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Acalabrutinib has demonstrated significant efficacy and safety in relapsed chronic lymphocytic leukemia (CLL). Efficacy and safety of acalabrutinib monotherapy were evaluated in a treatment-naive CLL cohort of a single-arm phase 1/2 trial (ACE-CL-001). Adults were eligible for enrollment if chemotherapy was declined or deemed inappropriate due to comorbidities (N = 99). Patients had a median age of 64 years and 47% had Rai stage III/IV disease. Acalabrutinib was administered orally 200 mg once daily, or 100 mg twice daily until progression or intolerance. A total of 99 patients were treated; 57 (62%) had unmutated immunoglobulin heavy-chain variable gene, and 12 (18%) had TP53 aberrations. After median follow-up of 53 months, 85 patients remain on treatment; 14 discontinued treatment, mostly because of adverse events (AEs) (n = 6) or disease progression (n = 3). Overall response rate was 97% (90% partial response; 7% complete response), with similar outcomes among all prognostic subgroups. Because of improved trough BTK occupancy with twice-daily dosing, all patients were transitioned to 100 mg twice daily. Median duration of response (DOR) was not reached; 48-month DOR rate was 97% (95% confidence interval, 90-99). Serious AEs were reported in 38 patients (38%). AEs required discontinuation in 6 patients (6%) because of second primary cancers (n = 4) and infection (n = 2). Grade ≥3 events of special interest included infection (15%), hypertension (11%), bleeding events (3%), and atrial fibrillation (2%). Durable efficacy and long-term safety of acalabrutinib in this trial support its use in clinical management of symptomatic, untreated patients with CLL.

Purpose Intolerance is the most common reason for kinase inhibitor (KI) discontinuation in CLL. Umbralisib a novel, highly selective PI3Kδ/CK1e inhibitor, is active and well tolerated in CLL patients. This phase 2 trial evaluated umbralisib in CLL patients who are intolerant to prior BTK or PI3K inhibitor therapy. Patients and methods In this phase 2 trial (NCT02742090), umbralisib was initiated at 800 mg oral daily in CLL patients requiring therapy per investigator discretion who were intolerant to prior BTK or PI3K inhibitor therapy, until progression or toxicity. Primary endpoint was progression-free survival (PFS). Secondary endpoints included time to treatment failure and umbralisib safety profile. DNA isolated from buccal swabs was genotyped for polymorphisms in CYP3A4, CYP3A5 and CYP2D6. Results Fifty-one patients were enrolled (44 BTKi and 7 PI3Kδi intolerant). Median age was 70 years (range 48-96), median of 2 prior lines of therapy (1-7), 24% had del17p and/or TP53 mutation, and 65% were IGHV unmutated. Most common AEs leading to prior KI discontinuation were rash (27%), arthralgia (18%), and atrial fibrillation (16%). Median progression free survival (PFS) was 23.5 months (95% CI 13.1-not estimable). 58% of patients were on umbralisib for a longer duration than prior KI. Most common (≥5%) grade ≥3 AEs on umbralisib (all causality) were neutropenia (18%), leukocytosis (14%), thrombocytopenia (12%), pneumonia (12%), and diarrhea (8%). Six patients (12%) discontinued umbralisib due to an AE. Eight patients (16%) had dose reductions and were successfully re-challenged. Conclusions Umbralisib is safe and effective in this BTK and alternate PI3K inhibitor intolerant CLL population. These are the first prospective data to confirm that switching from a BTK or alternate PI3K inhibitor to umbralisib can result in durable, well tolerated responses.

A diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) was elicited during acute COVID‐19 infection. COVID‐19 spike proteins trigger the alternative pathway of complement. Acute SARS‐CoV‐2 infection possibly expanded an existing PIG‐A mutation.

BACKGROUND: Treatment of chronic lymphocytic leukemia (CLL) with a fixed-duration venetoclax (Ven)-based regimen is now a standard of care (SOC) option for both frontline and relapsed refractory (R/R) disease based on results of the CLL14 and MURANO trials (Fischer et al NEJM 2019, Seymour et al NEJM 2018). As fixed-duration Ven regimens are now a SOC, it is expected that an increasing number of patients (pts) will ultimately progress after Ven exposure and require additional CLL-directed therapy. While many discuss re-treatment with Ven as a subsequent treatment option, the current literature contains response data on an extremely limited number of evaluable pts (11 pts MURANO, overall response rate (ORR) 55%; 3 pts VEN 365, ORR 100%). Whether re-treatment with Ven is an acceptable option remains an important unanswered clinical question. METHODS: We conducted a multicenter, retrospective study of CLL pts treated with a Ven-based regimen (Ven1) and then re-treated with a second Ven-based regimen (Ven2) in a later line of therapy (LOT). Data were collected from 13 centers and the CLL Collaborative Study of Real-World Evidence database. CLL pts were eligible for inclusion if they were treated with a Ven-based regimen in any LOT and then re-treated with a Ven-based regimen as a later LOT. Collected data included demographics, prognostic disease characteristics, tumor lysis syndrome (TLS) risk and incidence, clinical response and reasons for treatment discontinuation (dc). The primary study endpoint was investigator-assessed ORR (CR: complete response, PR: partial response, SD: stable disease, PD: progression of disease, iwCLL 2018). Kaplan-Meier method was used to estimate progression free survival (PFS). All other analyses were descriptive. RESULTS: We identified 25 pts who were re-treated with Ven. Pt characteristics prior to treatment with Ven1 are summarized in Table 1. In 24% of pts (n=6), Ven1 was administered as part of a clinical trial. Median prior LOT was 2 (range 0-10) with 12.0% treatment naïve and 60% with prior BTKi exposure. The majority of pts had ≥1 high-risk prognostic marker: del17p (39%), TP53 mut (27%), complex karyotype ≥5 abnormalities (30%) and unmutated IGHV (84%). For Ven1, treatment regimens, TLS risk, and dose are summarized in Table 2. With a median duration of exposure of 15 months (mos) (64% pts > 12 mos) for Ven1, the ORR was 88% (CR: 48%, PR: 40%, Figure 1A). Ten pts had minimal residual disease (MRD) assessments by flow cytometry; 8 pts (80%) achieved undetectable MRD (10^-4). Most common reasons for Ven1 dc included: toxicity (28%), completion of planned therapy (24%), MD/pt preference (24%), other (12%), alloHSCT (4%) and cost (4%). There was a median of 8.7 mos (36% > 12 mos) between Ven1 and the initiation of Ven2, and 88% did not receive another LOT between Ven1 and Ven2. Reasons for Ven2 initiation were either CLL progression (87.5%) or MRD-positive relapse (12.5%). For Ven2, TLS risk, TLS incidence and dose information are outlined in Table 2. TLS was a rare event during Ven re-treatment (4.5%, lab only). For Ven2, Ven monotherapy was the most common regimen (52%). Standard Ven dose-escalation was used for re-initiation in 17 of 19 pts with available data, however 1 pt started Ven2 at 400 mg daily (no TLS) and another underwent a prolonged ramp-up period. At the time of this analysis, 18 pts had available response assessments for Ven2: ORR is 72.2% (CR: 4, PR: 9, SD: 4 and PD: 1, Figure 1B). Median time from Ven2 to progression or last follow up is 8 mos (0.2-29 mos). Median PFS has not been reached. Estimated 12-month PFS is 69.1%. For pts with a CR to Ven2, median follow up time is 14.5 mos vs 7 mos for pts with PR or SD. Of 25 pts re-treated with Ven, 68% remain on Ven2 presently and 32% have discontinued Ven2, including due to CLL progression (n=4), completion of planned therapy (n=1), unrelated death (n=1), MD/pt preference (n=1). CONCLUSIONS: To our knowledge, this is the largest reported cohort of CLL pts re-treated with Ven after a prior Ven-based regimen. The high ORR in this pt population (median 2 prior therapies) suggests that re-treatment is a promising strategy and should be considered in treatment sequencing algorithms. Notably, pts with a CR to Ven2 had a longer median follow up than those with a PR or SD, suggesting a likelihood of deeper responses with time. Given the promising ORR, further research to prospectively validate Ven re-treatment is warranted. Updated data will be presented. Disclosures Allan: Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria; Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy. Sail:AbbVie Inc.: Current Employment, Current equity holder in publicly-traded company. Manzoor:Abbvie: Current Employment, Other: may hold stock or stock options. Pu:Takeda Pharmaceuticals: Consultancy. Barr:Gilead: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy, Research Funding; Abbvie/Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy; Morphosys: Consultancy; TG therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy. Coombs:LOXO Oncology: Honoraria; MEI Pharma: Honoraria; Abbvie: Consultancy, Honoraria; Genentech: Honoraria; AstraZeneca: Honoraria; Octapharma: Honoraria; Novartis: Honoraria. Schuster:AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria; Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding. Skarbnik:Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Consultancy; Beigene: Speakers Bureau; Verastem: Speakers Bureau; Novartis: Speakers Bureau; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CLL Society: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rhodes:Verastem: Consultancy; Abbvie/Genentech: Consultancy; Pharmacyclics: Consultancy; AstraZeneca: Consultancy. Barrientos:Janssen: Honoraria; Sandoz: Consultancy; Oncternal Therapeutics: Research Funding; Bayer: Consultancy; Genentech: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy. Roeker:American Society of Hematology: Research Funding; Abbott Laboratories: Other: spouse with minority ownership interest ; AbbVie: Other: spouse with minority ownership interest . Leslie:Celgene: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BeiGene: Honoraria, Speakers Bureau; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Honoraria, Speakers Bureau; Karyopharm: Honoraria, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Kamdar:Roche: Research Funding. Choi:Pharmacyclics/Abbvie: Research Funding; Genentech: Consultancy. Simkovic:Abbvie: Consultancy, Other: travel expenses. Lansigan:Seattle Genetics: Consultancy; BMS: Consultancy; BMS Steering Committee for MAGNIFY Program: Membership on an entity's Board of Directors or advisory committees; Spectrum Pharma: Consultancy, Research Funding. Zelenetz:Novartis: Consultancy; Gilead: Research Funding; Janssen: Consultancy; Celgene: Consultancy; Gilead: Consultancy; Genentech/Roche: Consultancy; Roche: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnology: Consultancy; MorphoSys: Research Funding; Amgen: Consultancy; Sandoz: Research Funding; Celgene: Research Funding; MEI Pharma: Research Funding. Moskowitz:Merck: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Miragen Therapeutics: Consultancy; Incyte: Research Funding; Merck: Consultancy; Imbrium Therapeutics, L.P.: Consultancy; Seattle Genetics: Consultancy. Goy:Morphosys: Research Funding; AbbVie: Research Funding; MD Anderson: Research Funding; Regional Cancer Care Associates/OMI: Current Employment; Infinity Verastem: Research Funding; Infinity: Research Funding; Karyopharm: Research Funding; Genentech/Roche: Research Funding; CALBG: Research Funding; Constellation: Research Funding; Bayer: Research Funding; PracticeUpdate Oncology: Consultancy; RCCA/OMI: Current Employment; Acerta: Consultancy, Honoraria, Other: leadership role, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: leadership role, Research Funding; Celgene: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: leadership role, Research Funding; COTA: Consultancy, Current equity holder in publicly-traded company, Other: leadership role; Kite, a Gilead Company: Consultancy, Current equity holder in publicly-traded company, Honoraria, Other: leadership role, Research Funding; Xcenda: Consultancy; Hackensack UMC and University of Nebraska: Research Funding. Feldman:Pfizer: Research Funding; Kyowa Kirin: Consultancy, Research Funding; Eisai: Research Funding; Cell Medica: Research Funding; Amgen: Research Funding; Pharmacyclics: Honoraria, Other, Speakers Bureau; Abbvie: Honoraria; Bayer: Consultancy, Honoraria; Trillium: Research Funding; Portola: Research Funding; Janssen: Speakers Bureau; AstraZeneca: Consultancy; Viracta: Research Funding; Rhizen: Research Funding; Corvus: Research Funding; BMS: Consultancy, Honoraria, Research Funding; Kite: Honoraria, Other: Travel expenses, Speakers Bureau; Celgene: Honoraria, Research Funding; Takeda: Honoraria, Other: Travel expenses; Seattle Genetics, Inc.: Consultancy, Honoraria, Other: Travel expenses, Research Funding, Speakers Bureau. Furman:Verastem: Consultancy; Genentech: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy, Research Funding; Acerta: Consultancy; Abbvie: Consultancy; TG Therapeutics: Consultancy, Research Funding; Sunesis: Consultancy; Pharmacyclics: Consultancy; Oncotarget: Consultancy; Loxo Oncology: Consultancy; Janssen: Consultancy, Speakers Bureau; Incyte: Consultancy. Mato:Genentech: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; BeiGene: Consultancy; LOXO: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Adaptive: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding.

Clonal expansion of B cell chronic lymphocytic leukemia (B-CLL) occurs within lymphoid tissue pseudofollicles. IL-15, a stromal cell–associated cytokine found within spleens and lymph nodes of B-CLL patients, significantly boosts in vitro cycling of blood-derived B-CLL cells following CpG DNA priming. Both IL-15 and CpG DNA are elevated in microbe-draining lymphatic tissues, and unraveling the basis for IL-15–driven B-CLL growth could illuminate new therapeutic targets. Using CpG DNA-primed human B-CLL clones and approaches involving both immunofluorescent staining and pharmacologic inhibitors, we show that both PI3K/AKT and JAK/STAT5 pathways are activated and functionally important for IL-15→CD122/ɣc signaling in ODN-primed cells expressing activated pSTAT3. Furthermore, STAT5 activity must be sustained for continued cycling of CFSE-labeled B-CLL cells. Quantitative RT-PCR experiments with inhibitors of PI3K and STAT5 show that both contribute to IL-15–driven upregulation of mRNA for cyclin D2 and suppression of mRNA for DNA damage response mediators ATM, 53BP1, and MDC1. Furthermore, protein levels of these DNA damage response molecules are reduced by IL-15, as indicated by Western blotting and immunofluorescent staining. Bioinformatics analysis of ENCODE chromatin immunoprecipitation sequencing data from cell lines provides insight into possible mechanisms for STAT5-mediated repression. Finally, pharmacologic inhibitors of JAKs and STAT5 significantly curtailed B-CLL cycling when added either early or late in a growth response. We discuss how the IL-15–induced changes in gene expression lead to rapid cycling and possibly enhanced mutagenesis. STAT5 inhibitors might be an effective modality for blocking B-CLL growth in patients.

Ibrutinib, a once-daily oral inhibitor of Bruton tyrosine kinase, has greatly improved outcomes for patients with chronic lymphocytic leukemia (CLL). The phase 3 RESONATE trial, which compared single-agent ibrutinib to ofatumumab in high-risk, relapsed patients with CLL, provided support for approval of ibrutinib in the United States and Europe. We describe long-term follow-up of patients treated in RESONATE, where continued superiority of progression-free survival (PFS) (hazard ratio [HR], 0.133; 95% confidence interval [CI], 0.099-0.178) was observed. Overall survival benefit continues (HR, 0.591; 95% CI, 0.378-0.926), although with decreased magnitude relative to that seen before crossover to ibrutinib was implemented for patients on ofatumumab (HR, 0.426; 95% CI, 0.220-0.823). Notably, overall response to ibrutinib increased over time, with 91% of patients attaining a response. The PFS benefit with ibrutinib was independent of baseline risk factors, although patients with ≥2 prior therapies had shorter PFS than those with

E1912 was a randomized phase 3 trial comparing indefinite ibrutinib plus 6 cycles of rituximab (IR) to 6 cycles of fludarabine, cyclophosphamide, and rituximab (FCR) in untreated younger patients with CLL. We describe measurable residual disease (MRD) levels in E1912 over time and correlate them with clinical outcome. Undetectable MRD rates (

Patient-derived xenograft models of chronic lymphocytic leukemia (CLL) can be created using highly immunodeficient animals, allowing analysis of primary tumor cells in an in vivo setting. However, unlike many other tumors, CLL B lymphocytes do not reproducibly grow in xenografts without manipulation, proliferating only when there is concomitant expansion of T cells. Here we show that in vitro pre-activation of CLL-derived T lymphocytes allows for a reliable and robust system for primary CLL cell growth within a fully autologous system that uses small numbers of cells and does not require pre-conditioning. In this system, growth of normal T and leukemic B cells follows four distinct temporal phases, each with characteristic blood and tissue findings. Phase 1 constitutes a period during which resting CLL B cells predominate, with cells aggregating at perivascular areas most often in the spleen. In Phase 2, T cells expand and provide T-cell help to promote B-cell division and expansion. Growth of CLL B and T cells persists in Phase 3, although some leukemic B cells undergo differentiation to more mature B-lineage cells (plasmablasts and plasma cells). By Phase 4, CLL B cells are for the most part lost with only T cells remaining. The required B-T cell interactions are not dependent on other human hematopoietic cells nor on murine macrophages or follicular dendritic cells, which appear to be relatively excluded from the perivascular lymphoid aggregates. Notably, the growth kinetics and degree of anatomic localization of CLL B and T cells is significantly influenced by intravenous versus intraperitoneal administration. Importantly, B cells delivered intraperitoneally either remain within the peritoneal cavity in a quiescent state, despite the presence of dividing T cells, or migrate to lymphoid tissues where they actively divide; this dichotomy mimics the human condition in that cells in primary lymphoid tissues and the blood are predominately resting, whereas those in secondary lymphoid tissues proliferate. Finally, the utility of this approach is illustrated by documenting the effects of a bispecific antibody reactive with B and T cells. Collectively, this model represents a powerful tool to evaluate CLL biology and novel therapeutics in vivo.

Ibrutinib positively modulates many T-cell subsets in chronic lymphocytic leukemia (CLL). To understand ibrutinib’s effects on the broader landscape of immune cell populations, we comprehensively characterized changes in circulating counts of 21 immune blood cell subsets throughout the first year of treatment in patients with relapsed/refractory (R/R) CLL (n = 55, RESONATE) and previously untreated CLL (n = 50, RESONATE-2) compared with untreated age-matched healthy donors (n = 20). Ibrutinib normalized abnormal immune cell counts to levels similar to those of age-matched healthy donors. Ibrutinib significantly decreased pathologically high circulating B cells, regulatory T cells, effector/memory CD4+ and CD8+ T cells (including exhausted and chronically activated T cells), natural killer (NK) T cells, and myeloid-derived suppressor cells; preserved naive T cells and NK cells; and increased circulating classical monocytes. T-cell function was assessed in response to T-cell receptor stimulation in patients with R/R CLL (n = 21) compared with age-matched healthy donors (n = 18). Ibrutinib significantly restored T-cell proliferative ability, degranulation, and cytokine secretion. Over the same period, ofatumumab or chlorambucil did not confer the same spectrum of normalization as ibrutinib in multiple immune subsets. These results establish that ibrutinib has a significant and likely positive impact on circulating malignant and nonmalignant immune cells and restores healthy T-cell function.

Therapeutic targeting of Bruton tyrosine kinase (BTK) has dramatically improved survival outcomes for patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Acalabrutinib is an oral, highly selective BTK inhibitor that allows for twice-daily dosing due to its selectivity. In this phase 1b/2 study, 134 patients with relapsed/refractory CLL or SLL (median age, 66 years [range, 42-85 years]; median prior therapies, 2 [range, 1-13]) received acalabrutinib 100 mg twice daily for a median of 41 months (range, 0.2-58 months). Median trough BTK occupancy at steady state was 97%. Most adverse events (AEs) were mild or moderate, and were most commonly diarrhea (52%) and headache (51%). Grade ≥3 AEs (occurring in ≥5% of patients) were neutropenia (14%), pneumonia (11%), hypertension (7%), anemia (7%), and diarrhea (5%). Atrial fibrillation and major bleeding AEs (all grades) occurred in 7% and 5% of patients, respectively. Most patients (56%) remain on treatment; the primary reasons for discontinuation were progressive disease (21%) and AEs (11%). The overall response rate, including partial response with lymphocytosis, with acalabrutinib was 94%; responses were similar regardless of genomic features (presence of del(11)(q22.3), del(17)(p13.1), complex karyotype, or immunoglobulin variable region heavy chain mutation status). Median duration of response and progression-free survival (PFS) have not been reached; the estimated 45-month PFS was 62% (95% confidence interval, 51% to 71%). BTK mutation was detected in 6 of 9 patients (67%) at relapse. This updated and expanded study confirms the efficacy, durability of response, and long-term safety of acalabrutinib, justifying its further investigation in previously untreated and treated patients with CLL/SLL. This trial was registered at www.clinicaltrials.gov as #NCT02029443.

Background: The ECOG-ACRIN randomized phase 3 clinical trial E1912 established ibrutinib-rituximab (IR) as the standard of care for CLL patients Methods: Patients enrolled on E1912 completed the Functional Assessment of Cancer Therapy-General (FACT-G) and Leukemia subscale at randomization (baseline), 3, 6, and 12 months post-randomization, and every 6 months for 2 years regardless of disease status. The primary outcome was the 31-item FACT-Leukemia Trial Outcome Index (FACT-Leu TOI), calculated by summing items from the FACT-G physical wellbeing (PWB), functional well-being (FWB), and leukemia subscales (score range: 0-124). The primary endpoint was defined as the difference in FACT-Leu TOI change scores from randomization to 12 months (at response evaluation) between patients treated with continuous therapy Arm A (IR) vs time-limited therapy Arm B (FCR). Mean change scores from baseline to each time point were calculated using all cases with data at baseline and the corresponding time point. Comparisons between treatment arms were performed using two-sample t tests. Linear mixed effects models were used to estimate the trajectories of PRO scores. Results: PRO data was extracted on 3/8/2021. PRO data was provided at baseline and 12 months for 233/354 (65.8%) patients on the IR arm and 118/175 (67.4%) patients on the FCR arm. At enrollment, there were no significant differences in the baseline FACT-Leu TOI scores (mean ± SE) between the two arms: IR (93.27 ± 1.03) vs FCR (92.68 ± 1.38; p=0.73). The FACT-Leu TOI score improved from baseline to 12 months in both arms (Table 1 and Figure 1). The change scores from baseline to 12 months, the primary outcome, were not significantly different between IR (7.59 ± 1.09) vs FCR (8.22 ± 1.44; p=0.73). Change in FACT-Leu TOI from baseline to 3 months was 5.77 ± 0.77 and 4.06 ± 1.18 (p=0.22); and from baseline to 6 months was 6.87 ± 0.87 and 8.01 ± 1.44 (p=0.50) in the IR and FCR arms, respectively. After the first 6 months of treatment, the improvement in FACT-Leu TOI scores was maintained in both treatment arms. There was no significant difference in total FACT-Leu TOI score in the continuous therapy (IR) vs time-limited therapy (FCR) arms over the first 36 months post registration. Analysis of FACT subscales showed PWB improved in the IR arm (0.37 ± 0.22) and declined in the FCR arm (-0.92 ± 0.39) from baseline to 3 months (p=0.004 for difference in PWB change between arms) but there was no significant difference between the two arms for change in PWB scores from baseline to 6 and 12 months. There were no significant differences between the two arms for change in FWB and FACT-Leu subscales from baseline to 3, 6 and 12 months. Conclusions: QOL improves in CLL patients age 70 and younger when treated in the frontline setting with IR or FCR. The improvement in QOL is maintained during continuous therapy with ibrutinib and there is no significant decline in QOL over time. Given the improvement in PFS and OS with IR over FCR seen in E1912, the results of this QOL analysis support the use of frontline ibrutinib in previously untreated younger CLL patients. Acknowledgement: This study was conducted by the ECOG-ACRIN Cancer Research Group (Peter J. O'Dwyer, MD and Mitchell D. Schnall, MD, PhD, Group Co-Chairs) and supported by the National Cancer Institute of the National Institutes of Health under award numbers: U10CA180794, U10CA180820, UG1CA189863, UG1CA190140, UG1CA232760, UG1CA233180, UG1CA233230, UG1CA233253, UG1CA233277, UG1CA233290, UG1CA233339, UG1CA189859, UG1CA233332. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Figure 1 Figure 1. Disclosures Kay: Oncotracker: Membership on an entity's Board of Directors or advisory committees; CytomX Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Research Funding; Acerta Pharma: Research Funding; Behring: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Targeted Oncology: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Research Funding; Sunesis: Research Funding; Genentech: Research Funding; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding. O'Brien: Amgen, Astellas, Celgene, GlaxoSmithKline, Janssen Oncology, Aptose Biosciences Inc., Vaniam Group LLC, AbbVie, Alexion, Verastem, Juno Therapeutics, Vida Ventures, Autolus, Johnson and Johnson, Merck, Bristol Myers Squibb, NOVA Research Company, Eli Lill: Consultancy; Kite, Regeneron, Acerta, Caribou, Gilead, Pharmacyclics, TG Therapeutics, Pfizer, Sunesis: Research Funding. Coutre: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Data Safety Monitoring Committee, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta: Other: Data Safety Monitoring Committee, Research Funding. Barr: AstraZeneca: Consultancy; Gilead: Consultancy; Janssen: Consultancy; Genentech: Consultancy; Beigene: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy; TG Therapeutics: Consultancy; Morphosys: Consultancy; Abbvie/Pharmacyclics: Consultancy. Cashen: Secura Bio, ADC Therapeutics: Consultancy. Mato: Adaptive Biotechnologies: Consultancy, Research Funding; DTRM BioPharma: Consultancy, Research Funding; Johnson and Johnson: Consultancy, Research Funding; Acerta/AstraZeneca: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; AstraZeneca: Consultancy; BeiGene: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; LOXO: Consultancy, Research Funding; MSKCC: Current Employment; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Nurix: Research Funding; Janssen: Consultancy, Research Funding; Genmab: Research Funding. Erba: AbbVie Inc; Agios Pharmaceuticals Inc; Astellas; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Daiichi Sankyo Inc; Genentech, a member of the Roche Group; GlycoMimetics Inc; Incyte Corporation; Jazz Pharmaceuticals Inc; Kura Oncology; Nov: Other: Advisory Committee; AbbVie Inc: Other: Independent review committee; AbbVie Inc; Agios Pharmaceuticals Inc; ALX Oncology; Amgen Inc; Daiichi Sankyo Inc; FORMA Therapeutics; Forty Seven Inc; Gilead Sciences Inc; GlycoMimetics Inc; ImmunoGen Inc; Jazz Pharmaceuticals Inc; MacroGenics Inc; Novartis; PTC Therapeutics: Research Funding; AbbVie Inc; Agios Pharmaceuticals Inc; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Incyte Corporation; Jazz Pharmaceuticals Inc; Novartis: Speakers Bureau. Stone: Onconova: Consultancy; AbbVie: Consultancy; Boston Pharmaceuticals: Consultancy; Bristol Myers Squibb: Consultancy; Gemoab: Membership on an entity's Board of Directors or advisory committees; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; Jazz: Consultancy; Syros: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Research Funding; Takeda: Consultancy; BerGen Bio: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Foghorn Therapeutics: Consultancy; Innate: Consultancy; Janssen: Consultancy; GlaxoSmithKline: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy, Research Funding; Actinium: Membership on an entity's Board of Directors or advisory committees; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; Aprea: Consultancy; Celgene: Consultancy; Macrogenics: Consultancy. Litzow: Actinium: Research Funding; Amgen: Research Funding; AbbVie: Research Funding; Pluristem: Research Funding; Jazz: Other: Advisory Board; Omeros: Other: Advisory Board; Astellas: Research Funding; Biosight: Other: Data monitoring committee. Tallman: NYU Grand Rounds: Honoraria; Kura: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Biosight: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Orsenix: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Rafael Pharmaceuticals: Research Funding; Glycomimetics: Research Funding; Biosight: Research Funding; Orsenix: Research Funding; Abbvie: Research Funding; Mayo Clinic: Honoraria; UC DAVIS: Honoraria; Northwell Grand Rounds: Honoraria; NYU Grand Rounds: Honoraria; Danbury Hospital Tumor Board: Honoraria; Acute Leukemia Forum: Honoraria; Miami Leukemia Symposium: Honoraria; New Orleans Cancer Symposium: Honoraria; ASH: Honoraria; NCCN: Honoraria. Shanafelt: Genentech, Pharmacyclics: Research Funding. Wagner: Eli Lilly, Johnson & Johnson: Other: Spouse, previously held individual stocks;; Celgene-BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Athenex Inc: Consultancy.

Background: The development of Richter Transformation (RT) in patients (pts) with chronic lymphocytic leukemia (CLL) while on targeted agents has been reported to have a median survival of 2.3-3.5 months (mo). Treatment is usually anthracycline-based combination regimens, though responses are short-lived. Phase 2 trial of combined venetoclax-REPOCH achieved a median progression free survival (PFS) of 16 mo. We studied the use of ibrutinib in combination with obinutuzumab, cyclophosphamide, doxorubicin, vincristine, and prednisone (I-OCHOP) JUN2017-SEP2018 (ClinicalTrials.gov: NCT03145480). During the conduct of the study, ibrutinib plus RCHOP in untreated diffuse large B cell lymphoma (NCT01855750) reported more treatment-emergent serious adverse events when compared to RCHOP, leading to higher rates of treatment discontinuation with toxicity more prominent in elderly pts. Since the majority of pts with CLL are elderly, enrollment was stopped. We report the outcomes of 3 participants. Methods: Informed consent was provided through IRB-approved protocol. Subjects were enrolled in an open-label phase II trial combining ibrutinib with O-CHOP. Ibrutinib 560mg was taken daily starting cycle 1 day 1 (C1D1) continuously until progression or start of new anticancer treatment. Obinutuzumab was given per prescription insert starting on C1D1 with CHOP for up to 6 cycles. Pts were allowed to discontinue study drugs to pursue allogeneic stem cell transplant (allo-SCT). Pts aged 18-80 years old with adequate organ function, Eastern Cooperative Oncology Group performance status ≤ 2, and histologically confirmed evidence of RT from CLL were eligible to participate. Prior targeted agent use was allowed until 24 hours prior to dosing. Chemo- or immuno-therapy was not allowed within 21 and 10 days of C1D1 respectively. The primary endpoint was investigator-assessed overall response rate (ORR) per revised response criteria for malignant lymphoma. Secondary outcomes included hematological improvement, PFS, overall survival (OS), and quality of life. Pts were allowed to pursue allo-SCT after achieving a response and were followed for PFS/OS. Descriptive analyses were utilized, and PFS/OS was calculated from initial treatment to death or last follow-up. Results: Three pts consented and started therapy: two women and one man with a median [range] age of 53 [36-73] years, all had high-risk disease (Figure 1). Median Cumulative Illness Rating Scale at baseline 2 [0-4]. No large cell lymphoma involved the bone marrow. All pts developed RT while on a novel agent (ibrutinib, acalabrutinib, or venetoclax monotherapy respectively). All enrolled immediately after RT diagnosis and received I-OCHOP. Participants had overall good adherence to ibrutinib therapy (mean missed doses per 28-day treatment cycle was 0.88 doses) while on trial. Two pts developed neutropenia (n=1, grade 3 and n=1, grade 4; neither febrile) that resolved by time of withdrawal from study. 2 pts had anemia (grade 1 and 2), and one participant had thrombocytopenia (grade 2), neither requiring transfusion support. All 3 pts reported fatigue (all grade 2 or less) that on average improved during treatment as assessed by FACIT questionnaire (mean Δ from baseline to end of treatment: -5). Figure 1 lists other adverse events. Of 3 enrolled pts, 2 pts achieved remission (1 complete, 1 partial) and undetectable minimal residual disease (detection sensitivity 0.01%) in the bone marrow post 4 cycles I-OCHOP and underwent allo-SCT and were followed for progression. Figures 2 and 3 show the PET responses after 2 cycles of I-OCHOP in 2 participants with bulky lymphadenopathy. Time to allo-SCT for the 2 pts was 3.7 and 3.9 mo from C1D1. After transplant, one pt relapsed with RT in the central nervous system after 20 mo and died from pneumonia 5 mo later; the other pt is alive 49.5 mo later with no evidence of disease. The third pt had rapid progression and came off study. Median PFS for the 3 pts was 23.5 mo [1.9-NR] and OS 29.1 mo [6.7-NR] as of datacut July 30, 2021. Conclusions: Despite historically poor outcomes reported after RT while on a targeted agent, ibrutinib addition to anthracycline-based regimen seemed well tolerated. Two patients achieved a rapid and deep responses irrespective of prior BTK inhibitor use and were able to pursue allo-SCT which correlated with durable PFS/OS. Figure 1 Figure 1. Disclosures Rhodes: Conquer Cancer Foundation Young Investigator Award: Other: Grant/Research Support; AbbVie, Genentech, Pharmacyclics, TG Therapeutics: Other: Consultant.

Background: Cirmtuzumab (Cirm) is a humanized monoclonal antibody that inhibits the tumor promoting activity of ROR1 and has demonstrated additive/synergistic activity with many anticancer agents, including ibrutinib (Ibr). Methods: Patients (Pts) with relapsed or refractory (RR) MCL or treatment-naïve (TN) or RR CLL were enrolled. In Part 1 (Dose Escalation), doses of Cirm IV q2wks x5 then q4wks of 2-16 mg/kg and 300 or 600 mg were examined. Safety of Cirm alone was assessed during the first 28 days, then Ibr was started at approved doses for each indication. Cirm 600 mg IV q2wks x3 then q4wks in combination with Ibr starting day 0 was chosen as the recommended dosing regimen for use in Part 2 (Expansion) and Part 3 (CLL only, Cirm/Ibr vs. Ibr). MCL Part 1 is closed, and Part 2 is open for enrollment. CLL Parts 1, 2 & 3 are closed for enrollment. Results: As of 18Jun2021 data cutoff, 28, 34 and 28 pts were treated in MCL Parts 1 & 2, CLL Parts 1 & 2, and CLL Part 3 (Cirm/Ibr (n=18) or Ibr (n=10)). In Parts 1 & 2 MCL, the median number (#) of prior systemic regimens was 1.5 (1-4) including pts relapsing after Ibr (n=4), auto-SCT (n=6), auto-SCT/allo-SCT (n=1), or auto-SCT/CAR-T (n=1). Ki-67 ≥30% and extra-nodal disease was present in 54% and 68% of pts, respectively. The median # of prior systemic regimens for CLL Parts 1 & 2 and CLL Part 3 (RR), was 2 (1-15) including auto-SCT (n=1), and 2 (1-6). Pts entered with Rai staging ≥ Grade 2 in 71% and 64%. Safety (MCL and CLL): Most frequent treatment emergent (TEAEs) (≥30%) for both MCL and CLL pts treated with Cirm/Ibr (N=80), (all grades; regardless of causality) included contusion & fatigue (both 40.0%), and diarrhea (37.5%). Most frequent (≥5%) Grade ≥3 TEAEs, regardless of causality included hypertension (10.0%), fatigue, neutropenia, pneumonia, and atrial fibrillation (all 6.3%), leukocytosis and anemia (both 5.0%). Grade ≥3 TEAEs of myelosuppression, regardless of causality, include anemia (5.0%), thrombocytopenia (1.3%), and neutropenia (6.3%). Most TEAEs in MCL or CLL pts were considered related by Investigator to Ibr alone 64% or 84% vs. Cirm alone 14.3% or 16%. Efficacy (MCL): The best response of 20 evaluable pts in Parts 1 & 2 included CR 35%, PR 45%, SD 10%, and 10% PD. At a median follow-up of 14.9 mos., the objective response rate (ORR), clinical benefit rate (CBR) and median duration of response (DOR) for overall, ≥30% Ki-67, and >1 prior systemic regimen subgroups, were 80%, 90% and (not reached) NR (95% CI: 11.9, NR), 81.8%, 81.8% and 13.8 (95% CI: 8.7, NR), and 90%, 100% and NR (95% CI: 8.7, NR). Responses occurred in all evaluable pts who received prior SCT+/- CAR-T (4CR, 2PR) or prior Ibr (2CR, 2PR). The median PFS (mPFS) for overall, pts achieving CR, and >1 prior systemic regimen subgroups were all NR with varying 95% CI: (16.5, NR), (0.03, NR), and (0.03, NR). Efficacy (CLL): The best response of 34 evaluable pts in Parts 1 & 2 included 94.1% ORR, 11.8% CR, 82.3% PR/PR-L, and 5.9% SD for a CBR of 100%. In Part 3, evaluable Cirm/Ibr TN (n=8) or RR (n=7) and Ibr TN (n=4) or RR (n=3) arms achieved 100% or 85.7% and 100% or 100% ORR, 12.5% or 0% and 0% or 0% CR, 87.5% or 85.7% and 100% or 100% PR/PR-L, 0% or 14.3% and 0% or 0% SD. No pts had PD as best response. All pts had a CBR of 100%. For Parts 1 & 2, at a median follow-up of 24.8 mos., the DOR for overall and >1 prior systemic regimen subgroups, was NR (8.3, 35.9) and NR (12.0, 29.6). In Part 3, at a median follow-up of 14.7 mos., the DOR for TN or RR Cirm/Ibr and Ibr arms is NR (7.7, 18.6) or NR (9.2, 14.8) and NR (11.2, 18.5) or NR (8.3, 14.2). The mPFS (Parts 1 & 2) for overall, pts achieving CR, and >1 prior systemic regimen subgroups were NR (9.1, 35.8), NR (95% CI: 22.5, NR), and NR (9.1, 35.2). In Part 3, mPFS for TN or RR Cirm/Ibr and Ibr arms is all NR. Conclusions: Cirm/Ibr is well-tolerated. ORR, CR, DOR, and mPFS were similar across all subgroups of MCL and CLL pts regardless of number of prior systemic regimens or poor risk factors. Striking responses were observed in patients with MCL as evidenced by a mPFS that was NR (95% CI: 16.5, NR), CR of 35%, and a DOR of NR (95% CI: 11.9, NR) within the study period. These data compare very favorably to the mPFS of 12.8 mos, CR of 20%, and a DOR of 18.6 mos., reported for Ibr alone (Rule 2017). For CLL pts treated with Cirm/Ibr, results continue to be encouraging as they mature. The study is ongoing, with MCL enrollment expanded to include Cirm + Ibr in pts who have had an inadequate response to an Ibr regimen, or who are refractory to approved BTKi agents. Figure 1 Figure 1. Disclosures Lee: Oncternal: Research Funding; Takeda: Research Funding; Celgene: Research Funding; Seagen: Research Funding; BMS: Honoraria, Research Funding; Aptitude Health: Honoraria; Guidepoint: Honoraria; Century Therapeutics: Consultancy; Pharmacyclics: Research Funding; Janssen: Honoraria. Choi: Abbvie: Other: Institution: Research Grant/Funding; Pharmacyclics: Other: Institution: Research Grant/Funding; Oncternal: Other: Institution: Research Grant/Funding; Velosbio: Other: Institution: Research Grant/Funding; Merck: Other: Institution: Research Grant/Funding; Geron: Other: Institution: Research Grant/Funding. Siddiqi: Celgene: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kite Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Speakers Bureau; Oncternal: Research Funding; TG Therapeutics: Research Funding. Wierda: Acerta Pharma Inc.: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; AstraZeneca: Research Funding; Cyclacel: Research Funding; Karyopharm: Research Funding; Xencor: Research Funding; Oncternal Therapeutics, Inc.: Research Funding; KITE Pharma: Research Funding; Miragen: Research Funding; Janssen: Research Funding; Gilead Sciences: Research Funding; Juno Therapeutics: Research Funding; Genentech: Research Funding; GSK/Novartis: Research Funding; Sunesis: Research Funding; Loxo Oncology, Inc.: Research Funding; Genzyme Corporation: Consultancy; AbbVie: Research Funding. Tuscano: BMS: Research Funding; Seattle Genetics: Research Funding; Takeda: Research Funding; Acrotech: Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Abbvie: Research Funding. Leslie: Abbvie: Consultancy, Honoraria; PCYC/Janssen: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Speakers Bureau; Karyopharm Therapeutics: Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; BeiGene: Consultancy, Honoraria, Speakers Bureau; ADC Therapeutics: Consultancy; Celgene/BMS: Consultancy, Honoraria, Speakers Bureau; TG Therapeutics: Consultancy, Honoraria, Speakers Bureau; Kite, a Gilead Company: Consultancy, Honoraria, Speakers Bureau; Epizyme: Consultancy, Honoraria, Speakers Bureau; Seagen: Consultancy, Honoraria, Speakers Bureau; Merck: Consultancy. Breitmeyer: Oncternal Therapeutics: Current Employment, Membership on an entity's Board of Directors or advisory committees. Yazji: Oncternal Therapeutics: Current Employment. Wang: Oncternal Therapeutics: Current Employment. Wang: OMI: Honoraria; Moffit Cancer Center: Honoraria; Chinese Medical Association: Honoraria; Newbridge Pharmaceuticals: Honoraria; DTRM Biopharma (Cayman) Limited: Consultancy; InnoCare: Consultancy, Research Funding; Scripps: Honoraria; Mumbai Hematology Group: Honoraria; VelosBio: Consultancy, Research Funding; BioInvent: Research Funding; Hebei Cancer Prevention Federation: Honoraria; Epizyme: Consultancy, Honoraria; Anticancer Association: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Lilly: Research Funding; Physicians Education Resources (PER): Honoraria; Dava Oncology: Honoraria; Clinical Care Options: Honoraria; Molecular Templates: Research Funding; BeiGene: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding; Pharmacyclics: Consultancy, Research Funding; Acerta Pharma: Consultancy, Honoraria, Research Funding; Imedex: Honoraria; Juno: Consultancy, Research Funding; Celgene: Research Funding; Genentech: Consultancy; Loxo Oncology: Consultancy, Research Funding; Kite Pharma: Consultancy, Honoraria, Research Funding; Miltenyi Biomedicine GmbH: Consultancy, Honoraria; The First Afflicted Hospital of Zhejiang University: Honoraria; Bayer Healthcare: Consultancy; BGICS: Honoraria; CAHON: Honoraria; Oncternal: Consultancy, Research Funding; CStone: Consultancy. Jamieson: Forty Seven Inc.: Patents & Royalties. Kipps: Genentech-Roche: Consultancy; Gilead Sciences: Consultancy, Honoraria, Other, Speakers Bureau; Janssen: Consultancy, Honoraria, Other, Research Funding, Speakers Bureau; Roche: Honoraria, Other; MD Anderson Cancer Center: Research Funding; Velos: Research Funding; CRIM: Research Funding; Indy Hematology Review: Other; TG Therapeutics: Other; Verstem: Other, Speakers Bureau; University of California, San Diego: Current Employment; Pharmacyclics/AbbVie: Honoraria, Research Funding; Breast Cancer Research Foundation: Research Funding; SCOR - The Leukemia and Lymphoma Society: Research Funding; National Cancer Institute/NIH: Honoraria, Research Funding; Genentech/Roche: Honoraria; European Research Initiative on CLL (ERIC): Honoraria; Genetech: Honoraria, Other; Celgene: Consultancy, Honoraria, Other, Research Funding; Bionest Partner: Other; DAVA Pharmaceuticals: Speakers Bureau; DAVAOncology: Consultancy, Honoraria, Other; AbbVie: Consultancy, Honoraria, Other, Speakers Bureau; Oncternal Therapeutics, Inc.: Current holder of stock options in a privately-held company, Other: Stock or other ownership, Patents & Royalties: Cirmtuzumab was developed by Thomas J. Kipps in the Thomas J. Kipps laboratory and licensed by the University of California to Oncternal Therapeutics, Inc., which provided stock options and research funding to the Thomas J. Kipps laboratory., Research Funding; Moores Cancer Center: Current Employment; MedImmune Inc: Research Funding; GlaxoSmithKline: Research Funding; Gilead Sciences, Inc.: Honoraria, Research Funding; Genentech, Inc.: Honoraria, Research Funding, Speakers Bureau; Pharmacyclics LLC, an Abbvie Company: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Celgene Corporation: Consultancy, Honoraria, Research Funding; Abbott Laboratories: Consultancy, Research Funding.

Richter's transformation (RT) is a complication of chronic lymphocytic leukemia (CLL) characterized by the development of an aggressive lymphoma, typically diffuse large B cell lymphoma (DLBCL). RT is associated with high expression of activation-induced cytidine deaminase (AID) and aberrant somatic hypermutation of non-immunoglobulin genes. Current frontline therapy of CLL, ibrutinib, eliminates AID + CLL cells and alters tissue microenvironment to Th1-biased niches; however approximately 10-20% of CLL patients develop RT upon ibrutinib treatment. In addition, ibrutinib leads to a clinical response in only ~40% of RT patients. Thus, RT remains an important unmet challenge for CLL patients and the mechanism of RT development during ibrutinib treatment is poorly understood. To determine the contributions of AID and T cells in RT development, and to understand the efficacy of ibrutinib in the treatment of RT, we first created patient-derived xenografts (PDXs) with samples from three RT patients who were refractory to (immuno)chemotherapy but had not previously received ibrutinib. In each case, the B-lymphocytes were larger in size and expressed lower levels of CD5 but higher levels of activation markers compared with the CLL cell counterpart. In PDXs, ibrutinib treatment led to significantly less RT cells in spleen with percentage of inhibition ranging from 28-60% for all three cases. Notably, AID levels were similar in RT cells residing in spleen of ibrutinib-treated and control mice. The numbers of T cells were also similar, although Th1:Th2 ratios were significantly increased by ibrutinib (control vs ibrutinib group: 33% vs 42%, P=0.01). Interestingly, the growth and survival of RT cells located in bone marrow (BM) were not affected by ibrutinib. We then investigated the efficacy of ibrutinib in the prevention and treatment of RT in a novel strain of TCL-1 mice, TCL1/Igκ-AID mice, that have AID overexpressed solely in B lymphocytes. These mice develop accelerated CLL disease, have shorter overall survival (OS), and bear increased numbers of AID signature mutations in genes that are drivers in CLL and DLBCL. First we injected primary splenocytes from a TCL1/Igκ-AID mouse (A-31) into wild-type C57BL/6 mice. A week later, mice were treated with vehicle or ibrutinib continuously for 3 weeks (N=5 per group, duplicated experiments). At the end of treatment, RT cells were found in 25% of recipients in the control group and only in 10% of ibrutinib-treated recipients. Ibrutinib-treated animals had overall smaller spleens and lymph nodes (LNs) filled with significantly less CLL or RT cells. Importantly, the balance of Th1/Th2 cytokines was also significantly changed by ibrutinib (Th1/Th2 in control vs ibrutinib: 25% vs 47%, P=0.01). However, again RT cells in BMs of treated and control animals were similar. We then repeated the experiment to determine overall survival by giving the mice vehicle or ibrutinib continuously. Compared to the TCL1/Igκ-AID (A-31) donors, recipients treated with control vehicle developed more aggressive CLL with shorter OS. However, Ibrutinib did not change the OS; both control and ibrutinib treated recipients had similar OS with all the mice developed and died from RT eventually. Finally, to determine the efficacy of ibrutinib in the treatment of RT in TCL1/Igκ-AID mice, we sorted A-31-derived RT cells collected from LNs, and injected these into C57BL/6 mice. Mice then received treatment for 3 weeks. Notably, ibrutinib did not change the numbers or sizes of LNs or spleens. The numbers of RT cells at all sites, including BM, remained the same. In both groups, the number of T cells and the Th1:Th2 were not altered by ibrutinib. In summary, our data suggest that ibrutinib is somewhat effective against primary RT cells in the spleen in PDX models but not at all in the aggressive TCL1/IgK-AID mouse model. This might be because ibrutinib does not reduce AID levels in tissue-resident RT cells. Notably, although RT cells in spleens and LNs respond to ibrutinib, those residing in BM are resistant in both PDX and TCL1/IgK-AID models. This suggests different clones or different ibrutinib-responsiveness of RT cells in primary versus secondary lymphoid tissues. Overall, these results suggest that ibrutinib does not prevent or cure RT. Additionally, TCL1/Igκ-AID mice might provide a model to study the development, prevention, and treatment of RT without the influence of prior chemo- or other therapies. Disclosures Wirtz: Abbvie: Current Employment. Szafer-Glusman: AbbVie: Current Employment, Other: Stock or other ownership.

Background. CLL-like monoclonal B-ceII lymphocytosis (MBL) is considered a requisite precursor of CLL, with 1-2% of subjects annually progressing to CLL requiring therapy. The role of immune alterations leading to and operating in MBL and controlling progression to CLL is not well characterized. Since an increased frequency of immune-related conditions associated with immune dysfunction exists prior to CLL diagnosis (Landgren et al, Br J Haematol 2007 and Blood 2007; Andersen et al, Leukemia 2020), immune alterations likely exist in MBL. We have examined the serum protein profiles of MBL and CLL in search of clues linking immune dysfunction with malignant transformation. Objectives. 1. Characterize the serum proteomic profiles of MBL individuals, IGHV-mutated CLL (M-CLL) and IGHV-unmutated CLL (U-CLL) patients, and age-matched healthy controls (HC). 2. Compare the serum proteomic profiles between the groups. 3. Assess the effect of IGHV mutation status on serum proteomic profiles in CLL. Methods. A total of 12 MBL, 12 M-CLL, 12 U-CLL and 12 age-matched HC were studied. Patients were cared for at Northwell Health, New York (n=25) and Hospital del Mar, Barcelona (n=11). All patients were treatment naive except for one U-CLL patient who was treated one year beforehand. Serum samples were collected, and their protein levels measured employing SOMAmers (modified single-stranded DNA aptamers; SomaLogic) to quantify relative levels of 1,310 proteins. P-values Results. Overall, the levels of 862 proteins differed significantly between groups: MBL vs. HC: 10 downregulated (d) and 24 upregulated (u); M-CLL vs. HC: 206d and 6u; U-CLL vs. HC: 54d and 40u; M-CLL vs. MBL: 384d and 5u; U-CLL vs. MBL: 74d and 24u; and M-CLL vs. U-CLL: 35d and 0u. IPA highlighted a role for the pro-inflammatory HMGB1 pathway in several comparisons. First, an activated HMGB1 pathway was predicted in MBL compared to HC, together with activation of phagocytes, and an inhibition of the systemic immune suppressor TGF-β. Second and consistent with the former, U-CLL patients displayed an activated HMGB1 pathway compared to HC, along with other signs of immune stimulation (activated NFkB and Th1 pathways, maturation of dendritic cells, and inhibition of TGF-β) and leukemic progression (activated progression of tumor, and leukocyte extravasation). Third and contrary to the above, the HMGB1 pathway was inhibited when comparing M-CLL to HC, in line with a global immune suppression signature (inhibited PRR, GM-CSF, FcεRI, IL1, IL8, TNF, Th1, STAT3 and NFkB pathways, in addition to inhibited cell movement, viability and activation). Notably, inhibition of immune pathways was predicted for both M-CLL and U-CLL compared to MBL (diminished TNF and IL6 signaling, and reduced cell movement), although the greatest differences were seen for M-CLL vs. MBL comparison, including blockade of the HMGB1 pathway in M-CLL. Finally, the M-CLL vs. U-CLL comparison suggested inhibited INFγ, IL2, IL3, IL4, NFkB, and decreased T lymphocyte stimulation and movement of tumor cells in M-CLL patients. Conclusions. An increased pro-inflammatory signature with involvement of the HMGB1 pathway was identified in MBL and U-CLL compared with HC, whereas the opposite was seen for M-CLL. Since MBL most often exhibit mutated IGHV (91% of cases in our cohort), these findings suggest immune stimulation as a characteristic feature in the pre-leukemic and U-CLL leukemic stage that surprisingly is not operative in M-CLL. Consistent with this, M-CLL displayed a global immune suppression (HMGB1 pathway inhibition), whereas U-CLL exhibited signs of immune stimulation (HMGB1 pathway activation) compared to HC which may relate to distinct capabilities of the two subtypes to interact with the microenvironment. Lastly, the increased inflammatory signature identified in MBL, which are mainly IGHV-mutated, was lessened in CLL, mainly in M-CLL patients. This is consistent with a decreased influence of immune imbalance and the HMGB1 pathway associated with IGHV-mutated clonal expansions. Acknowledgments. GB is supported by a grant from Fundación Alfonso Martín Escudero. Disclosures Allen: Alexon: Research Funding; Bristol Myers Squibb: Other: Equity Ownership; C4 Therapeutics: Other: Equity Ownership; Sanofi Genzyme: Membership on an entity's Board of Directors or advisory committees. Rhodes: Conquer Cancer Foundation Young Investigator Award: Other: Grant/Research Support; AbbVie, Genentech, Pharmacyclics, TG Therapeutics: Other: Consultant.

Background: Follicular lymphoma (FL) is the second most common subtype of non-Hodgkin lymphoma (NHL) accounting for ~35% of NHL and often have a clinically indolent course. PET/CT max SUV ≥10 and high proliferative index are associated with FL at high risk for transformation to aggressive lymphoma (Schöder, 2005; Rossi, 2020). A subset of patients (pts) with low histologic grade and high proliferation index (LG-HPI) have a more aggressive clinical course with inferior overall survival (OS) compared to low grade, low proliferation index (LG-LPI) FL patients (Wang, 2005). The aim of our study was to identify outcomes for patients with LG-HPI FL at our institution. Methods: We conducted a single center, retrospective study of FL diagnosed from 1/1/2015-1/1/2021. Demographic information, diagnoses, laboratory results, medications, pathology, and radiology reports were collected from pts' electronic medical records. Pathology specimens were de-identified and retrospectively reviewed by two pathologists. Review included comprehensive evaluation of histologic grade, proliferation index by Ki-67 percentage (Ki-67%), immunohistochemical staining, and c-MYC immunohistochemical staining. Biopsies were classified as LG-LPI if Grade 1-2 and Ki-67 was Results: 152 pts were diagnosed with FL and included for analysis. Patient characteristics are summarized in Table 1. Median age at diagnosis for all pts was 65.9 years. Sixty-three pts had LG-LPI, 61 LG-HPI, and 28 HG pts. Ten pts transformed to DLBCL (2 LG-LPI, 5 LG-HPI, 3 HG). Treatment regimens included initial observation (n = 44), anti-CD20 therapy alone (n = 24), chemo-immunotherapy (n = 53), and other (n = 31). Median TTFT was 1.27 mo (range 0-115.2 mo). There was moderate correlation between SUV of biopsied lesion ≥10 and Ki-67 percentage (ROC Area 0.6175). Median PFS was longer for LG-LPI compared to LG-HPI (78.6 vs 57.8 mo, p = 0.04, HR 2.37) but not between LG-HPI and HG (57.8 vs 61.3 mo respectively, p = 0.32) (Figure 1A). Median OS was not reached in any cohort with median follow up of 29.5 mo. There was no difference in OS between LG-LPI vs LG-HPI (p = 0.53) (Figure 1B). Histologic grade, proliferation index, Ann Arbor Staging, FLIPI score, PET/CT SUV intensity (max or of biopsied lesion), presence of c-Myc staining, or initial treatment regimen were not associated with median PFS or OS in either subgroup on univariate analysis. Conclusions: In our cohort, PFS was shorter for LG-HPI compared to LG-LPI but with a similar trajectory to that of HG FL, consistent with prior reports. No differences were seen in OS between LG-HPI and LG-LPI, and no covariates of interest including histologic grade, proliferation index, Ann Arbor Staging, FLIPI score, PET/CT SUV intensity, presence of c-Myc staining, or initial treatment regimen were associated with differences in PFS or OS. Our study is limited by a short follow up time compared to prior published cohorts (29.5 vs 98.4 mo). PET/CT SUV values of ≥10 have moderate predictive value for higher proliferative disease and can aid in identifying patients with higher proliferative disease. Longer follow up is needed to determine if LG-HPI impacts OS. References: 1. SchöderH, et al. Intensity of 18fluorodeoxyglucose uptake in positron emission tomography distinguishes between indolent and aggressive non-Hodgkin's lymphoma. J Clin Oncol 2005;23:4643-51. 2. Rossi C, et al. Baseline SUVmaxis related to tumor cell proliferation and patient outcome in follicular lymphoma. Haematologica 2020;Online ahead of print. 3. Wang SA, et al. Low histologic grade follicular lymphoma with high proliferation index: morphologic and clinical features. Am J Surg Pathol2005;29:1490-6. Figure 1 Figure 1. Disclosures Allen: Sanofi Genzyme: Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Other: Equity Ownership; Bristol Myers Squibb: Other: Equity Ownership; Alexon: Research Funding. Rhodes: Conquer Cancer Foundation Young Investigator Award: Other: Grant/Research Support; AbbVie, Genentech, Pharmacyclics, TG Therapeutics: Other: Consultant.

Background : Ibr, an established standard of care in CLL, is a once-daily Bruton tyrosine kinase inhibitor with significant progression-free survival (PFS) and overall survival benefit shown in multiple randomized phase 3 studies in first-line CLL. Ven, an oral BCL-2 inhibitor approved as a single agent or combined with rituximab or obinutuzumab for CLL treatment, achieves high rates of undetectable MRD (uMRD). Ibr and Ven, with distinct and complementary mechanisms of action, work synergistically to mobilize CLL cells from lymph nodes and lymphoid niches, enhance cell killing, and eliminate distinct CLL cell populations. CAPTIVATE (PCYC-1142; NCT02910583) is an international, multicenter phase 2 study evaluating first-line Ibr + Ven in 2 cohorts: MRD and Fixed-Duration (FD). Patients (pts) first received 3 cycles of Ibr followed by 12 cycles of combined Ibr + Ven. In the primary analysis of the MRD cohort, pts with Confirmed uMRD who after fixed duration treatment were randomized to placebo or continued Ibr had similar post-randomization 1-year DFS rates (95% and 100%, respectively) (Wierda, ASH 2020). Two-year post-randomization results are presented. Methods : Pts aged Results : 164 pts were enrolled. Median age was 58 years (range, 28-69). High-risk features included unmutated IGHV (60% of pts), del(17p)/TP53 mutation (20%), complex karyotype (19%), and del(11q) without del(17p) (17%). After 12 cycles of Ibr + Ven, 149 pts were randomized: Confirmed uMRD to placebo (n=43) or Ibr (n=43); without Confirmed uMRD to Ibr (n=31) or Ibr + Ven (n=32). Median overall follow-up was 38.2 mo (range, 15.0-47.9); median post-randomization follow-up was 24.0 mo (range, 5.8-33.1). In pts with Confirmed uMRD randomized to placebo versus Ibr, no new DFS events occurred since the primary analysis; 2-year DFS rates post-randomization remained unchanged at 95% (placebo) vs 100% (Ibr), for a 4.7% difference (95% CI -1.6-10.9) and overall log-rank P=0.1573 (Figure 1). In the placebo and Ibr arms post-randomization, modest improvements were observed in complete response (CR) rates, including CR with incomplete bone marrow recovery (CRi) (Figure 2). Estimated 36-mo PFS rates were 95% with placebo and 100% with Ibr. In pts without Confirmed uMRD randomized to Ibr vs Ibr + Ven, greater improvements in best uMRD rates and CR/CRi rates were observed with Ibr + Ven than with Ibr post-randomization (Figure 2). Estimated 36-mo PFS rates were 97% with both Ibr and Ibr + Ven. Median treatment duration was 36.8 mo (range, 0.5-47.9) in all pts (N=164). Modest differences in AEs were observed across treatment arms post-randomization. During the overall study period across all-treated pts, the most frequent grade 3/4 AEs were neutropenia (36%), hypertension (10%), thrombocytopenia (5%), and diarrhea (5%). With up to 48 mo of treatment, AEs led to discontinuation of Ibr or Ven in 13% of pts; no new safety signals emerged. Conclusions : First-line Ibr + Ven is an all-oral, once-daily, chemotherapy-free regimen that provides deep responses in pts with CLL. With an additional year of follow-up and no new MRD relapses, PDs or deaths in pts with confirmed uMRD, the 2-year DFS rate in the MRD-guided placebo arm remained high at 95% while 3-year PFS rates were ≥95% across all randomized treatment arms. The results in pts with Confirmed uMRD support the potential for treatment-free remission with fixed-duration treatment, including in pts with high-risk features. High rates of uMRD were achieved; the safety profile of Ibr + Ven was consistent with known safety profile for each agent. Figure 1 Figure 1. Disclosures Ghia: Acerta/AstraZeneca: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding; ArQule/MSD: Consultancy, Honoraria; BeiGene: Consultancy, Honoraria; Celgene/Juno/BMS: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Sunesis: Research Funding; Roche: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Research Funding. Allan: Celegene: Research Funding; AstraZeneca Pharmaceuticals LP, Genentech, a member of the Roche Group, Janssen Biotech Inc, TG Therapeutics Inc.: Research Funding; AbbVie: Consultancy, Honoraria; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria; Genentech: Consultancy, Research Funding; TG Therapeutics: Research Funding; Epizyme: Consultancy; AbbVie Inc, AstraZeneca Pharmaceuticals LP, BeiGene, Janssen Biotech Inc, Pharmacyclics LLC: Consultancy; AbbVie Inc, Ascentage Pharma, Epizyme, Genentech, a member of the Roche Group, Janssen Biotech Inc, Pharmacyclics LLC: Other: Advisory Committee. Siddiqi: Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Juno therapeutics: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BeiGene: Other: DSM Member, Speakers Bureau; PCYC: Speakers Bureau; Jannsen: Speakers Bureau; Dava Oncology: Honoraria; ResearchToPractice: Honoraria. Kipps: Janssen: Consultancy, Honoraria, Other, Research Funding, Speakers Bureau; Roche: Honoraria, Other; MD Anderson Cancer Center: Research Funding; Velos: Research Funding; CRIM: Research Funding; Indy Hematology Review: Other; TG Therapeutics: Other; Verstem: Other, Speakers Bureau; University of California, San Diego: Current Employment; Pharmacyclics/AbbVie: Honoraria, Research Funding; Breast Cancer Research Foundation: Research Funding; SCOR - The Leukemia and Lymphoma Society: Research Funding; National Cancer Institute/NIH: Honoraria, Research Funding; Genentech/Roche: Honoraria; European Research Initiative on CLL (ERIC): Honoraria; Bionest Partner: Other; Celgene: Consultancy, Honoraria, Other, Research Funding; Genetech: Honoraria, Other; Genentech-Roche: Consultancy; Gilead Sciences: Consultancy, Honoraria, Other, Speakers Bureau; DAVA Pharmaceuticals: Speakers Bureau; DAVAOncology: Consultancy, Honoraria, Other; AbbVie: Consultancy, Honoraria, Other, Speakers Bureau; Oncternal Therapeutics, Inc.: Current holder of stock options in a privately-held company, Other: Stock or other ownership, Patents & Royalties: Cirmtuzumab was developed by Thomas J. Kipps in the Thomas J. Kipps laboratory and licensed by the University of California to Oncternal Therapeutics, Inc., which provided stock options and research funding to the Thomas J. Kipps laboratory., Research Funding; Moores Cancer Center: Current Employment; MedImmune Inc: Research Funding; GlaxoSmithKline: Research Funding; Gilead Sciences, Inc.: Honoraria, Research Funding; Genentech, Inc.: Honoraria, Research Funding, Speakers Bureau; Pharmacyclics LLC, an Abbvie Company: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Celgene Corporation: Consultancy, Honoraria, Research Funding; Abbott Laboratories: Consultancy, Research Funding. Kuss: Commonwealth Serum Laboratories: Other: Stock or other ownership; AbbVie: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Merck: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Kyowa Kirin: Consultancy, Honoraria; Mundipharma: Consultancy, Honoraria; Roche Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Janssen: Speakers Bureau. Opat: AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sandoz: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; CSL: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Monash Health: Current Employment; BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GIlead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding. Flinn: Portola Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; TG Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Loxo: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Incyte: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Juno Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Forma Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Seagen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Pfizer: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Roche: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Genentech: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; ArQule: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Merck: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Constellation Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Nurix Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Celgene: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Unum Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Novartis: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Great Point Partners: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; MorphoSys: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Verastem: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; BeiGene: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Teva: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Acerta Pharma: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Janssen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; IGM Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Takeda: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Curis: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Karyopharm Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Calithera Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Gilead Sciences: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Iksuda Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Kite, a Gilead Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Agios: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Infinity Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Rhizen Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Forty Seven: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; AstraZeneca: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; AbbVie: Consultancy, Other: All Consultancy and Research Funding payments made to Sarah Cannon Research Institute, Research Funding; Trillium Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Triphase Research & Development Corp.: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Century Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Hutchison MediPharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Vincerx Pharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Sarah Cannon Research Institute: Current Employment; Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Seagen: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Unum Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute, Research Funding; Johnson & Johnson: Current holder of individual stocks in a privately-held company; Seattle Genetics: Research Funding. Badoux: Janssen: Honoraria; AbbVie: Honoraria, Other: Travel, Accommodations, Expenses. Tedeschi: Beigene: Honoraria, Speakers Bureau; AstraZeneca: Honoraria, Speakers Bureau; AbbVie: Honoraria, Speakers Bureau; Janssen: Honoraria, Speakers Bureau. Gonzalez-Barca: Kiowa: Consultancy, Speakers Bureau; Eusapharma: Consultancy; Janssen: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; Takeda: Speakers Bureau; Roche: Other: Travel, Accommodations, Expenses; AbbVie: Other: Travel, Accommodations, Expenses, Speakers Bureau. Pagel: Pharmacyclics/AbbVie: Consultancy; Gilead: Consultancy; Actinium Pharmaceuticals: Consultancy; Kite, a Gilead Company: Consultancy; BeiGene: Consultancy; Epizyme: Consultancy; MEI Pharma: Consultancy; AstraZeneca: Consultancy; Incyte/MorphoSys: Consultancy. Jacobs: AstraZeneca: Consultancy, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding, Speakers Bureau; ADC Therapeutics: Consultancy; Adaptive Biotechnologies: Consultancy; MEI Pharma: Research Funding; TeneoBio: Research Funding; SecuraBio: Consultancy, Speakers Bureau; Verastem: Consultancy; TG Therapeutics: Research Funding, Speakers Bureau; Jannsen: Speakers Bureau; Genentech: Consultancy; AbbVie: Consultancy, Speakers Bureau. Szafer-Glusman: AbbVie: Current Employment, Other: Stock or other ownership. Zhou: AbbVie: Current Employment, Other: Stock and other ownership. Ninomoto: AbbVie: Current Employment, Other: Stock or other ownership. Dean: Pharmacyclics: Current Employment, Other: Stock or other ownership; AbbVie: Other: Stock Ownership. Tam: Pharmacyclics: Honoraria; BeiGene: Consultancy, Honoraria; Loxo: Consultancy; AbbVie: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Novartis: Honoraria. Wierda: Janssen: Research Funding; AstraZeneca: Research Funding; GSK/Novartis: Research Funding; Acerta Pharma Inc.: Research Funding; Karyopharm: Research Funding; Xencor: Research Funding; Oncternal Therapeutics, Inc.: Research Funding; Loxo Oncology, Inc.: Research Funding; Genentech: Research Funding; Sunesis: Research Funding; Miragen: Research Funding; Cyclacel: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Juno Therapeutics: Research Funding; Gilead Sciences: Research Funding; KITE Pharma: Research Funding; Genzyme Corporation: Consultancy; AbbVie: Research Funding. OffLabel Disclosure: Ibrutinib in combination with venetoclax is not approved in any indication.

Introduction: The receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a transmembrane protein that is overexpressed in multiple cancers, including hematological malignancies. Zilovertamab vedotin (MK-2140) is an antibody -drug conjugate comprising a humanized IgG1 monoclonal antibody, a proteolytically cleavable linker, and the antimicrotubule cytotoxic agent monomethyl auristatin E (MMAE). Preclinical evidence demonstrated the cytotoxicity of zilovertamab vedotin in hematologic cell lines. This first human phase 1 dose escalation study (NCT03833180) evaluated the safety and efficacy of zilovertamab vedotin at various doses in patients with relapsed/refractory hematologic malignancies. Methods: Eligible patients aged ≥18 years with an Eastern Cooperative Oncology Group Performance Status of 0-2 and histological diagnosis of chronic lymphocytic leukemia/small lymphocytic leukemia, lymphoplasmacytic lymphoma/Waldenström macroglobulinemia, acute lymphoid leukemia, acute myeloid leukemia, or non-Hodgkin lymphoma (NHL; mantle cell lymphoma [MCL], follicular lymphoma, marginal zone lymphoma, diffuse large B-cell lymphoma [DLBCL], Richter transformation, Burkitt lymphoma, and T-cell-NHL) were enrolled. Participants received zilovertamab vedotin intravenously at starting doses of 0.50 mg/kg (up to 2.5 mg/kg) on day 1 every 3 weeks (Q3W) (Schedule 1), 1.0 mg/kg (planned up to 2.25 mg/kg) on day 1 and 8 Q3W (Schedule 2), or 1.0 mg/kg (planned up to 2.25 mg/kg) on days 1, 8, and 15 Q4W (Schedule 3) using an accelerated plus 3+3 dose escalation design. The primary end point was determination of the maximum tolerated dose (MTD). Secondary end points included safety, objective response rate (ORR), and duration of response (DOR). We present data for participants with NHL enrolled in Schedule 1. Results: A total of 51 patients were enrolled in Schedule 1 (starting dose 0.5 [n=1], 1.00 [n=3], 1.50 [n=3], 2.00 [n=3], 2.25 [n=11], or 2.50 [n=30] mg/kg) as of the data cutoff of May 18, 2021. Median (range) age of patients was 70 (44-91) years, 54.9% of patients were male, 49.0% had an ECOG PS of 0, and 41/51 (80%) were diagnosed with NHL; 13/51 (25.5%) were diagnosed with DLBCL and 17/51 (33.3%) were diagnosed with MCL. Enrollment in Schedules 2 and 3 is currently ongoing. The MTD for Schedule 1 was determined to be 2.5 mg/kg. Any-cause adverse events (AEs) occurred in 48 patients (94.1%), most commonly (≥30%) nausea (45.1%), fatigue (45.1%), peripheral neuropathy (41.2%), diarrhea (37.3%), dizziness (35.3%), and neutrophil count decrease (33.3%). Grade ≥3 AEs occurred in 33 (64.7%) patients, most commonly (≥5%) neutrophil count decrease (29.4%), hemoglobin decrease (15.7%), febrile neutropenia (7.8%), peripheral neuropathy (7.8%), platelet count decrease (7.8%), diarrhea (5.9%), lipase increase (5.9%), and pneumonia (5.9%). One patient died due to acute respiratory failure; however, it was not considered treatment-related by the investigator. A total of 7 (13.7%) patients permanently discontinued due to an AE and 18 (35.3%) had treatment interrupted or reduced due to an AE. Treatment-related AEs occurred in 36 patients (70.6%), most commonly (≥20%) peripheral neuropathy (41.2%), fatigue (37.3%), neutrophil count decrease (29.4%), nausea (27.5%), and diarrhea (21.6%); 24 patients (47.1%) experienced a grade ≥3 treatment-related AE. For Schedule 1, ORR was 36.6% (15/41 [95% CI: 22.1%-53.1%]) among all participants with NHL, with 5 having a complete response (CR) and 10 having a partial response (PR). ORR was 38.5% (95% CI: 13.9%-68.4%) for the 13 patients in the NHL group who had DLBCL; 3 patients had a CR and 2 patients had a PR. ORR was 52.9% (95% CI: 27.8%-77.0%) for the 17 patients in the NHL group who had MCL; 2 patients had a CR and 7 patients had a PR. Median (range) DOR was 7.8 months (2.1-17.6+ months) among all participants in Schedule 1 with NHL who achieved a response. Conclusion: These data suggest that targeting the ROR1 pathway with zilovertamab vedotin is associated with a tolerable safety profile and promising antitumor activity in patients with relapsed/refractory NHL. Disclosures Wang: Anticancer Association: Honoraria; Dava Oncology: Honoraria; BioInvent: Research Funding; Bayer Healthcare: Consultancy; Hebei Cancer Prevention Federation: Honoraria; Lilly: Research Funding; Scripps: Honoraria; Kite Pharma: Consultancy, Honoraria, Research Funding; Juno: Consultancy, Research Funding; CAHON: Honoraria; InnoCare: Consultancy, Research Funding; Molecular Templates: Research Funding; Pharmacyclics: Consultancy, Research Funding; Oncternal: Consultancy, Research Funding; Miltenyi Biomedicine GmbH: Consultancy, Honoraria; Genentech: Consultancy; Newbridge Pharmaceuticals: Honoraria; VelosBio: Consultancy, Research Funding; Celgene: Research Funding; Physicians Education Resources (PER): Honoraria; The First Afflicted Hospital of Zhejiang University: Honoraria; OMI: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Loxo Oncology: Consultancy, Research Funding; BeiGene: Consultancy, Honoraria, Research Funding; DTRM Biopharma (Cayman) Limited: Consultancy; Chinese Medical Association: Honoraria; AstraZeneca: Consultancy, Honoraria, Research Funding; Clinical Care Options: Honoraria; Mumbai Hematology Group: Honoraria; Moffit Cancer Center: Honoraria; BGICS: Honoraria; CStone: Consultancy; Imedex: Honoraria; Epizyme: Consultancy, Honoraria; Acerta Pharma: Consultancy, Honoraria, Research Funding. Mei: Janssen: Honoraria; EUSA: Honoraria; Sanofi-Genzyme: Honoraria; Morphosys: Honoraria; TG Therapeutics: Other: Institution: Research Grant/Funding; Epizyme: Other: Institution: Research Grant/Funding; BMS: Other: Institution: Research Grant/Funding; Beigene: Other: Institution: Research Grant/Funding; Incyte: Other: Institution: Research Grant/Funding. Barr: Beigene: Consultancy; Gilead: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; AstraZeneca: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Abbvie/Pharmacyclics: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy. Furman: Acerta/AstraZeneca: Consultancy; Janssen: Consultancy, Honoraria; Beigene: Consultancy; Genentech: Consultancy; Incyte: Consultancy; Loxo Oncology: Consultancy; Abbvie: Consultancy, Honoraria, Other: Expert testimony; AstraZeneca: Honoraria; Sunesis: Consultancy; Oncotracker: Consultancy; Pharmacyclics: Consultancy; TG Therapeutics: Consultancy; Verastem: Consultancy; Morphosys: Consultancy; Sanofi: Consultancy; X4 Pharmaceuticals: Consultancy. Patel: TG Therapeutics: Consultancy, Speakers Bureau; Abbvie: Consultancy; Sunesis Pharmaceuticals: Research Funding; Juno Pharmaceuticals: Consultancy; MEI Pharma: Consultancy, Research Funding; Kite: Consultancy, Research Funding, Speakers Bureau; Millenium/Takeda: Research Funding; Pharmacyclics/Janssen: Consultancy, Research Funding, Speakers Bureau; Morphosys: Consultancy; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Genentech/Roche: Consultancy, Research Funding, Speakers Bureau; Trillium Therapeutics: Research Funding; BeiGene: Consultancy; Aptevo Therapeutics: Research Funding; Fate Therapeutics: Research Funding; Xencor: Research Funding; Velos Bio: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding, Speakers Bureau; Curis, Inc: Research Funding; Celgene: Consultancy, Research Funding, Speakers Bureau. Thompson: AbbVie: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Genentech: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Adaptive Biotechnologies: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding, Expert Testimony; Pharmacyclics: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Janssen: Consultancy, Honoraria; Gilead: Other: Institution: Advisory/Consultancy, Honoraria; Amgen: Other: Institution: Honoraria, Research Grant/Funding. Choi: Abbvie: Other: Institution: Research Grant/Funding; Pharmacyclics: Other: Institution: Research Grant/Funding; Oncternal: Other: Institution: Research Grant/Funding; Velosbio: Other: Institution: Research Grant/Funding; Merck: Other: Institution: Research Grant/Funding; Geron: Other: Institution: Research Grant/Funding. Zhu: Merck & Co., Inc.: Current Employment. Chakraborty: Merck & Co., Inc.: Current Employment, Other: Current Stockholder. Marinello: Merck & Co., Inc.: Current Employment, Other: Current Stockholder. Spurgeon: Ionis: Other: Institution: Research Grant/Funding; Gilead Sciences: Other: Institution: Research Grant/Funding; Bristol Myers Squibb: Other: Institution: Research Grant/Funding; BeiGene: Other: Institution: Research Grant/Funding; AstraZeneca: Other: Institution: Research Grant/Funding; Acerta Pharma: Other: Institution: Research Grant/Funding; Pharmacyclics: Consultancy; Janssen: Consultancy, Other: Institution: Research Grant/Funding; Genentech: Consultancy, Other: Institution: Research Grant/Funding; Karyopharm: Consultancy; Velos Bio: Consultancy, Other: Institution: Research Grant/Funding; Merck & Co., Inc.: Other: Institution: Research Grant/Funding; Fred Hutchinson Cancer Research Center: Other: Data Safety Monitoring Board.

Introduction: Cirmtuzumab (Cirm) is a high-affinity humanized monoclonal antibody designed to inhibit the tumor promoting activity of ROR1. In this study, we examined the safety and efficacy of Cirm in combination with ibrutinib (Ibr) in patients (pts) with MCL or CLL. ROR1 is an onco-embryonic tyrosine kinase-like receptor that is found at high levels on the cell surface of many hematologic and solid cancers. Activation of ROR1 by binding its ligands such as Wnt5a results in increased intracellular signaling, tumor growth and survival, enhanced cancer cell stemness and epithelial mesenchymal transition. Methods: Pts with relapsed or refractory (RR) MCL or treatment naïve (TN) or RR CLL were enrolled and treated in separate groups. In Part 1 Dose Escalation (DE), groups of MCL and CLL pts received Cirm IV q2wks x5 doses then q4wks at assigned doses of 2-16 mg/kg, and in CLL, additional fixed dose levels of 300 or 600 mg were evaluated. The safety and PK of single-agent Cirm was assessed during the first 28 days, and then Ibr was started at 560 mg/day PO for MCL or 420 mg/day PO for CLL. After reviewing the safety and PK data from Part 1, a recommended regimen of fixed dose Cirm 600 mg IV q2wks x3 then q4wks plus Ibr starting D0 was chosen for use in Parts 2 and 3. In Part 3, CLL pts (only) were randomized to either Cirm/Ibr vs. Ibr alone Results: As of April 30, 2020, 12 evaluable MCL pts were enrolled into Part 1 DE. Of these pts, 83% (10) had received ≥ 2 separate prior treatment regimens. In CLL, 34 pts (12 TN and 22 RR pts) enrolled into Part 1 DE (n= 18) or Part 2 Expansion (n= 16). At least 79% of CLL pts in Parts 1 and 2 were high risk as determined by unmutated IGHV, del17p, and/or del11q. Safety: For both MCL and CLL, the most common adverse events (AEs) considered at least possibly related to Cirm alone were grade 1/2 (e.g. fatigue, 6%) with no dose limiting toxicities or discontinuations. The combination of Cirm plus Ibr was well tolerated, with no new or accentuated AEs compared to the known safety profile of Ibr alone. Cirm may be lowering the rates of certain AEs normally seen with Ibr; for example, neutropenic events were 8 mos after stopping all therapy. At a median follow-up of 12.8 mos, 100% of CLL pts were free of disease progression and 82% remained on study. CLL cells collected after the first 28 days of treatment showed a decrease in stemness signature (Choi et al, Cell Stem Cell 2019), with similar reductions seen with single agent Cirm or Cirm + Ibr. Additional pts have been enrolled into Part 2 Expansion MCL and into Part 3 CLL. Early data from these arms are not yet available and will be reported later. Conclusions: Cirmtuzumab in combination with ibrutinib is a well-tolerated and active regimen for RR MCL and TN or RR CLL. The 58% CR/CMR rate for MCL compares favorably to published data with single agent Ibr of 27% (Rule, et al. Haematologica 2019) and it is encouraging that responses occurred in heavily pretreated pts, including those with high Ki-67 expression. In CLL, the high ORR and interim PFS are encouraging; the significance of these observations will be determined with longer follow-up. These data support the continued investigation of this regimen in ROR1-expressing hematologic and solid malignancies. This study is ongoing, and due to the high CR rate in MCL pts, the number of pts to be enrolled in the Part 2 Expansion will be increased to further characterize the safety and efficacy of this combination. Disclosures Lee: Bristol-Myers Squibb: Consultancy, Research Funding; Aptitude Health: Speakers Bureau; Celgene: Research Funding; Guidepoint Blogal: Consultancy; Oncternal Therapeutics: Research Funding; Seattle Genetics: Research Funding; Takeda: Research Funding. Choi:Pharmacyclics/Abbvie: Research Funding; Genentech: Consultancy. Siddiqi:Juno Therapeutics, Pharmacyclics LLC, an AbbVie Company, AstraZeneca, Celgene, Kite Pharma, and BeiGene: Consultancy; Pharmacyclics LLC, an AbbVie Company, Seattle Genetics, Janssen, and AstraZeneca: Speakers Bureau; BeiGene: Other: DMC member; AstraZeneca: Other: Travel/accommodations/expenses; Astrazenca: Membership on an entity's Board of Directors or advisory committees; PCYC: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie Company, Juno Therapeutics, KITE Pharma, AstraZeneca, TG Therapeutics, Celgene, Oncternal, and BeiGene: Research Funding. Barrientos:Oncternal Therapeutics: Research Funding; Gilead: Consultancy; AstraZeneca: Consultancy; Bayer: Consultancy; Sandoz: Consultancy; Janssen: Honoraria; Genentech: Consultancy. Lamanna:Octapharma: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bei-Gene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Institutional research grants, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Institutional research grants, Research Funding; Juno: Other: Institutional research grants, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; MingSight: Other: Institutional research grants, Research Funding; Oncternal, Verastem, TG Therapeutics: Other: Institutional research grants, Research Funding; Astra Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Institutional research grants, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Institutional research grants, Research Funding; Columbia University Medical Center: Current Employment; Loxo: Research Funding. Tuscano:Abbvie: Research Funding; Pharmacyclics: Research Funding; Celgene: Honoraria, Research Funding; Amgen: Honoraria; Seattle Genetics: Honoraria; Novartis: Research Funding; Spectrum: Research Funding; Takeda: Research Funding; Genentech: Research Funding. Leslie:KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Honoraria, Speakers Bureau; Karyopharm: Honoraria, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; BeiGene: Honoraria, Speakers Bureau; Celgene: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Ianopulos:Oncternal Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Breitmeyer:Oncternal Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Hsu:Oncternal Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company; Immune Design: Ended employment in the past 24 months. Wang:Beijing Medical Award Foundation: Honoraria; Lu Daopei Medical Group: Honoraria; MoreHealth: Consultancy; OMI: Honoraria, Other: Travel, accommodation, expenses; Targeted Oncology: Honoraria; Loxo Oncology: Consultancy, Research Funding; Pulse Biosciences: Consultancy; Kite Pharma: Consultancy, Other: Travel, accommodation, expenses, Research Funding; Juno: Consultancy, Research Funding; BioInvent: Research Funding; VelosBio: Research Funding; Acerta Pharma: Research Funding; InnoCare: Consultancy; Oncternal: Consultancy, Research Funding; Nobel Insights: Consultancy; Guidepoint Global: Consultancy; Dava Oncology: Honoraria; Verastem: Research Funding; Molecular Templates: Research Funding; OncLive: Honoraria; Celgene: Consultancy, Other: Travel, accommodation, expenses, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Pharmacyclics: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding. Jamieson:Bristol-Myers Squibb: Other; Forty Seven Inc: Patents & Royalties. Kipps:VelosBio: Research Funding; Pharmacyclics/ AbbVie, Breast Cancer Research Foundation, MD Anderson Cancer Center, Oncternal Therapeutics, Inc., Specialized Center of Research (SCOR) - The Leukemia and Lymphoma Society (LLS), California Institute for Regenerative Medicine (CIRM): Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Research Funding; Ascerta/AstraZeneca, Celgene, Genentech/F. Hoffmann-La Roche, Gilead, Janssen, Loxo Oncology, Octernal Therapeutics, Pharmacyclics/AbbVie, TG Therapeutics, VelosBio, and Verastem: Membership on an entity's Board of Directors or advisory committees; Oncternal Therapeutics, Inc.: Other: Cirmtuzumab was developed by Thomas J. Kipps in the Thomas J. Kipps laboratory and licensed by the University of California to Oncternal Therapeutics, Inc., which provided stock options and research funding to the Thomas J. Kipps laboratory, Research Funding.

Background: Treatment options, together with guidelines, for pts with CLL have evolved and expanded with the introduction of novel agents. The informCLLTM registry is the largest US-based prospective, observational registry of pts who received treatment for CLL/SLL in the post-novel agent era. This prospective real-world registry is uniquely positioned to examine the impact of the dynamic treatment landscape, treatment practices, and outcomes in routine clinical setting. Here we present baseline characteristics, prognostic biomarker testing, and treatment patterns for the fully enrolled pt population. Methods: From Oct 2015 to June 2019, informCLL (PCYC-1134; NCT02582879) enrolled eligible pts with CLL/SLL who were ≥18 years (y), initiated FDA-approved treatment for CLL/SLL within ±45 days of enrollment and provided consent. Pts were classified into 5 groups based on treatment received at enrollment (index): ibrutinib (single agent or combination), chemoimmunotherapy (CIT), chemotherapy (CT), immunotherapy (IT), and other novel agents. Descriptive analyses are presented. Results: The registry fully enrolled with 1461 pts: 855 (59%) previously untreated and 606 (41%) relapsed/refractory (R/R) pts. Community-based practices enrolled 93% of pts. The median age was 71 y (33% ≥75 y), the majority were male (64%), and 88% had ECOG performance status of 0/1. For pts with staging performed at enrollment (n=852), 51% had Rai stage III/IV. Median (range) time from diagnosis to initial treatment on study was 18.6 months (mos, FISH testing was performed in 28% (n=415) of pts and was more frequent in previously untreated vs R/R pts (33% vs 21%). TP53 mutation testing was performed in 11% (n=162) of pts (previously untreated: 13%; R/R: 9%). IGHV mutational status testing was performed in 12% (n=171) of pts (previously untreated: 13%; R/R 10%). Of pts with prognostic biomarker testing, 24% (100/415) had del(17p), 27% (43/162) had TP53 mutation, and 71% (121/171) had unmutated IGHV. Prognostic biomarker testing by treatment group is shown in Figure 1. Table 1 shows the distribution of pts receiving different treatments on study. Across lines of therapy, the most common treatment was ibrutinib (46%); the majority (87%) started ibrutinib treatment at the recommended daily dose of 420 mg, and pts continuing ibrutinib therapy largely did not require dose modifications (75%). At 12 or 24 mos, 77% (307/401) and 68% (126/184) of pts continued on ibrutinib treatment, respectively. For pts who completed the most common CIT regimens (bendamustine + rituximab [BR] and fludarabine + cyclophosphamide + rituximab), 80% and 85%, respectively, received Conclusions: The informCLL registry provides an opportunity to prospectively assess CLL treatment patterns in the era of novel agents. The most common index treatment was ibrutinib and the majority of ibrutinib-treated pts remained on therapy at 2 y follow-up; CIT (primarily BR) was also used for one-third of patients. Prognostic biomarker testing rates were poor, especially for TP53 and IGHV mutational status. Data from informCLL also indicate a 'knowledge gap' in terms of prognostic marker testing and selection of therapies for pts with high-risk disease. Data from the now complete pt population and with continued follow up will allow for the ongoing evaluation of real-world treatment decisions and pt care that cannot be addressed by data from randomized clinical trials. Disclosures Mato: Janssen: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Genentech: Consultancy, Research Funding; BeiGene: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; LOXO: Consultancy, Research Funding. Barrientos:Janssen: Honoraria; Oncternal Therapeutics: Research Funding; Sandoz: Consultancy; Gilead: Consultancy; Genentech: Consultancy; Bayer: Consultancy; AstraZeneca: Consultancy. Sharman:AbbVie: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; BeiGene: Research Funding; Bristol Meyers Squibb: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Acerta: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Brander:BeiGene: Other, Research Funding; MEI Pharma: Other, Research Funding; DTRM: Other, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; ArQule: Consultancy, Other, Research Funding; Pfizer: Consultancy, Other; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; Ascentage: Other, Research Funding; Teva: Consultancy, Honoraria; Tolero: Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Verastem: Consultancy, Honoraria, Other, Research Funding; NCCN: Other; Novartis: Consultancy, Other; NCCN: Other; Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding. Kadish:Bluebird Bio: Current equity holder in publicly-traded company; Blueprint Medicines: Current equity holder in publicly-traded company; Teva Pharmaceutical: Current equity holder in publicly-traded company; Bristol-Myers Squibb: Current equity holder in publicly-traded company; Editas Medicine: Current equity holder in publicly-traded company; Johnson & Johnson: Current equity holder in publicly-traded company; Sarepta Therapeutics: Current equity holder in publicly-traded company; AbbVie: Current equity holder in publicly-traded company; Agios: Current equity holder in publicly-traded company; Celgene: Current equity holder in publicly-traded company, Speakers Bureau; Takeda: Speakers Bureau. Arango-Hisijara:Bristol-Myers Squibb: Current equity holder in publicly-traded company; AbbVie: Current equity holder in publicly-traded company; Pharmacyclics LLC, an AbbVie Company: Current Employment. Upasani:AbbVie: Current equity holder in publicly-traded company; Pharmacyclics LLC, an AbbVie Company: Current Employment; Protagonist Therapeutics: Current Employment. Han:Johnson and Johnson: Current equity holder in publicly-traded company; Janssen: Current Employment, Other: Travel expenses. Huang:Janssen Scientific Affairs, LLC: Current Employment; Johnson & Johnson: Current equity holder in publicly-traded company. Iyengar:Express Scripts: Patents & Royalties; AbbVie: Current equity holder in publicly-traded company; Pharmacyclics LLC, an AbbVie Company: Current Employment. Ghosh:Karyopharm: Consultancy; Genmab: Consultancy, Speakers Bureau; SGN: Consultancy, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau; Juno/Celgene/Bristol-Myers Squibb: Consultancy, Research Funding; Janssen: Consultancy, Research Funding, Speakers Bureau; Forty Seven Inc: Consultancy, Other: Research Bureau, Research Funding; Celgene/Bristol-Myers Squibb: Speakers Bureau; AbbVie: Speakers Bureau; AstraZeneca: Speakers Bureau; TG Therapeutics: Consultancy, Research Funding; Roche/Genentech: Research Funding.

Introduction: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein that is physiologically expressed during embryogenesis, largely disappears by birth, but can be reexpressed pathologically in transformed tissues of many hematological and solid cancers. VLS-101 is an antibody-drug conjugate (ADC) comprising a rapidly internalizing, humanized monoclonal antibody (UC-961) that recognizes extracellular ROR1, a cleavable linker, and the anti-microtubule cytotoxin, monomethyl auristatin E (MMAE). Methods: This first-in-human, Phase 1 study evaluated the safety, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and efficacy of VLS-101 in patients unselected for tumor ROR1 expression who had previously treated chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), or Richter transformation lymphoma (RTL). VLS-101 was infused over 30 min every 3 wk until cancer progression or intolerable toxicity. After accrual of 1 patient at the first dose level, cohorts were enrolled by 3+3 dose escalation with additional patients accrued and intrapatient dose escalation permitted to refine estimates of maximum tolerated dose and recommended dosing regimen (RDR). Results: 32 patients were enrolled, including 19 males and 13 females with median (range) ages of 70 (54-84) ys; ECOG performance status (n) of 0 (18), 1 (10), or 2 (4); and tumor types (n) of MCL (15), CLL (7), DLBCL (5), FL (3), MZL (1), and RTL (1). Patients had received a median (range) of 4 (1-24) prior systemic therapies including hematopoietic stem cell transplantation (5) and/or chimeric antigen receptor (CAR)-T or -natural killer (NK) cells (6). Among patients with MCL, 15/15 (100%) had received a Bruton tyrosine kinase inhibitor (BTKi), 13/15 (87%) discontinued the BTKi due to progressive disease, and 2/15 (13%) discontinued for atrial fibrillation after 15.6 or 68.5 months of BTKi therapy. Patients (n) by VLS-101 starting dose were 0.5 (1), 1.0 (3), 1.5 (3), 2.25 (11), and 2.5 (14) mg/kg. With intrapatient dose escalation, many patients (n) received a maximum of 2.25 mg/kg (12) or 2.5 mg/kg (17) during VLS-101 therapy (range: 1 to 13 cycles). Cycle 1 DLTs (n/N) by mg/kg dose level were 0.5 (0/1), 1.0 (0/3), 1.5 (0/3), 2.25 (1/11 [9%] Gr 4 neutropenia), and 2.5 (2/14 [14%]; one Gr 4 neutropenia; one Gr 3 diarrhea of uncertain cause). Gr 4 neutropenia occurred in 9/32 (28%) patients; 1/32 (3%) had neutropenic fever. Granulocyte colony-stimulating factor successfully ameliorated neutropenia. Baseline Gr 1 neuropathy was present in 10/32 (31%) patients. On-study reversible Gr 3 neuropathy occurred in 3/32 (9%) patients; no Gr 4 neuropathy occurred. Except for Gr ≤2 alopecia in 3/32 (9%) patients, other adverse events were not obviously drug-related. Considering all 175 infusions administered, drug-related infusion reactions, vomiting, tumor lysis syndrome, rash, hepatic or renal abnormalities, or QT prolongation were not observed. PK showed changes in ADC and MMAE exposures proportional with VLS-101 dose and a mean ADC half-life of ~2.5 d. PD indicated exposure-dependent ROR1 occupancy on circulating CLL cells. No neutralizing anti-drug antibodies were detected. Objective tumor responses were not seen in patients with other tumor types but were observed in 7/15 (47%) of patients with MCL (4 partial; 3 complete) and in 4/5 (80%) of patients with DLBCL (2 partial; 2 complete). From start of therapy, 6/7 patients with responding MCL have responses ongoing at 35, 38, 45, 47, 50, and 58 wk and 2/4 patients with responding DLBCL have responses ongoing at 23 and 47 wk of follow-up. Conclusions: In heavily pretreated patients, VLS-101 infusions were well tolerated and demonstrated a predictable safety profile consistent with an MMAE-containing ADC. Tumor selectivity was confirmed, with no evidence of ROR1-mediated toxicities or non-MMAE toxicities that would suggest normal tissue binding. Considering all data, the VLS-101 RDR was 2.5 mg/kg every 3 wk. Efficacy results provide clinical proof of concept for targeting ROR1 with VLS-101 and demonstrate durable objective responses in patients with advanced MCL or DLBCL, including those with prior BTKi or cellular therapies. Phase 1-2 studies of VLS-101 monotherapy and combination therapy in patients with hematological cancers and solid tumors are planned. Figure Disclosures Wang: Nobel Insights: Consultancy; Lu Daopei Medical Group: Honoraria; Oncternal: Consultancy, Research Funding; MoreHealth: Consultancy; Juno: Consultancy, Research Funding; Loxo Oncology: Consultancy, Research Funding; Acerta Pharma: Research Funding; InnoCare: Consultancy; OncLive: Honoraria; Guidepoint Global: Consultancy; VelosBio: Research Funding; Pulse Biosciences: Consultancy; Kite Pharma: Consultancy, Other: Travel, accommodation, expenses, Research Funding; Beijing Medical Award Foundation: Honoraria; Pharmacyclics: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; OMI: Honoraria, Other: Travel, accommodation, expenses; Celgene: Consultancy, Other: Travel, accommodation, expenses, Research Funding; BioInvent: Research Funding; Molecular Templates: Research Funding; Verastem: Research Funding; Dava Oncology: Honoraria; AstraZeneca: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Targeted Oncology: Honoraria. Barrientos:Gilead: Consultancy; Genentech: Consultancy; Bayer: Consultancy; Oncternal Therapeutics: Research Funding; Sandoz: Consultancy; Janssen: Honoraria; AstraZeneca: Consultancy. Furman:Verastem: Consultancy; Incyte: Consultancy; Janssen: Consultancy, Speakers Bureau; Loxo Oncology: Consultancy; Oncotarget: Consultancy; Pharmacyclics: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy, Research Funding; Acerta: Consultancy; Abbvie: Consultancy; AstraZeneca: Consultancy, Research Funding; Beigene: Consultancy; Genentech: Consultancy. Mei:Sanofi: Consultancy; Morphosys: Membership on an entity's Board of Directors or advisory committees. Barr:AstraZeneca: Consultancy, Research Funding; Verastem: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Merck: Consultancy; Morphosys: Consultancy; Gilead: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Janssen: Consultancy; Genentech: Consultancy. Choi:Genentech: Consultancy; Pharmacyclics/Abbvie: Research Funding. de Vos:Bayer: Consultancy; Verastem: Consultancy. Patel:Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; Kite: Consultancy; Janssen: Consultancy, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Adaptive Biotechnologies: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Rule:Janssen: Consultancy; Kite: Consultancy; Pharmacyclics: Consultancy. Flanders:VelosBio: Current Employment, Current equity holder in private company. Jessen:VelosBio: Current Employment, Current equity holder in private company; eFFECTOR: Current equity holder in private company. Riebling:VelosBio: Current Employment, Current equity holder in private company. Graham:Ce3: Current Employment. King:Ce3: Current Employment; VelosBio: Consultancy; AI Therapeutics: Consultancy. Schmidt:VelosBio: Current Employment, Current equity holder in private company; Gilead Sciences: Current equity holder in publicly-traded company. Lannutti:VelosBio: Current Employment, Current equity holder in private company; Gilead Sciences: Current equity holder in publicly-traded company. Johnson:Zentalis: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Current equity holder in publicly-traded company; Neoleukin: Current equity holder in publicly-traded company; Oncternal: Divested equity in a private or publicly-traded company in the past 24 months; Appelis: Divested equity in a private or publicly-traded company in the past 24 months; Acerta: Patents & Royalties; VelosBio: Current Employment, Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Miller:Cleveland BioLabs: Consultancy, Current equity holder in publicly-traded company; Gilead Sciences: Current equity holder in publicly-traded company; Cancer Genetics: Current equity holder in publicly-traded company; Incuron: Consultancy; Zentalis: Consultancy, Current equity holder in publicly-traded company; AbbVie: Current equity holder in publicly-traded company; EpiThany: Current equity holder in private company; AstraZeneca: Current equity holder in publicly-traded company; VelosBio: Consultancy, Current Employment, Current equity holder in private company; AI Therapeutics: Consultancy, Current equity holder in private company; Catalys Pacific: Consultancy. Spurgeon:Cardinal Health: Honoraria; VelosBio: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Pharmacyclics: Consultancy; Bristol-Myers Squibb: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Acerta: Research Funding; AstraZeneca: Research Funding; Genmab: Research Funding; Beigene: Research Funding; Verastem: Research Funding.

Ibrutinib, an oral inhibitor of Bruton's tyrosine kinase (BTK), at a once-daily dose of 420 mg achieved BTK active-site occupancy in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) that was maintained at 24 hours. It is unknown if intermittent interruption of ibrutinib therapy contributes to altered clinical outcomes. We therefore evaluated the effect of ibrutinib dose adherence on patient outcomes in the phase 3 RESONATE trial. The overall mean dose intensity (DI) was 95% with median treatment duration of similar to 9 months. Pharmacokinetic assessment of ibrutinib exposure at 420-mg dose suggested similar exposure regardless of patient weight or age. As assessed by independent review committee, patients with higher DI experienced longer median progression-free survival (PFS) compared with those with lower DI regardless of del17p and/or TP53 status. Of 79 patients requiring a drug hold, treatment was restarted at the original dose in 73 (92%) patients. Mean duration of a missed-dose event was 18.7 days (range, 8-56). Patients missing >= 8 consecutive days of ibrutinib had a shorter median PFS vs those missing

To the editor: Ibrutinib, approved by the US Food and Drug Administration (FDA), is an inhibitor of Bruton tyrosine kinase (BTK).[1][1][⇓][2][⇓][3][⇓][4]-[5][5] Ibrutinib use is associated with atrial fibrillation (AF), with an incidence of 5% to 6% after 18 months on therapy[4][4][⇓][5]-[6

Marginal zone lymphoma (MZL) is a heterogeneous B-cell malignancy for which no standard treatment exists. MZL is frequently linked to chronic infection, which may induce B-cell receptor (BCR) signaling, resulting in aberrant B-cell survival and proliferation. We conducted a multicenter, open-label, phase 2 study to evaluate the efficacy and safety of ibrutinib in previously treated MZL. Patients with histologically confirmed MZL of all subtypes who received ≥1 prior therapy with an anti-CD20 antibody–containing regimen were treated with 560 mg ibrutinib orally once daily until progression or unacceptable toxicity. The primary end point was independent review committee–assessed overall response rate (ORR) by 2007 International Working Group criteria. Among 63 enrolled patients, median age was 66 years (range, 30-92). Median number of prior systemic therapies was 2 (range, 1-9), and 63% received ≥1 prior chemoimmunotherapy. In 60 evaluable patients, ORR was 48% (95% confidence interval [CI], 35-62). With median follow-up of 19.4 months, median duration of response was not reached (95% CI, 16.7 to not estimable), and median progression-free survival was 14.2 months (95% CI, 8.3 to not estimable). Grade ≥3 adverse events (AEs; >5%) included anemia, pneumonia, and fatigue. Serious AEs of any grade occurred in 44%, with grade 3-4 pneumonia being the most common (8%). Rates of discontinuation and dose reductions due to AEs were 17% and 10%, respectively. Single-agent ibrutinib induced durable responses with a favorable benefit–risk profile in patients with previously treated MZL, confirming the role of BCR signaling in this malignancy. As the only approved therapy, ibrutinib provides a treatment option without chemotherapy for MZL. This study is registered at www.clinicaltrials.gov as #NCT01980628.

Idelalisib, a first-in-class oral inhibitor of phosphatidylinositol-3-kinase δ, has shown considerable antitumor activity as a monotherapy in recurrent indolent non-Hodgkin lymphoma (iNHL). To evaluate the safety and activity of idelalisib in combination with immunotherapy, chemotherapy, or both, 79 patients with relapsed/refractory iNHL were enrolled based on investigator preference in 3 treatment groups. Patients received continuous idelalisib in combination with (1) rituximab (IR; 375 mg/m2 weekly × 8 doses), (2) bendamustine (IB; 90 mg/m2 per day × 2, for 6 cycles), or (3) both bendamustine and rituximab at aforementioned doses (IBR; monthly × 6 cycles). Patients had a median age of 61 years, a median of 3 prior therapies, and 46% had refractory disease. The overall response rate was 75% (22% complete response) for IR, 88% (36%) for IB, and 79% (43%) for IBR. The median progression-free survival was 37.1 months overall: 29.7 months for IR, 32.8 for IB, and 37.1 months for IBR. The median duration of response was 28.6 months in the IR group and has not been reached in the IB and IBR groups. The most common grade ≥3 adverse events and laboratory abnormalities were neutropenia (41%), pneumonia (19%), transaminase elevations (16%), diarrhea/colitis (15%), and rash (9%). The safety and efficacy reflected in these early data, however, stand in contrast with later observations of significant toxicity in subsequent phase 3 trials in frontline chronic lymphocytic leukemia and less heavily pretreated iNHL patients. Our findings highlight the limitations of phase 1 trial data in the assessment of new regimens. This trial was registered at www.clinicaltrials.gov as #NCT01088048 (an extension study was registered at www.clinicaltrials.gov as #NCT01090414).

The efficacy of ibrutinib has been demonstrated in patients with chronic lymphocytic leukemia (CLL), including as first‐line therapy. However, outcomes after ibrutinib discontinuation have previously been limited to higher‐risk populations with relapsed/refractory (R/R) disease. The objective of this study was to evaluate outcomes of ibrutinib‐treated patients based on prior lines of therapy, including after ibrutinib discontinuation. Data were analyzed from two multicenter phase 3 studies of single‐agent ibrutinib: RESONATE (PCYC‐1112) in patients with R/R CLL and RESONATE‐2 (PCYC‐1115) in patients with treatment‐naive (TN) CLL without del(17p). This integrated analysis included 271 ibrutinib‐treated non‐del(17p) patients with CLL (136 TN and 135 R/R). Median progression‐free survival (PFS) was not reached for subgroups with 0 and 1/2 prior therapies but was 40.6 months for patients with ≥3 therapies (median follow‐up: TN, 36 months; R/R, 44 months). Median overall survival (OS) was not reached in any subgroup. Overall response rate (ORR) was 92% in TN and 92% in R/R, with depth of response increasing over time. Adverse events (AEs) and ibrutinib discontinuation due to AEs were similar between patient groups. Most patients (64%) remain on treatment. OS following discontinuation was 9.3 months in R/R patients (median follow‐up 18 months, n = 51) and was not reached in TN patients (median follow‐up 10 months, n = 30). In this integrated analysis, ibrutinib was associated with favorable PFS and OS, and high ORR regardless of prior therapies in patients with CLL. The best outcomes following ibrutinib discontinuation were for patients receiving ibrutinib in earlier lines of therapy.

BACKGROUND: Chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab (FCR) has been the standard therapy for younger patients with CLL. FCR therapy is particularly effective in patients with immunoglobulin heavy chain variable region (IGHV) mutated CLL. Approximately half of IGHV mutated patients are progression free 8 years after FCR therapy. At the ASH 2018 meeting, we reported the initial results of the ECOG 1912 (E1912) trial, a phase 3 trial comparing the FCR regimen to the combination of ibrutinib and rituximab (IR) for previously untreated CLL patients age 70 or younger who required therapy. With median follow-up of approximately 34 months, the trial demonstrated both a progression-free survival (PFS) and an overall survival (OS) benefit relative to FCR. On sub-set analysis by IGHV mutation status, the difference in PFS was statistically significant for IGHV unmutated patients but, with current follow-up, not IGHV mutated patients. Here, we present updated results for PFS in the E1912 trial. METHODS: As previously reported, eligible patients were treatment-naive individuals with CLL age 70 or younger. Patients with deletion 17p- were excluded from participating in the E1912 trial given their known poor response to FCR therapy. Patients were randomly assigned in a two-to-one ratio to receive ibrutinib (420 mg/day until disease progression or unacceptable toxicity) and rituximab (50 mg/m2 on day 1 of cycle 2, 325 mg/m2 on day 2 of cycle 2, and then 500 mg/m2 on day 1 of cycles 3-7) or six courses of intravenous fludarabine (25 mg/m2 days 1-3), cyclophosphamide (250 mg/m2 days 1-3) and rituximab (50 mg/m2 on day 1 of cycle 1, 325 mg/m2 on day 2 of cycle 1, and then 500 mg/m2 on day 1 of cycles 2-6) every 28-days. Adverse events (AEs) were graded according to the NCI Common Toxicity Criteria (version 4). Dose adjustments for cytopenias were based on the IWCLL CLL Working Group grading scale. The primary endpoint of the trial was PFS with OS a secondary endpoint. Analysis was by intention to treat. RESULTS: With median follow-up of 45 months, 257 (73%) of 354 patients randomized to IR remain on ibrutinib. With extended follow-up, grade 3 and above treatment-related AEs were observed in 70% of IR and 80% of FCR treated patients (OR=0.56; 95% CI 0.34 - 0.90; p=0.013). Among IR-treated patients, the median time on treatment is currently 43 months (range=0.2-61). Among the 95 patients who have discontinued ibrutinib, the reason for discontinuation was progression or death in 23 (7% of patients who started IR; 24% of those who discontinued treatment), AE or complication in 48 (14% of patients who started IR; 51% of those who discontinued treatment), and withdrawal of consent or other reasons in 24 (7% of patients who started IR; 25% of those who discontinued treatment). On multivariable Cox regression adjusting for Timed Up and Go test score, Cumulative Illness Rating Scale (CIRS) score, age, gender, ECOG performance status, creatinine clearance, and baseline anemia/thrombocytopenia, only CIRS score (range 0 - 14) predicted discontinuation of ibrutinib for a reason other than progression or death (HR=1.13 per unit increase; 95% CI 1.03 - 1.23; p=0.009). Among the 72 patients who discontinued ibrutinib for a reason other than progression or death, the median time on ibrutinib was 15.1 months (range 0.2-58.2 months). The median time from ibrutinib discontinuation to disease progression or death was 23 months. With current follow-up, we observed 110 PFS events. The hazard ratio (HR) for PFS favored IR over FCR (HR=0.39; 95% CI 0.26-0.57; p CONCLUSIONS: Although less than 7% of ibrutinib treated patients progressed while on therapy, roughly 1 in 5 patients have discontinued ibrutinib for a reason other than progression or death. The only parameter significantly associated with discontinuation for a reason other than progression was increased baseline CIRS score. With extended follow-up, the combination of ibrutinib and rituximab continues to provide superior PFS compared to FCR for younger patients with previously untreated CLL. Disclosures Shanafelt: Pharmacyclics: Research Funding; Patent: Patents & Royalties: US14/292,075 on green tea extract epigallocatechin gallate in combination with chemotherapy for chronic lymphocytic leukemia; Polyphenon E International: Research Funding; Merck: Research Funding; Abbvie: Research Funding; Genentech: Research Funding; Celgene: Research Funding; Glaxo-SmithKline: Research Funding; Hospira: Research Funding; Cephalon: Research Funding. Kay:MorphoSys: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Agios: Other: DSMB. O'Brien:Janssen: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Astellas: Consultancy; Aptose Biosciences, Inc: Consultancy; Amgen: Consultancy; Alexion: Consultancy; Acerta: Research Funding; Eisai: Consultancy; Gilead: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Verastem: Consultancy; Celgene: Consultancy; Sunesis: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Vaniam Group LLC: Consultancy; Regeneron: Research Funding; Kite: Research Funding. Barrientos:AbbVie: Consultancy, Research Funding; AstraZeneca: Consultancy; Genentech: Consultancy; Bayer: Consultancy; Gilead: Consultancy; Janssen: Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Sandoz: Consultancy; Oncternal Therapeutics: Research Funding. Coutre:Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Astra Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta: Research Funding; Gilead: Research Funding; BeiGene: Other: Travel, Accommodations, Expenses & Data Safety Monitoring Committee; Genentech: Consultancy. Barr:Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Gilead: Consultancy; Verastem: Consultancy; Genentech: Consultancy; Seattle Genetics: Consultancy; Merck: Consultancy; Celgene: Consultancy; Janssen: Consultancy; AbbVie: Consultancy; Astra Zeneca: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Cashen:Celgene: Other: Speaker's Bureau; Seattle Genetics: Other: Speaker's Bureau; Novartis: Other: Speaker's Bureau. Mato:AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Genentech: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Gilead: Research Funding; Acerta: Consultancy; Janssen: Consultancy. Erba:Amgen: Consultancy; MacroGenics: Consultancy, Other: Lecture fees, Research Funding; MacroGenics: Consultancy, Other: Lecture fees, Research Funding; Novartis: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; ImmunoGen: Consultancy, Research Funding; Astellas Pharma: Consultancy; Astellas Pharma: Consultancy; Amgen: Consultancy; GlycoMimetics: Consultancy, Other: Chair, data and safety monitoring board, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Celgene: Consultancy, Other: chair, AML Registry Scientific Steering Committee, Speakers Bureau; ImmunoGen: Consultancy, Research Funding; AbbVie: Consultancy, Other: Chair, IRC for phase III studies, Research Funding; GlycoMimetics: Consultancy, Other: Chair, data and safety monitoring board, Research Funding; Covance: Other: Fees for serving as chair on an independent review board for AbbVie Phase III studies; Covance: Other: Fees for serving as chair on an independent review board for AbbVie Phase III studies; AbbVie: Consultancy, Other: Chair, IRC for phase III studies, Research Funding; Celgene: Consultancy, Other: chair, AML Registry Scientific Steering Committee, Speakers Bureau; Pfizer: Consultancy; Pfizer: Consultancy; Seattle Genetics: Consultancy; Seattle Genetics: Consultancy; Daiichi Sankyo: Consultancy, Research Funding. Stone:Arog Pharmaceuticals: Consultancy, Honoraria, Research Funding; Otsuka-Astex Pharmaceuticals: Consultancy; Fujifilm: Consultancy; AstraZeneca: Consultancy; Celator Pharmaceuticals: Consultancy; Abbvie: Consultancy, Research Funding; Ono Pharmaceutical-Theradex Oncology: Consultancy; Cornerstone Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Takeda: Other: Fees for serving on a data and safety monitoring board ; Orsenix: Consultancy; MacroGenics: Consultancy; Jazz Pharmaceuticals: Consultancy; Agios: Consultancy, Research Funding; Stemline Therapeutics: Consultancy; Pfizer: Consultancy; Celgene: Consultancy, Other: Fees for serving on a steering committee, and fees for serving on a data and safety monitoring board; Novartis: Consultancy, Research Funding; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Astellas Pharma: Membership on an entity's Board of Directors or advisory committees; Argenx: Other: Fees for serving on a data and safety monitoring board ; Roche: Consultancy. Tallman:Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncolyze: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Introduction: Venetoclax (VEN) based therapy has become a standard of care in front line and relapsed-refractory (R/R) CLL based on favorable efficacy and toxicity. Whereas prospective data regarding activity of therapies following ibrutinib (IBR) or idelalisib (IDE) are available in the settings of progression (VEN, non-covalent BTKi) and intolerance (acalabrutinib), how best to manage patients (pts) who discontinue (dc) VEN remains a key unanswered question. With the increased use of VEN in early lines of therapy (LOT; CLL 14, MURANO), the activity of BTK inhibitors (BTKi) and cellular therapies following VEN becomes a critical issue. No prospective study has addressed this question, and currently reported VEN clinical trials have limited information about subsequent treatments. While recent data describe VEN resistance mechanisms (Guieze 2018, Blombery 2019), the impact of VEN resistance on efficacy of post VEN therapies is unknown. To address this gap, we conducted an international study to identify a large cohort of pts who dc VEN and have been subsequently treated. Methods: We conducted an IRB approved multicenter (31 US, EU, South American sites, in partnership with UK CLL Forum and CORE registry), retrospective cohort study of CLL pts who dc VEN for any reason. We examined demographics, dc reasons, responses, survival, adverse events (AEs) and activity of post VEN therapies. Primary endpoints were overall response rate (ORR) and progression free survival (PFS) for the post VEN treatments stratified by treatment type (BTKi, PI3Ki and cellular therapy: CAR-T or alloHSCT). ORR was defined by iwCLL criteria and PFS was defined from VEN dc to disease progression (PD), death, or last follow up for next treatment. Pts were further stratified by BTKi (resistant / intolerant) and PI3Ki exposure prior to VEN. PFS-2 was defined as time from VEN start to tumor progression on IBR or death from any cause. Results: 326 CLL pts who dc VEN in the front line (4%) and R/R settings (96%) were identified. The cohort was 69% male, 87% white, median (med) age 66 (38-91) at VEN start, 27% treated with VEN based combinations (n=88, med 6 cycles anti-CD20 abs). Pre VEN prognostic features: 82% IGHV unmutated (n tested=166), 47% del17p (n=306), 45% TP53 mut (n=217), 39% complex karyotype (n=273), 23% BTK mut (n=79), 18% NOTCH1 mut (n=103), 10% PLCγ2 mut (n=74). Pts received med 3 therapies (0-11) prior to VEN; 40% were BTKi naïve (n=130), 60% were BTKi exposed (196) and 81% were IDE naïve (n=263). Most common reasons for VEN dc were PD (38%), AE (20%), Richter's transformation (RT, 14%), 8% pt preference, and HSCT 5%. Of 326 pts who dc VEN, 188 (58%) were treated with a subsequent LOT, 61 are alive and untreated and 77 died prior to a subsequent LOT. Post VEN sequencing analyses focused on BTKi, PI3Ki and cellular therapy (CAR-T or alloHSCT) activities following VEN dc (Table1). ORR to BTKi was 84% (n=44) vs. 54% (n=30, p Conclusions: In the largest experience of therapies following VEN dc in CLL, we demonstrated that therapy selection following VEN requires consideration of prior novel agent exposure and reasons for discontinuation. For BTKi naïve pts, selection of a covalently binding BTKi results in high ORR and durable remissions. PFS-2 data provide reassurance for using VEN prior to IBR. For BTKi exposed pts, BTK inhibition is not effective in the setting of BTKi resistance but should be considered if prior BTKi intolerance. PI3K inhibition following VEN does not appear to result in durable remissions even in PI3Ki naïve pts, suggesting possible overlap in resistance mechanisms (BTK or VEN with PI3K). We conclude that BTKi in naïve or previously responsive pts and alloHSCT following VEN appear to be the most effective strategies with durable responses. These data suggest that a number of effective regimens exist for post VEN pts, providing support for VEN use earlier in the course of CLL. Disclosures Mato: Acerta: Consultancy; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Janssen: Consultancy; Gilead: Research Funding; Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Celgene: Consultancy. Roeker:AbbVie: Equity Ownership; Abbott Laboratories: Equity Ownership. Eyre:Gilead: Consultancy, Other: Research support, Speakers Bureau; Roche: Honoraria; Abbvie: Honoraria, Other: Travel to Conferences; Janssen: Honoraria, Other: Travel to Conferences ; Takeda: Other: Travel to Conferences . Jacobs:Pharmacyclics LLC, an AbbVie Company: Research Funding, Speakers Bureau; AstraZeneca: Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; JUNO: Consultancy; Gilead: Consultancy; TG Therapeutics: Honoraria, Research Funding. Hill:TG therapeutics: Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Research Funding; Kite: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Honoraria; Celegene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Takeda: Research Funding; Amgen: Research Funding. Lamanna:Celgene: Consultancy; Infinity/ Verastem: Research Funding; Ming: Research Funding; TG Therapeutics: Research Funding; Oncternal: Research Funding. Brander:Tolero: Research Funding; MEI: Research Funding; BeiGene: Research Funding; DTRM Biopharma: Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Research Funding; Novartis: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy; AbbVie: Consultancy, Honoraria, Research Funding; Acerta: Research Funding. Shadman:AbbVie: Consultancy, Research Funding; Astra Zeneca: Consultancy; BeiGene: Research Funding; TG Therapeutic: Research Funding; ADC Therapeutics: Consultancy; Atara Biotherapeutics: Consultancy; Verastem: Consultancy; Acerta Pharma: Research Funding; Sunesis: Research Funding; Mustang Bio: Research Funding; Celgene: Research Funding; Pharmacyclics: Consultancy, Research Funding; Sound Biologics: Consultancy; Genentech: Consultancy, Research Funding; Gilead: Consultancy, Research Funding. Ujjani:AstraZeneca: Consultancy; Genentech: Consultancy; Rigel: Consultancy; Gilead: Consultancy; Abbvie: Research Funding; Pharmacyclics: Research Funding. Perini:Janssen: Other: Advisory Board; Abbvie: Other: Advisory Board; AstraZeneca: Other: Advisory Board. Pinilla Ibarz:Sanofi: Speakers Bureau; Bayer: Speakers Bureau; Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; Takeda: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Teva: Consultancy; TG Therapeutics: Consultancy. Barrientos:Pharmacyclics: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Janssen: Consultancy; Gilead: Consultancy; Genentech: Consultancy. Skarbnik:Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Honoraria, Speakers Bureau; CLL Society: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Speakers Bureau; Novartis: Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Verastem Oncology: Honoraria, Research Funding, Speakers Bureau; Kite Pharma: Honoraria, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Acerta: Research Funding. Pagel:AstraZeneca: Consultancy; Gilead Sciences: Consultancy; Pharmacyclics: Consultancy. Choi:Abbvie: Consultancy, Research Funding, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy, Research Funding, Speakers Bureau; Rigel: Consultancy, Research Funding; Gilead: Consultancy, Speakers Bureau; Oncternal: Research Funding. Coombs:H3 Biomedicine: Research Funding. Barr:Janssen: Consultancy; Astra Zeneca: Consultancy, Research Funding; Merck: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Genentech: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Celgene: Consultancy; TG Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; AbbVie: Consultancy. Portell:Xencor: Research Funding; Roche/Genentech: Research Funding; Infinity: Research Funding; TG Therapeutics: Research Funding; AbbVie: Research Funding; Pharmacyclics: Consultancy; Janssen: Consultancy; Genentech: Consultancy, Research Funding; Amgen: Consultancy; Bayer: Consultancy; BeiGene: Consultancy, Research Funding; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding. Schuster:AstraZeneca: Honoraria; AbbVie: Honoraria, Research Funding; Acerta: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Loxo Oncology: Honoraria; Pfizer: Honoraria; Nordic Nanovector: Honoraria; Pharmacyclics: Honoraria, Research Funding; Novartis: Honoraria, Patents & Royalties: Combination Therapies of CAR and PD-1 Inhibitors with royalties paid to Novartis, Research Funding; Merck: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Gilead: Honoraria, Research Funding. Martinez-Calle:ABBVIE: Other: Travel support. Munir:AbbVie: Honoraria; Alexion: Honoraria; Gilead: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Roche: Honoraria; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sunesis: Consultancy; Pharmacyclics: Other: TBC; Acerta: Membership on an entity's Board of Directors or advisory committees. Nabhan:Aptitude Health: Employment. King:Astrazeneca: Other: Advisory board; Genentech: Other: Advisory Board ; Incyte: Other: Advisory Board. Zelenetz:Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cheson:Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Symbios: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Portola: Research Funding; Kite: Research Funding; Gilead: Research Funding; Epizyme: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding. Fox:Gilead: Consultancy; Janssen: Consultancy; Celgene: Consultancy; AbbVie: Consultancy; Sunesis: Consultancy; Takeda Pharmaceuticals: Consultancy; Atara Biotherapeutics: Consultancy; Adienne: Other: Travel Support. Allan:Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Janssen: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie company: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Consultancy.

Introduction: Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the Western world. Treatment selection in CLL is dependent upon a number of factors, such as patient age and genetic mutations, and can be challenging. A number of novel therapies and combination treatment approaches are now available, making treatment selection and management of adverse events increasingly complex. We sought to determine if a curriculum of online continuing professional education (CPE) activities could improve hematologists/oncologists (hem/onc, H/O), pathologists (path), nurse/NP, and pharmacist knowledge, competence, and confidence related to clinical decision making in patients with CLL. Methods: An expert panel identified educational gaps related to the treatment of patients with CLL. Based on the educational needs identified, the curriculum included 4 activities that were posted online between March 2019-June 2019. The first activity was a 30 minute video lecture (1 faculty) about measurable residual disease (MRD) analysis in CLL. The second activity was 30 minute video roundtable discussion (3 faculty) about treatment initiation and selection in newly diagnosed CLL. The third activity was a text activity focused on relapsed/refractory (R/R) CLL with 2 patient cases. The final activity was a video discussion between a nurse and pharmacist about mitigating side effects and optimizing compliance with oral therapies in CLL. Three activities were certified for physicians and the fourth activity was certified for nurses and pharmacists. Multiple-choice questions were asked before and after participation in each activity A repeated-pairs analysis was conducted where individual learners served as their own controls. Improved indicates an incorrect response pre-activity and a correct response post-activity. Reinforced indicates a correct answer pre- and post-activity. Improved confidence indicates a higher level of confidence post-activity. Results: As of July 2019, there were 356 hem/oncs, 154 pathologists, 178 nurses/NPs, and 504 pharmacists included in this analysis. The curriculum had a large impact on the knowledge and competence of hem/oncs and pathologists. MRD is an indicator of improved progression free survival: 13% H/O and path improved their knowledge, 58% H/O and 36% path reinforced their knowledge. The role for MRD measurement in CLL: 24% H/O and 15% of path improved their knowledge, 51% H/O and 39% path reinforced their knowledge. Selecting therapy for treatment-naïve CLL: 13% H/O and 30% path improved their competence, 57% H/O and 36% path reinforced their competence. Selecting therapy for relapsed/refractory (R/R) CLL: 39% H/O and 42% path improved their competence, 26% H/O and 11% path reinforced their competence. Managing treatment-related side effects in CLL: 11% H/O and 33% path improved their competence, 72% H/O and 31% path reinforced their competence. 10% of nurses/NPs and 11% of pharmacists improved and 30% of nurses/NPs and 38% of pharmacists reinforced their skills counseling patients about adverse event management and drug-drug interactions in R/R CLL. Tailoring frontline therapy in treatment-naïve CLL: 26% H/O and 15% path improved their confidence. Tailoring therapy in R/R CLL: 34% H/O and 31% path improved their confidence. Using MRD in CLL management: 31% H/O and 21% path improved their confidence. Improving patient engagement by using effective interprofessional communication: 25% nurses/NPs and 36% pharmacists improved their confidence. Conclusions: This analysis shows that an online CPE curriculum, utilizing many different formats (video, text, panel discussions) can improve and reinforce the knowledge, competence, and confidence of hem/oncs, pathologists, nurses/NPs, and pharmacists in multiple areas surrounding the treatment of patients with CLL. Results also suggest the following areas warrant further education: knowledge of the role for MRD in CLL management, individualizing therapy selection for treatment-naïve and R/R CLL, and managing treatment-related adverse events of CLL therapies. Acknowledgements: Sameer Bhagavatula contributed to data analysis for this research. Figure Disclosures Allan: Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Janssen: Consultancy, Honoraria; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta Pharma: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie company: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Awan:Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Janssen: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Gilead: Consultancy. Brander:AbbVie: Consultancy, Honoraria, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy; Tolero: Research Funding; DTRM Biopharma: Research Funding; BeiGene: Research Funding; MEI: Research Funding; Acerta: Research Funding; Novartis: Consultancy; Genentech: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Research Funding. Cohen:Genentech, Inc.: Consultancy, Research Funding; Janssen Pharmaceuticals: Consultancy; LAM Therapeutics: Research Funding; UNUM: Research Funding; Hutchison: Research Funding; Astra Zeneca: Research Funding; Lymphoma Research Foundation: Research Funding; ASH: Research Funding; Takeda Pharmaceuticals North America, Inc.: Research Funding; Gilead/Kite: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Bristol-Meyers Squibb Company: Research Funding. Barrientos:Pharmacyclics: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Janssen: Consultancy; Gilead: Consultancy; Genentech: Consultancy.

Background: Targeted inhibition of Bruton tyrosine kinase (BTK) has improved clinical outcomes for patients with chronic lymphocytic leukemia (CLL). Acalabrutinib is a highly selective, covalent BTK inhibitor. A recently completed phase 3 trial showed acalabrutinib improved progression-free survival (PFS) vs idelalisib or bendamustine + rituximab in relapsed/refractory (R/R) CLL patients (ASCEND: Ghia et al. EHA 2019;273259:LB2606). This is an updated analysis with extended follow-up of a phase 1-2 multicenter study (NCT02029443) in patients with R/R CLL/small lymphocytic lymphoma (SLL), to demonstrate the durability of response and long-term tolerability of acalabrutinib. Methods: Patients with CLL or SLL were eligible if they were R/R after ≥1 prior treatment. Eligible patients were ≥18 years of age with an Eastern Cooperative Oncology Group performance status (ECOG PS) ≤2. Oral acalabrutinib 100 mg was administered twice daily. All patients were treated until progressive disease or unacceptable toxicity occurred. Study endpoints included overall response rate (ORR), PFS, duration of response (DOR) and safety, with post hoc analysis of event-free survival (EFS). Response rates were based on the International Workshop on Chronic Lymphocytic Leukemia 2008 criteria (Hallek et al., 2008) with modification for lymphocytosis (Cheson et al., 2012). Nine patients had longitudinal peripheral blood mononuclear cell samples from pre-treatment baseline, during treatment and at progression analyzed for whole exome sequencing, to assess acquired mechanisms of treatment resistance. Results: In total, 134 patients with R/R CLL/SLL received ≥ 1 dose of acalabrutinib. The median age was 66 years (range, 42-85 years). Baseline characteristics included ECOG PS ≤1 (97%), bulky lymph nodes ≥5 cm (39%), unmutated immunoglobulin heavy chain variable region (IGHV; 73%), chromosome 17p13.1 deletion (23%), chromosome 11q22.3 deletion (18%), and complex karyotype (≥3 abnormalities; 35%). The median number of prior therapies was 2 (range, 1-13). Patients received acalabrutinib for a median of 41 months (range, 0.2-58 months). Most adverse events (AEs) were mild to moderate, and most commonly were diarrhea (52%), headache (46%), and upper respiratory tract infection (36%). Grade ≥3 AEs occurred in 66% of patients; most commonly (≥5% of patients) neutropenia (14%), pneumonia (11%), hypertension (7%), anemia (7%) and diarrhea (5%). AEs of interest included atrial fibrillation (7% all grades; 3% Grade ≥3) and major bleeding events (5% all grades; 3% Grade ≥3). Most patients (56%) remained on treatment. The most common reasons for discontinuing treatment were progressive disease (21%) and AEs (11%). AEs leading to discontinuation occurring in ≥1 patient included pneumonia (4 events), anemia, neutropenia, and thrombocytopenia (2 events each). The ORR (partial response with lymphocytosis or above) was 94% (95% confidence interval [CI]: 89-97%); with 4% of patients having complete response, 84% having partial response and 6% having partial response with lymphocytosis (Table). The median DOR, PFS and EFS were not reached; the estimated 42-month DOR was 61% (95% CI: 49-71%), PFS was 68% (95% CI: 59-76%) and EFS was 64% (95% CI: 54-71%). Responses were similar regardless of genomic features, including unmutated IGHV, chromosomal deletions and complex karyotype (Table). Upon relapse during acalabrutinib treatment, whole exome sequencing detected BTK mutations in 6 of 9 (67%) tested patients that were not detectable at baseline. Of the 6 patients with detectable BTK C481X mutations, 4 had expansion to high allele frequency of the BTK mutation at progression (up to 58%). In a longitudinal analysis of patients who had a sample after 6 months of treatment, the BTK mutation was not detectable. No PLCG2 gene mutations were detected using exome analysis in the 9 patients analyzed. Conclusions: These updated results confirm the earlier reports of acalabrutinib efficacy for the treatment of CLL and provide additional data on DOR and long-term tolerability. Reported AEs indicate a tolerable and consistent safety profile, with a low rate of major bleeding events. Genomic profiling in a small subset of patients indicated that acquired mutation of BTK was the most frequent mechanism of acalabrutinib resistance. Disclosures Furman: Genentech: Consultancy. Wierda:Loxo Oncology Inc.: Research Funding; Janssen: Research Funding; Xencor: Research Funding; Cyclcel: Research Funding; Oncternal Therapeutics Inc.: Research Funding; Miragen: Research Funding; Sunesis: Research Funding; KITE pharma: Research Funding; Juno Therapeutics: Research Funding; Gilead Sciences: Research Funding; Acerta Pharma Inc: Research Funding; Pharmacyclics LLC: Research Funding; Genentech: Research Funding; AbbVie: Research Funding; GSK/Novartis: Research Funding. Schuh:Roche: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Gilead: Consultancy, Honoraria. Devereux:Servier: Speakers Bureau; Roche: Consultancy, Other: Travel expenses, Speakers Bureau; GlaxoSmithKline: Consultancy; Gilead: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; MSD: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau. Brown:Pfizer: Consultancy; Sun: Research Funding; Verastem: Consultancy, Research Funding; TG Therapeutics: Consultancy; Teva: Honoraria; Sunesis: Consultancy; Pharmacyclics: Consultancy; Morphosys: Other: Data safety monitoring boards ; Sun Pharmaceuticals, Inc: Research Funding; Acerta Pharma: Consultancy; AstraZeneca: Consultancy; BeiGene: Consultancy; Catapult Therapeutics: Consultancy; Dynamo Therapeutics: Consultancy; Genentech/Roche: Consultancy; Gilead: Consultancy, Research Funding; Invectys: Other: other; Janssen: Honoraria; Kite: Consultancy, Research Funding; Loxo: Consultancy, Research Funding; Novartis: Consultancy; Octapharma: Consultancy. Hillmen:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding; Roche: Research Funding; Gilead: Research Funding; Apellis: Research Funding; Acerta: Membership on an entity's Board of Directors or advisory committees. Martin:Karyopharm: Consultancy; Teneobio: Consultancy; Celgene: Consultancy; I-MAB: Consultancy; Sandoz: Consultancy; Janssen: Consultancy. Awan:Sunesis: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; Innate Pharma: Research Funding; Gilead: Consultancy; Janssen: Consultancy; Abbvie: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy, Research Funding. Stephens:Acerta: Research Funding; Gilead: Research Funding; Karyopharm: Research Funding. Ghia:Sunesis: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; ArQule: Consultancy, Honoraria; BeiGene: Consultancy, Honoraria; Dynamo: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Juno/Celgene: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Acerta/AstraZeneca: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy. Barrientos:Bayer: Consultancy; AstraZeneca: Consultancy; AbbVie: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Genentech: Consultancy; Gilead: Consultancy; Janssen: Honoraria; Sandoz: Consultancy; Oncternal Therapeutics: Research Funding. Pagel:AstraZeneca: Consultancy; Gilead Sciences: Consultancy; Pharmacyclics: Consultancy. Woyach:Janssen: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; AbbVie: Research Funding; Karyopharm: Research Funding; Loxo: Research Funding; Morphosys: Research Funding; Verastem: Research Funding. Burke:AstraZeneca: Employment, Equity Ownership. Covey:Acerta Pharma: Employment, Equity Ownership; AstraZeneca: Equity Ownership. Gulrajani:AstraZeneca: Equity Ownership; Acerta Pharma: Employment, Equity Ownership. Hamdy:Acerta Pharma: Employment, Equity Ownership. Izumi:Acerta Pharma: Employment, Equity Ownership. Frigault:Acerta Pharma: Employment; AstraZeneca: Employment, Equity Ownership. Patel:Acerta Pharma: Employment, Equity Ownership. Rothbaum:Acerta Pharma: Employment, Equity Ownership. Wang:AstraZeneca: Equity Ownership; Acerta Pharma: Employment. O'Brien:Eisai: Consultancy; Celgene: Consultancy; TG Therapeutics: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Gilead: Consultancy, Research Funding; Verastem: Consultancy; Vaniam Group LLC: Consultancy; Astellas: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Acerta: Research Funding; Alexion: Consultancy; Amgen: Consultancy; Aptose Biosciences, Inc: Consultancy; Regeneron: Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Janssen: Consultancy, Honoraria; Kite: Research Funding. Byrd:Ohio State University: Patents & Royalties: OSU-2S; BeiGene: Research Funding; Acerta: Research Funding; Genentech: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Acerta: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; Genentech: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau. OffLabel Disclosure: This is a Phase 1/2 investigational study of acalabrutinib in chronic lymphocytic leukemia

Bruton's tyrosine kinases inhibitors (BTKis) represent major advances in CLL therapy. However resistance to this form of therapy is emerging, and such patients often progress more rapidly. Hence there is an important need for therapies that address resistance. Microenvironmental input like IL-4 is critical for CLL disease progression. Compared with normal B cells, CLL cells exhibit significantly higher levels of surface membrane (sm) IL-4 receptor (IL4-R) and contain increased amounts of pSTAT6, a downstream mediator of IL-4R signaling. IL-4 stimulation of CLL B cells suppresses smCXCR4 and increases smIgM, thus promotes CLL cell retention and expansion. In this study, we aimed to examine if smIL-4R expression, IL4R signaling, and IL-4-producing cells are altered in patients sensitive or resistant to BTKis. To do so, T and B cell subset changes were studied overtime in 12 acalabrutinib-treated CLL patients, 6 zanubrutinib-treated CLL patients, 30 ibrutinib-sensitive and 5 ibrutinib-resistant CLL patients, 4 of which exhibited BTK mutations. Consistent with only ibrutinib inhibiting T-cell kinase (ITK), T-cell subset analyses revealed no changes in Th1, Th2, Th17, Th9, and Th22 cells after zanubrutinib or acalabrutinib treatment. In contrast, a Th1-biased T-cell immunity was observed in patients responsive to ibrutinib. In patients progressing on ibrutinib, significantly reduced Th2 T cells were found during the resistant as well as sensitive periods. In an in vitro T-cell function assay using T cells collected before and after the treatment with each BTKi, only ibrutinib treated patients exhibited a reduced ability of T cells to support CLL B cell survival. We next studied changes in CLL B cells, including numbers of IL-4, -10 and -13 producing B cells after BTKi treatment. IL-13 producing CLL B cells were not changed. IL-10 producing CLL B cells were reduced in both ibrutinib sensitive and resistant patients, but not in zanubrutinib or acalabrutinib treated patients. Importantly, IL-4 producing CLL B cells were significantly decreased in patients treated with all 3 BTKi. Significantly reduced smIL-4R levels, impaired IL-4R signaling, decreased smIgM and increased smCXCR4 were also seen in patients treated with each BTKi. To understand the mechanism responsible for inhibition of IL-4 production in CLL cells treated with BTKis, we stimulated CLL cells through IgM, Toll-like receptor and CD40L, finding that only anti-IgM stimulation significantly increased IL-4 production and p-STAT6 induction. We then explored the function of IL-4. IL-4 enhanced CLL B cell survival in vitro and this action was blocked by all 3 BTKis. Moreover, adhesion of CLL B cells to smIL-4R expressing stromal cells was decreased by IL-4 and IL-4R neutralizing antibodies, especially in M-CLL cases. In in vivo studies transferring autologous T cells and CLL PBMCs into alymphoid mice, we found less CLL B cells in mouse spleens post ibrutinib than zanubrutinib or acalabrutinib treatment. This might be due to the suppressed Th2 cells found only in ibrutinib, while IL-4 producing B cells were reduced in all 3 BTKi treated mice. These results support the idea that IL-4 promotes CLL B cell adhesion and growth in tissues. Finally, we investigated the IL-4/IL-4R axis in ibrutinib-resistant patients. Although IL-4 producing T cells remain reduced during the sensitive and resistant phases, CLL B cell production of IL-4 and expression of and signaling through smIL-4R returned when patients developed ibrutinib-resistance. When comparing paired ibrutinib-sensitive and -resistant CLL B cells collected from 3 patients in a xenograft model that requires T cell help, we found ibrutinib-resistant CLL B cells grew in vivo with only minimal (~15%) numbers of autologous T cells compared to B cells collected from ibrutinib-sensitive phase; this suggested a reduced requirement for T-cell help for growth of ibrutinib-resistant CLL cells. In summary, we found IL-4 is a key survival factor in the CLL microenvironment that also improves leukemia cell adhesion to stromal cells expressing smIL-4R. IL-4 production and signaling can be stimulated in CLL B cells through the B-cell receptor, and are consistently blocked by BTKis. Moreover, the recovered ability of ibrutinib-resistant CLL B cells to produce and respond to IL-4 leads to disease progression, suggesting blocking the IL-4/IL-4R axis is a potential treatment for ibrutinib-resistant CLL patients. Disclosures Chen: Pharmacyclics: Research Funding; Beigene: Research Funding; Verastem: Research Funding; ArgenX: Research Funding. Tam:Abbvie, Janssen: Research Funding; Abbvie, Janssen, Beigene, Roche, Novartis: Honoraria. Ramsay:Celgene Corporation: Research Funding; Roche Glycart AG: Research Funding. Kolitz:Boeringer-Ingelheim: Research Funding; Roche: Research Funding; Astellas: Research Funding. Zhou:BeiGene: Employment. Barrientos:Genentech: Consultancy; Gilead: Consultancy; Janssen: Consultancy; Abbvie: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding. Rai:Pharmacyctics: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Cellectis: Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees.

Malignant cell growth within patients with B cell chronic lymphocytic leukemia (B-CLL) is largely restricted to lymphoid tissues, particularly lymph nodes. The recent in vitro finding that TLR-9 ligand (oligodeoxynucleotide [ODN]) and IL-15 exhibit strong synergy in promoting B-CLL growth may be particularly relevant to growth in these sites. This study shows IL-15–producing cells are prevalent within B-CLL–infiltrated lymph nodes and, using purified B-CLL cells from blood, investigates the mechanism for ODN and IL-15 synergy in driving B-CLL growth. ODN boosts baseline levels of phospho-RelA(S529) in B-CLL and promotes NF-κB–driven increases in IL15RA and IL2RB mRNA, followed by elevated IL-15Rα and IL-2/IL-15Rβ (CD122) protein. IL-15→CD122 signaling during a critical interval, 20 to 36–48 h following initial ODN exposure, is required for optimal induction of the cycling process. Furthermore, experiments with neutralizing anti–IL-15 and anti-CD122 mAbs indicate that clonal expansion requires continued IL-15/CD122 signaling during cycling. The latter is consistent with evidence of heightened IL2RB mRNA in the fraction of recently proliferated B-CLL cells within patient peripheral blood. Compromised ODN+IL-15 growth with limited cell density is consistent with a role for upregulated IL-15Rα in facilitating homotypic trans IL-15 signaling, although there may be other explanations. Together, the findings show that ODN and IL-15 elicit temporally distinct signals that function in a coordinated manner to drive B-CLL clonal expansion.

Clinical progression of B cell chronic lymphocytic leukemia (B-CLL) reflects the clone’s Ag receptor (BCR) and involves stroma-dependent B-CLL growth within lymphoid tissue. Uniformly elevated expression of TLR-9, occasional MYD88 mutations, and BCR specificity for DNA or Ags physically linked to DNA together suggest that TLR-9 signaling is important in driving B-CLL growth in patients. Nevertheless, reports of apoptosis after B-CLL exposure to CpG oligodeoxynucleotide (ODN) raised questions about a central role for TLR-9. Because normal memory B cells proliferate vigorously to ODN+IL-15, a cytokine found in stromal cells of bone marrow, lymph nodes, and spleen, we examined whether this was true for B-CLL cells. Through a CFSE-based assay for quantitatively monitoring in vitro clonal proliferation/survival, we show that IL-15 precludes TLR-9–induced apoptosis and permits significant B-CLL clonal expansion regardless of the clone’s BCR mutation status. A robust response to ODN+IL-15 was positively linked to presence of chromosomal anomalies (trisomy-12 or ataxia telangiectasia mutated anomaly + del13q14) and negatively linked to a very high proportion of CD38+ cells within the blood-derived B-CLL population. Furthermore, a clone’s intrinsic potential for in vitro growth correlated directly with doubling time in blood, in the case of B-CLL with Ig H chain V region–unmutated BCR and

The two major subtypes of diffuse large B cell lymphoma (DLBCL)—activated B cell–like (ABC) and germinal center B cell–like (GCB)—arise by distinct mechanisms, with ABC selectively acquiring mutations that target the B cell receptor (BCR), fostering chronic active BCR signaling(1). The ABC subtype has a ∼40% cure rate with currently available therapies, which is worse than the rate for GCB DLBCL, and highlights the need for ABC subtype-specific treatment strategies(2). We hypothesized that ABC, but not GCB, DLBCL tumors would respond to ibrutinib, an inhibitor of BCR signaling. In a phase 1/2 clinical trial that involved 80 subjects with relapsed or refractory DLBCL, ibrutinib produced complete or partial responses in 37% (14/38) of those with ABC DLBCL, but in only 5% (1/20) of subjects with GCB DLBCL (P = 0.0106). ABC tumors with BCR mutations responded to ibrutinib frequently (5/9; 55.5%), especially those with concomitant myeloid differentiation primary response 88 (MYD88) mutations (4/5; 80%), a result that is consistent with in vitro cooperation between the BCR and MYD88 pathways. However, the highest number of responses occurred in ABC tumors that lacked BCR mutations (9/29; 31%), suggesting that oncogenic BCR signaling in ABC does not require BCR mutations and might be initiated by non-genetic mechanisms. These results support the selective development of ibrutinib for the treatment of ABC DLBCL.

Hairy cell leukemia is an uncommon hematologic malignancy characterized by pancytopenia and marked susceptibility to infection. Tremendous progress in the management of patients with this disease has resulted in high response rates and improved survival, yet relapse and an appropriate approach to re-treatment present continuing areas for research. The disease and its effective treatment are associated with immunosuppression. Because more patients are being treated with alternative programs, comparison of results will require general agreement on definitions of response, relapse, and methods of determining minimal residual disease. The development of internationally accepted, reproducible criteria is of paramount importance in evaluating and comparing clinical trials to provide optimal care. Despite the success achieved in managing these patients, continued participation in available clinical trials in the first-line and particularly in the relapse setting is highly recommended. The Hairy Cell Leukemia Foundation convened an international conference to provide common definitions and structure to guide current management. There is substantial opportunity for continued research in this disease. In addition to the importance of optimizing the prevention and management of the serious risk of infection, organized evaluations of minimal residual disease and treatment at relapse offer ample opportunities for clinical research. Finally, a scholarly evaluation of quality of life in the increasing number of survivors of this now manageable chronic illness merits further study. The development of consensus guidelines for this disease offers a framework for continued enhancement of the outcome for patients.

It is an unprecedented time for the treatment of patients with chronic lymphocytic leukemia (CLL) with the recent approval of several targeted agents for use in frontline, relapsed, refractory, and high-risk disease. Traditionally, frontline management of CLL has been a combination of chemotherapy (fludarabine, cyclophosphamide, bendamustine, or chlorambucil) with an anti-CD20 monoclonal antibody (rituximab, ofatumumab, obinutuzumab). The current landscape is rapidly evolving with the advent of therapies that demonstrate selective inhibition of important pathways necessary for CLL proliferation and survival. Despite considerable progress, much is still unknown and optimal treatment selection and sequence is still debatable. None of the new agents have been compared against each other and the impact of adding an additional agent to monotherapy is not yet fully elucidated. In routine clinical practice, the choice of therapy is based on nonrandomized comparisons, presence of comorbidities, and toxicity considerations. These recently approved drugs (ibrutinib, idelalisib, and venetoclax) are reporting excellent outcomes, including patients with high-risk disease such as 17p deletion (17p−) or TP53 mutations (TP53mut). Ibrutinib and venetoclax have been approved for use in 17p− patients (frontline and relapsed, respectively). Ibrutinib is currently moving into the frontline space given recent regulatory approvals. This review will summarize and interpret the limited therapeutic sequencing data available, highlighting the need for additional studies to optimize combination strategies and treatments after failure or discontinuation of these novel agents.

Background: Bruton tyrosine kinase (BTK) is a critical component of B-cell receptor signaling pathway and a validated therapeutic target for CLL. Acalabrutinib is a highly selective, potent, covalent BTK inhibitor with minimal off-target activity that has been shown to have an overall response rate (ORR) of 95% (85% partial response [PR]; 10% PR with lymphocytosis [PRL]) after a median follow-up of 14.3 months in the relapsed CLL cohort of the Phase 1/2 ACE-CL-001 study. We present an updated analysis of the safety and efficacy results from the TN cohort of CLL patients from ACE-CL-001. Methods: Patients with TN CLL/small lymphocytic lymphoma (SLL) were eligible if they met International Workshop on Chronic Lymphocytic Leukemia (IWCLL) 2008 criteria for treatment, had an ECOG performance status of ≤2, and declined or were not appropriate candidates for chemotherapy. Patients received oral acalabrutinib 100 mg twice daily (BID) or 200 mg daily (patients were started on 200 mg QD and then switched to 100 mg BID) until progressive disease or unacceptable toxicity. Safety was the primary endpoint. Secondary endpoints were investigator-assessed overall response rate (ORR) by IWCLL 2008 criteria with modification for lymphocytosis, duration of response (DOR) and progression-free survival (PFS). Time to response (TTR; ≥ PR) and event-free survival (EFS) were exploratory endpoints. Results: A total of 99 patients (100 mg BID, n=62; 200 mg QD, n=37) were treated. The median age was 64 years (range 33-85), 46% of patients had bulky lymph nodes ≥5 cm, 47% had Rai stage III-IV disease at baseline, 10% (9/91) of patients had del(17p), and 62% (57/92) of patients had unmutated IGHV. As of December 1, 2017, the median time on study was 33 (1-39) months, with 91% of patients remaining on study treatment. Nine patients discontinued therapy: adverse events (n=5; 5%), pregnancy, disease progression, patient withdrawal, and initiation of subsequent therapy (n=1 each; 1%). The most common AEs (all grades; >20% of patients) were diarrhea (47%), headache (44%), contusion (34%), upper respiratory tract infection (33%), weight increase (30%), arthralgia (29%), nausea (26%), and cough (23%); the majority of these most common AEs were Grade 1/2. Grade 3/4 AEs occurred in 49% (49/99) of patients, most commonly (>2% of patients) neutropenia (7%), diarrhea (5%), headache (5%), nausea (4%), pneumonia (4%), hypertension (3%), and syncope (3%). Atrial fibrillation and hypertension (all grades vs grade 3/4) occurred in 6% vs 1% of patients and 14% vs 3% of patients, respectively. The most common bleeding events (>15%) were contusion (34%), petechiae (18%), and ecchymosis (16%); all bleeding events (60%) were Grade 1/2 except for 2 Grade 3 events (hematuria, upper gastrointestinal hemorrhage). Approximately 34% (34/99) of patients reported serious AEs (all grades), most commonly (≥5 patients) infection (pneumonia [4 patients], influenza [2 patients], and sinusitis [2 patients]). One grade 5 event (multiorgan failure due to neutropenic sepsis/pneumonia) was reported, which was considered unrelated to acalabrutinib. AEs leading to treatment discontinuation (5%) were secondary malignancies (angiosarcoma, glioblastoma multiforme, small cell lung cancer), neutropenic sepsis (Grade 2), rash (Grade 3), and urinary tract infection (Grade 3). ORR was high (97%) for this patient cohort (Table). Median DOR for the 96 responders (≥ PR) and median PFS for the 99 treated patients were not reached (NR) (95% CI: NR, NR; Figure 1). The 36-month DOR and PFS rate was 99% (95% CI: 91%, 100%) and 98% (95% CI: 92%, 100%), respectively. The EFS (with events defined as progression, death, discontinuation due to AE, or start of new anticancer therapy) was estimated to be 94.9% (95% CI: 88.2%, 97.9%) at 24 months (Figure 2). Median TTR was 3.7 months (range 2-22). For the 5 patients who achieved complete response (CR), the median time to CR was 28 months. One CLL progression was reported. No Richter's transformation occurred. Conclusion: Acalabrutinib monotherapy produced high response rates and demonstrated an acceptable safety profile in patients with TN CLL. Disclosures Furman: Gilead: Consultancy; Loxo Oncology: Consultancy; Acerta: Consultancy, Research Funding; Genentech: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy; Verastem: Consultancy; Incyte: Consultancy, Other: DSMB; Janssen: Consultancy; AbbVie: Consultancy. Martin:Gilead: Consultancy; Janssen: Consultancy; Bayer: Consultancy; Seattle Genetics: Consultancy; AstraZeneca: Consultancy; Kite: Consultancy. O'Brien:Janssen: Consultancy; GlaxoSmithKline: Consultancy; Acerta: Research Funding; Pfizer: Consultancy, Research Funding; Alexion: Consultancy; Pharmacyclics: Consultancy, Research Funding; Amgen: Consultancy; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; Vaniam Group LLC: Consultancy; Astellas: Consultancy; Abbvie: Consultancy; Aptose Biosciences Inc.: Consultancy; Gilead: Consultancy, Research Funding; Kite Pharma: Research Funding; Regeneron: Research Funding; TG Therapeutics: Consultancy, Research Funding. Brown:Celgene: Consultancy; Verastem: Consultancy, Research Funding; Janssen: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Boehringer: Consultancy; Sun Pharmaceutical Industries: Research Funding; Gilead: Consultancy, Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy; Beigene: Membership on an entity's Board of Directors or advisory committees; Acerta / Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy; TG Therapeutics: Consultancy; Roche/Genentech: Consultancy; Invectys: Membership on an entity's Board of Directors or advisory committees; Loxo: Consultancy. Barrientos:Pharmacyclics/Abbive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees. Devereux:Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Other: Personal fees. Hillmen:Novartis: Research Funding; Pharmacyclics: Research Funding; Celgene: Research Funding; Alexion Pharmaceuticals, Inc: Consultancy, Honoraria; Acerta: Membership on an entity's Board of Directors or advisory committees; F. Hoffmann-La Roche Ltd: Research Funding; Gilead Sciences, Inc.: Honoraria, Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Pagel:Gilead: Consultancy; Pharmacyclics, an AbbVie Company: Consultancy. Chen:Acerta Pharma: Employment. Hamdy:Acerta Pharma: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: various patents for ACP-196. Izumi:Acerta Pharma: Employment, Equity Ownership, Patents & Royalties: Acerta Pharma, various patents for ACP-196. Patel:Acerta Pharma: Employment, Equity Ownership. Wang:Acerta Pharma: Employment. Jain:Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; Pfizer: Research Funding; Abbvie: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Infinity: Research Funding; Incyte: Research Funding; BMS: Research Funding; ADC Therapeutics: Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Research Funding; BMS: Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; Infinity: Research Funding; Pfizer: Research Funding; Celgene: Research Funding; ADC Therapeutics: Research Funding; Astra Zeneca: Research Funding; Seattle Genetics: Research Funding; Servier: Research Funding; Verastem: Research Funding; Incyte: Research Funding; Cellectis: Research Funding; Celgene: Research Funding; Adaptive Biotechnologioes: Research Funding; Astra Zeneca: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Research Funding; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cellectis: Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologioes: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees. Wierda:AbbVie, Inc: Research Funding; Genentech: Research Funding.

Novel agents targeting the B-cell receptor signaling pathway, such as ibrutinib and idelalisib, are effective in patients with chronic lymphocytic leukemia (CLL), but complete responses are infrequent and residual disease often remains. Patients may discontinue ibrutinib because of unacceptable adverse events or if they develop ibrutinib resistance due to Bruton tyrosine kinase (BTK) or phospholipase C gamma 2 (PLCG2) mutations or other less-well-defined mechanisms. Therefore, alternative therapies that can overcome ibrutinib intolerance and resistance are needed. Duvelisib (DUV) is an oral dual phosphatidylinositol 3-kinase (PI3K)-δ and -γ inhibitor with activity in patients with relapsed/refractory CLL and a manageable safety profile. Preclinical studies point to distinct roles of PI3K-δ and -γ in CLL biology, suggesting that dual isoform inhibition may enhance efficacy by targeting both CLL and CLL-supporting cells. Importantly, DUV potently inhibits PI3K-δ and -γ in human peripheral blood mononuclear cells and CLL cells. Here, we further characterize the distinct functions of PI3K-δ and -γ in CLL and examine the mechanisms of action of DUV in vitro and in a patient-derived xenograft (PDX) model, highlighting the ability of DUV to overcome ibrutinib resistance. We first assessed the in vivo efficacy of PI3K-δ and/or PI3K-γ inhibition on CLL B cells using a PDX mouse model in which activated patient-derived T cells and CLL B cells were injected into alymphoid NOD-scid IL-2Rγnull (NSG) mice. Cells from 4 patients were transferred and allowed to expand for 2 weeks, after which mice were treated with DUV, a PI3K-δ inhibitor, or a PI3K-γ inhibitor for 3 weeks. DUV and the PI3K-δ inhibitor, but not the PI3K-γ inhibitor, significantly decreased the number of CLL B cells in the spleens of mice. In another set of experiments, combination treatment with the PI3K-δ and -γ inhibitors more potently impaired CLL B-cell survival than the PI3K-δ inhibitor alone. Next, the effects of PI3K-δ or -γ inhibition on CLL-supporting cells, ie, autologous T cells and murine macrophages, were examined in the PDX model using the same 4 patient samples. Significant decreases in both patient-derived T cells and murine macrophages were observed in the spleens of mice treated with DUV or the PI3K-γ inhibitor but not with the PI3K-δ inhibitor. Therefore, the function of PI3K-δ and -γ in macrophages and macrophage-supported CLL cell survival were examined in vitro. Murine bone marrow-derived macrophages were polarized via interleukin 4 and macrophage colony stimulating factor in the presence of DUV, a PI3K-δ inhibitor, or a PI3K-γ inhibitor. Both DUV and the PI3K-γ inhibitor impaired M2 polarization, assessed by arginase 1 (ARG1) mRNA expression. Culture with M2 macrophages increased CLL B-cell viability, and the addition of DUV inhibited this survival-promoting activity more than the PI3K-δ or -γ inhibitors alone. To assess whether DUV could inhibit CLL B cells from ibrutinib-unresponsive patients, activated T cells and CLL B cells from 2 patients who progressed on ibrutinib (1 with a BTK C481S mutation and 1 without a BTK mutation) were transferred into NSG mice and allowed to expand for 2 weeks, and then mice were treated with DUV or ibrutinib for 3 weeks. For both patient samples, there was a > 10-fold reduction in the number of CLL B cells recovered from the spleens of mice treated with DUV, as well as a significant reduction in the percentage of proliferating CLL B cells. In contrast, ibrutinib did not have significant impact on CLL B-cell numbers or proliferation in the spleen. In conclusion, DUV inhibits the in vivo survival and proliferation of leukemic B cells from CLL patients, including those who have progressed on ibrutinib. Dual PI3K-δ and -γ inhibition is more effective at inhibiting CLL B cells in vivo than PI3K-δ inhibition alone. Moreover, PI3K-γ inhibition shifts macrophage polarization away from a CLL-supportive M2 phenotype. Thus, DUV exerts inhibitory effects on CLL B cells and on CLL-supporting T and myeloid cells. Overall, these findings elucidate the non-redundant roles of PI3K-δ and -γ in CLL and demonstrate the potent antitumor activity of dual PI3K isoform inhibition by DUV in ibrutinib-resistant patient CLL cells in vivo. Further investigation of DUV as a therapeutic option for patients who are refractory to or intolerant of ibrutinib or other BTK inhibitors is ongoing in a phase 2 clinical trial (BRIO; NCT03370185). Disclosures Chen: Janssen: Research Funding; ArgenX: Research Funding; Beigene: Research Funding; Pharmacyclics: Research Funding; Verastem: Research Funding. Kutok:Infinity Pharmaceuticals: Employment, Equity Ownership. Barrientos:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Weaver:Verastem Oncology: Employment, Other: Stockholder; Agios Pharmaceuticals: Employment; Femto Dx: Equity Ownership. Pachter:Verastem: Employment, Other: Stockholder. Rai:Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Membership on an entity's Board of Directors or advisory committees; Cellectis: Membership on an entity's Board of Directors or advisory committees. Chiorazzi:AR Pharma: Equity Ownership; Janssen, Inc: Consultancy.

BACKGROUND: Chronic lymphocytic leukemia (CLL) is one of the most common lymphoid malignancies, accounting for ~11% of all hematologic neoplasms. Over the last 15 years, a series of phase 3 trials have established that chemoimmunotherapy (CIT) with fludarabine, cyclophosphamide, and rituximab (FCR) improves both progression free survival (PFS) and overall survival (OS) compared with chemotherapy alone. FCR is the gold standard for young fit patients with treatment naïve CLL. In parallel with the advances in CIT, a profound increase in the understanding of CLL B-cell biology led to new therapeutic approaches.1 Among these, ibrutinib (an irreversible inhibitor of Bruton's Tyrosine Kinase [BTK]) has had the largest impact on clinical practice to date. Initial trials of ibrutinib demonstrated robust and durable efficacy in patients with relapsed/refractory disease. Subsequent phase 3 trials showed improved PFS and OS with ibrutinib relative to chlorambucil in previously untreated, older CLL patients. Despite these advances, the efficacy of ibrutinib as a first-line treatment for younger CLL patients (i.e. METHODS: Eligible patients were treatment-naive individuals with CLL who were age Hematologic toxicity was graded according to the 2008 IWCLL Working Group scale. All other adverse events were graded according to the NCI Common Toxicity Criteria (version 4). The primary endpoint was PFS with a secondary endpoint of overall survival (OS). Analysis was by intention to treat. The first planed interim analysis for PFS was scheduled to occur 24-27 months after full accrual with the first interim analysis for OS scheduled to occur if the boundary for PFS was crossed. The primary analysis was a stratified logrank test applied to all patients as randomized. Treatment effect p-values are one-sided. The study was approved by the Central Institutional Review Board for the National Cancer Institute, conducted in accordance with the principles of the Declaration of Helsinki, and registered with ClinicalTrials.gov (NCT02048813). RESULTS: A total of 529 patients were accrued between January 31, 2014 and June 9, 2016. 354 patients were assigned to ibrutinib and rituximab (IR) and 175 to FCR. Nineteen patients did not start protocol therapy. The first interim analysis was performed September 2018. With median follow-up of 33.4 months, we observed 77 PFS events and 14 deaths. The hazard ratio (HR) for PFS favored IR over FCR (HR=0.352; 95% CI 0.223-0.558; p In subgroup analysis for PFS, IR was superior to FCR independent of age, sex, performance status, disease stage or the presence/absence of del11q23. With current follow-up, IR was also superior to FCR for IGHV unmutated patients (HR=0.262; 95% CI 0.137-0.498; p Grade 3 and 4 treatment-related adverse events were observed in 58% of IR and 72% of FCR treated patients (p=0.0042). Specifically, FCR was more frequently associated with grade 3 and 4 neutropenia (FCR: 69 [44%] of 158 vs. IR: 80 [23%] of 352; p CONCLUSIONS: The combination of ibrutinib and rituximab provides superior PFS and OS relative to FCR for patients with previously untreated CLL age Disclosures Shanafelt: Mayo Clinic: Patents & Royalties: Physician Well-being Index, Medical Student Well-being Index, Well-being index; Celgene: Research Funding; GlaxoSmithKline: Research Funding; Genentech: Research Funding; Abbvie: Research Funding; Pharmacyclics: Research Funding; Janssen: Research Funding. Kay:Janssen: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Cytomx Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Infinity Pharm: Membership on an entity's Board of Directors or advisory committees. O'Brien:Amgen: Consultancy; Astellas: Consultancy; Celgene: Consultancy; GlaxoSmithKline: Consultancy; Janssen: Consultancy; Aptose Biosciences Inc.: Consultancy; Vaniam Group LLC: Consultancy; Abbvie: Consultancy; Alexion: Consultancy; Kite Pharma: Research Funding; Regeneron: Research Funding; Acerta: Research Funding; Gilead: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding. Barrientos:Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Erba:Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy, Other: grant; Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy, Other: grant; Pfizer: Consultancy, Other: grant; Incyte: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Astellas: Research Funding; Janssen: Research Funding; Janssen: Research Funding; Amgen: Research Funding; Amgen: Research Funding; Novartis: Consultancy, Speakers Bureau; Astellas: Research Funding; Incyte: Consultancy, Speakers Bureau; Astellas: Research Funding; Pfizer: Consultancy, Other: grant; Novartis: Consultancy, Speakers Bureau; Juno: Research Funding; Juno: Research Funding; Novartis: Consultancy, Speakers Bureau; MacroGenics: Consultancy; MacroGenics: Consultancy; Amgen: Research Funding; Takeda/Millenium: Research Funding; Amgen: Research Funding; Takeda/Millenium: Research Funding; Seattle Genetics: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Celgene: Consultancy, Speakers Bureau; Takeda/Millenium: Research Funding; Immunogen: Consultancy, Research Funding; Takeda/Millenium: Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Celgene: Consultancy, Speakers Bureau; MacroGenics: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; MacroGenics: Consultancy; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Daiichi Sankyo: Consultancy, Research Funding; Juno: Research Funding; Juno: Research Funding; Agios: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Celgene: Consultancy, Speakers Bureau; Daiichi Sankyo: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Daiichi Sankyo: Consultancy, Research Funding. Stone:Juno: Consultancy; Macrogenics: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; FujiFilm: Consultancy; Sumitomo: Consultancy; Ono/Theradex: Consultancy; Otzuka/Astex: Consultancy; Pfizer: Consultancy; Roche: Consultancy; AbbVie: Consultancy, Research Funding; Actinium: Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Argenx: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy, Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy; Celator / Jazz: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cornerstone: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Tallman:ADC Therapeutics: Research Funding; Daiichi-Sankyo: Other: Advisory board; BioSight: Other: Advisory board; AbbVie: Research Funding; Cellerant: Research Funding; AROG: Research Funding; Orsenix: Other: Advisory board.