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Complex karyotype, defined as ≥3 cytogenetic abnormalities, is prognostic of survival in patients treated with ibrutinib or venetoclax in relapsed/refractory (RR) chronic lymphocytic leukemia (CLL). Recent studies re-evaluating this dichotomous variable have shown that higher numbers of cytogenetic abnormalities (ie, ≥5) have a worse overall survival in patients treated with chemoimmunotherapy. We sought to determine if increasing karyotypic complexity, treated as a continuous variable, was prognostic of survival for patients treated with ibrutinib for CLL. We conducted a retrospective analysis of all patients with CLL treated with single-agent ibrutinib or in combination with an anti–CD20 antibody at our institution. We included 456 patients with both treatment-naive and RR disease. Median number of prior therapies was 2 (range, 0-13), 30% of patients had presence of del(17p), and 75% expressed unmutated IGHV. Fifty percent had ≥3 cytogenetic abnormalities, including 30% with ≥5. In a multivariable analysis, increasing karyotypic complexity was an independent predictor of shorter progression-free survival (hazard ratio, 1.07; 95% confidence interval, 1.04-1.10; P < .0001) and overall survival (hazard ratio, 1.09; 95% confidence interval, 1.05-1.12; P < .0001). Furthermore, we found that presence of clonal evolution determined by cytogenetic analysis at progression was prognostic of subsequent survival (P = .02). This solidifies karyotypic complexity as an important prognostic factor for patients with CLL treated with ibrutinib. Further research should consider sequential karyotypic analysis as a determination of risk of progression and death in patients with CLL.

The management of chronic lymphocytic leukemia (CLL) has undergone unprecedented changes over the last decade. Modern targeted therapies are incorporated into clinical practice. Unfortunately, patients have begun to develop resistance or intolerance to multiple classes. Symptomatic patients previously treated with a BTK inhibitor (BTKi) and venetoclax represent a new and rapidly growing unmet need in CLL. Here, we define unmet needs in a modern treatment context. We also critically review the literature for PI3K inhibitors and chemoimmunotherapy and lack of data to support their utility following BTKis and venetoclax. Finally, we suggest opportunities to ensure the continued innovation for patients with CLL.

PURPOSE The development of highly effective targeted agents for chronic lymphocytic leukemia offers the potential for fixed-duration combinations that achieve deep remissions without cytotoxic chemotherapy. PATIENTS AND METHODS This phase II study tested a combination regimen of obinutuzumab, ibrutinib, and venetoclax for a total of 14 cycles in both patients with treatment-naïve (n = 25) and relapsed or refractory (n = 25) chronic lymphocytic leukemia to determine the response to therapy and safety. RESULTS The primary end point was the rate of complete remission with undetectable minimal residual disease by flow cytometry in both the blood and bone marrow 2 months after completion of treatment, which was 28% in both groups. The overall response rate at that time was 84% in treatment-naïve patients and 88% in relapsed or refractory patients. At that time, 67% of treatment-naïve patients and 50% of relapsed or refractory patients had undetectable minimal residual disease in both the blood and marrow. At a median follow-up of 24.2 months in treatment-naïve patients and 21.5 months in relapsed or refractory patients, the median progression-free and overall survival times were not yet reached, with only 1 patient experiencing progression and 1 death. Neutropenia and thrombocytopenia were the most frequent adverse events, followed by hypertension. Grade 3 or 4 neutropenia was experienced by 66% of patients, with more events in the relapsed or refractory cohort. There was only 1 episode of neutropenic fever. A favorable impact on both perceived and objective cognitive performance during treatment was observed. CONCLUSION The combination regimen of obinutuzumab, ibrutinib, and venetoclax offers time-limited treatment that results in deep remissions and is now being studied in phase III cooperative group trials.

7511 Background: Patients (pts) with chronic lymphocytic leukemia (CLL) suffer morbidity and mortality from CLL and increased risk for second primary neoplasia (SPN). BTK inhibitors (BTKi) are highly effective for the treatment (tx) of CLL and are associated with partial restoration of immune function with ongoing tx. The impact of BTKi on the risk for and patterns of SPN is yet to be characterized. Methods: CLL pts treated with ibrutinib or acalabrutinib at our center were identified retrospectively. Baseline (bl) and outcome data were collected including incidence (inc) of Richter’s transformation (RT), non-melanoma skin cancer (NMSC), and SPN. Standard inc ratio (SIR) with 95% confidence intervals (CI) were calculated using expected inc rates from the Surveillance, Epidemiology, and End Results Program, assuming a Poisson distribution for the observed inc. Cumulative inc (CIR) of SPN (excluding RT and NMSC) was calculated from BTKi start date to the diagnosis of SPN; death was a competing risk and pts without event were censored at last follow-up (f/u). SPN was correlated with bl data using the Fine-Gray model. Results: 691 pts were included; median age was 64 years (y), median prior lines of treatment (tx) was 2 (20% tx-naïve, 66% with prior chemo-immunotherapy), and 56% were never smokers. At median f/u of 44 months, 68 pts (10%) were diagnosed (dx) with SPN (SIR 2.4, CI 1.9-3.0) including 13 lung (SIR 3.2, CI 1.7-5.5), 9 melanoma (SIR 6.9, CI 3.1-13), 9 prostate (SIR 1.4, CI 0.6-2.6), 7 bladder (SIR 5.2, CI 2.1-10.6) cancers. CIR of SPN at 3 y was 7.6% (Table). Smoking (hazard ratio (HR) 2.9, CI 1.7-5.0, p < .01) and low bl CD8 count (HR 0.9 for 2-fold increase, CI 0.8-0.9, p < .01) were associated with higher inc of SPN. RT was dx in 58 pts (8%) and NMSC in 138 pts (20%). 179 pts had died with 3 y overall survival of 79% (CI 76-82); the most common causes of death were CLL/RT (57%) and SPN (13%). Conclusions: The inc of SPN in pts treated with BTKi for CLL is increased relative to the general population. With a 5 y CIR of NMSC and SPN of 23% and 12%, these data support consideration of intensive cancer screening for CLL pts receiving BTKi. [Table: see text]

Ibrutinib is associated with dramatic efficacy against B-cell malignancies. Yet, ibrutinib is linked with potentially-limiting cardiotoxicity, including emerging reports of profound hypertension. However, the long-term incidence, severity, and impacts of hypertension development during ibrutinib-use are unknown. Therefore, from 562 consecutive patients treated with ibrutinib for B-cell malignancies between 2009-2016 we assessed the incidence of new/incident or worsened hypertension [systolic blood pressure (BP) cutoff of 130mmHg]. Observed incident-hypertension rates were compared to Framingham-heart predicted incident-hypertension rates. We also evaluated the relationship of hypertension on ibrutinib to the development of other major-adverse-cardiovascular-events (MACE), including arrhythmias, myocardial infarction, stroke, heart failure, and cardiovascular death. Further, we assessed the preventative and modulatory effects of antihypertensives, by medication-class, on ibrutinib-related hypertension. Overall, 78.3% of ibrutinib-users developed new or worsened hypertension [mean systolic BP increase 5.2mmHg ({plus minus}20.7)] over a median of 30months. New hypertension developed in 71.6% of ibrutinib-users (467 observed vs. 39 Framingham-predicted cases per 1,000 person-years), with a time-to-50% cumulative incidence of 4.2months. Among those without preceding hypertension, 17.7% developed high-grade (BP g160/100mmHg) hypertension. In multivariable regression containing known predictors of MACE, new or worsened hypertension was associated with increased MACE [hazard ratio (HR) 2.17, 95%CI 1.08-4.38]. No single-antihypertensive class was associated with prevention or control of ibrutinib-related hypertension. However, antihypertensive initiation was associated with a lower risk of MACE (HR 0.40, CI 0.24-0.66). Collectively, these data suggest ibrutinib is associated with substantial increase in the incidence and severity of hypertension, and that hypertension development may suggest a higher risk of subsequent cardiotoxic events.

Purpose:Aberrant Myc expression is a major factor in the pathogenesis of aggressive lymphoma, and these lymphomas, while clinically heterogeneous, often are resistant to currently available treatments and have poor survival. Myc expression can also be seen in aggressive lymphomas that are observed in the context of CLL, and we sought to develop a mouse model that could be used to study therapeutic strategies for aggressive lymphoma in the context of CLL.Experimental Design:We crossed the Eμ-TCL1 mouse model with the Eμ-Myc mouse model to investigate the clinical phenotype associated with B-cell–restricted expression of these oncogenes. The resulting malignancy was then extensively characterized, from both a clinical and biologic perspective.Results:Eμ-TCL1xMyc mice uniformly developed highly aggressive lymphoid disease with histologically, immunophenotypically, and molecularly distinct concurrent CLL and B-cell lymphoma, leading to a significantly reduced lifespan. Injection of cells from diseased Eμ-TCL1xMyc into WT mice established a disease similar to that in the double-transgenic mice. Both Eμ-TCL1xMyc mice and mice with disease after adoptive transfer failed to respond to ibrutinib. Effective and durable disease control was, however, observed by selective inhibition of nuclear export protein exportin-1 (XPO1) using a compound currently in clinical development for relapsed/refractory malignancies, including CLL and lymphoma.Conclusions:The Eμ-TCL1xMyc mouse is a new preclinical tool for testing experimental drugs for aggressive B-cell lymphoma, including in the context of CLL.

In chronic lymphocytic leukemia (CLL) and very likely all cancer types, extracellular vesicles (EVs) are a common mechanism by which intercellular messages are communicated between normal, diseased, and transformed cells. Studies of EVs in CLL and other cancers have great variability and often lack reproducibility. For CLL patient plasma and cell lines, we sought to characterize current approaches used in isolating EV products and understand whether cell culture–conditioned media or complex biological fluids confound results. Utilizing nanoparticle tracking analysis, protein quantification, and electron microscopy, we show that ultracentrifugation with an OptiPrep cushion can effectively minimize contaminants from starting materials including plasma and conditioned media of CLL cell lines grown in EV-depleted complete RPMI media but not grown in the serum-free media AIM V commonly used in CLL experimental work. Moreover, we confirm the benefit of including 25 mM trehalose in PBS during EV isolation steps to reduce EV aggregation, to preserve function for downstream applications and characterization. Furthermore, we report the highest particles/μg EVs were obtained from our CLL cell lines utilizing the CELLine bioreactor flask. Finally, we optimized a proliferation assay that offers a functional evaluation of our EVs with minimal sample requirements.

Background: Acalabrutinib (A) is a next-generation, highly selective, covalent Bruton tyrosine kinase (BTK) inhibitor approved for marketing by the US FDA in patients (pts) with chronic lymphocytic leukemia (CLL). While responses to A monotherapy are durable in CLL, response depth may be enhanced with combination therapy and potentially allow treatment discontinuation. The safety and efficacy of A plus a CD20 antibody (obinutuzumab [O] or rituximab [R]) and the BCL-2 inhibitor venetoclax (V) were examined in a phase 1b study (CL-003; NCT02296918) in relapsed/refractory (R/R) or treatment-naïve (TN) CLL pts. Methods: Pts were aged ≥18 years with intermediate or high-risk CLL (R/R or TN) and an Eastern Cooperative Oncology Group performance status (ECOG PS) ≤2. Prior BTK inhibitor treatment was allowed for R/R pts if discontinuation was not due to CLL progression. R/R CLL pts received oral (PO) A 100 mg twice daily (BID) until progression, plus intravenous (IV) R 375 mg/m2 for 9 infusions (cycles 2-7), plus V PO daily per standard dosing (cycles 3-15). TN CLL pts received PO A and V (as above) plus IV O per standard dosing (cycles 2-7). The primary endpoint was safety. Secondary endpoints included investigator-assessed overall response rate (ORR, partial response [PR] or better) at cycle 16, complete response (CR) rate, undetectable minimal residual disease (uMRD) rate, duration of response (DOR), progression-free survival (PFS), overall survival (OS), and pharmacokinetics (PK). Results: Twelve pts were included in each cohort (R/R: male, n=9 [75%], median [range] age: 66 [55-72] y; TN: male, n=9 [75%], median [range] age: 61 [42-73] y). All pts had ECOG PS ≤1; 6/8 (75%) R/R and 8/10 (80%) TN pts had unmutated IGHV ( At a median follow-up of 23.2 mo (range: 19.8-25.3) in R/R pts and 22.0 mo (range: 19.5-24.4) in TN pts, 11 (92%) and 10 (83%) pts remained on treatment, respectively. Reasons for treatment discontinuation were adverse events (AEs) in 1 pt (8%) in each cohort (R/R: grade 1 purpura; TN: grade 2 head discomfort), and withdrawal by 1 pt (8%) in the TN cohort. The median number of treatment cycles in R/R pts was 23 (range: 14.9-27.5) for A, 6 (6-6) for R, and 13 (10.0-13.7) for V, and in TN pts was 23 (18.0-24.8) for A, 6 (6-6) for O, and 13 (13.0-13.5) for V. Reported AEs were similar to the individual agents' toxicity profiles (Table 1). Among AEs of interest, 7 R/R pts (58%) and 4 TN pts (33%) had cardiac AEs; grade ≥3 cardiac AEs were reported in 1 pt (8%). Atrial fibrillation was reported in 1 pt (grade 3; R/R pt with prior atrial fibrillation history). No ventricular arrhythmias were reported. Three R/R pts (25%) and 7 TN pts (58%) had hypertension AEs; none were grade ≥3. The most frequent infections (≥40%) were upper respiratory tract infection (URTI; 50%) in R/R pts and URTI (67%), sinusitis (42%), and nasopharyngitis (42%) in TN pts. Grade ≥3 infections occurred in 3 TN pts (lung infection, n=2 [17%]; prostate infection, staphylococcal bacteremia, staphylococcal sepsis, n=1 [8%] each) and no R/R pts. Six R/R pts (50%) and 3 TN pts (25%) had infusion-related reactions; none were grade ≥3. One R/R pt (8%) and 6 TN pts (50%) had decreased neutrophil counts; all were grade ≥3. No tumor lysis syndrome AEs, Richter transformations, or deaths were reported. After 16 cycles, ORR was 92% (95% CI: 62-100) in R/R pts and 100% (95% CI: 74-100) in TN pts. At the time of data cutoff, 50% of pts in each cohort had achieved CR or CR with incomplete marrow recovery (CRi). All pts with CR or CRi achieved uMRD (10-4) in peripheral blood (PB) at the time of CR/CRi or earlier. Overall, 8 (67%) R/R and 9 (75%) TN pts achieved uMRD (10-4) in PB at cycle 10 (Table 2). Median DOR, PFS, and OS were not reached in either group. Estimated 18-mo PFS and OS rates were 100% (95% CI: not estimable) in both cohorts. The PK of A and its active metabolite, ACP-5862, were consistent when given as monotherapy or with V, R, or O. The PK of V remained within the range observed with monotherapy (Salem et al. J Clin Pharmacol. 2017;57:484-492) when given with A. Conclusions: Combination therapy with A plus an anti-CD20 antibody and BCL-2 inhibitor leads to a tolerable safety profile with high CR and uMRD rates in both R/R and TN CLL pts, with minimal to no drug-drug interactions. Disclosures Woyach: Pharmacyclics, Janssen, Morphosys, Karyopharm, Verastem, Abbvie, Lox: Research Funding; Pharmacyclics LLC, an AbbVie Company, AbbVie, Janssen, AstraZeneca, ArQule: Honoraria; Janssen, Pharmacyclics, AstraZeneca, Abbvie, Arqule: Consultancy. Blachly:AbbVie, AstraZeneca, KITE Pharma: Consultancy. Rogers:Janssen: Research Funding; AstraZeneca: Consultancy, Other: Travel Funding; Pharmacyclics: Consultancy; AbbVie: Consultancy, Research Funding; Genentech: Research Funding; Acerta Pharma: Consultancy. Lozanski:Genentech, Novartis, Beckman Coulter: Research Funding. Andersen:Ohio State University: Current Employment, Research Funding. Patel:AstraZeneca: Current Employment, Current equity holder in publicly-traded company. Munugalavadla:Acerta Pharma/AstraZeneca: Current Employment, Current equity holder in publicly-traded company; Gilead Sciences: Current equity holder in publicly-traded company, Other: Family Association. Butturini:Puma Biotechnology: Divested equity in a private or publicly-traded company in the past 24 months; Dynavax, Puma Biotechnology: Ended employment in the past 24 months; Roche/Genentech, Pfeizer, AstraZeneca, Amgen: Current equity holder in publicly-traded company; Acerta Pharma: Current Employment. Xu:Acerta Pharma: Current Employment, Research Funding; AstraZeneca: Research Funding. Wang:Acerta Pharma: Current Employment. Byrd:Acerta Pharma: Research Funding; Syndax: Research Funding; Novartis: Research Funding; Kartos Therapeutics: Research Funding; Trillium: Research Funding; Leukemia and Lymphoma Society: Other; Janssen: Consultancy; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, Novartis, Janssen: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company, Janssen, Novartis, Gilead, TG Therapeutics: Other; Vincera: Research Funding.

Alterations in global DNA methylation patterns are a major hallmark of cancer and represent attractive biomarkers for personalized risk stratification. Chronic lymphocytic leukemia (CLL) risk stratification studies typically focus on time to first treatment (TTFT), time to progression (TTP) after treatment, and overall survival (OS). Whereas TTFT risk stratification remains similar over time, TTP and OS have changed dramatically with the introduction of targeted therapies, such as the Bruton tyrosine kinase inhibitor ibrutinib. We have shown that genome-wide DNA methylation patterns in CLL are strongly associated with phenotypic differentiation and patient outcomes. Here, we developed a novel assay, termed methylation-iPLEX (Me-iPLEX), for high-throughput quantification of targeted panels of single cytosine guanine dinucleotides from multiple independent loci. Me-iPLEX was used to classify CLL samples into 1 of 3 known epigenetic subtypes (epitypes). We examined the impact of epitype in 1286 CLL patients from 4 independent cohorts representing a comprehensive view of CLL disease course and therapies. We found that epitype significantly predicted TTFT and OS among newly diagnosed CLL patients. Additionally, epitype predicted TTP and OS with 2 common CLL therapies: chemoimmunotherapy and ibrutinib. Epitype retained significance after stratifying by biologically related biomarkers, immunoglobulin heavy chain mutational status, and ZAP70 expression, as well as other common prognostic markers. Furthermore, among several biological traits enriched between epitypes, we found highly biased immunogenetic features, including IGLV3-21 usage in the poorly characterized intermediate-programmed CLL epitype. In summary, Me-iPLEX is an elegant method to assess epigenetic signatures, including robust classification of CLL epitypes that independently stratify patient risk at diagnosis and time of treatment.

Targeted therapies including the engineered afucosylated anti-CD20 monoclonal antibody obinutuzumab, Bruton’s tyrosine kinase inhibitor ibrutinib, and B-cell lymphoma protein 2 inhibitor venetoclax have demonstrated significant clinical activity in chronic lymphocytic leukemia (CLL) and, based on their complementary mechanisms, are ideal for combination. However, combining venetoclax with other active agents raises safety concerns, as it may increase the risk for tumor lysis syndrome. To minimize this risk, we designed and implemented a fixed-duration regimen using sequentially administered obinutuzumab followed by ibrutinib (cycle 2) and venetoclax (cycle 3), for a total of fourteen 28-day cycles. This phase 1b study included 12 patients with relapsed or refractory CLL. We tested 3 dose levels of venetoclax and identified the doses of all 3 agents approved by the US Food and Drug Administration for use in the combination. Adverse events were consistent with known toxicities of the individual agents, with hematologic adverse events being most frequent. No clinically significant tumor lysis syndrome occurred. The overall response rate was 92% (95% confidence interval, 62%-100%), with 42% (5/12) achieving a complete remission or complete remission with incomplete marrow recovery. There were 6 patients with no detectable CLL in both the blood and bone marrow at the end of treatment. We found this regimen to be safe and tolerable in CLL, and capable of inducing deep responses, justifying future study in our ongoing phase 2 cohorts of relapsed or refractory and treatment-naive patients, as well as larger phase 3 trials currently in planning. This trial was registered at www.clinicaltrials.gov as #NCT02427451.

Richter syndrome (RS) of chronic lymphocytic leukemia (CLL) is typically chemoresistant, with a poor prognosis. We hypothesized that the oral Bcl-2 inhibitor venetoclax could sensitize RS to chemoimmunotherapy and improve outcomes. We conducted a single-arm, investigator-sponsored, phase 2 trial of venetoclax plus dose-adjusted rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (VR-EPOCH) to determine the rate of complete response (CR). Patients received R-EPOCH for 1 cycle, then after count recovery, accelerated daily venetoclax ramp-up to 400 mg, then VR-EPOCH for up to 5 more 21-day cycles. Responders received venetoclax maintenance or cellular therapy off-study. Twenty-six patients were treated, and 13 of 26 (50%) achieved CR, with 11 achieving undetectable bone marrow minimal residual disease for CLL. Three additional patients achieved partial response (overall response rate, 62%). Median progression-free survival was 10.1 months, and median overall survival was 19.6 months. Hematologic toxicity included grade ≥3 neutropenia (65%) and thrombocytopenia (50%), with febrile neutropenia in 38%. No patients experienced tumor lysis syndrome with daily venetoclax ramp-up. VR-EPOCH is active in RS, with deeper, more durable responses than historical regimens. Toxicities from intensive chemoimmunotherapy and venetoclax were observed. Our data suggest that studies comparing venetoclax with chemoimmunotherapy to chemoimmunotherapy alone are warranted. This trial was registered at www.clinicaltrials.gov as #NCT03054896.

This study aimed to describe treatment sequencing and healthcare costs among chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) patients treated with venetoclax in a US managed care population. CLL/SLL patients initiating venetoclax between 04/11/2016 and 06/30/2019 were selected from Optum’s de-identified Clinformatics Data Mart Database. Costs per-patient-per-month were described during the first 60 days of venetoclax-based treatment (initiation phase) and subsequent post-initiation phase. Based on venetoclax prescribing information, clinical event-related costs were identified through claims for tumor lysis syndrome (TLS) diagnosis, monitoring, prophylaxis, immunoglobulin treatment, neutropenia, thrombocytopenia, infection, renal impairment, hypertension, or cardiac arrhythmia. Statistical testing was not conducted due to small sample size. Twenty-five, 30, and 66 patients initiated venetoclax as their first observed regimen (1L), second observed regimen (2L), and third or later observed regimen (3L+), respectively. Most 2L (56.7%) and 3L+ (74.2%) venetoclax recipients previously received ibrutinib. Mean monthly all-cause costs during the initiation phase were $26,429 (1L cohort), $19,580 (2L cohort), and $23,918 (3L + cohort). Among the 2L cohort, mean monthly all-cause [clinical event-related] (including TLS) costs during initiation and post-initiation phases of venetoclax treatment were $15,506 [$6368] (initiation phase) and $14,318 [$5273] (post-initiation phase; median duration: 3.7 months) for patients receiving 1L ibrutinib, and $24,908 [$12,198] (initiation phase) and $16,905 [$7066] (post-initiation phase; median duration: 3.0 months) for patients not receiving 1L ibrutinib. In this descriptive study, highest mean costs were observed during venetoclax initiation phase. Venetoclax patients previously receiving ibrutinib had lower mean total all-cause and clinical event-related (including TLS) costs during their venetoclax line of therapy than those previously receiving non-ibrutinib therapy.

Noninfectious, ibrutinib-attributable adverse events resulting in discontinuation signifies an area of unmet need for patients with chronic lymphocytic leukemiaPatients discontinuing ibrutinib for ...

Hairy cell leukemia (HCL) is a rare B-cell malignancy, and there is a need for novel treatments for patients who do not benefit from purine analogs. Ibrutinib, an oral agent targeting Bruton tyrosine kinase in the B-cell receptor signaling pathway, is highly effective in several malignancies. Its activity in HCL was unknown, so we conducted a multisite phase 2 study of oral ibrutinib in patients with either relapsed classic or variant hairy cell leukemia. The primary outcome measure was the overall response rate (ORR) at 32 weeks, and we also assessed response at 48 weeks and best response during treatment. Key secondary objectives were characterization of toxicity and determination of progression-free survival (PFS) and overall survival (OS). Thirty-seven patients were enrolled at 2 different doses (24 at 420 mg, 13 at 840 mg). The median duration of follow-up was 3.5 years (range, 0-5.9 years). The ORR at 32 weeks was 24%, which increased to 36% at 48 weeks. The best ORR was 54%. The estimated 36-month PFS was 73% and OS was 85%. The most frequent adverse events were diarrhea (59%), fatigue (54%), myalgia (54%), and nausea (51%). Hematologic adverse events were common: anemia (43%), thrombocytopenia (41%), and neutropenia (35%). Ibrutinib can be safely administered to patients with HCL with objective responses and results in prolonged disease control. Although the initial primary outcome objective of the study was not met, the observation of objective responses in heavily pretreated patients coupled with a favorable PFS suggests that ibrutinib may be beneficial in these patients. This trial was registered at www.clinicaltrials.gov as #NCT01841723.

Chronic lymphocytic leukemia (CLL) patients who develop Hodgkin lymphoma (HL) have limited survival. No current therapeutic standard of care exists. We conducted a multi-center retrospective study of patients with Hodgkin transformation (HT) of CLL. Clinicobiologic characteristics, treatment type, and survival outcomes were analyzed and compared with historic case series. Ninety-four patients were identified. Median age at HT was 67 years (range, 38-85). Median time from CLL diagnosis to HT was 5.5 years (range, 0-20.2). Prior to HT, patients received a median of two therapies for CLL (range, 0-12). As initial therapy for HT, 61% (n=62) received ABVD-based regimens (adriamycin, bleomycin, vinblastine, and dacarbazine). Seven (7%) patients received hematopoietic cell transplantation (HCT) while in first complete remission (CR1). The median number of treatments for HT per patient was one (range, 0-5) with 59 (61%) patients only receiving one line of therapy. After HT, patients had a median follow-up of 1.6 years (range, 0-15.1). Two-year overall survival (OS) after HT diagnosis was 72% (95% Confidence Interval: 62-83). The patients who received standard ABVD-based therapy had a median OS of 13.2 years. Although limited by small sample size, the patients who underwent HCT for HT in CR1 had a similar 2-year OS (n=7; 67%) compared to patients who did not undergo HCT for HT in CR1 (n=87; 72%; P=0.46). In this multi-center study, HT patients treated with ABVD-based regimens had prolonged survival supporting the use of these regimens as standard of care for these patients.

B-cell receptor signalling inhibition by targeting Bruton tyrosine kinase (BTK) is effective in treating chronic lymphocytic leukemia (CLL). The BTK inhibitor ibrutinib may be intolerable for some patients. Acalabrutinib is a more selective BTK inhibitor that may be better tolerated by patients who are intolerant to ibrutinib. A phase 2 study of acalabrutinib was conducted in patients with relapsed/refractory CLL who were ibrutinib-intolerant and had continued disease activity. Intolerance was defined as having discontinued ibrutinib due to persistent grade 3/4 adverse events (AEs) or persistent/recurrent grade 2 AEs despite dose modification/interruption. Patients received oral acalabrutinib 100 mg twice daily until disease progression or intolerance. Sixty patients were treated. Overall response rate to acalabrutinib was 73% and three patients (5%) achieved complete remission. At median follow-up of 35 months, the median progressionfree and overall survival were not reached; 24-month estimates were 72% and 81%, respectively. The most frequent AEs with acalabrutinib were diarrhea (53%), headache (42%), contusion (40%), dizziness (33%), upper respiratory tract infection (33%), and cough (30%). Most common reasons for acalabrutinib discontinuation were progressive disease (23%) and AEs (17%). Most patients with baseline samples (49/52; 94%) and all with on-treatment samples (3/3; 100%) had no detectable BTK and/or PLCG2 mutations. Acalabrutinib is effective and tolerable in most patients with relapsed/refractory CLL who are intolerant of ibrutinib. Acalabrutinib may be useful for patients who may benefit from BTK inhibitor therapy but are ibrutinib intolerant.

Venetoclax has efficacy in patients relapsing after B-cell receptor pathway inhibitors (BCRis); however, because of the risk of tumor lysis syndrome (TLS), a 5-week dose ramp-up is required to attain the target dose. Patients relapsing after BCRis frequently have proliferative disease, requiring a faster time to target dose than this scheme allows. This limitation can potentially be overcome with rapid dose escalation (RDE). We analyzed 33 chronic lymphocytic leukemia patients who underwent venetoclax RDE after prior BTKi treatment. Median time to target dose was 9 days. Seventeen patients (52%) developed laboratory TLS, and 5 (15%) developed clinical TLS, all as a result of renal injury. TLS was seen in more patients with a higher initial tumor burden. TLS occurred at all dose levels, with most episodes occurring at the 50- and 100-mg doses. Most interestingly, a decrease in absolute lymphocyte count (ALC) from pre–venetoclax dose to 24 hours post–venetoclax dose of 10 × 103/μL was associated with an increased risk of TLS (hazard ratio, 1.32; P = .02), after controlling for venetoclax dose level. Venetoclax RDE with close in-hospital monitoring at experienced centers and in select patients is feasible. The rapidity with which ALC drops helps predict TLS and could help guide dose-escalation decisions.

Acalabrutinib is a selective irreversible Bruton tyrosine kinase (BTK) inhibitor that does not affect IL2-associated tyrosine kinase or antibody-dependent cellular cytotoxicity, making it an attractive candidate for combination therapy with anti-CD20 antibodies. We investigated acalabrutinib plus obinutuzumab in a phase Ib/II study (NCT02296918) of patients with treatment-naïve or relapsed/refractory chronic lymphocytic leukemia (CLL). Nineteen treatment-naïve and 26 relapsed/refractory patients were treated with acalabrutinib (100 mg twice daily) until progression and obinutuzumab (cycle 1: 100 mg day 1, 900 mg day 2, 1000 mg days 8 and 15; cycles 2–6: 1,000 mg day 1). Grade 3/4 adverse events occurred in 71% of patients. Overall response rates were 95% (treatment-naïve) and 92% (relapsed/refractory). Thirty-two percent of treatment-naïve and 8% of relapsed/refractory patients achieved complete remission. At 36 months, 94% (treatment-naïve) and 88% (relapsed/refractory) were progression free. Acalabrutinib plus obinutuzumab was well tolerated, producing high and durable responses in treatment-naïve and relapsed/refractory CLL. Significance: Rituximab plus the less selective BTK inhibitor ibrutinib has not shown benefit in CLL; however, the selective BTK inhibitor acalabrutinib plus the antibody-dependent cellular cytotoxicity–enhanced antibody obinutuzumab yielded durable responses that deepened over time in treatment-naïve and relapsed/refractory CLL, supporting the evaluation of this approach in larger, comparative studies in CLL. This article is highlighted in the In This Issue feature, p. 327

Detecting, characterizing, and monitoring rare populations of cells can increase testing sensitivity, give insight into disease mechanism, and inform clinical decision making. One area that can benefit from increased resolution is management of cancers in clinical remission but with measurable residual disease (MRD) by multicolor FACS. Detecting and monitoring genomic clonal resistance to treatment in the setting of MRD is technically difficult and resource intensive due to the limited amounts of disease cells. Here, we describe limited-cell FACS sequencing (LC-FACSeq), a reproducible, highly sensitive method of characterizing clonal evolution in rare cells relevant to different types of acute and chronic leukemias. We demonstrate the utility of LC-FACSeq for broad multigene gene panels and its application for monitoring sequential acquisition of mutations conferring therapy resistance and clonal evolution in long-term ibrutinib treatment of patients with chronic lymphocytic leukemia. This technique is generalizable for monitoring of other blood and marrow infiltrating cancers.

Introduction: The development of Bruton tyrosine kinase inhibitors (BTKi) and their introduction into clinical practice represent a major advance in the treatment of chronic lymphocytic leukemia (CLL). Ibrutinib and other second generation BTKi as monotherapies generally do not produce minimal residual disease negative (MRD-) complete remissions even with extended therapy. The reason for lack of continued elimination of CLL to a MRD- status over time is unknown, and we hypothesized that biological differences in the CLL cells or immune microenvironment might make them resistant to elimination. Methods: Samples were obtained from patients on continuous ibrutinib who hadn't relapsed at time points of 3 years on treatment and 5 years on treatment; and pre-ibrutinib. Isolated CLL cells were subject to B-cell receptor (BCR) sequencing using NEBNext Immune Sequencing Kit by New England Biolabs (NEB, Inc., USA). In a separate cohort, 10X VDJ+5'-sequencing was performed on peripheral blood mononuclear cells. Flow cytometry and ELISA were used to identify alterations in immune cell subtype and identify immune profiles associated with MRD positive (MRD+) status. Results: To identify the clonal pattern in MRD+, we performed deep sequencing of the BCR repertoire on samples from 13 patients with 3 time points each. We found that dominant clones tended to remain constant, but new clones appeared in later time points (Figure 1). MiXCR (v3.0.5) was used with default parameters to identify preprocessed reads containing CDR3 regions from B-cell heavy, kappa, and lambda chains, generating a list of unique productive and nonproductive CDR3 sequences associated with their relative abundances and specific V(D)J gene usage. Two out of three patients (patients 1 and 3) showed significant change in the clone over time. In patients 1 and 2, we saw that heavy chain clones emerge at later time points. In patient 3 alone, we observed that at 5 years there are two dominant clones. Our findings suggest that each patient shows a diverse repertoire of CLL clones and that the dominant clone does not change significantly across time points. To identify cell populations based on gene expression patterns, we performed 10X VDJ+5'-seq. Based on the expression of known markers, we identified CLL cells and other immune cell subtypes. We identified differentially expressed genes (DEGs) for CLL cells in each time points. Over time, we observed upregulation of CD79a, LTB, TAGLN2, and LGALS, genes typically associated with leukemic cell survival. Suggesting differential expression of pro-survival genes contribute to continued presence of MRD over time. T cells are known to be dysfunctional in CLL and have not previously been extensively studied in the setting of long term BTKi. We performed flow cytometry to determine the repertoire and function of T cells at 3 and 5 years of ibrutinib therapy. We found that the percentage of CD3+ T cells increases at later time points in all the 8 patients (p Conclusion: Extended ibrutinib treatment yields a subset of patients who become MRD- whereas a large majority remain MRD+. Our findings suggest that BCR repertoire in CLL MRD might change in long term ibrutinib therapy and induce necessary genes for its survival in the microenvironment. Although T cells and NK cells are non-functional at later time points, better understanding of these subtypes may lead to new strategies and to improve antitumor function of these cells. Differentiating the biology of why certain patients attain MRD- status on BTK inhibitor is of high interest as it could provide rationale for therapy discontinuation or add on approaches. Figure 1 Figure 1. Disclosures Rogers: AbbVie Inc.: Consultancy, Research Funding; Acerta Pharma: Consultancy; AstraZeneca: Consultancy; Genentech: Consultancy, Research Funding; Innate Pharma: Consultancy; Pharmacyclics LLC: Consultancy; Janssen Pharmaceuticals, Inc: Research Funding; ovartis Pharmaceuticals Corporation: Research Funding. Bhat: Beigene: Consultancy; AstraZeneca: Consultancy; Aptitude Health: Honoraria; Onclive: Honoraria. Kittai: Bristol-Meyers Squibb: Consultancy; Abbvie: Consultancy; Janssen: Consultancy. Blachly: INNATE: Consultancy, Honoraria; KITE: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria. Byrd: Novartis, Trillium, Astellas, AstraZeneca, Pharmacyclics, Syndax: Consultancy, Honoraria; Vincerx Pharmaceuticals: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Newave: Membership on an entity's Board of Directors or advisory committees. Woyach: AbbVie Inc, ArQule Inc, Janssen Biotech Inc, AstraZeneca, Beigene: Other: Advisory Committee; AbbVie Inc, ArQule Inc, AstraZeneca Pharmaceuticals LP, Janssen Biotech Inc, Pharmacyclics LLC, an AbbVie Company,: Consultancy; AbbVie Inc, Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Research Funding; Gilead Sciences Inc: Other: Data & Safety.

Introduction: B-cell activating factor receptor (BAFF-R) enhances the survival and regulation of normal and malignant B cells. VAY736 is a human monoclonal antibody (mAb) targeting BAFF-R that targets BAFF-R+ B cells for elimination by antibody-dependent cell-mediated cytotoxicity (ADCC). VAY736 has anti-leukemia activity in preclinical CLL models that is superior to that of anti-CD20 mAbs (McWilliams EM, et al. Blood Adv 2019;3:447-460). Although Bruton's tyrosine kinase inhibitors (BTKis; acalabrutinib, ibrutinib) are the current standard of care for CLL, the indefinite length of monotherapy required may result in cumulative clinical or economic toxicity and/or acquired treatment resistance. In preclinical models, adding VAY736 to ibrutinib significantly improved survival and reduced disease burden, suggesting that this combination may augment the anti-leukemia response and allow patients (pts) to discontinue ibrutinib. Methods: This dose escalation/expansion trial (NCT03400176) enrolled pts with CLL undergoing either first- or second-line therapy with ibrutinib and whose disease failed to achieve a complete response (CR) after >1 year of therapy or who had CLL with a mutation associated with ibrutinib resistance. Pts received oral ibrutinib (420 mg) once daily and VAY736 IV at 0.3, 1, 3, or 9 mg/kg once every 2 weeks. In the expansion, pts were enrolled into 2 arms depending on whether ibrutinib resistance mutations were present at baseline. Pts received VAY736 + ibrutinib for up to 6 28-day cycles. After 6 cycles, pts with a CR discontinued VAY736 and received ibrutinib for an additional 2 cycles; all other pts continued VAY736 + ibrutinib for those 2 cycles. Pts achieving undetectable minimal residual disease (uMRD) at C9D1 could discontinue ibrutinib at the investigator's discretion. This study aimed to characterize the safety and tolerability of VAY736 + ibrutinib, determine the recommended dose for expansion (RDE), and explore the efficacy of this combination. Results: A total of 32 pts (median age 65 years; ECOG PS 0: 91%) were treated prior to data cutoff (May 10, 2021). Overall, 19 pts completed therapy and 4 discontinued VAY736 + ibrutinib (primarily due to disease progression); 4 pts remain on VAY736 + ibrutinib and 5 pts continue to receive ibrutinib. Of the enrolled pts, 44% had CLL cells with mutations associated with ibrutinib resistance (mainly [71%] BTKC481); the median number of prior regimens was 1 (range: 0.0-14.0); median duration of prior ibrutinib therapy was 3.5 years (range: 0.2-8.3). Baseline cytogenetics were (not mutually exclusive): 19% del(17)(p13.1), 75% unmutated IGHV, 59% stimulated complex karyotypes (≥3 abnormalities), 34% del(11)(q22.3), 44% del(13)(q14), and 6% +12. No dose-limiting toxicities were observed and the RDE was 3 mg/kg, based on pharmacokinetics, exposure-to-response relationship, pharmacodynamics, safety, and in vitro ADCC. Twelve (38%) pts experienced AEs of Grade ≥3, most common (occurring in ≥2 pts) were neutrophil count decreased (n=5), lymphocyte count decreased (n=2), hypophosphatemia (n=2), and elevated lipase (n=2). The overall response at C9D1 for evaluable pts (n=21) was 38% CR, 5% CRi, 14% PR, 24% SD, and 19% PD (Fig. 1A). Thirteen (41%) pts achieved uMRD in blood. Eight pts (42%, 8/19) and 8 pts (42%, 8/19) had uMRD in blood and bone marrow (BM) at end of treatment (EoT), respectively. Among those, 6 pts were elected to discontinue ibrutinib and remained off treatment for 0.2-26.2 months and were still off therapy at the data cutoff. The median percentage change from baseline in MRD was -99.0% (range: -100.0% to -16.7%) and -97.3% (range: -100.0% to 1346.3%) in blood and BM, respectively. None of the pts who enrolled with CLL cells lacking mutations associated with ibrutinib resistance (11/11) developed mutations by C9D1. Although 1 pt with PLCG2 mutation eradicated mutant clones at EoT with VAY736, the response may vary depending on the type of mutation (Fig. 1B). Conclusions: VAY736 + ibrutinib was well tolerated with an acceptable safety profile enabling dose expansion. Clinical activity was observed including multiple pts attaining uMRD status in blood and BM, allowing 6 to discontinue ibrutinib therapy for an extended period. These data provide clinical evidence of the potent anti-leukemia activity of VAY736 and the potential to safely discontinue ibrutinib or other BTKi by VAY736 add-on therapy. Figure 1 Figure 1. Disclosures Rogers: AbbVie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy; Pharmacyclics: Consultancy; Innate Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Janssen: Research Funding. Flinn: TG Therapeutics: Consultancy, Other: All consultancy and 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; Yingli Pharmaceuticals: 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; BeiGene: 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; Constellation Pharmaceuticals: Other: All 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; Forty Seven: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Agios: 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; Iksuda Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Juno Therapeutics: Consultancy, Other: All consultancy and 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; Genentech: 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; Verastem: 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; AstraZeneca: 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; Loxo: 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; Pharmacyclics LLC, an AbbVie Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Kite, a Gilead Company: Consultancy, Other: All consultancy and 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; Celgene: 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; ArQule: Other: All 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; Unum 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; Nurix Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Merck: Other: All 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; Incyte: 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; Acerta Pharma: Other: All 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; Pfizer: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Portola 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; 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. Stephens: TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Adaptive: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Epizyme: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; JUNO: Research Funding; Arqule: Research Funding; AstraZeneca: Consultancy; Abbvie: Consultancy; Mingsight: Research Funding; CSL Behring: Consultancy; Celgene: Consultancy; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kipps: Oncternal Therapeutics, Inc.: Current equity holder in publicly-traded company, Patents & Royalties: Cirmtuzumab, Research Funding; Pharmacyclics/AbbiVie: Honoraria, Research Funding; Genentech/Roche: Honoraria; Celgene: Honoraria, Research Funding; VelosBio, Inc.: Research Funding; Janssen, Gilead, Dava Oncology,: Honoraria; Breast Cancer Research Foundation: Honoraria, Research Funding; Md Anderson Cancer Center: Research Funding; Gilead: Honoraria; National Cancer Institute/NIH: Honoraria, Research Funding; OncLive: Honoraria; Specialized Center of Research (SCOR) - The Leukemia and Lymphoma Society (LLS): Research Funding; California Institute for Regenerative Medicine (CIRM): Research Funding; European Research Initiative on CLL (ERIC): Honoraria; Dava Oncology: Honoraria; Patient Power, LLC: Honoraria; iwNHL: Honoraria; NCCN CLL/SLL Hairy Cell Leukemia Panel Meeting: Honoraria. Larson: TORL biotherapeutics: Current holder of individual stocks in a privately-held company; Abbvie: Research Funding; Bioline: Research Funding; BMS: Research Funding; Celgene: Research Funding; GSK: Research Funding; Janssen: Research Funding; Juno: Research Funding; Novartis: Research Funding; Pfizer: Research Funding; Takeda: Research Funding. McGarry: Novartis Institutes for Biomedical Research: Current Employment. Hassounah: Novartis Institutes for Biomedical Research: Current Employment, Patents & Royalties: unrelated . Gou: Novartis Pharma AG: Current Employment. Woo: Novartis: Current Employment, Current equity holder in publicly-traded company. Byrd: Novartis, Trillium, Astellas, AstraZeneca, Pharmacyclics, Syndax: Consultancy, Honoraria; Newave: Membership on an entity's Board of Directors or advisory committees; Vincerx Pharmaceuticals: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees.

Introduction: Alliance for Clinical Trials in Oncology A041202 is a NCI National Clinical Trials Network phase 3 study (NCT01886872) comparing BR (Arm 1) with ibrutinib (Arm 2) and the combination of ibrutinib plus rituximab (Arm 3) to determine whether ibrutinib-containing regimens are superior to chemoimmunotherapy (CIT) in terms of progression-free survival (PFS), and whether rituximab adds benefit to ibrutinib therapy. Initial results showed that ibrutinib-containing regimens had superior PFS to CIT, and that rituximab added to ibrutinib did not improve PFS over ibrutinib alone. Pts and Methods: Eligible pts on A041202 were those age ≥ 65 years with previously untreated, symptomatic CLL. Pts had a CrCl > 40 mL/min, bilirubin < 1.5 x ULN, and no significant life-limiting intercurrent illness or need for warfarin treatment. Pts were stratified on Rai stage, Zap-70 methylation performed centrally, and del(17)(p13.1) or del(11)(q22.3) by local interphase cytogenetics and were randomized 1:1:1 to each arm. Pts on Arm 1 who progressed could cross over to Arm 2. Here we present an updated analysis after the third planned interim analysis of Arms 2 and 3 versus Arm 1, and at the second planned interim analysis for Arms 3 vs 2. PFS and OS were estimated using the Kaplan-Meier method and corresponding hazard ratios with p-values were estimated using Cox proportional hazards models. These data encompass patient visits through April 2020 and were locked 15 February 2021. Results: Between 12/9/2013 and 5/16/2016, 547 pts were randomized (Arms 1: 183, 2: 182, and 3: 182). Baseline characteristics have previously been reported; briefly, median age was 71 years, 53% had unmethylated Zap-70, 61% were IGHV unmutated (performed in 66% of patients), 6% had del(17p) and 20% del(11q) by central FISH. Stimulated karyotype was performed centrally and revealed ≥ 3 abnormalities in 27%, and ≥ 5 in 11% of patients. With median follow-up of 55 months (mo), median PFS was 44 mo (95% CI 38-54) in Arm 1 and has not been reached in Arms 2 or 3 [Arm 2 vs 1 hazard ratio (HR): 0.36, 95% CI 0.26-0.52, p The benefit of ibrutinib regimens over CIT, with no additional benefit of rituximab when combined with ibrutinib, was consistent for all subgroups of patients defined by TP53 abnormalities, del(11q), complex karyotype, and IGHV (Figure 3). No significant interaction effects were observed between treatment arm and del(11q), complex karyotype, or IGHV. However, greater benefit of ibrutinib regimens over CIT was observed among patients with TP53 abnormalities than without (p Notable adverse events with ibrutinib include atrial fibrillation or flutter (afib) and hypertension (HTN). All grade afib was seen in 11 pts on BR (6%) and 67 pts on ibrutinib (19%). All grade HTN was seen in 95 pts on BR (54%) and 263 pts on ibrutinib (73%). Conclusions: This update of the A041202 trial continues to show that ibrutinib regimens prolong PFS over BR for older patients with treatment-naïve CLL. With longer follow-up, these benefits continue to be seen across subgroups, including those associated with higher risk disease. Strikingly, within the ibrutinib arms, there does not appear to be inferior PFS for patients with abnormalities in TP53, the highest risk feature seen in CLL, and a predictor of inferior PFS with ibrutinib in relapsed CLL. This differentiates ibrutinib (and perhaps BTKi in general) from other targeted therapy paradigms for treatment-naïve CLL. Similar to prior studies, rates of afib and HTN continue to increase with time on therapy. These data support the use of ibrutinib as initial therapy in CLL, and strengthen the rationale for use of ibrutinib for high risk disease. Support: U10CA180821, U10CA180882, U24CA196171, https://acknowledgments.alliancefound.org, Pharmacyclics, Inc Figure 1 Figure 1. Disclosures Woyach: Gilead Sciences Inc: Other: Data & Safety; AbbVie Inc, ArQule Inc, Janssen Biotech Inc, AstraZeneca, Beigene: Other: Advisory Committee; AbbVie Inc, Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Research Funding; AbbVie Inc, ArQule Inc, AstraZeneca Pharmaceuticals LP, Janssen Biotech Inc, Pharmacyclics LLC, an AbbVie Company,: Consultancy. Ruppert: Telios Pharma: Consultancy. Ding: Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; DTRM: Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees. Bartlett: ADC Therapeutics: Consultancy, Research Funding; Roche/Genentech: Consultancy; Seagen: Consultancy, Research Funding; Autolus: Research Funding; Bristol Myers Squibb: Research Funding; Celgene: Research Funding; Forty Seven: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Kite, a Gilead Company: Research Funding; Merck: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding. Brander: Pfizer: Consultancy, Other: Biosimilars outcomes research panel; Genentech: Consultancy, Research Funding; Verastem: Consultancy; Juno Therapeutics/Celgene/Bristol Myers Squibb: Research Funding; LOXO: Research Funding; TG Therapeutics: Consultancy, Research Funding; MEI Pharma: Research Funding; NCCN: Other: panel member; ArQule/Merck: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; DTRM: Research Funding; BeiGene: Research Funding; AstraZeneca: Research Funding; Ascentage: Research Funding; ArQule: Research Funding; AbbVie: Consultancy, Other: informCLL registry steering committee, Research Funding; Novartis: Research Funding. Barr: Seattle Genetics: Consultancy; Bristol Meyers Squibb: Consultancy; AstraZeneca: Consultancy; Beigene: Consultancy; Genentech: Consultancy; Abbvie/Pharmacyclics: Consultancy; Gilead: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; Janssen: Consultancy. Rogers: Pharmacyclics LLC: Consultancy; Innate Pharma: Consultancy; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy; Acerta Pharma: Consultancy; AbbVie Inc.: Consultancy, Research Funding; Janssen Pharmaceuticals, Inc: Research Funding; ovartis Pharmaceuticals Corporation: Research Funding. Parikh: Pharmacyclics, MorphoSys, Janssen, AstraZeneca, TG Therapeutics, Bristol Myers Squibb, Merck, AbbVie, and Ascentage Pharma: Research Funding; Pharmacyclics, AstraZeneca, Genentech, Gilead, GlaxoSmithKline, Verastem Oncology, and AbbVie: Membership on an entity's Board of Directors or advisory committees. Coutre: Acerta: Other: Data Safety Monitoring Committee, Research Funding; Genentech: 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; AstraZeneca: 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, Research Funding; Pharmacyclics: Consultancy, 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. Larson: Epizyme: Consultancy; Astellas: Consultancy, Research Funding; Gilead: Research Funding; CVS/Caremark: Consultancy; Takeda: Research Funding; Novartis: Research Funding; Rafael Pharmaceuticals: Research Funding; Cellectis: Research Funding. Erba: 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; 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. Litzow: Jazz: Other: Advisory Board; Pluristem: Research Funding; Actinium: Research Funding; Amgen: Research Funding; Astellas: Research Funding; AbbVie: Research Funding; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. Blachly: INNATE: Consultancy, Honoraria; KITE: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria. Owen: Genentech: Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Merck: Honoraria; Servier: Honoraria; Incyte: Honoraria; Pharmacyclics: Research Funding. Abramson: Bristol-Myers Squibb Company: Consultancy, Research Funding; C4 Therapeutics: Consultancy; Morphosys: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; EMD Serono: Consultancy; Genmab: Consultancy; Bluebird Bio: Consultancy; Kymera: Consultancy; BeiGene: Consultancy; Incyte Corporation: Consultancy; Astra-Zeneca: Consultancy; Allogene Therapeutics: Consultancy; Seagen Inc.: Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Genentech: Consultancy. Brown: Abbvie, Acerta/Astra-Zeneca, Beigene, Bristol-Myers Squibb/Juno/Celgene, Catapult, Eli Lilly, Genentech/Roche, Janssen, MEI Pharma, Morphosys AG, Nextcea, Novartis, Pfizer, Rigel: Consultancy; Invectys: Other: Data Safety Monitoring Committee Service; Gilead, Loxo/Lilly, SecuraBio, Sun, TG Therapeutics: Research Funding. Stone: Onconova: Consultancy; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Boston Pharmaceuticals: Consultancy; Bristol Myers Squibb: Consultancy; Jazz: Consultancy; Arog: Consultancy, Research Funding; Gemoab: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy; Janssen: Consultancy; Innate: 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; AbbVie: Consultancy; Actinium: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Aprea: Consultancy; Syros: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Agios: Consultancy, Research Funding; Celgene: Consultancy; Macrogenics: Consultancy. Byrd: Novartis, Trillium, Astellas, AstraZeneca, Pharmacyclics, Syndax: Consultancy, Honoraria; Vincerx Pharmaceuticals: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Newave: Membership on an entity's Board of Directors or advisory committees.

Background: Aggressive lymphoma arising in the setting of chronic lymphocytic leukemia (CLL), known as Richter's syndrome (RS), is associated with poor outcomes with standard of care therapies. There is limited capacity for PET-CT to distinguish patients (pts) who develop RS after ibrutinib (Mato Haematologica 2019). Data on outcomes of pts with RS having previously received ibrutinib is limited. Here we sought to determine if clinical characteristics associated with iwCLL criteria for progression (Hallek Blood 2018) predict the risk of RS and overall survival (OS) in pts treated with ibrutinib. Methods: We conducted a retrospective analysis of pts with CLL treated with ibrutinib from 2010-2019 at The Ohio State University. We identified pts that progressed after ibrutinib and classified the progression by 2018 iwCLL criteria. We then identified who developed RS on or after progression. Risk of developing RS was assessed through Fine and Gray model treating death as the competing risk. OS was measured from time of progression and estimated using Cox model. Results: We analyzed 559 pts who had received ibrutinib for CLL, and identified 179 pts who progressed per iwCLL criteria. 94% of the pts who progressed were relapsed/refractory prior to ibrutinib. 116 pts progressed on ibrutinib, and the median time to progression from ibrutinib start was 40.8 months (mos) (range: 0.2-103.9). 63 pts progressed after stopping ibrutinib due to an adverse event or development of a resistance mutation, and the median time to progression from ibrutinib start for these pts was 28.5 mos (range: 0.7-92.9). Of the 179 pts who progressed, 54 developed RS. Of these 54 pts; 83% had enlarging lymphadenopathy, 9% had an enlarging liver or spleen, 17% had constitutional symptoms, 31% had increasing lymphocytosis, 15%, 15%, and 2% had worsening thrombocytopenia, anemia, or neutropenia respectively. No pts had worsening of CLL in the bone marrow (BM) and 2% had new appearance of other organ involvement. As lymphadenopathy and lymphocytosis were the most common clinical features identified we analyzed them jointly; 61% had lymphadenopathy without lymphocytosis, 9% had lymphocytosis without lymphadenopathy, 22% had both, and 7% had neither. Among pts with RS, median time from progression to RS was 0.4 mos (range: 0-49.3). Nine pts had biopsy confirmed RS on the date of progression. Median time from ibrutinib start to RS was 27.8 mos (range: 0.7-92.9). We performed a univariable analysis to determine whether clinical signs of relapse were associated with subsequent risk of RS, and found that presence of lymphadenopathy without lymphocytosis at progression was significantly associated with risk of RS (HR 3.58, 95% CI 1.44-8.88, p=0.006) (Table 1, Figure 1A). To determine if there was an association between clinical features of progression and OS we evaluated all 179 pts that progressed; 72% had enlarging lymphadenopathy, 10% had an enlarging liver or spleen, 15% had constitutional symptoms, 46% had increasing lymphocytosis, 15%, 17%, and 2% had worsening thrombocytopenia, anemia, or neutropenia respectively, only 2% had worsening of CLL in the BM, and 1% had new appearance of other organ involvement. When analyzed jointly; 45% had lymphadenopathy without lymphocytosis, 20% had lymphocytosis without lymphadenopathy, 26% had both, and 9% had neither. Median OS from progression was 24.4 mos (95% CI: 18.6-45.5), while median OS from RS diagnosis was 4.0 mos (95% CI: 2.1-7.1). Median OS from progression was 15.2 mos (95% CI: 7.8-24.6), and 49.9 mos (95% CI: 20.0-NR) for the lymphadenopathy without lymphocytosis and the lymphocytosis without lymphadenopathy groups respectively (Figure 1B). On univariable analysis lymphadenopathy without lymphocytosis was associated with a shorter OS (Table 1). These findings were maintained on multivariable analysis, with lymphadenopathy without lymphocytosis remaining an independent predictor of OS (HR 2.12, CI 1.17-3.87, p=0.01). Conclusions: Here we show that pts who have received prior ibrutinib for CLL who progress with lymphadenopathy have a higher likelihood of having RS than those pts who progress without lymphadenopathy. Furthermore, pts who progressed with lymphadenopathy without lymphocytosis have a shorter OS. Our data suggests that consideration should be given to perform a biopsy to rule out RS in any pts progressing with lymphadenopathy after receiving ibrutinib therapy for CLL. Figure 1 Figure 1. Disclosures Kittai: Abbvie: Consultancy; Janssen: Consultancy; Bristol-Meyers Squibb: Consultancy. Bhat: Beigene: Consultancy; Onclive: Honoraria; AstraZeneca: Consultancy; Aptitude Health: Honoraria. Bond: Kite/Gilead: Honoraria. Byrd: Pharmacyclics LLC: Research Funding; Acerta Pharma: Research Funding; Genentech, Inc.: Research Funding; Janssen Pharmaceuticals, Inc.: Research Funding. Rogers: Genentech: Consultancy, Research Funding; Janssen: Research Funding; Abbvie: Consultancy, Research Funding; Novartis: Research Funding. Woyach: AbbVie Inc, ArQule Inc, Janssen Biotech Inc, AstraZeneca, Beigene: Other: Advisory Committee; AbbVie Inc, ArQule Inc, AstraZeneca Pharmaceuticals LP, Janssen Biotech Inc, Pharmacyclics LLC, an AbbVie Company,: Consultancy; Gilead Sciences Inc: Other: Data & Safety; AbbVie Inc, Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Research Funding.

Introduction: Our group and others have previously shown that the presence of complex karyotype (>/= 3 cytogenetic abnormalities) is an important prognostic factor in relapsed/refractory (RR) chronic lymphocytic leukemia (CLL) patients treated with ibrutinib (Woyach JCO 2017, Thompson Cancer 2015, Maddocks JAMA Oncology 2015). It has been shown recently that increasing karyotypic complexity is a prognostic marker (Baliakis Blood 2019), but whether this is relevant for patients treated with novel therapies is unclear. Here, we aimed to determine whether the degree of karyotypic complexity beyond the dichotomy of complex versus not is a prognostic variable for patients with CLL treated with ibrutinib. Methods: We conducted a retrospective analysis of all patients with CLL treated with ibrutinib as a single agent or in combination with a monoclonal anti-CD20 antibody (MOAB) from 2010 through 2019 at The Ohio State University. We included patients with both treatment-naïve (TN) and RR disease. To determine karyotype, cells were stimulated with mitogen cocktail (PWM/PMA/CpG-ODN) and analyzed according to standard laboratory procedures. FISH using probes for D13S319, D12Z3, ATM, and TP53 were done according to manufacturer's recommendations. PCR was used to determine IGHV mutational status. Cytogenetic testing was included in the analysis if done Results: We analyzed 561 patients with a median age of 65 (range 26-91). 86% were treated with ibrutinib monotherapy, 22% were TN, and median number of prior therapies was 2 (range 0-13). 96% had an ECOG performance status (PS) of 0 or 1. Median LDH, WBC, HgB and PLT were 213 U/L, 23.2 K/uL, 11.2 g/dL, and 115 K/uL respectively. With available data, del13q14, trisomy 12, del11q22, and del17p13 was present in 50%, 22%, 30%, and 29% of patients respectively; 74% of patients were IGHV unmutated. 63 patients were excluded from cytogenetic analyses as the test was not done during the specified time window. Of the 458 evaluable, 50% had >3 cytogenetic abnormalities including 30% with >5 abnormalities. After a median follow up of 55.5 months, for the entire cohort estimated median PFS was 61.6 months (95% CI 56.1-69.5), and estimated median OS was 95.4 months (95% CI 86.3-not reached). On univariable analysis, older age, RR status, higher ECOG PS and LDH, lower HgB and PLT, presence of del17p13 and increasing karyotypic complexity were found to be statistically significant predictors of worse PFS and OS. To illustrate the relationship between increasing karyotypic complexity and clinical outcome, Kaplan-Meier plots are provided grouping pts with 0-2, 3-4, and 5 or higher aberrations (Figure 1). Accounting for statistically and clinically important factors on multivariate analysis (MVA, Table 1), increasing karyotypic complexity continued to be a statistically significant predictor of both PFS (p=0.01, HR 1.08 (95% CI 1.02-1.15)) and OS (p=0.001, HR 1.14 (95% CI 1.05-1.23)). Del17p13 did not retain statistical significance independently of karyotypic complexity on MVA. The interaction effect between prior treatment status and karyotypic complexity term was not significant for OS (p=0.89) and PFS (p=0.46), suggesting the prognostic effect of karyotypic complexity is similar across TN and RR cohorts. Conclusions: In this single center retrospective analysis, we found that increasing karyotypic complexity predicts inferior survival for patients with CLL treated with ibrutinib. This highlights that it is not only important to dichotomize presence of complex karyotype as >3 abnormalities, but to describe the number of karyotypic abnormalities in subsequent studies. Disclosures Bond: Seattle Genetics: Honoraria. Byrd:Acerta Pharma: Research Funding; Trillium: Research Funding; Pharmacyclics LLC, an AbbVie Company, Janssen, Novartis, Gilead, TG Therapeutics: Other; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, Novartis, Janssen: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, BeiGene: Research Funding; Janssen: Consultancy; Leukemia and Lymphoma Society: Other; Novartis: Research Funding; Kartos Therapeutics: Research Funding; Vincera: Research Funding; Syndax: Research Funding. Rogers:AstraZeneca: Other: Travel; Abbvie, Acerta, AstraZeneca, Pharmacyclics: Consultancy; Abbvie, Genetech, Janssen: Research Funding. Woyach:Pharmacyclics: Consultancy, Research Funding; AbbVie: Research Funding; Janssen: Consultancy, Research Funding; Karyopharm: Research Funding; Morphosys: Research Funding; Loxo: Research Funding; Verastem: Research Funding.

Introduction: B cell activating factor receptor (BAFF-R) promotes the maturation and survival of normal and malignant B cells. VAY736 is a human investigational Fc-engineered afucosylated monoclonal antibody (mAb) targeting BAFF-R and enhancing NK-cell mediated antibody-dependent cellular cytotoxicity (ADCC). VAY736 demonstrated superior ADCC compared with anti-CD20 mAbs in the clinic and showed promising antileukemic activity in CLL preclinical models (McWilliams EM, et al. Blood Adv 2019;3:447-460). Although Bruton tyrosine kinase inhibitors such as ibrutinib and recently acalabrutinib have become the standard treatment for many patients (pts) with CLL, these agents require indefinite treatment and result in cumulative toxicity. Ibrutinib + VAY736 has synergy in preclinical studies prompting the hypothesis that this combination may deepen responses and allow pts to discontinue ibrutinib. Methods: This Phase Ib dose escalation/expansion trial (NCT03400176) of VAY736 + ibrutinib enrolled pts with R/R CLL who were receiving ibrutinib following relapse from another approved therapy and had either failed to achieve a CR after >1 y of ibrutinib treatment or had developed a mutation associated with resistance to ibrutinib. Pts received VAY736 IV at 0.3, 1, 3, or 9 mg/kg every 2 weeks + oral ibrutinib at 420 mg daily for 6 28-day cycles. After 6 cycles, pts with a CR discontinued VAY736 and received ibrutinib for an additional 2 cycles; a protocol amendment allowed all other pts to continue VAY736 + ibrutinib for an additional 2 cycles. Pts achieving CR and minimal residual disease (MRD)-negativity at Day 1 of Cycle 9 (C9D1) could discontinue ibrutinib at the investigator's discretion. The primary objective was to characterize the safety and tolerability of the combination and to determine the maximum tolerated dose (MTD)/recommended dose for expansion. Results: A total of 15 pts (median age: 65 years; ECOG PS 0: 93%) were treated by the data cutoff (June 9, 2020). Overall, 11 pts completed and 3 discontinued combination treatment (primarily due to disease progression); 1 pt remains on treatment. Most pts (73%) had an ibrutinib resistance mutation at baseline (mainly [82%] BTKC481) and 33% had received ≥4 prior regimens (median: 3, range: 1-5); median duration of prior ibrutinib was 4.1 y (range: 0.2-8.3). Baseline cytogenetics were (not mutually exclusive): 27% del(17)(p13.1), 80% unmutated IGHV, 80% stimulated complex karyotypes (≥3 abnormalities), 60% del(13)(q14), and 7% +12. No dose-limiting toxicities have been observed and the MTD has not been reached. A total of 14 (93%) pts experienced an AE regardless of cause. Four (27%) pts experienced AEs of grade ≥3, including decreased neutrophil count (n=3), hypophosphatemia (n=2), decreased white blood cell count, leukocytosis, increased lymphocyte count, hypertension, hypokalemia, and hypomagnesemia (n=1 each). The overall response at C9D1 was CR in 6 (40%) pts, SD in 4 (27%) pts, PD in 4 (27%) pts, and not assessed in 1 (7%) pt (still on treatment). The mean baseline CLL cells in bone marrow for the CR, SD, and PD groups were 27% (range: 0.8-60.6%), 13% (range: 2.5-27%), and 66% (range: 47-77.9%). Three (20%) pts with CR achieved MRD-negativity and were able to discontinue CLL-directed therapy including ibrutinib; they remained in CR for 1-16 months after ibrutinib discontinuation. The median percentage change from baseline in blood MRD was -92.8% (range: -100%; -16.7%; Figure 1) and in bone marrow MRD was -89.6% (range: -100%; -32.6%). Of the pts who had baseline ibrutinib-resistance mutations and C9D1 assessments, 1 pt (1/6) tested negative for ibrutinib-resistance mutations at C9D1. None of the pts who were ibrutinib-resistance mutation negative at baseline (4/4) developed mutations by C9D1. VAY736 concentration increased with dose, accumulated after repeated dosing in combination with ibrutinib, and achieved linear PK at 3 mg/kg or above. Tissue receptor occupancy was >99% for VAY736 doses of 3 mg/kg or above. Free BAFF was accumulated to steady state with no dose relationship. Conclusions: VAY736 + ibrutinib had an acceptable safety profile and demonstrated promising preliminary activity in pts with R/R CLL on ibrutinib, providing clinical evidence of a potential to discontinue ibrutinib by VAY736 add-on therapy. Further investigation of this combination including in pts on 1st line ibrutinib and other ibrutinib combinations is ongoing. Disclosures Rogers: AstraZeneca: Consultancy, Other: Travel Funding; Janssen: Research Funding; AbbVie: Consultancy, Research Funding; Genentech: Research Funding; Acerta Pharma: Consultancy; Pharmacyclics: Consultancy. Flinn:Juno Therapeutics: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; MorphoSys: Consultancy, Research Funding; Curis: Research Funding; Nurix Therapeutics: Consultancy; BeiGene: Consultancy, Research Funding; Loxo: Research Funding; Calithera Biosciences: Research Funding; Celgene: Research Funding; Pfizer: Research Funding; Novartis: Research Funding; Vincera Pharma: Consultancy; Roche: Consultancy, Research Funding; Teva: Research Funding; TG Therapeutics: Consultancy, Research Funding; Trillium Therapeutics: Research Funding; Infinity Pharmaceuticals: Research Funding; Incyte: Research Funding; Takeda: Consultancy, Research Funding; IGM Biosciences: Research Funding; Johnson & Johnson: Other; Yingli Pharmaceuticals ≠: Consultancy, Research Funding; Verastem: Consultancy, Research Funding; Triphase Research & Development Corp.: Research Funding; Seattle Genetics: Consultancy, Research Funding; Portola Pharmaceuticals: Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Constellation Pharmaceuticals: Research Funding; Merck: Research Funding; AstraZeneca: Consultancy, Research Funding; Karyopharm Therapeutics: Research Funding; ArQule: Research Funding; Unum Therapeutics: Consultancy, Research Funding; Gilead Sciences: Consultancy, Research Funding; F. Hoffmann-La Roche: Research Funding; Curio Science: Consultancy; Acerta Pharma: Research Funding; Forma Therapeutics: Research Funding; Forty Seven: Research Funding; AbbVie: Consultancy, Research Funding; Kite Pharma: Consultancy, Research Funding; Rhizen Pharmaceuticals: Research Funding; Agios: Research Funding; Genentech, Inc.: Research Funding; Great Point Partners: Consultancy; Iksuda Therapeutics: Consultancy. McGarry:Novartis: Current Employment. Gou:Novartis: Current Employment. Hassounah:Novartis: Current Employment. Woo:Novartis: Current Employment. Byrd:Leukemia and Lymphoma Society: Other; Trillium: Research Funding; Novartis: Research Funding; Kartos Therapeutics: Research Funding; Janssen: Consultancy; Pharmacyclics LLC, an AbbVie Company, Janssen, Novartis, Gilead, TG Therapeutics: Other; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, Novartis, Janssen: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, BeiGene: Research Funding; Acerta Pharma: Research Funding; Syndax: Research Funding; Vincera: Research Funding.

Background Acalabrutinib is a highly selective second-generation Bruton's tyrosine kinase (BTK) inhibitor approved for the treatment of chronic lymphocytic leukemia (CLL) and mantle cell lymphoma. Ibrutinib, the first-generation nonselective BTK inhibitor, has been associated with cardiovascular (CV) complications including atrial fibrillation and ventricular arrhythmias, potentially related to off-target effects. In prior studies, the incidence of major adverse cardiovascular effects (MACE) with ibrutinib was 16.5-38%. With acalabrutinib being more selective, we postulate that less of these off-target effects would be seen. Although early experience with acalabrutinib suggests improved tolerability compared to ibrutinib, the long-term CV risks are unknown. Therefore, we sought to characterize the incidence, risk factors, and management of CV complications associated with acalabrutinib across long-term follow-up. Methods We performed a retrospective single-center cohort study of adult patients treated with acalabrutinib for a hematologic malignancy from January 2010 to August 2019. Patient demographics, CV and cancer variables, and CV complications were collected throughout the duration of acalabrutinib therapy. MACE was defined as cardiac arrhythmias (including atrial and ventricular arrhythmias), myocardial infarction, stroke, heart failure, and CV death. CV events, including arrhythmias, were graded according to the Common Terminology Criteria for Adverse Events (CTCAE), and adjudicated with an independent cardiologist. Descriptive statistics were used to summarize patient characteristics, using the mean ± standard deviation (SD) or median (interquartile range) for continuous variables and frequency counts with percentages for categorical variables. Time-to-event analysis methods were used to summarize MACE outcomes and evaluate associations with these outcomes. Results Overall, 290 patients treated with acalabrutinib were identified, majority had CLL (89%), and were male (72%) with a median age of 64 years. Seventy-seven (27%) patients were previously treated with ibrutinib. Sixty-seven percent of patients had a prior cardiac history, including 49% with baseline hypertension (HTN). MACE occurred in 18 patients (6%). Atrial fibrillation was the most common event occurring in 12 patients, followed by diastolic heart failure in 3 patients. There was one ventricular arrhythmic event (0.3%). Forty-four percent of patients temporarily held acalabrutinib during the MACE event, while 50% had no change to their acalabrutinib therapy. After the event, 6% of patients discontinued acalabrutinib and 11% of patients had dose reduced to 100mg daily. Age, gender, diabetes, kidney disease, and smoking status were found to be significantly associated with MACE. The odds of MACE were 1.8 times higher for every 7-year increase in age; when looking at just atrial fibrillation, the odds were 1.58 times higher for every 7-year increase in age. The effect of current smokers compared to never smokers was not significantly associated with MACE, however the odds of MACE were 3.4 higher in former smokers compared to never smokers. In comparison to ibrutinib (Dickerson, et al. Blood, 2019), the rate of MACE was lower- 66 vs 21 events per 1,000 person-years (P Conclusion In summary, acalabrutinib was associated with a lower, but significant risk of MACE compared to ibrutinib. The occurrence of these cardiac events appears to associate with worse survival outcomes. Further research into the mechanism(s) of these events, their implications, and the optimal preventative strategies for adverse CV complications after BTK inhibitor initiation is needed. Figure 1 Disclosures Blachly: AbbVie, AstraZeneca, KITE Pharma: Consultancy. Rogers:Genentech: Research Funding; Acerta Pharma: Consultancy; Pharmacyclics: Consultancy; AstraZeneca: Consultancy, Other: Travel Funding; Janssen: Research Funding; AbbVie: Consultancy, Research Funding. Byrd:Kartos Therapeutics: Research Funding; Trillium: Research Funding; Vincera: Research Funding; Novartis: Research Funding; Acerta Pharma: Research Funding; Syndax: Research Funding; Leukemia and Lymphoma Society: Other; Janssen: Consultancy; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, Novartis, Janssen: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company, Janssen, Novartis, Gilead, TG Therapeutics: Other. Woyach:AbbVie: Research Funding; Janssen: Consultancy, Research Funding; Karyopharm: Research Funding; Loxo: Research Funding; Morphosys: Research Funding; Pharmacyclics: Consultancy, Research Funding; Verastem: Research Funding.

CD19 is an attractive therapeutic target as it is highly expressed in CLL. Tafasitamab (Taf) is an Fc-engineered, humanized anti-CD19 monoclonal antibody with efficacy in CLL as a single agent. Compared to non-engineered antibodies, Taf shows significantly increased antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis, and direct cytotoxic effects (apoptosis) on tumor cells. With the addition of lenalidomide (Len), ADCC can be further augmented in vitro. Given the potential synergy of these agents, acceptable individual safety profiles, and efficacy as single agents, we conducted a study of Taf in combination with Len in patients (pts) with treatment-naïve (TN) and relapsed/refractory (RR) CLL, and included a pilot cohort of ibrutinib (IB)-treated pts with resistance mutations, but no clinical relapse, with Taf added to IB. We present the final results of this single institution phase II trial. In combination with Len, Taf was given at a dose of 1 mg/kg on cycle(C) 1 day(D) 1, 9 mg/kg on C1 D 2, 8, 15, and 22, and D1 of C2-12. Len 2.5 mg began daily on C1D8 and was given continuously. Len was escalated to 10 mg daily in pts without toxicity. After C12, Len could continue indefinitely in responding pts. In combination with IB, Taf was given at 1 mg/kg on C1D1, 12 mg/kg on C1 D2, 8, 15, and 22, weekly during C2-3, and every other week through C12. IB continued at 420 mg daily. The primary endpoint for Phase II was overall response rate (ORR) after C6. Based on previous studies with single agent Len, we tested whether the combination could improve ORR, from 50% to 80% in the TN cohort, and from 30% to 60% in the RR cohort. Using single stage designs, 19 pts per cohort provided at least 90% power to detect an increase in ORR (type I error rate 10%). By design, 13 and 9 responses were needed in the TN and RR cohorts, respectively, to warrant further study. A secondary endpoint was ORR after 12 cycles of therapy. Twelve pts were enrolled in the TN cohort; median age was 62 (range 44-75). Six pts were Rai stage III/IV, and 1 had both del(17p) and del(11q). Nine pts had ZAP 70-methylated disease. After C6, ORR was 67% [1 complete response (CR), 7 partial responses (PR); 90% confidence interval (CI): 39-88]; responses remained the same after C12. Three pts completed treatment per protocol, 3 discontinued treatment for progressive disease (PD) and 6 for AEs. Thirteen pts were enrolled in the RR cohort, median age was 70 (range 62-75). Eight pts were Rai stage III/IV, 4 had del(17p) and 2 had del(11q). Eleven pts had ZAP 70-methylated disease. After C6, ORR was 15% (all PRs - 90% CI: 3-41), and responses improved to 38% after C12 (90% CI: 17-65). Additional 1 pt had stable disease (SD). Five pts completed treatment per protocol, 6 discontinued treatment for PD, 1 for alternative therapy, and 1 continues on treatment. Nine pts with molecular progression on IB were enrolled; median age was 62 (range 45-87). Seven pts had del(17p) and 1 pt had del(11q). Eight pts had ZAP 70-methylated disease. After C6, only 1 pt (11%) responded with a PR; 3 additional pts had SD. Two pts completed treatment per protocol criteria, 3 discontinued treatment for AEs, 2 for alternative therapy and 1 pt each for PD and increased C481S allelic frequency. Figure shows Progression-free Survival (PFS) and Overall Survival (OS) for the 3 cohorts. Taf plus Len was well tolerated. Grade(gr)≥3 AEs included: infections [4: I each of lung infection, sinusitis, upper respiratory tract infection (URTI) and appendicitis], decreased neutrophil count (3) and infusion related reactions (2) in TN pts and decreased neutrophil count (10), infections [7: 2 catheter related urinary tract infections, 1 each with URTI, lung infection and soft tissue infection, 2 unspecified], diarrhea (3), hyponatremia (3) and hypophosphatemia (3) in RR pts. In the Taf plus IB cohort most common gr≥3 AEs included infections (4: 2 lung infections, 1 URTI and I unspecified), hyperglycemia (3) and hyponatremia (3). Gr≥3 atrial fibrillation was seen in 1 pt. In conclusion, although the trial did not fully accrue as planned, Taf in combination with Len appeared safe and demonstrated promising activity in TN CLL, warranting further investigation, and has similar efficacy to rituximab plus Len in RR CLL. Taf plus IB was less effective in pts with resistance to IB. Disclosures Blachly: AbbVie, AstraZeneca, KITE Pharma: Consultancy. Rogers:AbbVie: Consultancy, Research Funding; Genentech: Research Funding; Janssen: Research Funding; Pharmacyclics: Consultancy; Acerta Pharma: Consultancy; AstraZeneca: Consultancy, Other: Travel Funding. Lozanski:Genentech, Novartis, Beckman Coulter: Research Funding. Byrd:Syndax: Research Funding; Vincera: Research Funding; Acerta Pharma: Research Funding; Novartis: Research Funding; Kartos Therapeutics: Research Funding; Trillium: Research Funding; Leukemia and Lymphoma Society: Other; Janssen: Consultancy; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company, Gilead, TG Therapeutics, Novartis, Janssen: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company, Janssen, Novartis, Gilead, TG Therapeutics: Other. Woyach:Karyopharm: Research Funding; Morphosys: Research Funding; Pharmacyclics: Consultancy, Research Funding; Verastem: Research Funding; AbbVie: Research Funding; Janssen: Consultancy, Research Funding; Loxo: Research Funding. OffLabel Disclosure: Lenalidomide off label use for CLL

Variant hairy cell leukemia (vHCL) is an uncommon disorder accounting for 10% of all HCL cases [1]. The difference in therapeutic response to chemotherapy between patients with classic HCL (cHCL) a...

Ibrutinib is a highly effective targeted therapy for chronic lymphocytic leukemia (CLL). However, ibrutinib must be discontinued in a subset of patients due to progressive CLL or transformation to aggressive lymphoma (Richter transformation). Transformation occurs early in the course of therapy and has an extremely poor prognosis. Thus, identification of prognostic markers associated with transformation is of utmost importance. Near-tetraploidy (4 copies of most chromosomes within a cell) has been reported in various lymphomas, but its incidence and significance in CLL has not been described. Using fluorescence in situ hybridization, we detected near-tetraploidy in 9 of 297 patients with CLL prior to beginning ibrutinib treatment on 1 of 4 clinical trials (3.0%; 95% confidence interval [CI], 1.4%-5.7%). Near-tetraploidy was associated with aggressive disease characteristics: Rai stage 3/4 ( P = .03), deletion 17p ( P = .03), and complex karyotype ( P = .01). Near-tetraploidy was also associated with ibrutinib discontinuation due to Richter transformation ( P P = .41). Of the 9 patients with near-tetraploidy, 6 had Richter transformation with diffuse large B-cell lymphoma. In a multivariable model, near-tetraploidy (hazard ratio [HR], 8.66; 95% CI, 3.83-19.59; P P = .01) were independent risk factors for discontinuing ibrutinib due to transformation. Our results suggest that near-tetraploidy is a potential prognostic marker for Richter transformation to assess in patients going on ibrutinib.

Purpose Therapeutic targeting of Bruton tyrosine kinase (BTK) with ibrutinib in chronic lymphocytic leukemia has led to a paradigm shift in therapy, and relapse has been uncommon with current follow-up. Acquired mutations in BTK and PLCG2 can cause relapse, but data regarding the prevalence and natural history of these mutations are limited. Patients and Methods Patients accrued to four sequential studies of ibrutinib were included in these analyses. Deep sequencing for BTK and PLCG2 was performed retrospectively on patients who experienced relapse and prospectively on a screening population. Results With a median follow-up time of 3.4 years, the estimated cumulative incidence of progression at 4 years is 19% (95% CI, 14% to 24%). Baseline karyotypic complexity, presence of del(17)(p13.1), and age less than 65 years were risk factors for progression. Among patients who experienced relapse, acquired mutations of BTK or PLCG2 were found in 85% (95% CI, 71% to 94%), and these mutations were detected an estimated median of 9.3 months (95% CI, 7.6 to 11.7 months) before relapse. Of a group of 112 patients examined prospectively, eight patients have experienced relapse, and all of these patients had acquired resistance mutations before relapse. A resistance mutation was detected in an additional eight patients who have not yet met criteria for clinical relapse. Conclusion Relapse of chronic lymphocytic leukemia after ibrutinib is an issue of increasing clinical significance. We show that mutations in BTK and PLCG2 appear early and have the potential to be used as a biomarker for future relapse, suggesting an opportunity for intervention.

PURPOSE: Venetoclax-based therapy is a standard-of-care option in first-line and relapsed/refractory chronic lymphocytic leukemia (CLL). Patient management following venetoclax discontinuation remains nonstandard and poorly understood. EXPERIMENTAL DESIGN: To address this, we conducted a large international study to identify a cohort of 326 patients who discontinued venetoclax and have been subsequently treated. Coprimary endpoints were overall response rate (ORR) and progression-free survival for the post-venetoclax treatments stratified by treatment type [Bruton’s tyrosine kinase inhibitor (BTKi), PI3K inhibitor (PI3Ki), and cellular therapies]. RESULTS: We identified patients with CLL who discontinued venetoclax in the first-line (4%) and relapsed/refractory settings (96%). Patients received a median of three therapies prior to venetoclax; 40% were BTKi naïve (n = 130), and 81% were idelalisib naïve (n = 263). ORR to BTKi was 84% (n = 44) in BTKi-naïve patients versus 54% (n = 30) in BTKi-exposed patients. We demonstrate therapy selection following venetoclax requires prior novel agent exposure consideration and discontinuation reasons. CONCLUSIONS: For BTKi-naïve patients, selection of covalently binding BTKis results in high ORR and durable remissions. For BTKi-exposed patients, covalent BTK inhibition is not effective in the setting of BTKi resistance. PI3Kis following venetoclax do not appear to result in durable remissions. We conclude that BTKi in naïve or previously responsive patients and cellular therapies following venetoclax may be the most effective strategies.

This single-arm, open-label, phase 1b study evaluated the maximum tolerated dose (MTD) of venetoclax when given with obinutuzumab and its safety and tolerability in patients with relapsed/refractory (R/R) or previously untreated (first line [1L]) chronic lymphocytic leukemia (CLL). Venetoclax dose initially was escalated (100-400 mg) in a 3 + 3 design to define MTD combined with standard-dose obinutuzumab. Patients received venetoclax (schedule A) or obinutuzumab (schedule B) first to compare safety and determine dose/schedule for expansion. Venetoclax-obinutuzumab was administered for 6 cycles, followed by venetoclax monotherapy until disease progression (R/R) or fixed duration 1-year treatment (1L). Fifty R/R and 32 1L patients were enrolled. No dose-limiting toxicities were observed. Safety, including incidence of tumor lysis syndrome (TLS), did not differ between schedules (2 laboratory TLSs per schedule). Schedule B and a 400-mg dose of venetoclax were chosen for expansion. The most common grade 3-4 adverse event was neutropenia (R/R, 58% of patients; 1L, 53%). Rates of grade 3-4 infections were 29% (R/R) and 13% (1L); no fatal infections occurred in 1L. All infusion-related reactions were grade 1-2, except for 2 grade 3 events. No clinical TLS was observed. Overall best response rate was 95% in R/R (complete response [CR]/CR with incomplete marrow recovery [CRi], 37%) and 100% in 1L (CR/CRi, 78%) patients. Rate of undetectable (

BACKGROUND: Ibrutinib has been approved by the Food and Drug Administration for the treatment of patients with untreated chronic lymphocytic leukemia (CLL) since 2016 but has not been compared with chemoimmunotherapy. We conducted a phase 3 trial to evaluate the efficacy of ibrutinib, either alone or in combination with rituximab, relative to chemoimmunotherapy. METHODS: Patients 65 years of age or older who had untreated CLL were randomly assigned to receive bendamustine plus rituximab, ibrutinib, or ibrutinib plus rituximab. The primary end point was progression-free survival. The Alliance Data and Safety Monitoring Board made the decision to release the data after the protocol-specified efficacy threshold had been met. RESULTS: A total of 183 patients were assigned to receive bendamustine plus rituximab, 182 to receive ibrutinib, and 182 to receive ibrutinib plus rituximab. Median progression-free survival was reached only with bendamustine plus rituximab. The estimated percentage of patients with progression-free survival at 2 years was 74% with bendamustine plus rituximab and was higher with ibrutinib alone (87%; hazard ratio for disease progression or death, 0.39; 95% confidence interval [CI], 0.26 to 0.58; P

Ibrutinib is highly efficacious and used at 420 mg/d for treatment of chronic lymphocytic leukemia (CLL). We previously demonstrated a decline in Bruton’s tyrosine kinase (BTK) protein levels in CLL cells after 1 cycle of ibrutinib, suggesting ibrutinib dose could be lowered after the first cycle without loss of biological effect. To test this postulate, a pilot study (NCT02801578) was designed to systematically reduce ibrutinib dosing within the same patient with CLL over the course of three 28-day cycles. After an initial cycle of 420 mg/d, the dose was reduced to 280 mg/d in cycle 2, and then to 140 mg/d in cycle 3. Eleven patients began study treatment, and 9 completed the 3 cycles. Plasma and intracellular pharmacokinetics (PK), BTK occupancy, and pharmacodynamic (PD) response at different doses of ibrutinib were compared. Plasma and intracellular levels of ibrutinib were dose-dependent, and even the lowest dose was sufficient to occupy, on average, more than 95% of BTK protein. In concert, BTK downstream signaling inhibition was maintained with 140 mg/d ibrutinib in cycle 3, and there were comparable reductions in total and phospho-BTK (Tyr223) protein levels across 3 cycles. Reductions of plasma chemokine CCL3 and CCL4 levels, considered to be biomarkers of ibrutinib response, were similar during the 3 cycles. These PK/PD data demonstrate that after 1 cycle of ibrutinib at the standard 420 mg/d dose, the dose can be reduced without losing biological activity. Clinical efficacy of lower doses needs to be systematically evaluated. Such dose reductions would lower drug cost, lessen untoward toxicity, and facilitate rationale-based combinations. This trial was registered at www.clinicaltrials.gov as #NCT02801578.

Chronic lymphocytic leukemia (CLL) is frequently complicated by secondary autoimmune cytopenias (AICs). Ibrutinib is an irreversible inhibitor of Bruton's tyrosine kinase approved for the treatment of relapsed CLL and CLL with del(17p). The effect of ibrutinib treatment on the incidence of AIC is currently unknown. We reviewed medical records of 301 patients treated with ibrutinib, as participants in therapeutic clinical trials at The Ohio State University Comprehensive Cancer Center between July 2010 and July 2014. Subjects were reviewed with respect to past history of AIC, and treatment-emergent AIC cases were identified. Before starting ibrutinib treatment, 26% of patients had experienced AIC. Information was available for a total of 468 patient-years of ibrutinib exposure, during which there were six cases of treatment-emergent AIC. This corresponds to an estimated incidence rate of 13 episodes for every 1000 patient-years of ibrutinib treatment. We further identified 22 patients receiving therapy for AIC at the time ibrutinib was started. Of these 22 patients, 19 were able to discontinue AIC therapy. We found that ibrutinib treatment is associated with a low rate of treatment-emergent AIC. Patients with an existing AIC have been successfully treated with ibrutinib and subsequently discontinued AIC therapy.

e19354 Background: Ibrutinib (Ibr) is an established standard of care in CLL/SLL patients across lines, regardless of age, comorbidities and risk status. With the introduction of venetoclax (Ven) in the treatment landscape, there is a need to understand the real-world treatment sequencing of targeted oral agents, and the implication of sequencing on HRU/costs. This retrospective study evaluated HRU/costs associated with Ven treatment in various sequencing scenarios, including prior use of Ibr. Methods: Optum Clinformatics Extended DataMart De-Identified Databases (4/11/2015-6/30/2019) were used to identify adults with CLL/SLL treated with Ven (excluding investigational combination therapies). The index date was the start of the first Ven-based line of therapy (index LOT) and the baseline period was the 12-month period pre-index. Mean all-cause HRU/costs per patient per month (PPPM) were calculated during the index LOT and the Ven ramp-up period (first 30 days post-index). Results: Among a total of 11,861 CLL/SLL patients receiving ≥1 LOT, 121 patients (1.0%) were treated with Ven, including 25 patients (64.0% single agent) using Ven in first line (1L cohort), 30 (90.0% single agent) in second line (2L cohort), and 66 (83.3% single agent) in third line or later (3L+ cohort). Mean age was 71.6 years; 33.1% were female; mean baseline Quan-Charlson Comorbidity Index score was 4.7; median follow up from the start of 1L was 25.3 months; median duration of index LOT was 4.2 months. The majority of 2L+ Ven patients were previously treated with Ibr (2L: 56.7%, 3L+: 74.2%). Patients in all 3 cohorts had frequent outpatient (OP) visits PPPM during their index LOT (1L: 4.58; 2L: 4.75; 3L+: 5.71). Total costs PPPM during the index LOT were highest in the 1L cohort (1L: $21,762; 2L: $17,697; 3L+: $20,900), driven by higher OP costs (1L $9,402; 2L: $5,633; 3L+: $7,701). Increased total costs PPPM were observed during Ven ramp-up (1L: $31,707; 2L: $21,036; 3L+: $25,362). Compared to the overall 2L cohort, those treated with Ibr in 1L had lower total costs PPPM (index LOT: $15,350; V ramp-up: $15,882). Conclusions: In this descriptive study, the highest costs PPPM were observed for Ven treatment in the 1L. Prior treatment with Ibr was common among 2L and 3L+ CLL/SLL patients treated with Ven. Among 2L Ven patients, those previously treated with Ibr in 1L had $2,347 and $5,154 lower costs PPPM during 2L and Ven ramp-up, respectively, suggesting that previous Ibr treatment may help reduce costs in subsequent V treatment.

8004 Background: While therapeutic options for CLL have improved, patients (pts) who develop Richter’s Syndrome (RS) still have a poor prognosis. Chemoimmunotherapy regimens such as R-EPOCH lead to CR in about 20% of RS pts, but PFS/OS is typically < 6 mo. The oral Bcl-2 inhibitor venetoclax (ven) had a 43% single agent response rate in RS. Here, we report the results of a phase 2 study of VR-EPOCH in RS. Methods: This is a single-arm, phase 2, IST of VR-EPOCH for RS (NCT03054896) at 3 US sites. CLL pts with biopsy-confirmed DLBCL were treated with R-EPOCH for 1 cycle, then after count recovery underwent accelerated inpatient ven daily ramp-up (20/50/100/200/400 mg), then ven + R-EPOCH for up to 5 more 21d cycles (ven 400 mg qd, d1-10 each cycle). Responders went to alloHCT or to continuous daily ven 400 mg maintenance. Response evaluation by Lugano criteria with PET/CT. Results: As of the data cut on 2/3/2020, the study is fully enrolled with 27 pts. Median age: 63 yrs (range 49-77). CLL features: 26% del(17p); 44% complex karyotype; 48% IGHV unmutated; 41% TP53 and 15% NOTCH1 mutation. Median prior CLL treatments: 2 (range 0-5, prior ibrutinib [n = 8], ven [n = 2], and PI3Ki [n = 2]) with 6 untreated CLL pts. Median # ven + R-EPOCH cycles: 4 (range 0-6). 5 pts had dose de-escalation of R-EPOCH, 1 pt had dose escalation. ≥Gr 3 heme tox: neutropenia (58%), anemia (50%), thrombocytopenia (50%). ≥Gr 3 non-heme tox in > 15% of pts: febrile neutropenia (38%) and hypophosphatemia (23% each). No pts had TLS with daily ven ramp-up. Infections: pneumonia (n = 4), sepsis during C1 of R-EPOCH prior to starting ven (n = 3), enterocolitis (n = 3), sinusitis (n = 2), and 1 pt each with influenza A and norovirus. 10 pts have died, including 7 due to disease progression (2 during C1 before ven), and 1 each due to sepsis, sudden death, and GVHD post-alloHCT. In ITT analysis, 16 responded (ORR 59%); 13/27 (48%) had CR as best response, all with undetectable bone marrow MRD for CLL. Six pts were not evaluable for efficacy of the combo (5 had toxicity in C1 and never started ven, 1 withdrew after C1). In the 21 pts who started combo therapy, the ORR was 76%, CR rate 62%. Only 1 pt with CR has progressed. The pt on longest ven maintenance is in CR 2 years post chemo. 8 pts went to alloHCT, with pts still in CR now up to 2.5 yrs post-alloHCT. With a median follow-up of 9.3 mo (range 0.6-30), median PFS and OS are both 16.3 mo. Conclusions: VR-EPOCH is active for RS. Expected toxicities from intensive chemoimmunotherapy and ven were seen, but daily ven ramp-up was feasible. The 48% CR rate and median PFS of 16.3 mo are favorable in the context of historical results. Clinical trial information: NCT03054896 .

The Bruton tyrosine kinase inhibitor (BTKi) ibrutinib has transformed chronic lymphocytic leukemia (CLL) therapy but requires continuous administration. These factors have spurred interest in combination treatments. Unlike with chemotherapy, CD20-directed antibody therapy has not improved the outcome of BTKi treatment. Whereas CD20 antigen density on CLL cells decreases during ibrutinib treatment, the B-cell activating factor (BAFF) and its receptor (BAFF-R) remain elevated. Furthermore, BAFF signaling via noncanonical NF-κB remains elevated with BTKi treatment. Blocking BAFF interaction with BAFF-R by using VAY-736, a humanized defucosylated engineered antibody directed against BAFF-R, antagonized BAFF-mediated apoptosis protection and signaling at the population and single-cell levels in CLL cells. Furthermore, VAY-736 showed superior antibody-dependent cellular cytotoxicity compared with CD20- and CD52-directed antibodies used in CLL. VAY-736 exhibited in vivo activity as a monotherapy and, when combined with ibrutinib, produced prolonged survival compared with either therapy alone. The in vivo activity of VAY-736 is dependent upon immunoreceptor tyrosine–based activation motif (ITAM)–mediated activation of effector cells as shown by using an ITAM-deficient mouse model. Collectively, our findings support targeting the BAFF signaling pathway with VAY-736 to more effectively treat CLL as a single agent and in combination with ibrutinib.

Background B-cell receptor signaling inhibition (BCRi) is an effective treatment (trtmt) for patients (pts) with chronic lymphocytic leukemia (CLL), but resistance develops. Venetoclax selectively inhibits anti-apoptotic protein B-cell lymphoma 2 (BCL-2), and has demonstrated efficacy in relapsed/refractory CLL pts, particularly after BCRi. Venetoclax is started at 20 mg daily and escalated weekly over 5 weeks to the goal dose to avoid acute tumor lysis syndrome. However, we observed that many pts with relapsed/refractory CLL relapsing on BCRi progress more quickly than this schedule allows; they may progress while still taking BCRi or vigorously after its discontinuation. Given the need to promptly attain goal venetoclax dose in this population, we developed a rapid dose escalation scheme for venetoclax and reviewed our experience to understand the feasibility, safety, and efficacy of this approach in a properly equipped university setting. Methods We retrospectively evaluated adult pts with relapsed/refractory CLL presenting to The Ohio State University who were treated with a "rapid dose escalation" of venetoclax. Charts were reviewed for previous and concomitant CLL treatments, tumor burden, prognostic factors, performance status, and co-morbidities. Venetoclax dosing was planned for a shorter time period than the 5 weeks described in the label dosing. The dose was increased as quickly as tolerated following the customary doses (20mg, 50mg, 100mg, 200mg, then 400mg). We reviewed the evaluated safety and efficacy outcomes with this approach. Results We treated 34 pts with rapid venetoclax dose escalation. Median age at venetoclax start was 54 years old and were 73.5% men. Pts had a median of 5 previous CLL trtmts (range 2-18). The most recent trtmt was single-agent BCRi in 18 cases, which overlapped with venetoclax in the majority. Only 6 pts had high tumor burden and the majority had low or medium tumor burden. Cytogenetic abnormalities at venetoclax start included: 17 (50.0%) pts with 17p deletion, 5 (14.7%) with 13q deletion, 6 (17.6%) with 11q deletion, and 3 (8.8%) with trisomy 12. Fifty percent of pts had a complex karyotype, and 76.5% had unmutated IGVH status. 24 (80%, n=30 pts that had testing done) pts had confirmed BTK/PLCу2 mutations. The mean time to goal venetoclax dose was 9.6 days (range 4-31); all but 1 pt reached goal dose. Eighteen (52.9%) pts developed tumor lysis syndrome (TLS) by lab criteria at doses from 20-400 mg, 5 pts developed TLS by clinical criteria, and 1 pt experienced grade 3 severity TLS (per Cairo-Bishop definition). Only 4 pts had an elevated uric acid requiring rasburicase. Seventy-three percent of pts achieved at least a partial remission, and 4 pts each had stable or progressive disease. Three pts died within 30 days: 1 from uncontrolled bleeding and neutropenia, 1 due to neutropenic sepsis with invasive fungal infection and gastric perforation, and 1 due to neutropenic septic shock and respiratory failure. Time to best response was mean 50.7 days (range 2-428). Median time to subsequent trtmt was 279.5 days (range 73-430). 23 pts (67.6%) had not progressed at 1 year, and 26 (76.5%) were surviving at 1 year. Conclusion/summary Rapid dose escalation of venetoclax in this pt population is safe and feasible. Despite a high percentage of patients developing TLS (52.9%), all patients recovered without lasting complications and all but one were able to achieve the goal dose of venetoclax. This dosing scheme achieved disease control with 67.6% remaining progression-free at 1 year and the majority of pts surviving. It is reasonable to implement venetoclax rapid dose escalation in the proper hospital setting with ample ancillary support. This approach may be needed for CLL patients with rapidly progressive disease on BCRi. Disclosures Dotson: Abbvie: Consultancy. Bhat:Pharmacyclics: Consultancy; Janssen: Consultancy. Byrd:Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Acerta: Research Funding; BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Genentech: Research Funding; Acerta: Research Funding; BeiGene: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau. 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. Awan:Genentech: Consultancy; Sunesis: Consultancy; Gilead: Consultancy; Abbvie: Consultancy, Speakers Bureau; Janssen: Consultancy; Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy, Speakers Bureau. Rogers:AbbVie: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Acerta Pharma: Consultancy. OffLabel Disclosure: Venetoclax- we will be suggesting a faster increase from starting to maximum/goal dose than the dosing label recommends. This is in order to achieve faster disease control.

Introduction Blocking Bruton tyrosine kinase (BTK) with ibrutinib has demonstrated efficacy in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL) patients (pts). However, resistance to therapy is common. Preclinical data suggest selinexor (oral selective inhibitor of nuclear export) downregulates BTK (Hing 2015). We hypothesized that dual BTK blockade by combining ibrutinib and selinexor would be tolerable and efficacious in CLL/NHL pts. Herein, we report the phase I combination study with expansion cohorts. Methods Pts with histologically confirmed CLL/NHL were enrolled (n=33). Eligible pts were age ≥18 years (yrs), had ≥1 prior therapy and ECOG performance status of 0-1. CLL pts met iwCLL 2008 criteria for therapy. Pts received selinexor orally 1-2 times weekly (3 weeks of 4-week cycle) and daily oral ibrutinib (420mg) starting Cycle 1 Day 8. Treatment cycles were repeated until disease progression, intolerance, death or discontinuation of trial participation. Primary endpoint was determination of maximum tolerated dose (MTD). Dose-finding proceeded using a modified continual reassessment method targeting a probability of dose limiting toxicity (DLT) Results Median age was 66 yrs (50-80). Included pts had CLL (n=16), Richter's transformation (RT=8), diffuse large B-cell lymphoma (DLBCL, n=6), and mantle cell lymphoma (MCL=3). Median number of prior therapies was 4 (1-14) and 58% had received ibrutinib. Baseline characteristics are detailed in Table 1. The combination was tolerated. MTD was 40mg of selinexor (D1, 8, 15) and 420mg daily ibrutinib [dose level 1 (DL1)]. Two pts were treated with selinexor 30mg twice weekly and 420mg of daily ibrutinib (DL2) and both experienced significant fatigue and discontinued therapy. These adverse events (AE) were considered DLTs. The remainder of pts received DL1. Grade ≥3 hematologic AEs were rare with 3 (9%) and 1 (3%) pt experiencing neutropenia and anemia, respectively. Most common non-hematologic AEs of any grade were nausea (39%) diarrhea (33%), fatigue (33%), and anorexia (27%). Grade ≥3 non-hematologic AEs were uncommon with 2 pts (6%) experiencing hypertension and 1 pt each (3%) experiencing diarrhea, nausea, elevated alkaline phosphatase, cataract, weight gain, upper respiratory tract infection, pancreatitis, pneumonitis, and multi-system organ failure. Other AEs of interest were weight loss, bleeding, and tachycardia, experienced by 5 (15%), 4 (12%), and 3 (9%) pts, respectively. There were 5 pt deaths while on study; 3 related to disease progression and 2 related to infection. In total, 81% achieved disease control with 33% achieving CR or PR (partial response) and 48% achieving stable disease (SD; Table 2). All CLL pts who received prior ibrutinib or had complex karyotype achieved at least SD, and all who did not receive prior ibrutinib had CR or PR. Two CLL pts with known BTK mutation had response to therapy and 7 had SD. One CLL pt who received 1 prior therapy achieved CR with no detectable residual disease. One of the 8 RT pts achieved CR and 5 achieved SD. In the 11 pts who achieved at least PR, the median duration of response was not reached (NR). In the 15 pts with SD and >2 mos of follow-up, 20% (3/15) maintained SD for >6 mos. Median PFS for pts with CLL and NHL was 8.9 (95%CI:4.6-NR) and 2.7 (95%CI:0.7-NR) mos, respectively (Figure 1). For CLL pts who received and did not receive prior ibrutinib, 64% (7/11) and 20% (1/5) progressed, respectively. For CLL pts who received 1-2 and ≥3 prior therapies 20% (1/5) and 64% (7/11) progressed, respectively. With median follow-up of 5.3 (range:1.2-22.5) and 5.5 (range:0.7-33.1) mos, median OS for CLL and NHL pts was NR (95%CI:15.4-NR) and 5.4 (95%CI:2.6-NR) mos, respectively (Figure 2). Conclusions Ibrutinib (420mg daily) and selinexor (40mg weekly) was tolerable and demonstrated efficacy in this heavily pretreated, high-risk population of CLL/NHL pts. Efficacy may be greater in earlier lines of therapy. Further investigation is needed to optimize response rates and durability. Disclosures Stephens: Karyopharm: Research Funding; Gilead: Research Funding; Acerta: Research Funding. Rogers:Janssen: Research Funding; Acerta: Consultancy; Abbvie: Research Funding; Genentech: Research Funding. Bhat:Janssen: Consultancy; Pharmacyclics: Consultancy. William:Guidepoint Global: Consultancy; Defined Health: Consultancy; Techspert: Consultancy; Celgene Corporation: Consultancy; Kyowa Kirin, Inc.: Consultancy. Jaglowski:Kite: Consultancy, Other: advisory board, Research Funding; Novartis: Consultancy, Other: advisory board, Research Funding; Juno: Consultancy, Other: advisory board; Unum Therapeutics Inc.: Research Funding. Glenn:BMS: Research Funding; Merck: Research Funding; Genentech: Research Funding. Byrd:Genentech: Research Funding; Acerta: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Genentech: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Acerta: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; BeiGene: Research Funding; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau. 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. OffLabel Disclosure: Selinexor is an oral inhibitor of nuclear export. This presentation will describe the combination of ibrutinib and selinexor, which is an off-label use for the drug.

Background: Ibrutinib (ibr) for the treatment of chronic lymphocytic leukemia (CLL) has improved progression-free survival (PFS) compared to other treatments, especially in high-risk patients (pts). However, resistance occurs and is associated with mutations in the drug binding target (BTK) and its immediate downstream target (PLCg2). These ibr resistance mutations (IRmut) are detectable months prior to developing progressive disease (PD) and predict clinical relapse. Prospectively determining the time from starting ibr to development of IRmut and from IRmut detection to PD will improve our understanding of how to manage these patients. Venetoclax (ven) is highly effective after ibr and decreases IRmut. Adding ven to ibr for ibr resistance is a rational choice as this combination is safe and effective in CLL. Adding an agent rather than stopping ibr avoids disease flare associated with ibr discontinuation. This phase 2 study was designed to follow CLL pts taking ibr and at high risk for resistance (observation cohort) and to test ven in combination with ibr for those who develop PD (intervention cohort). This will determine: the incidence of IRmut and PD in this population, the ORR with ibr/ven, and the ability of this combination to eliminate IRmut. Trial Design and Methods: This multisite study will open at 4 centers initially. Eligible pts are adults with CLL taking ibr for ≥12 months and at high risk for ibr resistance defined as having ≥2 prior treatments and del(17p)(p13.1) on FISH panel and/or a complex karyotype. Pts with known IRmut or who cannot continue ibr for any reason are excluded. Enrolled pts enter the observation cohort and are followed every 3 months with a clinic visit, blood counts, and testing for IRmut. Pts who develop IRmut will also have CT scans at their visits to detect PD. Those with IRmut who develop PD by iwCLL 2018 criteria will enter the intervention cohort. Pts in the intervention cohort will start ven in addition to ibr. Ven will be ramped-up over 5 weeks to a target dose of 400mg. Pts will take combination ibr/ven for 12 cycles of 28 days in length. After 12 cycles they will undergo response assessment and those achieving a complete remission (CR) with no detectable leukemia (uMRD) in both the blood and bone marrow will stop ven and continue ibr alone. Those who do not achieve CR with uMRD will continue ibr/ven until cycle 24 and undergo a second response assessment. If in a CR with uMRD after 24 cycles they continue on ibr alone. If a CR with uMRD is not achieved after 24 cycles patients continue ibr/ven until PD, intolerance, death, or end of study which is 30 months after the last patient enters the intervention cohort (Figure). In the intervention cohort all pts will be tested for IRmut in the blood every 3 months with bone marrow testing at response assessments. The study has co-primary endpoints of ORR to combination ibr/ven after 12 cycles and the rate of IRmut negative status at that time in the intervention cohort. ORR will be tested first using a single-stage phase 2 design with a null hypothesis that the rate is ≤50% versus the alternative hypothesis that it is ≥75%. Only if the combination is effective in ORR will the rate of IRmut negative status be formally tested. Constraining overall Type I and II errors to 0.10 using this sequential testing strategy, 26 evaluable pts are required and 28 will be accrued. Secondary endpoints for the intervention cohort are the PFS and overall survival since starting the combination ibr/ven and the incidence and type of adverse events with ibr/ven. Secondary endpoints in the observation cohort are the incidence of IRmut during ibr treatment and the PFS after developing an IRmut. We estimate that 180 pt-years of follow up for the observation cohort will be needed. The yearly rate of mutation development in this population is approximately 20%, therefore this will identify 36 pts with IRmut. Of those with IRmut, approximately 80% will remain eligible to enter the intervention cohort. Accrual to the observation cohort will stop once 28 pts enter the intervention cohort. Conclusion: This multicenter phase 2 trial examines the development of IRmut and clinical resistance to ibr in a cohort of high-risk CLL pts and will determine the efficacy of adding ven to ibr in those who develop PD. We expect to determine the natural course of molecular and clinical ibr resistance in CLL and if adding ven is an effective treatment strategy. Figure Disclosures Rogers: Acerta: Consultancy; Genentech: Research Funding; Abbvie: Research Funding; Janssen: Research Funding. Bhat:Pharmacyclics: Consultancy; Janssen: Consultancy. Stephens:Karyopharm: Research Funding; Gilead: Research Funding; Acerta: Research Funding. Ye:Janssen: Research Funding; Karyopharm: Research Funding; Portola: Research Funding; MingSight: Research Funding; Sanofi: Research Funding. Byrd:Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Genentech: Research Funding; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; Novartis: Other: Travel Expenses, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; BeiGene: Research Funding; BeiGene: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding. 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. OffLabel Disclosure: This abstract discussion the use of combination ibrutinib and venetoclax in CLL.

Introduction:T cell engaging bispecific antibodies (T-BsAb) redirect cytotoxic T cells to tumor associated antigen (TAA)-positive target cells, leading to T-cell activation and lysis of target cells. Blinatumomab is the only T-BsAb approved by FDA. Numerous T-BsAb are undergoing clinical trials, targeting both hematological malignancies (e.g. BCMA, CD123 and CD33) and solid tumors (e.g. CEA, EpCAM, and GPC3). While these T-BsAbs represent a promising novel therapeutic approach, their efficacy remains modest. Ibrutinib is an irreversible inhibitor of Bruton's tyrosine kinase (BTK) and induces durable remissions in chronic lymphocytic leukemia (CLL). Our group has reported that ibrutinib has favorable immunomodulatory effects due to inhibition of interleukin-2 inducible T-cell kinase (ITK). Ibrutinib decreased key immunosuppressive checkpoint molecules and the frequency of regulatory T cells (Treg)(Long, Beckwith et al. 2017). Moreover, Ibrutinib significantly increased the number of the activated T cells by rescuing them from activation induced cell death (AICD). However, the function of ibrutinib 'rescued' T cells and their ability to mediate T-BsAb redirected cytotoxicity is unknown. Therefore we proceeded to study how ibrutinib treatment affects the functional competency of T cells by measuring their capability to mediate Blinatumomab redirected cytotoxicity. To examine T cell function post ibrutinib treatment, T cells were isolated from pre and post treatment PBMC samples by fluorescence activated cell sorting (FACS), and used as effector cells with pre-treatment CLL B-cells as target cells. Blinatumomab redirected T-cell cytotoxicity against tumor cells and T cell survival were assayed by flow cytometry based methods. Effector cells (T cells) were labeled with CFSE. Target (CLL) cells were labeled with CellTrace Violet. They were co-cultured at an E:T ratio of 4:1 with Blinatumomab for 24 hours. Effector cells and target cells can be distinguished by different fluorescence labels. Apoptosis and cell death were evaluated by Annexin-V and PI staining. The number of viable target cells and effector cells were calculated by Countbright counting bead. Results: We observed that post-ibrutinib T cells demonstrated significantly superior cytotoxicity against autologous CLL cells in the presence of blinatumomab in three independent patient samples. Numbers of viable CLL cells co-cultured with post-ibrutinib T cells were lower when compared to those co-cultured with pre-ibrutinib T cells (33.6%, 68% and 55.1% reduction in viable CLL cells for the three patient samples, respectively). We also found that Treg depletion (by depleting CD25high/CD127low CD4+ T cells) further enhanced cytotoxicity for both pre and post-ibrutinib treatment T cells, with the numbers of viable CLL cells reduced another 30-40%. Moreover, compared to pre-ibrutinib T cells, post-ibrutinib treatment T cells again demonstrated superior cytotoxicity when Treg cells were depleted, with decreased numbers of viable CLL cells at the end of co-culture (43%, 69% and 49.4% reduction, respectively). We also observed that the numbers of viable T cells from pre-ibrutinib samples were much lower than post-ibrutinib samples (52.5%, 77.9% and 74% reduction in viable T cells, respectively). Conclusions: Our findings suggest that ibrutinib-rescued T cells are functionally competent. CLL patients' T cells post ibrutinib treatment demonstrated superior cytotoxicity against autologous leukemia cells compared to T cells from treatment baseline. Moreover, we show that increased T cell activity is not solely due to ibrutinib-related Treg depletion. Treg depletion in our experiments further enhanced the cytotoxicity of both post and pre-ibrutinib treatment T cells while post-ibrutinib T cells still demonstrated superior cytotoxicity (Fig 1). Lastly, T cells isolated from post-ibrutinib samples demonstrated significantly improved viability after in-vitro stimulation with blinatumomab, which is likely a result of reduced AICD. Disclosures Bhat: Pharmacyclics: Consultancy; Janssen: Consultancy. Rogers:Janssen: Research Funding; AbbVie: Research Funding; Genentech: Research Funding; Acerta Pharma: 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. Muthusamy:Ohio State University: Patents & Royalties: OSU-2S. Byrd:Novartis: Other: Travel Expenses, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Genentech: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; BeiGene: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau.

Introduction Acalabrutinib (A) is a selective, second-generation irreversible Bruton's Tyrosine Kinase inhibitor (BTKi) that has shown outstanding clinical activity in chronic lymphocytic leukemia (CLL) and other hematologic malignancies. Acquired resistance to the first-generation BTKi, ibrutinib (I), is mediated most commonly by C481S mutations in BTK, which decrease binding affinity and change binding from irreversible to reversible. The mechanism of resistance to A has not been investigated. Patients and Methods All patients (pts) treated at The Ohio State University and enrolled on an IRB approved phase 1b/2 study in CLL were included in this analysis. Beginning 12 months (mos) after the initiation of A, pts underwent deep sequencing every 3-6 cycles using a digital droplet PCR assay for BTK C481S or Ion Torrent Sequencing for any BTK or PLCG2 mutations. At relapse, samples from each pt underwent full BTK and PLCG2 sequencing. Correlation between baseline characteristics and relapse was assessed using proportional sub-distribution hazards model, pts who were still on treatment were censored at last follow-up. Results 105 pts were included in this analysis. 38 (36%) were treatment-naïve (TN), 50 (48%) were relapsed/refractory (RR), and 17 (16%) were previously intolerant of I (intol). The median age was 62 (range 33-84) and median number of prior therapies was 1 (range 0-11). The pts were generally high-risk, with 66% having unmutated IGHV, 24% with del(11)(q22.3), 15% with del(17)(p13.1), and 28% with complex karyotype (≥ 3 abnormalities). With a median follow-up of 47.5 mos (range 37.7-58.5) 30% of pts (n=31) have discontinued therapy, 17 for progression of disease (CLL in 16 pts, Richter's transformation in 1), and 14 for other reasons. Cumulative incidence rate (CIR) of progression varied significantly by cohort. At 12 mos, CIR of progression ranged from 0% in both the TN and RR cohorts to 11.8% (95% CI 1.8-32%) in those who were intol. By 36 mos, CIR of progression was 5.3% (95% CI 0.9-15.7%) in TN cohort, 6% (95% CI 1.5-15%) in the RR cohort, and 35.3% (95% CI 13.7-58%) in the intol cohort (Figure 1). In univariable analysis, higher risk of progression was associated with del(17)(p13.1) on baseline FISH (p All 16 pts with CLL relapse had a sample evaluated for BTK C481S at relapse, and 14 had samples evaluated for full BTK and PLCG2 mutations using Ion Torrent deep sequencing. BTK C481 mutations were found in 11/16 (69%; C481S in 10, C481R and C481Y in 1). One pt with a BTK C481S mutation also had a BTK T474I gatekeeper mutation, and one had co-existing C481R mutation. Two pts with BTK C481S mutations had co-existing PLCG2 mutations previously associated with I resistance at 103/105 pts were screened every 3-6 cycles for BTK mutations. 22 pts have had mutations detected at a median of 31.6 mos from A initiation. TN and RR pts had median time to mutation of 38.8 and 32.9 mo, respectively. For intol pts median time to mutation detection was 24.8 mos from start of A, 33.8 mos from start of any BTKi. Median time from BTK mutation detection to clinical relapse is 12 mos (95% CI: 4.8-not reached), with no significant difference among cohorts in time from mutation to disease progression. Conclusions Here we show for the first time that CLL relapse on A is mediated predominantly by mutations in BTK similar to I. While not unexpected, this is significant as resistant patterns could be different given the more selective nature of A as well as potentially higher BTK occupancy over time due to twice daily dosing. Monitoring for BTK resistance offers the opportunity to intervene clinically before symptomatic disease. Disclosures 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. Rogers:AbbVie: Research Funding; Acerta Pharma: Consultancy; Genentech: Research Funding; Janssen: Research Funding. Bhat:Janssen: Consultancy; Pharmacyclics: Consultancy. Grever:Acerta Pharma, LLC: Membership on an entity's Board of Directors or advisory committees. Lozanski:Boehringer Ingelheim: Research Funding; Beckman Coulter: Research Funding; Stemline Therapeutics Inc.: Research Funding; Genentec: Research Funding. Byrd:Ohio State University: Patents & Royalties: OSU-2S; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Genentech: Research Funding; Genentech: Research Funding; Acerta: Research Funding; Acerta: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; 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; BeiGene: Research Funding; BeiGene: Research Funding.

Introduction: The Bruton's Tyrosine Kinase (BTK) inhibitor ibrutinib (IB) is a standard therapy for previously untreated CLL patients. While therapy is currently indicated only for patients with progressive, symptomatic disease, the introduction of targeted therapies in CLL has re-opened the question of whether asymptomatic high risk patients would benefit from early intervention. As well, even in early stages CLL is associated with profound cellular, humoral and innate immune suppression and patients with CLL respond poorly to routine vaccinations. IB has been shown to reverse disease mediated immune dysfunction partly through Th1 skewing. We undertook a phase 2 study of IB in asymptomatic high risk CLL patients who did not otherwise require therapy to evaluate: 1) the safety and efficacy of 2 years of IB in this clinical setting and 2) ability of IB to improve the efficacy of routine vaccines. Methods: This is a single-stage phase II study of IB in previously untreated asymptomatic, genetically high-risk patients with CLL, who did not meet IWCLL treatment criteria. High risk genomics were defined as del(11)(q22.3), del(17)(p13.1), unmutated IGHV, and/or complex karyotype (≥3 cytogenetic abnormalities). Patients were randomized to receive IB 420mg PO daily either concurrent with the pneumococcal (PCV13), influenza and TdaP vaccines (Arm A) or following vaccination (Arm B) for a total of 27 cycles (2 years). The primary objective of the study was to determine the safety and 2-year progression-free survival (PFS) of asymptomatic, high-risk CLL patients treated with IB. Secondary objectives include determination of safety and immune responses to vaccines in relation to IB administration, development of resistance, and quality-of-life (QOL). QOL measures assessed general QOL (SF-12, EORTC), anxiety (GAD-7) and depression (PHQ-9). Results: Forty-four patients (pts; 21 in Arm A, 23 in Arm B) were enrolled from 1/2016 to 6/2017, with a median age of 58 (range 35-82). Sixty-six percent of pts were male and all were high-risk: 91% with unmutated IGHV, 14% with del(17)(p13.1), 34% with del(11)(q22.3), and 24% with complex karyotype (≥ 3 abnormalities). Median follow-up is 2.6 years (range: 0.2-3.2). Excluding 2 patients in Arm B who progressed prior to receipt of IB, 2-year PFS was 92%. From a landmark of 2-years and including 33 patients who reached this point and discontinued IB, 6-month PFS was 87% (95% CI: 69-95%; Figure 1). Of 9 pts who progressed after IB discontinuation, 3 have not required further treatment, 5 restarted IB or acalabrutinib, and 1 started venetoclax/rituximab, and all responded. For PCV13, in Arm A, 15/16 patients showed a significant increase in antibody titer 2 cycles following vaccination, but response disappeared by cycle 12. In Arm B, 3/13 patients had an increase in antibody titer, with no increase following second vaccination. For influenza, patients in Arm B showed a significant response to influenza A vaccination, while patients in both arms responded to influenza B vaccination. IB was generally well tolerated, and only one pt discontinued treatment due to toxicity (atrial fibrillation). Grade 3+ toxicities that occurred in >2% of patients included anemia (7%), atrial fibrillation (11%), dental caries (7%), hyperglycemia (7%), hypertension (43%), and neutropenia (7%). At baseline, patients' reports of physical health-related (M=48.52, SD=7.96) and mental health-related quality of life (M=52.20, SD=8.57) similar to U.S population norms, along with moderately high global health (M=78.49 of 100, SD = 20.51). Additionally, patients' anxiety (M=3.56, SD=4.71) and depressive symptom reports (M=3.65, SD=4.46) were in the "none/mild" range. There was no significant change in the latter measure from baseline to 12 months (p>0.25), excepting anxiety which slightly decreased (M=1.31, SD=2.33; F(3,44)=5.94, p Conclusions Early intervention with IB was well tolerated and significantly improved patient disease status. Vaccine response to PCV13 was improved by concurrent ibrutinib, but lost at 12 months, suggesting re-vaccination might be helpful. Quality of life remained good throughout treatment, with improvement in patient anxiety. Extended follow-up will be required to determine how long remissions can be maintained after drug discontinuation in this population. Disclosures Woyach: Verastem: Research Funding; Loxo: Research Funding; Morphosys: Research Funding; Karyopharm: Research Funding; AbbVie: Research Funding; Janssen: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding. Rogers:AbbVie: Research Funding; Acerta Pharma: Consultancy; Genentech: Research Funding; Janssen: Research Funding. Bhat:Pharmacyclics: Consultancy; Janssen: Consultancy. Grever:Acerta Pharma, LLC: Membership on an entity's Board of Directors or advisory committees. Lozanski:Beckman Coulter: Research Funding; Stemline Therapeutics Inc.: Research Funding; Boehringer Ingelheim: Research Funding; Genentec: Research Funding. Byrd:TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Novartis: Other: Travel Expenses, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau. Awan:Gilead: Consultancy; Sunesis: Consultancy; Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Janssen: Consultancy; Genentech: Consultancy. OffLabel Disclosure: Clinical trial of ibrutinib used in an off-label setting

Introduction: Targeted irreversible Bruton's Tyrosine Kinase (BTK) inhibitors ibrutinib and acalabrutinib, have revolutionized treatment for chronic lymphocytic leukemia (CLL). While BTK inhibition (BTKi) achieves durable responses in 90% of patients, only 10% achieve minimal residual disease (MRD) negative status. MRD positive patients have persistent residual CD5+CD19+ tumor B cells at approximately 1-5 /mm3 in peripheral blood. These cells may represent a subpopulation of B-cell lymphocytosis pre-malignant cells or may carry a BTK C481, PLCG2, or other CLL mutation that is ultimately responsible for disease relapse. Alternatively, MRD could be derived from the original clones present at initial disease presentation that are not dependent on BTK signaling. Readily available clinical DNA sequencing and MRD monitoring techniques lack the ability to characterize these cells adequately due to their rarity in peripheral blood. To address this problem, we developed a novel method for limited-cells using fluorescence activated cell sorting in tandem with next generation sequencing (LC-FACSeq) to characterize rare tumor subpopulations in the blood and bone marrow. LC-FACSeq may be useful not only for CLL but also other leukemias. Methods: LC-FACSeq uses fluorescent activated cell sorting (FACS) to isolate pure populations of rare tumor cells after which targeted deep sequencing is performed to monitor CLL-related mutations in NOTCH1, SF3B1, and TP53, as well as genes associated with BTKi relapse and resistance: BTK and PLCG2. For validation of this method, we generated libraries from DNA isolated from FACS isolated bulk (n >15000) versus n= 50, 100, 300, or 500 CD5+/CD19+ cells from CLL patients (n=5). Results: All samples analyzed had an average read depth of 1212 (SEM=56) per gene and an average coverage uniformity of 88.24% (SEM=.01). We show that showed that 300-cell LC-FACSeq libraries demonstrated comparable variant calling and minimal noise to standard libraries generated from purified DNA from bulk cells. Using samples from patients with previously identified BTK C481S mutations, we found that both sensitivity and specificity of LC-FACSeq for BTK C481S was 100%. Furthermore, LC-FACSeq reliably amplified BTK C481S signals from subclones as small as 6 in 300 total cells (2%) when mutated tumor cells were serially diluted into BTK wild type tumor cells. In using LC-FACSeq to retrospectively analyze four independent patients who developed Ibrutinib resistance, we found that we could see the emergence of small BTKi resistant subclones as early as 10 months before clinical detection. We next extended LC-FACSeq to examine the clonal architecture of long-term (> 12 months) ibrutinib-treated MRD positive patients. Median treatment time was 5 years. BTK C481S mutations were observed in the latest available on-treatment samples of only one patient. Using LC-FACSeq we observed canonical CLL-associated clonal mutations similar to those observed in previous studies. Of the 14 MRD positive patients, 7 showed subclonal changes in TP53, NOTCH1, POT1, SF3B1, and MYD88 over the course of ibrutinib treatment although we found no correlation or consensus in these clonal shifts. Conclusion: LC-FACSeq is a highly sensitive method of characterizing clonal evolution in rare cells. Our data shows that LC-FACSeq is useful for monitoring sequential acquisition of mutations conferring therapy resistance and clonal evolution in long-term ibrutinib treated chronic lymphocytic leukemia (CLL) patients. We also observe that in most cases, MRD clones after long-term ibrutinib treatment are genetically similar to disease clones from pretreatment baseline. Compared to current MRD monitoring strategies, the main advantages of LC-FACSeq are that 1) variants can be confidently called from rare sorted tumor populations and subpopulations, 2) library generation can be completed in less than a day in a diagnostic laboratory compared to the labor-intensive protocols of traditional NGS approaches, and 3) amplicon panels can be easily customized for application to other types of leukemia and lymphoma. (EH is supported by the Graduate Pelotonia Fellowship and the NIH F30) Disclosures Bhat: Janssen: Consultancy; Pharmacyclics: Consultancy. Rogers:Janssen: Research Funding; AbbVie: Research Funding; Genentech: Research Funding; Acerta Pharma: Consultancy. Woyach:AbbVie: Research Funding; Janssen: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Karyopharm: Research Funding; Loxo: Research Funding; Morphosys: Research Funding; Verastem: Research Funding. Lozanski:Beckman Coulter: Research Funding; Stemline Therapeutics Inc.: Research Funding; Genentec: Research Funding; Boehringer Ingelheim: Research Funding. Muthusamy:Ohio State University: Patents & Royalties: OSU-2S. Byrd:Novartis: Other: Travel Expenses, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Ohio State University: Patents & Royalties: OSU-2S; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; 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; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; BeiGene: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Genentech: Research Funding; Acerta: Research Funding.

In this issue of Blood, Ghez et al report on 33 patients who developed invasive fungal infections during ibrutinib treatment, the majority of which were invasive aspergillosis, which supports the observation that fungal infections are a potential risk with ibrutinib.1