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The treatment landscape of relapsed/refractory (R/R) classic Hodgkin lymphoma (cHL) has evolved significantly over the past decade following the approval of brentuximab vedotin (BV) and the programmed death-1 (PD-1) inhibitors. We evaluated how outcomes and practice patterns have changed for R/R cHL patients who underwent autologous hematopoietic cell transplantation (AHCT) at our institution from 2011-2020 (N=183) compared to 2001-2010 (N=159) and evaluated prognostic factors for progression-free survival (PFS) and overall survival (OS) in both eras. OS was superior in the modern era (4-year estimates 89.1% vs 79.0%, HR 0.53, 95% CI 0.33-0.85, p=0.011) with a trend towards lower non-relapse mortality beyond 2 years post-transplant. Among patients who progressed after AHCT, 4-year post-progression survival increased from 43.3% to 71.4% in the modern era, reflecting increasing use of BV and the PD-1 inhibitors. In multivariable analysis for patients transplanted in the modern era, age ³45 years, primary refractory disease, and lack of complete remission pre-AHCT were associated with inferior PFS, while receipt of a PD-1 inhibitor-based regimen pre-AHCT was associated with superior PFS (HR 0.21, 95% CI 0.05-0.80, p=0.030). Extranodal disease at relapse was associated with inferior OS (HR 3.12, 95% CI 1.25-7.77, p=0.014). Our study demonstrates improved survival for R/R cHL after AHCT in the modern era attributed to more effective salvage regimens allowing for better disease control pre-AHCT and improved outcomes for patients who progressed after AHCT. Excellent outcomes were observed with PD-1 inhibitor-based salvage regimens pre-AHCT and support a randomized trial evaluating immunotherapy in the second line setting.

The prognosis of patients with large B-cell lymphoma (LBCL) that progresses after treatment with chimeric antigen receptor (CAR) T-cell therapy targeting CD19 (CAR19) is poor. We report on the first 3 consecutive patients with autologous CAR19-refractory LBCL who were treated with a single infusion of autologous 1 × 106 CAR+ T cells per kilogram targeting CD22 (CAR22) as part of a phase 1 dose-escalation study. CAR22 therapy was relatively well tolerated, without any observed nonhematologic adverse events higher than grade 2. After infusion, all 3 patients achieved complete remission, with all responses continuing at the time of last follow-up (mean, 7.8 months; range, 6-9.3). Circulating CAR22 cells demonstrated robust expansion (peak range, 85.4-350 cells per microliter), and persisted beyond 3 months in all patients with continued radiographic responses and corresponding decreases in circulating tumor DNA beyond 6 months after infusion. Further accrual at a higher dose level in this phase 1 dose-escalation study is ongoing and will explore the role of this therapy in patients in whom prior CAR T-cell therapies have failed. This trial is registered on clinicaltrials.gov as #NCT04088890.

Profiling of circulating tumor DNA (ctDNA) in the bloodstream shows promise for noninvasive cancer detection. Chromatin fragmentation features have previously been explored to infer gene expression profiles from cell-free DNA (cfDNA), but current fragmentomic methods require high concentrations of tumor-derived DNA and provide limited resolution. Here we describe promoter fragmentation entropy as an epigenomic cfDNA feature that predicts RNA expression levels at individual genes. We developed 'epigenetic expression inference from cell-free DNA-sequencing' (EPIC-seq), a method that uses targeted sequencing of promoters of genes of interest. Profiling 329 blood samples from 201 patients with cancer and 87 healthy adults, we demonstrate classification of subtypes of lung carcinoma and diffuse large B cell lymphoma. Applying EPIC-seq to serial blood samples from patients treated with PD-(L)1 immune-checkpoint inhibitors, we show that gene expression profiles inferred by EPIC-seq are correlated with clinical response. Our results indicate that EPIC-seq could enable noninvasive, high-throughput tissue-of-origin characterization with diagnostic, prognostic and therapeutic potential.

Allogeneic hematopoietic cell transplantation (HCT) remains an important treatment for adults with acute lymphoblastic leukemia (ALL). We hypothesized that advances in ALL and transplantation have resulted in improved HCT outcomes in recent years. In this study, we evaluated the characteristics and outcomes of adult ALL patients undergoing allogeneic HCT over the last decade. Patients with ALL aged 18 years and older who underwent allogeneic HCT at Stanford University between 2008 and 2019 were included in this study. Patients were divided into 2 eras based on year of HCT: 2008 to 2013 (earlier era) and 2014 to 2019 (later era). A total of 285 patients were included: 119 patients underwent HCT in the earlier era and 166 in the later era. Patients who underwent transplantation in the later era were more likely to be Hispanic (38% versus 21%) and to have an HCT-comorbidity index ≥3 (31% versus 18%). Donor source for HCT also differed with an increase in the use of HLA-mismatched donor sources (38% versus 24%), notably umbilical cord blood in the later era (16% versus 0%). Patients in the later era were less likely to undergo transplantation with active disease (4% versus 16%); pre-HCT rates of measurable residual disease were similar across the eras (38% versus 40%). In unadjusted analyses, overall survival (OS) improved across eras, with 2-year estimates for the later and earlier eras of 73% (95% confidence interval [CI], 66%-80%) versus 55% (95% CI, 46%-64%), respectively. Multivariable analysis confirmed the association between later era and OS (hazard ratio = 0.52, 95% CI, 0.34-0.78). Finally, among patients relapsing after HCT (25% in later era and 33% in earlier era), the use of novel immunotherapies increased in the later era (44% versus 3%), as did the median OS after post-HCT relapse (16 months versus 8 months, P.001). OS after HCT for adult ALL has improved in recent years. This is due, in part, to a significant improvement in the ability to effectively salvage adults with ALL relapsing after HCT.

Background As a result of the COVID-19 widespread pandemic, cryopreservation of allogeneic donor apheresis products was implemented to mitigate the challenges of donor availability and product transport. Although logistically beneficial, the impact of cryopreservation on clinical outcomes and graft composition remains unclear. Objectives To compare the outcomes and graft composition with cryopreserved versus fresh allografts in the setting of allogeneic hematopoietic cell transplantation (allo-HCT). Study design We retrospectively analyzed the clinical outcomes of 30 consecutive patients who received cryopreserved allografts between March and August 2020 as compared to 60 consecutive patients who received fresh allografts prior to the COVID-19 pandemic. Primary endpoints were hematopoietic engraftment, graft failure (GF) and secondary outcomes were overall survival (OS), relapse free survival (RFS) and non-relapse mortality (NRM). In addition, extended immunophenotype analysis was performed on cryopreserved versus prospectively collected fresh apheresis samples. Results Compared to fresh allografts, both neutrophil and platelet recovery were delayed in recipients of cryopreserved reduced intensity conditioning (RIC) allo-HCT with median times to engraftment of 24 days vs 18 days (P = .01) and 27 days vs 18 days (P = .069), respectively. We observed primary GF in 4 of 30 patients in the cryopreserved cohort (13.3%) vs only one of 60 patients (1.7 %) in the fresh cohort (P = .03). Cryopreserved RIC allo-HCT was associated with significantly lower median total, myeloid and T-cell donor chimerism at 1 month. OS and RFS were inferior for cryograft recipients with hazard ratio [HR (95%Cl)]: 2.16 (1.00, 4.67) and 1.90 (0.95, 3.79), respectively. Using an extended immunophenotype analysis we compared 14 samples from the cryopreserved cohort to 6 prospectively collected fresh apheresis donor samples. These analyses showed both decrease in total cell viability and significantly reduced absolute numbers of NK cells (CD3−CD56+) in the cryopreserved apheresis samples. Conclusion In this single institution study we note delayed engraftment and a trend toward clinical inferiority of cryopreserved vs fresh allografts. Further evaluation of the use of cryopreserved allografts and their impact on clinical and laboratory outcomes is warranted.

Growth factor and chemotherapy-based stem cell mobilization strategies are commonly used to treat patients with multiple myeloma. We retrospectively compared 398 patients mobilized between 2017 and 2020 using either cyclophosphamide (4 g/m(2)) plus granulocyte colony-stimulating factor (G-CSF) or G-CSF alone, with on demand plerixafor (PXF) in both groups. Although total CD34(+) yield was higher after chemomobilization compared with G-CSF +/− PXF (median, 13.6 × 10(6)/kg versus 4.4 × 10(6)/kg; P < .01), achievement of ≥2 × 10(6) CD34(+) cells (95% versus 93.7%; P =.61) and rates of mobilization failure (5% versus 6.3%; P =.61) were similar. Fewer patients required PXF with chemomobilization (12.3% versus 49.5%; P < .01), and apheresis sessions were fewer (median, 1 [range, 1 to 4] versus 2 [range, 1 to 5]). The rate of complications, including neutropenic fever, emergency department visits, and hospitalizations, was higher after chemomobilization (30% versus 7.4%; P < .01). Previous use of ≤6 cycles of lenalidomide did not impair cell yield in either group. The median cost of mobilization was 17.4% lower in the G-CSF +/− PXF group (P = .01). Between group differences in time to engraftment were not clinically significant. Given similar rates of successful mobilization, similar engraftment time, and less toxicity and lower costs compared with chemomobilization, G-CSF with on-demand PXF may be preferable in myeloma patients with adequate disease control and limited lenalidomide exposure.

Background: MGTA-145, a CXCR2 agonist, has shown promising activity for hematopoietic stem cell (HSC) mobilization with plerixafor in pre-clinical models and healthy volunteers. It has the potential to become the first GCSF free regimen for HSC mobilization/apheresis in preparation for transplant, with fewer side effects, better patient experience and optimal resource utilization. Methods: We conducted a single center phase 2 trial of MGTA-145 + plerixafor for HSC mobilization in patients with multiple myeloma (MM), NCT04552743. Primary endpoint was collection of ≥2 x 10 6 CD34+ cells/kg in up to 2 days of mobilization/apheresis. Secondary endpoints were collection of 4 and 6 x 10 6 CD34+ cells/kg, safety and engraftment. Patients with MM, 18-70 years of age, within 1 year of starting treatment & CrCl > 30 ml/min were eligible. Patients received plerixafor 0.24 mg/kg (0.16 mg/kg if renal dysfunction) SQ, followed 2 hours later by MGTA-145 (0.03 mg/kg) IV over 3-10 minutes and apheresis within 30 minutes. Mobilization and collection were repeated for a second consecutive day if day 1 yield was < 6 x 10 6 CD34+ cells/kg. The study was open-label single arm trial of 15 patients. If 13 or more patients met primary endpoint, an expansion cohort of 10 patients was planned. The trial has 85% power at a 5% one-sided type I error rate. Our analysis is based on aggregated results from total cohort of 25 patients. Results: Median age was 62 years, 52% were female, 24% had ISS stage 3, 57% had high-risk FISH (primarily gain1q). Induction therapy was VRD in 68% (17), daratumumab VRD in 24% (6), CyBorD in 8% (2) patients. Median duration of induction was 4 months (3-6) and median lenalidomide exposure was 5 cycles (1-8), with > VGPR in 88% of patients. (Table 1) Plerixafor 0.24 mg/kg was given in 24 (96%) patients. Median pre-apheresis CD34 count was day 1, 24/uL (3-99) & day 2, 15/uL (5-46). Median total HSC cell yield (CD34+ cells/kg x 10 6) was 5.0 (1.1-16.2), day 1 yield was 3.4 (0.3-16.2) and day 2 yield was 1.9 (0.5-4.6) (Fig1). 88% (n=22) of patients met the primary endpoint of collecting sufficient HSCs in < 2 days of mobilization + apheresis to proceed to transplant, 68% (17) in 1 day (2 x 10 6 CD34+ cells/kg). 3 patients who did not meet primary endpoint successfully collected HSCs with standard GCSF + plerixafor dosing & 2-3 apheresis sessions. Secondary endpoints of 4 and 6 x 10 6 CD34+ cells/kg in < 2 days were met in 68% (17) and 40% (10) patients. MGTA-145+plerixafor was well tolerated. At least 1 treatment emergent AE (TEAE) with MGTA-145 was seen in 60% of patients (grade 1, n= 14, grade 2, n=1). Pain (all grade 1) was most common, seen in 44% (11), with 38% (9) patients experiencing acute onset transient bone pain with MGTA-145 (duration: 7 minutes, range: 3-28). Using the validated Brief Pain Inventory, 56% (14) patients self-reported pain with mobilization vs 40% (10) at baseline. 7/15 patients without baseline pain reported pain with mobilization. An increase for worst pain was seen on mobilization day 1, that returned to the baseline, but no difference for aggregate score of pain severity/interference (linear mixed effects model). At last follow-up, 18 patients have completed transplant with MGTA-145 mobilized graft, with melphalan 200 mg/m 2 in 15 (83%) patients. Median of 3.5 (2.2-8.1) x 10 6 CD34+ cells/kg were infused. All patients have engrafted. Median time to neutrophil engraftment of 12 days (range: 11-15) & platelet engraftment (platelets > 20,000, no transfusion in 7 days) of 17.5 days (15-33) are comparable to historical data (DiPersio et al. 2009). RBC transfusion was needed in 3 (17%) patients. 14 patients have day 100 follow-up, all with durable engraftment. MGTA-145 + plerixafor mobilized grafts had a favorable graft composition. We observed high enrichment for CD90+CD45RA- among CD34+ cells, a CD34 subset of long term engrafting HSCs (median: 36% of CD34+ cells, range 10-66%, N=25). 74% (17 of 23) grafts were minimal residual disease negative with next generation flow cytometry. Conclusions: This is the first study to evaluate the novel G-CSF-free regimen of MGTA-145 + plerixafor for HSC cell mobilization & collection for hematologic malignancies. The study cohort was representative of transplant eligible patients with MM, with 88% patients meeting the primary endpoint. The regimen was well tolerated. Patients achieved timely & durable engraftment. Our data support further development of this regimen for rapid HSC mobilization. Figure 1 Figure 1. Disclosures Sidana: Janssen: Consultancy, Research Funding; Allogene: Research Funding; Magenta Therapeutics: Consultancy, Research Funding; BMS: Consultancy. Kumar: Bluebird Bio: Consultancy; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Carsgen: Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Oncopeptides: Consultancy; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tenebio: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Consultancy; Antengene: Consultancy, Honoraria; Amgen: Consultancy, Research Funding; Roche-Genentech: Consultancy, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; BMS: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding. Muffly: Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy; Astellas, Jasper, Adaptive, Baxalta: Research Funding; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding. Arai: Magenta Therapeutics: Research Funding. Meyer: Indee, Jura: Consultancy; Orca Biosystems: Research Funding; GigaImmune: Current holder of stock options in a privately-held company; Triursus Therapeutics: Current holder of stock options in a privately-held company. Rezvani: US Department of Justice: Consultancy; Kaleido: Other: One-time scientific advisory board; Nohla Therapeutics: Other: One-time scientific advisory board; Pharmacyclics-Abbvie: Research Funding. Weng: Kite Pharma: Research Funding. Frank: Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Allogene Therapeutics: Research Funding; Adaptive Biotechnologies: Research Funding. Shiraz: Kite Pharma-Gilead: Research Funding. Girgenti: Magenta Therapeutics: Current Employment. Goncalves: Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Schmelmer: Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Davis: Magenta Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Shizuru: Jasper Therapeutics, Inc.: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Chair of scientific advisory board; Forty seven Inc: Other: Inventor on a patent licenses by Forty Seven. Forty seven was acquired by Gilead in 2020. Miklos: Pharmacyclics: Patents & Royalties; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees.

Background Allogeneic (off the shelf) chimeric antigen receptor (CAR) T-cell therapy addresses the logistical challenges, availability (including insufficient T-cell yields from low baseline absolute lymphocyte count), and variable product quality of autologous CAR T therapy. ALLO-501 is a genetically modified anti-CD19 AlloCAR T™ cell product that uses TALEN ® gene editing to disrupt the T-cell receptor alpha constant gene and the CD52 gene with TALEN to reduce the risk of graft-versus-host disease (GvHD) and permit the use of ALLO-647 (anti-CD52 monoclonal antibody [mAb]), for selective and transitory host lymphodepletion (LD). Here we present updated safety and efficacy data including consolidation cohort. ALLO-501 uses Cellectis technologies. Methods ALPHA (NCT03939026) is a Phase 1, open-label, multicenter dose escalation study in patients (pts) with relapsed/refractory (R/R) large B-cell lymphoma (LBCL) or follicular lymphoma (FL) and ≥2 prior lines of therapy (including an anti-CD20 mAb). Pts with donor specific antibodies and baseline rituximab >15 ng/mL were excluded. Following LD with ALLO-647 (39, 60, or 90 mg), fludarabine 30 mg/m 2/d x 3d (F), and cyclophosphamide 300 or 500 mg/m 2/d x 3d (C), escalating doses of ALLO-501 (40, 120, or 360 x 10 6 viable CAR T cells [DL1, DL2 and DL3]) were given. For pts receiving one ALLO-501 dose, retreatment was allowed. In the consolidation cohort, pts with ≥stable disease (SD) at D28 receive consolidation therapy with second ALLO-647 dose of 30 mg and ALLO-501 (DL2) cell infusion. Results As of July 9, 2021, 98% (46/47) of pts enrolled were treated (1pt excluded due to renal failure) with ALLO-501 in the single dose cohort (n=39) and consolidation cohort (n=7). Median time from enrollment to LD was 5 days. Pts had advanced-stage disease (Stage III: 17 [37.0%], Stage IV: 26 [56.5%]) and were heavily pretreated (median of 4 prior lines [range 2-12]). In the study, 20% of pts were R/R after prior Auto CAR T therapy; 54% were chemo refractory. No dose-limiting toxicities (DLTs) or GvHD observed. No pts experienced Grade (Gr) 2+ immune effector cell-associated neurotoxicity syndrome (ICANS). Gr 1/2 cytokine release syndrome (CRS) occurred in 21.7% (10/46) and Gr 3+ in 1 pt with a single dose and was managed with standard guidelines. Cytopenias were the most common adverse event (AE) and occurred in 82.6% of pts. Gr 3+ infections occurred in 23.9% of pts. As previously reported, 5 pts died after treatment, 4 of non-treatment related AEs and 1 of Aspergillus pneumonia (263d post CAR T) deemed related to ALLO-501. Efficacy in Auto CAR T naïve pts (n=36) was evaluated in the modified-intent-to-treat (mITT) population and was nearly identical to the intent-to-treat (ITT) population. The objective response (ORR) and complete response (CR) rates were 75% and 50%, respectively. Among pts with LBCL (n=13), ORR and CR were 61.5% (95% CI: 31.6, 86.1) and 46.2% (95% CI: 19.2, 74.9). In FL (n=23), the ORR was 82.6% (95% CI: 61.2, 95.1) and CR was 52.2% (95% CI: 30.6, 73.2). Of 7 pts in consolidation cohort, 5 FL pts received consolidation and 2 LBCL pts received 1 st CAR T dose and are awaiting consolidation. Of the 4 pts (all FL) that had a tumor assessment after consolidation dose (D56), ORR and CR were 100% and 75%, respectively. Among the 18 FL and 11 LBCL Auto CAR naïve pts who had the opportunity to be followed for 6 months, 27.8% of FL and 36.4% of LBCL pts remained in CR at month 6. The longest ongoing CR is 15+ months. All consolidation pts dosed remain in response with the longest response being a CR at month 4. Conclusions This updated data continues to highlight that allogeneic CAR T therapy can be safely and effectively delivered to pts with R/R NHL with encouraging durability of response. Ninety-eight percent of pts enrolled were treated with ALLO-501 with a median of 5 days from enrollment to therapy, supporting the ease and speed pts were able to be treated with AlloCAR T therapy. The safety was manageable with no DLT or GvHD; no Gr 2+ ICANS and limited CRS. Infection rates were similar to that observed in autologous CAR T trials. The 6-month CR rate of 36.4% in LBCL is similar to the 6-month CR rates reported in the pivotal trials of autologous CAR T therapies(NEJM 2017;377:2531-2544. Lancet 2020;396(10254):817. NEJM 2019;380:45-56). Consolidation dosing demonstrated similar safety and improved efficacy vs single dosing with ORR of 100% and CR of 75% in pts who had tumor evaluation after consolidation. Disclosures Neelapu: Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene Therapeutics, Cell Medica/Kuur, Incyte, Precision Biosciences, Legend Biotech, Adicet Bio, Calibr, Unum Therapeutics and Bluebird Bio: Honoraria; Takeda Pharmaceuticals and related to cell therapy: Patents & Royalties; Kite, a Gilead Company, Bristol Myers Squibb, Merck, Poseida, Cellectis, Celgene, Karus Therapeutics, Unum Therapeutics (Cogent Biosciences), Allogene, Precision BioSciences, Acerta and Adicet Bio: Research Funding; Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene, Kuur, Incyte, Precision BioSciences, Legend, Adicet Bio, Calibr, and Unum Therapeutics: Other: personal fees. Nath: Actinium: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Munoz: Targeted Oncology, OncView, Kyowa Kirin, Physicians' Education Resource, and Seagen: Honoraria; Pharmacyclics/Abbvie, Bayer, Kite, a Gilead Company, Pfizer, Janssen, Juno/Celgene, Bristol Myers Squibb, Kyowa Kirin, Alexion, Fosun Kite, Innovent, Seagen, BeiGene, Debiopharm, Epizyme, Karyopharm, ADC Therapeutics, Servier, and Genmab: Consultancy, Other: advisory role; Bayer, Gilead/Kite Pharma, Celgene, Merck, Portola, Incyte, Genentech, Pharmacyclics, Seattle Genetics, Janssen, and Millennium: Research Funding; Kite, a Gilead Company, Kyowa, Bayer, Pharmacyclics/Janssen, Seagen, Acrotech/Aurobindo, Beigene, Verastem, AstraZeneca, Celgene/BMS, Genentech/Roche.: Speakers Bureau; Alexion, AstraZeneca Rare Disease: Other: Study investigator. Miklos: Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Pharmacyclics: Patents & Royalties. Frank: Allogene Therapeutics: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding. Shin: Allogene Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Loomis-Navale: Allogene: Current Employment, Current equity holder in publicly-traded company. Nguyen: Allogene: Current Employment; Nektar: Ended employment in the past 24 months. Locke: Wugen: Consultancy, Other; EcoR1: Consultancy; Umoja: Consultancy, Other; Cowen: Consultancy; Kite, a Gilead Company: Consultancy, Other: Scientific Advisory Role, Research Funding; Iovance Biotherapeutics: Consultancy, Other: Scientific Advisory Role; GammaDelta Therapeutics: Consultancy, Other: Scientific Advisory Role; Moffitt Cancer Center: Patents & Royalties: field of cellular immunotherapy; Takeda: Consultancy, Other; Novartis: Consultancy, Other, Research Funding; Emerging Therapy Solutions: Consultancy; Janssen: Consultancy, Other: Scientific Advisory Role; Legend Biotech: Consultancy, Other; Gerson Lehrman Group: Consultancy; Cellular Biomedicine Group: Consultancy, Other: Scientific Advisory Role; Calibr: Consultancy, Other: Scientific Advisory Role; BMS/Celgene: Consultancy, Other: Scientific Advisory Role; Bluebird Bio: Consultancy, Other: Scientific Advisory Role; Amgen: Consultancy, Other: Scientific Advisory Role; Allogene Therapeutics: Consultancy, Other: Scientific Advisory Role, Research Funding. OffLabel Disclosure: Discussion of fludarabine and cyclophosphamide in combination with ALLO-647 as conditioning regimen prior to administration of ALLO-501 in NHL patients.

Introduction: Brexucabtagene autoleucel (brexu-cel) was approved by US FDA for relapsed/refractory (R/R) mantle cell lymphoma (MCL) on July 24, 2020 based on results from the pivotal ZUMA-2 (NCT02601313) study, in which an objective response rate (ORR) of 93% and a complete response (CR) rate of 67% were achieved among the 60 treated patients with at least 7 months of follow-up. The study had stringent eligibility criteria, including prior treatment with a BTK inhibitor (BTKi), and only allowed BTKi and/or corticosteroid for bridging therapy. We report here the safety and efficacy of brexu-cel in standard of care practice among centers in the US Lymphoma CAR-T Consortium. Methods: Fourteen centers participated in this retrospective study. Patients who underwent leukapheresis by 6/15/2021 with an intent to manufacture brexu-cel were included. Baseline clinical characteristics, bridging therapy, adverse events after brexu-cel infusion, and post-infusion outcome data were collected. Eligibility for ZUMA-2 was retrospectively determined based on characteristics at the time of leukapheresis. Duration of response (time from initial response to disease progression or death from any cause), progression-free survival (PFS; time from infusion to disease progression or death from any cause) and overall survival (OS; time from infusion to death from any cause) were analyzed using the Kaplan-Meier method. Results: At the data cut-off date of 7/9/2021, 107 patients underwent leukapheresis, among whom 93 (87%) completed brexu-cel infusion, 2 (2%) were waiting for infusion, and 12 (11%) did not receive infusion (manufacture failure n=6, organ dysfunction n=1, death n=5). Baseline clinical characteristics of the 93 infused patients are shown in Table 1. The median age was 67 years and 81% were male. 32% had high risk simplified MIPI, 77% had Ki-67≥30%, 45% had blastoid or pleomorphic variant, 46% had TP53 alteration, 29% had complex karyotype, and 7% had CNS involvement. The median number of prior lines of therapy was 3. Eighty-two percent had prior BTKi treatment, and 44% had refractory disease to the last line of therapy. Sixty-eight (73%) patients would not have met ZUMA-2 eligibility criteria. Reasons for ineligibility included ECOG PS ≥2 (n=8), CNS involvement by lymphoma (n=6), prior therapies (n=33), cytopenia (n=11), renal or hepatic dysfunction (n=13), other medical conditions (n=18), and active infection (n=2). Sixty (65%) of the 93 patients received bridging therapy, which included BTKi (n=27), venetoclax (n=14), chemotherapy (n=19), CD20 antibody (n=26), lenalidomide (n=3), corticosteroid (n=9), and radiotherapy (n=13). Only 13 (14%) patients received BTKi or corticosteroid alone as in ZUMA-2. Among 93 infused patients, cytokine release syndrome (CRS) rate was 88% (8% grade ≥3), and immune effector cell-associated neurotoxicity syndrome (ICANS) rate was 58% (33% grade ≥3). No grade 5 CRS or ICANS occurred. Medications used to manage CRS and ICANS were 71 (76%) for tocilizumab, 64 (69%) for steroid, and 16 (17%) for anakinra. Twenty-four (26%) patients required ICU admission, 9 patients required vasopressors, and 4 patients required mechanical ventilation. With a median follow-up of 3.0 months (range 0.1-9.6), day 30 response was evaluable in 81 patients, and the ORR was 86%, with 64% CR (Table 2). The ORR/CR rates were 94%/70% for blastoid or pleomorphic variants, 82%/50% for TP53 altered, 84%/61% for BTKi-exposed, 94%/76% for BTKi-naïve, and 88%/67% for those not meeting ZUMA-2 eligibility criteria. The ORR/CR rates were 87%/69% for patients who received bridging therapy and 85%/56% for those who did not. For patients who achieved a response at day 30, the rate of continued response at 3-month was 83.7% (95% CI 68.3%-92.0%). The 3-month PFS rate was 80.6% (95% CI 68.6%-88.4%), and the 6-month OS rate was 82.1% (95% CI 67.7%-90.5%). Conclusions: This multicenter retrospective study demonstrated encouraging safety and efficacy data of brexu-cel in R/R MCL in the real world practice. The CRS and ICANS incidences were comparable to those reported in ZUMA-2, but use of tocilizumab and steroid was more frequent than in ZUMA-2. Although 73% of the patients would have been ineligible for ZUMA-2, the ORR and CR rate were comparable to those reported in ZUMA-2. Longer follow-up is necessary to confirm long term safety and efficacy. YW, PJ and FLL are co-first authors, and YL, MW and MDJ are co-senior authors. Figure 1 Figure 1. Disclosures Wang: Novartis: Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Eli Lilly: Membership on an entity's Board of Directors or advisory committees; InnoCare: Research Funding; LOXO Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; MorphoSys: Research Funding. Jain: Kite: Consultancy; Lilly: Membership on an entity's Board of Directors or advisory committees. Locke: Gerson Lehrman Group: Consultancy; Emerging Therapy Solutions: Consultancy; EcoR1: Consultancy; Cowen: Consultancy; GammaDelta Therapeutics: Consultancy, Other: Scientific Advisory Role; Kite, a Gilead Company: Consultancy, Other: Scientific Advisory Role, Research Funding; Umoja: Consultancy, Other; Janssen: Consultancy, Other: Scientific Advisory Role; Wugen: Consultancy, Other; Legend Biotech: Consultancy, Other; Takeda: Consultancy, Other; Novartis: Consultancy, Other, Research Funding; Moffitt Cancer Center: Patents & Royalties: field of cellular immunotherapy; Iovance Biotherapeutics: Consultancy, Other: Scientific Advisory Role; Calibr: Consultancy, Other: Scientific Advisory Role; Cellular Biomedicine Group: Consultancy, Other: Scientific Advisory Role; BMS/Celgene: Consultancy, Other: Scientific Advisory Role; Bluebird Bio: Consultancy, Other: Scientific Advisory Role; Amgen: Consultancy, Other: Scientific Advisory Role; Allogene Therapeutics: Consultancy, Other: Scientific Advisory Role, Research Funding. Munoz: Bayer, Gilead/Kite Pharma, Celgene, Merck, Portola, Incyte, Genentech, Pharmacyclics, Seattle Genetics, Janssen, and Millennium: Research Funding; Kite, a Gilead Company, Kyowa, Bayer, Pharmacyclics/Janssen, Seagen, Acrotech/Aurobindo, Beigene, Verastem, AstraZeneca, Celgene/BMS, Genentech/Roche.: Speakers Bureau; Targeted Oncology, OncView, Kyowa Kirin, Physicians' Education Resource, and Seagen: Honoraria; Pharmacyclics/Abbvie, Bayer, Kite, a Gilead Company, Pfizer, Janssen, Juno/Celgene, Bristol Myers Squibb, Kyowa Kirin, Alexion, Fosun Kite, Innovent, Seagen, BeiGene, Debiopharm, Epizyme, Karyopharm, ADC Therapeutics, Servier, and Genmab: Consultancy, Other: advisory role; Alexion, AstraZeneca Rare Disease: Other: Study investigator. Maurer: BMS: Research Funding; Genentech: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Nanostring: Research Funding. Beitinjaneh: Kite/Gilead: Other: Ad Board Event Attendee. Frank: Allogene Therapeutics: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding. Dahiya: Miltenyi Biotech: Research Funding; Kite, a Gilead Company: Consultancy; Jazz Pharmaceuticals: Research Funding; Atara Biotherapeutics: Consultancy; BMS: Consultancy. McGuirk: Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Gamida Cell: Research Funding; Novartis: Research Funding; Bellicum Pharmaceuticals: Research Funding; Fresenius Biotech: Research Funding; Astelllas Pharma: Research Funding; Novartis: Research Funding; Allovir: Consultancy, Honoraria, Research Funding; Pluristem Therapeutics: Research Funding; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; EcoR1 Capital: Consultancy. Goy: Vincerx pharma: Membership on an entity's Board of Directors or advisory committees; Michael J Hennessey Associates INC: Consultancy; Elsevier's Practice Update Oncology, Intellisphere, LLC(Targeted Oncology): Consultancy; Phamacyclics: Research Funding; Vincerx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Rosewell Park: Consultancy; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; AbbVie/Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Research Funding; Incyte: Honoraria; Hoffman la Roche: Consultancy; LLC(Targeted Oncology): Consultancy; Xcenda: Consultancy, Honoraria; OncLive Peer Exchange: Honoraria; Infinity/Verastem: Research Funding; Genentech/Hoffman la Roche: Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Medscape: Consultancy; Xcenda: Consultancy; Bristol Meyers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding; Bristol Meyers Squibb: Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie/Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Elsevier PracticeUpdate: Oncology: Consultancy, Honoraria; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Genomic Testing Cooperative: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Leadership role; Physicians' Education Resource: Consultancy, Other: Meeting/travel support; MorphoSys: Honoraria, Other; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Constellation: Research Funding; COTA (Cancer Outcome Tracking Analysis): Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Leadership role; Hackensack Meridian Health, Regional Cancer Care Associates/OMI: Current Employment. Vose: Kite, a Gilead Company: Honoraria, Research Funding. Hill: Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel Support, Research Funding; Celgene (BMS): Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Gentenech: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Incyte/Morphysis: Consultancy, Honoraria, Research Funding; AstraZenica: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria. Oluwole: Pfizer: Consultancy; Curio Science: Consultancy; Janssen: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. Deol: Kite, a Gilead Company: Consultancy. Shah: Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding; Pfizer: Consultancy, Other: Expenses; Novartis: Consultancy, Other: Expenses; Bristol-Myers Squibb/Celgene: Consultancy, Other: Expenses; BeiGene: Consultancy, Honoraria; Amgen: Consultancy; Precision Biosciences: Consultancy; Kite, a Gilead Company: Consultancy, Honoraria, Other: Expenses, Research Funding; Pharmacyclics/Janssen: Honoraria, Other: Expenses; Acrotech/Spectrum: Honoraria; Servier Genetics: Other; Adaptive Biotechnologies: Consultancy. Paludo: Karyopharm: Research Funding. Miklos: Pharmacyclics: Patents & Royalties; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy. Ghobadi: Wugen: Consultancy; Atara: Consultancy; Amgen: Consultancy, Research Funding; Celgene: Consultancy; Kite, a Gilead Company: Consultancy, Honoraria, Research Funding. Neelapu: Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene Therapeutics, Cell Medica/Kuur, Incyte, Precision Biosciences, Legend Biotech, Adicet Bio, Calibr, Unum Therapeutics and Bluebird Bio: Honoraria; Takeda Pharmaceuticals and related to cell therapy: Patents & Royalties; Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene, Kuur, Incyte, Precision BioSciences, Legend, Adicet Bio, Calibr, and Unum Therapeutics: Other: personal fees; Kite, a Gilead Company, Bristol Myers Squibb, Merck, Poseida, Cellectis, Celgene, Karus Therapeutics, Unum Therapeutics (Cogent Biosciences), Allogene, Precision BioSciences, Acerta and Adicet Bio: Research Funding. Lin: Legend: Consultancy; Novartis: Consultancy; Gamida Cell: Consultancy; Vineti: Consultancy; Bluebird Bio: Consultancy, Research Funding; Sorrento: Consultancy; Takeda: Research Funding; Merck: Research Funding; Janssen: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. Wang: Moffit Cancer Center: Honoraria; Chinese Medical Association: Honoraria; InnoCare: Consultancy, Research Funding; Epizyme: Consultancy, Honoraria; Hebei Cancer Prevention Federation: Honoraria; Newbridge Pharmaceuticals: Honoraria; Genentech: Consultancy; OMI: Honoraria; Physicians Education Resources (PER): Honoraria; Clinical Care Options: Honoraria; CAHON: Honoraria; VelosBio: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; CStone: Consultancy; Loxo Oncology: Consultancy, Research Funding; BioInvent: Research Funding; Juno: Consultancy, Research Funding; DTRM Biopharma (Cayman) Limited: Consultancy; BGICS: Honoraria; Bayer Healthcare: Consultancy; Janssen: Consultancy, Honoraria, Research Funding; Kite Pharma: Consultancy, Honoraria, Research Funding; Molecular Templates: Research Funding; Imedex: Honoraria; Miltenyi Biomedicine GmbH: Consultancy, Honoraria; Dava Oncology: Honoraria; Oncternal: Consultancy, Research Funding; Lilly: Research Funding; Celgene: Research Funding; Anticancer Association: Honoraria; AstraZeneca: Consultancy, Honoraria, Research Funding; The First Afflicted Hospital of Zhejiang University: Honoraria; BeiGene: Consultancy, Honoraria, Research Funding; Scripps: Honoraria; Mumbai Hematology Group: Honoraria; Acerta Pharma: Consultancy, Honoraria, Research Funding. Jain: BMS, Kite/Gilead, Novartis, Precision Biosciences, Takeda: Consultancy.

BACKGROUND: Patients with relapsed/refractory (R/R) large B-cell lymphoma (LBCL) after failure of CD19-directed CAR T-cell therapy (CAR19) have a dire prognosis, with an overall response rate (ORR) of 29% to conventional salvage therapies, and a median overall survival (OS) of 6 months. CD22 is expressed on the majority of B-cell malignancies. Autologous CAR T-cells targeting CD22 (CAR22) have yielded an ORR of 70-90% in pediatric patients with R/R B-cell acute lymphoblastic leukemia (B-ALL), including those who had previously failed CAR19 therapy. Based on these encouraging results, we evaluated CAR22 in adult patients with R/R LBCL, focusing on those with CAR19-refractory disease. METHODS: This ongoing single-institution phase I dose escalation clinical trial (NCT04088890) is evaluating a CAR construct incorporating the m971 CD22 single chain variable fragments and 41BB/CD3z endodomains integrated within autologous T-cells via lentiviral transduction. After lymphodepletion (LD) with fludarabine and cyclophosphamide, patients are infused with cryopreserved CAR T-cells after a 7- to 11-day closed manufacturing process utilizing the CliniMACS Prodigy device (Miltenyi). Primary objectives assess the ability to successfully manufacture CAR22 and safety. Secondary objectives include efficacy and durability of responses. RESULTS: Twenty-one patients with LBCL [n=12 at dose level 1 (DL1), 1x10 6 CAR+ cells/kg; n=9 at dose level 2 (DL2), 3x10 6 CAR+ cells/kg] have been enrolled with a median age of 64 years (range, 36-79) and a median of 4 (range, 3-8) prior lines of therapy. All patients had at least one high risk feature, including failure of prior CAR19 therapy (n=20); refractory disease to second-line or later therapy (n=17); elevated lactate dehydrogenase (LDH) pre-LD (n=17); high tumor burden (n=9); a history of primary refractory disease (n=7); failure of prior autologous hematopoietic stem cell transplantation (HSCT) (n=6); never achieving CR to any therapy (n=5); or LBCL with MYC gene rearrangements (n=5). Successful manufacturing of cells was achieved in all patients. All patients reached day 28 post-infusion and are included in the safety and efficacy analysis presented here; updated results will be presented at the meeting. Every patient experienced cytokine release syndrome (CRS); 20/21 (95%) were Grade 1-2, 1/21 (5%) were Grade 3. Four patients (19%) experienced immune effector cell-associated neurotoxicity syndrome (ICANS); all cases were Grade 1-2 and resolved within 2 days. Five patients (24%) experienced a hyperinflammatory macrophage activation syndrome (MAS), manifested in all cases by pancytopenia and consumptive coagulopathy (DIC) requiring transfusion and/or growth factor support. One patient who received DL2 had a Grade 5 infectious event in the setting of ongoing MAS and pancytopenia. Relative to DL1, higher prevalence of Grade ≥3 cytopenias beyond D28 (89% vs. 50%) and MAS (33% vs. 17%) were observed at DL2; thus, DL1 was selected as the maximally tolerated dose (MTD). ORR at D28 was 86% (CR, n=11; PR, n=7), and was similar between DL1 and DL2 (92% vs. 78%; p=ns). 3/7 (43%) initial PR improved to CR at a median of 3 months post-infusion. All 14 patients (67% of cohort) who achieved CR remain in remission, with a mean follow-up of 7.3 months (range, 1.2-21.3); median progression free survival (PFS) and OS have not yet been reached. Five patients died from disease progression, and one patient died from septic shock in CR. CD22 expression by flow was downregulated or absent in 1/3 (33%) patients evaluated after relapse. Peak CAR-T expansion as detected by peripheral blood flow cytometry occurred at a median of 14 days, with a trend towards earlier and higher peak levels in DL2 patients. Significantly higher mean CAR-T levels occurred at peak expansion in patients who developed MAS (1070±915 vs. 196±209 CAR+ cells/μL; p=0.001). CONCLUSIONS: Infusion of CAR22 in R/R LBCL is safe and well tolerated at DL1. Manufacturing of CAR22 was uniformly successful. With a mean follow-up of 7.3 months, the ORR and CR rates are 18/21 (86%) and 14/21 (67%), respectively. These data demonstrate CAR22 to be an effective salvage therapy for CAR19-refractory or CD19-negative LBCL. Figure 1 Figure 1. Disclosures Frank: Allogene Therapeutics: Research Funding; Adaptive Biotechnologies: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees. Oak: Kite Pharma-Gilead: Research Funding. Arai: Magenta Therapeutics: Research Funding. Rezvani: Kaleido: Other: One-time scientific advisory board; Nohla Therapeutics: Other: One-time scientific advisory board; Pharmacyclics-Abbvie: Research Funding; US Department of Justice: Consultancy. Shiraz: Kite Pharma-Gilead: Research Funding. Sidana: Janssen: Consultancy, Research Funding; Allogene: Research Funding; Magenta Therapeutics: Consultancy, Research Funding; BMS: Consultancy. Weng: Kite Pharma: Research Funding. Davis: Novartis Pharmaceuticals: Honoraria; Jazz Pharmaceuticals: Research Funding. Feldman: Samsara Biocapital: Consultancy; Obsidian: Consultancy; Lonza PerMed: Consultancy; Gradalis: Consultancy. Mackall: Lyell: Consultancy, Current equity holder in publicly-traded company, Other: Founder; Syncopation Life Sciences: Consultancy, Current holder of individual stocks in a privately-held company, Other: Founder; Apricity: Consultancy, Current equity holder in publicly-traded company; Neoimmune Tech: Consultancy; Nektar: Consultancy, Research Funding. Miklos: Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Pharmacyclics: Patents & Royalties; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees. Muffly: Astellas, Jasper, Adaptive, Baxalta: Research Funding; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding; Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy. OffLabel Disclosure: CD22-directed CAR-T therapy for the treatment of adults with relapsed/refractory large B-cell lymphoma

Introduction: In situ vaccination aims to induce an immune response locally at one tumor site that propagates systemically to all tumor sites. This approach can be effective in indolent lymphoma (Brody et al., JCO 2010, Frank et al., Cancer Discov 2018, Hammerich et al., Nat Med 2019). We designed a novel clinical strategy combining in situ vaccination with systemic ibrutinib, a kinase inhibitor that modulates B and T cells. Our preclinical work had shown that combined intratumoral CpG injection and systemic ibrutinib administration was curative of systemic disease in a mouse lymphoma model, an effect that was T cell dependent (Sagiv-Barfi, Blood, 2015). Here we report the results and correlative data from the Phase I/II clinical trial testing this combination along with local low-dose radiation in adults with recurrent low-grade B cell lymphoma (NCT02927964). Methods: Enrolled patients received intratumoral injections of CpG (SD-101, 3 mg) weekly for 5 doses and local radiation (4Gy in two fractions) to the same site. Daily oral ibrutinib (560mg) began after the second intratumoral injection. Revised Lugano criteria (Cheson et al., JCO, 2014) were used to assess overall radiographic responses to therapy. Distal responses were assessed by excluding the injected site and measuring only non-injected sites. Fine needle aspirates (FNAs) were obtained from CpG-injected and non-injected nodal tumor sites pre- and post-treatment and analyzed by flow cytometry and droplet-based single-cell RNA sequencing (scRNAseq). Results: Among the twenty patients treated on study, median age was 64, 55% were male, and all but one had a diagnosis of follicular lymphoma. All patients were previously treated with an average of 2 lines of therapy, and half had previously received chemotherapy. Adverse events (AEs) were consistent with known effects of ibrutinib (including diarrhea and rash) and of CpG (including fever and flu-like reactions). No drug-related grade 4, serious, or unexpected AEs were observed. As anticipated, all patients experienced tumor reduction at the locally treated site (median 84% reduction). Remarkably, all patients experienced some tumor reduction at non-injected non-irradiated index lesions (median 45%, range 13-100%), suggesting the generation of systemic immune responses (Figure 1A). By Cheson criteria, ten patients achieved an objective response, including one complete response (ORR 50%). Despite an overall improvement in tumor burden, three patients had new or progressing non-index lesions and scored as progressive disease. Treatment induced an expansion of naïve and effector memory T cells and reductions in T follicular helper (Tfh) and activated regulatory T cells (Tregs) at the injected site. T cells with high expression of transcripts related to oxidative phosphorylation (Toxphos) increased preferentially in patients with subsequent clinical tumor reduction (Figure 1B), implicating T cell metabolism in successful generation of immune responses. Analysis of single cell T cell receptor (TCR) sequencing data revealed>300 clones that were comprised of at least 2 cells at each timepoint and which expanded or contracted at least two-fold during treatment. Expanding clones were more likely than contracting clones to be activated or memory T cells and less likely than contracting clones to be Tfh or Tregs (Figure 1C-D). Clone dynamics were often similar at the two sampled tumor sites, reflecting systemic immune responses. Finally, in vitro assays showed treatment-induced expansion of tumor-specific T cells in the peripheral blood of all 6 evaluable patients. Conclusion: The combination of oral ibrutinib, intratumoral CpG, and local low-dose radiation is safe and can generate systemic antitumor immune responses and systemic tumor shrinkage in low-grade B cell lymphoma. Figure 1 Figure 1. Disclosures Shree: Gilead: Other: Spouse's employment. Khodadoust: CRISPR Therapeutics, Nutcracker Therapeutics: Research Funding; Myeloid Therapeutics: Membership on an entity's Board of Directors or advisory committees; Alexion, AstraZeneca Rare Disease: Other: Study investigator. Frank: Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding; Allogene Therapeutics: Research Funding. Beygi: Kite/Gilead: Current Employment. Levy: GigaGen: Membership on an entity's Board of Directors or advisory committees; Teneobio: Membership on an entity's Board of Directors or advisory committees; Nurix: Membership on an entity's Board of Directors or advisory committees; Dragonfly: Membership on an entity's Board of Directors or advisory committees; Apexigen: Membership on an entity's Board of Directors or advisory committees; Viracta: Membership on an entity's Board of Directors or advisory committees; Spotlight: Membership on an entity's Board of Directors or advisory committees; Immunocore: Membership on an entity's Board of Directors or advisory committees; Walking Fish: Membership on an entity's Board of Directors or advisory committees; Kira: Membership on an entity's Board of Directors or advisory committees; Abintus Bio: Membership on an entity's Board of Directors or advisory committees; Khloris: Membership on an entity's Board of Directors or advisory committees; Virsti: Membership on an entity's Board of Directors or advisory committees; BiolineRx: Membership on an entity's Board of Directors or advisory committees; BeiGene: Membership on an entity's Board of Directors or advisory committees; Quadriga: Membership on an entity's Board of Directors or advisory committees.

BACKGROUND GVHD and non-relapse mortality (NRM) remain frequent complications of HLA-matched HSCT despite the use of standard immunosuppression like tacrolimus and methotrexate. Alternative GVHD prophylaxis (PPX) strategies like T-cell depletion and post-transplant cyclophosphamide negatively impact relapse, infection, and organ toxicity, and no strategy has yet demonstrated a clear benefit for GVHD-free survival. Orca-T is an investigational cellular product comprising stem and immune cells that leverages highly purified donor regulatory T cells to control alloreactive immune responses. Unlike point-of-care graft engineering approaches, Orca-T is produced in a central GMP laboratory and has been successfully distributed to multiple centers across in the U.S. Early clinical trials using Orca-T showed a good safety profile, promising GVHD control, and potentially improved immune reconstitution. Here, we present trial results from both a single-institution Phase 1/2 trial that has completed enrollment and an ongoing multicenter Phase 1b trial. METHODS As of 28 July 2021, 113 patients aged 18-72 have received Orca-T for AML, ALL, MDS, lymphoma, or myelofibrosis. We present here data from 80 patients that have ≥90 days follow-up. 28 and 52 patients, respectively, received Orca-T followed by single-agent GVHD prophylaxis on a single-center Phase 2 study (NCT01660607) and a multicenter Phase Ib (NCT04013685). Orca-T products were derived from HLA-matched related (n=46) or unrelated (n=34) donors. Patients received a variety of myeloablative conditioning regimens (e.g., non-TBI, n=66; TBI-based, n=14) followed by single-agent PPX with either tacrolimus (n=73) or sirolimus (n=7). Median follow-up for these patients is 541 days (single-center) and 248 days (multicenter). We identified a contemporaneous SOC cohort, and we reported on their clinical outcomes at Stanford (n=95) with both matched related (n=52) and unrelated (n=43) transplant recipients who received unmanipulated PBSC products (median f/u 546) and methotrexate plus tacrolimus prophylaxis. RESULTS The Orca-T investigational cell therapy was manufactured reliably, delivered in less than 72 hours for all patients, and every patient enrolled received Orca-T. The Treg drug product was characterized by high Treg purity of 93.8% +/- 3.1% and a dose of 2.6 +/- 0.4 x 106 per kg (equivalent between trials). An Orca-T product was produced and infused for all patients, and there were no logistics failures or infusion reactions. All patients engrafted and Orca-T patients showed earlier neutrophil (median of 12 days vs. 14 days, p On the single-center, Phase 2 clinical trial study at Stanford there is evidence of improved 1-year GVHD and relapse-free survival (GRFS) which was 77% (CI 51-88%) for Orca-T patients vs 34% (CI 25-44%) with SOC (Figure 1A). We observed improved rates of >grade 2 acute GVHD at Day +180 (aGVHD, 14% versus 33%), moderate-to-severe chronic GVHD at 1 year (4% versus 42%) and NRM at 1 year (0% versus 13%). Relapse-free (RFS) and overall survival (OS) trended upwards for Orca-T. Severe infectious complications were rare. Key clinical results from both Orca-T trials are summarized in Table 1; 23 of 80 patients had ≥1 year follow-up. Consistent with findings from the single-institution study, on the multicenter study, rates of moderate-to-severe cGVHD and non-relapse mortality were low at 1-year post-transplant at 3% and 4%, respectively. For all patients who received Orca-T across both studies, we observed GRFS of 72% (Figure 1B), RFS of 78%, and OS of 91% at 1 year. These survival rates compare favorably to the contemporaneous SOC control (33%, 71% and 78%, respectively). Immune reconstitution in Orca-T patients with single agent tacrolimus appears similar to SOC except for observable differences in the IL-2 pathway. CONCLUSIONS Manufacture of high precision Orca-T investigational cell therapy drug products was scaled in a central GMP with reliable distribution to centers. Patients that received Orca-T and single-agent PPX showed significantly reduced aGVHD, cGVHD and NRM. Orca-T shows promise to improve GRFS and other transplant outcomes. Orca-T has been granted Regenerative Medicine Advanced Therapy status by the FDA, and a phase 3 prospectively, randomized study is planned. Figure 1 Figure 1. Disclosures Gandhi: Gamida Cell: Consultancy, Membership on an entity's Board of Directors or advisory committees; CareDx Inc: Honoraria. Muffly: Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy; Astellas, Jasper, Adaptive, Baxalta: Research Funding; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding. Shiraz: Kite Pharma-Gilead: Research Funding. Mehta: Kadmon: Research Funding; Incyte: Research Funding; CSLBehring: Research Funding; Syndax: Research Funding. McGuirk: Allovir: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Gamida Cell: Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Juno Therapeutics: Consultancy, Honoraria, Research Funding; EcoR1 Capital: Consultancy; Bellicum Pharmaceuticals: Research Funding; Pluristem Therapeutics: Research Funding; Fresenius Biotech: Research Funding; Astelllas Pharma: Research Funding; Novartis: Research Funding. Waller: Verastem Oncology: Consultancy, Research Funding; Cambium Oncology: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Arai: Magenta Therapeutics: Research Funding. Rezvani: US Department of Justice: Consultancy; Nohla Therapeutics: Other: One-time scientific advisory board; Pharmacyclics-Abbvie: Research Funding; Kaleido: Other: One-time scientific advisory board. Weng: Kite Pharma: Research Funding. Miklos: Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Pharmacyclics: Patents & Royalties. Frank: Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding; Allogene Therapeutics: Research Funding. Fernhoff: Orca Bio: Current Employment. Putnam: Orca Bio: Current Employment. McClellan: Orca Bio: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Shaw: Orca bio: Consultancy; mallinkrodt: Other: payments. Abedi: Seattle Genetics: Speakers Bureau; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Speakers Bureau. Meyer: Triursus Therapeutics: Current holder of stock options in a privately-held company; GigaImmune: Current holder of stock options in a privately-held company; Orca Biosystems: Research Funding; Indee, Jura: Consultancy.

Introduction: As the use of CAR-T cell therapy grows, there is an increased need to understand its impact on the patient experience, especially symptom burden and cognitive function. While the immediate side-effects of CAR-T therapy have been reported, our study aims to describe the longitudinal impact of CAR-T therapy on patients' quality of life (QoL), including patient-reported cognitive function and performance-based cognition, which are not well understood. Methods: Patients with hematologic malignancies undergoing CAR-T therapy were prospectively recruited from two academic centers. The primary endpoint was feasibility of completing longitudinal PRO assessments and PBM of cognition. NIH PROMIS measures assessed physical, mental, cognitive, and social health. PROMIS measures use the t-score metric, where 50 is the average in the U.S. population and a 5 point (0.5 SD) change was considered clinically meaningful. The NIH Toolbox Cognition Battery measured 6 constructs of cognition, scored on the t-score metric (10 point = 1SD, change considered clinically meaningful). Exploratory analyses described change from baseline. PROMIS measures were completed at baseline, 7 and 14 days, 1, 3, 6, and 12 months (mo) after CAR-T. The Toolbox was assessed at baseline, 1 month, and 12 months. Due to COVID restrictions on in person research, the Toolbox could not be assessed for the first 13 patients. Results: From 8/2020 to 6/2021, 28 patients have been enrolled. Baseline, day 7, day 14, 1 mo, 3 mo, and 6 mo data were available in 27, 20, 21, 23, 15 (10 not yet reached), and 9 (16 not yet reached) patients, respectively. The mean age was 57 years (range 27-78); 44% were female. Race distribution was: Caucasian 75%, Asian 8%, Hawaiian/Pacific Islander 4% and other race 8%; 21% were Hispanic ethnicity. Patients received CAR-T for diagnoses of NHL (75%), MM (17%), and ALL (13%). CRS was seen in 86% (all grade 1-2), neurotoxicity (ICANS) in 34% (grade 1-2: N=5 and grade > 3: N=5). PROMIS questionnaires were completed in >70% of patients across all timepoints with current follow-up; thus it was feasible to collect these data at frequent intervals after CAR-T. Mean baseline PROMIS t-scores (N=27) were similar to the average US population in all domains (fatigue: 53, sleep: 52, pain: 52, anxiety: 53, depression: 49) except for decreased physical function (44) among patients (Fig 1a-b). Physical function, fatigue, and pain interference worsened during the first month but returned to baseline by month 3 (Fig 1a-b). PBM of cognition (NIH Toolbox) were assessed at baseline in 15 pts and 1 mo in 8 patients (4 incomplete, 3 not reached timepoint). The toolbox requires in-person administration and takes 35 minutes, but has been completed in 75% of evaluable patients. At baseline, the mean total composite score was 65 th percentile and t-score was 57; mean fluid composite score was 50 th percentile and t-score was 50; mean crystallized composite score was 69 th percentile and t-score was 58 (fluid composite score measures ability to reason, crystallized composite score measures accrual of knowledge over time, Weintraub et al Neurology 2013). Little change in scores was seen in language domains and some increase (not clinically significant) was seen in constructs on attention, executive function, and episodic memory. While not significant, a trend towards worsening working memory and processing speed and a trend towards worsening t-scores for all composite scores was seen (Figure 1c). 2 patients with neurotoxicity grade 3 and available baseline and 1-mo Toolboxes were noted to have decreases in all composite scores (clinically significant in 1). Patients did not self-report changes in cognitive function over 6 months (Fig 1d). Conclusion: This study reports early data from longitudinal neurocognitive assessments and PROs in patients undergoing CAR-T. It is feasible for patients undergoing CAR-T to complete PROMIS surveys (PROs) and NIH cognitive Toolboxes (performance-based test). Early and frequent PRO surveys captured initial worsening in physical function, fatigue, and pain interference that returned to baseline by month 3. There was no change in patient-reported cognitive function over time, but using PBM cognition testing, we noted a trend towards worsening cognition in some domains. Continued patient accrual and longer follow up will allow assessment of degree and persistence of worsened PBM cognition associated with CAR-T. Figure 1 Figure 1. Disclosures Frank: Allogene Therapeutics: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding. Shah: Lily: Consultancy, Honoraria, Research Funding; Miltenyi Biotec: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy; Legend: Consultancy; Kite: Consultancy; Incyte: Consultancy; Umoja: Consultancy. D'Souza: Imbrium, Pfizer, BMS: Membership on an entity's Board of Directors or advisory committees; Janssen, Prothena: Consultancy; Sanofi, Takeda, Teneobio, CAELUM, Prothena: Research Funding. Miklos: Pharmacyclics: Patents & Royalties; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees. Muffly: Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding; Astellas, Jasper, Adaptive, Baxalta: Research Funding. Sidana: Janssen: Consultancy, Research Funding; Magenta Therapeutics: Consultancy, Research Funding; Allogene: Research Funding; BMS: Consultancy.

Introduction: CAR-T cell therapy is associated with extra-ordinary costs with estimates of as much as $1.5 million in some patients, including the high list-price for the CAR-T product, additional costs of inpatient stay, toxicity management and outpatient follow-up. As a result, CAR-T therapy may be associated with financial toxicity for patients due to high costs, as well as the financial strain of travel and/or temporary relocation. To date, there are no published studies assessing financial toxicity among CAR-T patients. Methods: Adult patients with hematologic malignancies receiving CAR-T therapy (commercial and clinical trial products) were prospectively recruited from two academic centers to this longitudinal, mixed methods study evaluating financial toxicity in CAR-T recipients. Patients completed questionnaires and telephone interviews prior to CAR-T, 28 days (questionnaire only), 90 days, and 180 days after treatment. The questionnaire included the Comprehensive Score for Financial Toxicity (COST-FACIT), a validated questionnaire with 12 questions on financial stressors of cancer care. Eleven of the 12 items are used to create a summary score ranging from 0 to 44, with higher scores indicating better financial well-being. Validation studies have established clinically meaningful grades of financial toxicity: scores 26+ = grade 0; 14-25 = grade 1; < 14 = grade 2; 0 = grade 3. Semi-structured interviews included questions on financial concerns, impacts on lifestyle, and other medical costs, including questions like "Has the financial cost of your cancer treatments up until this point affected your lifestyle?" Quantitative analysis included COST-FACIT scores summarized as means, ranges, and standard deviations at each timepoint, including longitudinal change from baseline. Qualitative analysis included recording interviews, professional transcription, team-based codebook development, and systematic thematic analysis. Results: We report on 28 patients enrolled from August 2020 to June 2021. For questionnaires, 26 completed baseline, 23 completed day 28 (1 patient died and 2 have not reached this timepoint), 12 completed day 90 (11 have not reached this timepoint), and 8 completed day 180 (16 have not reached this timepoint). For qualitative interviews, 16 completed baseline telephone interviews, 6 completed day 90 (10 have not reach this timepoint), and 4 completed day 180 (12 have not reached this timepoint). Median age was 57.7 years, 52% were male, 21% Hispanic/Latinx, 75% white, 8% Asian, and 4% Hawaiian/Pacific Islander. A majority of patients were (76%) married. COST-FACIT scores were highest at baseline indicating higher financial well-being (mean 29), and also represented the largest range (range 8-44) suggesting patients come into CAR-T at different levels of financial toxicity, ranging from grade 0 to grade 2 (Figure 1). Average financial toxicity at Baseline and Day 28 corresponded to grade 0 toxicity. Financial well-being declined thereafter, elevating to grade 1 toxicity with the average score 25.2 at day 90 and 23.6 at day 180. At Baseline, Day 28, and Day 90 there are patients experience grades 0, 1, and 2 financial toxicity. Qualitative themes include: Insurance, Lodging/Relocation, Work/Income, Nontraditional sources of funding, Discussion with Providers (Table 1). Preliminary assessment of thematic patterns over time supports the quantitative results, with patients expressing little to no financial concerns at baseline, often citing "great insurance", with changes at day 90 recognizing the additional costs not covered by insurance, and uncertainty of insurance coverage. Conclusions: Our results using both quantitative and qualitative methods indicate the financial impact of CAR-T therapy extends beyond the cost of treatment. Patients undergoing CAR-T therapy experience financial toxicity, with its impact worsening with time as the stressors and payments cumulate. These data are important for understanding the full patient experience with CAR-T therapy and emphasize that durable support and resources are needed to help patients with financial toxicity. Concern for financial toxicity may limit access to this therapy and future research should focus on access to therapy based on personal financial concerns and referral patterns. Figure 1 Figure 1. Disclosures Frank: Allogene Therapeutics: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding. Miklos: Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Patents & Royalties; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy. Shah: Umoja: Consultancy; Miltenyi Biotec: Consultancy, Honoraria, Research Funding; Lily: Consultancy, Honoraria, Research Funding; Incyte: Consultancy; Kite: Consultancy; Legend: Consultancy; Epizyme: Consultancy. D'Souza: Imbrium, Pfizer, BMS: Membership on an entity's Board of Directors or advisory committees; Sanofi, Takeda, Teneobio, CAELUM, Prothena: Research Funding; Janssen, Prothena: Consultancy. Muffly: Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy; Astellas, Jasper, Adaptive, Baxalta: Research Funding; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding. Sidana: Allogene: Research Funding; Janssen: Consultancy, Research Funding; BMS: Consultancy; Magenta Therapeutics: Consultancy, Research Funding.

Background Allogeneic (off the shelf) chimeric antigen receptor (CAR) T-cell therapy addresses the logistical challenges, availability (including insufficient T-cell yields from low baseline absolute lymphocyte count), and variable product quality of autologous CAR T therapy. ALLO-501A is a genetically modified anti-CD19 AlloCAR T™ cell product that uses TALEN ® gene editing to disrupt the T-cell receptor alpha constant gene (TRAC) and the CD52 gene to reduce the risk of graft-versus-host disease (GvHD) and permit the use of ALLO-647, an anti-CD52 monoclonal antibody (mAb), for selective and transitory host lymphodepletion (LD). Here we present an update on the preliminary safety, efficacy, and correlative data. ALLO-501A uses Cellectis technologies. Methods ALPHA2 (NCT04416984) is a single-arm, open-label, Phase 1/2 trial of ALLO-501A in patients (pts) with relapsed/refractory (R/R) large B-cell lymphoma (LBCL including [R/R] diffuse LBCL [DLBCL], transformed follicular lymphoma [tFL], marginal zone lymphoma [tMZL], primary mediastinal B-cell lymphoma [PMBCL], follicular lymphoma grade 3B [FL3B]) who received ≥2 prior lines of therapy (including an anthracycline and anti-CD20 mAb), have an ECOG performance status of 0 or 1. Subjects with donor specific antibodies are excluded. Following LD with ALLO-647, fludarabine 30 mg/m 2/d x 3d (F), and cyclophosphamide 300 or 500 mg/m 2/d x 3d (C), either a single (40 [DL1] or 120 [DL2] x 10 6 viable CAR T cells) or consolidation dose of ALLO-501A (DL2) are given. For consolidation dose, pts with ≥stable disease (SD) at day 28 receive consolidation with second ALLO-647 (no chemo) for LD and ALLO-501A (DL2) cell infusion. Results As of July 9, 2021, 20 pts were enrolled; 15 pts were treated with ALLO-501A (12 evaluable and 3 pending D28 assessment); 3 pts pending treatment; 2 pts withdrew due to adverse event (AE)/progressing disease (PD) prior to dosing. Patients were heavily pretreated with advanced-stage disease (Stage III: 4 [22.2%], Stage IV: 8 [44.4%]), median number of prior treatments was 3 with a high of 7. Three pts (16.7%) had primary refractory disease. Safety profile was manageable in both single dose and consolidation cohorts. Events of interest in the single dose cohort have been previously reported (ASCO 2021). In the consolidation cohort (13 enrolled, 9 pts dosed thus far), no cytokine release syndrome (CRS), no GvHD, no immune effector cell-associated neurotoxicity syndrome (ICANS), no dose-limiting toxicities (DLTs), no dose reductions, no Grade (Gr) 3+ infections and no related serious adverse events (SAEs) occurred, and infusion-related reactions were Gr 1. Among all treated, cytopenias were the most common AE and occurred in 72% of pts. Of the 12 evaluable pts (6 each treated in the single dose and consolidation dose cohort), both the overall response rate (ORR) and complete response (CR) were 50% (95% CI: 21.1, 78.9). In the consolidation cohort, both ORR and CR rate were 66.7% (95% CI: 22.3, 95.7) with 3/3 partial responses (PRs) converting to CR after consolidation; 1 pt had CR at days 28 and 56 post consolidation and 2 pts had PD at month 1 and did not receive consolidation. In single dose cohort, 2 pts have ongoing CR at 9 and 12+ months. CAR T expansion was greater in pts who achieved a CR with a geometric mean area under the curve (AUC) at D1-28 of 206,990 copies/ug*days (n=6; GSD 4.94) compared to pts who did not achieve a CR with AUC at D1-28 of 3,571 copies/ug*days (n=3; GSD 2.41). Pts who received the consolidation dose continued to have CAR T expansion after the 2 nd CAR T infusion with geometric mean AUC from D30-56 of 92,893 copies/ug*days (n=4; GSD 5.42). Conclusions ALLO-501A with consolidation dosing demonstrated comparable safety and an improved efficacy profile compared to single dosing with all 4 pts who received consolidation remaining in CR. Persistence of CAR T at D28 and expansion after consolidation dose was observed in addition to the observed deepening of responses in pts whose initial response was PR. Additional follow up is needed to determine whether consolidation also improves the durability of response. Consolidation was well tolerated and given the generally favorable overall safety profile, ALLO-501A may have the potential to be given in the outpatient setting. Enrollment is ongoing. Updated efficacy and follow-up will be presented at the meeting. Currently, an ALLO-501A Phase 2 trial is planned. Disclosures Locke: Cowen: Consultancy; Umoja: Consultancy, Other; Wugen: Consultancy, Other; Takeda: Consultancy, Other; Novartis: Consultancy, Other, Research Funding; Janssen: Consultancy, Other: Scientific Advisory Role; Bluebird Bio: Consultancy, Other: Scientific Advisory Role; BMS/Celgene: Consultancy, Other: Scientific Advisory Role; Calibr: Consultancy, Other: Scientific Advisory Role; Amgen: Consultancy, Other: Scientific Advisory Role; GammaDelta Therapeutics: Consultancy, Other: Scientific Advisory Role; Cellular Biomedicine Group: Consultancy, Other: Scientific Advisory Role; Kite, a Gilead Company: Consultancy, Other: Scientific Advisory Role, Research Funding; Legend Biotech: Consultancy, Other; Iovance Biotherapeutics: Consultancy, Other: Scientific Advisory Role; EcoR1: Consultancy; Allogene Therapeutics: Consultancy, Other: Scientific Advisory Role, Research Funding; Emerging Therapy Solutions: Consultancy; Gerson Lehrman Group: Consultancy; Moffitt Cancer Center: Patents & Royalties: field of cellular immunotherapy. Neelapu: Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene Therapeutics, Cell Medica/Kuur, Incyte, Precision Biosciences, Legend Biotech, Adicet Bio, Calibr, Unum Therapeutics and Bluebird Bio: Honoraria; Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene, Kuur, Incyte, Precision BioSciences, Legend, Adicet Bio, Calibr, and Unum Therapeutics: Other: personal fees; Kite, a Gilead Company, Bristol Myers Squibb, Merck, Poseida, Cellectis, Celgene, Karus Therapeutics, Unum Therapeutics (Cogent Biosciences), Allogene, Precision BioSciences, Acerta and Adicet Bio: Research Funding; Takeda Pharmaceuticals and related to cell therapy: Patents & Royalties. Hamadani: Janssen, Incyte, ADC Therapeutics, Omeros, Morphosys, Kite: Consultancy; Sanofi, Genzyme, AstraZeneca, BeiGene: Speakers Bureau; Takeda, Spectrum Pharmaceuticals and Astellas Pharma: Research Funding. Frank: Allogene Therapeutics: Research Funding; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding. Popplewell: Novartis: Other: Travel; Pfizer: Other: Travel; Hoffman La Roche: Other: Food. Abramson: Bluebird Bio: Consultancy; Kymera: Consultancy; BeiGene: Consultancy; Incyte Corporation: Consultancy; Astra-Zeneca: Consultancy; Allogene Therapeutics: Consultancy; Seagen Inc.: Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Novartis: Consultancy; Morphosys: Consultancy; Kite Pharma: Consultancy; C4 Therapeutics: Consultancy; Genmab: Consultancy; EMD Serono: Consultancy; Bristol-Myers Squibb Company: Consultancy, Research Funding; Genentech: Consultancy. Munoz: Pharmacyclics/Abbvie: Consultancy, Research Funding, Speakers Bureau; Bayer: Consultancy, Research Funding, Speakers Bureau; Gilead/Kite Pharma: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy; Janssen: Consultancy, Research Funding, Speakers Bureau; Juno/Celgene: Consultancy, Research Funding, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Kyowa: Consultancy, Honoraria, Speakers Bureau; Alexion: Consultancy; Beigene: Consultancy, Speakers Bureau; Fosunkite: Consultancy; Innovent: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding, Speakers Bureau; Debiopharm: Consultancy; Karyopharm: Consultancy; Genmab: Consultancy; ADC Therapeutics: Consultancy; Epizyme: Consultancy; Servier: Consultancy; Merck: Research Funding; Portola: Research Funding; Incyte: Research Funding; Genentech: Research Funding, Speakers Bureau; Millennium: Research Funding; Targeted Oncology: Honoraria; OncView: Honoraria; Physicians' Education Resource: Honoraria; Roche: Speakers Bureau; AstraZeneca: Speakers Bureau; Verastem: Speakers Bureau; Acrotech/Aurobindo: Speakers Bureau. Shin: Allogene Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Loomis-Navale: Allogene: Current Employment, Current equity holder in publicly-traded company. Miklos: Pharmacyclics, Amgen, Kite, a Gilead Company, Novartis, Roche, Genentech, Becton Dickinson, Isoplexis, Miltenyi, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Biosciences, Adicet, Adaptive Biotechnologies: Research Funding; Kite, a Gilead Company, Amgen, Atara, Wugen, Celgene, Novartis, Juno-Celgene-Bristol Myers Squibb, Allogene, Precision Bioscience, Adicet, Pharmacyclics, Janssen, Takeda, Adaptive Biotechnologies and Miltenyi Biotechnologies: Consultancy; Adaptive Biotechnologies, Novartis, Juno/Celgene-BMS, Kite, a Gilead Company, Pharmacyclics-AbbVie, Janssen, Pharmacyclics, AlloGene, Precision Bioscience, Miltenyi Biotech, Adicet, Takeda: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Patents & Royalties. OffLabel Disclosure: Discussion of fludarabine and cyclophosphamide in combination with ALLO-647 as conditioning regimen prior to administration of ALLO-501A in patients with R/R LBCL.

Background Treatment with chimeric antigen receptor (CAR) T cell therapies have shown dramatic, often durable responses for relapsed/refractory B-cell malignancies. However, it can be associated with significant side effects such as cytokine release syndrome (CRS), immune effector-cell associated neurotoxicity syndrome (ICANS) and life-threatening consumptive coagulopathies. The underlying pathobiology of such hemostatic defects and their distinct clinical sequelae remains obscure. This retrospective study aims at quantifying CAR T therapy associated bleeding and thrombotic complications and their association with CRS, ICANS, and laboratory derangements. Methods 130 adult patients with DLBCL or B-ALL treated between 2017-2020 with CD19 CAR-T therapy axicabtagene ciloleucel (N=90) or a bispecific CD 19/22 CAR construct utilizing 4-1BB costimulatory domains (N=40) were analyzed to determine dynamics of coagulation parameters and platelet counts as well as incidences of bleeding or thrombosis in the first three months after CAR T infusion. Events were included if graded ≥ 2 or if intervention was required. Platelet counts and coagulation parameters were collected prior to lymphodepletion (pre-LD), day 0, 3, 7, 14, 21, 28, 60 and 90. Results 12 (9.2%) and 8 (6.2%) patients developed bleeding and thrombotic complications in the first three months after CAR-T infusion, respectively. Events are characterized in Figure 1. All bleeding events occurred between days 0-30 (median 17.5, range 8-30), while thrombotic events occurred between days 2-91 (median day 29, range, 2-91). Two (1.5%) patients experienced both bleeding and thrombosis. Bleeding events coincided with the onset of thrombocytopenia and hypofibrinogenemia, and patients who bled had lower platelet (median 22.5 vs. 47 K/uL; p=0.03) and fibrinogen (median 151 vs. 351 ug/mL; p=0.007) nadirs in the first 30 days compared to those without bleeding. Temporally, the lowest median platelet nadir occurred at day 7 in patients with bleeding events vs. day 21 in patients without bleeding, while timing of fibrinogen nadirs were at day 21 in both. Patients with bleeding episodes were more likely to be older (median age: 70 vs. 60 yrs, p=0.03), have thrombocytopenia prior to lymphodepletion therapy (median 117.5 vs. 174.5 K/uL, p=0.01), and have elevated LDH (lymphoma subgroup; p=0.07). Other lab derangements in the first 30 days seen more frequently in patients with bleeding included prolonged thrombin time (TT) (21% vs. 6%; p=0.02), PT (16% vs. 5%; p=0.06), and elevated d-dimer (16% vs. 3%; p=0.01) indicative of a consumptive process. Thrombotic events were not significantly associated with elevated or peak d-dimer values (median 4.97 vs. 2.37 ug/mL, p=0.20). Interestingly, occurrence or severity of CRS was not associated with bleeding or thrombotic events, nor was it associated with marked derangements in coagulation abnormalities. However, higher grade ICANS (grade > 3) was associated with bleeding (42% vs. 15%; p=0.038), thrombosis (50% vs. 16%; p=0.03), and evidence of endothelial activation including PT prolongation (78% vs. 35%; p 13 (10%) patients received anticoagulation for prophylaxis or therapeutic indications that predated CAR T infusion. Four started anticoagulation secondarily for thrombotic events after CAR-T infusion, and one received tissue plasminogen activator (tPA) for an acute stroke. In this group, no patients developed bleeding complications from anticoagulation. Conclusion Both bleeding (9.2%), and thrombotic (6.2%) events are observed after CAR T cell therapy, with bleeding limited to the first month in our cohort. Notably, ICANS was uniquely associated with PT prolongation, hypofibrinogenemia, and increased fibrin degradation, in addition to both bleeding and thrombosis. These results suggest that a systemic coagulopathy coincides with high grade ICANS and whether these neurologic events truly represent sequelae of widespread vascular dysfunction warrants further investigation. Anticoagulation was safe in the patients whom it was indicated. Risk factors for bleeding and thrombotic complications should be studied prospectively to develop risk-assessment models and clinical guidelines for management of bleeding and thrombosis (including prophylaxis) during CAR T therapy. Disclosures Muffly: Adaptive: Research Funding; Servier: Research Funding; Amgen: Consultancy. Negrin:BioEclipse Therapeutics: Current equity holder in private company; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; KUUR Therapeutics: Consultancy; Biosource: Current equity holder in private company; Amgen: Consultancy; UpToDate: Honoraria. Shizuru:Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Meyer:Orca Bio: Research Funding. Shiraz:Kite, a Gilead Company: Research Funding; ORCA BioSystems: Research Funding. Rezvani:Pharmacyclics: Research Funding. Mackall:Apricity Health: Consultancy, Current equity holder in private company; NeoImmune Tech: Consultancy; Nektar Therapeutics: Consultancy; Allogene: Current equity holder in publicly-traded company; BMS: Consultancy; Lyell Immunopharma: Consultancy, Current equity holder in private company. Miklos:Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding. Sidana:Janssen: Consultancy.

Background: Historically, the survival of adult patients with acute lymphoblastic leukemia (ALL) relapsing after allogeneic hematopoietic cell transplantation (HCT) was dismal, with fewer than 10% surviving long-term (Fielding et al Blood 2007). In the last five years, the availability of targeted immunotherapies including blinatumomab (blin), inotuzumab ozogamicin (IO), and chimeric antigen T-cell receptor (CART) therapy has expanded the opportunity for effective salvage of relapsed/refractory ALL. We hypothesized that the expanding therapeutic landscape has resulted in superior survival following post-HCT relapse in adult ALL in the targeted immunotherapy era. Methods: We performed a retrospective analysis of adults receiving first allogeneic HCT for ALL between 2008-2019 at Stanford University; patients were stratified by time period of HCT: 2008-2013 (earlier era) vs 2014-2019 (recent immunotherapy era). Descriptive statistics characterized the study cohort; chi-square test was used to evaluate differences in characteristics and treatments based on time period transplanted. Kaplan Meier method was used to determine overall survival (OS); log-rank tested significance between time periods. Follow-up time of the earlier time period was truncated to 5.4 years to match maximum follow-up time of the more recent time period. Results: Of the 285 adult ALL patients transplanted (N=119, 2008-2013; N=166, 2014-2019), 81 (28%) experienced disease relapse following HCT and represent the analytic cohort. Post-HCT relapse occurred in 39 (33%) transplanted between 2008-2013 and 42 (25%) transplanted between 2014-2019. The median time to relapse following HCT was 7.72 months (95% CI, 3.88-14.0), and did not significantly differ between time periods. Baseline patient and transplant characteristics were similar across the two time periods (Table 1); however, relative to the earlier time period, patients transplanted during the more recent time period were less likely to be transplanted with active disease (26% vs 2%), and more likely to receive cord blood as a stem cell source (0 vs 10%). The median overall survival (OS) for the entire cohort following post-HCT relapse was 9.93 months (95% CI, 7.07-12.73). However, the median OS from relapse was 7.99 months (95% CI, 3.30-11.6) for patients transplanted in the earlier era, while the median OS for patients relapsing in the recent era was 15.75 months (95% CI, 9.24-26.4), P Conclusion: In this large cohort of adults transplanted for ALL over the last decade, we show that the OS of ALL patients relapsing after HCT has significantly improved, coinciding with a substantial increase in the availability and utilization of novel therapies in this setting. Additional studies are needed to understand the optimal therapeutic intervention for post-HCT relapse in adult ALL. Disclosures Meyer: Orca Bio: Research Funding. Miklos:Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding. Negrin:UpToDate: Honoraria; Biosource: Current equity holder in private company; Amgen: Consultancy; BioEclipse Therapeutics: Current equity holder in private company; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; KUUR Therapeutics: Consultancy. Rezvani:Pharmacyclics: Research Funding. Shizuru:Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Sidana:Janssen: Consultancy. Shiraz:ORCA BioSystems: Research Funding; Kite, a Gilead Company: Research Funding. Muffly:Amgen: Consultancy; Adaptive: Research Funding; Servier: Research Funding.

Background: Characterization of T-cell receptor (TCR) diversity and dynamics is increasingly critical to understanding therapeutic immune responses targeting tumors. Current TCR profiling methods generally require invasive tissue biopsies that capture a single snapshot of immune activity or are limited by the sheer diversity of the circulating TCR repertoire. In theory, T-cells with the greatest turnover could best reflect pivotal immune dynamics from both circulating and tissue-derived compartments, including non-circulating tissue-resident memory T-cells (Trm). To noninvasively capture such responses in the blood, we developed and benchmarked a high-throughput TCR profiling approach using plasma, optimized for the fragmented nature of cfDNA and the non-templated nature of rearranged TCRs. We then applied this method for residual disease monitoring in mature T-cell lymphomas (TCL) without circulating disease and for characterizing immune dynamics after anti-CD19 chimeric antigen receptor (CAR19) T-cell therapy of B-cell lymphomas with axicabtagene ciloleucel. Methods: We developed SABER (Sequence Affinity capture & analysis By Enumeration of cell-free Receptors) as a technique for TCR enrichment and analysis of fragmented rearrangements shed in cfDNA and applied this method using Cancer Personalized Profiling by Deep Sequencing (CAPP-Seq). We used SABER to profile a total of 381 samples (300 cfDNA and 81 PBMC samples) from 75 lymphoma patients and 18 healthy controls. After mapping sequencing reads (hg38) to identify candidate rearrangements within TCR loci, unique cfDNA fragments were resolved by a novel strategy to define consensus of unique molecular identifiers clustered by Levenshtein distances, followed by CDR3-anchoring for enumeration of final receptor clonotypes. SABER thus leverages information from fragmented TCRs, a critical requirement for cfDNA, to make V gene, CDR3, and J gene assignments after deduplication-mediated error-correction. We benchmarked SABER against established amplicon-based TCR-β targeted sequencing (LymphoTrack, Invivoscribe) and repertoire analysis methods (MiXCR; Bolotin et al, 2015 Nature Methods) when considering both cfDNA and PBMC samples from healthy adults and TCL patients. We assessed SABER performance for tracking clonal molecular disease in patients with mature TCLs from both cellular and cell-free circulating compartments (n=9). Malignant TCL clonotypes were identified in tumor specimens using clonoSEQ (Adaptive Biotechnologies). Finally, we evaluated TCR repertoire dynamics over time in 66 DLBCL patients after CAR19 T-cell therapy. Results: SABER demonstrated superior recovery of TCR clonotypes from cfDNA compared to both amplicon sequencing (LymphoTrack, Invivoscribe) and hybrid-capture methods when enumerating receptors using MiXCR (Fig. 1A). When applied to blood samples from TCL patients, SABER identified the malignant clonal TCR-β rearrangement in 8/9 (88.9%) cases, with significantly improved detection in cfDNA (p=0.015, Fig. 1B). Specifically, tumoral TCR clonotype was detectable only in cfDNA in 6 cases (75%), cfDNA-enriched in 1 case (12.5%), and detectable only in PBMCs in 1 case (12.5%). We applied SABER to monitor TCR repertoire dynamics in cfDNA after CAR T-cell therapy of patients with relapsed/refractory DLBCL and observed increased T-cell turnover and repertoire expansion (greater total TCR-β clonotypes) (Fig. 1C). As early as 1-week after CAR19 infusion, TCR repertoire size was significantly correlated both with cellular CAR19 T-cell levels by flow cytometry (p=0.008) as well as with retroviral CAR19 levels in cfDNA (p=2.20e-07) suggesting faithful monitoring of CAR T-cell activity (Fig. 1D). TCR repertoire size one month after infusion was significantly associated with longer progression-free survival (HR 0.246, 95% CI 0.080-0.754, p=0.014). Conclusions: SABER has a favorable profile for cfDNA TCR repertoire capture when compared to existing methods and could thus have potential broad applicability to diverse disease contexts. Given the higher abundance of lymphoma-derived TCRs in cfDNA than intact circulating leukocytes, SABER holds promise for monitoring minimal residual disease in T-cell lymphomas. This approach also holds promise for monitoring T-cell repertoire changes including after CAR T-cell therapy and for predicting therapeutic responses. Disclosures Kurtz: Genentech: Consultancy; Foresight Diagnostics: Other: Ownership; Roche: Consultancy. Kim:Corvus: Research Funding; Eisai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Elorac: Research Funding; Forty Seven Inc: Research Funding; Galderma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Horizon Pharma: Consultancy, Research Funding; Innate Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kyowa-Kirin Pharma: Research Funding; Medivir: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; miRagen: Research Funding; Neumedicine: Consultancy, Research Funding; Portola: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees; Solingenix: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding. Mackall:Lyell Immunopharma: Consultancy, Current equity holder in private company; BMS: Consultancy; Allogene: Current equity holder in publicly-traded company; Apricity Health: Consultancy, Current equity holder in private company; Nektar Therapeutics: Consultancy; NeoImmune Tech: Consultancy. Miklos:Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding. Diehn:Varian Medical Systems: Research Funding; Illumina: Research Funding; Roche: Consultancy; AstraZeneca: Consultancy; RefleXion: Consultancy; BioNTech: Consultancy. Khodadoust:Seattle Genetics: Consultancy; Kyowa Kirin: Consultancy. Alizadeh:Janssen: Consultancy; Genentech: Consultancy; Pharmacyclics: Consultancy; Chugai: Consultancy; Celgene: Consultancy; Gilead: Consultancy; Roche: Consultancy; Pfizer: Research Funding.

Introduction: Disease relapse after allogeneic hematopoietic cell transplantation (HCT) is the main cause for an unsuccessful transplant outcome. The prognosis is generally poor and there is no consensus regarding optimal therapy to restore disease control. We retrospectively analyzed 121 patients with hemato-lymphoid malignancies who had disease relapse after a first HCT (HCT1) and received a subsequent allograft (HCT2) or a donor lymphocyte infusion (DLI). The goal of the analyses was to better understand which clinical features was associated with improved outcomes, and to help define the risk-benefit of these two interventions. Methods: Between September 1, 2009 and December 31, 2019, 550 consecutive patients had disease relapse after HCT1 of which 28 (5%) received HCT2 and 93 (17%) received DLI. Results: The HCT1 baseline characteristics were comparable for both groups (Table1). The median time interval from HCT1 to disease relapse was 8 months (range 1-87). Patients who had disease relapse within 6 months of HCT1 had withdrawal of immune suppression (IS) medication whereas most patients with disease relapse beyond 6 months already had had IS drugs discontinued. DLI was the treatment choice for CML, CLL and plasma cell neoplasms, or for a low level of disease relapse/progression. In the HCT2 cohort, the median age was 56 (range 31-70) and 17 (61%) patients were returned to CR with chemotherapy prior to HCT2. Three patients (11%) received a myeloablative regimen and 23 (82%) received a reduced intensity regimen (RIC). The graft source was mobilized peripheral blood in 26 patients (92%) and 20 (71%) had a different donor at HCT2. Karnofsky performance status was >90% in 11 (39%) patients at HCT2. In the DLI cohort, the median age was 60 (range 22-77) and 48 (52%) were returned to CR prior to the first DLI. Patients received a median of one DLI (range 1-4). The median CD3+ T cell dose was 1.0 X107CD3+/kg (range 0.5-30). Karnofsky performance status was >90% in 56 (67%) patients at time of DLI. Both interventions were well tolerated and the 1-year non-relapse mortality (NRM) was 21% (n=6) for HCT2 and 12% (n=11) for DLI. Acute graft-versus-host disease (aGVHD), grades 2-4, occurred in 39% and 24% of the patients who received HCT2 and DLI. The 3-year cumulative incidence of extensive chronic GVHD was 25% for HCT2 and 23% for DLI. The median follow-up for living patients was 37 months. The median event-free survival (EFS) was 18 months for HCT2 and 5 months for DLI (Fig.1A). The estimated 3-year overall survival (OS) was 60% [95% confidence interval (CI): 39-78] for HCT2 and 30% [95% CI: 21-42] for DLI (Fig.1B). The main causes of death were disease progression (n = 4) and GVHD (n = 4) for the HCT2 cohort. The same was true for the DLI cohort, although death from progressive disease was more common (n = 43 patients) compared to death from GVHD (n = 16 patients). Within the limitations of the small number of patients only one factor in univariate analysis was associated with an improved OS for both HCT2 and DLI and this was attainment of complete donor CD3+ T cell chimerism (>95% donor type) after either intervention. The 3-year OS for patients who attained full donor chimerism was 68% and 66% for HCT2 and DLI, respectively, compared to 33% and 24% for these groups if full donor chimerism was not achieved. The KPS at the time of DLI was significantly associated with improved OS: the median OS was 2, 8 and 19 months when KPS was Conclusion: HCT2 and DLI can both offer long-term disease control for disease relapse after HCT1 albeit only a minority of patients receive these interventions. In our analysis, HCT2 and DLI were well tolerated and the risks of NRM and GVHD appear similar to HCT1. Long-term OS for HCT2 is achieved for about half of the patients when using a RIC and when the patient is returned to CR prior to the intervention. For DLI, a higher performance status and a longer remission after HCT1 were both associated with improved long-term survival. Conditions that enable attainment of full donor chimerism are important to maximize graft-versus-tumor effect for both HCT2 and DLI. Disclosures Muffly: Servier: Research Funding; Amgen: Consultancy; Adaptive: Research Funding. Rezvani:Pharmacyclics: Research Funding. Sidana:Janssen: Consultancy. Shiraz:Kite, a Gilead Company: Research Funding; ORCA BioSystems: Research Funding. Meyer:Orca Bio: Research Funding. Shizuru:Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Miklos:Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding. Negrin:Biosource: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy; BioEclipse Therapeutics: Current equity holder in private company; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; Amgen: Consultancy.

Introduction: Patients with T-cell lymphoma have variable clinical manifestations and outcomes depending on the histology and their response to therapies. However, the overall outcomes are not as good as their B-cell lymphoma counterpart with induction chemotherapy alone. Therefore, autologous transplant is often used as consolidation in first remission or at relapse because of the poor outcomes with conventional therapy. We have reported previously on Stanford experience of these patients who underwent autologous transplant before 2007 (BBMT 2008, 14:741). Here, we reported a retrospective review of patients in the modern era (2008-2018) with emphasis on the impact of pre-transplant disease status on outcomes and post-transplant relapse management. Method: Between July 1, 2008 and July 31, 2018, 102 consecutive patients with T-cell lymphoma received high dose chemotherapy/autologous hematopoietic cell rescue at Stanford and constitute the study cohort (Figure 1). This study cohort was selected for adequate follow-up (>2 years) after transplant. Progression free survival (PFS) and overall survival (OS) was estimated from the date of transplant using the Kaplan-Meier method. PFS and OS were compared between groups with different pre-transplant disease status based on response to the last pre-transplant therapies (CR1 vs. PR1 vs. CR2). Result: This study cohort included patients with peripheral T-cell lymphoma, non-specified (n=21), angioimmunoblastic T-cell lymphoma (n=50), ALK-negative anaplastic large-cell lymphoma (n=14), ALK-positive anaplastic large-cell lymphoma (n=5), extranodal NK/T cell lymphoma (n=9), enteropathy-type T-cell lymphoma (n=1), adult T-cell leukemia/lymphoma (n=1) and hepatosplenic T-cell lymphoma (n=1). It had a male/female ratio of 61/41, and a median age of 58 years (range 23-71). At diagnosis the majority of the patients had stage III/IV disease (70%) and B symptoms (56%). The median time from diagnosis to transplant was 8.1 months (range 4-176). The majority of patients were in first complete remission (CR1, n=79) at the time of transplant, while others were in PR1 (n=11) or in CR2 (n=12) from last pre-transplant therapies. Ninety-one (89%) patients received high dose cyclophosphamide/carmustine/etoposide(CBV) and 11 patients received high dose carmustine/etoposide/cytarabine/melphalan (BEAM) prior to autograft infusion. Median follow-up post-transplant was 36.8 months (range 0.7-130) for the entire cohort. The estimated 3-year PFS and OS were 60% (95% CI 49-68%) and 75% (95% CI 65-82%), respectively (Figure 2A). Patients who were in CR1 had significantly better median PFS compared to patients in PR1 or CR2 (7.04 vs 1.19 years, p=0.039; 7.04 vs 0.48 years p=0.004, Figure 2B). The estimated 3-year PFS were 67% (95% CI 55-76%), 36% (95% CI 11-63%), and 29% (95% CI 8-56%) for the CR1, PR1 and CR2 groups respectively. Patients who were in CR1 also had significantly better median OS compared to patients in PR1 or CR2 (not reached vs 2.30 years, p=0.018; not reached vs 3.76 years p=0.045, Figure 2C).The estimated 3-year OS were 82% (95% CI 71-89%), 44% (95% CI 14-70%), and 53% (95% CI 21-78%) for the CR1, PR1 and CR2 groups respectively. In this cohort, there were no significant differences in either PFS or OS between different histology. Forty patients experienced disease relapse after transplant. The majority (n=28, 70%) of these patients received additional therapies including chemotherapy (n=13), brentuximab vedotin (n=12), HDAC inhibitor (n=7), and radiation (n=3) with a median systemic therapy of 2 (range 1-5). Thirteen patients eventually underwent allogeneic hematopoietic cell transplantation. The median OS after post-transplant relapse was 21.3 months (Figure 3). Both brentuximab vedotin and allogeneic transplant seemed to provide prolonged survival for these relapsed patients, with estimated 2-year post-relapse OS were 75% (95% CI 13-96%) and 63% (95% CI 28-84%) for the two groups respectively. Conclusion: Autologous transplant remains to be a good option as consolidation for patients with T-cell lymphoma, mostly in patients with first complete remission. While close to 40% of the patients experienced relapse after autologous transplant, additional therapies such as brentuximab vedotin or/and allogeneic transplant can provide long-term benefit for these patients. Disclosures Shizuru: Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Shiraz:Kite, a Gilead Company: Research Funding; ORCA BioSystems: Research Funding. Muffly:Servier: Research Funding; Amgen: Consultancy; Adaptive: Research Funding. Sidana:Janssen: Consultancy. Meyer:Orca Bio: Research Funding. Rezvani:Pharmacyclics: Research Funding. Miklos:Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Allogene Therapeutics Inc.: Research Funding; Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding. Negrin:Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; Biosource: Current equity holder in private company; Amgen: Consultancy; BioEclipse Therapeutics: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy.

Introduction: Given similar overall survival (OS) seen in patients receiving delayed vs. early autologous stem cell transplant (ASCT) in multiple myeloma (MM), some patients are electing to proceed with transplant at relapse instead of with upfront therapy. However, there is limited data in the era of novel therapies on expected disease control and outcomes in MM when ASCT is done for relapsed disease. The objective of this single-center retrospective study was to evaluate the outcomes of ASCT in patients with relapsed MM. Methods: Between January 1, 2010, and November 31, 2019, 168 consecutive patients with relapsed MM received ASCT at our center and constitute the study cohort. Progression free survival (PFS) was estimated from start of therapy at relapse until progression or death. PFS-PRIOR represents PFS of the immediate prior line of therapy before current relapse for which ASCT was pursued. OS was estimated from start of therapy at relapse and also from diagnosis until death. Results: Of the 168 patients, the majority underwent transplant in first relapse (69%, n=116) and the majority had not received a prior transplant (80%, n=135). Baseline and treatment characteristics of the cohort are shown in Table 1. High-risk cytogenetics were seen in 27% and ISS stage III disease in 15%. Median PFS-PRIOR was 20 months (range 2-228). The induction regimen used before ASCT included a doublet in 32%, a triplet in 56%, a quadruplet in 1.5% and a chemotherapy-based regimen in 9% of patients. Stem cell collection was done after relapse in 72% of the cohort. Conditioning regimen included melphalan 200 mg/m2 in 90% patients, including melphalan 200 mg/m2+BCNU in 55%. Median time to neutrophil and platelet engraftment was 11 and 16 days, respectively. Response after ASCT was very good partial response or better in 82% (n=124) of patients. Maintenance therapy was given in 35% (n=56) of patients after ASCT, with 73% patients receiving IMiD maintenance and a median duration of maintenance of 7 months (range 1-41). Survival: Median follow-up of this cohort was 61 months. Median PFS from start of treatment was 28 months. Median OS from start of treatment was 69 months and from diagnosis was 118 months. Two patients (1%) died within the first 3 months of complications related to transplant. As expected, patients who received ASCT at first relapse had a longer PFS of 33 months compared to 22 months when the transplant was done at second or later relapse, p=0.003 (Fig. 1A). OS from treatment start in patients undergoing transplant at first relapse was 82 months and those undergoing ASCT at second or later relapse was 45 months, p=0.004 (Fig. 1B). However, there was no difference in OS from diagnosis in these two groups (118 vs 134 months, p=0.97). Subgroup analysis was done in patients undergoing transplant at first relapse. Patients who had a PFS-PRIOR of ≥36 months had OS of 91 months compared to 62 months for those who experienced a shorter PFS-PRIOR, p=0.03. PFS in the subgroup of patients without prior ASCT undergoing transplant in first relapse (N=96) was 30 months. Multivariate Cox proportional hazards analysis was done for PFS and OS incorporating the following covariates: high risk cytogenetics, Karnofsky performance status (KPS), relapse number, PFS-PRIOR ≥36 months, response at ASCT, and use of maintenance. ASCT in first relapse was associated with better PFS with a hazard ratio (HR) of 0.63 (95% CI 0.42-0.94, p=0.03) and OS (HR 0.59, 95% CI 0.35-0.99, p=0.04). Achieving a PFS-PRIOR of ≥36 months was associated with improved PFS (HR 0.62, 95% CI 0.39-0.99, p=0.04) and OS (HR 0.41, 95% CI 0.21-0.82, p=0.01). Better KPS was also associated with longer PFS (HR 0.61, 95% CI 0.41-0.91, p=0.01) and OS (HR 0.52, 95% CI 0.31-0.86, p=0.01). Progressive disease at transplant was, as expected, associated with worse PFS (HR 3.28, 95% CI 1.89-5.70, p Conclusions: This study provides comprehensive data on expected outcomes and prognostic factors amongst patients with MM undergoing ASCT at relapse, with median PFS and OS being 28 and 69 months in a cohort where only a third of patients received maintenance therapy. Disease response at transplant, PFS-PRIOR and KPS were prognostic for survival. These data can serve as a guide when counseling patients undergoing ASCT for relapsed MM and also serve as benchmark in designing clinical trials of transplant and comparative novel therapies for relapsed MM. Disclosures Muffly: Amgen: Consultancy; Adaptive: Research Funding; Servier: Research Funding. Shiraz:Kite, a Gilead Company: Research Funding; ORCA BioSystems: Research Funding. Liedtke:Adaptive: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Caelum: Membership on an entity's Board of Directors or advisory committees. Rezvani:Pharmacyclics: Research Funding. Meyer:Orca Bio: Research Funding. Shizuru:Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Negrin:Biosource: Current equity holder in private company; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; BioEclipse Therapeutics: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy; Amgen: Consultancy. Miklos:Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding. Sidana:Janssen: Consultancy.

Background: The prognostic and predictive utility of measurable residual disease (MRD) assessments using bone marrow (BM) aspirates is well-established in the management of acute lymphoblastic leukemia (ALL). However, frequent BM MRD monitoring post-therapy is limited by the invasive, expensive, and at times impractical nature of numerous BM examinations. Limited retrospective reports have suggested that MRD analysis by next-generation sequencing (NGS) using peripheral blood (PB) may provide a viable alternative to MRD monitoring of the BM. We conducted a prospective, multi-institutional observational study of NGS-based MRD of the PB among adult ALL patients undergoing cellular therapies (hematopoietic cell transplantation [HCT] and chimeric antigen receptor T cells [CART]) in order to determine the correlation between PB and BM MRD and to explore the clinical utility of monitoring MRD in the PB. Methods: Patients >= 18 years-old with ALL were recruited from Stanford University and Kaiser Permanente, Northern California. The MRD analyses were conducted using Adaptive Biotechnologies ClonoSEQ NGS based platform that tracks tumor specific VDJ rearrangement in B and T cell malignancies. Assessment of MRD was obtained from the PB and BM prior to HCT/CART. Among HCT patients, PB MRD was obtained at one month, and then every 2-3 months for the first year following HCT; a paired BM MRD sample was obtained at the 3 month time-point with optional additional BM examinations. Among CART patients, paired PB and BM MRD were obtained at one month, and then every 2-3 months for the first year following CART. The correlation between log10 values of PB and BM MRD samples was evaluated using the Pearson correlation coefficient. Clinical relapse was defined as morphologic leukemia blasts in the marrow or extramedullary site, or administration of a new therapy for rising MRD. Results: Sixty-nine patients scheduled to undergo cellular therapies were enrolled; 3 (4%) did not undergo planned therapy and were excluded and 4 (6%) lacked a detectable clonal leukemia sequence and were thus off study, resulting in a study population of 62 (42 BMT, 17 CART, 3 BMT and CART). The median age was 42 years (IQR 30-53), 36 (58%) were male, 54 (87%) had B-ALL,16 (26%) were BCR-ABL+, and 28 (46%) had extramedullary (EM) involvement. Across all patients, PB MRD was highly correlated with BM MRD (r=0.87; p Conclusion: This prospective observational study demonstrates a strong correlation between PB and BM NGS MRD results in ALL. These results show that non-invasive monitoring of PB-based MRD in ALL patients undergoing curative intent cellular therapies represents a viable alternative to serial BM examinations, providing clinically actionable information and the opportunity to intervene on impending clinical relapse. Disclosures Muffly: Adaptive: Research Funding; Amgen: Consultancy; Servier: Research Funding. Meyer:Orca Bio: Research Funding. Negrin:Amgen: Consultancy; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; BioEclipse Therapeutics: Current equity holder in private company; Biosource: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy. Rezvani:Pharmacyclics: Research Funding. Sidana:Janssen: Consultancy. Shiraz:ORCA BioSystems: Research Funding; Kite, a Gilead Company: Research Funding. Shizuru:Jasper Therapeutics, Inc: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Liedtke:Adaptive: Membership on an entity's Board of Directors or advisory committees; Caelum: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria. Miklos:Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding.

BACKGROUND: CD22 is expressed on the majority of B-cell malignancies. Autologous CAR T-cells targeting CD22 (CAR22) have yielded objective response rates (ORR) of 70-90% in pediatric patients with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (ALL), including those who had previously failed CD19-directed CAR T-cell (CAR19) therapy. Based on these encouraging results, we evaluated CAR22 in adult patients with R/R ALL and for the first time in patients with R/R large B-cell lymphoma (LBCL), including those who had failed prior autologous CAR19 therapy. METHODS: This single-institution phase I dose escalation clinical trial (NCT04088890) is evaluating a CAR construct incorporating the m971 CD22 single chain variable fragments and 41BB/CD3z endodomains integrated within autologous T-cells via lentiviral transduction. After lymphodepletion with fludarabine and cyclophosphamide, patients were infused with fresh or cryopreserved CAR T-cells after a 7- to 11-day closed manufacturing process utilizing the CliniMACS Prodigy device (Miltenyi). The current cohort includes patients treated at dose level 1 (DL1), which was 1x106 CAR+ cells/kg. Primary objectives assessed the ability to successfully manufacture CAR22 and safety. Overall response rate (ORR) at 28 days post-infusion (D28) was a secondary objective. RESULTS: Three patients with LBCL have been enrolled with a median age of 53 years (range, 51-57) and a median of 6 (range, 5-8) prior lines of therapy. All three patients received prior CAR19 and had refractory disease to second-line or later therapy (n=3); had not undergone autologous hematopoietic stem cell transplantation (HSCT) (n=3); had MYC and BCL2 gene rearrangements (double-hit lymphoma; n=2); had high tumor burden (SPD >50 cm2; n=2); had a history of primary refractory disease (n=1); or had never achieved CR to any therapy (n=1). Six patients with ALL have been enrolled with a median age of 43.5 years (range, 23-62) and a median of 6 (range, 4-8) prior lines of therapy. All six patients received prior allogeneic HSCT and had Ph-positive disease (n=3); had central nervous system (CNS) involvement (n=3); had extramedullary disease (n=2); had high disease burden (BM blasts >5%; n=2); had received prior CD19-directed therapy (n=5); or had received prior CD22-directed therapy (n=3). Successful manufacturing of cells at DL1 was achieved in all patients. All patients (LBCL n=3, ALL n=6) reached day 28 and are included in the safety and response analysis presented here; updated results will be presented at the meeting. Eight patients (88.9%) experienced cytokine release syndrome (CRS); all were Grade 1-2. There were no cases of immune effector cell-associated neurotoxicity syndrome (ICANS). No differences in toxicities were seen across the patient age spectrum and no Grade 5 toxicities occurred following CAR22 infusion. In LBCL, all patients achieved a response at D28 (ORR=100%; CR, n=1, PR, n=2). Both patients with a D28 PR improved to CR by day 90 and 180. All patients remain in CR, with a median follow-up of 8.4 months (range, 6-9.3). In ALL, all patients achieved a CR at D28 (ORR=100%; MRD-, n=5, MRD+, n=1). After a median follow up of 5.1 months (range, 1-8.2), three patients relapsed at 2.5, 4, and 5.5 months after infusion; one patient died while undergoing subsequent therapy 7.3 months post-infusion. CD22 expression by flow cytometry was downregulated or absent in two patients after relapse. Peak CAR expansion as detected by peripheral blood flow cytometry reached a median level of 90.1 (LBCL; range, 85.4-350) and 43.4 (ALL; range, 0.9-399.6) CAR+ cells/µL between D14 and D21. In two LBCL patients with progression following CAR19, CAR22 levels were 11.7 and 55.9 fold higher than prior CAR19 levels at peak expansion. CONCLUSIONS: Infusion of CD22-targeting CAR T-cells in R/R LBCL and ALL is safe and well tolerated. Manufacturing of CAR22 was uniformly successful. To date, 3 of 3 heavily treated adult patients with LBCL whose disease relapsed after prior CAR19 have each achieved CR durable to at least 6 months. All adult ALL patients have achieved CR following CAR22, with some early relapses observed. Accrual is ongoing. Disclosures Negrin: Amgen: Consultancy; Biosource: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; BioEclipse Therapeutics: Current equity holder in private company. Rezvani:Pharmacyclics: Research Funding. Shiraz:ORCA BioSystems: Research Funding; Kite, a Gilead Company: Research Funding. Sidana:Janssen: Consultancy. Mackall:BMS: Consultancy; Allogene: Current equity holder in publicly-traded company; Apricity Health: Consultancy, Current equity holder in private company; Nektar Therapeutics: Consultancy; NeoImmune Tech: Consultancy; Lyell Immunopharma: Consultancy, Current equity holder in private company. Miklos:Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding. Muffly:Amgen: Consultancy; Adaptive: Research Funding; Servier: Research Funding. OffLabel Disclosure: CD22-directed CAR T-cell Therapy for the treatment of adults with relapsed/refractory LBCL and B-ALL

Background Cytokine-induced killer (CIK) cells are an ex vivo–expanded cellular therapy product with potent anti-tumor activity in a subset of patients with solid and hematologic malignancies. We hypothesize that directing CIK cells to a specific tumor antigen will enhance CIK cell anti-tumor cytotoxicity. Methods We present a newly developed method for affixing antibodies directly to cell surface proteins. First, we evaluated the anti-tumor potential of CIK cells after affixing tumor-antigen targeting monoclonal antibodies. Second, we evaluated whether this antibody-conjugation method can profile the surface proteome of CIK cells. Results We demonstrated that affixing rituximab or daratumumab to CIK cells enhances cytotoxic killing of multiple lymphoma cell lines in vitro. These ‘armed’ CIK cells exhibited enhanced intracellular signaling after engaging tumor targets. Cell surface proteome profiling suggested mechanisms by which antibody-armed CIK cells concurrently activated multiple surface proteins, leading to enhanced cytolytic activity. Our surface proteome analysis indicated that CIK cells display enhanced protein signatures indicative of immune responses, cellular activation and leukocyte migration. Conclusions Here, we characterize the cell surface proteome of CIK cells using a novel methodology that can be rapidly applied to other cell types. Our study also demonstrates that without genetic modification CIK cells can be rapidly armed with monoclonal antibodies, which endows them with high specificity to kill tumor targets.

BACKGROUND: Autologous hematopoietic stem cell transplantation (ASCT) is a standard treatment for multiple myeloma (MM). Consensus guidelines recommend collecting sufficient stem cells in case there is need for stem cell boost for delayed/poor engraftment or for future second ASCT. However, collecting and storing backup stem cells in all patients requires significant resources and cost, and the rates of backup stem cell utilization are not well studied. OBJECTIVE: To examine the utilization of backup stem cells (BSCs) in patients with MM undergoing ASCT. STUDY DESIGN: Patients with MM aged ≥18 years old who underwent first ASCT at our institution from January 2010 through December 2015 and collected sufficient stem cells for at least two transplants were included in this single-center retrospective study. This timeframe was selected to allow for adequate follow-up. RESULTS: A total of 393 patients were included. The median age was 58 years (range 25–73). After a median follow-up of 6 years, the median PFS of the cohort was 3 years. 61% (n = 240) of patients progressed or relapsed. Chemotherapy based mobilization was used in almost all patients (98%). The median total CD34+ cells collected was 18.2 × 10(6)/kg (range 3.4–112.4). A median of 5.7 × 10(6) CD34+ cells/kg (range 1.8–41.9) were infused during the first ASCT and a median of 10.1 × 10(6) CD34+ cells/kg (range 1.5–104.5) were cryopreserved for future use. 6.9% (n = 27) of patients utilized backup stem cells, with 2.3% (n = 10) using them for stem cell boost, 4.6% (n = 18) for a second salvage ASCT, including 1 patient for both stem cell boost and second ASCT. Rates of backup stem cell use amongst patients aged

Introduction: Local treatment with intratumoral CpG (a toll-like receptor 9 agonist, SD-101) and low-dose radiation can elicit antitumor immune responses and global tumor reduction in patients with low-grade lymphoma (Frank, Cancer Discov, 2018). Ibrutinib compromises B-cell survival by inhibiting Bruton's tyrosine kinase, but also modulates T-cells by inhibiting interleukin-2-inducible T-cell kinase. In a mouse model of lymphoma, ibrutinib plus intratumoral CpG was curative of systemic disease, an effect that was T-cell dependent (Sagiv-Barfi, Blood, 2015). Thus, we initiated a phase I/II clinical trial combining oral ibrutinib, intratumoral CpG and local low-dose radiation in adults with recurrent low-grade lymphoma (NCT02927964). Methods: Enrolled patients received intratumoral injections of CpG (SD-101, 3mg) weekly for 5 doses, starting on the second day of a 2-day course of local radiation (4Gy total) to the same site. Daily oral ibrutinib (560mg) began on day 9. Treatment-emergent adverse events (AEs), ibrutinib dose modifications and adherence were recorded at every visit. Revised Lugano criteria (Cheson et al., JCO, 2014) were used to assess response to therapy, based on CT scans at 3, 6, 12, 18, and 24 months. Fine needle aspirates (FNAs) were obtained from CpG-injected and non-injected nodal tumor sites pre- and post-treatment and analyzed by flow cytometry and single-cell RNA sequencing (scRNAseq). When available, viably preserved tumor and peripheral blood cells were used for in vitro immune response assays. Results: As of July 16, 2020, 18 patients had been treated, with a median follow-up of 12 months. Ten were male and 8 were female. All but one had a diagnosis of follicular lymphoma; one patient had marginal zone lymphoma. All were previously treated with an average of 2 prior lines of therapy. AEs were consistent with known effects of ibrutinib (including diarrhea and rash) and of CpG (including fever and flu-like reaction) with no unexpected AEs to suggest synergistic toxicity. There were no grade 4 or 5 events. AEs led to ibrutinib dose reduction or discontinuation in 2 patients and dose interruption in 6 patients. At the time of analysis, 9 of 18 evaluable patients had achieved a partial response (50% ORR) and 12 of 18 patients experienced at least a 30% reduction in the distant uninjected lesions (Figure 1A). Most responses have been maintained for at least 6 months, many longer (Figure 1B). Flow cytometry revealed decreased T follicular helper cells and increased CD4 and/or CD8 effector T-cells, CD137+ activated T-cells, and NK cells in CpG-injected tumors. Abscopal immune effects in distant non-injected lesions included an increase in Granzyme B+ CD8 T-cells, most prominent after the addition of ibrutinib. scRNAseq data showed significant transcriptional shifts in tumor cells and in tumor-infiltrating T-cells, including signatures of interferon response and T cell activation and cytotoxicity. Finally, in vitro assays showed tumor-specific immune responses in peripheral blood T-cells of all 6 evaluable patients tested thus far. Conclusion: Early data suggest that the combination of oral ibrutinib, intratumoral CpG, and local low-dose radiation is safe and can generate systemic antitumor immune responses and systemic tumor shrinkage in low-grade lymphoma. Disclosures Khodadoust: Seattle Genetics: Consultancy; Kyowa Kirin: Consultancy. Levy:Quadriga: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; GigaGen: Membership on an entity's Board of Directors or advisory committees; Teneobio: Membership on an entity's Board of Directors or advisory committees; Sutro: Membership on an entity's Board of Directors or advisory committees; Checkmate: Membership on an entity's Board of Directors or advisory committees; Nurix: Membership on an entity's Board of Directors or advisory committees; Dragonfly: Membership on an entity's Board of Directors or advisory committees; Abpro: Membership on an entity's Board of Directors or advisory committees; Apexigen: Membership on an entity's Board of Directors or advisory committees; Spotlight: Membership on an entity's Board of Directors or advisory committees; 47 Inc.: Membership on an entity's Board of Directors or advisory committees; XCella: Membership on an entity's Board of Directors or advisory committees; Immunocore: Membership on an entity's Board of Directors or advisory committees; Walking Fish: Membership on an entity's Board of Directors or advisory committees; Viracta: Membership on an entity's Board of Directors or advisory committees.

Introduction: Chimeric antigen receptor (CAR) T cells targeting either CD19 or CD22 have yielded striking complete remission (CR) rates of 70%-90% in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL), but CD19 negative and CD22 low relapse limits the curative potential of these single-antigen CAR T cell approaches. We hypothesized that a bivalent CAR-T construct that can target CD19 and/or CD22 would prevent antigen negative/low relapse. Here we present the combined single institution experience to date of pediatric and adult patients with R/R ALL treated with this novel bispecific CAR. Methods: We conducted parallel Phase I clinical trials of CD19/CD22 bispecific CAR T cells in pediatric and adult patients with relapsed/refractory ALL. We utilized lentiviral transduction of a bivalent CAR construct incorporating the fmc63 CD19 and m971 CD22 single chain variable fragments (scFvs) and a 41BB costimulatory endodomain. After lymphodepletion with fludarabine and cyclophosphamide, patients were infused with fresh or cryopreserved CAR T cells manufactured using a 7-11 day process. Two dose levels were tested during dose escalation: Dose level 1 was 1x106 CAR T cells/kg and dose level 2 was 3x106 cells/kg. Primary objectives assessed the ability to successfully manufacture CAR19/22 CAR T cells and safety while response at Day 28 post-infusion was a secondary objective. Blood, bone marrow and cerebrospinal fluid samples were obtained at protocol defined intervals for correlative biology studies. Results: Nineteen patients have been enrolled (10 pediatric; 9 adult) with a median age of 23 years (range, 2-68) and median of 4 (range, 2-11) prior lines of leukemia-directed therapy. Ten patients received prior HCT, 9 were treated with prior Blinatumomab, 3 with prior CD19 directed CAR T cells and 4 with prior Inotuzumab. Fourteen patients (8 pediatric, 6 adult) have been infused to date with CD19/CD22 bispecific CAR T cells; 7 were treated at dose level 1 (DL1) and 7 at dose level 2 (DL2). Successful manufacturing of cells at target dose levels was achieved in all patients. Twelve patients have reached day 28 and are included in the safety and response analysis presented here. Nine of 12 (75%) experienced cytokine release syndrome (CRS) and 2/12 (17%) developed immune-effector cell neurotoxicity syndrome (ICANS). The CRS and ICANS were all grade 1 or 2 across both dose levels and across pediatric and adult patients except for one adult with high disease burden who experienced grade 4 CRS and grade 4 ICANS, both of which were reversible. No differences in toxicities were seen across the patient age spectrum and there were no cases of treatment-related mortality within 28 days following CAR T infusion. Eleven of 12 (92%) patients achieved a CR, 10 of whom achieved CR at day 28 and one with a PR of extramedullary disease at day 28 which improved to CR by day 180 without further leukemia-directed intervention. One patient had primary progressive disease prior to day 28. Peak CAR expansion as detected by peripheral blood flow cytometry reached a median level of 11.13% (DL1) and 29.1% (DL2) CAR T of CD3+ cells with a range of 0.7-22.54% and 3.8-86.96%, respectively. To date, 3 patients (1 pediatric and 2 adult patients) have relapsed, all with retention of CD19. Post-remission practice differed across pediatric and adult patients; Six pediatric patients reaching day 28 underwent consolidative hematopoietic cell transplantation (HCT) whereas no adult patients received subsequent HCT. One patient died from complications post HCT while in remission. Therefore, the overall survival for all infused patients was 92% with a median follow-up of 9.5 months from time of infusion (range, 1-20). Conclusion: The combined pediatric and adult phase I trials of bispecific CD19/CD22 targeting CAR T cells in relapsed/refractory ALL demonstrates safety and tolerability at two dose levels. Expanded accrual at dose level 2 is ongoing and clinical outcomes will be updated. This work additionally demonstrates feasibility of delivering unified B-ALL CAR T cell therapy across age boundaries. Multi-parametric CyTOF studies permitting CAR T cell phenotyping in conjunction with single cell TCR tracking, proteomics, epigenomics and cytokine profiling are ongoing and will be used to further characterize persisting CAR T cells and define inter-product and inter-patient variability. Disclosures Muffly: Pfizer: Consultancy; KITE: Consultancy; Adaptive: Research Funding. Majzner:Xyphos Inc.: Consultancy; Lyell Immunopharma: Consultancy. Feldman:Octane Biotech, Inc.: Employment; Personalized Medicine Initiative Science: Membership on an entity's Board of Directors or advisory committees. Miklos:Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Becton Dickinson: Research Funding; Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees; AlloGene: Membership on an entity's Board of Directors or advisory committees. Mackall:Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Background: Anti-CD19 chimeric antigen receptor (CAR19) T-cells have significant activity in patients with relapsed/refractory DLBCL (rrDLBCL). While the majority of rrDLBCL patients receiving axicabtagene ciloleucel (Axi-cel)achieve complete responses, a significant subset of patients experience disease progression (Locke FL, et al. Lancet Oncol. 2019). Circulating tumor DNA (ctDNA) analysis has demonstrated utility for predicting therapeutic benefit in DLBCL, as well as for detecting emergent resistance mechanisms to targeted therapies. Here we apply cell-free DNA (cfDNA) analysis to patients receiving Axi-cel, to characterize molecular responses, resistance mechanisms, and to track CAR19 cells. Methods: We performed Cancer Personalized Profiling by Deep Sequencing (CAPP-Seq) on DNA from germline and plasma samples collected prior to CAR T-cell infusion, multiple time-points post infusion, and, where available, at the time of relapse from 30 patients receiving Axi-cel for rrDLBCL at Stanford University. We designed a novel hybrid-capture panel and analysis pipeline designed to detect both tumor variants, as well as Axi-cel specific recombinant retroviral sequences to quantify CAR19 levels in cfDNA. Tumor variants were identified prior to and following Axi-cel therapy to assess for emergent variants, and Axi-cel specific sequences were quantified. Results: The median follow-up for the 30 patients after Axi-cel infusion was 10 months, with 47% (14/30) of patients experiencing disease progression after Axi-cel therapy. We identified an average of 164.3 SNVs per case (range:1-685) before Axi-cel therapy; the most common coding variants identified at baseline were in MLL2 (29.2%), BCL2 (22.5%), and TP53 (19.3%). When treated as a continuous variable, pretreatment ctDNA levels were prognostic of PFS (HR 2.16, 95% CI 1.11-4.21, P=0.02). Using a previously established ctDNA threshold to stratify disease burden (2.5 log10(hGE/mL); Kurtz et al. JCO 2018), we observed significantly superior PFS in patients with low pretreatment ctDNA levels treated with Axi-cel (Fig. 1A). In the majority of Axi-cel treated patients (62.9%), ctDNA was detectable at day 28, and PFS was significantly longer in patients with undetectable ctDNA at this time-point (Fig. 1B). Multiple putative resistance mechanisms were identified at relapse after Axi-cel, including emergent variants in CD19, HVEM, and TP53, as well as copy number gains in PD-L1 (Fig. 1C). For example, in one patient, a CD19 stop-gain mutation, which was not detected prior to treatment or at the time of the first interim PET scan, emerged at the time of relapse (Fig. 1D). Finally, we found cfDNA evidence for Axi-cel DNA in 74% of patients 28 days after therapy, including in patients without evidence of circulating CAR T-cells in PBMCs. Axi-cel levels in cfDNA as measured by CAPP-Seq were significantly correlated with CAR19 flow cytometry (Pearson r=0.55, P=.015; Fig. 1E). Conclusions: Baseline and interim ctDNA measurements have prognostic significance in DLBCL patients being treated with CAR19 T-cells, and potential emergent resistance mutations, including in CD19, can be identified in patients via cfDNA analysis. Quantification of CAR19 T-cells using cfDNA is significantly correlated with flow cytometric quantification, indicating that these cells can be quantified via cfDNA. Taken together, these data indicate that cfDNA analysis is a powerful tool for predicting response to CAR19 therapy, identifying genomic determinants of resistance and quantifying CAR19 cells, which may in turn inform the next therapeutic steps. Figure 1: A) Kaplan Meier analysis of PFS, with patients stratified based on pre-Axi-cel therapy ctDNA level, above and below a previously established threshold (2.5 log10[haploid Genome Equivalents/mL]). B) A Kaplan Meier plot depicting PFS stratification for patients with detectable versus undetectable ctDNA at day 28 after Axi-cel infusion. C) Oncoprint depicting selected emergent and baseline tumor variants in progressors and non-progressors after Axi-cel therapy. D) Change in mean ctDNA variant allele frequency (VAF) and emergence of a CD19 stop-gain mutation (CD19 pTrpX) at the time of relapse in a patient who initially achieved a CR at day 28 after CAR19 infusion. E) Relationship between CAR19 T-cell quantification by cfDNA and flow cytometry. (ND: Not detected) Disclosures Kurtz: Roche: Consultancy. Chabon:Lexent Bio Inc: Consultancy. Khodadoust:Corvus Pharmaceuticals: Research Funding. Majzner:Xyphos Inc.: Consultancy; Lyell Immunopharma: Consultancy. Mackall:Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Diehn:Roche: Consultancy; Quanticell: Consultancy; Novartis: Consultancy; AstraZeneca: Consultancy; BioNTech: Consultancy. Miklos:Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Becton Dickinson: Research Funding; AlloGene: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees. Alizadeh:Genentech: Consultancy; Janssen: Consultancy; Pharmacyclics: Consultancy; Gilead: Consultancy; Celgene: Consultancy; Chugai: Consultancy; Roche: Consultancy; Pfizer: Research Funding.