Vos, Sven de

PURPOSE Off-the-shelf, allogeneic CD19 chimeric antigen receptor (CAR) T-cell products may improve access to treatment versus autologous ones. We report the phase I experience of the allogeneic CD19 CAR T-cell product cemacabtagene ansegedleucel (cema-cel) and its predecessor, ALLO-501, in CD19 CAR T-naïve patients with relapsed/refractory large B-cell lymphoma (R/R LBCL). METHODS In the ALPHA2/ALPHA studies, the safety and efficacy of allogeneic CD19 CAR T cells were evaluated in CD19 CAR T treatment-naïve patients with R/R LBCL. Patients received healthy donor-derived, human leukocyte antigen–unmatched cema-cel/ALLO-501 following a 3-day lymphodepletion regimen of fludarabine (30 mg/m 2 once daily), cyclophosphamide (300 or 500 mg/m 2 once daily), and escalating doses of the anti-CD52 monoclonal antibody, ALLO-647. RESULTS As of September 26, 2024, 33 CD19 CAR T-naïve patients with LBCL (median age, 66 years; median number of previous therapies, 3) received allogeneic CAR T cells. CAR T-cell expansion was observed following infusion, with persistence observed up to 4 months. The overall and complete response (CR) rates were 58% and 42%, respectively; the median duration of response in patients with a CR was 23.1 months. The most common treatment-emergent adverse events were hematologic toxicities. No cases of graft-versus-host disease, immune effector cell–associated neurotoxicity syndrome, or grade ≥3 cytokine release syndrome were reported. CONCLUSION Allogeneic CD19 CAR T cells demonstrated promising overall and durable CR rates with a manageable safety profile in CD19 CAR T-naïve patients with R/R LBCL, supporting additional evaluation of cema-cel in patients with LBCL.

ZUMA-12 is a multicenter phase 2 study evaluating axicabtagene ciloleucel (axi-cel) autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy as part of first-line treatment for high-risk large B-cell lymphoma (LBCL). In the primary efficacy analysis (n = 37; median follow-up, 15.9 months), axi-cel demonstrated a high rate of complete responses (CR; 78%) and a safety profile consistent with prior experience. Here, we assessed updated outcomes from ZUMA-12 in 40 treated patients after ≥3 years of follow-up. Eligible adults underwent leukapheresis, lymphodepleting chemotherapy, and axi-cel infusion (2 × 106 CAR T cells/kg). Investigator-assessed CR, objective response, survival, safety, and CAR T-cell expansion were assessed. The CR rate among response-evaluable patients (n = 37) increased after the primary analysis to 86% (95% confidence interval [CI], 71%-95%), with a 92% objective response rate. After a median follow-up of 47.0 months (range, 37.1-57.8 months), 36-month estimates (95% CI) of duration of response and event-free, progression-free, and overall survival were 81.8% (63.9%-91.4%), 73.0% (55.6%-84.4%), 75.1% (57.5%-86.2%), and 81.1% (64.4%-90.5%), respectively. In total, 4 patients had new malignancies, 2 occurring after the data cutoff of the primary analysis; none were axi-cel–related. Eight patients died on study, 2 of whom died from nonrelapse mortality causes. After long-term follow-up, axi-cel demonstrated a high durable response rate, with no new safety signals after the primary analysis, suggestive of an effective first-line therapy with curative intent in high-risk LBCL. Further assessments are needed to determine its benefit vs standard of care. This trial was registered at clinicaltrials.gov, as NCT03761056.

Background: While breakthroughs in hematologic malignancies with autologous CAR T-cell therapies have been met with growing clinical interest due to impressive outcomes, limitations in logistics/manufacturing, quality consistency, and product availability persist. Allogeneic CAR T-cell therapies may circumvent such challenges by providing an off-the-shelf therapeutic option derived from healthy donors. For allogeneic CAR T cells to be successful, there must be a safe and effective way to control host lymphocyte rejection of allogeneic CAR T cells (allo-rejection). ALLO-501 and ALLO-501A are allogeneic anti-CD19 CAR T-cell products that use Cellectis technologies' TALEN® gene editing to disrupt both the TCRα constant ( TRAC) and CD52 genes. CD52 disruption specifically permits use of ALLO-647, an anti-CD52 antibody, for the transient and selective depletion of host lymphocytes that enables ALLO-501 and ALLO-501A to proliferate after infusion without rapid allo-rejection. Updated phase 1 data for ALLO-501 (ALPHA; NCT03939026) and ALLO-501A (ALPHA2; NCT04416984) showed that administration of anti-CD19 allogeneic CAR T product following use of lymphodepletion that includes ALLO-647 plus fludarabine and cyclophosphamide provided durable responses and an acceptable safety profile in CAR T-cell-naive pts with r/r large B-cell lymphoma (LBCL; Locke FL, et al. ASCO 2023; #2517). Herein, we provide safety results of ALLO-647 in pts with r/r LBCL and follicular lymphoma (FL). Methods: Pts with r/r LBCL and FL enrolled in ALPHA and ALPHA2 studies received a 3 to 5-day lymphodepletion regimen consisting of fludarabine 30 mg/m 2 and cyclophosphamide 300-500 mg/m 2 (FC) and 39, 60, or 90 mg of ALLO-647 in divided doses. ALLO-501/ALLO-501A were administered after the completion of lymphodepletion. Incidence rates of grade ≥3 cytopenias (neutropenia, thrombocytopenia, anemia and pancytopenia) were assessed at 3 timepoints (Study Day 28, Day 56, and Month 4). Pts underwent weekly cytomegalovirus (CMV) monitoring. Leukocyte reconstitution was evaluated following lymphodepletion and CAR T-cell infusion. Results: As of April 20, 2023, 87 pts with r/r LBCL (n=61) and FL (n=26) were treated with ALLO-647 and included in the analysis (median age, 64 years; median number of prior regimens, 3). In total, 11 (13%), 39 (45%), and 37 (43%) pts received 39, 60, and 90 mg ALLO-647, respectively. Among the LBCL pts, 33 were CAR T-cell-naive and treated with product manufactured using the Phase 2 process. Median follow-up was 29.5 months (range, 6.8-47.5). The most common treatment-emergent adverse events (TEAEs), assessed from the time of first dose of lymphodepletion, included neutropenia (79%), anemia (61%), infusion-related reactions (IRRs, 55%), and thrombocytopenia (53%). The most common grade ≥3 TEAEs included neutropenia (74%), anemia (38%), and thrombocytopenia (38%). The proportion of pts experiencing grade ≥3 cytopenias decreased over time from Day 28 (29%) to Day 56 (20%) to Month 4 (15%), which was consistent across all lymphoma pt subgroups. ALLO-647 IRRs were typically low grade, except for 5 (6%) grade 3 events; all IRRs were managed with supportive care measures. After treatment with ALLO-501/501A, 20 pts (23%) experienced cytokine release syndrome events, which were low grade except for 1 (1%) grade 3 event. No GvHD, grade ≥3 immune effector cell-associated neurotoxicity syndrome events, or progressive multifocal leukoencephalopathy were reported. Any grade and grade ≥3 infections were reported in 50 pts (58%) and 18 pts (21%), respectively. Two pts had (2%) fatal infectious events (COVID-19 pneumonia and pneumonia, n=1 each) as previously reported. The most common infection was CMV reactivation (any grade, n=22 [25%]; grade 3, n=8 [9%]). Following lymphodepletion, the median time to absolute neutrophil count and absolute lymphocyte count recovery to grade <4 was 7 days and 28 days, respectively. T-cell counts exhibited a steady increase over time, with the majority of pts achieving full T-cell recovery (return to baseline levels) by Month 6. Detailed pharmacokinetics and pharmacodynamics data will be presented. Conclusions: These data suggest allogeneic CAR T-cell products administered following lymphodepletion consisting of FC and ALLO-647 can provide a safe and tolerable alternative to autologous CAR T-cell therapy.

Background: Axi-cel is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for the treatment of relapsed/refractory (R/R) LBCL. ZUMA-12 (NCT03761056) is a Phase 2, multicenter, single-arm study of axi-cel as part of first-line treatment in patients with high-risk LBCL. In the primary efficacy analysis (n=37; median follow-up of 15.9 months), axi-cel demonstrated a high rate of investigator-assessed complete response (CR; 78%; 95% CI, 62-90) and an 89% objective response rate (ORR; 95% CI, 75-97). Axi-cel also had a manageable safety profile, with no new safety signals observed in the first-line setting (Neelapu et al. Nat Med. 2022). Here, we report updated efficacy and safety outcomes from ZUMA-12 in all patients treated with axi-cel after a median follow-up of ≥40 months. Methods: Eligible adults had high-risk LBCL, with MYC and BCL2 and/or BCL6 rearrangements (double- or triple-hit histology) per investigator or an International Prognostic Index (IPI) score ≥3, plus a positive interim PET per Lugano classification (Deauville score 4/5) after 2 cycles of an anti-CD20 monoclonal antibody and anthracycline-containing regimen. Patients underwent leukapheresis, followed by lymphodepleting chemotherapy (cyclophosphamide and fludarabine) on Days -5, -4, and -3, and a single axi-cel infusion of 2×10 6 CAR T cells/kg on Day 0. Per investigator discretion, non-chemotherapy bridging could be administered. The primary endpoint was investigator-assessed CR rate per Lugano classification (Cheson et al. J Clin Oncol. 2014). Secondary endpoints included ORR, duration of response (DOR), event-free survival (EFS), progression-free survival (PFS), overall survival (OS), safety, and levels of CAR T cells in blood and cytokines in serum. Results: As of May 3, 2023, 42 patients were enrolled and 40 were treated with axi-cel, with a median follow-up of 40.9 months (range, 29.5-50.2). In total, 37 patients were evaluable for response (centrally confirmed double- or triple-hit histology or IPI score ≥3). The CR rate was 86% (95% CI, 71-95), and 92% (95% CI, 78-98) of patients had an objective response. Patients with centrally confirmed double- or triple-hit histology (n=10) had a CR rate of 90%. Responses were ongoing in 73% of response-evaluable patients at data cutoff. Medians for DOR, EFS, PFS, and OS were not reached. The 36-month estimates for DOR, EFS (Figure 1), PFS, and OS (Figure 2) were 82%, 73%, 75%, and 81%, respectively. All treated patients (n=40) experienced adverse events (AEs) of any grade and 88% of patients had grade ≥3 AEs. Similar to the primary analysis, the most common any-grade AEs were pyrexia (100%), headache (70%), and neutrophil count decreased (55%). No new cases of cytokine release syndrome (CRS) or neurologic events of any grade occurred since the prior data cut and all cases of CRS and neurologic events reported were resolved by data cutoff. Prolonged cytopenias of any grade (present Day ≥30 post-infusion) occurred in 9 patients (n=7 neutrophil count decreased) and were resolved by data cutoff. There were 8 deaths due to progressive disease (n=5) and other causes not related to axi-cel (1 COVID-19, 1 esophageal adenocarcinoma, 1 septic shock on Days 350, 535, and 287 post axi-cel infusion, respectively). Two of the 8 deaths (1 progressive disease and 1 esophageal adenocarcinoma) occurred after the primary analysis. Among treated patients, post-infusion CAR T-cell expansion by peak and area under the curve was 36.9 cells/µL and 368.0 cells/µL×days, respectively, in those with ongoing responses at data cutoff (n=17), 45.1 cells/µL and 413.4 cells/µL×days in those who relapsed (n=6), and 34.7 cells/µL and 566.8 cells/µL×days in non-responders (n=3). Conclusion: In this updated analysis of ZUMA-12 with a median follow-up of ≥40 months, axi-cel demonstrated a high rate of durable responses and no new safety signals. Axi-cel may benefit patients exposed to fewer prior therapies and those with high-risk LBCL, a population with high unmet need and poor outcomes after standard first-line chemoimmunotherapy.

2517 Background: Approximately 50% to 60% of pts with r/r LBCL will either not achieve a complete response (CR) or will relapse with current treatments and require additional therapy. Autologous anti-CD19 chimeric antigen receptor T (CAR T) therapies have revolutionized the care of patients whose disease progresses following standard therapies, but patient-specific manufacturing processes and long wait times to treatment present challenges for their broad clinical use. Allogeneic (healthy-donor-derived), off-the-shelf, anti-CD19 (CAR T) treatment promises broader and more rapid access to one-dose treatment with curative intent. Initial phase 1 data for the anti-CD19 AlloCAR T cell product ALLO-501 (NCT03939026) and successor, ALLO-501A (NCT04416984), demonstrated a manageable safety profile with no dose-limiting toxicities (DLTs), and efficacy comparable to autologous CAR T therapy in pts with r/r LBCL who were autologous CAR T-naïve. This update provides additional follow up and a focus on participants who received the conditioning regimen and cells made with an optimized manufacturing process currently under study in the first potentially pivotal trial for an allogeneic CAR T product. Methods: In these two multicenter, single-arm, open-label, phase 1 trials, a cohort of autologous CAR T-naïve pts with r/r LBCL underwent 3-day lymphodepletion (LD) with FCA90, fludarabine (F, 30 mg/m2/day), cyclophosphamide (C, 300 mg/m2/day), and ALLO-647 (A [anti-CD 52 mAb] 30 mg/day; total dose: 90 mg) followed by a single dose of ALLO-501 or ALLO-501A produced by the Alloy manufacturing process. Results: As of Jan 26, 2023, 12 pts received the FCA90 LD regimen and CAR T therapy with 100% receiving product per specifications with a median time from enrollment to LD of 3 days. Median follow-up time (actual) was 7.1 months (range: 1.4, 36.0). No DLTs, severe (Gr3+) cytokine-release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), or graft-versus-host disease (GvHD) events occurred. An overall response rate and a CR rate of 66.7% and 58.3%, respectively, were observed. Median DOR was 23.1 months. Among 8 pts with the opportunity to be followed for 6 months, 5 (62.5%) had achieved CR and 4 (50.0%) sustained CR through 6 months. Analyses of vector copy number pharmacokinetics at Days 28 and 56 documented substantial and sustained expansion of CAR T cells. Conclusions: A one-time dose of allogeneic CAR T therapy following LD with FCA90 provided durable responses with a manageable safety profile in patients with r/r/ LBCL comparable to those treated with autologous CAR T cells. This treatment enables rapid access to off-the-shelf treatment with a median time from trial enrollment to treatment of 3 days. These findings support broader evaluation of ALLO-501A in the ongoing, first potentially pivotal phase 2 trial (ALPHA2) of off-the-shelf allogeneic CAR T cells. Clinical trial information: NCT03939026 .

Abstract Modulation of expression of the c-kit proto-oncogene product, the receptor for the recently identified stem cell factor, was studied on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated cultures of CD34+ normal bone marrow progenitor cells, blast cells from patients with primary acute myelogenous leukemia, cells from the leukemia cell lines HEL and MO7E, as well as cultured HMC-1 mast cells. Expression of c-kit was assessed on both RNA and protein level employing standard Northern blotting, reverse transcription, and polymerase chain reaction-based Southern blotting, as well as cell surface labeling with anti-c-kit mAb YB5.B8. Treatment of virtually all cell types with nontoxic concentrations of TPA (10(-9) M) for at least 48 h was associated with down-regulation of synthesis of c-kit transcripts and stem cell factor-receptor surface expression. Studies on the mechanism of action of TPA utilizing the HEL erythroleukemia line showed that TPA was primarily acting by accelerating the turnover of c-kit RNA most likely through induction of a destabilizing protein. The effect of TPA on c-kit expression levels was independent of TPA-mediated induction of differentiation since other compounds including IFN-gamma, vitamin D3, retinoic acid, arabinofuranosylcytosine, butyric acid, and camptothecin, which also effectively induced differentiation of HEL cells, failed to alter levels of c-kit expression.

Abstract Background: High-risk LBCL is associated with poor prognosis after first-line anti-CD20 mAb-containing regimens, highlighting the need for novel treatments. Axi-cel, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, is approved for treatment of relapsed/refractory (R/R) LBCL after ≥2 lines of systemic therapy. Here we report the primary analysis of ZUMA-12, a Phase 2, multicenter, single-arm study of axi-cel as part of first-line therapy in patients with high-risk LBCL. Methods: Eligible adults had high-risk LBCL, defined by histology (double- or triple-hit status [MYC and BCL2 and/or BCL6 translocations] per investigator) or an IPI score ≥3, plus a positive interim PET per Lugano Classification (Deauville score [DS] 4/5) after 2 cycles of an anti-CD20 mAb and anthracycline-containing regimen. Patients underwent leukapheresis and received conditioning chemotherapy (cyclophosphamide and fludarabine) followed by a single axi-cel infusion at 2×10 6 CAR T cells/kg. Non-chemotherapy bridging could be administered before conditioning per investigator discretion. The primary endpoint was investigator-assessed complete response (CR) rate per Lugano. Secondary endpoints included objective response rate (ORR; CR + partial response), duration of response (DOR), event-free survival (EFS), progression-free survival (PFS), overall survival (OS), incidence of adverse events (AEs), and levels of CAR T cells in blood and cytokines in serum. The primary analysis occurred after all treated patients had ≥6 months of follow-up. Results: As of May 17, 2021, 42 patients were enrolled and 40 were treated with axi-cel. Median age was 61 years (range, 23-86); 68% of patients were male, 63% had ECOG 1, 95% had stage III/IV disease, 48% had DS4, 53% had DS5, 25% had double- or triple-hit status per central assessment, and 78% had IPI score ≥3. A total of 37 patients had centrally confirmed double- or triple-hit histology or an IPI score ≥3 and were evaluable for response, with 15.9 months of median follow-up (range, 6.0-26.7). The CR rate was 78% (n=29; 95% CI, 62-90); 89% of patients had an objective response, and median time to initial response was 1 month. Among all 40 treated patients, 90% had an objective response (80% CR rate). At data cutoff, 73% of response-evaluable patients had ongoing responses. Medians for DOR, EFS, and PFS were not reached; 12-month estimates were 81%, 73%, and 75%, respectively. The estimated OS at 12 months was 91%. All 40 treated patients had AEs of any grade; 85% of patients had Grade ≥3 AEs, most commonly cytopenias (68%). Grade ≥3 cytokine release syndrome (CRS) and neurologic events (NEs) occurred in 3 patients (8%) and 9 patients (23%), respectively. Median times to onset of CRS and NEs were 4 days (range, 1-10) and 9 days (range, 2-44), with median durations of 6 days and 7 days, respectively. All CRS and most NEs (28/29) of any grade resolved by data cutoff (1 ongoing Grade 1 tremor); 39/40 CRS events resolved by 14 days post-infusion and 19/29 NEs resolved by 21 days post-infusion. Tocilizumab was administered to 63% and 3% of patients for management of CRS or NEs, respectively; corticosteroids were administered to 35% and 33% of patients for CRS and NE management. One Grade 5 event of COVID-19 occurred (Day 350). Median peak CAR T-cell level in all treated patients was 36 cells/µL (range, 7-560), and median expansion by AUC 0-28 was 495 cells/µL × days (range, 74-4288). CAR T-cell levels peaked at a median of 8 days post-infusion (range, 8-37). Higher frequency of CCR7+CD45RA+ T cells in axi-cel product, previously associated with greater expansion of CAR T cells (Locke et al. Blood Adv. 2020), was observed in ZUMA-12, compared with the ZUMA-1 study in R/R LBCL (Neelapu et al. New Engl J Med. 2017). Conclusion: In the primary analysis of ZUMA-12, axi-cel demonstrated a high rate of rapid and complete responses in patients with high-risk LBCL, a population with high unmet need. With 15.9 months of median follow-up, responses were durable as medians for DOR, EFS, and PFS were not yet reached and over 70% of patients remained in response at data cutoff. No new safety signals were reported with axi-cel in an earlier line. Overall, axi-cel may benefit patients exposed to fewer prior therapies, and further trials in first-line high-risk LBCL are warranted to assess axi-cel in this setting. Figure 1 Figure 1. Disclosures Neelapu: 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; 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. Dickinson: Janssen: Consultancy, Honoraria; Takeda: Research Funding; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria; Celgene: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria; MSD: Consultancy, Honoraria, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria, Other: travel, accommodation, expenses, Research Funding, Speakers Bureau; Gilead Sciences: Consultancy, Honoraria, Speakers Bureau. Munoz: Kite, a Gilead Company, Kyowa, Bayer, Pharmacyclics/Janssen, Seagen, Acrotech/Aurobindo, Beigene, Verastem, AstraZeneca, Celgene/BMS, Genentech/Roche.: Speakers Bureau; Bayer, Gilead/Kite Pharma, Celgene, Merck, Portola, Incyte, Genentech, Pharmacyclics, Seattle Genetics, Janssen, and Millennium: Research Funding; 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; Targeted Oncology, OncView, Kyowa Kirin, Physicians' Education Resource, and Seagen: Honoraria. Thieblemont: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Gilead Sciences: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Bristol Myers Squibb/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses , Research Funding; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Cellectis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Hospira: Research Funding; Bayer: Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses . Oluwole: Pfizer: Consultancy; Curio Science: Consultancy; Janssen: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. Herrera: Takeda: Consultancy; Genentech: Consultancy, Research Funding; Merck: Consultancy, Research Funding; Seagen: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Kite, a Gilead Company: Research Funding; Gilead Sciences: Research Funding; Tubulis: Consultancy; ADC Therapeutics: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Karyopharm: Consultancy. Ujjani: Loxo: Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; TG Therapeutics: Honoraria; Gilead: Honoraria; ACDT: Honoraria; Kite, a Gilead Company: Honoraria; Adaptive Biotechnologies: Research Funding; Atara Bio: Consultancy; AbbVie: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding. Lin: Sorrento: Consultancy; Legend: Consultancy; Novartis: Consultancy; Bluebird Bio: Consultancy, Research Funding; Gamida Cell: Consultancy; Janssen: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Juno: Consultancy; Vineti: Consultancy; Takeda: Research Funding; Merck: Research Funding; Kite, a Gilead Company: Consultancy, Research Funding. Riedell: Bayer: Honoraria; Karyopharm Therapeutics: Consultancy, Honoraria; Morphosys: Research Funding; Celgene/Bristol-Myers Squibb Company: Consultancy, Honoraria, Research Funding; Verastem Oncology: Honoraria; Kite, a Gilead Company: Honoraria, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding; Takeda: Consultancy; BeiGene: Consultancy; Calibr: Research Funding; Xencor: Research Funding; Tessa Therapeutics: Research Funding. Kekre: Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Lui: Gilead Sciences: Other: stock or other ownership; Kite, a Gilead Company: Current Employment, Other: travel support. Milletti: Kite, a Gilead company: Current Employment; Gilead Sciences: Other: stock or other ownership . Dong: Kite, a Gilead Company: Current Employment; Gilead Sciences: Other: stock or other ownership ; GliaCure/Tufts: Consultancy, Other: advisory role, Patents & Royalties. Xu: Kite, A Gilead Company: Current Employment; Gilead Sciences: Other: stock or other ownership . Chavez: MorphoSys, Bayer, Karyopharm, Kite, a Gilead Company, Novartis, Janssen, AbbVie, TeneoBio, and Pfizer: Consultancy; ADC Therapeutics: Consultancy, Research Funding; Merk: Research Funding; AstraZeneca: Research Funding; MorphoSys, AstraZeneca, BeiGene, Genentech, Kite, a Gilead Company, and Epizyme: Speakers Bureau; BMS: Speakers Bureau.

Abstract 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.