Stevens, Don A.

Abstract Introduction: The Duffy null variant (genotype or phenotype) is associated with lower circulating absolute neutrophil counts (ANC) without increased risk for infection. It is found in ~66% of people identifying as Black or African American vs <1% of people of Asian or European ancestry. Many ANC reference intervals (RI) are not representative of the Duffy null population. There are no adult Duffy null WBC RI and no pediatric Duffy null ANC or WBC RI. Thus, we aimed to assess Duffy null ANC and WBC distributions as well as develop WBC and ANC RI for adults and pediatrics. Methods: Twenty-three sites across the United States collected samples with all sites excluding participants with conditions or medications that could impact ANC or WBC. Only Duffy null participants were included. Sex, race, ethnicity, age, sample collection type, practice setting, Duffy testing method, ANC, and WBC were recorded. The non-parametric method for determining lower limit of normal (LLN), upper limit of normal (ULN), and 90% confidence intervals (CI) around the limits was performed according to the Clinical and Laboratory Standards Institute guidelines. Specific ULN and LLN are not reported as these are preliminary data. The Mann-Whitney U test was used to compare sex and prior data; differences by age groups were assessed with Kruskal-Wallis test. Results: 316 participants 18+ years-old (y/o) were assessed of whom 62.3% (n=197) are female, 97.5% (n=308) identified as Black or African American, and 94.9% (n=300) identified as non-Hispanic. Median age was 47 y/o (IQR: 32-60.5). Median ANC was 2600/uL (IQR: 1860-3530; range: 400-7400); 28.6% (n=90) of participants had ANC <2000/uL, 13.6% (n=43) had ANC <1500/uL, and 2.5% (n=8) had <1000/uL. The 90% CI around the LLN was 810-1070/uL and 5570-7130/uL around the ULN. Consistent with prior data, there was a difference in median ANC by sex (male: 2400/uL; female: 2710/uL; p=0.02). There was no significant difference between this ANC data and previously published Duffy null ANC data (p=0.28). Median WBC was 5.4x109/L (IQR: 4.4-6.5; range: 2.10-11.64) with 4.1% (n=13) of participants with WBC <3.0x109/L. The 90% CI around the LLN is 3.68-4.30x109/L and 11.02-12.97x109/L around the ULN. 515 participants between 0-17 y/o were assessed with 51.8% (n=267) females, 94.8% (n=488) identified as Black or African American, and 94.0% (n=484) identified as non-Hispanic. Among pediatric participants, 56.8% (n=291) had ANC <2000/uL, 38.7% (n=198) had ANC <1500/uL, and 14.4% (n=74) had ANC <1000/uL. For those <1 y/o (n=29), median ANC was 950/uL (IQR: 840-1360; range: 111-3910). There are currently too few samples to predict ULN and LLN. Median WBC was 8.85x109/L (IQR: 7.03-10.16; range: 4.17-13.53). For those 1-5 y/o (n=143), median ANC was 1735/uL (IQR: 1100-2550; range: 207-5810) with a 90% CI around the LLN of 207-820/uL and 4020-5810/uL around the ULN. Median WBC was 6.72x109/L (IQR: 5.64-8.25; range: 3.68-12.97). For those 6-11 y/o (n=128), median ANC was 1590/uL (IQR: 1090-2470; range: 420-5490) with a 90% CI around the LLN of 420-910/uL and 4340-5490/uL around the ULN. Median WBC was 5.42x109/L (IQR: 4.45-6.70; range: 2.80-10.50). For those 12-17 y/o (n=215), median ANC was 2190/uL (IQR: 1460-2930; range: 204-5850) with a 90% CI around the LLN of 540-930/uL and 4350-5510/uL around the ULN. Median WBC was 5.06x109/L (IQR: 4.26-6.20; range of 2.04-9.91). There is a significant difference in ANC by age category (p<0.0001). Conclusion: This is the first report of healthy pediatric Duffy null ANC and WBC data and the first large-scale verification of adult Duffy null ANC and WBC data. Final RI are expected in September 2025. Among adults with the Duffy null phenotype, ANC LLN are likely between 810-1070/uL. Pediatric ANC LLN are likely as low as 207-820/uL (1-5 y/o), 420-910/uL (6-11 y/o), and 540-930/uL (12-17 y/o). These findings redefine “normal” as a significant proportion of healthy participants have ANC or WBC below current RI or below thresholds typically defined as disease. Limitations include heterogeneous sample populations and collection methods. Future analyses will assess differences between collection sites or methods. Ultimately, this work lays the foundation for a more scientifically sound and equitable approach to medical care by ensuring that RI accurately reflects health for the entire community. Healthcare systems are strongly encouraged to adopt Duffy null-specific ANC and WBC RI.

Abstract Introduction Odronextamab, a CD20×CD3 bispecific antibody, demonstrated compelling efficacy with a generally manageable safety profile in heavily pretreated patients (pts) with relapsed/refractory (R/R) follicular lymphoma (FL) in the Phase 2 ELM-2 study (NCT03888105; Kim TM, et al. Ann Oncol 2024). Pts in ELM-2 received odronextamab monotherapy until disease progression or unacceptable toxicity, with dosing frequency reduced to every 4 weeks (Q4W) in those with sustained complete response (CR) for at least 9 months. Here, we report longer term outcomes in the global FL population of ELM-2, including efficacy and safety in pts who switched to Q4W dosing. Methods Details of the ELM-2 study for the R/R FL cohort have been reported previously. Odronextamab monotherapy was administered intravenously, with step-up dosing in Cycle (C) 1 to help mitigate the risk of cytokine release syndrome (CRS), followed by 80 mg in C2–4, then 160 mg every 2 weeks (Q2W) maintenance. Pts with a CR for ≥9 months switched from 160 mg Q2W to Q4W. Pts with the opportunity for response assessment at 12 weeks were included in this analysis. Primary endpoint was objective response rate (ORR) per Lugano criteria by independent central review (ICR). Key secondary endpoints included CR rate, duration of response (DOR), and progression-free survival (PFS) by ICR, overall survival (OS), and safety. Results As of May 5, 2025 data cutoff, 128 pts with R/R FL Grade (Gr) 1–3a were evaluable for efficacy and safety analysis (overall global population). Median duration of odronextamab exposure was 42.9 weeks (range 0.4–264.0) and median follow-up was 34.1 months (95% CI 33.8–37.9). Eligible pts (n=48) switched to Q4W dosing, with median duration of follow-up from time of switching to Q4W dosing of 19.7 months (95% CI 16.2–31.9). Baseline characteristics were generally similar between the overall population and the subgroup of pts who switched to Q4W dosing. The ORR by ICR in the overall population was 80.5% and CR rate was 74.2%, with a median DOR of 26.0 months and median duration of CR of 32.2 months. In pts with sustained CR for ≥9 months who transitioned to Q4W maintenance, the median DOR from time of switching was 31.5 months. In the overall population, the median PFS was 24.1 months and median OS was not reached (estimated 24- and 36-month OS rates: 70.1% and 64.3%, respectively). In pts with CR, median PFS was 38.0 months and median OS was not reached (24- and 36-month OS rates: 80.1% and 75.2%). All 128 pts had treatment-emergent adverse events (TEAEs), with Gr ≥3 TEAEs reported in 112 pts (87.5%). Discontinuation due to TEAEs occurred in 29 pts (22.7%), and 5 pts died due to treatment-related TEAEs. With the 0.7/4/20 mg step-up regimen, CRS was reported in 55.0% (33/60; Gr 3 in 1 pt) of pts, with no new CRS events observed after switching to Q4W. Infections occurred in 81.3% (Gr ≥3, 46.1%) of pts, with COVID-19 (any Gr, 39.8%) the most frequent. After switching to Q4W dosing, the rate of any grade infection was 81.3% (Gr ≥3, 39.6%). Opportunistic infections (narrow SMQ defined) were reported in 18% (Gr ≥3, 8.6%) of pts in the overall population, with 22.9% (Gr ≥3, 8.3%) of pts having an opportunistic infection after switching to Q4W. Conclusions In the ELM-2 study with ~3-year follow-up in heavily pretreated pts with R/R FL, odronextamab continued to demonstrate deep and durable responses, as well as encouraging PFS and OS, particularly in the majority of pts who achieved CR. Responses remain durable in those who switched to Q4W dosing, lasting for a median additional 31.5 months from the time of switching, demonstrating the long-term, continued therapeutic benefit of odronextamab in pts with R/R FL. The safety profile remained generally manageable, with no new safety signals observed, and no evidence of increased infection risk in pts who switched to Q4W maintenance. Updated data will be presented.

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.

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.

Introduction: BTK inhibitors (BTKis) are approved for chronic lymphocytic leukemia (CLL), Waldenström macroglobulinemia (WM), mantle cell lymphoma (MCL), and marginal zone lymphoma (MZL). Disease that progresses on BTKis often has BTK mutations that lead to treatment (tx) resistance; novel BTK-targeting agents that overcome BTKi resistance are needed. BGB-16673 is a heterobifunctional small molecule that binds to BTK and E3 ligase, resulting in BTK degradation via ubiquitination. In preclinical models, BGB-16673 degraded wild-type (WT) BTK and known covalent and noncovalent BTKi-resistant mutant proteins, leading to tumor suppression. Methods: Pts with R/R CLL, WM, MCL, MZL, non-germinal center B-cell diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), or Richter transformation (RT) were eligible for this open-label, first-in-human, phase 1 trial (BGB-16673-101; NCT05006716). Pts must have received ≥2 prior therapies (≥1 for RT) and have an ECOG performance status of 0-2 and adequate end-organ function. In the US and Australia, pts must have received a covalent BTKi (cBTKi) if approved for their disease. BGB-16673 was dosed daily by mouth in 28-day cycles. Escalation using a Bayesian optimal interval design with 6 dose levels (50-600 mg once daily) is planned. Primary objectives are to assess safety/tolerability and establish the maximum tolerated dose (MTD) and recommended phase 2 dose. Key secondary objectives are to assess pharmacokinetics, pharmacodynamics (PD), and preliminary antitumor activity. Safety was assessed according to CTCAE v5.0 (all pts) and iwCLL hematologic toxicity criteria (pts with CLL). Dose-limiting toxicities (DLTs) were assessed in the first 4 weeks. Response was assessed per Lugano criteria for all except CLL (iwCLL 2018 criteria) and WM (iwWM-6 criteria). Results: As of May 26, 2023, 26 pts (10 CLL, 4 MCL, 2 MZL, 4 WM, 4 FL, 1 DLBCL, 1 RT) were enrolled at 5 dose levels (50 mg, 4; 100 mg, 9; 200 mg, 9; 350 mg, 3; 500 mg, 1). Median age was 70.5 y (range, 25-83). Median number of prior therapies was 3.5 (range, 2-9), including cBTKis (n=21; 10 CLL, 4 WM, 4 MCL, 1 MZL, 1 RT, 1 DLBCL), BCL2 inhibitors (n=12; 9 CLL, 2 WM, 1 RT), and noncovalent BTKis (ncBTKis; n=4; 2 CLL, 1 WM, 1 FL). In CLL, del17p/ TP53 mutation (n=8) and unmutated IGHV (n=7) were frequent. Median follow-up was 3.5 mo (range, 0.2-13.9). MTD was not reached. Treatment-emergent AEs (TEAEs) were reported by 88.5% of pts (grade [gr] ≥3, 46.2%; serious, 38.5%). The most common TEAEs were contusion (30.8%; no gr ≥3), pyrexia (23.1%; no gr ≥3), neutropenia/neutrophil count decreased (23.1%; gr ≥3, 15.4%), and lipase increased (23.1%; gr ≥3, 3.8%; all transient and asymptomatic). No hypertension or atrial fibrillation was observed. One pt died from sepsis with possible disease progression. No discontinuations due to AEs occurred. Two pts had dose reductions due to TEAEs (gr 3 hematuria with urinary tract infection and recurrent urothelial carcinoma and gr 2 arthralgia). One DLT occurred in 1 pt at 200 mg (gr 3 maculopapular rash on day 27; after 5-day dose hold, assigned dose was recommenced with persistent gr 1 rash). BGB-16673 exposure increased in a dose-dependent manner. At steady state with doses ≥50 mg daily, BGB-16673 exposure exceeded the calculated half maximal degradation concentration for WT and cysteine 481-mutated BTK for the dosing interval. Preliminary PD data showed deep, sustained reductions in BTK protein levels in peripheral blood and tumor tissue, even at the lowest dose. Most CLL pts experienced lymphocytosis during the first 3 cycles of tx. Twenty of 26 pts (77%) remain on therapy (discontinuation: 4 progressive disease, 2 withdrawal). Of 18 response-evaluable pts, 12 (67%) responded (5/6 CLL, 1/3 MCL, 2/2 MZL, 3/4 WM, 1/2 FL, 0/1 DLBCL; 1 CR in MCL, all others had PR; Figure), including pts who received a cBTKi (n=10) and an ncBTKi (n=2). Responses started at the lowest dose level. All responders remain in response, the longest responder remaining on tx for 60 weeks. Conclusions: Preliminary data from this ongoing, first-in-human study of the novel BTK degrader BGB-16673 demonstrate a tolerable safety profile and clinical responses in heavily pretreated pts with B-cell malignancies, including those with BTKi-resistant disease. Substantial reductions in BTK protein levels in peripheral blood and tumor tissue were also observed, demonstrating proof-of-concept of a strong, on-target effect.

Introduction: ISB 1342 is a humanized CD38xCD3 bispecific T-cell engager using Ichnos proprietary Bispecific Engagement by Antibodies based on the T cell receptor (BEAT ®) platform, designed to simultaneously bind CD38 on multiple myeloma (MM) cells and CD3ε on T cells, to induce tumor killing. This mechanism of action is different from existing monospecific CD38 targeting therapies and was designed to overcome resistance to daratumumab in MM. ISB 1342 exhibits potent killing of the primary MM cells and MM cell lines with low sensitivity to daratumumab ( Pouleau B. et al. Blood 2023; 142 (3): 260-273). We report here, the updated findings from the weekly dose-escalations of intravenous (IV) and subcutaneous (SC) injections of an ongoing, single-agent phase 1 study (NCT03309111) of ISB 1342 in patients with RRMM. Methods: Adult patients with RRMM that relapsed after or were refractory to prior therapies, including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 antibody; received ISB 1342 on a weekly (QW) schedule by IV or SC injection with a priming dose on the first day in 2 parallel dose-escalation schemas. Patients had measurable disease per the International Myeloma Working Group (IMWG) criteria (2016). Dose escalation in the QW schedule began at 0.2/0.3 mg/kg priming/treatment dose and followed a “3 + 3” design. The primary study objectives are to determine the maximum tolerated dose (MTD) and select a recommended phase 2 dose (RP2D) of ISB 1342. Secondary objectives includ evaluation of anti-myeloma activity, pharmacokinetics (PK), pharmacodynamics, and immunogenicity of ISB 1342. Results: As of July 18, 2023, based on ongoing clinical database, 39 subjects had received weekly IV infusions of ISB 1342 in 8 dose-escalation groups from 0.2/0.3 mg/kg to 4.0/16.0 mg/kg as priming/treatment dose; and 7 additional subjects had received weekly SC injections at 2.0/8.0 mg/kg. Two different formulations have been tested in SC group. Median number of cycles administered was 2. The majority were male (57%) and white (74%); 13% were Black or African American. The median age was 69 years (range, 54-76) and the median time since diagnosis was 6.6 years (range, 2.8-22.2). The median number of prior anti-myeloma lines of therapy was 6 (range 1-12). Twenty-one (67%) subjects were considered to be triple-class refractory and 18 (48%) penta-drug refractory. Forty-one (89%) subjects experienced treatment-related adverse events (TRAEs) of any grade. Most TRAEs were grade 1-2, including infusion related reactions (37%), cytokine release syndrome (CRS, 34%, all grade 1or 2), anemia (24%), neutropenia (24%), and thrombocytopenia (17%). Five subjects in SC group (71% of SC) had injection site reaction, all grade 1 or 2. Grade 3 or higher TRAEs occurring in more than 5% of subjects were infusion related reaction (no grade 4), anemia (no grade 4), neutropenia, leukopenia. No Grade 5 TRAE was observed. After QW IV infusion, ISB 1342 serum concentration peaked at the end of infusion and then showed bi-exponential decline. ISB 1342 serum exposures increased in a dose linear fashion across the tested IV infusion dose range. The limited PK data after SC injection suggest slow presentation of ISB 1342 into the systemic circulation leading to lower C max and delayed T max relative to IV. Transient increases in serum cytokines were observed within 24 hours after ISB 1342 dosing, including IFNg, TNFa, IL-2, IL-6 and IL-10. Transient increases in T-cell activation were observed by flow cytometry at 24-48 hours after ISB 1342 dosing at 1.0 / 4.0 μg/kg and above, based on increased expression of CD69 on peripheral blood CD4+ and CD8+ T-cell populations (Figure 1). Comparison of the available data from subjects treated at 2 / 8 μg/kg (Cohort 109) indicated reduced T-cell activation following SC compared to IV administration of ISB 1342. The efficacy signals observed in Cohorts 108 and 109 are consistent with the estimates of the lower boundary of the predicted efficacious dose range using a quantitative systems pharmacology (QSP) model based on preclinical data. Updated clinical data, including response rates and safety data, will be present at the meeting. Conclusions: Treatment with ISB 1342 was well tolerated at higher dose levels evaluated. Observed CRS events were moderate. No increased risk of infection has been observed . Updated safety, efficacy, biomarker and PK data will be presented.

Abstract Anti-CD19 immunotherapy tafasitamab is used in combination with lenalidomide in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) who are ineligible for autologous stem cell transplant. Open-label, phase 1b, First-MIND study assessed safety and preliminary efficacy of tafasitamab + R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) ± lenalidomide as first-line therapy in patients with DLBCL. From December 2019 to August 2020, 83 adults with untreated DLBCL (International Prognostic Index 2-5) were screened and 66 were randomly assigned (33 per arm) to R-CHOP-tafasitamab (arm T) or R-CHOP-tafasitamab-lenalidomide (arm T/L) for 6 cycles. Primary end point was safety; secondary end points included end-of-treatment (EoT) overall response rate (ORR) and complete response (CR) rate. All patients had ≥1 treatment-emergent adverse event, mostly grade 1 or 2. Grade ≥3 neutropenia and thrombocytopenia occurred, respectively, in 57.6% and 12.1% (arm T) and 84.8% and 36.4% (arm T/L) of patients. Nonhematologic toxicities occurred at similar rates among arms. R-CHOP mean relative dose intensity was ≥89% in both arms. EoT ORR was 75.8% (CR 72.7%) in arm T and 81.8% (CR 66.7%) in arm T/L; best ORR across visits was 90.0% and 93.9%. Eighteen-month duration of response and of CR rates were 72.7% and 74.5% (arm T) and 78.7% and 86.5% (arm T/L); 24-month progression-free and overall survival rates were 72.7% and 90.3% (arm T) and 76.8% and 93.8% (arm T/L). Manageable safety and promising signals of efficacy were observed in both arms. Potential benefit of adding tafasitamab + lenalidomide to R-CHOP is being investigated in phase 3 frontMIND (NCT04824092). This study is registered at www.clinicaltrials.gov as #NCT04134936.

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 .