Flinn, Ian W.

Introduction: Brexu-cel is an autologous anti-CD19 CAR T-cell therapy approved in the US and EU for treatment of adults with R/R MCL (after ≥2 prior therapies in EU) based on a high objective response rate (ORR; 93%; 67% complete response [CR] rate) in pts who received the pivotal dose (2×106 anti-CD19 CAR T cells/kg; Cohort 1; N=60) in ZUMA-2 (NCT02601313; Wang et al, N Engl J Med 2020). After ~4 years (y) of median follow-up, Brexu-cel demonstrated a median overall survival (OS) of 46.4 months (mo) in 68 pts with R/R MCL in Cohort 1 (Goy et al. ASH 2023). Cohort 2 was established to assess a lower dose (0.5 x 106 anti-CD19 CAR T cells/kg); however, the risk/benefit ratio of the Cohort 1 dose was deemed the optimal dose before Cohort 2 reached full enrollment. Here we report primary outcomes of Cohort 2 and 5-y outcomes of Cohorts 1 and 2. Methods: Pts with R/R MCL and ≤5 prior therapies including a BTKi received optional bridging therapy (protocol-defined), lymphodepleting chemotherapy, and 1 infusion of brexu-cel. The primary endpoint was ORR (CR + partial response [PR]) per Lugano classification (Cheson et al. J Clin Oncol. 2014) by independent radiology review committee (IRRC) assessment. Key secondary endpoints were duration of response (DOR), best objective response (BOR), progression-free survival (PFS), OS, and safety. After ≥24 mo of assessment, pts could transition to long-term follow-up (LTFU), NCT05041309, where they were monitored for late-onset targeted/serious adverse events (AEs) possibly related to brexu-cel, presence of replication-competent retrovirus (RCR), and/or insertional mutagenesis. Descriptive statistics are reported herein. Results: As of the primary analysis data cutoff date, July 24, 2019, 17 pts enrolled in Cohort 2, 14 (82%) of whom were treated with brexu-cel with median follow-up of 16.0 mo (range, 13.9-18.0). Pt characteristics for Cohort 2 (N=14) were similar to Cohort 1; median (range) age and number or prior therapies was 61.5 y (52-73) and 3 (2-5); 100% US-treated, 79% male, 71% extranodal disease, 50% intermediate or high s-MIPI scores, 50% refractory to last therapy, and 43% had prior autologous stem cell transplantation. ORR was 93% (95% CI, 66.1-99.8) per IRRC; 64% had a CR (95% CI, 35.1-87.2), 29% had a PR (95% CI, 8.4-58.1) and 1 pt was not assessed. All 14 pts had ≥1 AE of any grade (Gr), with Gr ≥3 AEs occurring in 93% of pts; the most common being hypotension (50%), white blood cell count decrease (50%), anemia (43%), and neutrophil count decrease (43%). Rates of Gr ≥3 cytokine release syndrome (CRS) and neurological events were 7% and 43%, respectively. As of April 1, 2024, median follow-up (range) for Cohort 1 and 2 was 67.8 mo (58.2-88.6; N=68) and 72.3 mo (70.1-74.3; N=14), respectively. In Cohort 1, 24 pts were still alive (35%; 2 withdrew consent and 1 lost to follow up) and 44 pts died (65%). In Cohort 2, 8 pts were still alive (57%; 2 withdrew consent and 1 lost to follow up) and 6 pts died (43%). A total of 27 pts (Cohort 1, n=23; Cohort 2, n=4) enrolled in the LTFU study by data cutoff with a median follow-up time of 70.2 mo (range, 58.2-88.6). Median (95% CI) investigator-assessed DOR and PFS were 36.5 mo (17.7-48.9; n=60; 17 patients in ongoing response, all CR) and 25.3 mo (12.7-46.6; N=68) in Cohort 1; and 57.5 mo (4.7-not estimable [NE]; n=12; 3 pts in ongoing response, all CR) and 29.5 mo (3.3-NE; N=14) in Cohort 2. Median OS (95% CI) and 60-mo OS rates (95% CI) were 46.5 mo (24.9- 60.2) and 38.5% (26.7-50.1) in Cohort 1; and not reached (9.4-NE) and 53.6% (23.8-76.2) in Cohort 2. One pt had 3 ongoing AEs on LTFU, hypogammaglobulinemia and 2 viral infections that arose prior to LTFU. Two pts died on LTFU, both due to progressive disease; no new secondary malignancies or RCR cases were reported. Conclusions: Consistent with Cohort 1, brexu-cel demonstrated a high ORR, durable responses, and an expected safety profile in pts with R/R MCL in Cohort 2 despite the lower dose. However, small sample size limits interpretation of these results. With >5 y of median follow-up, pts in Cohort 1 and 2 continued to experience durable responses with high 60-mo OS rates. No new safety signals were detected and no secondary malignancies or RCR cases were reported in LTFU. Additionally, ZUMA-2 results are consistent with real-world outcomes of brexu-cel in the post BTKi R/R MCL setting (89% ORR and 81% CR rate; Wang Y, et al. J Clin Oncol. 2023). These results support the continued use of brexu-cel in R/R MCL.

Background: Mosunetuzumab (Mosun), a CD20xCD3 bispecific antibody, received accelerated approval for the intravenous treatment of patients (pts) with relapsed/refractory (R/R) follicular lymphoma (FL) who have received ≥2 prior lines of systemic therapy. Mosun can be administered in the outpatient setting with a fixed treatment duration. In an ongoing Phase I/II study, Mosun administered subcutaneously (SC) induced durable responses with a manageable safety profile in pts with previously untreated low-tumor burden FL (LTB; Flinn et al. ASH 2023). Efficacy, safety and pharmacodynamic profiles of Mosun SC are being evaluated in an open-label, multicenter, Phase II study (MorningSun; NCT05207670) in pts with B-cell non-Hodgkin lymphomas, including previously untreated FL. Here we present >8-month follow-up efficacy, safety and biomarker data for Mosun SC in first-line, LTB FL. Methods: Pts had untreated Grade (Gr) 1 or 2 FL, LTB by Groupe d'Etude des Lymphomes Folliculaires criteria, Ann Arbor stage III/IV disease, and Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-2. Mosun SC injection was administered with step-up dosing in Cycle (C) 1 (Day [D] 1, 5mg; D8, 45mg; D15, 45mg), then 45mg on D1 of each 21-day cycle. Hospitalization was not mandatory. Pts with a complete metabolic response (CMR) after C8 could complete therapy. Pts with a partial metabolic response (PMR) or stable disease continued treatment for up to 17 cycles. Dexamethasone premedication was mandatory in C1 and C2 and optional thereafter. The primary endpoint was progression-free survival at 24 months. Exploratory analyses assessed cytokine levels in pts with versus without cytokine release syndrome (CRS) and pharmacodynamic changes in T and B cells in a subgroup of pts. Results: As of February 7, 2024, 65 pts were enrolled in US community (n=41) and academic (n=24) centers. At baseline, median age was 63 years (range: 34-82). Most pts had an ECOG PS of 0 (83.1%) or 1 (15.4%); 29 pts (44.6%) had extranodal involvement and 3 pts (4.6%) had B symptoms. Median duration of follow-up was 8.6 months (95% confidence interval [CI]: 5.7-10.9). Median number of cycles was 8 (range: 1-17). Among 60 pts with ≥1 post-baseline tumor assessment, the objective response rate was 95.0% (95% CI: 86.1-99.0; n=57) and CMR was 83.3% (95% CI: 71.5-91.7; n=50). Median time to response was 2.8 months (range: 2.3-8.3). At data cut-off, responses were ongoing in 48 pts with a CMR and in 5 pts with a PMR. In 64 safety-evaluable pts, the most common adverse event (AE) was injection-site reaction (70.3%; Gr 1, 65.6%; Gr 2, 4.7%). CRS by ASTCT occurred in 30 pts (46.9%; Gr 1, 39.1%; Gr 2, 7.8%); CRS events presented early in C1 (53.1%; Gr1, 45.3%; Gr2, 7.8%) and C2 (Gr1, 1.6%). Nineteen pts received CRS treatment (tocilizumab, 7.8%; steroids, 7.8%; tocilizumab + steroids, 4.7%; fluids, 3.1%; low-flow oxygen, 1.6%); 8 pts had a serious AE and were hospitalized. All CRS events resolved. Other common AEs included headache (45.3%; Gr 1, 29.7%; Gr 2, 15.6%), fatigue (45.3%; Gr 1, 35.9%; Gr 2, 9.4%), maculo-papular rash (31.3%; Gr 1, 14.1%; Gr 2, 15.6%; Gr 3, 1.6%), and increased alanine aminotransferase (28.1%; Gr 1, 21.9%; Gr 2, 4.7%; Gr 3, 1.6%). Gr 3/4 AEs in ≥5% of pts were neutropenia without fever (12.5%; Gr 3, 4.7%; Gr 4, 7.8%) and lymphopenia (7.8%; Gr 3, 1.6%; Gr 4, 6.3%). Suspected immune effector cell-associated neurotoxicity syndrome occurred in 2 pts (confusional state, Gr 1, n=1; Gr 2, n=1); all events resolved. Infections occurred in 30 pts (46.9%; Gr 1, 7.8%; Gr 2, 31.3%; Gr 3, 7.8%) with the most common (≥10%) being COVID-19 (17.2%; Gr 1, 7.8%; Gr 2, 7.8%; Gr 3, 1.6%) and upper respiratory tract infections (12.5%; Gr 1, 3.1%; Gr 2, 9.4%). One pt had a Gr 5 (fatal) AE 13.7 months after treatment was completed (reported as unrelated to Mosun; cause unknown). After the first Mosun dose, cytokine levels significantly increased on C1D2 (interleukin-6, n=44, p≤0.001; interferon-γ and tumor necrosis factor-α, n=41, p≤0.001). This spike in cytokine levels did not differ in pts with (n=19) versus without (n=25) CRS events in C1. Conclusions: Mosun SC monotherapy shows encouraging high efficacy as a fixed-duration treatment in first-line LTB FL. A manageable safety profile was reported, supporting ease of access for patients with drug administration in outpatient settings. Longer follow-up is needed to confirm long-term durability of response and safety.

Introduction: Historically, older patients (pts) with relapsed/refractory large B-cell lymphoma (R/R LBCL) were often deemed ineligible for curative-intent autologous stem cell transplant (ASCT) due to age and concern for increased toxicity related to comorbidities. We previously demonstrated in the pivotal ZUMA-7 study that older pts with R/R LBCL can safely receive axicabtagene ciloleucel (axi-cel) as second-line (2L) therapy with improved event-free survival (EFS), response rate, and quality of life compared with standard of care (SOC) based on results from the primary EFS analysis (Westin, et al. Clin Cancer Res. 2023). At a median follow-up of 47.2 months (mo), results from the ZUMA-7 primary overall survival (OS) analysis demonstrated superior OS in the intention-to-treat (ITT) analysis (hazard ratio [HR], 0.73; 95% CI, 0.54-0.98; stratified two-sided log-rank P=0.03; Westin, et al. N Engl J Med. 2023; NCT03391466). We now report updated efficacy and safety results from the primary OS analysis among ZUMA-7 pts aged ≥65 years (y) and ≥70 y. Methods: Eligible pts were randomized 1:1 to axi-cel or SOC (2-3 cycles of platinum-based chemoimmunotherapy; responding pts proceeded to high-dose chemotherapy with ASCT). The primary OS analysis occurred 5 y after the first pt was randomized (01/25/2018) per protocol. Other endpoints included progression-free survival (PFS) per investigator assessment and safety. A planned subgroup analysis of pts aged ≥65 y was conducted in addition to an analysis for those ≥70 y. Multivariate analyses were performed to examine treatment efficacy with axi-cel compared with SOC after adjusting for multiple covariates, including sex, disease type, molecular subgroup, lactate dehydrogenase (LDH), tumor burden, and age; strata for these analyses included second-line age-adjusted International Prognostic Index (aaIPI), and relapsed vs refractory disease. Exploratory analyses were conducted to determine the association between OS and axi-cel product characteristics for pts aged ≥65 y. Results: A total of 109 pts were included in the analysis (axi-cel: 51 were ≥65 y, 26 of whom were ≥70 y, maximum age was 80 y; SOC: 58 were ≥65 y, 27 of whom were ≥70 y, maximum age was 81 y). Compared with SOC pts at baseline, more axi-cel pts had high-risk features, including aaIPI 2-3, elevated LDH, and high-grade B-cell lymphoma. At a median follow-up of 46.6 mo, OS was prolonged in the axicel vs SOC arm in pts aged ≥65 y (HR, 0.691; 95% CI, 0.401-1.190) and for those ≥70 y (HR, 0.330; 95% CI, 0.135-0.809). Similar results were observed using the piecewise Cox regression model. The median OS for axi-cel and SOC pts was 43.5 mo (95% CI, 20.9-not estimable [NE]) and 19.6 mo (95% CI, 12.3-NE), respectively, among those aged ≥65 y, and 24.7 mo (95% CI, 12.8-NE) and 11.2 mo (95% CI, 6.1-NE), respectively, among those aged ≥70 y. In the SOC arm, 57% and 52% of pts received subsequent cellular immunotherapy off protocol in pts aged ≥65 y and ≥70 y, respectively. Multivariate analyses demonstrated an even greater OS benefit with axi-cel over SOC when adjusting for differences in baseline characteristics in pts aged ≥65 y (HR, 0.526; 95% CI, 0.266-1.041) and in pts aged ≥70 y (HR, 0.184; 95% CI, 0.045-0.755). PFS assessed by investigator confirmed benefit of axi-cel over SOC in pts aged ≥65 y (HR, 0.406; 95% CI, 0.230-0.715) and in pts aged ≥70 y (HR, 0.206; 95% CI, 0.078-0.547). The median PFS for axi-cel and SOC pts was 28.7 mo (95% CI, 5.1-NE) and 5.0 mo (95% CI, 2.8-7.2), respectively, for those aged ≥65 y, and 11.4 mo (95% CI, 4.1-NE) and 2.7 mo (95% CI, 1.7-5.0), respectively, for those aged ≥70 y. No new treatment-related deaths occurred since the primary EFS analysis. There were no manufacturing failures for any pt who underwent leukapheresis. Similar associations between product characteristics and outcomes were observed among the elderly and overall populations, including improved OS associated with a greater (>median) proportion of juvenile or stem memory T-cell phenotype cells (CCR7+CD45RA+ T cells) in the axi-cel product among pts aged ≥65 y (HR, 0.369; 95% CI, 0.138-0.984). Conclusion: Axi-cel as 2L therapy prolonged survival over SOC in pts aged ≥65 y, including in pts aged ≥70 y. These findings confirm that age alone should not be a barrier for consideration of CAR T-cell therapy, supporting the use of axi-cel as a curative-intent 2L therapeutic option for older pts with R/R LBCL.

Background: Despite the efficacy of covalent (c) Bruton tyrosine kinase inhibitors (BTKi) in R/R MCL, disease relapse arises through evolution of resistance mechanisms or development of cBTKi intolerance. Pirtobrutinib, a highly selective, non-covalent (reversible) BTKi has favorable oral pharmacology that enables continuous BTK inhibition throughout the daily dosing interval regardless of the intrinsic rate of BTK turnover. Pirtobrutinib is the first BTKi to demonstrate durable efficacy following prior cBTKi therapy in heavily pre-treated R/R MCL and was well-tolerated with a low frequency of treatment discontinuation due to toxicity (Wang et al., JCO, 2023). Pirtobrutinib is approved in the USA to treat relapsed or refractory MCL after at least two lines of systemic therapy including a prior cBTKi. Here, we report updated results of pirtobrutinib therapy in all patients (pts), including those with biologically high-risk R/R MCL with a median survival follow-up of 24.2 months (range, 18.2-29.8). Methods: Pts with R/R MCL received pirtobrutinib monotherapy in the multicenter Phase 1/2 BRUIN trial (NCT03740529). Efficacy was assessed in all cBTKi pre-treated pts, as well as in cBTKi treatment-naïve pts. Key endpoints included overall response rate (ORR) as assessed by independent review committee per Lugano 2014 criteria, duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Pts were included across the dose escalation range and expansion (25-300 mg/day) with 93% (n=141) receiving at least one dose of 200 mg/day, the FDA-approved dose. A data cut of 05 May 2023 was utilized. Results: Among all 152 pts with R/R MCL who received a prior cBTKi, the median age was 70 years (range, 46-88), and 52% had intermediate-risk and 28.3% had high-risk sMIPI scores. Median prior lines of therapy were 3 (range, 1-9), including an anti-CD20 antibody (96.7%), chemotherapy (90.1%), immunomodulator (17.1%), stem cell transplant (21.7%), BCL-2 inhibitor (15.8%), CAR-T cell therapy (8.6%), and PI3K inhibitor (3.9%). Among pts with high-risk biomarker data available, 30/60 (50%) had TP53 mutations and 45/63 (71%) had a Ki-67 index of ≥30%. The ORR for cBTKi pre-treated pts was 49.3% (95% CI, 41.1-57.6), including 15.8% complete responses (n=24) and 33.6% partial responses (n=51), whilst cBTKi naïve pts (n=14) had an ORR of 85.7% (95% CI, 57.2-98.2). The ORR among 128 pts who had discontinued a prior cBTKi due to PD and 21 pts who had discontinued for toxicity/other reasons was 43.0% and 90.5%, respectively. Among the 75 responding cBTKi pre-treated pts, the median DOR was 21.6 months (95% CI, 9.2-27.2) at a median follow-up of 24 months. The 18- and 24-month DOR rates were 51.9% (95% CI, 37-64.8) and 38.9% (95% CI, 22.7-54.8), respectively. ORR and DOR by high-risk subgroups (including blastoid/pleomorphic variants, Ki-67 index ≥30%, and TP53 mutations) are shown in Table 1. The 18- and 24-month DOR rates among 12 responding cBTKi naïve pts were both 90.0% (95% CI, 47.3-98.5). The median PFS and OS for cBTKi pre-treated pts was 5.6 months (95% CI, 5.3-9.2), and 23.5 months (95% CI, 17.1-NE), respectively. In the MCL cohort (n=166), the most frequent treatment-emergent adverse events (TEAEs) were fatigue (31.9%), diarrhea (22.3%), and dyspnea (17.5%). The most common Grade ≥3 TEAE was neutropenia/neutrophil count decreased (13.3%) and the rate of Grade ≥3 infections was (19.9%). Grade ≥3 hemorrhage/hematoma (2.4%) and all-grade atrial fibrillation/flutter (3.6%) were infrequent. Overall, 8 pts (5%) had treatment-related AEs leading to dose reductions and 5 (3%) had treatment-related AEs leading to pirtobrutinib discontinuation. Conclusion: Pirtobrutinib continues to demonstrate durable efficacy and a favorable safety profile in heavily pre-treated R/R MCL pts with prior cBTKi therapy. High ORRs were observed in pts who had PD on a prior cBTKi, and in pts with high-risk disease features including blastoid/pleomorphic variants, elevated Ki-67 index, and TP53 mutations.

7514 Background: Pirtobrutinib is a highly selective, non-covalent (reversible) BTKi. Here, we report updated results of pirtobrutinib in patients (pts) with cBTKi pre-treated relapsed/refractory (R/R) MCL and more than 3 years follow-up from start of enrollment. Methods: Pts with cBTKi pre-treated R/R MCL received pirtobrutinib monotherapy in a multicenter phase 1/2 BRUIN trial (NCT03740529). Efficacy was assessed in the prespecified primary efficacy cohort that comprised the first 90 enrolled pts who had measurable disease, had received a prior cBTKi, and had no known central nervous system involvement. The primary endpoint was overall response rate (ORR) as assessed by independent review committee. Secondary endpoints included duration of response (DOR) and safety. A data cut of 29 July 2022 was utilized. Results: Among MCL pts who received a prior cBTKi (n=90), median age was 70 years (range, 46-87), median prior lines of therapy were 3 (range, 1-8), 82% discontinued a prior cBTKi due to disease progression, and 78% had intermediate/high risk sMIPI score. Of samples available, 17/36 (47%) had TP53 mutations and 25/34 (74%) had Ki67 ≥30%. The ORR was 57% (95% CI, 46-67), including 19% complete responses (n=17) and 38% partial responses (n=34). At a median follow-up time of 13 months, the median DOR among the 51 responding pts was 17.6 months (95% CI, 7.3-27.2). The 12- and 18-month estimated DOR rates were 58% (95% CI, 41-72) and 45% (95% CI, 27-61), respectively. ORR and DOR by subgroups are shown in the Table. The median progression-free survival was 7.4 months (95% CI, 5.3–13.3). The median overall survival was 23.5 months (95% CI, 15.9-NE). In the MCL safety cohort (n=166), the most frequent treatment-emergent adverse events (TEAE) were fatigue (31%), diarrhea (22%), and anemia (17%). The most common Grade ≥3 TEAE was neutropenia (15%). Grade ≥3 TEAE of hemorrhage (3%) and atrial fibrillation/flutter (2%) were infrequent. Only 5 (3%) pts discontinued due to a treatment-related AE. Conclusions: Pirtobrutinib continues to show durable efficacy and a favorable safety profile in heavily pre-treated R/R MCL pts with prior cBTKi therapy. Responses were observed in pts with high-risk disease features including pts with blastoid/pleomorphic variants, elevated Ki67 index, and TP53 mutations. Clinical trial information: NCT03740529 . [Table: see text]