Citations

Cellular Immunotherapies: Late Phase and Commercially Available Therapies The Impact of Inotuzumab Ozogamicin (InO) Treatment on Brexucabtagene Autoleucel (Brexu-cel) Outcomes in Adults with Relapsed/Refractory B-cell Acute Lymphoblastic Leukemia (B-ALL) Introduction: Brexu-cel is the first approved CD19-directed chimeric antigen receptor (CAR) T-cell therapy for adult patients (pts) with relapsed/refractory (r/r) B-ALL. InO, an anti-CD22 antibody drug conjugate, is also approved for the same indication. With the accessibility to several targeted therapies in r/r B-ALL, the optimal sequence remains uncertain. The effect of prior treatment with InO on brexu-cel outcomes remains underreported, especially as a bridging therapy, as well as the effect of previous response to InO on post brexu-cel outcomes. Methods: This is a retrospective multicenter analysis from 25 U.S. institutions of adults (≥18 years) with r/r B-ALL treated with commercial brexu-cel from 2021 to 2023 post FDA approval. Methodologies for assessing minimal residual disease (MRD) (minimal threshold of 10 -4) included flow cytometry, NGS, or qPCR depending on institutional practice. Progression-free survival (PFS) and overall survival (OS) were calculated from day of brexu-cel infusion and were not censored for hematopoietic cell transplant (HCT) or maintenance. All living patients were censored at the time of last follow-up prior to data lock, which occurred on June 30, 2023. Results: Among 152 infused, 83 (54.6%) had pre-CAR InO therapy (InO-exposed), with a median of 3 administered doses (range: 1-22). Within the InO-exposed cohort, 23 (28%) pts received InO as a CAR T-cell bridging therapy (ie, between apheresis and lymphodepletion) with or without pre-apheresis and 60 (72%) pts received InO only during pre-apheresis. Baseline characteristics for InO exposed and InO-naïve pts are shown in Table 1. InO-exposed pts had higher median prior lines of therapies (4 vs. 3; p= 0.05), more frequently had active disease (≥5% marrow blasts) at the time of apheresis (67% vs. 44%, p= 0.02), and had lower incidence of Ph+ disease (19% vs. 45%, p=0.003), compared to InO-naïve pts, respectively. The incidences of cytokine release syndrome (CRS) (85% vs. 85%, p= 0.26) and ICANS (58% vs. 57%, p= 0.36) post infusion were similar, and post-infusion death in remission occurred in 17% and 12% among InO-exposed and InO-naïve pts, respectively. Morphological complete remission (CR) and MRD- rates following brexu-cel infusion were 89% and 77% for InO-exposed pts, and 92% and 70% for InO-naive pts, respectively. Post CAR therapy, more InO-naïve pts underwent consolidation/maintenance therapy (transplant, chemotherapy, or TKIs) compared to InO-exposed pts (41% vs. 19%, p= 0.004). The median follow-up after brexu-cel was 8.4 (range) months. Median OS (not reached (NR) vs. 12 months; p= 0.033) and median PFS (NR vs. 7 months; p= 0.029) were superior in InO-naïve pts compared to InO-exposed pts, respectively. However, after adjusting for pre-apheresis disease burden and post-CAR maintenance therapy, there were no longer significant differences in OS (HR= 1.25;95%CI: 0.62-2.53; p= 0.53) or PFS (HR= 1.24;95%CI:0.71-2.16, p=0.45) based on pre-CAR InO exposure. When InO-exposed pts were stratified based on prior InO-response (CR vs. no response), InO-responsive pts had superior estimated 12-month OS (64%) and PFS (38%) relative to InO-refractory pts (OS: 33%; PFS: 34%), but inferior to InO-naïve pts (OS: 75%; PFS 56%), with p-values of 0.0001 and 0.021 for OS and PFS, respectively (Figure 1). The timing of pre-CAR InO therapy did not impact brexu-cel survival outcomes, with comparable estimated 12-month OS (43% vs. 58%, p= 0.35) and PFS (46% vs. 38%, p= 0.57) for InO-exposed pts during bridging therapy and patients who received InO as a therapy prior to apheresis. Conclusion: After adjusting for pre-CAR disease burden and post-CAR consolidation/maintenance, we found that prior InO exposure does not significantly associate with PFS or OS following brexu-cel. However, relative to InO-responsive patients, patients who were InO-refractory appear to have worse post-CAR survival outcomes. Finally, timing of InO administration (ie as a prior line of therapy or as CAR bridging) did not influence outcomes brexu-cel outcomes.

Background : Allogeneic hematopoietic cell transplant (alloHCT) is the only potentially curative therapy for patients (pts) with relapsed or refractory (R/R) AML. Only a minority undergo alloHCT as they typically have dismal outcomes due to high relapse rates, especially those with TP53 mutations and active disease. Additionally, older pts cannot tolerate intensive treatment and hence are not eligible for alloHCT. 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells. 131I-apamistamab led induction and conditioning can thus provide these pts access to alloHCT potentially leading to better disease control and outcomes even in pts with the TP53 mutation. Methods: The SIERRA trial (NCT02665065) is a multi-center, randomized, controlled Phase 3 study comparing the rate of durable complete remission (dCR) lasting ≥6 months (mos) after complete remission with/without platelet recovery (CR/CRp) between two groups: 131I-apamistamab led induction and conditioning followed by alloHCT vs physician's choice of conventional care (CC). Pts were randomized (1:1) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. CR/CRp assessment was 28-56 days post alloHCT or 28-42 days post initiation of therapy in the CC group. Pts in the CC group not achieving leukemia-free state could crossover (CO) to 131I-apamistamab. We report the characteristics and outcomes of all pts with TP53 mutation who were enrolled in the SIERRA trial. Results: In total, 153 pts were randomized (CC, n=77; 131I-apamistamab, n=76). All pts who received the therapeutic dose of 131I-apamistamab (n=66) underwent HCT vs 14 (18.2%) in the CC group. Of evaluable pts, dCR rates at 6 months were 22% in the 131I-apamistamab group vs 0% in the CC group (95% CI;12.29, 34.73; p<0.0001). A total of 37 pts with TP53 mutation were enrolled (CC=20; 131I-apamistamab =17) with a prevalence of 24.2%. Table 1 shows the baseline characteristics of these pts. Median overall survival (OS) for pts in the 131I-apamistamab group, who were TP53 negative was 6.37 mos compared to 5.72 mos for the TP53 mutation positive pts (HR=0.66; 95% CI [0.37, 1.18]; p=0.16). In the CC group (including CO pts), the median OS for TP53 positive pts was 2.96 mos. When the CC group without CO were analyzed, the median OS was 6.51 mos and 1.66 mos for the TP53 mutation negative and positive groups respectively (HR=0.28; 95% CI [0.12, 0.67]; p=0.0022). For TP53 mutation positive pts who received 131I-apamistamab ( 131I-apamistamab plus CO pts), the median OS was 5.49 mos compared to a median 1.66 mos in pts who did not receive 131I-apamistamab (CC pts without CO) [(HR=0.23; 95% CI [0.10, 0.52]; p=0.0002) (Figure 1)]. Conclusion: Pts with TP53 mutated R/R AML have a dismal prognosis and are seldom offered alloHCT due to high post-transplant relapse rates. 131I-apamistamab led alloHCT significantly improves survival outcomes in pts with TP53 mutations, commensurate with rates observed in pts with wildtype TP53, thereby overcoming the negative impact of this mutation. These data clearly support the use of 131I-apamistamab led induction and conditioning and alloHCT in R/R AML, including in patients with a TP53 mutation.

Background: Most older patients (pts) with relapsed or refractory (R/R) AML cannot tolerate intensive treatment and are not eligible for curative allogeneic hematopoietic cell transplant (alloHCT). 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells. 131I-apamistamab led induction and conditioning can provide these pts with access to alloHCT. Methods: SIERRA (NCT02665065) was a multi-center, randomized, controlled phase 3 study comparing the efficacy of 131I-apamistamab led induction and conditioning versus physician's choice of conventional care (CC) in pts ≥55 years of age with active, R/R AML. Pts were randomized (1:1, n=153) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. Primary endpoint was durable complete remission (dCR), defined as CR ≥6 mos with or without platelet recovery (CRp). Pts not achieving CR in CC could crossover (CO) to receive 131I-apamistamab. Treatment with 131I-apamistamab was prescribed as an individualized dose for each pt following a dosimetric infusion and biodistribution analysis, with the prescribed activity of 131I set to deliver a maximum estimated radiation dose to the liver as the dose limiting organ of 24 Gy (determined as the maximum tolerable dose (MTD)) in earlier studies), thereby providing the highest dose to the diseased bone marrow and circulating leukemic cells without exceeding individual organ radiation dose tolerances. Here, we performed an analysis to determine whether a radiation dose-response relationship could be established based on either 1) administered radiation dose to liver and the rate of achieving the primary endpoint of dCR (with 95% binomial confidence intervals) or 2) dCR rate and the ratio of bone marrow/liver absorbed radiation dose as an indicator of favorable biodistribution between target/risk organ. Results: All pts receiving the therapeutic dose of 131I-apamistamab (n=66) were able to receive an alloHCT, and the primary endpoint (dCR) was achieved in 13 pts receiving 131I-apamistamab vs 0 pts in CC (p<0.0001). The median absorbed liver dose was 21.6 Gy (IQR: 21.0 - 22.8 Gy), median absorbed dose to bone marrow was 16.0 Gy (IQR: 11.5 - 22.3 Gy), and median ratio between marrow/liver dose was 0.79 (IQR: 0.52 - 1.02). Table 1 shows the distribution and rate of dCR for pts who received above or below 22 Gy administered dose to liver (24 Gy to liver was the established MTD from earlier studies, in which doses were escalated in 2 Gy increment and thus, 22 Gy represented MTD-1), and for pts stratified by marrow/liver dose ratio (higher ratio representing more favorable biodistribution). Pts with ≤22 Gy liver dose had a dCR rate of 13.5% vs. 27.6% for pts with >22 Gy liver dose, and pts with <median dose to bone marrow had a dCR rate of 12.1% vs. 27.3% for pts with ≥median estimated marrow dose. Importantly, pts with increasingly favorable biodistribution had nominally higher dCR rates of 10.0%, 20.0% and 26.9% for a marrow/liver ratio <0.6, 0.6-0.9 and >0.9, respectively, as illustrated in Figure 1. Taken together this demonstrates a radiation dose-response for the primary endpoint in this study. Overall, safety was similar across doses to the liver. Conclusion: 131I-apamistamab led induction and conditioning followed by alloHCT resulted in statistically significant improvement in dCR at 6 mos vs conventional care. A dose-response was demonstrated for pts receiving 131I-apamistamab with those receiving a liver dose closer to the MTD of 24 Gy having about twice the dCR rate compared to pts 22 Gy (MTD-1) or less. We also found pts with higher marrow/liver ratio experienced considerably higher rates of dCR which highlights the importance of maximizing the dose to target tissues, within the limits of established risk organ dose tolerances.

Introduction: In October 2021, the FDA approved brexu-cel for the treatment of adults ≥ 18 years old with R/R B-ALL. Following this approval, a consortium of cancer centers was formed across the US to investigate outcomes following commercial brexu-cel use for adults with R/R B-ALL. One area of interest is the toxicity profile of brexu-cel when given in the real-world context, including the respective incidences and severity of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS). Methods: Eligible pts included adults ≥ 18 years old who received commercial brexu-cel starting in October 2021 onward at a participating center in the US (N = 25). Retrospective patient data were collected across participating institutions, with the most recent data lock occurring on June 30, 2023. Criteria from the ASTCT were used to grade CRS and ICANS severity. Statistical methods included the use of medians and simple ratios for descriptive outcomes; univariate logistic regression models were used to assess the association of various factors with the probability of CRS and ICANS, and Cox regression was used to examine the association of each with the hazards of mortality and failure for event-free survival (EFS; earliest of progression, relapse, or death). Results: Key demographics and toxicities are described in Tables 1 and 2 (respectively). Of the 152 pts infused with brexu-cel, 82% (N = 125) developed CRS and 56% (N = 85) developed ICANS. CRS and ICANS did NOT develop in 12% (N = 19). Twenty percent of all pts (N = 31) required ICU-level care for management of CAR-related toxicities, with a median LOS in ICU of 4 days (range 1-79). In univariate models, grade 3+ ICANS was most likely to occur in pts with active disease (≥ 5% marrow blasts and/or EMD) at the time of apheresis (OR 2.63, 1.28-5.38, p = 0.008); a numerical increase for grade 3+ CRS (OR 2.35, 0.69-8, p = 0.17) was seen in pts with active disease at apheresis. Therapies received for these CAR-related toxicities included steroids, tocilizumab (toci), and anakinra (Table 2). Among pts who received steroids (N = 94), 37% (N = 34) achieved a sufficient response to the first steroid trial and did not require subsequent therapies; otherwise, toxicities improved with the first steroid course but later worsened in 16% (N = 15); the first trial of steroids was not effective but improved when further steroids were given in 31% (N = 29); there were no responses to any doses of steroids in 10% (N = 9). In pts receiving toci (N = 103), 31% (N = 32) achieved a sufficient response to the first dose and did not require any further therapy; toxicities improved with the first dose but later worsened in 31% (N = 32); the first dose was ineffective but improvement was seen with subsequent doses in 21% (N = 22); 9% (N = 9) did not respond at all to toci. The rate of death within day +28 was 6% (N = 9), and the respective causes were typically multifactorial: CRS was implicated in 3 cases, ICANS in 3, infection in 5, disease relapse/progression in 2, and HLH in 1 case. In total, uncontrolled ICANS was implicated in the death of 6 pts (between day +9 to day +106). HLH was reported in 6 pts: in most cases, this was a biochemical diagnosis, and it either overlapped with concurrent CRS or infection or occurred following CRS/ICANS. The most common infections between day 0 and day +28 included bacteremia in 8% of pts (N = 12), fungal infections in 4% (N = 6), pneumonia in 3% (N = 5), and CMV infections in 3% (N = 4). The fungal infections included 4 instances of invasive sinopulmonary infections (2 due to aspergillus; 2 due to mucormycosis) and 2 cases of candidemia. With both CRS and ICANS treated as a time-varying covariate, the development of grade 3+ CRS was associated with a higher hazard of death (HR 2.38, 1.00-5.66, p = 0.05); grade 3+ ICANS was not associated with a demonstrably higher risk of death (HR 1.11, 0.60-2.05, p = 0.74). The HR of EFS failure for Grade 3+ CRS was 1.81 (0.87-3.79, p = 0.12) and for grade 3+ ICANS HR = 0.93 (0.56-1.53, p = 0.77). Conclusions: In this real-world study of toxicities from brexu-cel use for adults with R/R B-ALL, we observed CRS and ICANS in the majority of pts, and no new safety signals were observed. Rates of severe CRS and ICANS were more common with active disease. Interestingly, though CRS-related mortality was rare, grade 3+ CRS was associated with a higher risk of death. Efforts to identify mechanisms and mitigable risk factors for these toxicities are warranted.

Introduction In October 2021, brexucabtagene autoleucel (brexu-cel) received U.S. FDA approval as the first CAR T-cell therapy for adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL) based on the 55-patient ZUMA-3 Phase II study. We subsequently established ROCCA and now report on the largest cohort of patients treated with commercial brexu-cel for r/r B-ALL to date. Methods Adults (18+) with r/r B-ALL infused with commercial brexu-cel across 25 U.S. institutions were included. ASTCT consensus criteria were used to score CRS and ICANS. Methodologies for assessing MRD (minimal threshold of 10 -4) included flow cytometry, NGS, or qPCR depending on institution practice. Duration of remission (DOR) was calculated from time of complete response (CR); progression-free survival (PFS) and overall survival (OS) were calculated from day of brexu-cel infusion and were not censored for hematopoietic cell transplant (HCT) or maintenance. All living patients were censored at the time of last follow-up prior to data lock, which occurred on June 30, 2023. Results Among 152 infused, the median age was 46 (range, 18-81), 57% were male, and 34% were Hispanic. Most (67%) had Ph- ALL, were heavily pre-treated (median 4 prior lines), and entered apheresis with high disease burden (57%). At time of apheresis, 23% of patients only had MRD+ disease and 15% were in complete molecular remission. While 82% developed CRS, the majority was grade 1-2, with 9% of the overall cohort experiencing grade 3-4 CRS. In contrast, 55% developed ICANS, with 32% of the entire cohort experiencing grade 3-4 ICANS. Eight patients (5%) died of toxicity/infection prior to D+28 response assessment. Among 133 patients with response assessment, 120 (90%) achieved morphologic CR, of whom 82% were MRD-, 15% were MRD+, and 3% MRD unknown. The median follow-up for survivors was 8.4 months; 45 patients have relapsed and 42 patients died. Median DOR was not reached. Median PFS and OS were 8.6 months and 15.6 months, respectively. Estimated PFS and OS of the entire cohort at 6-months were 61% (95% CI, 52-68) and 81% (95% CI, 73-87) and at 12-months were 47% (95% CI, 37-56) and 63% (95% CI, 53-72), respectively. We found no association between pre-CAR disease burden and post-CAR PFS/OS. However, patients with MRD- response to CAR had superior PFS relative to patients with MRD+ CR (median 14 months vs. 5 months, P=0.002). Forty-four patients received post-CAR consolidation/maintenance therapy while in CR: 25 allogeneic HCT, 15 TKI, 2 POMP, and 3 other/unknown. To examine the effect of consolidation/maintenance following brexu-cel, we performed a landmark analysis of PFS limited to patients alive and in CR at 2-months post-CAR infusion (N=113) and suggests superior PFS in patients receiving either HCT or other forms maintenance, relative to those receiving no further therapy following brexu-cel ( P=0.055). We then investigated post-CAR MRD-response in combination with receipt of post-CAR consolidation/maintenance and found that even among patients achieving MRD-negative response, post-CAR consolidation/maintenance led to superior PFS (Figure 1). Conclusions Among 152 adults treated with commercial brexu-cel for r/r B-ALL across 25 U.S. institutions, we found very high response rates (CR/CRi: 90%; 82% MRD-) consistent with the Zuma-3 data. While rates of severe CRS are low, grade 3-4 ICANS was observed in 32% of patients and warrants further investigation We demonstrate the prognostic impact of achieving an MRD-negative CR and an emerging role for consolidation/maintenance therapies to enhance the durability of response following brexu-cel in adults r/r B-ALL.

Background Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR-T) cell therapy that recently received U.S. FDA approval as the first CAR-T cell therapy for adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). Social determinants of health (SDoH) are shown to significantly influence outcomes in B-ALL. However, how SDoH relate to and affect outcomes in patients with B-ALL receiving CAR-T therapy has not been well established. We studied the impact of SDoH on outcomes of adults with B-ALL receiving brexu-cel as part of the Real-world Outcomes Collaborative of CAR-T in Adult ALL (ROCCA). Methods This retrospective multicenter analysis spanning 25 U.S centers included adults (≥18 years) with r/r B-ALL treated with commercial brexu-cel between 2021-2023. Progression-free survival (PFS) and overall survival (OS) were calculated from the day of brexu-cel infusion and were not censored for hematopoietic cell transplant (HCT) or maintenance. Univariate and multivariate Cox proportional hazards models were used to evaluate the association of age, sex, pre-apheresis disease burden, and SDoH (referral source, insurance, distance from home to CAR-T site, marital status, and the social deprivation index) with progression-free survival (PFS) and overall survival (OS). The social deprivation index (SDI), a composite measure (including income, education, employment, housing, household characteristics, and transportation) used to quantify socio-economic variation in health outcomes, with higher SDI indicating greater social disadvantage, was estimated at the zip code level. (Butler et al., 2013) Results Of the 152 patients who received brexu-cel (Table 1), 57% were male. 51% identified as non-Hispanic White, with the remainder identifying as Hispanic (34%), Asian/Pacific Islander (7%), Black (6%), American Indian/Alaskan Native (1%), or mixed race (1%). A majority (46%) were referred for brexu-cel from private/community-based practices and 62% lived within 50 miles of the CAR-T center (36% lived >50 miles and 2% were unknown). Health insurance coverage included primarily public (49%) and private (42%); no patients were uninsured. High SDI (76-100% percentile) was present in 26%, while 14% had a low SDI (0-25 th percentile). In unadjusted analyses, there was no difference in PFS or OS between patients with high versus low SDI; closer distance to the CAR-T site (<50 miles versus >50 miles)) was associated with worse OS (HR 1.96; 95% CI 1.00, 3.84; p=0.05). Multivariate analysis (Table 2) revealed that male sex was associated with inferior PFS (HR 1.98; 95% CI 1.02, 3.85; p=0.04) and OS (HR 2.52; 95% CI 1.09, 5.84; p=0.03). There was no difference in PFS (HR 0.95, 95% CI 0.48-1.88, p=0.88) or OS (HR 0.80; 95% CI 0.33,1.92; p=0.62) when comparing Hispanic and non-Hispanic White patients. Additionally, there was no difference in PFS or OS based on any SDoH, including insurance type, marital status, referral source, caregiver type, and distance to transplant center. Conclusions In patients receiving brexu-cel, survival outcomes appear independent of SDoH. Contrary to previous reports suggesting inferior outcomes for Hispanic patients with B-ALL after receiving traditional systemic therapies, we observed comparable outcomes to non-Hispanic patients treated with brexu-cel. Distance from the CAR-T site and referrals from the community did not affect outcomes. Additionally, those with higher SDI had similar outcomes to those with a lower SDI, although this analysis was limited by sample size and the selection bias that exists in being referred for brexu-cel in the first place. The relatively lower logistical burden of CAR-T compared to allogeneic stem cell transplant or non-fixed duration systemic therapies may have mitigated the impact of SDoH on outcomes. These real-world data suggest that continuing to improve access to and treatment with brexu-cel may improve overall outcomes for disadvantaged populations with r/r B-ALL.

Background : Most older patients (pts) with relapsed or refractory (R/R) AML cannot tolerate intensive treatment and are not eligible for curative allogeneic hematopoietic cell transplant (alloHCT). 131I-apamistamab, an anti-CD45 radioimmunoconjugate, delivers high dose targeted radiation to hematopoietic cells, allowing for myeloablation and eradication of leukemic cells while sparing toxicity to healthy organs. 131I-apamistamab led induction and conditioning can thus provide these pts with access to alloHCT. Methods: The SIERRA trial (NCT02665065) is a multi-center, randomized, controlled Phase 3 study comparing the rate of durable complete remission (dCR) lasting >6 months (mos) after complete remission with/without platelet recovery (CR/CRp) between two groups: 131I-apamistamab led induction and conditioning followed by alloHCT vs physician's choice of conventional care (CC). Pts were randomized (1:1) to CC or 131I-apamistamab with fludarabine and total body irradiation (2 Gy) followed by alloHCT. CR/CRp assessment was 28-56 days post alloHCT or 28-42 days post initiation of therapy on the CC group. Pts in the CC group not achieving leukemia-free state could crossover (CO) to 131I-apamistamab. Here we report the results of a post hoc analysis to determine if the presence of various risk factors (i.e., Karnofsky Performance Status (KPS) <90, HCT Comorbidity Index >3, age >65, adverse-risk cytogenetics, venetoclax failure prior to randomization) influenced achievement of dCR in pts treated with 131I-apamistamab. Results: In total, 153 pts were randomized (CC, n=76; 131I-apamistamab, n=77). All pts who received the therapeutic dose of 131I-apamistamab (n=66) underwent alloHCT vs 14 (18.2%) in the CC group. Of evaluable pts, dCR rates at 6 mos were 22% in the 131I-apamistamab group vs 0% in the CC group (95% CI;12.29, 34.73; p<0.0001). A total of 19 pts (13, 131I-apamistamab group; 6, CO) achieved dCR. Table 1 shows the pt, disease, and transplant characteristics of dCR vs. non-dCR pts. Eight of the 19 pts (42.1%) had primary induction failure and the median time to randomization from diagnosis was 5.4 mos. Approximately 50% of pts (9/19) had adverse-risk cytogenetics. Over 35% (7/19) of the pts had failed prior venetoclax and the median number of prior treatments was 3 (range 1-5). A total of 10/19 (52%) pts had KPS of <90% and a comorbidity index of >3. There was no difference in the rate of dCR when stratifying by number of risk factors for a given pt (0 to 5) with 27% for pts with 0-1 risk factors, 14% for pts with 2-3 risk factors, and 11% for pts with 4-5 risk factors (p=0.251). Conclusion: Pts with R/R AML who have multiple risk factors such as adverse risk cytogenetics, age >65, venetoclax failure, high comorbidity index or poor KPS are typically not considered for alloHCT due to high transplant-related mortality and post-transplant relapse rates. 131I-apamistamab was effective in achieving durable responses in R/R AML pts irrespective of the presence of multiple risk factors and successfully enabled alloHCT in such pts due to its targeted mechanism of action.

Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for adults with relapsed or refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). Blinatumomab is a CD19-directed bispecific T-cell engager that is also approved for r/r B-ALL, and often used as early salvage therapy. Data in the pediatric/AYA population suggest that patients who did not respond to blinatumomab may have inferior outcomes to CD19-directed CAR-T products compared to those who have achieved a response to blinatumomab or were blinatumomab-naïve (Myers et al. J Clin Oncol 2022). In this study, we evaluate the response to blinatumomab and subsequent response to brexu-cel in adults with r/r B-ALL. Methods: Retrospective data were collected from 25 centers across the U.S. as part of the real-world outcomes collaborative study of CAR-T in B-ALL (ROCCA). Consecutive patients treated with brexu-cel from 2021 to 2023 were categorized by blinatumomab exposure status. Those exposed were separated into “blinatumomab responders” (B-R), defined as patients achieving a CR/CRi in response to any number of cycles of blinatumomab, and “non-responders” (B-NR). Each cohort was compared for outcomes of interest. The primary outcome was CR/CRi rate at day 28 following brexu-cel administration. Secondary outcomes were duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Survival outcomes were calculated from day of brexu-cel infusion and were not censored for allogeneic hematopoietic cell transplantation or maintenance therapy. All living patients were censored at data cutoff on June 30, 2023. Survival comparisons were made by log rank test. Results: Among 152 patients who received brexu-cel, the median follow-up time was 8.4 months. Eighty-eight (57%) of 152 r/r B-ALL brexu-cel recipients had received blinatumomab prior to apheresis. The median number of pre-apheresis blinatumomab cycles was 2 (range 1-12). The baseline characteristics of B-R, B-NR, and blinatumomab-naïve (B-NV) patients were similar, including pre-apheresis disease burden and receipt of maintenance therapy following brexu-cel infusion (Table 1). Seventy percent (N= 62) of the blinatumomab-exposed patients were B-R, while 30% (N=26) were B-NR. Rates of CR/CRi at day 28 following brexu-cel infusion were similar between B-R, B-NR, and B-NV patients (79% vs 84% vs 78%, respectively). Most of these remissions were negative for measurable residual disease (MRD), with similar MRD negativity rates in the three groups (table 2). 1-year DOR and PFS were significantly higher in the B-NV group compared to B-R or B-NR (77% vs 49% vs 50%, p<.0001; 60% vs 37% vs 30%, p<.0001). B-NV and B-R had better 1-year survival compared to B-NR (71% vs 65% vs 32%, p<.0001). There were more CD19-negative relapses following brexu-cel in B-NR (29%) and B-R (18%) compared to B-NV patients (8%), although this was not statistically significant. Conclusions: Brexu-cel induced deep responses in a majority of adults with r/r B-ALL, irrespective of prior exposure or response to blinatumomab. Similar to data published by the pediatric CAR-T cell groups, our data draw speculation that adult patients who did not respond to blinatumomab experience shorter overall survival following brexu-cel compared to those who responded to or did not receive blinatumomab. This should be confirmed in a larger, prospective clinical trial. Because this analysis could not account for patients who achieved durable remission after blinatumomab, these differences may not reflect superiority of sequencing brexu-cel before blinatumomab. The higher number of CD19-negative relapses in the blinatumomab-exposed cohort add to the interest in pursuing strategies to address antigen escape following CAR-T cell therapy directed against a previously targeted antigen.