Blunk, Betsy

PURPOSE On the basis of the results of the ZUMA-3 trial, brexucabtagene autoleucel (brexu-cel), a CD19-directed chimeric antigen receptor T-cell therapy, gained US Food and Drug Administration approval in October 2021 for adults with relapsed/refractory (R/R) B-cell ALL (B-ALL). We report outcomes of patients treated with brexu-cel as a standard therapy. METHODS We developed a collaboration across 31 US centers to study adults with B-ALL who received brexu-cel outside the context of a clinical trial. Data were collected retrospectively from October 2021 to October 2023. Toxicities were graded per American Society for Transplantation and Cellular Therapy guidelines for cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS). RESULTS At the time of data lock, 204 patients had undergone apheresis and 189 were infused. Median follow-up time was 11.4 months. Forty-two percent of patients received brexu-cel in morphologic remission and would have been ineligible for participation in ZUMA-3. After brexu-cel, 151 achieved complete remission (CR), of which 79% were measurable residual disease (MRD) negative remissions. Median progression-free survival (PFS) was 9.5 months and median overall survival was not reached. Grade 3-4 CRS or ICANS occurred in 11% and 31%, respectively. In multivariable analysis, patients receiving consolidative hematopoietic cell transplantation (HCT; hazard ratio, 0.34 [95% CI, 0.14 to 0.85]) after brexu-cel had superior PFS compared with those who did not receive any consolidation or maintenance therapy. CONCLUSION Similar to ZUMA-3, high rates of MRD-negative CR were observed after brexu-cel treatment for R/R B-ALL. The use of HCT as consolidation after brexu-cel resulted in improved PFS.

Abstract The effect of prior inotuzumab ozogamicin (InO) treatment on brexucabtagene autoleucel (brexu-cel) outcomes remains unclear in adults with acute lymphoblastic leukemia (ALL). We conducted a retrospective multicenter analysis of 189 patients with relapsed/refractory ALL treated with brexu-cel. Over half of the patients received InO before brexu-cel (InO exposed). InO-exposed patients were more heavily pretreated (P = .02) and frequently had active marrow disease before apheresis (P = .03). Response rate and toxicity profile after brexu-cel were comparable for InO-exposed and InO-naïve patients; however, consolidation therapy after brexu-cel response was used at a higher rate in InO-naïve patients (P = .005). With a median follow-up of 11.4 months, InO-exposed patients had inferior progression-free survival (PFS; P = .013) and overall survival (OS; P = .006) in univariate analyses; however, prior InO exposure did not influence PFS (hazard ratio, 1.20; 95% confidence interval, 0.71-2.03) in multivariate models. Within InO-exposed patients, InO responders had superior PFS (P = .002) and OS (P < .0001) relative to InO-refractory patients. The timing of administering InO did not affect brexu-cel outcomes, with comparable PFS (P = .51) and OS (P = .86) for patients receiving InO as bridging therapy or before apheresis. In conclusion, although InO exposure was associated with inferior survival outcomes after brexu-cel in unadjusted analyses, these associations were no longer significant in multivariate analyses, suggesting it is unlikely that InO negatively affects brexu-cel efficacy. Our data instead imply that InO-exposed recipients of brexu-cel tend to be higher-risk patients with intrinsic adverse leukemia biology.

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.

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.

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.

Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy approved for adults with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL). Bridging therapy, defined as anti-leukemia therapy given between apheresis and lymphodepleting chemotherapy, was permitted on the pivotal ZUMA-3 trial. The optimal bridging therapy is unknown in this setting. Here we report patient and disease characteristics in those receiving bridging therapies prior to brexu-cel and the impact of bridging on clinical outcomes in a large multicenter cohort. Methods and Results: ROCCA includes 25 US institutions contributing retrospective data from 152 B-ALL patients treated with standard of care brexu-cel between 2021-2023. Ninety-nine patients (65%) received bridging therapy, while 53 patients (35%) received no bridging therapy. Bridging therapy consisted of cytotoxic chemotherapy ( n=65, 66%), immunotherapy ( n=26, 26%; 23 inotuzumab, 3 blinatumomab), tyrosine kinase inhibitors (TKI) ( n=20, 20%; 16 ponatinib), steroids only ( n=10, 10%), and intrathecal chemotherapy ( n=22, 22%). The median age of the cohort was 46 (IQR 32-61). Patients were heavily pre-treated with a median of 4 prior lines of therapy. The median days from apheresis to infusion was 33 (IQR 26-42). 119 patients had known pre-apheresis blast counts; the bridging group had higher pre-apheresis blast burden, with 21 of 76 patients (28%) having ≥ 50% blasts compared to only 5 of 43 patients (12%) in the no bridging group ( p=0.02). In addition, more patients who received bridging had pre-apheresis extramedullary disease (32% vs. 15%, p=0.02). All other baseline characteristics were similar between the two groups (Table 1). Fifty-four (54%) patients had response assessment after bridging therapy and prior to brexu-cel infusion. In patients who received inotuzumab for pre-apheresis active disease, defined as ≥ 5% blasts, 6 of 13 (46%) who had post-bridging assessment achieved a complete response (CR; 5 measurable residual disease (MRD)+, 1 MRD-), with a mean proportional reduction in blast burden of 46% from baseline. In contrast, after chemotherapy bridging, only 2 of 16 patients (13%) with pre-apheresis active disease had a CR. Patients receiving chemotherapy bridging had a mean proportional increase in blast burden of 4.4%. In recipients of TKI bridging, 2 of 4 patients (50%) with pre-apheresis active disease had a CR. Compared to no bridging, patients in the bridging group had similar rates of grade 3 or 4 CRS (9% bridging vs. 8% no bridging, p=0.73) and grade 3 or 4 ICANS (34% vs. 26%, p=0.32). In univariate analysis, there was no statistically significant difference in day 28 response with 63 patients (72%) achieving MRD- complete response in the bridging group as compared to 36 patients (78%) in the no bridging group ( p=0.60). Non-relapse mortality was similar between the two groups (17% bridging vs. 9% no bridging, p=0.20). Overall survival (OS) and progression-free survival (PFS) were superior in the no bridging group: 1-year OS 74.7% vs 56.8% (log-rank p=0.04), and 1-year PFS 57.3% vs 41.7% (log-rank p=0.04). In a multivariate analysis stratified by bridging and pre-apheresis disease burden, patients with pre-apheresis blasts ≥ 5% and bridging had worse survival than ≥ 5% blasts and no bridging: 1-year OS 45.3% vs. 87.5% and 1-year PFS 27.7% vs. 64.3% (Figure 1). However, patients with < 5% blasts had similar survival regardless of bridging. Conclusions: In our real-world analysis, adults with R/R B-ALL receiving bridging therapy had a higher disease burden at baseline. Despite greater baseline disease, there were no significant differences in toxicity and day 28 response in those receiving bridging therapy vs. not. While survival was inferior in patients with pre-apheresis active disease who received bridging, this may be confounded by the degree of tumor burden. In patients with < 5% blasts pre-apheresis, bridging did not impact survival. Furthermore, inotuzumab bridging demonstrated the most significant disease debulking. However, the comparisons in this study are limited by the variability in practice for post-bridging disease reassessment and the small proportion of patients with active disease who did not receive bridging. A more uniform approach to peri-CAR disease assessment would enable more robust study of optimal bridging strategies.