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4845 Risk Factors Associated with Sub-Optimal Outcomes Following Obecabtagene autoleucel (obe-cel) for Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia (R/R B-ALL): What We Have Learned from the FELIX Trial

Program: Oral and Poster Abstracts
Session: 704. Cellular Immunotherapies: Early Phase Clinical Trials and Toxicities: Poster III
Hematology Disease Topics & Pathways:
Clinical trials, ALL, Adult, Chimeric Antigen Receptor (CAR)-T Cell Therapies
Monday, December 9, 2024, 6:00 PM-8:00 PM

Claire Roddie, MD1*, Jae H. Park, MD2, Paul Shaughnessy, MD3, Aaron C. Logan, MD, PhD4, Karamjeet S Sandhu, MD5, Mehrdad Abedi, MD6*, Bijal D Shah, MD7, Michael R Bishop, MD8*, Daniel J. DeAngelo, MD, PhD9, Wolfram Brugger, MD10*, Martin A Pule, MD11*, Justin Shang, PhD12* and Elias Jabbour, MD13

1University College London Cancer Institute, London, United Kingdom
2Memorial Sloan Kettering Cancer Center, New York, NY
3Sarah Cannon Transplant and Cellular Therapy Program, Methodist Hospital, San Antonio, TX
4Hematology, Blood and Marrow Transplantation, and Cellular Therapy Program, University of California at San Francisco, San Francisco, CA
5City of Hope National Medical Center, Duarte, CA
6University of California Davis, Davis, CA
7Moffitt Cancer Center, Tampa, FL
8The David and Etta Jonas Center for Cellular Therapy, University of Chicago, Chicago, IL
9Dana-Farber Cancer Institute, Boston, MA
10Autolus Therapeutics, Munich, Germany
11Autolus Therapeutics, London, United Kingdom
12Autolus Therapeutics, Rockville, MD
13University of Texas MD Anderson Cancer Center, Houston, TX

Background: Obe-cel, an anti-CD19 autologous CAR T with a fast off-rate CD19 binding domain to improve persistence/reduce toxicity, is being investigated for the treatment of adult R/R B-ALL. Immune effector cell-associated hematotoxicity is the most common side effect of CAR T therapy but the pathophysiology of prolonged hematotoxicity is poorly understood and the lack of consensus for its treatment presents challenges. The CAR-HEMATOTOX (HT) model was developed in large B-cell lymphoma for risk-stratifying patients (pts) prior to CAR T therapy for hematotoxicity and outcomes. Here, we report an analysis exploring outcomes for pts with R/R B-ALL, risk-stratified using the HT model.

Methods: FELIX (NCT04404660) is a Phase Ib/II study evaluating the efficacy and safety of obe-cel in adult pts (≥18 yrs) with R/R B-ALL. Pts received bridging therapy as appropriate and underwent lymphodepletion (LD; fludarabine, 4×30mg/m2; cyclophosphamide, 2×500mg/m2), followed by tumor burden-guided infusions on Days 1 and 10 to a target dose of 410×106 CAR T-cells. HT scores were calculated using the HT model (Rejeski K, et al. Blood 2023;142[10]:865–77); parameters comprise pre-LD platelet count, absolute neutrophil count, hemoglobin, and inflammatory parameters (C-reactive protein [CRP] and ferritin). The score discriminates between low-risk (0–1) and high-risk (≥2) of hematotoxicity. Associations between hematotoxicity risk, immunotoxicity risk, and outcomes were assessed (data cut-off: 7 February 2024).

Results: In FELIX, most pts infused with obe-cel were high-risk (102/127 [80%]), while 25/127 (20%) pts were low-risk or unknown. Baseline characteristics were generally similar across the two groups but a higher proportion of pts were male in the low-risk group vs the high-risk group (72% vs 47%), with increased rates of pre-treatment in low-risk pts vs high-risk pts: ≥3 prior therapies (48% vs 32%); previous allo-stem cell transplant (allo-SCT; 56% vs 41%), and previous inotuzumab ozogamicin or blinatumomab (80% vs 51%). Median bone marrow blasts at LD were increased in high-risk pts (45.5%, range: 5.0–90.0) vs low-risk pts (7.0%, range: 2.0–38.0), representing greater disease burden. Overall remission rate was numerically lower for high-risk pts (73.5%, 95% confidence interval [CI]: 63.9, 81.8) vs low-risk pts (96.0%, 95% CI: 79.6, 99.9). High-risk pts experienced worse survival outcomes, with median event-free survival (EFS; 95% CI) 9.0 months (5.8, 15.1) vs not estimable (NE) and median overall survival (OS; 95% CI) 14.1 months (10.7, 17.1) vs NE for high- and low-risk pts, respectively. Additionally, 12-month EFS (95% CI) and OS (95% CI) rates were 45.4% (34.6, 55.6) vs 65.5% (40.2, 82.1) and 57.6% (47.4, 66.5) vs 75.0% (52.6, 88.0) for high- and low-risk pts, respectively. Median duration of remission (95% CI) was 14.2 months (8.2, NE) vs NE for high- and low-risk pts, respectively. While in remission, 17% of high-risk pts and 21% of low-risk pts proceeded to allo-SCT. Rates of any-grade cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were increased in high-risk pts vs low-risk pts (72% vs 56% and 25% vs 12%); however, rates of Grade ≥3 CRS and ICANS were comparable (3% vs 0% and 7% vs 8%). High-risk pts experienced slightly prolonged CRS vs low-risk pts (median [range]: 6.0 days [1.0–21.0] vs 4.0 days [1.0–6.0]), while duration of ICANS was comparable (median [range]: 8.5 days [1.0–53.0] vs 8.0 days [5.0–8.0]). Among responders, rates of Grade ≥3 infections within 3 months post-infusion were higher in high- vs low-risk pts (27% vs 13%), reflecting their underlying baseline and disease characteristics. Time to recovery of neutrophil (1×109) and platelet (100×109) counts was longer in high- vs low-risk pts (median [95% CI]: 1.9 months [1.5, 2.0] vs 0.8 months [0.7, 1.9] and 2.1 months [1.9, 2.3] vs 0.6 months [0.0, 1.9], respectively).

Conclusions: The HT score was found to be correlated with disease burden. Risk-stratification for hematotoxicity, using pre-LD clinical parameters together with disease burden, has the potential to be a useful tool for identifying pts more likely to benefit from obe-cel treatment and experience reduced toxicity. Pts with high-risk HT scores had consistently worse outcomes than pts with low-risk HT scores. Further studies are warranted.

Disclosures: Roddie: Autolus, BMS, Gilead, Janssen: Consultancy; Autolus, BMS, Gilead: Honoraria, Speakers Bureau. Park: Adaptive Biotechnologies, Affyimmune, Allogene, Amgen, Artiva Biotherapeutics, Autolus, Bright Pharmaceutical Services, BMS, Caribou Biosciences, Curocell, Galapagos, Gilead Sciences, Intellia, In8Bio, Kite, Novartis, Pfizer, Servier, Sobi, Synthekine: Consultancy; Curocell: Current equity holder in publicly-traded company; Autolus, Fate Therapeutics, Genentech, InCyte, Servier, Sobi, Takeda (Institution): Research Funding; Takeda: Consultancy. Shaughnessy: Autolus, Sanofi: Consultancy; Sanofi: Speakers Bureau; BMS: Speakers Bureau. Logan: Kadmon/Sanofi: Research Funding; Pfizer: Consultancy; Kite/Gilead: Research Funding; Amgen: Consultancy, Research Funding; Autolus: Research Funding; Talaris: Research Funding; Pharmacyclics: Research Funding; Astellas Pharma: Research Funding; AbbVie: Consultancy; Actinium: Consultancy; Bristol Myers Squibb: Consultancy; Sanofi: Consultancy; Takeda: Consultancy; Kite: Consultancy. Sandhu: Autolus: Consultancy. Abedi: AbbVie, BMS and Gilead Sciences: Speakers Bureau; Autolus, BMS and Gilead Sciences: Research Funding; Orca Bio: Research Funding; BMS, Autolus: Consultancy; CytoDyn: Current holder of stock options in a privately-held company. Shah: Eli Lilly: Consultancy; Kite Pharma: Consultancy; Autolus, Beigene, Century Therapeutics, Deciphera, Jazz, Kite/Gilead, Pfizer, Precision Biosciences, Novartis, Takeda: Consultancy; Jazz Pharmaceuticals, Kite-Gilead, Servier: Research Funding; Pepromene Bio: Other: DSMB; Bristol Myers Squibb: Consultancy; Jazz Pharmaceuticals: Consultancy; Adaptive Biotechnologies: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy. Bishop: Achieve Clinics, Arcellx, Autolus, BMS, Chimeric Therapeutics, CRISPR Therapeutics, In8Bio, Iovance Biotherapeutics, Kite-Gilead, Optum Health, Novartis, Sana Biotechnology: Consultancy; Achieve Clinics, In8Bio: Current holder of stock options in a privately-held company; Arcellx, Autolus, Bristol-Myers Squibb, CRISPR Therapeutics, Lyell, Gilead Sciences and Novartis: Research Funding; AbbVie, ADC Therapeutics, Bristol-Myers Squibb, Gilead Sciences, Incyte, Novartis, Sanofi and Servier: Honoraria, Speakers Bureau. DeAngelo: Daiichi-Sankyo, Fibrogen: Other: DSMB; Mt Sinai MPN Consortium: Other: Mt Sinai MPN Consortium; AbbVie, Blueprint, GlycoMimetics, Novartis: Research Funding; Dana-Farber Cancer Institute: Current Employment; Amgen, Autolus, Blueprint, Gilead, Incyte, Jazz, Novartis, Pfizer, Servier, Takeda: Consultancy. Brugger: Autolus: Current Employment, Current equity holder in publicly-traded company. Pule: Autolus: Current Employment, Current equity holder in publicly-traded company; Autolus: Other: Entitled to royalty payments from related intellectual property. Shang: Autolus: Current Employment, Current equity holder in publicly-traded company. Jabbour: AbbVie, Adaptive Biotechnologies, Amgen, Ascentage Pharma Group, Pfizer, Takeda: Research Funding; AbbVie, Adaptive Biotechnologies, Amgen, Astellas Pharma, BMS, Genentech, Incyte, Pfizer, Takeda: Consultancy.

*signifies non-member of ASH