Results of Phase II FELIX Trial Lead to BLA Acceptance for Obe-Cel in B-ALL

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The FDA has accepted a biologics license application (BLA) from Autolus Therapeutics for the chimeric antigen receptor (CAR) T-cell therapy obecabtagene autoleucel (obe-cel) to treat adults with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). The FDA assigned the BLA with a Prescription Drug User Fee Act (PDUFA) date of November 16, 2024.¹

“Acceptance of the BLA filing is an important milestone for Autolus and we look forward to continuing our collaboration with the FDA during the review cycle,” said Christian Itin, PhD, CEO of Autolus Therapeutics, plc, in a news release.¹ “With the PDUFA date set for November, we remain focused on preparing for the potential launch of obe-cel.”

The application is supported by data from the Phase II FELIX trial (NCT04404660), in which the drug produced a complete response (CR) rate of 54.3% and a CR with incomplete count recovery (CRi) rate of 21.3% (n = 94).2 The CAR T-cell therapy produced an overall remission rate of 76% (95% CI, 66%-84%; P < .0001).

Investigators enrolled adults with relapsed or refractory adult B-ALL who had at least 5% bone marrow blasts at screening in cohort A, MRD positivity at screening in cohort B, and isolated extramedullary disease at screening in cohort C.^2,3 The trial’s primary endpoint was CR/CRi rate by central assessment, with secondary endpoints that included duration of response (DOR), event-free survival (EFS), overall survival, MRD negativity rate, and safety.

As of the data cutoff date of September 13, 2023, 153 patients were enrolled and 127 patients received infusion with obe-cel. Among these patients, 107 were assigned to cohort A, 13 were assigned to cohort B, and 7 were assigned to cohort C. A total of 26 patients discontinued treatment because of death (n = 15), issues related to manufacturing (n = 7), toxicity (n = 2), physician decision (n = 1), and disease progression (n = 1).

Data presented at the 2023 American Society of Hematology Annual Meeting indicated that obe-cel produced high CR/CRi rates across all patients subgroups.³ At a median follow-up of 16.6 months (range, 3.7-36.6), median EFS was 11.7 months (95% CI, 7.2-not evaluable [NE]) among patients administered treatment, the six-month EFS rate was 65% (95% CI, 56%-73%), and the 12-month EFS rate was 50% (95% CI, 39%-59%). Further, 17% of patients who responded to treatment went on to transplant while in remission.

In terms of safety, investigators reported low rates of grade 3 or higher CRS and/or ICANS. Among all patients, 69% experienced grade 1 or 2 CRS and 2% experienced CRS of grade 3 or higher.

Common treatment-emergent adverse effects experienced by 20% or more of patients administered obe-cel included pyrexia (any grade, 29%; grade ≥3, 2%), nausea (26%; 2%), diarrhea (25%; 2%), febrile neutropenia (24%; 24%), anemia (24%; 21%), headache (24%; 0%), neutropenia (23%; 21%), hypotension (22%; 5%), hypokalemia (21%; 6%), and decreased neutrophil count (20%; 20%).

References

1. Autolus Therapeutics announces acceptance of biologics license application for obecabtagene autoleucel (obe-cel) as a potential treatment for relapsed/refractory adult B-cell acute lymphoblastic leukemia (ALL). News release. January 22, 2024. Accessed January 24, 2024. https://autolus.gcs-web.com/news-releases/news-release-details/autolus-therapeutics-announces-acceptance-biologics-license
2. Roddie C, Sandhu KS, Tholouli E, et al. Safety and efficacy of obecabtagene autoleucel (obe-cel, AUTO1), a fast-off rate CD19 CAR, in relapsed/refractory adult B-cell acute lymphoblastic leukemia (r/r B-ALL): Top line results of the pivotal FELIX study. J Clin Oncol. 2023;41(suppl 16):7000. doi:10.1200/JCO.2023.41.16_suppl.7000
3. Roddie C, Sandhu KS, Tholouli E, et al. Obecabtagene autoleucel (obe-cel, AUTO1) for relapsed/refractory adult B-cell acute lymphoblastic leukemia (R/R B-ALL): pooled analysis of the ongoing FELIX phase Ib/II study. Blood. 2023;142(suppl_1):222. doi:10.1182/blood-2023-179454