FELIX phase Ib/II post hoc analysis: Obe-cel for R/R B-ALL with EMD

Results from a post hoc analysis of the phase Ib/II, open-label, multicenter, single-arm FELIX trial (NCT04404660), evaluating obecabtagene autoleucel (obe-cel), a CD19-directed chimeric antigen receptor (CAR) T-cell therapy, in adults with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) with (n = 27) or without (n = 100) extramedullary disease (EMD) at lymphodepletion (LD), were presented by Jae Park at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, May 29 – June 2, 2026, Chicago, US. The primary endpoint was overall remission rate (ORR) as assessed by an independent response review committee (IRRC). 

Key data: At a median follow-up of 32.8 months, the ORR was 59.3% in patients with EMD at LD vs 83.0% in those without EMD at LD. Among patients with <5% bone marrow (BM) blasts at LD, the ORR was 71.4% in those with EMD at LD vs 89.7% in those without EMD at LD. The median duration of remission (DoR) was 42.5 months in patients with EMD at LD vs not estimable (NE) in those without EMD at LD. The median event-free survival (EFS) was 4.5 months in patients with EMD at LD vs 14.3 months in those without EMD at LD, while the median overall survival (OS) was 15.3 months vs 21.0 months, respectively. In patients with <5% BM blasts, median DoR, EFS, and OS were NE regardless of EMD presence. Grade ≥3 cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 3.7% and 18.5% with EMD at LD vs 2.0% and 4.0% without EMD at LD, respectively; Grade ≥3 infections occurred in 48.1% with EMD at LD and 57.0% without EMD at LD. 

Key learning: Obe-cel demonstrated clinically meaningful activity in adults with R/R B-ALL and EMD at LD, particularly in those with <5% BM blasts, while maintaining low rates of severe CRS and ICANS in this subgroup. These findings support the potential role of obe-cel in this adverse-risk population with limited treatment options.