Phase Ib/II FELIX trial post hoc analysis: Obe-cel in R/R B-ALL stratified by morphologic remission status

Results from a post hoc analysis of the phase Ib/II FELIX (NCT04404660) trial, evaluating obecabtagene autoleucel (obe-cel) in 127 patients with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) in morphologic remission (<5% bone marrow [BM] blasts), were presented by Claire Roddie at the European Hematology Association (EHA) 2026 Congress, June 11–14, 2026, Stockholm, SE. Patients were stratified by morphologic remission status at screening (in remission [Y]; no remission [N]) and at lymphodepletion following bridging therapy into those who remained in remission (Y/Y, 7.9%), went into remission (N/Y, 20.5%), came out of remission (Y/N, 7.1%), and remained with no remission (N/N, 64.6%). The primary endpoint was overall remission rate (ORR), including complete remission (CR) and CR with incomplete hematologic recovery (CRi), per independent response review committee (IRRC). 

Key data: In the Y/Y group, 10% of patients received no bridging therapy vs 22.2% of patients in the Y/N group. In the N/N group, 74.4% of patients received chemotherapy bridging vs 30.8% of patients in the N/Y group. Patients in the Y/N vs Y/Y (22.2% vs 10.0%) and N/N vs N/Y (51.2% vs 26.9%) groups were more likely to experience treatment failure or relapse. Median event-free survival (EFS) and overall survival (OS) were not estimable (NE) in the Y/Y, Y/N, and N/Y groups and were 9.0 months and 13.5 months, respectively, in the N/N group. Grade ≥3 cytokine release syndrome (CRS) occurred in 3.7% of patients in the N/N group only, and Grade ≥3 immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 11.1% and 9.8% of patients in the Y/N and N/N groups, respectively. 

Key learning: Obe-cel achieved clinically relevant responses in patients with R/R B-ALL, regardless of morphologic remission status at screening or at lymphodepletion, with the greatest efficacy and safety benefit observed in patients in morphological remission, supporting the use of obe-cel in patients with low BM blast percentage, including those in morphologic remission.