Obecabtagene autoleucel (obe-cel) for relapsed/​refractory B-ALL: The FELIX study

During the ALL Hub Steering Committee meeting in April 2026, Daniel DeAngelo chaired a discussion on the latest findings from the phase Ib/II FELIX trial (NCT04404660) investigating 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).¹ The discussion featured contributions from Ibrahim Aldoss, José María Ribera, André Baruchel, Wendy Stock and Nicolas Boissel.

In his presentation, DeAngelo outlined the currently approved CD19-directed CAR T-cell therapies for the treatment of B-ALL, including obe-cel and brexucabtagene autoleucel (brexu-cel) for adults with R/R B-ALL, and tisagenlecleucel (tisa-cel) for paediatric and young adult patients with R/R B-ALL.^2–7 He then discussed the key findings from the phase Ib/II FELIX trial (Figure 1), including long-term outcomes and predictors of response to obe-cel, in adults with R/R CD19-positive B-ALL (Figure 2).^1,8-10

Key points  

• The FELIX trial demonstrated that obe-cel produces high remission rates, durable responses, and a favourable safety profile in patients with R/R B-ALL, with outcomes linked to lower disease burden at lymphodepletion and sustained CAR T-cell persistence.¹  
• After a median follow-up of 32.8 months (range, 19.9–52.8 months), 38.4% of responders remained in remission without stem cell transplant or other non-protocol specified therapies.⁹ 
  • These findings suggest that some patients may not require additional therapy; however, longer follow-up, further analyses, and independent validation are needed to confirm these results.⁹ 
• Lower disease burden at lymphodepletion and ongoing CAR T-cell persistence were independent factors associated with long-term remission and survival. 
  • Patients with ≤20% bone marrow blasts had an overall response rate of 85%, compared with 73% in patients with >20% bone marrow blasts. ⁹ 
  • Patients with ongoing CAR T-cell persistence had a prolonged predicted event-free survival compared with patients with a loss of CAR T-cell persistence at Month 12 or at Month 6.⁸ 
• Age did not appear to adversely affect outcomes, with comparable event-free survival and overall survival observed in patients aged <55 years and ≥55 years; rates of Grade ≥3 cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS remained low across age groups.¹¹ 
• Ongoing phase II clinical studies are investigating obe-cel in different ALL settings, including: 
  • As consolidation therapy for adults with newly diagnosed high-risk B-ALL (NCT07053059)¹² 
  • As consolidation therapy in adults with ALL in first complete remission without measurable residual disease (NCT07400029)¹³ 
  • In pediatric patients with R/R B-ALL (NCT06173518); preliminary findings from the phase Ib/II CATULUS study (NCT06173518) have shown promising efficacy and a favorable safety profile of obe-cel in pediatric patients with R/R B-ALL^14,15 
• Real-world data from the ROCCA consortium (40 North American centers) supported the findings from the FELIX trial, with high response rates that were similar between patients treated with brexu-cel (n = 53) and obe-cel (n = 36);¹⁶ real-world evidence is still accumulating following the relatively recent approval of obe-cel. 
• Despite the durable long-term responses observed with obe-cel, the role of stem cell transplant consolidation in patients with R/R ALL remains to be fully established. 
  • Current practice remains variable and the optimal sequencing of CAR T-cell therapy and allogeneic hematopoietic stem cell transplantation remains to be defined through longer-term, prospective data. 
• Additionally, there is currently uncertainty regarding the optimal intensity of pre-CAR T-cell cytoreduction in patients with high blast counts, reflecting a need to balance achieving deeper disease control against avoiding delays to CAR T-cell infusion. 
  • Data from the FELIX trial indicates that lower disease burden is associated with improved outcomes.⁸ 
• Furthermore, optimization of infection prophylaxis, monitoring, and management is required in patients undergoing CAR T-cell therapy, given the high infection risk associated with prior intensive therapies, bridging regimens, and prolonged cytopenias. 
• Overall, the FELIX study established obe-cel as an effective CD19-directed CAR T-cell therapy for adults with R/R B-ALL, demonstrating high remission rates, durable responses, low rates of severe CRS and ICANS, and encouraging long-term outcomes, particularly in patients with low disease burden and sustained CAR T-cell persistence. 

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