Safety and Efficacy of Obe-cel in Patients ≥55 Years with R/R B-ALL

Overview

In patients aged 55 years and older with relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL), obe-cel CAR T-cell therapy demonstrated a high overall remission rate of 87.5% with durable responses and a manageable safety profile. The incidence of severe cytokine release syndrome and neurotoxicity was low, supporting obe-cel's positive benefit-risk profile in this older patient population.

Background

Treatment options for patients aged 55 years and older with R/R B-ALL are limited due to poorer outcomes and toxicities associated with standard therapies like blinatumomab and inotuzumab ozogamicin. Additionally, many older patients are ineligible for potentially curative stem cell transplantation. CAR T-cell therapies targeting CD19, such as obe-cel, have shown promise but data in older adults remain scarce. This post-hoc analysis of the FELIX trial evaluates obe-cel's efficacy, safety, and persistence specifically in patients aged 55 and above.

Data Highlights

Median duration of remission: 21.2 months; Median event-free survival: 11.7 months; Median overall survival: 16.8 months; Median follow-up: 20.1 months.

Key Findings

• Overall remission rate (CR or CRi) in patients ≥55 years was 87.5% at median 20.1 months follow-up.
• High remission rates were observed in subgroups: 91.3% in Ph+ patients and 84.2% in those with prior stem cell transplantation.
• Median duration of remission was 21.2 months, with median event-free survival of 11.7 months and overall survival of 16.8 months.
• Grade ≥3 cytokine release syndrome occurred in 2.1% of patients; Grade ≥3 neurotoxicity (ICANS) occurred in 10.4%, with no severe events in patients with <5% bone marrow blasts at lymphodepletion.
• Severe infections were common (54.2%) regardless of remission status; treatment-related mortality within 3 months was 4.2%.
• CAR T-cell persistence median duration was not estimable, indicating durable cellular presence.

Clinical Implications

Obe-cel CAR T-cell therapy offers a highly effective treatment option with durable remissions for older adults with R/R B-ALL, a population with limited therapeutic alternatives. The low incidence of severe CRS and neurotoxicity supports its tolerability in this age group, including those with prior intensive therapies. Clinicians should monitor for infections and hematologic toxicities, but obe-cel represents a promising therapy for patients ≥55 years who are often ineligible for stem cell transplantation.

Conclusion

Obe-cel demonstrates a favorable efficacy and safety profile in patients aged 55 years and older with R/R B-ALL, achieving high remission rates and durable responses with manageable toxicity. These findings support its use as an effective treatment option in this challenging patient population.

References

1. Yallop et al. 2025 -- Safety, Efficacy and CAR T-cell Persistence of Obe-cel in Patients ≥55 Years with R/R B-ALL