The FDA has granted approval to obecabtagene autoleucel (Aucatzyl; Autolus Inc.) for the treatment of adult patients with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL). This CD19-directed, genetically modified autologous T-cell immunotherapy offers a new treatment option for patients facing this challenging disease. The approval was based on the results of the pivotal FELIX trial (NCT04404660).
Efficacy Demonstrated in FELIX Trial
The FELIX trial, an open-label, multicenter, single-arm study, evaluated the safety and efficacy of obecabtagene autoleucel in adult patients with relapsed or refractory CD19-positive B-cell ALL. To be eligible, patients needed to have relapsed following a remission lasting 12 months or less, have relapsed or refractory ALL after two or more lines of systemic therapy, or have disease that was relapsed or refractory 3 or more months after allogeneic stem cell transplantation.
The primary endpoint of the trial was the rate of complete remission (CR) achieved within 3 months following infusion. Secondary endpoints included the duration of response, measurable residual disease (MRD) negativity rate, and safety. Patients underwent several stages: screening, leukapheresis, pre-conditioning, treatment, and follow-up.
Of the 65 patients evaluable for efficacy, 27 (42%; 95% CI, 29%-54%) achieved CR within 3 months. The median duration of CR achieved within 3 months was 14.1 months (95% CI, 6.1-not reached).
Safety Profile and Adverse Events
The prescribing information for obecabtagene autoleucel includes a boxed warning for cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and T-cell malignancies. In the full study population, CRS occurred in 75% of participants, with neurological toxicities occurring in 64%, including ICANS in 24%.
Common non-laboratory adverse reactions (incidence ≥ 20%) included CRS, infections (pathogen unspecified), musculoskeletal pain, viral infections, fever, nausea, bacterial infectious disorders, diarrhea, febrile neutropenia, ICANS, hypotension, pain, fatigue, headache, and hemorrhage.
Dosing and Administration
The recommended dose of obecabtagene autoleucel is 410 x 106 CD19 chimeric antigen receptor (CAR)-positive viable T cells, administered as a split dose infusion on Day 1 and Day 10 (±2 days). The dosing is based on bone marrow blast assessment and follows fludarabine and cyclophosphamide lymphodepleting chemotherapy.
Autolus Therapeutics at Tandem Meetings 2025
Autolus Therapeutics is presenting clinical data updates at the 2025 Tandem Meetings, showcasing the potential benefits of obecabtagene autoleucel. An economic model comparing costs associated with CRS and ICANS among patients treated with CAR T-cell therapies for relapsed/refractory B-ALL suggests that obecabtagene autoleucel is associated with lower healthcare costs compared to brexu-cel, primarily due to lower rates of Grade 3/4 adverse events and faster resolution.
Additionally, data comparing obecabtagene autoleucel to an external control arm (ECA) in adult patients with relapsed/refractory B-ALL demonstrated higher overall response rate (ORR) and longer overall survival (OS) and event-free survival (EFS) compared to standard of care therapies in matched ECAs. Safety was comparable between treatment groups, demonstrating a positive benefit-risk profile.
Further research indicates that achieving deep molecular remission (MRD <10-6 leukemic cells) is associated with more durable responses and higher EFS and OS rates in patients treated with obecabtagene autoleucel.
