The FDA has granted approval to obecabtagene autoleucel (obe-cel), also known as Aucatzyl, a CD19-directed CAR T-cell immunotherapy, for the treatment of adult patients with relapsed or refractory (r/r) B-cell precursor acute lymphoblastic leukemia (ALL). This approval marks a significant advancement for patients facing this aggressive cancer, where historical outcomes have been poor upon relapse. The decision was based on data from the pivotal phase 1b/2 FELIX clinical trial (NCT04404660).
The FELIX trial demonstrated compelling efficacy, with overall complete remission (CR) rates exceeding 60%. Furthermore, patients who achieved complete remission within three months exhibited a median duration of remission beyond 12 months. These results underscore the potential of obe-cel to provide durable responses in a challenging patient population.
The recommended dose of obe-cel is 410 × 106 CD19 chimeric antigen receptor (CAR)-positive viable T-cells. The treatment is preceded by lymphodepleting chemotherapy consisting of fludarabine and cyclophosphamide and is administered as a split-dose infusion on Day 1 and Day 10 (±2 days) of treatment, contingent on bone marrow blast assessment. Notably, the FDA did not require a Risk Evaluation and Mitigation Strategy (REMS) for this therapy.
Clinical Insights from Key Investigators
"Adult ALL is an extremely aggressive cancer, and there is a high unmet medical need that exists in the treatment of patients with this disease once they relapse, where historically they suffer from poor outcomes," stated Elias Jabbour, MD, lead investigator of the US-based portion of the FELIX study and a professor at The University of Texas MD Anderson Cancer Center. "This milestone approval, based on the demonstrated clinical benefit of Aucatzyl, brings new hope for adult patients with r/r B-ALL."
Claire Roddie, MD, PhD, FRCPath, the lead investigator of the FELIX study and Associate Professor of Haematology at the University College London (UCL) Cancer Institute, added, "Based on the experience in the FELIX trial Aucatzyl is highly active and can be well managed, offering an attractive risk benefit profile for B-ALL patients. In the FELIX trial Aucatzyl has shown long term persistence and deep responses which we believe are critical for long term remissions in B-ALL."
Efficacy and Safety Data from FELIX Trial
The biologics license application for obe-cel was initially submitted in November 2023, supported by data from the FELIX trial. Among the 65 patients with evaluable efficacy data, 63% achieved overall CR, including 51% who achieved it at any time and 12% with CR with incomplete hematologic recovery. The primary efficacy endpoint, CR within 3 months, was achieved by 42% of patients, with a median duration of remission of 14.1 months.
Updated data, incorporating a pooled analysis with data from the phase 1 ALLCAR19 trial (NCT02935257), were presented at the 2023 American Society of Hematology (ASH) Annual Meeting & Exposition. The ALLCAR19 trial initially enrolled patients aged 16 years and older with r/r B-ALL but was later expanded to include patients with r/r B-cell chronic lymphocytic leukemia and r/r B-cell non-Hodgkin lymphoma.
Regarding safety, the FELIX trial reported low rates of cytokine release syndrome (CRS), with only 3% of adverse events being grade 3 and none being grade 4 or 5. Grade 3 or greater immune effector cell-associated neurotoxicity syndrome (ICANS) was reported in 7% of patients.
Novel Design for Reduced Toxicity
Obe-cel features a novel fast off-rate CD19 binding domain, engineered to shorten the binding time between CAR T-cells and leukemia cells. This design aims to reduce cytokine secretion and T-cell exhaustion. As Dr. Roddie noted at the ASCO Annual Meeting, this feature could lead to a more manageable toxicity profile compared to other available therapies, potentially facilitating outpatient administration and improving patient quality of life.
Manufacturing and Distribution
Autolus will manufacture obe-cel at its dedicated facility, 'the Nucleus,' in Stevenage, United Kingdom. The facility holds a Manufacturer’s Importation Authorization and a GMP certificate from the UK's Medicines and Healthcare products Regulatory Agency, obtained in March 2024. Cardinal Health will serve as Autolus’ commercial distribution partner in the United States.
