Obecabtagene autoleucel demonstrated safety and efficacy in adults with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL), according to research presented at the ASCO Annual Meeting 2023.

These results, from the phase 2 FELIX study (ClinicalTrials.gov Identifier: NCT04404660), were presented by Claire Roddie, MD, PhD, of University College London in the UK.

The trial included 94 patients with CD19-positive relapsed/refractory B-ALL who received obecabtagene autoleucel. The median age of these patients was 50 years (range, 20 to 81), and the median number of prior therapies was 2 (range, 1 to 6). The median bone marrow (BM) blast percentage was 49.5% at screening and 41.1% at preconditioning. Extramedullary disease was present at preconditioning in 19.1% of patients.

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Obecabtagene autoleucel was administered in up to 2 doses. For the first infusion, patients with BM blasts up to 20% received 100×106 chimeric antigen receptor (CAR) T cells, while those with BM blasts greater than 20% received 10×106 CAR T cells.

In patients who tolerated the first obecabtagene autoleucel infusion with no immune effector cell-associated neurotoxicity syndrome (ICANS) or with cytokine release syndrome (CRS) lower than grade 2, an additional obecabtagene autoleucel infusion was given. This infusion consisted of 310×106 CAR T cells for patients who initially had BM blasts up to 20% or 400×106 CAR T cells for those with BM blasts greater than 20%.

Ultimately, 94% of infused patients received both infusions. The median follow-up was 9.5 months.

The overall remission rate was 76%. The complete response (CR) rate was 54.3%, and the rate of CR with incomplete count recovery (CRi) was 21.3%. The median duration of response was 14.1 months, and 97% of evaluable responders were minimum residual disease negative.  

Grade 3 or higher CRS occurred in 3.2% of infused patients. Grade 3 or higher ICANS was reported in 7.4%. There was 1 death considered related to obecabtagene autoleucel. 

Dr Roddie noted that this study population was heavily pretreated, older, and had a high disease burden. “Despite all of these odds being stacked against the product, obe-cel was able to achieve CR or CRi in 76% of those infused patients,” she said.

Disclosures: This research was supported by Autolus Therapeutics. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Roddie C, Sandhu KS, Tholouli E, et al. Safety and efficacy of obecabtagene autoleucel (obe-cel, AUTO1), a fast-off rate CD19 CAR, in relapsed/refractory adult B-cell acute lymphoblastic leukemia (r/r B-ALL): Top line results of the pivotal FELIX study. ASCO 2023. June 2-6, 2023. Abstract 7000.