The novel anti-CD19 autologous chimeric antigen receptor (CAR) T cell therapy obecabtagene autoleucel (obe-cel) achieved durable remissions in 40% of patients with relapsed or refractory B-ALL without a subsequent stem cell transplant (SCT), according to results from the Phase Ib/II FELIX clinical trial presented by Elias Jabbour, M.D., professor of Leukemia.

At a median follow-up of 21.5 months, these patients were in ongoing remission without SCT or other therapies.

The 12-month event-free survival (EFS) and overall survival (OS) rates were 49.5% and 61%, respectively.

Eighteen percent of patients, all with no measurable residual disease, went on to receive a SCT after obe-cel infusion.

Of these patients, 55% had persistent CAR T cells present prior to transplant. The median time to SCT was 101 days after treatment.

The median EFS and 12-month EFS rate were identical between those who did and did not receive a SCT, and similar findings were observed when researchers assessed for OS. These results suggest that SCTs did not offer additional value for these patients and that obe-cel could be considered as a standalone treatment, Jabbour explained.

“We observed that persistence of CAR T cells and B-cell aplasia both were associated with improved event-free survival in patients treated with obe-cel,” Jabbour said.

“These outcomes demonstrate a potential of a long-term plateau in the survival curve, which supports this therapy being considered as a standard-of-care for adults with relapsed or refractory B-ALL who currently have limited treatment options.” B-cell aplasia occurs when anti-CD19 CAR T cells kill CD19-expressing B-lymphocytes causing a patient to have an extremely low B-cell count.

The open-label, multi-center, single-arm trial treated 127 adult patients with relapsed or refractory B-ALL with obe-cel.

Trial participants had lymphodepletion, an important step that kills existing T-cells to create a blank slate for CAR T cell therapy, followed by obe-cel infusion in split doses on days one and 10. Side effects were consistent with previous studies, and no new adverse effects were identified.

Source: ASCO