US-based immune-oncology therapy company 2seventy bio has announced that it has paused the trial investigating a new T-cell therapy to treat leukaemia following the death of a patient.

The patient was the first subject treated at the second dose level in the Phase I trial.

In accordance with protocol rules for a Grade 5 (fatal) serious adverse event (SAE), trial sponsor Seattle Children’s Hospital halted the study. 2seventy bio says it has notified the US Food and Drug Administration (FDA) and is currently investigating if its candidate was a factor in the SAE.

The PLAT-08 study (NCT05105152) is investigating SC-DARIC33, a chimeric antigen receptor (CAR) T-cell therapy, in patients with acute myeloid leukaemia. The trial set out to test the safety and feasibility of the candidate – with a primary endpoint of associated adverse events. Patients enrolled are 30 years of age or younger with relapsed or refractory CD33+ leukaemia.

2seventy bio recently reported positive preliminary results from the trial at the American Society of Gene & Cell Therapy (ASGCT) Annual Meeting in Los Angeles, California.

2seventy bio chief medical officer Steve Bernstein said: “Importantly, I’d like to offer that our thoughts are with the family during this time. The safety of every patient who participates in our studies or is treated with our therapies is the utmost priority for us, and we are in communication with FDA while we assess the data surrounding this SAE and the potential next steps for the study."

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