US regulators have placed a partial clinical hold on all trials assessing venetoclax for multiple myeloma after a higher than expected number of patient deaths.

The move follows a review of data from the ongoing Phase III BELLINI trial testing the drug for relapsed/refractory multiple myeloma, in which a higher proportion of deaths was observed in the venetoclax arm compared to the control arm of the trial.

Data analysis showed 41 (21.1%) patient deaths in the venetoclax arm, among which 13 (6.7%) were treatment emergent, compared to 11 (11.3%) deaths in the placebo arm, among which 1 (1.0%) was treatment emergent (occurred less than 30 days after last dose of study drug).

The US FDA’s partial hold means no new patients should be enrolled in any studies of venetoclax for multiple myeloma, until a further analysis of the data is completed.

It does not, however, affect any of the approved indications for the drug, which is on the market under the brand name Venclexta/Venclyxto for chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), or any trials outside of multiple myeloma.

AbbVie stressed that despite the setback it remains confident in the benefit/risk profile of venetoclax in its approved indications.

"We will continue working with the FDA and worldwide regulatory agencies to determine appropriate next steps for the multiple myeloma programme," said Michael Severino, vice chairman and president, AbbVie.

"We will continue to further the research and development of venetoclax and other therapies with the potential to transform the standards of care in blood cancers."

Venetoclax is being developed by AbbVie and Roche. The drug is jointly commercialised by AbbVie and Roche group Genentech in the US, and by AbbVie elsewhere.