US FDA puts Zentalis' cancer drug studies on partial hold after patient deaths

(Reuters) -The U.S. health regulator has placed three studies of Zentalis Pharmaceuticals' cancer drug on partial clinical hold following the death of two trial participants, the company said on Tuesday.

Shares of the drug developer slumped about 26% to $6.22 in early trading.

The drug candidate, azenosertib, was being tested against solid tumors in an early-stage study and in patients with a type of ovarian and uterine cancer in two mid-stage studies.

"We don't think this is the end for azenosertib," Oppenheimer analyst Matthew Biegler said, adding that the hold is resolvable with enhanced patient monitoring and preventatives.

While dosing for participants already enrolled will continue, further enrollments in the mid-stage studies have been paused, the company said.

The resolution of the partial clinical hold is necessary to continue the development of azenosertib as a monotherapy, CEO Kimberly Blackwell said on a conference call, adding that other studies testing the drug in combination can continue.

The regulator's decision comes after two patients in the ovarian cancer study died due to presumed blood-related infection associated with the treatment, the company said.

Azenosertib belongs to a class of drugs that inhibit a protein called WEE1, which may be found in higher-than-normal amounts in some types of cancer cells.

Zentalis said it plans to share additional efficacy and safety data for azenosertib from the ovarian cancer trial later this year, adding that it is working with the Food and Drug Administration to resolve the clinical hold.

(Reporting by Mariam Sunny in Bengaluru; Editing by Shailesh Kuber)