June 18 (Reuters) - Zentalis Pharmaceuticals ( ZNTL )

said on Tuesday the U.S. Food and Drug Administration has placed

a partial clinical hold on three studies testing its cancer

drug, following the death of two trial participants.

Shares of the drug developer slumped about 30% to $5.88 in

premarket trading.

The drug, 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.

The regulator's decision comes after two patients in the

ovarian cancer study died due to presumed sepsis, a condition

where the body's immune system has an extreme response to an

infection, the company said.

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 FDA to resolve the

clinical hold.