** Shares of drug developer Zentalis Pharmaceuticals ZNTL.O fall ~19% to $1.94

** ZNTL says its experimental cancer drug, azenosertib, works better than current treatments in ovarian cancer patients who have previously been treated with platinum-based chemotherapy and whose cancer has become resistant

** It reported data from two mid-stage trials testing its therapy alone or in combination with niraparib in patients with ovarian cancer and platinum-resistant ovarian cancer patients

** In one of the studies, ZNTL's drug resulted in a 5.5 months duration of response on average in patients

** Oppenheimer analyst Matthew Biegler says investors are "squabbling" as the duration of response was slightly under 6 months, a pivotal study could take another 2 years and that accelerated approval isn't a "done deal"

** Wedbush analyst Robert Driscoll says he remains "unconvinced" by the durability data that will ultimately support full approval

** ZNTL is seeking the U.S. FDA's accelerated approval for its drug to treat platinum-resistant ovarian cancer

** ZNTL fell ~81% in 2024

(Reporting by Kamal Choudhury in Bengaluru)

((Kamal.Choudhury@thomsonreuters.com))