June 20 (Reuters) - U.S. health regulators informed Pozen Inc that they have come to a preliminary determination that the drugmaker's experimental stomach ulcer drug did not show bioequivalence with 325 mg aspirin, further jeopardizing the drug's chances to win approval soon.
Pozen's shares were down 19 percent in extended trade, after closing at $7.45 Wednesday on the Nasdaq.
The stock had plunged by nearly a third in April, when the U.S. Food and Drug Administration suggested the company also seek approval for a lower version of the drug, and that it may limit the drug to a smaller-than-expected patient population.
In a regulatory filing Wednesday, Pozen said the FDA now advised it that its lower dose drug would also likely need an in vivo bioequivalence study to win approval.
Pozen had said In April that it did not intend to conduct a new study for the lower dose and would instead submit existing data in support of the application. At the time, the company said it expected its filing for marketing approval to be delayed by six months.
The oral, once-daily drug is a combination of aspirin and AstraZeneca's Prilosec, a commonly used gastric medicine. If approved, the pill would offer a convenient alternative to patients who would otherwise have to take these two drugs separately.
Pozen said on Wednesday it planned a follow-up call with the FDA in the next few weeks to determine the next steps in satisfying the bioequivalence requirements and any impact on the approval filing timeline.