Actavis Plc said U.S. health regulators denied approval to its contraceptive patch for women and asked for more data.
The U.S. Food and Drug Administration questioned the differences in size and formulation of the patch used in trials and the to-be-marketed patch.
The generic drugs maker, which received a "complete response letter" from the FDA, said it planned to work closely with the agency to address the questions.
Such letters typically lay out FDA concerns that need to be addressed before a treatment is approved.
Actavis' contraceptive skin patch is designed to provide continuous delivery of the hormone norethindrone, a type of progestin, during a once-weekly, seven-day dosing regimen.
Progestin, the synthetic form of female sex hormone progestogen, inhibits ovulation and thickens the layer of mucus at the cervix so sperm cannot enter the uterus.
The treatment will compete with Johnson and Johnson's Ortho Evra, an estrogen/progestin combination contraceptive patch. Estrogen is another female sex hormone.
A progestin-only patch can be safer than combination patches as high levels of estrogen are often linked to blood clotting disorders and an increased risk of cancer.
The company also filed on Tuesday an application to market the generic version of Merck & Co Inc's NuvaRing, a estrogen/progestin combination hormonal contraceptive vaginal ring.
Actavis said it may be the first applicant to file the application, which, if approved may entitle it to 180 days of generic market exclusivity.
Shares of Dublin, Ireland-based Actavis were down 0.6 percent at $165.16 in early trading on the New York Stock Exchange on Tuesday.
(Reporting by Esha Dey and Natalie Grover in Bangalore; Editing by Joyjeet Das and Saumyadeb Chakrabarty)