Vivus Inc said European regulators recommended that its obesity pill not be approved, citing potential safety concerns related to the long-term use of the drug.
The European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) raised concerns over heart risks and birth defects and the drug Qsiva's use by patients for whom it was not indicated.
Vivus, which announced in late September that it was expecting a negative response, said it intends to appeal the panel opinion and request a re-examination of the decision by the CHMP.
The drug was launched in the United States in September under the brand name Qsymia, becoming the first new diet pill on the market in over a decade.
Vivus shares, which have fallen 11 percent since the September warning, were down 2 percent at $20.70 in extended trade. They closed at $21.06 on the Nasdaq on Thursday.
(Reporting by Balaji Sridharan in Bangalore, Editing by Anthony Kurian)