The FDA asked Vivus to remove a restriction against use by women of childbearing potential from the proposed label of its experimental weight loss drug Qnexa (phentermine/topiramate), the company announced Monday. The drugmaker said that it is currently revising risk language on the label for this group, which generally includes women under the age of 55, but said that the drug will remain contraindicated for women who are pregnant. The FDA declined to comment on why it requested that the restriction be removed. Qnexa is currently scheduled to be reviewed by an advisory committee on February 22.
US regulators declined to approve the therapy in 2010 and requested additional information on the drug’s cardiovascular effects, as well as the risk of birth defects associated with topiramate. In September 2011, the agency agreed to allow an early resubmission of Vivus's application before the completion of the FORTRESS study, which assessed the offspring of women exposed to topiramate during the first trimester of pregnancy. Top-line preliminary data from the trial showed that topiramate was associated with higher rate of cleft palates in offspring of women who took the drug during pregnancy, compared with those who took other epilepsy drugs.
Reflecting on the news, which sent shares of Vivus up as much as 14 percent, the company warned that the move "should not be interpreted to mean that the potential for FDA approval of Qnexa has improved." Moreover, the move should not be viewed as a signal that any final Qnexa label will not include contraindications or warnings for specific populations, the company said.
However, Leerink Swann analyst Steve Yoo said that the announcement "markedly increases the importance of the Qnexa FDA advisory panel because the patient population discussed at the panel will encompass the majority of the market." Still, he warned that seeking approval for a larger patient population could also increase the risk that the drug is not approved or potentially delay approval. Yoo noted that "if the panel focused solely on the limited indication it would have been possible for Vivus to obtain Qnexa approval prior to the final FORTRESS data," but the agency may now opt to wait until the final results are known, reducing the likelihood that a decision will be made by the agency's April 17 deadline. J.P. Morgan analyst Cory Kasimov echoed these views, noting that the FDA may view the announcement as a major amendment and request more time to review the application. However, he noted that "we think shifting the approval timeline by a few months will have little bearing on the stock's valuation."
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