On average, the Christmas period can lead to a weight gain of around 5 pounds. Vivus’s Qnexa is the most efficacious obesity drug to have emerged from the pipeline in years, but the recently announced results of the FORTRESS study have dealt a blow to the weight loss hopes of many - at the time of year when it is needed most.
The Fetal Outcome Retrospective TopiRamate ExpoSure Study (FORTRESS) was a retrospective assessment of the teratogenic risk of the antiepileptic agent topiramate (Johnson & Johnson's Topamax), which comprises one half of Qnexa. In this study, the medical records of three groups were analyzed: mothers and infants who had been exposed to topiramate during pregnancy, mothers and infants who had previously taken topiramate before (but not during) pregnancy, and a control group with similar medical profiles, regardless of prior use of antiepileptic drugs.
The results of the FORTRESS study demonstrated that women taking topiramate during pregnancy were almost twice as likely to deliver babies with oral clefts than those who that had taken the drug before the pregnancy, but who stopped during pregnancy (prevalence rate of 0.29% versus 0.16%; prevalence ratio of 1.88).
So, from these findings alone, it seems clear that taking topiramate during pregnancy is not a good idea. What is even more concerning, however, is when the results of the third group are taken into consideration; the control group of mother and infant dyads with similar medical profiles had a prevalence rate of only 0.07% of oral clefts. This equates to a prevalence ratio of 5.44 for the topiramate pregnancy-exposed group, versus the similar medical profiles control group.
So, what does this mean for FDA approval prospects for Qnexa?
The results of the study obviously don’t look good in terms of clearing Qnexa from the potential to cause fetal harm. The teratogenic potential of topiramate was the major concern from the FDA’s Complete Response Letter for Qnexa. However, Vivus has only submitted an application to the FDA for Qnexa to treat men and women of non-child bearing potential. Therefore, we are continuing to forecast a 2012 launch for Qnexa, despite the results of the FORTRESS study. But, if Qnexa is approved for this population, very strict controls will certainly be put in place to ensure no off-label prescribing to women of child bearing potential, and this will no doubt impact Qnexa’s sales potential. Vivus was hoping to expand the indication to include women of child bearing age if the results of the FORTRESS study had been more positive, however, this is now looking very unlikely.
Overall, Santa did not deliver great results for Vivus with the FORTRESS study. But we will have to wait until the FDA’s review on February 22, 2012 to see if it will really be bah humbug for Vivus.