Vivus' New Diet Drug Might Get You Pregnant (Whether You Like It or Not)
Does Vivus' (VVUS) new weight-loss drug Qnexa make you sexy and pregnant? According to the FDA, whose advisory panel votes on whether the drug should be approved tomorrow, some women got unwanted pregnancies during the drug's testing either because the drug defeated their contraception or because their fertility improved. Or because they had more sex. The FDA's briefing document says:
If approved, the person-years of exposure to PHEN/TPM [Qnexa] among women of child-bearing potential will be enormous.Qnexa is a teratogen, meaning that it can deform a fetus if a woman takes it during pregnancy. Deformities include cleft palates and limb abnormalities. Thus in Vivus' tests women were urged to make sure they used two methods of contraception (either a condom plus a cap, or the pill plus a condom, for instance). Here's what happened:
There were 34 pregnancies reported during conduct of the PHEN/TPM studies. At least 17 of the pregnancies occurred in women randomized to high-dose PHEN/TPM.In total, only four of 34 pregnancies occurred in women on the placebo (see page 106 of the document for the results table). The numbers are too small to draw conclusions about whether Qnexa is literally defeating contraceptive methods. An alternative explanation is that as the obese women lost weight on the drug, they became more sexually confident, or more sexually attractive, or less careful about contraception, and ... you can figure out the rest yourself. That's not quite how the FDA put it, of course:
Factors contributing to this [contraception] failure no doubt include weight-loss-induced improvement in fertility and perhaps a drug-drug interaction between PHEN/TPM and oral contraceptives where the former reduces the efficacy of the latter.Whatever the reason, the FDA is concerned that if the drug is approved it will generate a bunch of unplanned pregnancies:
... the occurrence of 34 pregnancies in a controlled clinical development program where enrollment required agreement for use of double barrier or oral contraceptive plus single barrier methods, as well as a negative pregnancy test at each study visit underscores the large potential for pregnancy exposure with QNEXA if approved for weight loss.It's the second time that the "weight-loss experiments make you pregnant" notion has arisen in the pharmaceutical world recently. Allergan (AGN) did tests of its Lap-Band system on obese teens in Australia and three of 24 girls became pregnant. Contraceptive counseling was not part of the study protocol. D'oh! The theory that weight loss literally increases sexual activity is currently being studied at the University of Pennsylvania.
And finally: If you want more evidence that weight loss drugs are generally not successful, then check out Reuters' nice timeline of diet drug failures.
Related:
- Why the FDA Will Likely Reject 3 New Weight Loss Drugs
- Why Estimates of Future Revenues for Obesity Drugs Are Likely Off the Mark
- Why Vivus's Qnexa Might Not Avoid the Obesity Drug Graveyard
- Why Vivus's Qnexa Might Avoid the Obesity Drug Graveyard