April 9, 2012
The United States Food and Drug Administration today announced that it is not ready to approve Qnexa, the "new" weight loss drug composed of two very old medications. This delay comes as a bit of a surprise since in February of this year, an advisory panel to FDA recommended for approval of Qnexa by a 20-2 vote. The day after that vote, shares of Vivus Inc, the venture-capital funded company that holds the patent on Qnexa, doubled overnight. It was widely expected that the FDA itself, a federal agency charged with, among many other duties, ensuring the safety and efficacy of interstate prescription pharmaceuticals, would likely "rubber-stamp" Qnexa's final formal approval as the first new prescription weight loss in the US in over 13 years. Alas it is not so.
Perhaps not coincidentally, the FDA has, in recent weeks, issued several statements that sounded to me like "shots across the bow" as regards Qnexa's approval status. In one such statement, the agency suggested that cardiac safety ranked among its top concerns for Qnexa and for all new weight loss drugs. While the source of this apparent angst lies in part with data that suggests Qnexa may raise heart rate in users, I believe that much of it is a lingering side effect of the horrific disaster that was fen-phen. Fen-phen was the colloquial name for the very popular 1990's combination of the (then) FDA approved weight loss medications fenfluramine and phentermine that was shown, in 1997, to cause cardiac fibrosis. While the combination of the two drugs was formally "off-label" use, the FDA at the time, wisely, chose not to use this as a self-defense and instead, fell on it's proverbial sword. This course of action was wise, I believe, because it was clear at the time, and is very clear now, that the combination of the two drugs was not precisely the source of the risk and rather that fenfluramine alone and not phentermine was the agent that caused cardiac fibrosis. My personal sense is that career staffers of the agency, the men and women who have devoted their careers to drug safety, were then and are now, fifteen years later, profoundly wounded by the fiasco. And so, to me at least, it is no surprise that the agency itself (as opposed to its advisory committees) is acting with an abundance of caution as regards Qnexa, another "combination" weight loss containing phentermine which, although it played no role in fen-phen's cardio-toxicity was, nevertheless, a passenger on the 'Titanic' and whose name still confuses people about the true cause of fen-phen's risks.
If the preceding paragraph sounds like an apology for the FDA's caution, it is. If it sounds like a defense of Qnexa, it is not. Not so much. As I have said elsewhere, Qnexa is neither an enormous breakthrough in pharmaceutical bariatrics nor is it necessarily "safe" in the sense of the term that FDA values. And the problem lies not with cardiac risk but with the much more pedestrian risks of the topiramate contained in Qnexa. While these risks aren't as dramatic or occult as heart disease, they are in some ways less controllable. Specifically, topiramate is something of "stupid-pill" that can affect users in ways that are eerily reminiscent of alcohol intoxication and could probably pose a risk not just to users but to the public. Once again, as with fen-phen, it is important to note that phentermine is not the bad actor. Furthermore, I have prescribed topiramate for weight loss for many years and I will likely continue in that practice, but ONLY in very special circumstances and only in doses lower than those found in Qnexa. My concerns with Qnexa relate to the fear that just as with fen-phen, the drug combination will prove so tempting that it will inevitably be prescribed to millions of people for whom it is an ill-advised choice.
At any rate, FDA has put the brakes on Qnexa and delayed its approval by at least three months. If I were to wager on the chances that this product would eventually be approved, yesterday I would have laid five to one odds in its favor. Today I think it's fifty-fifty. As likely as not, Qnexa will never see the light of day.