Several years ago, antiobesity drug development was not looking so hot. In 2007, Sanofi-Aventis failed to win US Food and Drug Administration (FDA) approval for rimonabant a pill that successfully helped people shed pounds because the drug carried risks of depression and suicidal thoughts. Then, in 2008, Merck pulled the plug on its Phase 3 trials of taranabant because it also engendered suicidal thoughts and neurological effects in some participants. And a decade before those late-stage disappointments, a couple of FDA-approved weight-loss drugs were making headlines for carrying dangerous side effects. In 1997, the FDA pulled the obesity medications fenfluramine (of the wildly popular fen-phen drug combination) and dexfenfluramine (Redux) off the market after research turned up evidence of heart valve damage in people taking the drugs.
By 2009, Big Pharma was backing out of the weight-loss market, with Merck and Pfizer abandoning their programs to develop drugs similar to rimonabant and taranabant, which block cannabinoid receptors in the brain. Although the antiobesity drug market was big according to CDC estimates, about 35 percent of adults in the U.S. are obese a blockbuster weight-loss pill that didn’t have serious side effects was proving elusive.
But a few firms, including several small biotechs, decided to stick with it. “Some of the prior experience with drugs on the market, like fen-phen and Redux, have likely led large pharma to view the therapeutic space with some conservatism,” says Preston Klassen, executive vice president and head of global development at Orexigen Therapeutics, a small, California-based firm. “And generally, when you have that situation, smaller companies will step into that void when the science makes sense.” And their perseverance is starting to pay off. After a years-long drought in approvals for antiobesity medications, in the past few years the FDA has approved four new drugs specifically for general obesity: Belviq and Qsymia in 2012, and Contrave and Saxenda in late 2014. Three of these four were developed by small companies whose success hinges on one or a few compounds aimed directly at treating general obesity.
The recent burst of antiobesity drug approvals reflects an evolving appreciation for the molecular intricacies of this multifaceted, chronic disease. Today’s antiobesity drugs including the four recent approvals and several more in development have traded the blunt cudgel of appetite suppression for more precise targeting of pathways known to play roles in obesity. “With our understanding of the complex biology of obesity and all of the different molecules and receptors involved in the process, we’re much better able to target those molecules and receptors,” says Arya Sharma, chair in obesity research and management at the University of Alberta in Canada. “These are very specific agents that are designed for very specific actions. There is renewed enthusiasm in this field.”………
