We examined the impact of FDA's 2008 guidelines for addressing cardiovascular risks of new therapies for type 2 diabetes on clinical trials. We focused on the new class of incretin-modulating drugs, exenatide, sitagliptin, saxagliptin and liraglutide, which were approved in 2005-2010. We contrasted these findings with those from 2 different groups: 1. diabetes drugs approved in the same timeframe but with a non-incretin mechanism of action (colesevelam HCl and bromocriptine mesylate) and 2. diabetes drugs with NDAs delayed and not yet approved within the same time frame (vildagliptin, alogliptin, insulin inhalation powder, and exenatide long acting release). The new guidelines have had an important impact on clinical development. Review time has increased over 2-fold. The increase is seen even if a drug with the same mechanism of action has been already approved. Whereas exenatide (approved in 2005) required 10 months of regulatory review, the approval of liraglutide in 2010 required more than twice as long (21 months). In contrast, the marketing authorization of liraglutide in the EU required 14 months. Additionally, the manufacturer of vildagliptin announced in June 2008, 30 months after the NDA was filed, that a re-submission to meet FDA's demands was not planned. The drug however received marketing authorization in the EU in 2007. The number of randomized patients and patient-years in NDAs increased more than 2.5 and 4 fold, respectively since the guidelines. The significant cost increases and negative publicity because of rare adverse reactions will adversely affect future clinical research in type 2 diabetes and not address its burgeoning health care impact.
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