Requiem for Rimonabant: Therapeutic Potential for Cannabinoid CB1 Receptor Antagonists after the Fall

The endocannabinoid system is found throughout the CNS and the body where it impacts many important physiological processes. Expectations were high that targeting cannabinoid receptors would prove therapeutically beneficial; pharmaceutical companies quickly seized on the appetitive and metabolic effects of cannabinoids to develop a drug for the treatment of weight loss. Alas, the experience with first-in-class cannabinoid type-1 receptor (CB1R) antagonist rimonabant is a now-classic cautionary tale of the perils of drug development and the outcome of rimonabant’s fall from grace dealt a blow to those pursuing therapies involving CB1R antagonists. And this most commercially compelling application of rimonabant has now been partially eclipsed by drugs with different mechanisms of action and greater effect. Still, blocking CB1 receptors causes intriguing metabolic effects, some of which appear to occur outside the CNS. Moreover, recent years have seen a startling change in the legal status of cannabis, accompanied by a popular embrace of ‘all things cannabis’. These changes combined with new pharmacological strategies and diligent medicinal chemistry may yet see the field to some measure of fulfillment of its early promise. Here, we review the story of rimonabant and some of the therapeutic niches and strategies that still hold promise after the fall.