A few hours after Sanofi-Aventis ended all clinical trials of Acomplia, Pfizer announced the termination of a late-stage obesity treatment which, like the French firm’s drug, is a cannabinoid receptor antagonist.

The New York-based drugs giant said it is ending a Phase III development programme on the investigational compound known as CP-945,598 but not on the grounds of any adverse effects. Pfizer said that based on “all currently available information” and an ongoing review of the studies by an independent data monitoring committee, it believes the drug “has the potential to be a safe and effective treatment for weight management”.

However, the company has decided to pull the plug “based on changing regulatory perspectives on the risk/benefit profile” of the drug class “and likely new regulatory requirements for approval”. Martin Mackay, president of Pfizer’s Global R&D, said that “"while confident in the safety of the compound, we believe that this is the appropriate decision based on all available information regarding this class of agents, as well as recent discussions with regulatory authorities”.

The decision to kill off CP-945,958 is not terribly surprising as Pfizer recently announced that obesity was one of the therapeutic areas it would no longer focus on. The company had said it would continue to work on the drugs it already has in Phase III development but this new class of obesity products is not cutting the mustard.

As well as Sanofi’s problems with Acomplia (rimonabant), which are well-documented elsewhere in this elert, last month Merck & Co ended development of taranabant, which blocks cannabinoid type 1 receptors in the brain. The decision was made after Phase III data showed more adverse events in higher doses of the drug, such as depression, anxiety and irritability.