Company blames regulatory scrutiny on this class of drugs.

Pfizer decided to ax Phase III development of its weight-management compound, CP-945,598, a selective antagonist of the cannabinoid type 1 (CB1) receptor. The firm says that FDA would likely ask for further testing, which would still not guarantee an approval.

This class of drugs has been linked to psychiatric side effects such as depression and suicidal thoughts. The FDA has thus been more vigilant with requirements for these medications. Instead of having to meet those requirements and the level of uncertainty involved, Pfizer will stop development. The firm states that all data so far, though, has shown the drug to be safe and effective.

CB1 receptor agonists were once thought to be very promising for potential obesity treatment, notes Daniel Ruppar, industry manager, North America, pharmaceuticals & biotechnology, Frost & Sullivan. “The headline example of that is sanofi-aventis’ Accomplia, which has been in Europe since 2006. Sanofi’s drug was just suspended and all trials were stopped. Merck & Co. also had a recent obesity drug failure, which was stopped in Phase III in the beginning of October.

“Anything in this drug class targeting an obesity indication at this point will have some higher safety hurdles from the FDA pretty much guaranteed,” Ruppar concludes.“Especially with Pfizer refocusing/restructuring, this makes good sense as they are probably trying to focus on the best possible compounds in the clinic to invest in.”

Pfizer previously reported that obesity was a therapeutic area it would no longer pursue but that it would see late-stage programs through. No one from Pfizer was immediately available to discuss the details of the CP-945,598 program.

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