GW pharmaceuticals A UK Company has plans of starting a Phase 1 clinical trial of a medicine which is derived from cannabis on an experimental basis.

The company said researchers had found cannabis not only contains an active ingredient called tetrahydrocannabinol (THC) that acts on CB-1 and CB-2 receptors to boost the appetite, but also has an ingredient called tetrahydrocannabivarin (THCV) that has the opposite effect.

"GW is now working towards starting a Phase I study looking at the effects of THCV in obese healthy volunteers," a spokesperson said.

GW becomes the latest in a growing list of pharmaceutical companies large and small that are exploring diet drugs based on the body's cannabinoid system. But while the target is the same, GW's approach is somewhat different than that of Sanofi-Aventis, which continues to await U.S. FDA action on diet drug Acomplia.

Merck & Co. has a diet drug, MK-0364, that works by blocking the CB-1 receptor like Acomplia which it hopes to submit for FDA approval in 2008, and Pfizer has a CB-1 receptor antagonist in Phase III trials but has not yet announced when it expects to file for FDA approval.

Bristol-Myers Squibb and its partner, Solvay Pharmaceuticals are making another CB - 1 antagonist but its lacking behind.