Wyeth said yesterday that US regulators have put back the decision date for DVS-233 (desvenlafaxine succinate), an extended-release form of its popular depression drug Effexor, adding another three months to the review period.

Wyeth resubmitted raw data from preclinical carcinogenicity studies in a new format at the end of July, but, as this fell within the final three months of the original review period, the US Food and Drug Administration has bought more time to properly digest the data, and is now expected to make a decision on January 22.

Also in July, it was also revealed that Wyeth would have to conduct additional clinical trials of DVS-233, to see if it can find a level that retains efficacy but improves its tolerability, particularly reducing the tendency of the drug to cause nausea, thereby pushing back its expected launch to 2007.

But hopes for DVS-233 remain high. The drug has been designed to maintain the company's antidepressant franchise now that Effexor (venlafaxine) is facing generic competition. And, aside from depression, the company is also assessing its utility in the treatment of menopausal symptoms, fibromyalgia and chronic pain from damaged nerve fibres. If its path to market is successful, the drug could well be a key driving force behind pushing Wyeth away from its troubled times of late.

According to the firm, extension of the review deadline will not infringe on its plans to roll out the drug in 2007, and shareholders remained relatively unconcerned on the news. The group’s stock actually closed up on the New York Stock Exchange, climbing $0.40 to $48.70.