Wyeth has filed for approval in the USA of desvenlafaxine (DVS-233), a follow-up to its blockbuster antidepressant Effexor (venlafaxine).

Desvenlafaxine is a metabolite of venlafaxine and like its parent compound acts as a dual serotonin/noradrenaline reuptake inhibitor. Studies presented at the American Society for Clinical Pharmacology and Therapeutics earlier this year showed that the sustained-release formulation of desvenlafaxine provides higher blood levels of the active drug than the once-daily Effexor ER formulation of venlafaxine, and had a lower tendency to cause nausea.

“We know from clinical studies as well as clinical practice that there remain significant unmet needs in treating depressed patients," said Gary Stiles, Wyeth’s chief medical officer. "If approved, desvenlafaxine extended release will offer physicians a new clinically proven option for treating depression."

Desvenlafaxine is seen as a patent extension strategy for Wyeth as it defends its Effexor franchise, which is facing the threat of generic competition.

Revenues for Effexor XR and its immediate-release parent Effexor came in at $861 million dollars in the third quarter of 2005, a 4% decline owing to generic competition affecting the whole antidepressant sector. So far, Wyeth has been able to fend off copycat rivals to Effexor XR in the US market, which accounted for $589 million of third quarter sales, by striking a deal with generic drugmaker Teva Pharmaceutical Industries.