Sun Pharmaceutical Industries, one of India's largest drugmakers by market value, has lost out on a $ 3 billion revenue potential from the US market. This was after a rival beat it to gain the US regulator's approval to sell the world's best selling anti-depressant.

The US Food and Drug administration (FDA) recently benchmarked further generic approvals of the tablet form of Effexor XR (venlafaxine) to the US-based Osmotica Pharmaceutical's marketing application. The approval makes Sun Pharma's marketing application invalid.

Sun Pharma will now have to conduct a fresh bio-equivalence study comparing its products with Osmotica's tablets and resubmit their ANDA, which effectively prevents its plans of launching the drug in the US market. Effexor XR extended release drug in capsule form had an annual sales of $ 3 billion for the month ended September 2008 and is the largest selling drug of Wyeth. Osmotica has already launched its tablet version following the product patent expiry of the basic ingredient in June, this year.

"The resubmission and approval of fresh ANDA after conducting bio-equivalence studies will take over two years. Sun Pharma was expecting US-FDA approval for this drug in the third quarter of this financial year," said Ranjit Kapadia, head – Life Science Research, Prabhudas Lilladher.