Ranbaxy Laboratories Ltd. (500359.BY) Friday said it has launched a generic version of GlaxoSmithKline's (GSK.LN) anti-herpes medicine Valtrex in the U.S., a development expected to significantly boost its financial results.

Ranbaxy--a unit of Japan's Daiichi Sankyo Co.--launched the generic drug, valacyclovir hydrochloride, in the U.S on Nov. 25.

The news underscores Ranbaxy's confidence that, despite facing regulatory issues in the U.S., it will not miss out on opportunities stemming from being the first to file generic applications with the Food and Drug Administration.

The news pushed Ranbaxy shares higher on the Bombay Stock Exchange, where they were up 2.9% to INR442.50 at 0840 GMT, while the benchmark Sensitive Index was down 2.5%.

Ranbaxy will have a 180-day exclusive marketing period for the medicine as "first-to-file" status lets it be the only maker of the drug, other than GlaxoSmithKline, for the first six months from the patent's expiry.

Annual U.S. sales for valacyclovir tablets stood at $2.2 billion, according to September data from market research firm IMS.

"Valtrex is expected to contribute $200 million to sales and $80 million to the bottom line during the six months of exclusivity," said Sushant Dalmia, pharma analyst at Mumbai-based Angel Broking.

"Ranbaxy Pharmaceuticals has introduced valacyclovir hydrochloride, 500 milligram and 1 gram tablets, having previously been granted U.S. FDA approval for these oral dosage forms," a Ranbaxy spokesman told Dow Jones Newswires.

"Ranbaxy Pharmaceuticals, being the first to file and to successfully challenge the valacyclovir patents, is the first generic pharmaceutical manufacturer entitled to offer an affordable alternative to the brand," he said.

Ranbaxy Pharmaceuticals Inc., which sells generic products in the U.S, is a wholly owned unit of Ranbaxy.

Ranbaxy's spokesman said the product is being manufactured from the production facility of its Ohm Laboratories Inc. unit in New Jersey.

In July 2007 Ranbaxy settled litigation with GlaxoSmithKline over the U.S. patent covering Valtrex. Under the agreement, Ranbaxy was to launch its generic copies of Valtrex in the U.S. in late 2009 with 180-day exclusivity.

It received final approval from the U.S. FDA to manufacture and sell generic Valtrex in early February 2007.

However, there were doubts Ranbaxy would be able to launch in time as the FDA banned it from importing more than 30 generic drugs into the U.S. in September 2008 because of violations of certain manufacturing practices at its plants at Dewas and Paonta Sahib in India.

The patent for Valtrex--which was launched in 1995 to treat genital herpes, cold sores and shingles--expires in 2009 in the U.S. and Europe, with the exception of Greece and Spain, where it expired in 2008.

Angel Broking's Dalmia said the generic Valtrex launch demonstrates Ranbaxy's ability to protect its first-to-file opportunities, despite facing FDA action and has raised confidence it will be able to do so again in future.

Ranbaxy had previously lost out on a lucrative opportunity to be the first to launch a generic version of GlaxoSmithKline's migraine drug Imitrex in the U.S. because of a delay in receiving FDA approval.

-By Rumman Ahmed, Dow Jones Newswires; 91-9845104173; rumman.ahmed@dowjones.com