New Delhi: Drug firms Lupin Ltd and Natco Pharma on Thursday said that they have entered into an alliance to jointly market generic Lapatinib Ditosylate tablets, used for treating breast cancer, in the American market.

Natco has filed an abbreviated new drug application (ANDA) seeking United States Food and Drug Administration (USFDA) approval for marketing these tablets in the strength of 250 mg, Natco and Lupin Ltd said in separate statements.

"Natco has partnered with Lupin for marketing of the product," Natco Pharma said in a filing to the Bombay Stock Exchange (BSE).

Lapatinib Ditosylate tablets are sold under the brand name Tykerb in the American market. The patent of Tykerb is with Glaxo.

"Tykerb had sales of USD 113.6 million as of March, 2011, according to IMS health," Lupin said.

"Natco and Lupin believe that they are the first to file an ANDA containing a paragraph IV certification for Lapatinib," it added.

This means that once their ANDA is approved, the firms could have 180 days' exclusivity for the product in the US.

Shares of Lupin Ltd and Natco Pharma were being quoted at Rs 430.80 and Rs 268 apiece, respectively, in morning trade on the BSE, up 1.35 and 2.72 per cent from their previous closing levels.