Hyderabad: Natco Pharma Ltd, which has been involved in a legal battle to launch a generic version of Teva’s top-selling multiple sclerosis drug in the US market, may have to wait till September, as the US Supreme Court has referred back the case relating to Teva’s US patent to the US court of appeals for the federal circuit to review the patent’s validity.

“The Supreme Court made no finding as to the validity of the US’808 patent, but instead sent the case back to the Federal Circuit to consider the matter in view of the modified standard," Natco said in a statement.

US court of appeals for the federal circuit, a specialized court that hears the vast majority of the patent appeals in July 2013 ruled the patent was invalid, prompting Teva to seek Supreme Court review.

Natco has teamed up with Mylan, while Novartis AG’s generic subsidiary Sandoz Inc. partnered with Momenta Pharmaceuticals Inc. to challenge the validity of Teva’s key patent related to 20 mg dosage version of Copaxone in US courts.

Copaxone, with sales of $4 billion a year and which accounts for 50% of Teva’s profit, is due to expire in September. During the first nine months of last year, Copaxone reported $3.1 billion of Teva’s $15.1 billion revenue.

Even if Natco is made to wait till September to launch the generic version of Copaxone, it is still a limited competition drug with three other generic firms in market for next 3-4 years, said Hitesh Mahida, an analyst at Mumbai-based Antique Stock Broking Ltd.

Shares of Natco dropped 5.9% to Rs.1432.10 on BSE, while the benchmark Sensex rose 0.17% to 28,835 points.

“We are encouraged by the US Supreme Court’s decision and look forward to the Federal Circuit’s review," Erez Vigodman, chief executive of Teva, said in a statement.

He said the company would keep exploring “all available avenues to protect" Copaxone from knockoffs.

The version of Copaxone at issue is sold in 20 milligrams per ml. Last year, Teva launched a Copaxone at double the dose, which can be taken less frequently. Teva has been trying to migrate patients to the higher-dose version, which is covered by patents that don’t expire until 2030.

“We continue to believe that (Teva’s) patent is invalid…and we will address that issue with the Federal Circuit Court of Appeals," said Heather Breschin, chief executive officer of Mylan said in a statement.

Bloomberg contributed to this story.