US drug giant Merck & Co has dragged Indian generic drugmaker Glenmark Pharmaceuticals to court in a bid to stop it from selling copycat forms of its diabetes drugs Januvia and Janumet.

Merck, which is known as MSD outside of the US and Canada, is claiming that Glenmark is acting unlawfully by selling generic forms of these drugs - called Zita and Zita Met - in India, as the patents protecting them are still valid, according to media reports.

In what is proving to be a bone of contention for multinational drugmakers, companies can seek approval to market a patented drug in India just four years after its launch under the countries' Drugs and Cosmetics Act, an avenue reportedly taken by Glenmark in this instance.

Company officials have thus far refused to comment on the case, but the Economic Times of India was told 'off the record' that Glenmark's versions have been priced at a 20% discount to their branded counterparts, in the hope of gaining a significant share of the market.

A spokesperson for Merck told the media that the firm is "disappointed with Glenmark's decision to introduce products that directly infringe upon our intellectual property," and stressed that it would "vigorously defend them". 

The case is yet another example of the problems arising from India's unstable intellectual property landscape; just this week the Supreme Court of India rejected Novartis' application to patent an updated version of its cancer drug Glivec (imatinib), in a decision welcomed by patient groups and generic drugmakers but slammed by the pharma.

"We strongly believe that original innovation should be recognised in patents to encourage investment in medical innovation, especially for unmet needs," argued Novartis India chairman Ranjit Shahani, noting that it has never been granted an original patent for Glivec in India, despite having had patents granted in nearly 40 countries.