Generic drugmakers, especially Sun Pharmaceutical Industries, are celebrating a landmark ruling by the US Supreme Court which has ruled in favour of the Indian drugmaker in its long-running patent battle with Novo Nordisk over the latter's diabetes drug Prandin.

The court has backed Sun subsidiary Caraco Pharmaceutical Laboratories in its patent litigation against Novo over a generic version of Prandin (repaglinide). In a unanimous opinion, it concluded that Caraco can seek correction of the Danish drugmaker's "inaccurate use code" regarding the combination use of repaglinide and metformin for the treatment of type 2 diabetes, namely Prandimet.

The move represents a reversal of the US Court of Appeals for the Federal Circuit’s April 2010 decision. That judgment dismissed Caraco’s claim to change Novo’s patent submissions.

Sun said it pleased that "this landmark decision will help all generic companies prevent brand companies from improperly delaying or preventing the marketing of generic drugs against their products by misrepresenting their patents to the Food and Drug Administration". Caraco's Abbreviated New Drug Application for generic Prandin is still awaiting approval at the FDA, while a separate appeal concerning the validity of patents for the drug is currently pending. before the Court of Appeals for the Federal Circuit.

James Shehan, general counsel of Novo's US unit noted that "while we are disappointed with the decision, it appears the Supreme Court has held only that Caraco may challenge the use code narrative" for the firm’s patented method of treating diabetes with repaglinide in combination with metformin. He argues that this use code narrative "is, and has always been, correct, and we are confident that further proceedings will show Caraco’s challenge…is meritless".

Novo noted that in 2011, sales of Prandin and PrandiMet in the US amounted to about 1 billion Danish kroner, or $176.4 million.

The Generic Pharmaceutical Association in the USA applauded the ruling in a case "that threatened to eliminate a critical check on brand-name drug manufacturers’ ability to block generic competition by providing FDA with misleading and overbroad descriptions of their patents".

The GPhA's chief executive Ralph Neas said the ruling is "a win for generic competition and, more importantly, a win for consumers". He added that “we commend the Supreme Court for preventing Novo’s actions from becoming a playbook for all brands and costing consumers millions of dollars by delaying the introduction of affordable, lifesaving generic drugs.”