Merck & Co has received a new approval from US regulators for its much-touted type 2 diabetes drug Januvia but the good news was tempered just a little by reports that the firm is to change the label on the treatment to include a warning about hypersensitivity reactions.

The US Food and Drug Administration has approved expanded labelling for Januvia (sitagliptin), Merck’s dipeptidyl peptidase-4 inhibitor, can now be prescribed as an initial therapy in combination with metformin and as add-on therapy to a sulfonylurea, ie glimepiride and in a combination of a sulfonylurea and metformin when dual therapy does not provide adequate glycaemic control. It is already approved as a monotherapy, and as an add-on with metformin or thiazolidinediones and has proved to be a hugely successful treatment for the firm since it was launched in the USA in October 2006. Second-quarter sales reached $144 million and when Merck posts its third-quarter results on Monday, another strong performance is expected.

However the firm also noted that the expanded labelling for Januvia has been updated to include post-marketing reports of hypersensitivity reactions in patients treated with the drug which include anaphylaxis and angioedema. They also include exfoliative skin conditions, notably the rare but potentially fatal Stevens-Johnson syndrome. Merck stated that “because these reactions are reported voluntarily from a population of uncertain size”, it is not possible to “reliably estimate their frequency or establish a causal relationship to drug exposure”, noting that over two million prescriptions have been written for Januvia since it was launched and the overall incidence of adverse reactions have been similar to placebo.

RNAi technology licensed from Protiva

The Januvia news came just after Merck announced that it has licensed a technology from Canada’s Protiva Biotherapeutics called SNALP< which is used in the development of treatments using RNA interference. The deal, for which financial details were not disclosed, means that Protiva has also agreed to drop all litigation against Merck’s Sirna Therapeutics subsidiary, acquired at the end of 2006 for $1.1 billion, relating to the SNALP technology.

However Protiva itself is still facing a legal battle with fellow Canadian group Tekmira Pharmaceuticals Corp over certain RNAi technology. The latter’s chief executive, Timothy Ruane, said “we are confident in our position and we will continue our focus on bringing resolution to this dispute…whether through the courts or other mechanisms”. Tekmira is working in tandem with Alnylam Pharmaceuticals, which recently ended its own RNAi alliance with Merck.