As predicted, US regulators have issued Merck & Co with a non-approvable letter for its painkiller Arcoxia as a treatment for osteoarthritis.

The decision by the US Food and Drug Administration comes as a surprise to no-one, as it follows the advice given by one of the agency’s advisory committees which voted 20-1 against recommending approval of Arcoxia (etoricoxib), a COX-2 inhibitor that has been under review since December 2003, citing a possible link to increased risks of heart attacks and strokes.

The FDA indicated that Merck would need to provide additional data in support of the benefit-to-risk profile for the proposed doses of Arcoxia in order to gain approval. The advisory panel had fiercely criticised the firm’s choice of diclofenac as the comparator drug in its New Drug Application, arguing that it has higher heart risks than similar treatments, such as naproxen.

The FDA is clearly concerned that Arcoxia could pose some of the same cardiovascular risks as the company's withdrawn pain-reliever Vioxx (rofecoxib) and given the controversial nature of that treatment, rejection of another COX-2 inhibitor was expected. However, Peter Kim, president of Merck Research Laboratories, said the firm disappointed, saying there is “more long-term safety data from controlled clinical trials, in terms of patient-years on treatment, for Arcoxia than for any other non-steroidal anti-inflammatory drugs.”

Merck is not saying whether it will conduct additional studies and resubmit its application in the future but confirmed that it will continue to market Arcoxia in the 63 countries where it is already approved. The drug brought in $265 million in revenues in 2006.