Bristol-Myers Squibb has suffered a setback with the news that regulators in the USA want more information on its organ transplant drug belatacept, despite an advisory panel backing the treatment in March.

The US Food and Drug Administration has issued a complete response letter regarding the Biologics License Application for belatacept in kidney transplantation and while no new clinical studies have been requested, the agency wants to look at the 36-month data from ongoing Phase III studies to further evaluate the long-term effects of the drug. The BLA included 24-month data.

B-MS noted that other requests raised in the letter primarily relate to “information to support the manufacturing of belatacept and the proposed risk evaluation and mitigation strategy”. The company said it was continuing to work closely with the FDA to address its questions and remains “committed to belatacept as a potential new therapeutic option for kidney transplant patients”.

The FDA’s decision has surprised observers seeing as how at the beginning of March, the agency’s Cardiovascular and Renal Drugs Advisory Committee voted 13 to five to recommend approval. However panel members did suggest at the time that that additional studies are needed to evaluate the long-term safety and efficacy of belatacept, a selective T cell co-stimulation blocker.

On a conference call for the first-quarter results at the end of last week, B-MS R&D head Elliot Sigal said given that the advisory committee was held less than two months ago, and the fact that belatacept will have a REMS, “there's a significant amount of work that we need to finish prior to approval”. He added that “we are all ready with the supply and the preparations for launch”, which B-MS believes will happen ten days after approval is finally gained.

Belatacept is one of the five potential blockbusters in its pipeline that B-MS hopes will fill the earnings gap that will appear when the anticoagulant Plavix (clopidogrel) goes off-patent in 2012.