Eli Lilly and partner Daiichi Sankyo have been boosted by the news that US regulators have granted a priority review to their much-touted oral antiplatelet prasugrel.

The decision means that the US Food and Drug Administration will now decide whether to give its approval to Lilly’s New Drug Application for prasugrel, for patients with acute coronary syndrome being managed with percutaneous coronary intervention, within six months, rather than the usual 10-12 month review period. The NDA for prasugrel, which if approved will compete with Plavix (clopidogrel), Sanofi-Aventis and Bristol-Myers Squibb’s blockbuster, was submitted to the agency on December 26 last year.

Getting a priority review from the FDA has surprised many analysts, seeing that eagerly-anticipated data from a large late-stage study comparing prasugrel with Plavix unveiled in November was mixed. Lilly noted that the 13,608-patient TRITON TIMI-38 trial showed that prasugrel produced “a highly significant 19% reduction in relative risk” for the endpoint of cardiovascular death, non-fatal heart attack or non-fatal stroke when compared with Plavix, but prasugrel-treated patients also experienced a statistically significant increase in non-coronary artery bypass grafting major bleeding compared to Plavix.

Prasugrel is perceived as the jewel in Lilly’s pipeline and if it is found to be more effective than Plavix, it could have peak sales of $4 billion and more if the drug gets onto the market before generic clopidogrel is introduced in the USA in 2011.