Once again, the FDA has delayed its approval of prasugrel, a blood thinner that Lilly and its partner, Daiichi Sankyo, have been hoping will one day compete against Plavix, which is marketed by Bristol-Myers Squibb and Sanofi-Aventis.

This is the second time the agency has postponed approval. However, the delay last June was largely expected, given uncertainty over the increased risk of major bleeding associated with the blood thinner that was revealed in a clinical trial last November. In the study, prasugrel was pitted against Plavix and was 19 percent more effective in preventing cardiovascular death, non-fatal heart attacks and strokes. But prasugrel was 32 percent more likely to cause serious bleeding.

In a brief statement, Lilly says the FDA “did not complete its review for the prasugrel new drug application by the Prescription Drug User Fee Act goal date of September 26, 2008,” and then attempts to put a positive spin on the setback.

“We remain engaged in collaborative and productive discussions with the FDA regarding the details of our application. This is a very large, complex submission, and it should not be surprising that delays occur,” Jennifer Stotka, Lilly’s vp for global regulatory affairs, says in a statement. “Daiichi Sankyo and Lilly will not speculate on the timing or what the outcome will be. However, the review is very far along, and we remain optimistic.”

In an investor note, Tim Anderson of Sanford Bernstein writes: “Two outstanding questions include whether they will get the lower 5mg dose approved (we don’t think so), and whether they have a clean label without restrictions (we don’t think so)…

“Our best guess at this point is that while the review is not yet complete, a final decision by FDA is not likely to require that Lilly and Daiichi generate new clinical data; the issue may be a smaller one like finessing the label, the risk management plan, etc. We assume (prasugrel) launches in the fourth quarter, but that the drug won’t turn profitable until 2010. By 2015, our sales forecast of $950 million accounts for 10 percent of Lilly’s earnings per share.

“Daiichi Sankyo and Lilly remain confident in the submission package for prasugrel and look forward to bringing this medication to the market for ACS patients who are being managed with PCI,” John Alexander, Daiichi’s global head of research and development, adds.