The latest deadline for an agency decision is this coming Friday and the outcome is extremely important for the drugmaker and its partner, Daiichi Sankyo, which have already endured a three-month delay while the FDA completed its review of the blood thinner.

“It’s by far the biggest event at Lilly for quite some time,” David Heupel, a portfolio manager with Thrivent Investment Management, tells Reuters, noting the outcome has equally serious implications for Bristol-Myers Squibb and Sanofi-Aventis, which co-market the rival Plavix treatment.

The main study for the drug contained mixed results - prasugrel was effective at preventing heart problems, but caused increased bleeding (back story). Lilly stock could jump as much as 10 percent on an approval, or fall as much as 10 percent if regulators require additional extensive data, JP Morgan analyst Chris Schott tells Reuters.

Morningstar analyst Matthew Coffina gives prasugrel a 70 percent chance of approval at some point, and is expecting a US launch in mid-2009, with annual sales of $2 billion in about 10 years, Reuters writes.

In a clinical trial, prasugrel was pitted against Plavix, and results released last November found prasugrel was 19 percent more effective than Plavix in preventing cardiovascular death, nonfatal heart attacks and strokes. But prasugrel was 32 percent more likely to cause serious bleeding, raising questions about its overall appeal to doctors and patients and FDA examiners, Reuters adds.

The bleeding risk was most common among patients weighing less than 135 pounds, over 75 years old or who had suffered a stroke previously. The FDA initially was expected to rule on prasugrel in June, but extended the review by three months to weigh more info. The FDA could approve prasugrel, but with restrictions that address patients that are most at risk of bleeding, Reuters continues.

Regulators could warn doctors against prescribing it for those at-risk patient groups. Patients using the drug might also be required to enroll in a registry to make sure they are safely taking the med. Analysts believe a registry is unlikely, but could dampen potential sales if physicians find the conditions too burdensome.

JP Morgan’s Schott tells Reuters he would not be surprised if the FDA required an additional short study testing a lower-dose version in the bleeding-prone groups, which would likely delay the drug’s approval by a year.

Another scenario: the FDA could require data from an ongoing large 10,000 patient study that is testing prasugrel against Plavix among patients with heart problems. Results of that study are not expected until early 2011. Such a prolonged delay could prevent prasugrel from making deep inroads before cheap generic forms of Plavix reach the market in late 2011, Reuters notes.

“Generic Plavix will be a competitive threat no matter when prasugrel is launched,” Morningstar’s Coffina tells Reuters. “If it were delayed it would just make it that much harder.”

Source: Reuters