Sept. 26 (Bloomberg) -- Eli Lilly & Co.'s experimental blood thinner, prasugrel, is still being reviewed by U.S. regulators, delaying action.

``This is a very large, complex submission, and it should not be surprising that delays occur,'' said Lilly's vice president for global regulatory affairs, Jennifer Stotka, in a statement issued today by Lilly and partner Daiichi Sankyo Co. She said the review by the Food and Drug Administration ``is very far along.''

A decision was expected today, based on the FDA's usual timetable. The product is vital to plans by Indianapolis-based Lilly to replace lost revenue when its top-seller, the antipsychotic Zyprexa, loses patent protection in 2011. The consensus of analysts is that the FDA will approve prasugrel with restrictions on use and that it will generate about $570 million a year by 2012, according to analyst Seamus Fernandez.

``We remain cautious on Lilly's long-term prospects as declining sales and earnings per share post-2010 are highly likely without several new blockbuster product launches,'' said Fernandez, with Leerink Swann in Boston, in a Sept. 8 note to investors.

Lilly fell 4 percent to $44.95 in extended trading after earlier rising 22 cents to $46.82 at 4:15 p.m. in New York Stock Exchange composite trading. Daiichi Sankyo, Japan's third- largest drugmaker, fell 30 yen, or 1 percent, to 2,910 yen on the Tokyo Stock Exchange.

The FDA had no comment on the status of prasugrel, which would be marketed as Effient, agency spokeswoman Sandy Walsh said today in an e-mail.

More Fatal Bleeding

In a study, prasugrel prevented more heart attacks and strokes than Plavix, an $8.1 billion seller in 2007 for Bristol- Myers Squibb Co. and Sanofi-Aventis SA. More people taking prasugrel died from bleeding than those taking Plavix in the trial.

``Our best guess at this point is that while the Effient review is not yet complete, a final decision by FDA is not likely to require that Lilly and Daiichi-Sankyo generate new clinical data,'' said Tim Anderson, an analyst with Sanford C. Bernstein in New York, in a note today to investors. ``The issue may be a smaller one like finessing the label'' with warnings about dangers or crafting a plan to manage the drug's risks, he said.

Anderson estimates the drug won't turn profitable until 2010, and will generate $950 million in annual sales in 2015.

A decision on prasugrel was initially delayed by the FDA on June 24 when the agency said it needed more time to review information previously submitted by the companies.

Demand for Thinners

Demand for blood thinners has surged to prevent heart disease, especially in patients having arteries cleared. Prasugrel prevents platelets in the blood from clumping, causing clots that can lead to heart attacks and death.

Plavix, which may lose its patent protection in 2011, is Bristol-Myers's best seller. Prasugrel's clinical trials were designed to show the drug is superior to Plavix and to persuade doctors to prescribe it, though a generic medicine may be cheaper, Lilly has said.

A study presented in November at the American Heart Association's scientific meeting found the number of deaths from heart disease prevented by prasugrel was offset by a similar number of patients who experienced fatal bleeding.

The research, funded by Daiichi and Lilly, involved 13,608 patients followed for a more than a year in 30 countries. Though prasugrel prevented 23 more heart attacks than Plavix for every 1,000 patients, it caused 6 more cases of excessive bleeding, according to the study.

Daiichi Sankyo will market prasugrel in Japan and with Lilly elsewhere. Sales will be booked by Lilly, from which Daiichi Sankyo will receive revenue.

In addition to Zyprexa, Lilly medicines facing generic competition in coming years include the antidepressant Cymbalta and the osteoporosis medicine Evista. The three drugs generated $7.95 billion worldwide in 2007, or 43 percent of Lilly's revenue.

To contact the reporter on this story: Elizabeth Lopatto in New York at elopatto@bloomberg.net.

Last Updated: September 26, 2008 18:24 EDT