* Group, researcher urge study of lower prasugrel dose
* Dangerous bleeding, cancers a concern - group
* Lilly, Daiichi confident in benefit-risk profile
* Lilly shares down 1.5 pct
By Susan Heavey
WASHINGTON U.S. regulators should halt their review of Eli Lilly and Co's bloodthinner candidate prasugrel, a consumer advocacy group and one of the drug's early researchers said on Wednesday, citing concerns over the dose tested in a major study.
"The available evidence suggests that prasugrel at a daily dose of 10 (milligrams) is unsafe, resulting in excess hemorrhage and perhaps cancer," Public Citizen's Health Research Group said in a letter to the Food and Drug Administration. "The efficacy of the drug is also in question."
The FDA's long-anticipated decision over whether to approve prasugrel, which is being developed by Lilly with Japan's Daiichi Sankyo Co Ltd, has been delayed for nearly a year. The drug is already approved in Europe and has been launched in some countries under the brand name Efient.
FDA spokeswoman Sandy Walsh said the agency had received the letter and would reply to Public Citizen. She declined to give an update of FDA's review of the drug, citing legal restrictions applying to products under consideration for approval.
Lilly and Daiichi said they "remain confident in the overall benefit-risk profile of prasugrel and stand behind the clinical trial design and results." The group's concerns were addressed at a February FDA meeting, they said in a statement.
The companies said they were working with the FDA on the final stages of the drug's review process and hoped to get it on the market "soon."
Analysts expect the potential blockbuster drug to rival Sanofi-Aventis SA and Bristol-Myers Squibb Co's $8 billion-a-year Plavix, which like prasugrel aims to prevent dangerous blood clots in heart patients. Plavix is also known by its chemical name, clopidogrel.
But prasugrel has become mired in controversy.
The FDA removed noted cardiologist Dr. Sanjay Kaul from the February advisory panel meeting because of comments he made months before, that researchers had overestimated prasugrel's ability to control clots without causing excessive harmful bleeding.
Agency officials said Lilly had contacted them about Kaul before he was removed, prompting a congressional probe.
Public Citizen, which wrote the letter along with researcher Dr. Victor Serebruany, called on the FDA not to make any approval decision until the companies conduced a new trial. Serebruany worked on early clinical studies for prasugrel and holds a U.S. patent application on it, but he sold the commercial licensing rights to Eli Lilly, Public Citizen said.
A study of more than 13,000 patients with acute coronary syndrome showed prasugrel increased the risk of possibly fatal hemorrhage by half compared with clopidogrel, and the risk of fatal hemorrhage fourfold, the group's letter said.
Prasugrel patients also saw "an excess of new cancers, especially highly metastatic solid tumors," the group wrote, adding that while the drug did "not appear to be a carcinogen, it may act as a cancer promoter."
Shares of Lilly were down 1.5 percent to $34.52 in late morning trade on the New York Stock Exchange. Daiichi shares earlier closed down 1.9 percent in Tokyo.
(Reporting by Susan Heavey; Editing by Lisa Von Ahn and Tim Dobbyn)