Last week, Daiichi Sankyo and Eli Lilly released a press statement announcing the suspension of two small prasugrel-related pharmacodynamic clinical trials due to a dose adjustment. However, the lack of color as to what the adjustment might be has stirred up some rumblings amongst financial analysts.
Prasugrel is an investigational oral antiplatelet agent for potential treatment of acute coronary syndrome. "Prasugrel is a very high-profile drug for Lilly, and we are looking for the company to file that with FDA in the next few months," said Barbara Ryan, an analyst at Deutsche Bank. "Here is the first indication that things might not have gone as planned, but that is speculative. We won't know what the outcome of the study is until the American Heart Association meeting November 4."
According to the release, the pharmacodynamic studies compare the relative effectiveness of prasugrel and clopidogrel (Plavix) in inhibiting platelet aggregation in patients with coronary artery disease.
"We are suspending enrollment in these two small pharmacodynamic trials so that we can amend current protocols," J. Anthony Ware, Lilly cardiovascular platform leader for prasugrel, stated in a release. "These amendments are strictly protocol-related and do not provide a basis for inferring overall outcomes of other prasugrel trials."
Coming Up: Phase III Data The Phase III program for prasugrel is largely complete, and the data is expected this Sunday at the American Heart Association meeting. Lilly has not stated what the dose adjustments are (whether up or down). If they are up, it is likely an indication that the company is looking for better efficacy. If they are down, the company is adjusting for safety concerns, including, but not limited to, bleeding.
Given the proximity of that announcement with the imminent announcement of the Tritan study—a head-to-head Phase III study versus Plavix in ACS—one would speculate that the study was not a very positive one, Ryan said.
"Companies have different reasons for canceling their trials, and I don't think there is an epidemic of stopped trials," said Les Funtleyder, a drug analyst at Miller Tabak. "Clinical trials are difficult, and it is better that they stop them early than keep going and spending money."
Most analysts said that they would rather see a trial fail early before the companies have invested significant amount of money in them—as in the case of Pfizer's torcetrapib, which was suspended last year due to a high mortality rate in clinical trial patients. However, Lilly's stock did take a hit with the news, falling 6 percent last Thursday.
"What affected Lilly's stock was that there was limited information released as to why the trials were stopped and the timelines," Funtleyder said. "That raised concern that somehow you could extrapolate what happened in the smaller trials and project it onto the large trial, which you can't really do."