Forest Laboratories ( FRX) shares had some life sucked out of them after the company announced it had signed a development and marketing agreement with Paion, a private German biotech firm, for desmoteplase, a potential stroke treatment derived from vampire bat saliva. The terms of the deal were not announced, but Forest won the rights for the drug in the U.S. and Canada in exchange for making an upfront payment on June 30. Going forward, Forest will fund the research and make milestone and royalty payments to Paion, based on the progress of the drug, which dissolves blood clots. In reaction to the news, shares of Forest dropped $1.78, or 3.1%, to $55.43. Desmoteplase has shown promise in phase II trials as a treatment for acute ischemic stroke, able to treat patients up to nine hours after they first experience stroke symptoms. Currently, the only stroke treatments that dissolve clots must be administered three hours after symptoms first surface, a narrow time-frame that usually makes it impossible to treat patients. "Desmoteplase is novel in two ways," said Howard Solomon, chairman and CEO of Forest Labs, in a statement. "Early clinical results suggest that it can more precisely target the blood clots that cause stroke and that it can be used up to nine hours after patients first experience symptoms, expanding the population of patients who may be eligible for treatment to up to 300,000 patients each year who arrive at the hospital within the first nine hours of symptom onset -- a substantial increase over the estimated 66,000 patients who arrive within the first three hours." Both companies will be working with the Food & Drug Administration on the testing and clinical trials needed to file a biologics license application. Forest said desmoteplase, which was recently granted fast-track approval by the FDA, will likely enter phase II-b clinical trials in the fall.