SCOTTSDALE, Ariz., May 30 (UPI) -- U.S. medical scientists are conducting a clinical trial on an investigational stroke drug that’s derived from snake venom. Mayo Clinic researchers in Scottsdale, Ariz., said the fibrinogen depleting drug called ancrod might reduce the extent of disability resulting from acute ischemic stroke -- a stroke in which a blood vessel to the brain is blocked, leading to loss of neurological function.