Combinatorial chemistry and high-throughput screening have been the rage in drug discovery since the late 1990s, but plant and animal sources still hold promise. In particular, venoms have proven to be rich areas for exploitation. Drugs derived from snakes, vampire bats, and Gila monsters are all nearing regulatory review and potentially, approval. But in September, a Food and Drug Administration advisory panel voted against approval of AstraZeneca's Exanta, a cobra venom-derived anticoagulant. These products face the same and possibly higher hurdles as other molecules when it comes to reaching the market.