New drugs from the dreaded deerfly?

Deerflies -- nasty, green-eyed flies found along the New England coast - have driven many a sunbather from the beach with their nasty, persistent biting.

But even these pests have a positive side. So that the deerfly can sip its meal at leisure (or until a hand slaps it away), the insect's spit contains a potent compound that helps keep the blood flowing, says Ethan A. Lerner, a dermatologist at Massachusetts General Hospital-East (MGH) in Charlestown. That compound, called chrysoptin by its discoverers, prevents particles in the blood from plugging up the nick, MGH's Suzanne A. Grevelink, Lerner, and their colleagues report in the Oct. 1 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

Last year, Lerner's group found a chemical for keeping blood vessels open in the sandfly, a tropical insect. But Lerner and Grevelink decided to look for new fly substances locally. They collected live deerflies at nearby marshes and beaches using a modified Dustbuster. Then they extracted liquid from the flies' salivary glands and tested it by adding it to solutions of platelets, tiny bloodborne particles of cytoplasm that help plug damaged blood vessels and initiate clotting.

Chrysoptin, a salivary protein, prevents the chemical changes that make platelets sticky. This protein acts by blocking certain docking sites, or receptors, on the platelets' surfaces. Normally, these receptors bind the substance that triggers stickiness, says Lerner. Without this binding, the platelets do not clump.

Substances in viper venom also work this way, says Lerner. In fact, several pharmaceutical companies are using venom to develop medications to stem blood clots involved in heart attacks or strokes. Because chrysoptin is more potent than venom, it may prove even more promising, Lerner adds.