Wall Street’s measure of how Cogent Biosciences Inc.’s KIT D816V inhibitor bezuclastinib (often shortened to bezu) might fare in mastocytosis against U.S. FDA cleared Ayvakit (avapritinib), the tyrosine kinase inhibitor from Blueprint Medicine Corp., caused the former’s stock (NASDAQ:COGT) to tumble, closing Dec. 11 at $4.06, down $4.58, or 53%. Data from the ongoing phase II Summit trial testing bezu in non-advanced systemic mastocytosis rolled out during the American Society of Hematology (ASH) meeting in San Diego. Waltham, Mass.-based Cogent’s prospect turned up a rapid and continuing improvement in patient symptoms, with a 57% median best improvement on Mast Cell Quality-of-Life.