Magenta Therapeutics has recruited Pfizer (NYSE: PFE) executive John Davis to serve as the startup’s new chief medical officer. Before coming to Cambridge, MA-based Magenta, Davis was Pfizer’s senior vice president and head of early clinical development. His experience also includes positions at Baxalta and Genentech. Magenta is developing treatments for bone marrow transplant patients who have autoimmune diseases, blood cancers, and genetic diseases. Last year, the Harvard University spinout raised $50 million in a Series B round of funding led by GV, the investment arm of Google.