MTOR and plasma cell myeloma: Geldanamcyin is an inhibitor of mTOR signaling as well [115] While initially promising as an potent anticancer agent [115,179,180], its hepatotoxicity has precluded its clinical use [180,181]; however, several less toxic derivatives have been developed [182], with 17AEP-GA and 17DMAG recently demonstrating growth suppression of multiple myeloma cells similar to geldanamycin [181].