Merck & Co's immunotherapy Keytruda led to a high response rate for patients with the blood cancer multiple myeloma when added to standard therapy in a small, early stage trial, according to data presented on Monday. The Phase I study tested Keytruda in combination with Celgene's Revlimid and the corticosteroid dexamethasone in patients whose disease had progressed after they had already received several other treatments, including several who were not helped by previous treatment with Revlimid.