Merck & Co. Inc. said Monday it was buying privately held biopharmaceutical company Tilos Therapeutics, in a deal that could be valued at up to $773 million. The deal includes an upfront payment and contingent milestone payments. Tilos targets therapeutics for the treatment of cancer, fibrosis and autoimmune diseases. "Tilos has developed a compelling portfolio of candidates that employ a novel approach to modulating the potent signaling molecule TGFβ by binding to latency-associated peptide, with potential applications across a range of disease indications," said Dean Li, senior vice president, discovery and translational medicine, Merck Research Laboratories. Merck's stock has gained 7.9% year to date, while the SPDR Health Care Select Sector ETF has tacked on 5.2% and the Dow Jones Industrial Average has advanced 11.4%.