Marathon Pharmaceuticals LLC is facing added criticism over the $89,000 price tag on its drug for a rare muscle disorder as a group of eight U.S. lawmakers said they’re concerned that it “exploits” patients. In a March 3 letter to Marathon Chief Executive Officer Jeffrey Aronin, seven Democratic U.S. senators and one independent demanded information on the closely held drugmaker’s pricing practices and product development costs for Emflaza, used to treat lethal Duchenne muscular dystrophy.