X4 Pharmaceuticals Inc. is a clinical-stage biopharmaceutical company. It is focused on the discovery, development and commercialization of novel therapeutics for the treatment of rare diseases. The company's product candidates include X4P-001, X4P-002 and X4P-003 which are in clinical stage. X4 Pharmaceuticals Inc., formerly known as Arsanis, Inc., is based in Cambridge, United States.