Merrimack Pharmaceuticals, Inc., a biopharmaceutical company, engages in discovering, developing, and preparing to commercialize medicines paired with companion diagnostics for the treatment of cancer primarily in the United States. Its therapeutic oncology candidates in clinical development include MM-398, a nanotherapeutic encapsulation of the chemotherapy drug irinotecan, which is has completed Phase III clinical trials for the treatment of patients with metastatic pancreatic cancer whose cancer had progressed on treatment with the chemotherapy drug gemcitabine; in a Phase I clinical trial as a monotherapy in patients with glioma and in combination with cyclophosphamide in patients with pediatric solid tumors; and in a Phase 1 translational clinical trial designed to identify predictive biomarkers associated with MM-398. The company’s therapeutic oncology candidates also include MM-302 that is in Phase II clinical trial for the treatment of patients with ErbB2 (HER2)-positive, locally advanced or metastatic breast cancer; MM-121, which is in Phase II clinical trial for the treatment of patients with heregulin positive, advanced non-small cell lung cancer, as well as ovarian, breast, and non-small cell lung cancers; and MM-111 that is in a Phase II clinical trial for the treatment of patients with advanced gastric, esophageal, and gastroesophageal junction cancers. In addition, its therapeutic oncology candidates consist of MM-151 and MM-141, which are in Phase I clinical trials for the treatment of patients with solid tumors. The company has collaboration and license agreements with Baxter International Inc., Baxter Healthcare Corporation, Baxter Healthcare SA, Actavis, Sanofi, PharmaEngine, Inc., Dyax Corp., Adimab LLC, and University of California. Merrimack Pharmaceuticals, Inc. was incorporated in 1993 and is headquartered in Cambridge, Massachusetts.