Organization and Nature of Operations	12 Months Ended
Organization and Nature of Operations	Dec. 31, 2014
Accounting Policies [Abstract]
Organization and Nature of Operations	1. Organization and Nature of Operations MacroGenics, Inc. (the “Company”) was incorporated in Delaware on August 14, 2000. The Company is a clinical-stage biopharmaceutical company focused on discovering and developing innovative monoclonal antibody-based therapeutics for the treatment of cancer, as well as various autoimmune disorders and infectious diseases. The Company generates its pipeline of product candidates from its proprietary suite of next-generation antibody technology platforms which it believes improve the performance of monoclonal antibodies and antibody-derived molecules. These product candidates, which the Company has identified through its understanding of disease biology and immune-mediated mechanisms, may address disease-specific challenges which are not currently being met by existing therapies.

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