3058 Background: IMGN388 is a novel antibody-drug conjugate (ADC) composed of an integrin-targeting fully human antibody with the maytansinoid, DM4, attached via a covalent bond. IMGN388 has shown strong activity against human xenograft lung, colon, pancreatic, ovarian and breast tumors in nude rat models. Methods: This is a first-in-human study of IMGN388. New cohorts of patients with advanced solid tumors receive increasing doses of IMGN388, given intravenously, to establish its maximum tolerated dose (MTD). The primary study objectives are to evaluate the safety, MTD and pharmacokinetics (PK) of IMGN388 when given every 3 weeks. Secondary objectives include evaluation of pharmacodynamics, immunogenicity and evidence of activity. Results: 26 patients received a total of 52 cycles of IMGN388 at doses ranging from 5 to 80 mg/m2. IMGN388 was generally well-tolerated. Grade 1/2 toxicities assessed to be treatment related include: fatigue, nausea, anorexia, vomiting, diarrhea, headache and allergic reaction....