This is a Phase 1, open-label, dose escalation and cohort expansion study designed to characterize the safety, tolerability, PK, PD, immunogenicity, and preliminary antitumor activity of MGD013 administered by IV infusion on every 2 weeks. The study consists of a Dose Escalation Phase to determine the MTD or maximum administered dose (MAD) of MGD013 if no MTD is defined, followed by a Cohort Expansion Phase to further define the safety and initial antitumor activity of MGD013 with the dose established in the Dose Escalation Phase.