An open-label, multi-dose, single-arm, multi-center, Phase 1, dose-escalation study will be
      conducted to define the toxicity profile, MTD, PK, immunogenicity, and potential antitumor
      activity of MGAH22 in patients with refractory HER2 positive breast cancer and patients with
      other carcinomas that overexpress HER2 for whom no standard therapy is available. After an
      MTD has been defined, an additional cohort of patients will be treated at the MTD to obtain
      further information regarding the safety of the chosen dose, to definitively describe PK, and
      to evaluate potential anti-tumor activity of MGAH22.

      Patients will be monitored for a minimum of four weeks after administration of the final dose
      of MGAH22. The National Cancer Institute's (NCI's) Common Terminology Criteria for Adverse
      Events (CTCAE), v.4.0, will be used for grading AEs except as noted within the protocol.
      Study assessments will include AE monitoring, ECG monitoring, PK analysis of serum MGAH22,
      determination of the serum concentration of soluble MGAH22 and tumor markers, and an
      assessment of potential anti-MGAH22 antibody [human anti-chimeric antibody (HACA)] response.

      Tumor response assessments using Study Day 43 CT scans will be performed approximately six
      weeks after the first MGAH22 dose for each patient. Patients with evidence of disease
      regression (partial or complete response or stable disease by RECIST criteria) will be
      allowed to continue therapy at the same dose, or at a reduced dose if warranted by DLT or
      significant AE in Cycle 1. Subsequent cycles which will begin on Study Day 50 will consist of
      MGAH22 administration on Study Days 1, 8, and 15 of each 28-day cycle, with tumor evaluation
      every other cycle. Responding patients may receive continued antibody therapy until evidence
      of progression of disease is documented or the patient experiences DLT. Patients who have
      responded and received at least 3 years of MGAH22 study therapy may continue MGAH22
      post-progression, with or without chemotherapy, at the Investigators' discretion.