• Occurrence of Adverse Events and Serious Adverse Events [ Time Frame: Study Day 50 or 28 days after last infusion ] [ Designated as safety issue: Yes ]
  Note that serious adverse events that are considered study drug related can be reported at any time after Study Day 50 or 28 days after the last infusion.
  
  

• Maximum tolerated dose [ Time Frame: Study day 50 or 28 days after last infusion ] [ Designated as safety issue: Yes ]
  

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 by RECIST criteria in patients with measurable disease or stable measurable or evaluable disease with > 25% decline in relevant tumor marker) 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.