Safety Study of MGA271 in Refractory Cancer

An open-label, multi-dose, single-arm, multi-center, Phase 1, dose-escalation study will be conducted to define the toxicity profile, maximum tolerated dose (MTD), pharmacokinetics (PK), immunogenicity, and potential antitumor activity of MGA271 in patients with refractory cancer that expresses B7-H3.

In the initial segments of the study, patients will be monitored for a minimum of four weeks after administration of the final dose of MGA271. Study assessments will include adverse event (AE) monitoring, electrocardiogram (ECG) monitoring, PK analysis of serum MGA271, determination of the serum concentration of soluble MGA271 and tumor markers, and an assessment of potential anti-MGA271 antibody [human anti-human antibody (HAHA)] response.

Tumor response assessments using Study Day 43 CT scans or MRI will be performed approximately six weeks after the first MGA271 dose for each patient. Patients with evidence of clinical benefit (partial or complete response or stable disease by RECIST or RANO Response criteria) will be allowed to continue therapy at the same dose, or at a reduced dose if warranted by dose limiting toxicity (DLT) or significant AE in Cycle 1. Subsequent cycles which will begin on Study Day 50 will consist of MGA271 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.

In the Expansion Segment of the study, patients will receive weekly, uninterrupted infusions with an initial response assessment at 8 weeks. Tumor evaluation will be carried out by both RECIST and immune-related response criteria (irRC).