Randomized phase II study of FOLFOX +/- MET inhibitor, onartuzumab (O), in advanced gastroesophageal adenocarcinoma (GEC).

2 Background: Aberrant up-regulation of the MET/HGF pathway is associated with poor prognosis in multiple malignancies, including GEC. Onartuzumab (O) is a fully humanized, monovalent anti-MET antibody that inhibits HGF binding and receptor activation. We examined the efficacy and safety of mFOLFOX6 and O in the first-line setting for metastatic, HER2-negative GEC. Methods: This was a double-blind, placebo controlled phase II study in which patients were randomized 1:1 to mFOLFOX6 + O 10 mg/kg. Eligibility included no prior treatment for metastatic disease, age >18, ECOG 0-1, retained organ function, HER2-negative, and evaluable disease. The primary objectives were to detect a meaningful improvement in progression free survival (PFS) in the ITT population or the MET-positive (≥ 50% of tumor with moderate-strong intensity staining by IHC based on central review) subgroup. With 120 patients enrolled and 84 PFS events observed, the target HR was 0.7 in the ITT population, and 0.6 in the MET-positive subgroup...