This is an open-label, single-arm, dose-escalation phase Ib study to determine the safety, maximum tolerated dose (MTD) and efficacy of KD019, a multi kinase inhibitor of EGFR, HER2, Src and VEGFR2, in combination with trastuzumab and mFOLFOX-6 for patients with human epidermal growth factor receptor 2 positive (HER2+) metastatic or unresectable adenocarcinoma of esophagus, gastroesophageal junction or stomach.~Patients with HER2+ metastatic or unresectable adenocarcinoma of the esophagus, gastroesophageal junction or stomach will receive trastuzumab and mFOLFOX-6 in combination with KD019 to evaluate the safety, toxicity and maximum tolerated dose of this regimen. There will be four dose cohorts for KD019. KD019 will be administered orally continuously daily on a 28 day cycle. Trastuzumab and mFOLFOX-6 will be administered as infusions every 2 weeks at standard doses without escalation. The sequence on the days when all agents are administered will be KD019 followed by trastuzumab and mFOLFOX-6.~Hypothesis A) KD019, a small molecule inhibitor of multiple receptor tyrosine kinases including EGFR, HER2, VEGFR-2 and Src, can be safely added, in an effective dose, to the every 2 week schedule of mFOLFOX-6 + trastuzumab for patients with metastatic or unresectable HER2+ adenocarcinoma of esophagus, GEJ or stomach~B) When added to mFOLFOX-6 + trastuzumab, KD019will increase response duration, progression free survival~Primary objective:~To assess the safety, tolerability, maximum tolerated dose (MTD), recommended phase II dosing (RP2D) of KD019 in combination of trastuzumab and mFOLFOX-6~Secondary objectives:~To characterize the pharmacokinetics (PK) parameters of KD019 administered once daily in combination with every 2 week mFOLFOX-6 and trastuzumab in subjects with metastatic or unresectable HER2+ adenocarcinoma of the esophagus, gastroesophageal junction (GEJ) and stomach.~To evaluate tumor biopsy specimens pre- and post- treatment with KD019 and trastuzumab for changes in target receptors and correlate with response
This dose-escalation study is to determine the safety, maximum tolerated dose (MTD) and efficacy of KD019 in combination with trastuzumab and mFOLFOX-6.