IN10018 Monotherapy or in Combination With Docetaxel in Gastric or GEJ Adenocarcinoma

Inclusion Criteria: * 1.Has histologically or cytologically confirmed diagnosis of locally advanced and/or metastatic gastric or GEJ adenocarcinoma. * For monotherapy, participants need to be failed to respond to standard therapy or standard or curative therapy does not exist or is not tolerable. * For combination therapy, participants need to have disease progression within 3 months after at least first-line therapy. * 2.Has at least one measurable tumor lesion per RECIST 1.1. * 3.Has an ECOG performance status of 0 or 1. * 4.Estimated life expectancy is more than 3 months. * 5.Adequate organ and bone marrow functions. * 6.Has been fully informed and provided written informed consent for the study Exclusion Criteria: * 1.Has other histological types other than adenocarcinoma. * 2.For participants with HER2/neu positive tumors or have an unknown tumor status, need to match the following: * If HER2/neu positive, participant must have documentation of disease progression on trastuzumab or other anti-HER2/neu therapy. * Participants with unknown status must have their HER2/neu status determined locally. If HER2/neu-negative, the participant will be eligible. If HER2/neu-positive, the participant must have documentation of disease progression on trastuzumab or other anti-HER2/neu therapy. * 3.Has had disease progression after docetaxel/paclitaxel containing treatment (combination therapy only). * 4.Has received prior systemic therapies (i.e. chemotherapy, biotherapy, endocrinotherapy, and immunotherapy) within 4 weeks prior to start of study treatment. * 5.Has received prior radiotherapy within 2 weeks prior to start of study treatment. * 6.Has severe allergy or hypersensitivity to IN10018 and/or docetaxel, or any components used in their preparation or has contraindication for taxane therapy. For participants in monotherapy group, only restriction to IN10018 applies. * 7.Has severe renal disease or impaired renal function. * 8.Has an active infection requiring systemic therapy within 2 weeks prior to start of study treatment. * 9.Has a history or current evidence of interstitial lung disease.