Inclusion Criteria:  Life expectancy of ≥ 12 weeks Measurable or non-measurable disease for Part 1; measurable disease using RECIST v1.1 is required for Part 2 Recovered from prior therapy to Grade ≤ 1 or return to baseline status (except for alopecia) Eastern Cooperative Oncology Group (ECOG) performance status 0-1 Patients with adequate bone marrow function Last dose of previous anticancer therapy ≥ 4 weeks prior to first dose of NDI-101150; includes prior anti-PD-1 or anti-PD-L1 therapy, other anticancer therapy, radiotherapy, or surgical intervention For Part 2, willing to consent to required tumor biopsy(ies) For Part 1 Only (Dose Escalation, Monotherapy and Combination Therapy): Histologically or cytologically confirmed advanced or metastatic solid tumors for whom no standard therapies are available or refractory to standard therapy For Part 2 (Dose Expansion, Monotherapy and Combination Therapy): Histologically or cytologically confirmed advanced or metastatic gastric or GEJ adenocarcinoma for which no standard therapy is available or are refractory to standard therapy  Exclusion Criteria:  Previous solid organ or hematopoietic cell transplant Central nervous system (CNS) malignant disease not previously treated, active leptomeningeal disease, uncontrolled symptomatic CNS involvement, or CNS malignant disease requiring steroid or other therapeutic intervention Prior anticancer treatment Clinically significant cardiovascular disease History of severe hypersensitivity reaction to treatment with monoclonal antibody(ies) (for combination therapy cohorts only) History of interstitial lung disease, idiopathic pulmonary fibrosis, pneumonitis (including drug induced), organizing pneumonia (i.e., bronchiolitis obliterans, cryptogenic organizing pneumonia, etc.), or evidence of history of pneumonitis on chest computed tomography scan in the last 6 months Known additional malignancy that is active and/or progressive requiring treatment Unstable or severe uncontrolled medical condition (e.g., unstable cardiac function, unstable pulmonary condition, uncontrolled diabetes) or any important medical or psychiatric illness or abnormal laboratory finding