Study of INBRX-106 and INBRX-106 in Combination With Pembrolizumab (Keytruda®) in Subjects With Locally Advanced or Metastatic Solid Tumors (Hexavalent OX40 Agonist)

Select Inclusion Criteria: * Males or females aged ≥18 years. * Parts 1 and 3 (escalation cohorts): Subjects with locally advanced or metastatic non resectable solid tumors, whose disease has progressed despite all standard therapies or for whom no further standard or clinically acceptable therapy exists. * Part 2 (single-agent expansion cohort): Subjects with NSCLC, melanoma, HNSCC, G/GEA, RCC, or TCC, with histologically confirmed, locally advanced or metastatic, non-resectable disease, which has progressed despite all standard therapies including CPI or for whom no standard or clinically acceptable therapy exists. * Part 4 (expansion cohorts in combination with pembrolizumab, with or without chemotherapy): Subjects with melanoma (all types), HNSCC, G/GEA, RCC, TCC, NSCLC, or MSI-high, TMB-high, MMR-deficient tumors, with histologically confirmed, locally advanced or metastatic, non resectable disease, which is either CPI-naive (melanoma, HNSCC, NPC) or progressed despite all standard therapies including CPI (NSCLC, RCC, TCC, uveal melanoma, MSI-high, TMB-high, or MMR-deficient solid tumors) or for whom no standard or clinically acceptable therapy exists. * For Cohort F3 (NSCLC), subjects may have progressed on no more than 2 lines of standard therapy that must include at least one PD-1/L1 regimen. * For Cohort F4 (HNSCC and NPC), subjects may be previously treated with no more than 1 prior chemotherapy regimen in metastatic setting. Prior PD-1/L1 in curative (neo-adjuvant/adjuvant) setting is allowed only if completed \>/= 6 months prior to progression to local recurrence or metastatic disease. * For Cohort F8, subjects must have previously untreated, histologically confirmed Stage II, IIIA or IIIB (T3-4N2) NSCLC. Lymph node disease requires histologic confirmation, while T3 disease requires only radiographic documentation. Subjects need to be able to undergo planned surgery. * All subjects with non-squamous NSCLC must have documentation of absence of tumor activating EGFR mutations and absence of ALK gene rearrangements. * PD-L1 by IHC (22C3): Parts 1 and 3: IHC optional. Part 2: IHC result mandatory but any score allowed. Combined Positive Score (CPS) ≥ 1% (or Tumor Proportion Score ≥50% for NSCLC; for TMB-high tumors, any TPS% is allowed). Part 4: Combined Positive Score (CPS) ≥ 1% (or Tumor Proportion Score ≥50% for NSCLC; for TMB-high tumors, any TPS% is allowed). For Cohort F8, any TPS (including 0%) is acceptable. * Adequate hematologic, coagulation, hepatic and renal function and ECOG score as defined per protocol. Select Exclusion Criteria: * Prior exposure to OX40 agonists. Exposure to anti-PD-1 and/or anti PD-L2 CPIs or an agent targeting other co-stimulatory T-cell receptor pathways. * Receipt of any investigational product or any approved anticancer drug(s) or biological product(s) within 4 weeks prior to the first dose of study drug with certain exceptions. * Hematologic malignancies (e.g., ALL, AML, MDS, CLL, CML, NHL, Hodgkin's lymphoma and multiple myeloma) * Prior or concurrent malignancies. Exception: Subjects with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessments of INBRX-106. * Grade ≥ 3 immune-related adverse events (irAEs) or irAE that lead to discontinuation of prior immunotherapy. Some exceptions as defined per protocol apply. * Active autoimmune disease or documented history of autoimmune disease that required systemic steroids or other immunosuppressive medications. Certain exceptions as defined in protocol apply. * Diagnosis of immunodeficiency or treatment with systemic immunosuppressive medications within 7 days prior to the first dose of study drug. Certain exceptions as defined in protocol apply. * History of hepatitis B, hepatitis C, or human immunodeficiency virus (HIV) infection. Exceptions as defined in protocol apply. * Active interstitial lung disease (ILD) or pneumonitis or a history of ILD or pneumonitis requiring treatment with steroids or other immunosuppressive medications. * Clinically significant cardiac condition, including myocardial infarction, uncontrolled angina, viral myocarditis, cerebrovascular accident, or other acute uncontrolled heart disease \< 3 months prior to enrollment on this trial; left ventricular ejection fraction (LVEF) \< 50%; New York Heart Association (NYHA) Class III or IV congestive heart failure; or uncontrolled hypertension; or oxygen saturation \<92% on room air. * Active, hemodynamically significant pulmonary embolism within 12 weeks prior to enrollment on this trial. * Major surgery within 4 weeks prior to enrollment on this trial. * Anti-infectious drug treatments (i.e., antibiotics) within 4 weeks prior to the first dose of study drug. * Prior organ allograft transplantations or allogeneic peripheral blood stem cell (PBSC) or bone marrow (BM) transplantation. * Additional in- and exclusion criteria per protocol.