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 locally advanced or metastatic, non-resectable disease, which has
             progressed despite all standard therapies or for whom no standard or clinically
             acceptable therapy exists.

          -  Part 4 (expansion cohorts in combination with pembrolizumab): Subjects with melanoma,
             HNSCC, G/GEA, RCC, or TCC, or NSCLC, with locally advanced or metastatic, non
             resectable disease, which has progressed despite all standard therapies or for whom no
             standard or clinically acceptable therapy exists.

          -  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. Part 4: Combined Positive Score (CPS) ≥ 1% (or Tumor Proportion Score
             ≥1% for NSCLC).

          -  Adequate hematologic, coagulation, hepatic and renal function and ECOG score as
             defined per protocol.

        Select Exclusion Criteria:

          -  Prior exposure to OX40 agonists.

          -  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.

          -  Known or active primary central nervous system (CNS) tumors, leptomeningeal disease
             and CNS metastases. Exception: Subjects with previously treated, asymptomatic, and
             clinically stable CNS metastases may be allowed study entry if certain criteria apply.

          -  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.

          -  Treatment with systemic immunosuppressive medications within 4 weeks 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
             for Parts 1 and 3. Exceptions as defined in protocol for expansion cohorts will 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, cerebrovascular accident, or other acute uncontrolled heart
             disease < 3 months; left ventricular ejection fraction (LVEF) < 50%; New York Heart
             Association (NYHA) Class III or IV congestive heart failure; or uncontrolled
             hypertension.

          -  Active, hemodynamically significant pulmonary embolism within 3 months 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.