Key Inclusion Criteria:

          -  Subject has a histologically- or cytologically-diagnosed solid tumor which is advanced
             or metastatic and which has progressed on or following at least one systemic therapy
             regimen administered for advanced or metastatic disease or for which no approved
             therapy exists. Subject's prior treatment should include all approved regimens that
             have demonstrated a survival advantage for the subject's disease, stage, and line of
             therapy.

          -  Has measurable disease per RECIST 1.1.

          -  An adequate tumor sample must be available from core needle biopsies obtained during
             the Screening Period and following the subject's most recent systemic therapy.

          -  Agrees to an on-treatment biopsy preferably of the same lesion from which the
             pre-CBX-12 treatment sample was obtained as long as the Investigator determines such
             biopsy can be performed with acceptable safety.

        Exclusion Criteria:

          -  Cytotoxic chemotherapy, biologic agent, investigational agent, or radiation therapy
             less than or equal to 3 weeks prior to the first dose of CBX-12. The interval may be
             reduced to 2 weeks for bone only radiation therapy or investigational agents not
             expected to be associated with adverse events (AEs) after 2 weeks of last
             administration, with Medical Monitor approval.

          -  Small-molecule kinase inhibitors or hormonal agents less than or equal to 14 days
             prior to the first dose of CBX-12.

          -  Subjects who are currently receiving any other anti cancer or investigational
             agent(s).

          -  Clinically significant intercurrent disease.

          -  Subjects with primary central nervous system (CNS) tumors or clinically active CNS
             metastases or carcinomatous meningitis. Subjects with stable brain metastasis may be
             enrolled with Medical Monitor approval.