Inclusion Criteria:

          1. Subject must be ≥18 years-of-age at the time of signature of the informed consent form
             (ICF).

          2. Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1.

          3. Subjects with histologically or cytologically confirmed advanced solid tumors which
             have progressed despite standard therapy or for which no standard therapy exists.

          4. Subjects with life expectancy ≥3 months.

          5. Patients must have at least one measurable lesion as defined by RECIST v1.1.

          6. Patients who have sufficient baseline organ function.

        Exclusion Criteria:

          1. Severe autoimmune disease (including immune-related adverse events of prior
             immune-oncology therapy) or autoimmune disorder that requires chronic systemic
             corticosteroid treatment at immunosuppressive doses (prednisone >10 mg/day or
             equivalent).

          2. Known malignant central nervous system disease other than neurologically stable,
             treated brain metastases.

          3. History or evidence of interstitial lung disease, radiation pneumonitis which required
             steroid treatment, or idiopathic pulmonary fibrosis, pleural or pericardial effusion
             that required intervention such as a drain.

          4. 8. History of seropositive status for hepatitis B, hepatitis C and human
             immunodeficiency virus (HIV).

          5. History or evidence of active infections (Grade ≥2).

          6. History or evidence of significant inflammatory or vascular eye disorder.

          7. History of an allogeneic bone marrow or solid organ transplant.

          8. Use of systemic anti-cancer agent (except for anti-androgen therapy for prostate
             cancer) or investigational drug ≤28 days prior to the first dose of JAB-3312.

          9. History of radiation therapy ≤28 days prior to the first dose of JAB-3312, or likely
             to require radiation therapy at any time until the 30 days after the last dose of
             JAB-3312.

         10. History of transfusion of whole blood, red blood cell or platelet packets ≤2 weeks
             before the start of treatment.

         11. Subjects experiencing unresolved Grade >1 toxicity before the start of treatment.