The primary objective is to evaluate the safety and tolerability of S-588210 (S-488210+S-488211) in patients with unresectable recurrent and/or metastatic solid tumors.

Inclusion Criteria:

1. Patients with unresectable recurrent and/or metastatic solid tumor of lung, esophageal, head and neck, mesothelioma, or bladder cancer (including urothelial cancer of renal pelvis, ureters, and urethra), who have progressed after conventional systemic therapies or have exhausted or are intolerant to existing treatment options.
2. Human leukocyte antigen (HLA)-A*02:01-positive patients.
3. Patients who are male or female aged ≥18 years at the time of informed consent.
4. Patients with the Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1 at enrollment.
5. Patients who have a lymphocyte count accounting for 15% or higher of the total white blood cell count within 28 days before enrollment.
6. Patients who provide a personally signed and dated informed consent document for participation in the study.
7. Patients with expected life-span of at least 3 months from the time of enrollment.

Exclusion Criteria:

1. Patients who are expected to require any of the following therapies between enrollment and completion of the Observation Period.

   • Anti-malignant tumor drug
   • Systemic corticosteroid (except for corticosteroid defined as the equivalent of prednisone ≤ 10 mg/day orally)
   • Systemic immunosuppressant drug
   • Radiotherapy (except for restricted radiotherapy for pain relief of bone metastasis) for the cancer(s)
   • Surgical therapy for the cancer(s)
   • Hyperthermia for the cancer(s)
   • Traditional Chinese herbal medicine with anti-tumor or immunosuppressant effect
   • Other investigational products

2. Patients who have severe concurrent hepatic impairment, renal impairment, heart disease, hematological disease, respiratory disease, or metabolic disease, with the exception of any symptoms and/or signs associated with cancer(s).

3. Patients who have known human immunodeficiency virus infection.

4. Patients with uncontrolled systemic or active infection.

5. Patients who had any diseases with the risk of sudden death within 12 months before enrollment.

6. Patients with a history or evidence of autoimmune diseases and/or immunodeficiencies.

7. Female patients who are pregnant, breastfeeding, or have a positive pregnancy test at the predose examinations.

8. Patients who are considered ineligible for this study by the investigator or subinvestigator due to any reasons, including inability to understand and follow the requirements of the study.