This is a dose-escalation and dose-expansion Phase 1/2a trial to evaluate the safety and tolerability of DB-1201 in subjects with advanced solid tumors.

This is a multicenter, non-randomized, open-label, multiple-dose, FIH study. The study consists of two parts: Part 1 adopts a rule based "3 + 3" design to identify MTD/RP2D; Part 2 is a dose expansion phase to confirm the safety, tolerability and efficacy in selected solid malignant tumors.

Inclusion Criteria:

1. Male or female at least 18 years old.
2. Has histologically or cytologically confirmed metastatic or locally advanced solid tumors for which no effective standard therapy existed or standard of care has failed or is not considered as an option.
3. Is capable of comprehending study procedures and risks outlined in the informed consent and is willing to provide written consent.
4. Has an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-1.
5. At least one measurable lesion as assessed by the investigator according to response evaluation criteria in solid tumors (RECIST) version 1.1 criteria.
6. Has adequate organ function within 7 days prior to initiation of the first Treatment Cycle
7. Platelet count ≥ 100 000/mm3
8. Hemoglobin (Hb) ≥ 8.5 g/dL
9. Absolute neutrophil count (ANC) ≥ 1500/mm3
10. Creatinine ≤ 1.5 × upper limit of normal (ULN), or
11. Creatinine clearance ≥ 60 mL/min (modification Cockcroft-Gault equation)

Exclusion Criteria:

1. Has a medical history of symptomatic chronic heart failure (CHF) (New York Heart Association [NYHA] classes II-IV) or serious cardiac arrhythmia requiring treatment.
2. Has a medical history of myocardial infarction or unstable angina within 6 months before Day 1.
3. Has a QTc prolongation to > 470 millisecond (ms) based on a 12-lead electrocardiogram (ECG) in triplicate.
4. Active or prior documented autoimmune disease within the past 2 years. NOTE: Subjects with a history of autoimmune thyroid disease are not excluded. Subjects with vitiligo or psoriasis not requiring systemic treatment (within the past 2 years) are not excluded.
5. Active or prior documented inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
6. History of primary immunodeficiency.
7. History of allogeneic organ transplant.
8. Has an uncontrolled infection requiring IV injection of antibiotics, antivirals, or antifungals.
9. Known human immunodeficiency virus (HIV) infection, or active hepatitis B or C infection.
10. Is a lactating mother (women who are willing to temporarily interrupt breastfeeding will also be excluded), or pregnant as confirmed by pregnancy tests performed within 7 days prior to initiation of the first Treatment Cycle.
11. Male and female subjects who are unwilling to use adequate contraceptive methods (double barrier or intrauterine contraceptive) during the study and for at least 7 months after the last dose of study drug.