A Study of AK138D1 in Advanced Malignant Tumors

Inclusion Criteria: 1. The subject must sign the written informed consent form (ICF) voluntarily; 2. At enrollment, aged ≥ 18 to ≤ 75 years, both males and females are eligible; 3. ECOG performance status score of 0 or 1; 4. Has a life expectancy of ≥ 3 months; 5. At least 1 measurable lesion as per RECIST v1.1 that is suitable for repeated accurate measurement. 6. Adequate organ function. Exclusion Criteria: 1. Prior human epidermal growth factor receptor 3 (HER3) -targeted therapies, including antibodies, antibody-drug conjugates (ADCs), chimeric antigen receptor T-cell immunotherapy (CAR-T), and others; 2. Concomitant participation in another clinical study, unless it is a non-interventional clinical study or the follow-up period of an interventional study; 3. Presence of active central nervous system (CNS) metastases. 4. Live vaccines or attenuated live vaccines administered within 4 weeks prior to the first dose, or planned to be administered during the study; use of inactivated vaccines is allowed; 5. Untreated subjects with active hepatitis B or active hepatitis C; 6. Known active pulmonary tuberculosis (TB); subjects with suspected active TB must undergo appropriate clinical assessment to rule out the presence of active disease; 7. Known active syphilis infection; 8. Subjects with known allergy to any component of any study drug; and with a history of known severe hypersensitivity reactions to other monoclonal antibodies; 9. Other reasons for ineligibility as evaluated by the investigator.