This is a first-in-human (FIH), open-label, multicenter dose escalation and expansion study of ALK201. The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of ALK201 as a monotherapy in adult participants with Advanced Solid Tumors. The study will also identify recommended dose(s) for subsequent clinical studies of ALK201.

Inclusion Criteria:

• Men and women ≥18 and ≤75 years old on the day of signing the ICF
• At least 1 measurable lesion per RECIST v1.1
• Expected survival ≥3 months
• Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 or 1
• Adequate organ function
• Female participants of childbearing potential or male participants whose partner is a female of childbearing potential agree to use medically effective contraceptive methods from the date of signing the ICF until at least 6 months after the last dose of the IP, and during this period, male participants are not allowed to donate sperms

Exclusion Criteria:

• Active or pre-existing autoimmune diseases that may relapse
• Pleural effusion, pericardial effusion, or intraperitoneal effusion accompanied with clinical symptoms, clinically poorly controlled, or requiring repeated drainage
• Allergies to any component of ALK201 or other monoclonal antibodies
• Primary central nervous system malignancies, or active metastases to central nervous system and/or metastases to meninges
• Combined with ≥ Grade 2 stomatitis and/or nose bleeding at screening
• Vaccinated with live vaccines within 4 weeks prior to the first dose

Note: Other protocol defined Inclusion/Exclusion criteria may apply