A Phase Ⅰ/Ⅱa Study of HMPL-A251 in Participants With Advanced or Metastatic HER2-expressing Solid Tumors

Inclusion Criteria: 1. Histologically confirmed unresectable advanced or metastatic disease. 2. Have at least one measurable lesion per RECIST v1.1; 3. Life expectancy ≥ 12 weeks; 4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-1; 5. Weight ≥ 35 kg; Exclusion Criteria: 1. An established diagnosis of type I diabetes mellitus or uncontrolled type II diabetes mellitus. 2. Use of strong inhibitors or strong inducers of cytochrome P450 3A4 enzyme (CYP3A4), and inhibitors of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) within 5 elimination half-lives or 2 weeks (whichever is longer) before the first dose of study drug; 3. Toxicity from prior anti-tumor therapy has not recovered to Grade 1 or baseline prior to the first dose of study drug (except alopecia). Participants with chronic Grade 2 toxicities may be eligible after discussion between the investigator and Sponsor Medical Monitor (e.g., Grade 2 chemotherapy-induced neuropathy); 4. Baseline blood amylase or lipase exceeds the normal range and are judged by the investigators to be clinically significant; 5. Spinal cord compression, leptomeningeal disease, or clinically active central nervous system (CNS) metastases, defined as untreated or symptomatic, or requiring therapy with corticosteroids or anticonvulsants to control associated symptoms; 6. Major surgery within 28 days prior to the first dose of study drug. Participants must have recovered adequately from the toxicity and/or complications from the intervention prior to the first dose of study drug(s);