QLS5212 for Participants With Advanced Solid Tumors

Inclusion Criteria: * Being able to provide informed consent and documentation of informed consent prior to initiation of any study-related tests or procedures that are not part of standard-of-care for the patient's disease. * Patients must also be willing and able to comply with study procedures, including the acquisition of specified research specimens. * Age ≥ 18 years old. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * For Dose Escalation, patients with histologically diagnosed unresectable, locally advanced, or metastatic solid tumors. * Life expectancy ≥ 3 months. * Measurable disease as per Response Evaluation Criteria in Solid Tumors version 1.1 criteria and documented by CT and/or MRI. 7\. Acceptable laboratory parameters: 1. Absolute neutrophil count ≥ 1,500/μL. 2. Platelet count ≥ 100 × 1000/μL 3. Hemoglobin ≥ 9.0 g/dL. 4. Albumin ≥ 3 g/dL. 5. ALT/AST ≤ 3.0 × ULN.（for patients with hepatic metastases, ALT and AST ≤ 5 × ULN.） 6. Total bilirubin ≤ 1.5 ULN or ≤ 3 x ULN for patients with Gilbert's disease. 7. a calculated or measured creatinine clearance ≥60 mL/minute. * Identification of an archival tumor sample (i.e., tissue block \[formalin-fixed paraffin-embedded\] or a series of approximately 10-15 slides). Exclusion Criteria: * History of other primary malignancies, except: Basal cell or squamous cell carcinoma of the skin, cervical carcinoma in situ, ductal carcinoma in situ of the breast, or papillary thyroid cancer that has been definitively treated with no evidence of recurrence; Other malignancies that have been adequately treated and remain disease-free for ≥3 years prior to first study dose; * Untreated or active brain metastases, including leptomeningeal carcinomatosis; * Prior systemic anti-cancer therapy within specified windows; * Prior treatment with Monomethyl auristatin E (MMAE)- or Monomethylauristatin F (MMAF)-based antibody-drug conjugates (e.g., enfortumab vedotin, disitamab vedotin, tisotumab vedotin) or any TPBG-targeted therapy; * Clinically significant cardiovascular disease; * Uncontrolled systemic infection or active tuberculosis; * Active autoimmune disease requiring systemic immunosuppressive therapy within the past 2 years; * Active interstitial lung disease (ILD) or suspected ILD that cannot be ruled out by imaging at screening.