The goal of this Phase Ib/II interventional study is to evaluate the safety, tolerability, pharmacokinetics and efficacy of QLC5513 combined with QL1706± platinum in the treatment of patients with advanced or metastatic malignant solid tumors. This study is divided into two phases: Phase Ib is the combined dose escalation phase, where dose escalation of QLC5513 combined with QL1706± platinum is conducted and RP2D is explored; In the Phase II tumor type expansion study stage, the primary objective is to evaluate the objective response rate (ORR) of QLC5513 combined with QL1706± platinum-based treatment in patients with advanced or metastatic malignant solid tumors.

Inclusion Criteria:

1. Has an eastern cooperative oncology group (ECOG) performance status of 0 to 1.
2. Has adequate organ function.
3. The expected survival period is ≥3 months.
4. Based on the pathological report of the most recent biopsy or other pathological specimens, advanced or metastatic solid tumors confirmed by histology or cytology are not suitable for radical treatments such as surgery and radiotherapy.
5. According to the RECIST v1.1 evaluation criteria, the participants had at least one radiologically measurable lesion.

Exclusion Criteria:

1. Prior treatment with TROP2-targeting agents, ADCs with topoisomerase 1 inhibitor (TOP1i) payloads, or other TOP1i drugs.
2. There was symptomatic central nervous system (CNS) metastasis, leptomeningeal metastasis or spinal cord compression caused by metastasis before the first use of the investigational product.
3. Active, uncontrolled bacterial, fungal or viral infections.
4. Radiotherapy with more than 25% of the bone marrow exposed within 4 weeks prior to the first use of the investigational drug; Local radiotherapy (excluding brain radiotherapy) was performed within two weeks before the first use of the investigational drug.
5. Subjects with a history of a second malignant tumor other than the target indication within 5 years prior to signing the informed consent (excluding cured basal cell skin cancer, superficial bladder cancer, carcinoma in situ of the breast, papillary thyroid carcinoma, etc.).
6. Prior to the first dose of the investigational product, all reversible toxicities from prior anti-tumor therapy (excluding alopecia and pigmentation) have not recovered to ≤ Grade 1 (as assessed by CTCAE v5.0), with the exception that peripheral neuropathy must have not recovered to ≤ Grade 2. History of irAEs from prior immune checkpoint inhibitor treatment that required permanent discontinuation of the immune checkpoint inhibitor.
7. Active autoimmune disease that has required systemic treatment in the past 2 years.