The phase 1/2 clinical study includes three stages: Phase 1 dose escalation, phase 1 PK expansion and phase 2 cohort expansion：

• Phase 1: Assesse safety, tolerability, PK, immunogenicity and preliminary efficacy of QLS5133 in advanced solid tumors. Phase 1 dose escalation will use ATD + BOIN, the maximum sample size for each dose group is 12. For Phase 1 PK expansion, 1 to 4 appropriate doses will be selected. After the DLT observation period in the selected dose group up to 12 subjects (including those subjects in the dose escalation stage) can be further enrolled for PK expansion.
• Phase 2: Evaluates QLS5133's anti-tumor efficacy in subjects with advanced solid tumors. at least 2 dose groups will be expanded.

Inclusion Criteria:

• Aged ≥ 18 years on the day of signing the ICF, male or female;
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) score: 0 or 1;
• Measurable disease, per RECIST v1.1;
• Adequate organ function;
• Recover from all reversible AEs from previous anti-tumor treatment (i.e., Grade ≤ 1, according to NCI-CTCAE v5.0), excluding alopecia (any grade) and Grade ≤ 2 neuropathy peripheral, or who experience other abnormalities that are not clinically significant or toxicities judged to have no risk by the investigator;
• Left ventricular ejection fraction (LVEF) ≥ 50%;

Exclusion Criteria:

• Previous treatment with drugs targeting CDH6 (including ADCs), or any drug containing topoisomerase I inhibitors (including ADCs);
• Large and uncontrollable pleural, pericardial or abdominal effusion before the first dose (those who are stable for at least 2 weeks after drainage can be enrolled);
• Progressive or symptomatic brain metastases;
• Clinically significant bleeding symptoms or obvious bleeding tendency within 1 month before the first dose
• History of significant cardiac disease, or poorly controlled diabetes mellitus;
• History of recurrent autoimmune diseases;
• History of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML);
• History of other active malignant tumors within 3 years before signing the informed consent form;
• If female, is pregnant or breastfeeding;
• Be allergic to any component of QLS5133 or its excipients.