A Study of MHB088C Injection Versus Treatment of Physician's Choice in Subjects With Relapsed Small Cell Lung Cancer

Exclusion Criteria

• •Participants who meet any of the following criteria will be disqualified from entering the study:
• •1. Diagnosis of other primary malignancies within 5 years prior to signing the informed consent form.
• •2. Prior pathological diagnosis of combined SCLC, or any transformed non-small cell lung cancer or transformed SCLC.
• •3. Receipt of chemotherapy within 4 weeks prior to the first administration of study drug, or receipt of radiotherapy, biologics, endocrine therapy, immunotherapy, or other anti-tumor therapy within 4 weeks prior to the first dose.
• •4. Previous or ongoing treatment with topoisomerase I inhibitors, including antibody-drug conjugates (ADCs) containing topoisomerase I inhibitor payloads.
• •5. Brain metastases (unless asymptomatic and stable for more than 4 weeks prior to randomization); presence of leptomeningeal metastases or brainstem metastases; spinal cord compression (identified via imaging, regardless of symptoms).
• •6. Bone marrow metastasis.
• •7. Prior B7-H3-targeted therapy.
• •8. Has uncontrolled or significant cardiovascular disease.
• •9. Moderate-to-severe pulmonary disease significantly impairing lung function, including idiopathic pulmonary fibrosis, autoimmune/connective tissue disorders with lung involvement, or prior pneumonectomy.
• •10. Has history of (non-infectious) interstitial lung disease (ILD)/pneumonitis that required corticosteroids, current ILD/pneumonitis, or suspected ILD/pneumonitis that cannot be ruled out by imaging at Screening.
• •11. Moderate or severe pulmonary diseases severely affecting lung function.
• •12. Active tuberculosis, autoimmune diseases not in clinical remission, other acquired or congenital immunodeficiency diseases, or history of allogeneic stem cell, bone marrow, or organ transplantation.
• •13. Serious infections within 4 weeks before the first dose, including but not limited to those requiring systemic antibiotic therapy, bacteremia, or severe pneumonia.
• •14. Clinically uncontrolled third-space effusion requiring intervention, including pleural or peritoneal effusions.
• •15. Known hypersensitivity to investigational product components, analogues, or control drugs (e.g., topotecan, irinotecan, paclitaxel).
• •16. Pregnant or lactating women, or women/men intending to conceive.