This is a Phase Ib/II, open-label clinical study designed to evaluate the safety, tolerability, preliminary anti-tumor activity, recommended Phase 2 dose (RP2D), pharmacokinetic (PK) characteristics, and immunogenicity of DXC006 in combination with an immune checkpoint inhibitor (ICI) or platinum-based chemotherapy in patients with small cell lung cancer (SCLC).

Inclusion Criteria:

1. Voluntarily signed informed consent and willingness to comply with the protocol requirements.
2. Male or female.
3. Age ≥18 years and ≤75 years.
4. Life expectancy ≥3 months.
5. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2.
6. Histologically or cytologically confirmed small cell lung cancer (SCLC).
7. Toxicity from prior anti-tumor therapy has resolved to ≤ Grade 1 as defined by NCI-CTCAE version 6.0 (except alopecia); peripheral neuropathy must have completely resolved.
8. Adequate hepatic, renal, coagulation, and cardiac function.
9. The participant and their spouse agree to use effective barrier or pharmacologic contraception (excluding rhythm method) from the time of signing the informed consent until 6 months after the last dose of study treatment.

Exclusion Criteria:

1. Histologically or cytologically confirmed combined SCLC, NSCLC, sarcomatoid carcinoma, or large cell neuroendocrine carcinoma.
2. Within 14 days prior to the first dose: underwent plasmapheresis; received systemic corticosteroid therapy at a daily dose >10 mg prednisone or equivalent (or equivalent anti-inflammatory activity) for more than 3 consecutive days (short-term use for prevention of contrast media allergy is permitted).
3. Prior allogeneic hematopoietic stem cell transplantation (HSCT) or history of solid organ transplantation.
4. Prior treatment with CD56-targeted therapy.
5. Symptomatic brain metastases or leptomeningeal metastases.
6. History of severe or life-threatening immune-related adverse events or infusion-related reactions (including permanent discontinuation of immuno-oncology therapy due to intolerance).
7. Active autoimmune disease or immunodeficiency, or a history of such conditions.
8. Evidence of significant cardiovascular risk.
9. Dyspnea or current requirement for continuous supplemental oxygen therapy, or current active pneumonitis or interstitial lung disease (except mild cases as determined by the investigator).
10. History of other primary malignancies, with the exception of malignancies that have been cured and have a very low risk of recurrence within 5 years, such as basal cell carcinoma or squamous cell carcinoma of the skin, or carcinoma in situ of the cervix or breast.
11. Severe non-healing wound, ulcer, or bone fracture; or major surgery within 28 days prior to dosing, or anticipated major surgery during the study period.
12. History of hypersensitivity to any component or excipient of DXC006, immune checkpoint inhibitors, or platinum-based chemotherapy.
13. Active hepatitis B (HBV-DNA above the upper limit of normal at the central laboratory or >1000 copies/mL); hepatitis C infection (positive hepatitis C antibody or positive HCV RNA PCR result).
14. Known positive serology for human immunodeficiency virus (HIV); active syphilis (patients with positive syphilis antibody only are eligible); potential active pulmonary tuberculosis (chest imaging within 3 months prior to the first dose suggestive of active tuberculosis infection).
15. Active bleeding within 30 days prior to screening, or risk of major gastrointestinal bleeding or hemoptysis as determined by the investigator; or hereditary bleeding tendency, coagulopathy, or bleeding symptoms requiring other medical intervention.
16. Severe arterial or venous thromboembolic events within 6 months prior to study drug administration, such as cerebrovascular accident (including transient ischemic attack), deep vein thrombosis, or pulmonary embolism.
17. Positive serum pregnancy test or currently breastfeeding female participants.
18. Active infection requiring medical therapy (CTCAE Grade ≥2); uncontrollable pleural effusion, ascites, or pericardial effusion requiring repeated drainage.
19. Administration of live attenuated vaccines within 28 days prior to the first dose.
20. Other conditions that, in the judgment of the investigator, may affect the patient's participation in the study.
21. Poor general condition, such as requirement for mechanical ventilation and/or intravenous catecholamine infusion, and/or severe neurological impairment, coma, and/or quadriplegia with complete loss of communication ability (deafness, blindness, aphasia); uncontrolled seizures; other psychiatric disorders that may affect study participation.