The study is being conducted to evaluate the efficacy and safety of QL1706 versus QL1604 monotherapy as consolidation treatment in patients with limited-stage small cell lung cancer (LS-SCLC) who have not experienced disease progression after concurrent or sequential chemoradiotherapy.

QL1706 (Iparomlimab and Tuvonralimab) is a single bifunctional MabPair product against PD-1 and CTLA-4. QL1604 is a monoclonal antibody against PD-1.

Inclusion Criteria:

• The patient must be aged between 18 and 75 years (inclusive of boundary values), and both males and females are eligible.
• Pathologically confirmed LS-SCLC [I-III stage SCLC (any T, any N, M0)], according to the American Joint Committee on Cancer (AJCC, 8th edition) staging manual.
• Received 4 cycles of chemotherapy concurrent or sequential with radiotherapy. Chemotherapy must contain platinum and etoposide. Radiotherapy must be either total 60-70 Gy over 6 weeks for the QD regimen or total 45 Gy over 3 weeks for BID schedules.
• Patients must have achieved a complete response (CR), partial response (PR), or stable disease (SD) after receiving curative platinum-based CRT and must not have developed progressive disease (PD) prior to study entry.

Exclusion Criteria:

• Mixed SCLC and non-small cell lung cancer (NSCLC).
• Extensive-stage SCLC.
• Active or prior documented autoimmune or inflammatory disorders.
• Received other chemotherapy regimens besides etoposide and platinum-based therapy.
• Active or prior documented autoimmune or inflammatory disorders.
• Presence of interstitial lung disease or active non-infectious pneumonia (excluding grade 1 radiation pneumonitis not treated with corticosteroids).