A Phase 1/2 Adaptive Dose-Escalation and Expansion Study of Dual-Targeting Chimeric Antigen Receptor Natural Killer (CAR-NK) Cells Directed Against DLL3, CD56 (NCAM1), and/or GD2 in Adults With Relapsed/Refractory Small Cell Lung Cancer

Rationale: SCLC is characterized by rapid progression, early relapse after platinum-based therapy, and antigen heterogeneity. DLL3, CD56 (NCAM1), and GD2 are frequently evaluated SCLC-associated surface targets. Dual-target CAR designs may reduce antigen-escape risk compared with single-target approaches. Investigational products: Three off-the-shelf allogeneic CAR-NK cell products are evaluated. Each product is manufactured from healthy-donor NK cells and engineered to express a dual-target CAR plus a safety switch (e.g., inducible caspase-9) and a persistence support element (e.g., IL-15 support). The exact construct features can be adapted to the sponsor's platform. Study schema: (1) Screening and biomarker assessment, including tumor antigen profiling for DLL3, CD56, and GD2 by immunohistochemistry (IHC) or validated equivalent assay. (2) Phase 1 dose escalation in up to three parallel arms (one arm per dual-target construct) using a modified 3+3 design to determine MTD and/or RP2D. (3) Interim construct selection based on a composite of safety (DLT rate), manufacturability/feasibility, in vivo expansion/persistence, and preliminary efficacy. (4) Phase 2 expansion cohort treated with the selected construct at RP2D to further characterize safety and estimate antitumor activity. Conditioning and dosing: Participants receive lymphodepleting chemotherapy (e.g., fludarabine and cyclophosphamide) followed by CAR-NK infusion(s). Because NK-cell persistence can be limited, repeat dosing within a cycle is permitted (e.g., Day 0, Day 7, Day 14), and a second cycle may be allowed in responders without prohibitive toxicity. Safety monitoring: Participants are monitored for cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), infusion reactions, cytopenias, infections, and other adverse events. An independent safety monitoring committee reviews cumulative safety at each dose level and prior to construct selection. Follow-up: Clinical follow-up continues for 24 months for efficacy and late toxicity. Long-term follow-up for gene-modified cell products (up to 15 years) may be conducted per local regulatory requirements to monitor delayed adverse events.