Abstract 5204: CD5-directed CAR5/IL-15 NK cells as a therapeutic platform for T-cell malignancies

Abstract Background: Engineered NK cells have increasingly emerged as a powerful allogeneic cell therapy platform, with multiple trials demonstrating meaningful anti-tumor responses, durable clinical activity, and an excellent safety profile without GVHD and low cytokine-release toxicity. Their suitability for large-scale manufacturing makes CAR-NK cells particularly attractive for broad clinical use. T-cell lymphomas and leukemias remain difficult to treat, and although CD5 is a widely expressed and clinically actionable target, CAR-T cell development has been limited by fratricide and manufacturing barriers. A CD5-directed NK cell that avoids these limitations is therefore attractive in this setting. Methods: We developed iC9/CAR5/IL-15 NK cells, an off-the-shelf engineered NK-cell therapy targeting CD5+ tumors without fratricide or GVHD. The construct incorporates IL-15 to enhance persistence and the inducible caspase 9 (iC9) safety switch for controlled elimination if needed. A panel of CD5-targeting CAR constructs incorporating different intracellular signaling was generated and screened to identify constructs that optimized NK-cell activation, cytotoxicity, cytokine production, metabolic fitness, and functional persistence. These were tested against multiple CD5+ T-ALL and T-cell lymphoma models, followed by in vivo evaluation in xenograft systems and safety testing against normal human tissues and long-term culture. Results: Several signaling domains mediated strong anti-tumor activity, each with distinct advantages. CD28- and DAP10-based designs demonstrated the most consistent performance, supporting potent cytotoxicity and enhanced NK-cell activation. After comparing functional reproducibility, including cytotoxicity, cytokine production, proliferation, and serial killing, and considering manufacturing feasibility together with our prior clinical experience using CD28- signaling in CAR-NK products, the CD28-based iC9/CAR5/IL-15 NK construct was selected as the lead therapeutic candidate. In vivo, CD28-based iC9/CAR5/IL-15 NK cells resulted in rapid tumor regression and a significant survival benefit in CD5+ T-ALL xenograft models. Safety studies confirmed the absence of off-target cytotoxicity, and prolonged culture showed no autonomous expansion or phenotypic instability. Conclusion: iC9/CAR5/IL-15 NK cells overcome the barriers that have hindered CD5-directed CAR-T cell approaches, offering a scalable off-the-shelf therapy for aggressive T-cell malignancies. A Phase I/II clinical trial evaluating this therapy in relapsed/refractory CD5+ T-cell cancers is now open and accruing at our center. Citation Format: Rafet Basar, Sunil Acharya, Nadima Uprety, May Daher, Francia Reyes Silva, Rejeena Shrestha, Bin Liu, Mayra Shanley, Merve Dede, Pinaki Banerjee, Ping Li, Paul Lin, Enli Liu, Donghai Xiong, Ken Chen, David Marin, Elizabeth Joan Shpall, Katayoun Rezvani. CD5-directed CAR5/IL-15 NK cells as a therapeutic platform for T-cell malignancies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5204.