Immunologic determinants of infusion products and the tumor microenvironment govern response to TIL therapy in...

The immunologic features of tumor-infiltrating lymphocyte (TIL) infusion products and their interactions with the tumor microenvironment that govern clinical responses in metastatic melanoma remain incompletely characterized.

We performed integrated immunophenotypic and spatial transcriptomic profiling of TIL infusion products and matched tumor microenvironments from patients treated on early-phase clinical trials.

The durable objective response rate was 36%, with a median progression-free survival of 8 months among patients treated with TIL therapy with or without additional therapies. Responders exhibited infusion products enriched for CD8⁺ T cells, stem-like memory subsets, and LAG-3-expressing CD8⁺ T cells, together with enhanced peripheral TIL persistence. The abundance of infused LAG-3+ TILs correlated with tumor reactivity and prolonged progression-free survival. Prior immune checkpoint inhibitor exposure was associated with reduced CD8⁺ stem cell memory T cell frequency and diminished co-stimulatory receptor expression, suggesting impaired TIL fitness. Tumors enriched for tertiary lymphoid structures and spatial immune programs characterized by antigen presentation, interferon signaling, and B cell activation were independently associated with clinical benefit.

These findings define an integrated framework linking TIL composition and the tumor microenvironment to therapeutic response and identify potential biomarkers and biological features that may guide patient selection and optimization of TIL therapy.

This work was funded by Iovance Biotherapeutics, the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation, the Melanoma Research Alliance, the Donald A. Adam Melanoma & Skin Cancer Center of Excellence, American Cancer Society-Leo and Anne Albert Charitable Foundation Research Scholar Grant, and Melanoma SPORE (P50CA168536).