Long-Term TIL Engraftment and Clonal Expansion After Multiple TIL and Anti-PD-1 Therapy: A Five-Year Immunogenomic Case Study
Adoptive cell therapy using tumor-infiltrating lymphocytes (TIL) can achieve durable responses in metastatic melanoma and other indications, but the long-term clonal dynamics after multiple administration and synergy with checkpoint blockade are still to be explored. We present a longitudinal case study of a prostate cancer patient treated with serial TIL infusions and delayed anti-PD-1 therapy, analyzed using high-throughput T-cell receptor (TCR) sequencing from serial blood and tumor samples over five years. TIL-derived clonotypes exhibited sustained persistence and clonal expansion in blood, with peaks corresponding to clinical response. Multiple TIL administration increased the patient exposure to the therapy, improving its pharmacokinetics profile over time. Notably, anti-PD-1 therapy administered six months post-first TIL administration further expanded both previously infused and novel TIL-derived clonotypes, coinciding with durable complete response. Serial tracking revealed stable levels of TIL-derived clonotypes up to five years post-treatment, with persistent tumor infiltration. T-cell clonotype expansion was associated with decreased TCR diversity and increased frequency of hyperexpanded clones, suggesting selective amplification of tumor-reactive populations. Our findings provide mechanistic insight into the long-term persistence and reactivation of TIL-derived immunity and illustrate the potent synergy between adoptive transfer and delayed PD-1 blockade, supporting the integration of longitudinal immunogenomic monitoring in personalized immunotherapy. Overall design: Peripheral blood and tumor biopsies were collected at baseline, following each TIL infusion, and periodically up to five years. TCRß deep sequencing was performed to track TIL-derived, blood-borne, and unique clonotypes longitudinally D= day M= month W= week Y= year TIL-1-D1: sample collected one day after first infusion,   TIL-2-D1: sample collected one day after second infusion, and so forth.