Combination therapy with anti-LAG3 and anti-PD1 modulates immunosuppressive intratumoral CD4+ regulatory T cells in metastatic melanoma 4544

Abstract Description Regulatory T cells (Tregs) drive immunosuppression in the tumor microenvironment and suppress anti-tumor immunity. Combination immunotherapies (IO) including anti-PD1+anti-LAG3 improve survival in advanced melanoma, but how combination therapy modulates Tregs is unclear. To address this question, we sought to better understand Treg cell states, differentiation dynamics, and gene regulatory networks using single-cell RNA sequencing data from tumors of IO-naïve melanoma patients treated with anti-PD1+anti-LAG3. We found that this combination therapy significantly modulated intra-tumoral Treg cell frequencies post-treatment, leading to a reduction in TNFR(hi) Tregs—the core suppressive tumor-infiltrating Treg subset—in patients that achieved pathological response. In addition to modulation of cell frequencies, combination therapy promoted unique gene regulatory networks (GRN) in TNFR(hi) Tregs post-treatment, compared to its monotherapies. Pathway enrichment analysis of the GRNs in this Treg subset revealed enrichment for inflammatory responses and the regulation of T cell activation and differentiation, suggesting the potential of combination therapy to modulate Treg phenotype. These findings suggest that combination therapy with anti-PD1+anti-LAG3 consistently modulated intratumoral Tregs in melanoma patients who respond to therapy, indicating that changes in Treg frequencies and states may enhance antitumor immunity. Funding Sources This study is supported by NIHP50 CA254865; P50 CA097190; R35 CA26385; BMS CA224-070. Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)