TGF-βRII/IL-15 Immunotherapeutic complex targets exhausted CD8+ T cell subsets in lymph nodes and tumors

Exhausted CD8+ T cells, located within the tumor-draining lymph nodes (TDLNs) are responsible for maintaining tumor-specific responses in cancer. Here, we demonstrate that a bifunctional TGF-βRII/IL-15 protein complex (HCW9218), with TGF-β neutralization and IL-15 immunostimulatory activities, is capable of localizing to the TDLNs and tumors after subcutaneous administration, neutralizes TGF-β, expands progenitor stem-like exhausted T cells (TPEX) in TDLNs, and promotes their infiltration into tumors. Immune-checkpoint-inhibitors (ICIs) significantly enhanced the effects of HCW9218 on TPEX, and synergistically improved HCW9218 anti-tumor efficacy in melanoma and reduced spontaneous lung metastasis in breast cancer models. In a dose-escalating clinical trial in patients with chemo-refractory/relapsed solid tumors, HCW9218 monotherapy was well-tolerated, reduced serum TGF-β levels, promoted CD8+ T cell expansion in peripheral blood and CD8+ T cell infiltration in tumor biopsies. These findings provide a strong basis for using HCW9218 to enhance the efficacy of ICIs against solid tumors in the clinical setting.