NL-201 upregulates MHC-I expression and intratumoral TCR diversity, and demonstrates robust antitumor activity as monotherapy and in combination with PD-1 blockade.

Cytokine engineering has shown promise as a means to create novel immunomodulatory agents or to improve upon the therapeutic potential of natural cytokines. NL-201, a de novo, hyperstable, interleukin-2 receptor alpha (IL-2Rα)-independent agonist of the receptors for IL-2 and IL-15, elicits robust preclinical activity in syngeneic murine cancer models, including those resistant to immune checkpoint inhibitors (ICIs). Here, we report that NL-201 monotherapy converts 'cold' tumor microenvironments to immunologically 'hot' states by driving pro-inflammatory gene expression, enhancing IFNγ-dependent MHC-I expression, and expanding both T-cell number and clonal diversity. Additionally, the combination of NL-201 and anti-PD-1 resulted in complementary antitumor activity in the immunologically 'cold' and ICI resistant B16F10, EMT6, and Renca syngeneic models. In the B16F10 model, treatment with NL-201 plus anti-PD-1 increased the abundance of CD4+ and CD8+ effector T cells in the tumor microenvironment. These findings reveal an important mechanistic basis for the antitumor activity of NL-201 both as a monotherapy and in combination with PD-1 antagonists, and provide further context for the role of IL2Rα-based signaling in ICI-resistant tumors.