Abstact

BACKGROUND Combining interleukin-2 (IL-2) agonism with programmed cell death protein 1 (PD-1) checkpoint inhibition has shown synergistic potential in reinvigorating antitumor T cell responses. However, integrating these two mechanisms within a single molecule has been challenging due to competing requirements for PD-1 engagement and IL-2 receptor signaling. ANV600 is a novel bispecific antibody-cytokine fusion protein that targets a non-blocking epitope on PD-1, enabling cis-targeted IL-2Rβγ agonism while preserving combinability with therapeutic PD-1 inhibitors. This design allows for selective expansion of tumor antigen-specific T cells while avoiding the systemic toxicity and regulatory T cell (Treg) expansion associated with conventional IL-2 therapies. METHODS The PD-1-targeting antibody used in ANV600 was generated by immunization of humanized mice and selected for its ability to bind PD-1 without blocking the binding epitope of PD-1 checkpoint blocking agents. ANV600 was evaluated in multiple syngeneic tumor models using human PD-1 transgenic mice. Tumor-infiltrating lymphocytes were analyzed to assess the selectivity of ANV600 for PD-1+ T cell subsets. Combination studies with pembrolizumab and nivolumab were performed to assess synergy with checkpoint inhibitors. RESULTS ANV600 significantly inhibited tumor growth as monotherapy across multiple models, including the immune checkpoint-resistant B16F10 melanoma. By targeting PD-1, ANV600 selectively expanded tumor antigen-specific CD8+T cells, particularly progenitor exhausted (Tpex) and cytotoxic exhausted (Tcex) subsets, while sparing Tregs and NK cells. Combination with pembrolizumab and nivolumab resulted in additive effects, consistent with the complementary roles of PD-1 blockade in expanding Tpex cells and IL-2Rβγ signaling in reprogramming Tcex cells. ANV600's efficacy was dependent on CD8+T cells and primarily driven by tumor-resident T cells, as it remained effective despite blocked lymph node trafficking (FTY720) but was abrogated on CD8+ T cell depletion. CONCLUSIONS ANV600 represents a novel approach to delivering IL-2Rβγ agonism specifically to PD-1+ cells while preserving the binding site for PD-1 checkpoint inhibitors. By targeting a non-blocking epitope on PD-1, ANV600 enables the selective expansion of tumor-reactive CD8+ T cells while allowing independent and optimized dosing of both agents. This design ensures combinability with PD-1 inhibitors at clinically relevant doses, including in patients previously treated with checkpoint blockade. These findings support the clinical development of ANV600 as both a monotherapy and a combination therapy in cancer immunotherapy.