153P - Discovery of a Novel, Dual CD73 and PD-1 Targeting Multispecific Drug Fc-Conjugate (DFC) for the Treatment of Cancer

Background

The approval of several PD-1/L1 axis inhibitors has revolutionized cancer therapy and established a role for CD8⁺ T cells in tumor destruction. While anti-PD-1 therapy has demonstrated durable responses, only a subset of patients respond. To improve response rates, we developed a multispecific PD-1/CD73 targeting DFC. CD73 catalyzes the rate limiting step in production of immuno-suppressive adenosine, which inhibits immune cell activation through a mechanism distinct from PD-1. Herein, we describe a first-in-class dual targeting DFC, comprising a multivalent conjugate of a small molecule CD73 inhibitor to a proprietary human IgG1 Fc-fusion with a PD-1 inhibitor peptide. This dual-targeting DFC has potential for differentiation from approved PD-1/L1 inhibitors.

Methods

Binding of the dual targeting DFC to biotinylated hPD-1 was determined using a commercial kit and to human CD8⁺ T cells by flow cytometry. CD73 inhibition was determined in cell-free and cell-based assays. Efficacy was evaluated in transgenic mice expressing human PD-1/PD-L1 with MC-38 (hPD-L1) tumors (Genoway, France). Tumor volumes were recorded and statistical analysis was by t-test (Mann-Whitney) or two-way ANOVA.

Results

The dual targeting DFC demonstrated potent activity against both checkpoint targets: Binding to hPD-1 with an IC₅₀ of < 1 nM and functional inhibition of CD73 with an EC₅₀ of 9 nM. Efficacy was determined in a humanized mouse model against the colon cell line MC-38 (hPD-L1). The dual targeting DFC demonstrated a statistically significant reduction in tumor volume (∼55%) at a dose of 3 mg/kg (P<0.0001). Pembrolizumab biosimilar at 10 mg/kg did not result in a significant reduction in tumor volume.

Conclusions

This work describes a dual targeting DFC with potent activity against two validated immune checkpoint pathways. The in vitro activity translated to efficacy in a humanized mouse model at doses as low as 3 mg/kg. The relative contributions of each ligand to activity against different tumors is under investigation as Cidara’s first multispecific DFC advances through preclinical development.

Legal entity responsible for the study

Cidara Therapeutics.

Funding

Cidara Therapeutics.

Disclosure

J. Levin, S. Döhrmann, N. Dedeic, A. Almaguer, D. Zuill, E. Abelovski, J. Fortier, Q. Zhao, M. Hernandez, K. Amundson, M. Moniz, H. Chen, D. Panickar, T. Lam, T. Brady, A. Borchardt, J.N. Cole, G. Hough, J.B. Locke, L.W. Tari: Financial Interests, Personal, Full or part-time Employment: Cidara Therapeutics.