Abstract 5293: Preclinical development of NI-3201, a PD-L1xCD28 bispecific antibody mediating CD28 costimulation upon PD-L1 blockade
Authors: Majocchi Sara , Anceriz Nadia , Viandier Alizée , Lesnier Adeline , Cons Laura , Nouveau Lise , Pace Emily A. , Millard Bjorn L. , Daubeuf Bruno , Moine Valéry , Salgado-Pires Susana , Saro José , Shang Limin , Masternak Krzysztof , Ferlin Walter G. 
Published: March 2024

Abstract
NI-3201 is a PD-L1xCD28 bispecific antibody generated on the κλ body platform that blocks the PD-L1/PD-1 immune checkpoint pathway and conditionally provides T cell activation “signal 2” when engaging PD-L1+ tumor or immune cells (e.g., antigen-presenting cells). By combining two distinct mechanisms of action into a single molecule, NI-3201 overcomes two major immune suppression mechanisms commonly observed in a variety of solid tumors, namely: [1] suppression of T cell response (induced by PD-L1+ cells engaging PD-1 on T cells) and [2] restricted/limited T cell activation (due to the lack of costimulatory signal associated to the scarcity of CD28 ligands in the TME). Importantly, NI-3201 was designed to require primary T cell stimulation (“signal 1”) to afford its activity: in the absence of TCR engagement, NI-3201 is unable to activate T cells, thus preventing unintended systemic inflammation.
The single agent pharmacological activity of NI-3201 was assessed in vitro through a Cytomegalovirus (CMV) recall assay in which CMV+ PBMCs were cocultured with PD-L1+ cancer cell lines ectopically loaded with CMV-specific MHC-I peptides, thus providing “signal 1”. NI-3201 induced the activation and proliferation of CMV-specific T cells which resulted in killing of the target tumor cells. In vivo, the single agent activity of NI-3201 was shown in immunocompetent huCD28-transgenic mice engrafted with huPD-L1-expressing murine colon adenocarcinoma MC38 cells, a model in which NI-3201 induced durable anti-tumor immunological memory response. In humanized mouse models where T cell engagers (TCEs) were ineffective, NI-3201 was able to synergize with TCEs to control tumor growth, even inducing tumor regression in one model. The pharmacokinetics (PK) and tolerability of NI-3201 were investigated in non-human primates (NHP) after single and repeated-dosing. NI-3201 demonstrated favorable PK with close to dose-proportional concentrations being achieved. Upon repeated NI-3201 administration, no hypercytokinemia was observed; only a mild and transient IL-6 release and associated increase in C-reactive protein (CRP) levels were seen, with no clinical signs reported. The favorable profile seen in NHP was supported by data generated in vitro further de-risking the cytokine release syndrome (CRS) potential. Quantitative systems pharmacology (QSP) modelling integrating both in vitro and NHP data predicted a drug concentration required for optimal NI-3201 activity in the TME, and preliminary data suggests optimal patient activity at Q2W-Q3W dosing schedule.
The anti-tumor activity as a single agent or as universal combination partner for TCEs, shown in vitro and in vivo, together with the favorable safety profile of NI-3201, support its clinical development planned to start in Q1 2025.
Citation Format: Sara Majocchi, Nadia Anceriz, Alizée Viandier, Adeline Lesnier, Laura Cons, Lise Nouveau, Emily A. Pace, Bjorn L. Millard, Bruno Daubeuf, Valéry Moine, Susana Salgado-Pires, José Saro, Limin Shang, Krzysztof Masternak, Walter G. Ferlin. Preclinical development of NI-3201, a PD-L1xCD28 bispecific antibody mediating CD28 costimulation upon PD-L1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5293.