Abstract B151: Discovery and characterization of a novel small molecule brain penetrant PD-L1 inhibitor

Abstract

Abstract Introduction: Immunotherapy has revolutionized cancer treatment in the last decade. Several monoclonal PD-1 and PD-L1 antibodies have been approved for treating various cancers. Small molecule PD-L1 inhibitors with brain-penetrating ability may have potential to overcome the limitations of antibodies and bring benefit for patients with intracranial tumors. Leveraging advanced computation-aided structural analysis and medicinal chemistry design, we have successfully discovered an innovative orally available small molecule PD-L1 inhibitor ABSK044. In preclinical experiments, this compound demonstrates robust T-cell activating ability, strong anti-tumor efficacy, and brain-penetrating activity. Method: ABSK044's ability to block PD-1-PD-L1 interaction was evaluated by HTRF assay and cellular luciferase reporter assay. Its biological activity was evaluated in vitro in MLR and in vivo in syngeneic tumor models. Results: ABSK044 strongly inhibits PD-1-PD-L1 interaction with an IC50 less than 1nM in vitro and very potently rescues PD-L1-induced suppression of T cell activation signaling in cells. Furthermore, it efficiently rescues cytokine production in CD8+ T cells suppressed by PD-L1, reaching a level comparable to that of PD-L1 antibodies. In in vivo studies, oral administration of ABSK044 strongly inhibits tumor growth to an extent similar to therapeutic anti-PD-L1 antibodies. Notably, ABSK044 demonstrates excellent brain penetration with a Kp value exceeding 0.4. DMPK and safety profiling demonstrate excellent drug-like properties of ABSK044. Conclusion: ABSK044, presented here by Abbisko Therapeutics, is a highly potent and orally available small molecule PD-L1 antagonist with brain-penetrating activity. Its superior profile supports its fast-track preclinical development. Citation Format: Yongxian Zhang, Mingming Zhang, Baowei Zhao, Hongping Yu, Yao-Chang Xu, Zhui Chen, Haiyan Ying. Discovery and characterization of a novel small molecule brain penetrant PD-L1 inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B151.