Abstract 3504: QL415, a tumor targeted IL-15 fusion protein stimulating both lymphoid and myeloid immune cells for optimal anti-tumor immune response

Abstract Cytokines are potent stimulators of the immune system and have long been investigated and used as therapeutics to treat cancer. However, free cytokines have short half-life and the lack of tumor targeting often results in systemic toxicity. IL-15 is a stimulatory cytokine that shares the common beta and gamma receptors with IL-2. In contrast to IL-2, IL-15 is more selective for NK and effector memory T cells, with less proliferative effect on Tregs, making it a more preferred therapeutic candidate for cancer. QL415 is an anti-PD-L1 x IL-15 fusion protein designed to enhance tumor accumulation and prolong blood circulation, thereby widening the therapeutic window. IL-15 and IL-15 receptor alpha sushi domain are covalently linked to the C-terminus of our proprietary PD-L1 antibody. Fc-mediated effector functions were ablated using mutations in the CH2 domain, to prevent depletion of effector immune cells. In vitro studies showed QL415 to be highly potent in promoting proliferation and pSTAT5 signaling of IL-15 -responding NK92 and M07e cells. QL415 selectively induced proliferation of NK and CD8+ T cells from human PBMC in vitro and mouse CD8+ and NK1.1 cells in vivo. In a MC38 mouse colon cancer model expressing human PD-L1, QL401 was highly effective in suppressing tumor growth, in contrast to PD-L1 monoclonal antibody or a non-targeted IL-15 control. Follow up tumor rechallenge study showed protective memory against cognate MC38 but not B16F10. In a separate MC38 tumor model using a mouse surrogate molecule of QL415, immunophenotyping of antigen presenting cells offered preliminary evidence of enrichment of conventional dendritic cells 1 in the tumor draining lymph nodes. Therefore, QL415 not only directly stimulates effector immune cells, but also indirectly through antigen presenting cells, promotes robust anti-tumor response. In non-human primates, Q415 was tolerated up to 1.5 mg/kg, well above the effective therapeutic dose. In light of these favorable preclinical efficacy and safety results, a phase 1 dose escalation and expansion study has been initiated to evaluate the safety, tolerability, and early efficacy of QL415. Citation Format: Irene Tang, Lauren Schwimmer, Monica Jin, Shenda Gu, Wei Wei Prior, Arianne Capacio, Hieu V. Tran, Allan Chan, Anna McClain, Shihao Chen, Chuanzeng Cao, Xiaoran Wu, Yanling Xu, Dongmei Guan, Xi Chen, Xianli Su. QL415, a tumor targeted IL-15 fusion protein stimulating both lymphoid and myeloid immune cells for optimal anti-tumor immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3504.