Abstract 2093: PEGylated IL-2 with enhanced anti-tumor efficacy and safety profile

Abstract

Abstract Introduction: Interleukin-2 (IL-2) can activate and expand tumor killing lymphocytes. High doses of IL-2 are needed to activate CD8+ T cells. Severe toxic side effects associated with high doses, as well as the poor PK profile of IL-2, have limited its clinical usage. Various strategies have been employed to prolong half-lives of IL-2 and enable selectivity or bias towards receptor binding to reduce toxicity and maintain good efficacy. Among these, certain PEGylation strategies have generated promising clinical results, but also showed some major limitations. We report a unique PEGylation strategy to produce PEGylated IL-2 with a therapeutic window more than two times larger than the reference PEGylated IL-2. Methods: CT26 murine syngeneic model was used for evaluation of in vivo efficacy and safety. Each 6-8 weeks old female BALB/c mouse was inoculated subcutaneously in the right front flank region with CT26 tumor cells (5 x 105). Tumors were allowed to grow to mean size ~110 mm3 before randomization and treatment. Body weights and tumor volumes were measured three times per week. The tumor-free mice at the end of the study were re-challenged with CT26 colon tumor cells on the left side. Results: Utilizing our proprietary PEGylation technology, rhIL-2 was covalently connected with multiple PEG polymers through releasable linkers (RL). The releasable linkers are designed to modulate the release rate of the active IL-2 species. In CT26 syngeneic mouse model, CS-PEG-IL-2 showed significantly enhanced efficacy and safety over IL-2 and reference PEGylated IL-2. rhIL-2 (2 mg/kg, bid x 5, two cycles, i.p.) resulted in complete response (CR) in one out of eight (1/8) mice, while 3 mg/kg dose resulted in death in 8/8 mice. With the reference PEGylated IL-2, 3/8 CR were obtained at 3 mg/kg dose (q1w x 4, i.v.), and 6 mg/kg dose resulted in death in 8/8 mice. Whereas, with three CS PEGylated IL-2 analogs, 5/8 and 6/8 CR were achieved at 3 mg/kg and 6 mg/kg dose respectively, and no obvious toxicity was observed even at the highest dose. After re-challenged with another inoculation of CT26 cancer cells, the CR mice remained tumor-free until the end of the study at day 158. Conclusions: CS unique PEGylation strategy generated PEG-IL-2 with superior anti-tumor efficacy and safety profiles. Preclinical results support clinical evaluation of this novel class of PEGylated IL-2 analogs. Citation Format: Yuntao Song, Hui Li, Wei Zhang, Dayan Fu, Meng Xu. PEGylated IL-2 with enhanced anti-tumor efficacy and safety profile [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 2093.