Abstract 4059: Vitokine-2: A TIL-targeting tumor activable engineered IL-2 for cancer treatment
Authors: Challa Sreerupa V. , Hsieh Yao-Te , Gelinas Karen , Umana Andrea , Weng Wei-chun , Berisha Toska , Stephens Cameron , Li Yuesheng , Xu Jing 
Published: March 2024

Background: Interleukin-2 is the first approved immune-oncology (IO) drug to treat multiple metastatic cancers with durable and curative antitumor effects. Yet, its application is restricted due to severe toxicity, short half-life, and a small fraction of response rate. To reduce toxicity and improve efficacy, we developed Vitokine-2, a tumor infiltrating lymphocyte (TIL)-targeting, tumor activable, and precision engineered IL-2 that remains inert systemically but activated in the tumor microenvironment (TME).

Methods: Through protein and structure-guided precision engineering, the biological activity of IL-2 was optimized, concealed, guided to exhausted TILs, and activated at TME. The biological activity was determined by measuring proliferation (Ki67) of CD8+ T and NK cells using human peripheral blood mononuclear cells (PBMCs). Pharmacokinetics (PK), pharmacodynamics (PD), and anti-tumor efficacy were evaluated in mice, encompassing healthy and multiple syngeneic tumor mouse models.

Results: Vitokine-2 was inactive in stimulating CD8+T and NK cell proliferation in vitro. Yet, its biological activity was fully restored following the cleavage and release of the concealing domain. Vitokine-2 displayed a significantly prolonged in vivo pharmacokinetic profile due to half-life extension, concealing and reduction of target sink. Administration of Vitokine-2 in mice resulted in minimal or no detectable activation, proliferation, and expansion of cytotoxic CD8+T and NK cells in the systemic circulation. However, marked CD8+ T cell proliferation and expansion with enhanced expression of granzyme B, a cytotoxic functional biomarker, was observed within the TME. The effect was specific to cytotoxic lymphocytes but not regulatory T cells. Corroborating with the expansion and enhanced functionality of CD8+ T cells in TME, robust antitumor efficacy was observed with Vitokine-2 but not with the non-activable IL-2 counterpart. Furthermore, dose-dependent tumor killing efficacy and complete eradication of tumors were demonstrated in multiple syngeneic tumor models. Vitokine-2 was found to be safe and well tolerated with minimal interferon gamma release and body weight loss even at much higher doses.

Conclusion: Vitokine-2 is a TIL-targeting, tumor activable and precision engineered IL-2. It demonstrated robust anti-tumor efficacy with minimal systemic toxicity. It is safe, well tolerated, and permits high dose administration, yielding a widened therapeutic window. Vitokine-2 presents a paradigm-shifting, potentially a first-in-class, highly safe and efficacious IO therapy with an immense potential to address both IO-responsive and unresponsive patient population.

Citation Format: Sreerupa V. Challa, Yao-Te Hsieh, Karen Gelinas, Andrea Umana, Wei-chun Weng, Toska Berisha, Cameron Stephens, Yuesheng Li, Jing Xu. Vitokine-2: A TIL-targeting tumor activable engineered IL-2 for cancer treatment [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 4059.