1061 Anchored immunotherapy with CD137 (4-1BB) and CD122 (IL-2/15Rβ) multi-agonists induce monotherapy anti-tumor immunity and abscopal responses without systemic toxicity
Year: 2026
Type: conference-abstract
Abstract: Background CD137 (4-1BB) is a costimulatory receptor expressed by activated T and NK cells; however, clinical development of agonist anti-CD137 antibodies has been hampered by hepatotoxicity. We have previously shown that fully human αCD137 can be anchored in the tumor microenvironment by linking the antibody to aluminum hydroxide (alum) via a phosphorylated alum binding peptide (ABP). 1 To further enhance the activity of αCD137 antibody agonists, we fused CD122 stimulators (IL-2 or IL-15) to αCD137 and provide initial characterization of these anchored multi-agonists in preclinical models.Methods αCD137-ABP was genetically fused with either IL-2 or IL-15 and co-expressed with FAM20C kinase. Phosphorylation was verified by malachite green assay and alum binding was confirmed by alum retention assay. Alum-anchored αCD137-IL2-ABP (ANK-303) and αCD137-IL15-ABP (ANK-304) were characterized for in vitro potency using CD137 expressing cells with an NF-κB reporter, and CD122 expressing human cells with a STAT5 reporter or mouse CTLL-2 cells. In vivo studies were performed with C57BL/6 mice expressing the extracellular domain of human CD137 bearing dual flank MC38 syngeneic tumors. When primary tumors reached ~100 mm3 volume they were injected intratumorally once weekly, and the contralateral secondary tumor was left un-injected. Serum was harvested at various times post-injection and assessed for drug concentration and liver transaminase levels (ALT, AST), and both the primary and secondary tumors were assessed for immune cell infiltration by immunohistochemistry (IHC). Tumor volumes were compared with Two-Way ANOVA, and Mantel-Cox Log-Rank test for survival.Results Both αCD137-IL2-ABP and αCD137-IL15-ABP were phosphorylated and retained on alum. In vitro, CD137 and CD122 pathway agonism were confirmed. In vivo, ANK-303 and ANK-304 were well tolerated, with no effects on body weight or perturbations of liver enzymes, while reducing systemic exposure. ANK-303 and ANK-304 both induced tumor regression of the injected primary tumor (p < 0.0001 and p = 0.0022, respectively) and abscopal responses in the non-injected contralateral tumor (p = 0.0119 and p = 0.0272, respectively), resulting in extension of survival (p = 0.0009 for both). Combination of ANK-303 with systemic αPD-1 further enhanced abscopal responses, increased the bilateral complete response rate, and resulted in greater extension of survival (p = 0.0062). Notably, cured mice resisted rechallenge suggesting generation of anti-tumor immune memory.Conclusions Anchored αCD137–IL-2 and αCD137–IL-15 retained dual agonist functions in vitro and potentiated the therapeutic effects of αCD137 in vivo. The ability of these agents to be retained locally results in reduced systemic exposure and less toxicity. This approach warrants future development and clinical translation.Reference Newman R, Jain K, Kaufman H, Battula S. Agonistic CD137 (4-1BB) anchored immunotherapy (ANK-203) elicits potent 4-1BBL signaling in vitro and therapeutic responses against established tumors without systemic toxicity in vivo. Cancer Immunol Res. 2026;14(2_Supplement):B067.Ethics Approval All the procedures related to animal handling, care and the treatment in the study were performed according to the guidelines approved by the Institutional Animal Care and Use Committee (IACUC) of WuXi AppTec, following the guidance of the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC).
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,490
OpenAlex ID: W7225174750