Abstract 4066: Generation of tumor targeted self-assembling split IL-12 subunits for the treatment of cancer

Abstract A major milestone in immuno-oncology was the development of immune checkpoint inhibitors, resulting in significant benefits for numerous patients. However, many patients are not responsive, become refractory, or cannot tolerate the treatment due to toxicity or side effects, demonstrating the need for additional immunotherapies. Cytokines are a class of promising immunomodulatory proteins being explored as therapeutics, but their success has been limited due to their rapid clearance or pleiotropic properties. Classically known as ‘signal 3’ of an endogenous immune response, IL-12p70 is a heterodimeric cytokine comprising p35 and p40 subunits. When administered exogenously, IL-12 is a potent stimulator of the immune system and can have profound anti-tumor activity; however, the clinical use of IL-12 has been limited due to poor systemic tolerability. Therefore, developing an immunotherapy that can be systemically administered and improve the therapeutic index could capitalize on the potential clinical benefit of IL-12. Mural Oncology has developed an innovative approach to mitigate the toxicity of IL-12 by splitting the heterodimer into inactive p35 and p40 monomers. The individual subunits are separately fused to two non-competitive antibody fragments targeting a highly expressed tumor-associated antigen. The goal of this approach is to conditionally activate IL-12 preferentially in the tumor microenvironment (TME). This is achieved by sequential administration of the targeted subunits, which will drive assembly and activity of the IL-12 heterodimer primarily at the tumor site, reducing systemic exposure and thereby potentially reducing associated toxicities. To engineer the split IL-12 subunits, a structure-based rational design approach was used to remove the natural intra-molecular disulfide bond and generate variants that maintained affinity between the p35 and p40 monomers. The engineered subunits were characterized using analytical methods and screened for the pair with the strongest affinity. Additionally, the candidate pair was assessed for receptor binding and functional activity on human T cells through phosphorylation of STAT4 and secretion of IFN-γ. Pharmacokinetics and pharmacodynamics were evaluated in mouse models with and without tumors demonstrating that dual targeting led to an increase in tumor retention, rapid clearance from circulation, and dose dependent release of IFN-γ. The results thus far demonstrate that the innovative approach of tumor targeted self-assembling split IL-12 has the potential to enhance the overall therapeutic potential of this cytokine. A development candidate will be identified and moved into clinical testing in cancer patients to enable us to fully understand if this design approach holds true in the clinical setting. Citation Format: Joshua Heiber, Pinar Gurel, Robert G. Newman, Kristiana Dreaden, Yanchun Zhao, Chunhua Wang, Su-Ping Pearson, Jean Chamoun. Generation of tumor targeted self-assembling split IL-12 subunits for the treatment of cancer 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 (6Suppl): Abstract nr 4066.