Design of de novo interleukin mimics for targeted immunotherapy

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PROJECT SUMMARY Although immunostimulatory cytokines can be used to combat cancer, their poor stability and high off-target toxicity has limited their application in the clinic. The ​long-term goal of this project is to produce targeted anti-cancer cytokine mimetics with reduced toxicity. The ​overall objective is to apply recent breakthroughs in ​de novo protein design to yield a new category of targeted, non-toxic, immunostimulatory proteins. The ​central hypothesis is that the beneficial stimulatory effects of natural cytokines can be engineered into ​de novo designed proteins which do not engage in off-target binding, thereby circumventing the dose-limiting toxicities seen in clinical applications of natural/reengineered cytokines. The ​specific aims are to: (1) use ​de novo protein design to generate hyperstable, bioactive mimetics of interleukin-2, -4, -12, -15, and -21 which function by engaging with (i.e. binding to) interleukin receptors ​in vivo​; (2) to split these mimics into inactive parts which can regain activity by reassembling ​in vivo​; and (3) to fuse each of these inactive parts to specific targeting domains, thereby yielding conditionally-active cytokine mimics that stimulate T-cells by reassembling only on the surface of a targeted cells (i.e. cancer cells displaying two specific surface biomarkers). ​As proof of principle​, the first such ​de novo designed cytokine mimetic has been produced, split, and shown to reduce tumors in mice without accompanying toxicity or immunogenicity. This research proposal is ​innovative because it seeks to resolve a long-standing barrier to cancer immunotherapy (namely, the off-target toxicity of cytokine-based therapeutics) by designing from scratch a new class of non-toxic cytokine mimics. The proposal is ​significant because it would be the first example of computational protein design yielding targeted, biosuperior cancer therapeutics. Ultimately, such molecules have the potential to treat a wide range of cancers, including malignant melanoma, renal cell carcinoma, and more.