Development of antisense oligonucleotides that enhance sIL7R as novel cancer immunotherapy

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PROJECT SUMMARY Immunotherapy, which is designed to unleash the immune system to attack and kill cancer cells, holds enormous promise for the treatment of cancer. Such promise was recognized by the 2018 Nobel Prize in Medicine or Physiology awarded to Drs. James P. Allison (UT MD Anderson Cancer Center) and Tasuku Honjo (Kyoto University) for their discovery of cancer therapy by inhibition of negative immune regulation. Immune check point inhibitors, such as monoclonal antibodies that target the negative immune regulators CTLA-4 and PD-1 have gained FDA approval for several types of cancer. Exemplifying their potential, the anti-CTLA-4 monoclonal antibody Ipilimumab (Yervoy, Bristol Myers Squibb) was approved in 2011 for the treatment of melanoma and subsequently for other types of cancer. Likewise, anti-PD1 monoclonal antibodies Pembrolizumab (Keytruda, Merck) and Nivolumab (Opdivo, Bristol Myers Squibb) were also approved for melanoma and later for other types of cancers. Some results with these biologics have been very impressive. However, the promise of immunotherapy has been limited by the fact that in many patients there is no response. Potential pro-immune modulators with potential to boost response rate to immunotherapy have emerged from our work on autoimmunity. This work has led us to discover that soluble interleukin-7 receptor (sIL7R) is a driver of autoimmunity, which is usually not a desirable outcome, but in the context of immuno-oncology it could enhance anti-cancer immunity either alone or synergistically with immune checkpoint inhibitors. In this proposal, we test the hypothesis that increasing levels of sIL7R, a driver of autoimmunity, will lead to enhanced immune- reactivity and thus improved anti-cancer immunity. Given that sIL7R is produced by alternative splicing of the sixth exon of IL7R pre-mRNAs, specifically by exclusion of this exon, its expression can be controlled using splicing-modulating antisense oligonucleotides (ASOs). To increase sIL7R levels we generated two ASOs, IL7R- 001 and IL7R-004, that increase exclusion of IL7R exon 6 and production of sIL7R (pro-sIL7R ASOs). IL7R expression is largely restricted to T cells, and thus this cell type is the main producer of sIL7R. We have optimized delivery of these ASOs into human primary T cells in vitro, which will facilitate in vitro testing in this proposal and is critical for subsequent in vivo efficacy studies. As proof-of-concept, here we will test in vitro whether pro-sIL7R ASOs can modulate T cell function and enhance T cell-mediated killing of cancer cells. If pro-sIL7R ASOs enhance anti-cancer immunity in vitro, in Phase II we will test their anti-cancer therapeutic potential in a highly relevant, genetically-induced hepatocellular carcinoma model in baboons (Papio anubis). This model developed by our collaborators at the Southwest National Primate Research Center (San Antonio, TX), is one of the first experimentally tractable models of cancer in nonhuman primates and an ideal model for in vivo testing of immunotherapy candidate drugs, such as pro-sIL7R ASOs.