Drug Discovery and Development

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Core B: Project Summary: The overall goal of this multi-disciplinary, multi-site PPG application is to build a firm foundation of discovery science in cellular senescence that leads to a pipeline of therapeutic strategies that slow or prevent age-associated diseases. Each of the four PPG Projects focus on the role of senescent cells in specific age-related health outcomes: Project 1, Metabolic Dysfunction (Kirkland/Tchkonia); Project 2, Skeletal Fragility (Khosla/Farr); Project 3, Vascular Dysfunction (Miller); and Project 4, Skeletal Muscle Loss and Dysfunction (LeBrasseur). To establish cause and effect, each project will use genetic and pharmacologic approaches to ablate senescent cells. Importantly, we have already established that senolytics, drugs able to induce apoptosis specifically of senescent cells, have cell-type specificity, such as working in adipocytes and not in endothelial cell, or vice versa. The Drug Discovery and Development Core (DDDC) will work with the other three cores to assist all four projects with the identification of the most effective senotherapeutics for their cell types of interest. The DDDC has developed multiple assays based on primary murine and human cells for screening and optimizing senotherapeutic compounds and drug combinations. Examples of senolytics and senomorphics (drugs that inhibit the senescence-associated secretome) identified by the DDDC include inhibitors of BCL-2 family members, the combination of dasatinib plus quercetin, HSP90 inhibitors, the flavonoid fisetin, rapamycin, inhibitors of IKK/NF-κB, JAK inhibitors, multimeric resveratrol and mitochondrial- targeted free radical scavengers. No one senotherapeutic compound has proven effective in clearing or modulating all senescent cell types. In addition, given that many of the senolytics identified to date are FDA approved anti-cancer drugs, it is likely that their senolytic activity as well as their cell-type specificity can be improved by medicinal chemistry. Thus, the essential role of the DDDC is to develop and implement assays for measuring senotherapeutic activity in the cells types of murine, rat and/or human cells as needed for the four projects. Mouse, rat and/or human cells will be induced to undergo senescence through different mechanisms, including oxidative and genotoxic stress, replicative senescence and treatment with senescent cell conditioned media, as deemed most appropriate to the cell type of interest and its normal physiology in vivo. 2D and 3D senescent cell culture assays will be developed and utilized for use in both primary and secondary screens. These assays will be used for comparing existing senotherapeutics, screening novel compounds, and testing analogs of known senotherapeutics for improved activity. In addition, the DDDC will provide DMPK analysis of senotherapeutic compounds for determining drug stability and distribution in young and old mice to assist each project in determining the right dosing regimen for their proposed experiments. Finally, the Core will validate the ability of the identified compounds to reduce the senescent cell burden in vivo using mouse models of accelerated aging carrying p16INKA and p21Cip1 reporters of cellular senescence.