An innovative proof-of-concept approach to identify age-modulating drugs capable of reversing inflammation and re-setting the epigenetic clock

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ABSTRACT In order to identify drugs and/or interventions with the potential to delay the onset and progression of age- associated pathologies, preclinical studies have used animal models where extension of lifespan could be accurately assessed. Several outstanding candidate therapeutics have been identified over the last decade; these include mTOR inhibitors (like rapamycin), senolytic agents, acarbose, and others. However, translating anti-aging results from animal models into humans has been challenging. For example, measuring extension of lifespan would be impractical in humans, so it is necessary to identify and validate parameters that can serve as surrogate markers of healthy aging. Moreover, the efficacy of age-modulating drugs is often only demonstrable with older individuals where functional deficits are already evident. Thus, testing of potential anti- aging therapeutics should be done in a cohort of human subjects of an advanced age; issues of safe administration would be even more acute in this “at risk” population. To circumvent these limitations, we propose to develop and validate an innovative, minimally invasive, cost-effective assay in human subjects ranging from 65-95 years old. The putative anti-aging test drug will be applied topically to a discrete area of skin on the subject’s forearm while a “vehicle only” (control) is applied in parallel to the opposite arm. Thus, each subject will serve as his/her own control. The pharmacodynamic outcomes at the “test” and placebo sites will be compared in both males and females since the effects of age-modulating agents often differ between the sexes. Ascertaining the efficacy of topically-applied therapeutics requires robust biomarkers of aging that can be measured in skin, but will be generalizable to the intact organism. Towards this end, we have opted to use two independent parameters that are known to be modified with aging both locally (in individual tissues) and systemically: i) the DNA methylation pattern or “epigenetic clock” and ii) biomarkers associated with inflammation. To validate the proposed technique, we have chosen a drug, rapamycin (RAPA), which has already been shown to modulate aging in rodents and which has been tested for safe systemic application in humans [1-4]. After a 6 month treatment phase, suction blisters will be generated at each site to allow collection of skin cells (blister flap) for use in the epigenomic analysis (Aim 1) and interstitial (blister) fluid for use in measuring cytokines and other inflammatory regulators (Aim 2). Once validated, our approach can be used to safely and efficiently screen the age-modulating potential of pharmacological agents in humans to identify those agents that warrant large, expensive human clinical trials with systemic agent administration.