Phenotypic Screening Identifies Hydroxypyridone Anti-Fungals As Novel Medicines for the Prevention of Hypertrophic Scars

Although hypertrophic scarring affects similar to 91% of burn patients annually, there is no drug to prevent this common complication. Hypertrophic scars are a result of dysregulated wound healing, characterised by persistent myo-fibroblast transformation and the excessive accumulation of extracellular matrix (ECM). Due to the multi -mechanistic nature of the scarring process, target-based approaches for identifying novel drugs have failed. Primary human dermal fibroblasts, derived from burn scar tissue, were exposed to transforming growth factor -beta 1 (TGF-beta 1) to induce myofibroblast transformation. A phenotypic screening assay, measuring alpha-smooth muscle actin (alpha-SMA) expression, was developed to screen 1,954 approved drugs. Drugs that elicited >80% inhibition of alpha-SMA expression, and >80% cell viability were progressed as candidate drugs. Anti-myofibroblast activity of the candidates was confirmed before investigating their effects on extracellular matrix (ECM) pro-duction and keratinocyte epithelial-mesenchymal transition (EMT). TGF-beta 1 induced myofibroblast transformation in primary human dermal fibroblasts (Emax = >3 ng/mL). The assay was optimised and validated (Z' = 0.59), before screening 1,954 approved drugs. 90 drugs were identified as hits and hydroxypyridone anti-fungals selected for further testing. Concentration-response curves for these drugs confirmed their concentration-dependent anti-myofibroblast activity (IC50 = 1.4 - 16.7 mu M). Hydrox-ypyridone anti-fungals were also found to successfully reduce ECM production and keratinocyte EMT.This is the first study to screen approved drugs in primary human dermal fibroblasts. Hydroxypyridone anti-fungals were found to prevent myofibroblast transformation, ECM production and keratinocyte EMT suggesting they could be repurposed to prevent hypertrophic scarring.