A UV-Independent Topical Small-Molecule Approach for Melanin Production in Human Skin

The presence of dark melanin (eumelanin) within human epidermis represents one of the strongest predictors of low skin cancer risk. Topical rescue of eumelanin synthesis, previously achieved in “redhaired” Mc1r-deficient mice, demonstrated significant protection against UV damage. However, application of a topical strategy for human skin pigmentation has not been achieved, largely due to the greater barrier function of human epidermis. Salt-inducible kinase (SIK) has been demonstrated to regulate MITF, the master regulator of pigment gene expression, through its effects on CRTC and CREB activity. Here, we describe the development of small-molecule SIK inhibitors that were optimized for human skin penetration, resulting in MITF upregulation and induction of melanogenesis. When topically applied, pigment production was induced in Mc1r-deficient mice and normal human skin. These findings demonstrate a realistic pathway toward UV-independent topical modulation of human skin pigmentation, potentially impacting UV protection and skin cancer risk. [Display omitted] •SIK inhibitors induce MITF, the master regulator of pigment genes in vitro•Topical SIK inhibitor treatment of redhead mice rescues melanin production•Human skin-permeable SIK inhibitors induce melanin production in human skin explants Mujahid et al. describe the successful generation of topical small molecules capable of inducing dark pigmentation in human skin, thus potentially generating a variety of new applications.