Ablative fractional laser alters biodistribution of ingenol mebutate in the skin

Topically applied ingenol mebutate (IngMeb) is approved for field-treatment of actinic keratosis and is currently being investigated for treatment of non-melanoma skin cancer (NMSC). Ablative fractional lasers (AFXLs) generate microscopic ablation zones (MAZs) in the skin, which may help induce a deep penetration needed for effective treatment of NMSC. Using Franz diffusion cells, uptake and bio-distribution were investigated over 21 h in intact (n = 9) and AFXL-exposed porcine skin (n = 58). A 2940-nm fractional Er:YAG laser generated intraepidermal (11.2 mJ/MAZ; 66 μm deep, 177 μm wide) and intradermal (128 mJ/MAZ; 570 μm deep, 262 wide) MAZ’s with 16, 97, and 195 MAZs/cm². Surface ablation densities corresponded to 0.5, 2.5, and 5 % for intraepidermal MAZs, and corresponded to 1, 5, and 10.5 % for intradermal MAZs. Liquid-chromatography–mass-spectrometry quantified deposition of IngMeb in stratum corneum, epidermis, dermis, and receiver chamber. In intact skin, IngMeb readily penetrated to the epidermal layer (1,314 ng, 41 % of the applied IngMeb), while dermal deposition was limited (508 ng, 16 %). In AFXL-exposed skin, a profound dermal deposition of IngMeb was achieved, while less accumulated in SC and epidermis. Uptake depended entirely on laser density; increasing coverage from 0 % to 0.5 %, 1 %, 2.5 %, 5 %, and 10.5 % enhanced dermal uptake 1.6-, 2.1-, 3.1-, 3.4-, and 3.9-fold, respectively (p < 0.0001). Channel depth did not influence drug uptake; at 5 % density, dermal deposition with intraepidermal and intradermal MAZs was analogous (1801 vs. 1744; p = 0.447). In conclusion, IngMeb readily distributes to superficial layers of intact skin, whereas dermal uptake is limited. Independent of channel depth, AFXL enhances dermal drug deposition, providing for customized topical delivery and potential use of IngMeb for treatment of NMSC.