Anthralin-From Psoriasis Drug to Power Adjuvant.

Anthralin has a long history as a topical treatment for psoriasis, where it reduces keratinocyte hyper-proliferation and effectively clears plaques. While it lowers inflammatory markers in psoriatic skin, it paradoxically induces inflammation in healthy skin through reactive oxygen species (ROS) and related pathways. However, its precise mechanism of action remains incompletely understood. Interestingly, the once undesirable pro-inflammatory effect in healthy skin may now represent a valuable adjuvant property for transcutaneous immunization (TCI). In particular, combining anthralin with the TLR7 agonist imiquimod (IMQ) elicits strong cytotoxic T-cell responses in pre-clinical studies. When paired with antigenic peptides that can penetrate the skin, this immunization approach is especially promising in the context of cancer therapy, given the central role of cytotoxic T-cells in tumor rejection. However, current evidence is largely derived from mouse models, but its efficacy and safety in humans remain to be established. This review therefore examines whether anthralin can be repurposed as a cutaneous adjuvant for transcutaneous immunization, and which mechanistic and translational constraints must be overcome before human application.