The use of Toll-like receptor-7 agonist in the treatment of basal cell carcinoma: an overview.

Basal cell carcinoma (BCC) is a subtype of nonmelanoma skin cancer (NMSC), with an increasing incidence worldwide. Currently, excision of the tumour with histological control is the standard therapy. However, high incidence rates have led to concern about the economic burden imposed by BCC management in many countries. Imiquimod is a member of a novel class of immune response modifiers (IRM), which works by using the toll-like receptor (TLR)-7. Although the exact mode of action is so far unknown, it is suggested to induce the expression of different cytokines like interleukin (IL)-1, IL-6, IL-12, interferon (IFN)-alpha and tumour necrosis factor (TNF)-alpha, which stimulate or enhance both the innate immune system and the cell-mediated immune response. Pre-clinical studies have indicated the potential of this TLR-7 agonist for the treatment of precancers and tumours in humans. A number of Phase II trials have demonstrated the efficacy of imiquimod for the treatment of BCC, although the most appropriate dosing regimen is being confirmed in Phase III studies. Imiquimod 5% cream for the treatment of mainly superficial BCC appears to be an effective and well-tolerated treatment option.