Pharmacology of adapalene.

Adapalene, a synthetic retinoid, is a new drug proposed for the treatment of acne patients. Studies on the in vitro and in vivo pharmacology of adapalene have shown that it is very active on cell and tissue proliferation and differentiation. Furthermore, adapalene has anti-inflammatory potential as determined by its anti-AP1 activity. Adapalene interacts selectively with the nuclear receptors RAR beta and RAR gamma, and its activity on proliferation and differentiation can be blocked by a RAR beta-gamma antagonist. Because RAR beta is not expressed in human keratinocytes, the effect of adapalene on the major cell type of the epidermis is certainly mediated by its interaction with RAR gamma. The unique pharmacological properties of adapalene may explain why, when compared to tretinoin, it has an improved therapeutic ratio due to its better tolerance.