Pivotal clinical trials of adapalene in the treatment of acne

Adapalene, a naphthoic-acid derivative, possesses some of the biological activities of tretinoin but has distinct physicochemical properties and binding properties for selective affinity for retinoic acid receptors. As such, adapalene is less likely to be associated with certain local tolerability problems (e.g. burning, erythema, pruritus). Over the past 5 years, numerous clinical trials have been conducted to compare the efficacy and tolerability of adapalene and tretinoin in the treatment of acne vulgaris. Three pivotal, large, well-controlled studies involving almost 900 patients showed that adapalene gel 0.1% and adapalene solution 0.1% are at least as effective as tretinoin gel 0.025%, with superior local tolerability. Adapalene cream 0.1% has proven to be significantly more effective than vehicle, with response rates comparable to those observed with the gel and solution. A meta-analysis of trials with the gel formulation confirmed these findings, showing equivalent efficacy and improved tolerability vs. tretinoin gel 0.025%. Moreover, the onset of clinical effect was shown to be significantly more rapid than that of tretinoin gel. Taken together, these studies demonstrated that adapalene has overall efficacy similar to that of topical tretinoin, but with a superior therapeutic ratio that may result in superior outcomes in clinical practice through improved compliance. This may be expected because of its lesser potential for skin irritation, especially early in treatment, and because of greater convenience in that no waiting period is required between face washing and application of the product. Therefore, 5 years of clinical experience have established that adapalene in its various formulations is a valuable addition to current treatments for acne vulgaris.