Allergen Inc has launched Aczone, a topical gel formulation of the antibacterial, anti-inflammatory agent dapsone, for the potential treatment of acne vulgaris. Oral dapsone has demonstrated efficacy in acne, but was associated with severe side effects such as anemia, which was particularly serious in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Aczone was developed to overcome this limitation, and is formulated using solvent-microparticle technology for improved absorption and action and for fewer side effects. In a phase I clinical trial, systemic exposure to dapsone was 126-fold lower following treatment with Aczone compared with oral dapsone. Aczone significantly reduced lesion counts in patients with acne in phase III trials, and was particularly effective in reducing inflammatory lesions. In a phase IV trial, Aczone was safely applied to patients with G6PD deficiency without inducing anemia. Phase IV trials in patients with acne were ongoing at the time of publication to assess safety and to compare Aczone monotherapy with combinations of Aczone and other anti-acne therapeutics. At the time of publication, Allergen was also developing Aczone for the treatment of rosacea; the drug was undergoing phase II trials for this indication. Aczone appears to be a novel promising anti-acne therapeutic option, particularly for patients with inflammatory acne.