New gel launched for the treatment of acne

Sometime in the next year-when details are ironed out-QLT Inc., Vancouver, Canada, plans to launch Aczone (dapsone 5% gel) for the topical treatment of acne vulgaris. The product was approved in July, but QLT is pondering how best to work with the labeling required by the Food & Drug Administration. "We might wait [to launch] until we have phase IV data," said Mohammed Azab, M.D., chief medical officer of QLT. Phase IV trials evaluating this issue are slated to begin this year.

While the gel's mechanism of action in acne is unknown, Azab believes its efficacy results from the drug's proven anti-inflammatory and antibacterial properties. "There are three driving factors in the pathogenesis of acne: increased sebum production, bacterial infection, and inflammation," he said. "Topical dapsone may well address two of these three factors. Existing products typically combine a drying agent with an antibacterial agent."

Because of its concern over the safety of topical dapsone-based on the safety of oral dapsone-the FDA has issued a labeling requirement that patients need to be screened for G6PD deficiency, and patients with this deficiency must be monitored by regular blood counts. "Dapsone is known for its potential side effect of hemolysis, especially in patients with certain common enzyme deficiencies like G6PD," Azab said. So despite very clean data, the FDA is requiring labeling that mandates screening of patients for G6PD deficiency. (In the clinical trial program, 1.4% of 3,500 patients had G6PD deficiency, a percentage consistent with the incidence of G6PD deficiency in the North American population.) Azab noted, however, that "the FDA left the door open for us to conduct a phase IV study that treats G6PD patients, and, if we show that the product is safe in those patients compared with vehicle, then it is willing to reconsider that requirement." That study will soon be under way.

QLT is also evaluating dapsone gel in conjunction with other acne therapy. "Following our submission, we conducted a randomized, controlled phase IIIB study in which we added a drying agent to dapsone gel therapy. Using dapsone gel with a drying agent should affect the factors that contribute to acne: inflammation, infection, and sebum production. We will be reporting these data before the end of the year," Azab concluded.

Kathy Hitchens is a medical writer based in Indiana.