By Mary Welch

Dusa Pharmaceuticals Inc. received an FDA approval letter for Levulan Photodynamic Therapy (PDT) for the treatment of multiple actinic keratoses of the face and scalp.

"We will be modifying our label and the FDA must re-inspect our manufacturing facilities, which should take place in the third quarter," said Stuart Marcus, senior vice president and chief scientific officer at Dusa. "We don't think those issues are any big deal. We expect we'll be in dermatologists' offices by the first quarter of next year.

The approval covers Dusa's 20% Levulan (aminolevulinic acid HCI) Kerastick applicator, and its Blu-U fluorescent tube illuminator. When delivered to target tissues, Levulan is taken up and converted by fast-growing cells into protoporphyrin IX (PplX), a potent photosensitizer, which then can be activated by an appropriate light source.

Actinic keratoses (AK) are common sun-induced precancerous skin lesions that occur primarily in fair-skinned individuals. Current treatments include liquid nitrogen (freezing) and 5-FU cream.

"Liquid nitrogen is quick and effective but it can cause the pigment to change and blister. The topical creams can be corrosive, which is painful and irritating," Marcus said. "In our studies, patients said they preferred Levulan. The only side effects were some stinging and burning during treatment, which lasts 16 minutes. We believe we are the first standardized therapy for this precancerous skin condition."

The Toronto-based company conducted two parallel Phase III trials at 16 U.S. sites involving 240 patients with between four and 15 AKs each. All patients received either 20% Levulan topical solution, or a placebo plus blue light.

In one study of 117 patients, 86 percent of those given a single treatment of Levulan had a complete response, with 94 percent responding after two treatments. In contrast, only 32 percent of the lesions cleared after two treatments of the placebo and light.

In the second study of 126 people, 81 percent had a complete lesion response with one Levulan treatment, with 90 percent having a complete response with two treatments. The placebo group showed a 20 percent clearance after two treatments.

The market potential is huge, Marcus said. "There are about 4 million visits to the dermatologist each year in the U.S. for this indication," he said. "We believe this could be a $100 million product."

The company will launch in the U.S. first and is seeking a multinational partner to help market it in Europe.

Dusa is actively pursing other applications for Levulan. It currently is in Phase I/II trials using Levulan PDT for hair removal. A Phase II study for acne should start soon. A Dusa-supported investigator-sponsored study of Levulan PDT for cervical intraepitheleal neoplasia (CIN) is under way at the University of California at Irvine. A Phase I/II trial using Levulan Photodetection is taking place with high-risk bladder cancer patients.

"We are looking at Levulan for a variety of indications, including oncology, gynecological and women's health issues, including as an adjuvant to a Pap smear," Marcus said. "It's almost like Levulan is like a Ginsu knife - it dices, slices, cuts, purees. We think it has potential for so many applications."