Blazing new trails

May 01, 2007, 4:00am

The quest for innovative new photoprotection options includes exploration of antioxidants and DNA repair enzymes as well as research into melanocyte-stimulating hormones. Research shows that melanin increases in Caucasian patients following injections of alpha-melanocyte-stimulating hormone (alpha-MSH), which is released from the pituitary gland to induce the production of melanin following UVB exposure.

Key Points

The biggest news in recent years was the Food and Drug Administration's 2006 approval of Mexoryl, a highly photostable ingredient that offers long-lasting and complete broad-spectrum UV protection. The protection includes short-wavelength UVA rays (320 nm to 340 nm).

"We are excited about Mexoryl SX, because it really is a very stable sunscreen and has great UVA protection," says Elma D. Baron, M.D., assistant professor of dermatology and director of the Skin Study Center at Case Western Reserve University, Cleveland. "There aren't many other filters that can limit that range of absorption of UVA, so we know this will be a good sunscreen."

The product, which combines Mexoryl SX (ecamsule) with L'Oréal's patented association of avobenzone (Parsol 1789), has an SPF rating of 15 and a UVA protection value of 15 based on persistent pigment darkening testing.

Little patient enthusiasm

Despite the enthusiasm among dermatologists over Mexoryl, Dr. Baron tells Dermatology Times she has yet to see the excitement rub off on patients.

"I haven't seen any big sign that it's on the market and I actually don't think any of my patients have used the product," she says.

Meanwhile, as researchers push toward other approaches to photoprotection, one of the most innovative areas is that of melanin-inducing drugs. A team in Australia has made headway with its work on the alpha-melanocyte-stimulating hormone (alpha-MSH), which is released from the pituitary gland to induce the production of melanin following UVB exposure.

In a study of 65 Caucasian subjects, researchers with the Royal Prince Alfred Hospital at the University of Sydney, Australia, reported that subcutaneous injection of a potent synthetic melanotropin (alpha-MSH) in the abdomen for three 10-day cycles over three months was linked to significant increases in melanin density (J Invest Dermatol. 2006 Aug;126(8):1869-1878).

The greatest changes were seen among subjects with the lowest baseline skin melanin levels. Subjects with the low minimal erythemal dose skin (MED) type showed average melanin increases of 41 percent (from 2.55 to 3.59, P < 0.0001 vs. placebo), compared with increases of only 12 percent (from 4.18 to 4.70, P < 0.0001 vs. placebo) in subjects with a high MED skin type, the researchers reported.

In addition, epidermal sunburn cells resulting from exposure to three MED of UV radiation were reduced by more than 50 percent after MSH treatment in the subjects with low baseline MED. Thymine dimer formation was also shown to be reduced by 59 percent (P = 0.002) in the epidermal basal layer.

"This study has shown for the first time the potential ability of a synthetic hormone that augments melanin production to provide photoprotection to people who normally burn in direct sunlight," the researchers report.

Other research shows promise

In other photoprotection developments, DNA-repairing enzymes are gaining notice as means for skin repair following sun damage.

AGI Dermatics is working on getting FDA approval for its Dimericine product, billed in the media as a "morning-after" skin repair product for sun damage. While the company awaits the approval, it has released a seven-product skin line called Remergent, which it says works in a "similar" manner to target DNA repair, barrier rebuilding and pigmentary issues.