SAN FRANCISCO — Fair-skinned volunteers injected with synthetic α-melanin-stimulating hormone readily acquired tans and showed minimal epidermal damage following exposure to ultraviolet light, in a study unveiled at the annual meeting of the American Academy of Dermatology.
Dr. Ross Barnetson, the Raymond E. Purvess Professor of Dermatology at the University of Sydney (Australia) and the Royal Prince Alfred Hospital, both in Camperdown, New South Wales, reported on the experimental approach to sun protection during a special session highlighting exciting new trial data.
In his presentation, Dr. Barnetson explained that 79 Australian subjects, most of them fair-skinned women, were enrolled in a 3-month trial comparing subcutaneous abdominal injections of Melanotan, which is an analog of α-melanocyte-stimulating hormone (α-MSH), with a placebo.
Melanin density, which was measured in the skin of subjects by using spectrophotometry, was found to increase significantly in patients who received the α-MSH injections for 10 days a month for 3 months.
“What was fascinating was that … the patients with low baseline MED [minimal erythema dose]—that is, [Fitzpatrick] skin type I or skin type II—had much better responses than those with high MED,” Dr. Barnetson said during the session.
“It was a big surprise to us that, suddenly, people with red hair were getting a tan,” he added.
The patients who had low baseline MED scores demonstrated a 40% increase in melanin density over eight separate skin sites after being administered the hormone, compared with a 12% increase in those with high baseline MED scores.
Melanin density increases were seen not only in skin that was exposed to the sun but also in skin that was unexposed.
The investigators went on to measure epidermal changes following exposure of subjects to three times their baseline MED of solar-simulated ultraviolet rays, 90 days into the trial.
Compared with placebo, individuals with low baseline MED who were administered the hormone demonstrated a 50% reduction in epidermal sunburned (apoptotic) cells and nearly a 60% reduction in DNA damage, as measured by thymine dimer formation.
“Melanotan results in an increase in skin pigmentation, with the greatest increases in those with low MED, [for example] type I and II skin types,” Dr. Barnetson said in his conclusion.
“Clearly, it has the propensity to prevent cellular damage, as measured by sunburned cells and thymine dimers.”
In the short term, he said that the synthetic hormone may prove to be useful as a means of preventing photosensitizing diseases such as polymorphic light eruption. Early studies of the effect of the synthetic hormone on those diseases have been “very encouraging,” he noted.
In the long term, a product might be developed that could be used to prevent the development of skin cancer in individuals who are fair-skinned.
There are wrinkles that must be worked out before a commercial product can become a reality in the marketplace, however.
Dr. Barnetson noted that 12 of 59 patients assigned to the active treatment arm of the investigation dropped out because of flushing and nausea, which were adverse events associated with the Melanotan injections. A depot form of injection that was administered to subjects in a subsequent study appears to have ameliorated those side effects, he said.
An audience member asked Dr. Barnetson about the possibility of melanocyte proliferation in response to the injections.
Although that has not proven to be an issue, “there is some suggestion [Melanotan] could be immunosuppressive, so we have to think of the long term,” Dr. Barnetson replied.
In trials involving “quite a lot of subjects” who were administered the synthetic hormone, no case of melanoma has been diagnosed.
Melanotan is manufactured by the Melbourne (Australia)-based company Clinuvel Pharmaceuticals Ltd. (formerly Epitan Ltd.). Dr. Barnetson disclosed that he serves on the firm's medical advisory board.