Application of a topical photoparticle immediately before non-ablative 810 nm diode laser treatment for acne resulted in a statistically significant reduction from baseline in inflammatory acne counts on the back, according to a small feasibility study presented in April at the annual conference of the American Society for Laser Medicine and Surgery (ASLMS) in San Diego.
“One of the major challenges of acne treatment is patient compliance,” says investigator Sarah Schram, M.D., a dermatologic surgeon in private practice in Tucson, Ariz. “Teenagers, in particular, are not very good at using topical medications or remembering to take pills every day. There are also potentially serious adverse events associated with these therapies.”
The study authors were specifically interested in treatment of acne on the back because the back is fairly resistant to therapy.
“The back is also an area that is difficult for patients to apply cream,” Dr. Schram tells Dermatology Times. “Plus, people may need to be placed on oral medications that they wish to avoid.”
The study goal was use of an in-office procedure that could lead to improvement in acne vulgaris, without requiring such strict medication compliance.
“Use of a topical photoparticle could enhance laser treatment of acne by facilitating photothermal injury of the sebaceous follicles,” Dr. Schram says. “Patients also did not need to do treatments at home in-between.”
The study consisted of 11 subjects with back acne, of whom 11 were in the safety population and 10 in the intent-to-treat population. Six men and four women (mean age 26.5 years) participated in the efficacy interim analysis.
The blinded trial divided the back into two areas for treatment. One side of the back was treated with the photoparticle (Sienna Biopharmaceuticals) and the other side was not. Both sides received the same 810 nm diode laser treatment.
“We wanted to control to ensure that the laser treatment alone was not causing the improvement,” says Dr. Schram, who at the time of the study was a dermatologic surgeon at the University of Minnesota in Minneapolis.
The topical photoparticle is an extremely small silver particle “that can be tuned to basically increase absorption of the laser,” Dr. Schram says. The photoparticle was applied using a vibrating paddle to increase the penetration of the particles into the sebaceous glands and follicular units.
“These particles are designed to absorb more of the laser energy for more focused intense treatment to the desired target, which in this case is sebaceous glands,” Dr. Schram explains. “This is the same target as isotretinoin, which is currently the only acne therapy that provides long-term drug-free remission of acne in many patients.”
The particles were in a liquid suspension and massaged into the skin right before laser treatment. Excessive particles on the surface of the skin were washed off.
Patients received four laser treatments at weekly intervals and then were followed for three months.
The mean total lesion count on the back at baseline was 9.7, with a mean of 7.4 for inflammatory lesions.
At 12 weeks after the final laser treatment, both the control (laser only) group and the laser+photoparticle group achieved a mean percentage reduction in total lesion count: -45.5 for control vs. -62.8 for combined therapy.
To understand the impact of high peak power on lesion counts, the study analyzed a subgroup of six subjects who received at least one of four treatments with high peak power laser settings. In this subgroup, statistically significant reductions in both total and inflammatory lesion counts were observed for laser+photoparticle (-5.3 and -4.2, respectively), but not for control (-4.2 and -3.7, respectively).
The study findings do not surprise Dr. Schram.
“Based on the physics, it makes sense,” she says. “With a photoparticle, laser energy is delivered more precisely through the sebaceous glands and there is better absorption of the energy.”
Although, applying the photoparticle does add about 15 minutes to office time, she says.
On the other hand, the study found no treatment-related adverse events and no subject discontinued treatment or the study due to an adverse event.
“However, patients should expect local tolerabilities, including erythema, perifollicular edema and hypopigmentation, which are typical, transient side effects of laser therapy” Dr. Schram says.
Dr. Schram and her colleagues hope that ongoing larger clinical trials, which expand the use of the photoparticle to three commonly used lasers (810 nm, 755 nm, and 1064 nm), will confirm study results “so that a topical photoparticle with laser can be incorporated into standard practice with dermatologists’ existing install base of lasers,” she says.
Disclosure: Dr. Schram reports no relevant