SAN DIEGO – Twelve years ago, Merete Haedersdal, MD, PhD, and colleagues published data from a swine study, which showed for the first time that the ablative fractional laser can be used to boost the uptake of drugs into the skin.
That discovery paved the way for what are now well-established clinical applications of laser-assisted drug delivery for treating actinic keratoses and scars. According to Dr. Haedersdal, professor of dermatology at the University of Copenhagen, evolving clinical indications for laser-assisted drug delivery include rejuvenation, local anesthesia, melasma, onychomycosis, hyperhidrosis, alopecia, and vitiligo, while emerging indications include treatment of skin cancer with PD-1 inhibitors and combination chemotherapy regimens, and vaccinations.
During a presentation at the annual conference of the American Society for Laser Medicine and Surgery, she said that researchers have much to learn about laser-assisted drug delivery, including biodistribution of the drug being delivered. Pointing out that so far, “what we have been dealing with is primarily looking at the skin as a black box,” she asked, “what happens when we drill the holes and drugs are applied on top of the skin and swim through the tiny channels?”
By using high-performance liquid chromatography (HPLC) and HPLC mass spectrometry to measure drug concentration in the skin, she and her colleagues have observed enhanced uptake of drugs – 4-fold to 40-fold greater – primarily in ex vivo pig skin. “We do know from ex vivo models that it’s much easier to boost the uptake in the skin” when compared with in vivo human use, where much lower drug concentrations are detected, said Dr. Haedersdal, who, along with Emily Wenande, MD, PhD, and R. Rox Anderson, MD, at the Wellman Center for Photomedicine, at Massachusetts General Hospital, Boston, authored a clinical review, published in 2020, on the basics of laser-assisted drug delivery.
“What we are working on now is visualizing what’s taking place when we apply the holes and the drugs in the skin. This is the key to tailoring laser-assisted uptake to specific dermatologic diseases being treated,” she said. To date, she and her colleagues have examined the interaction with tissue using different devices, including ex vivo confocal microscopy, to view the thermal response to ablative fractional laser and radiofrequency. “We want to take that to the next level and look at the drug biodistribution.”
Efforts are underway to compare the pattern of drug distribution with different modes of delivery, such as comparing ablative fractional laser to intradermal needle injection. “We are also working on pneumatic jet injection, which creates a focal drug distribution,” said Dr. Haedersdal, who is a visiting scientist at the Wellman Center. “In the future, we may take advantage of device-tailored biodistribution, depending on which clinical indication we are treating.”
Another important aspect to consider is drug retention in the skin. In a study presented as an abstract at the meeting, led by Dr. Wenande, she, Dr. Haedersdal, and colleagues used a pig model to evaluate the effect of three vasoregulative interventions on ablative fractional laser-assisted 5-fluororacil concentrations in in vivo skin. The three interventions were brimonidine 0.33% solution, epinephrine 10 mcg/mL gel, and a 595-nm pulsed dye laser (PDL) in designated treatment areas.
“What we learned from that was in the short term – 1-4 hours – the ablative fractional laser enhanced the uptake of 5-FU, but it was very transient,” with a twofold increased concentration of 5-FU, Dr. Haedersdal said. Over 48-72 hours, after PDL, there was “sustained enhancement of drug in the skin by three to four times,” she noted.
The synergy of systemic drugs with ablative fractional laser therapy is also being evaluated. In a mouse study led by Dr. Haedersdal’s colleague, senior researcher Uffe H. Olesen, PhD, the treatment of advanced squamous cell carcinoma tumors with a combination of ablative fractional laser and systemic treatment with PD-1 inhibitors resulted in the clearance of more tumors than with either treatment as monotherapy. “What we want to explore is the laser-induced tumor immune response in keratinocyte cancers,” she added.
“When you shine the laser on the skin, there is a robust increase of neutrophilic granulocytes.” Combining this topical immune-boosting response with systemic delivery of PD-1 inhibitors in a mouse model with basal cell carcinoma, she said, “we learned that, when we compare systemic PD-1 inhibitors alone to the laser alone and then with combination therapy, there was an increased tumor clearance of basal cell carcinomas and also enhanced survival of the mice” with the combination, she said. There were also “enhanced neutrophilic counts and both CD4- and CD8-positive cells were increased,” she added.
Dr. Haedersdal disclosed that she has received grants or research funding from Lutronic, Venus Concept, Leo Pharma, and Mirai Medical.