, according to an expert speaking at the annual Coastal Dermatology Symposium, held virtually.
Dr. Neal Bhatia
This relationship is not new. In a review of treatments for AKs, Neal Bhatia, MD, a dermatologist and researcher at Therapeutics Dermatology, San Diego, advised that most effective agents trade a higher risk of inflammatory reactions – including erythema, flaking, and scaling – for greater therapeutic gain. In many cases, local skin reactions are an inevitable consequence of their mechanism of action.
Data from the completed phase 3 trials of tirbanibulin 1% ointment (KX01-AK-003 and KX01-AK-004), are illustrative. (Tirbanibulin 1% ointment was approved by the Food and Drug Administration in mid-December, after the Coastal Derm meeting was held.)
In the phase 3 trials, which have not yet been published, tirbanibulin, an inhibitor of Src kinase, which has an antiproliferative action, was four to five times more effective than vehicle by day 57 for overall complete clearance (P < .0001) of AKs and complete clearance of the face (P < .0001), but rates of local skin reactions were generally two to three times higher, according to Dr. Bhatia.
In the KX01-AK-004 trial, for example, 61% of patients had complete clearance of the face, versus 14% of those randomized to vehicle. The difference for overall partial clearance (76% vs. 20%; P < .0001), partial clearance of the face (80% vs. 22%; P < .0001), and partial clearance of the scalp (69% vs. 15%; P < .0001) was even greater. When compared with placebo, tirbanibulin was also associated with greater rates of erythema (90% vs. 31%), crusting (45% vs. 8%), flaking (84% vs. 35%), swelling (38% vs. 2%) and erosions or ulcers (12% vs. 1%).
Although these events might be a challenge with regard to tolerability for some patients, they might best be described as evidence that the drug is working.
“Local skin reactions are anticipated. They are not adverse events. They are not side effects,” Dr. Bhatia said at the meeting, jointly presented by the University of Louisville and Global Academy for Medical Education. “Patients are going to get red, and you need to counsel patients about the 5 days when they can expected to be red. It is a sign of the civil war, if you will, that your skin is taking on with the actinic keratoses.”
Both 3- and 5-day courses of the drug were tested in the clinical trials. (The approved prescribing information recommends treatment on the face or scalp once a day for 5 consecutive days).
Other studies evaluating treatments for AKs have also associated an increased risk of local skin reactions with greater efficacy, Dr. Bhatia noted. As an example, he cited a phase 4 study comparing 0.015% ingenol mebutate gel to diclofenac sodium 3% gel in people with facial and scalp AK lesions.
At the end of the 3-month study, complete clearance was higher among those on ingenol mebutate, which was applied for 3 days, when compared with diclofenac sodium gel, which was applied daily for 3 months (34% vs. 23%; P = .006). However, patients randomized to ingenol mebutate gel had to first weather a higher rate of application-site erythema (19% vs. 12%) before achieving a greater level of clearance.
The correlation between efficacy and local reactions at the site of treatment application emphasizes the importance of educating patients about this relationship and in engaging in shared decision-making, Dr. Bhatia said.
“It is basically a tradeoff between local skin reactions, between frequency [of applications], compliance, and, of course, duration of therapy, even though both drugs served their purposes well,” said Dr. Bhatia, referring to the comparison of the ingenol mebutate and diclofenac gels.
Although not absolute, efficacy and tolerability were also generally inversely related in a recent four-treatment comparison of four commonly used field-directed therapies. In that trial, the primary endpoint was at least a 75% reduction from baseline in the number of AKs to 12 months after treatment ended.
For that outcome, 5% fluorouracil (5-FU) cream (74.7%) was significantly more effective than 5% imiquimod cream (53.9%), methyl aminolevulinate photodynamic therapy (37.7%), and 0.015% ingenol mebutate gel (28.9%). Also, 5-FU treatment was associated with the moderate or severe erythema (81.5%), severe pain (16.%), and a severe burning sensation (21.5%).
Other therapies on the horizon, some of which are already available in Europe or Canada, show a relationship between efficacy and local skin reactions. Of two that Dr. Bhatia cited, 5-FU and salicylic acid combined in a solution and 5-FU and calcipotriene combined in an ointment have demonstrated high rates of efficacy but at the cost of substantial rates of erythema and flaking.
Transient skin reactions can be made acceptable to patients who are informed of the goals of clearing AKs, which includes lowering the risk of cancer, as well as cosmetic improvement. In the phase 4 study comparing ingenol mebutate gel to diclofenac sodium gel, the end-of-study global satisfaction rates were higher (P < .001) for those randomized to the most effective therapy despite the local skin reactions.
Preparing patients for the consequences of therapy for AKs is essential, because optimal therapy involves treating uninvolved skin, according to Hassan Galadari, MD, assistant professor of dermatology, United Arab Emirates University, Dubai. A coauthor of a recent review article on actinic keratoses, Dr. Galadari said in an interview that field treatment means patients might have local skin reactions where they did not previously have lesions.
“Actinic damage may not be visible with the naked eye. That is why field treatment, which is applying medicine in adjacent areas that may appear normal, is indicated,” he said. As a result, “areas that otherwise may have appeared as normal start to react by becoming red, itchy, and even inflamed.”
He agreed with Dr. Bhatia that local skin reactions are typically the price paid for effective control of these precancerous lesions.
This publication and Global Academy for Medical Education are owned by the same parent company.
Dr. Bhatia reports financial relationships with more than 30 pharmaceutical companies with dermatologic products, including Almirall and other companies with products relevant to AK therapies.