Results from trials such as Dédée Murrell, BMBCh, MD, pointed out at the EB World Congress, organized by the Dystrophic Epidermolysis Bullosa Association (DEBRA)., with allantoin, and , with diacerein, were “disappointing,”
Those two topical agents were most likely let down by the trials’ design, said Dr. Murrell, of St. George Hospital, University of New South Wales, Sydney, but she noted that there were still some promising trials that were either ongoing, such as, with Oleogel-S10, or that were about to be unblinded, such as SISTERS, with sirolimus.
Epidermolysis bullosa (EB) is a group of rare genetic diseases that can cause the skin to blister and peel away to varying degrees, causing itchy and painful skin, as well as recurrent wounds, some of which may seem never to heal and that increase the risk for squamous cell carcinoma. Although finding a cure for the disease is high on the research agenda, finding a reliable therapy that can soothe and protect the skin is of equal importance.
Trials and tribulations
Conducting trials in rare diseases can be difficult because the studies are often small and poorly controlled, Dr. Murrell said during an oral presentation at the meeting. To gain regulatory approval, trials need to have an active and a placebo arm, because “even though we’re dealing with a rare disease, we still have to show statistical significance between the two arms.”
However, it is not just about finding enough participants who meet the inclusion criteria and adequately controlling the study, as finding funding can also be a significant hurdle. That is the case particularly when an existing drug with no patent protection is proposed to be repurposed. As an example, Dr. Murrell said that many patients with EB may use gentian violet to treat their condition, but it has been around for so long and is so widely used, that funding a trial to formally prove its merit is unlikely. In addition, “there are special caveats that occur in dermatology clinical trials with topical drugs that don’t exist [in trials] with systemic treatments, one of which is that it is very important to keep other variables the same,” Dr. Murrell said. “So, for example, the dressings need to stay the same throughout a trial with a topical therapy, because if you improve the dressings [during the course of the trial], you could mask the effect of the treatment.” Similarly, the bathing and cleansing routines of the participants need to remain the same throughout the trial.
“We also need to have validated instruments to prove whether these treatments are working, and the instruments need to be objective as well as subjective,” Dr. Murrell advised. For example, inflammation and blistering need to be scored separately from scarring and skin damage. “You have to conduct a clinical trial to be able to verify that there is diminished scarring or damage, because those are the longer-term complications.” Inflammation and blistering are valid endpoints to use in shorter-term studies.
Dr. Murrell also cautioned on getting too enthused about the results of case reports. “We do get excited when we see a patient using something new and they seem to be getting much better,” but such reports do not have a placebo arm, or, if there is one, then there is no vehicle control, she said. It’s important to include a run-in period in a trial to establish a new baseline and to ensure that any effects seen with a topical agent are independent of the carrier substance or any altered bathing behavior or dressing habits, which could skew the results.