The new frontier of atopic dermatitis
The approval in 2017 of dupilumab (Dupixent), a monoclonal antibody that inhibits the signaling of both IL-4 and IL-13) for moderate-severe atopic dermatitis (AD) in adults illustrates the new standing of dermatologic diseases in the field of drug development and commercialization. “Atopic dermatitis had always been the forgotten chronic disease in dermatology. … We’ve had no good treatments,” said Eric Simpson, MD, professor of dermatology at Oregon Health & Science University, Portland. “Dupilumab coming to the forefront [as a dermatology-first indication] has changed the entire perspective of the field. … Everyone is now trying to find the next best drug.”
Dr. Eric Simpson
As with psoriasis, a targeted therapy for AD was made possible by the development in the 1990s of monoclonal antibody technology and the ensuing ability to create biologics that target specific molecules in the body – as well as bedside-to-bench research that homed in on the involvement of particular cytokines.
But there also is a “new understanding of the burden of the disease,” Dr. Simpson observed. In the last 5 years, he said, research funded by the National Eczema Association documented that AD “not only causes inflammation of the skin … but that it affects people at school and in the workplace, that people have multiple mental health comorbidities and skin infections, and that the disease profoundly affects the entire patient in ways that weren’t really recognized or appreciated.”
Having evolved in the footsteps of psoriasis, AD is at a higher starting point in terms of the safety and efficacy of its first biologic, sources said. On the other hand, AD is a much more complex and heterogeneous disease, and researchers are trying to determine which immune pathways and cytokines are most important – and in which populations.
“We’re at the beginning. We’re trying to figure out how to get 80% of patients clear or almost clear [as we can now with psoriasis biologics] rather than almost 40% [as in the dupilumab pivotal trials],” said Dr. Simpson, former cochair of the National Eczema Association’s scientific committee. Public data from ongoing phase 2 and 3 trials of other Th2 cytokine inhibitors suggest that 25%-45% of enrolled patients achieve high levels of clearance, he noted.
Emma Guttman-Yassky, MD, PhD, Sol and Clara Kest Professor and vice-chair for research in the department of dermatology at the Icahn School of Medicine at Mount Sinai, New York, said that AD’s heterogeneity involves “many factors, like ethnicity, age … and whether they have an atopic background such as asthma.”
Bruce Jancin/MDedge News
Dr. Emma Guttman-Yassky
Her research is showing, for instance, that AD in Asian and black patients is different than AD in European-American patients, and that the presence of comorbidities may well have treatment implications. She has also shown that children may have a different phenotype than adults, with greater activation of the Th17 axis that typifies psoriasis.
“For certain patients, we may need to target more than one pathway, or target a different pathway than the Th2 pathway. And treatment may be different in the setting of comorbidities,” said Dr. Guttman-Yassky, who is also director of the laboratory of inflammatory skin diseases at Mount Sinai. “We may think of one treatment – dupilumab, for example – for someone who has asthma and AD. But for patients who don’t have asthma and are Asian, for instance, or for children, we may need additional agents.”
Her research over the years on AD has taught her the importance of human studies over mouse model studies; it was in humans, she noted, that she and other investigators demonstrated “without doubt” that AD is an immune disease and not simply a barrier disease. The Th2 cytokine pathway appears to play the predominant role in AD, though “there still is a strong Th1 component,” she said.
“We’re in a better position to figure this out today [than in the past 20 or even 10 years],” said Dr. Guttman-Yassky, who recalls being told years ago that AD was a “dead end,” that it “would kill [her] career.” Given the evolution of science and the recognition of comorbidities and seriousness of dermatologic diseases, “the stars are aligned to get more [therapies] to these patients.”
Janus kinase (JAK) inhibitors are among these therapies. Three JAK inhibitors are in or have recently completed phase 3 studies for AD; two are currently approved for rheumatoid arthritis, and the other has been designed specifically for AD, Dr. Simpson pointed out. The drugs are oral small molecule drugs that block the JAK signaling pathways for certain proinflammatory cytokines.
“The JAK inhibitors are a real exciting story for dermatology,” he said. “Theoretically, by blocking more cytokines than biologics do, there could be some safety issues – that’s why we’re awaiting big phase 3 study results so we can figure out the risk-benefit balance and guide our patients as to which drug is best.”
Andrew Blauvelt, MD, MBA, president of Oregon Medical Research Center in Portland – a stand-alone dermatology clinical trial center founded in 1998 – likes to envision the evolution of drugs for dermatologic conditions as a funnel, with the most broad-acting drugs at the wide top of the funnel and the most targeted drugs at the bottom tip.
Dr. Andrew Blauvelt
JAK inhibitors, he said, sit near the middle – more targeted and safer than cyclosporine and methotrexate, for instance, but not as targeted as the biologics now available for psoriasis and being developed for AD. “The oral medications that have been developed for psoriasis and those coming for AD are not quite as targeted to the disease,” he noted. “JAK inhibitors have great efficacy – it’s more a question of safety and being able to treat without causing collateral damage.”
Dr. Blauvelt expects the armamentarium of new drugs approved for AD to go from one (dupilumab) to seven within the next 2 years. This will include three new biologics and three new oral JAK inhibitors, he predicts. As the specialty sorts through and integrates these new drugs into practice, dermatologists will increasingly personalize treatment and will face the “nonscientific” challenge of the cost of new therapies and patient access to them, he noted.
In the meantime, said Dr. Simpson, recent drug discoveries have driven more non–pharmaceutical-funded translational research aimed at understanding the underlying biology of AD. The National Institutes of Health, for instance, “is interested in dupilumab and its impact on the skin barrier and skin defense mechanisms,” he said. “We’ll learn a lot more [in coming years].”