Atopic dermatitis (AD) is an incredibly common chronic skin disease, affecting up to 25% of children and 7% of adults in the United States.1,2 Despite the prevalence of this disease and its impact on patient quality of life, research and scholarly work in AD has been limited until recent years. A PubMed search of articles indexed for MEDLINE using the term atopic dermatitis showed that there were fewer than 500 articles published in 2000 and 965 in 2010; with our more recent acceleration in research, there were 2168 articles published in 2020 and more than 1300 published in just the first half of 2021 (through June). This new research includes insights into the pathogenesis of AD and study of the disease impact and comorbidities as well as an extensive amount of drug development and clinical trial work for new topical and systemic therapies.
New Agents to Treat AD
The 2016 approval of crisaborole,3 a phosphodiesterase 4 inhibitor, followed by the approval of dupilumab, an IL-4 and IL-13 pathway inhibitor and the first biologic agent approved for AD,4 ushered in a new age of therapy. We currently are awaiting the incorporation of a new set of topical nonsteroidal agents, oral Janus kinase (JAK) inhibitors, and new biologic agents for AD, several of which have completed phase 3 trials and extended safety evaluations. How these new drugs will impact our standard treatment across the spectrum of care for AD is not yet known.
The emergence of new systemic therapies is timely, as the most used systemic medications previously were oral corticosteroids, despite their use being advised against in standard practice guidelines. Other agents such as methotrexate, cyclosporine, azathioprine, and mycophenolate are discussed in the literature and AD treatment guidelines as being potentially useful, though absence of US Food and Drug Administration (FDA) approval and the need for frequent laboratory monitoring, as well as drug-specific side effects and an increased risk of infection, limit their use in the United States, especially in pediatric and adolescent populations.5
The approval of dupilumab as a systemic therapy—initially for adults and subsequently for teenagers (12–17 years of age) and then children (6–11 years of age)—has markedly influenced the standard of care for moderate to severe AD. This agent has been shown to have a considerable impact on disease severity and quality of life, with a good safety profile and the added benefit of not requiring continuous (or any) laboratory monitoring.6-8 Ongoing studies of dupilumab in children (ClinicalTrials.gov identifiers NCT02612454, NCT03346434), including those younger than 1 year,9 raise the question of how commonly this medication might be incorporated into care across the entire age spectrum of patients with AD. What standards will there be for assessment of severity, disease impact, and persistence to warrant use in younger ages? Will early treatment with novel systemic agents change the overall course of the disease and minimize the development of comorbidities? The answers to these questions remain to be seen.
JAK Inhibitors for AD
Additional novel therapeutics currently are undergoing studies for treatment of AD, most notably the oral JAK inhibitors upadacitinib,10 baricitinib,11 and abrocitinib.12 Each of these agents has completed phase 3 trials for AD. Two of these agents—upadacitinib and baricitinib—have prior FDA approval for use in other disease states. Of note, baricitinib is already approved for treatment of moderate to severe AD in adults in more than 40 countries13; however, the use of these agents in other diseases brings about concerns of malignancy, severe infection, and thrombosis. In the clinical trials for AD, many of these events have not been seen, but the number of patients treated is limited, and longer-term safety assessment is important.10,11
How will the oral JAK inhibitors be incorporated into care compared to biologic agents such as dupilumab? Tolerance and more serious potential adverse events are concerns, with nausea, headaches, and acneform eruptions being associated with some of the medications, in addition to potential issues with herpes simplex and zoster infections. However, oral JAK inhibitors have the benefit of not requiring injections, something that many patients may prefer, and data show that these drugs generally are associated with a rapid reduction in pruritus and, depending on the drug, very quick and profound effects on objective signs of AD.10-12 Two head-to-head studies have been completed comparing dupilumab to oral JAK inhibitors in adults: the JADE COMPARE trial examining dupilumab vs abrocitinib12 and the Heads UP trial comparing dupilumab vs upadacitinib.14 Compared to dupilumab, higher-dose abrocitinib showed more rapid responses, superiority in itch response, and similarity or superiority in other outcomes depending on the time point of the evaluation. Adverse event profiles differed; for example, abrocitinib was associated with more nausea, acneform eruptions, and herpes zoster, while dupilumab had higher rates of conjunctivitis.12 Upadacitinib, which was only studied at higher dosing (30 mg daily), showed superiority to dupilumab in itch response and in improvement in AD severity in multiple outcome measures; however, there were increases in serious infections, eczema herpeticum, herpes zoster, and laboratory-related adverse events.14 Dupilumab has the advantage of studies of extended use along with real-world experience, generally with excellent safety and tolerance other than injection-site reactions and conjunctivitis.8 Biologics targeting IL-13—tralokinumab and lebrikizumab—also are to be added to our armamentarium.15,16 The addition of these agents and JAK inhibitors as new systemic treatment options points to the quickly evolving future of AD treatment for patients with extensive disease.
New topical therapies in development provide even more treatment options. New nonsteroidal topicals include topical JAK inhibitors such as ruxolitinib17; tapinarof,18 an aryl hydrocarbon receptor modulator; and phosphodiesterase 4 inhibitors. These agents may be useful either as monotherapy, as studied, potentially without the regional limitations associated with stronger topical corticosteroids, but also should be useful in clinical practice as part of therapeutic regimens with other topical steroid and nonsteroidal agents.
The Microbiome and AD
In addition, research looking at topical microbes as specific interventions that may mediate the microbiome and inflammation of AD are intriguing. A recent phase 1 trial from the University of California San Diego19 indicated that topical bacteriotherapy directed at decreasing Staphylococcus aureus may provide an impact in AD. Observations by Kong et al20 showed that gram-negative microbiome differences are seen in AD patients compared to unaffected individuals, which has fueled studies showing that Roseomonas mucosa, a gram-negative skin commensal, when applied as a topical live biotherapeutic agent has improved disease severity in children and adults with AD.21 Although further studies are underway, these initial data suggest a role for microbiome-modifying therapies as AD treatment.
Chronic Hand Eczema
Chronic hand eczema (CHE), which has considerable overlap with AD in many patients, especially children and adolescents,22-24 is another area of interesting research. This high-prevalence condition is associated with allergic and irritant contact dermatitis24-26—conditions that are both considered alternative diagnoses for and exacerbators of AD27—and is a disease process currently being targeted for new therapies. Delgocitinib (NCT04872101, NCT04871711), the novel JAK inhibitor ARQ-252 (NCT04378569), among other topical agents, as well as systemic therapeutics such as gusacitinib (NCT03728504), are in active trials for CHE. Given CHE’s impact on quality of life28 and its overlap with AD, investigation into this disorder can help drive future AD research as well as lead to better knowledge and treatment of CHE.
Despite the promising results of these myriad new therapies in AD, there are many factors that influence how and when we use these drugs, including their approval status, FDA labeling, and the ability of patients to access and afford treatment. Additionally, continued study is needed to evaluate the long-term safety and extended efficacy of newer drugs, such as the oral JAK inhibitors. Despite these hurdles, the current landscape of research and development is rapidly evolving. Compared to the many years when only one main group of therapies was a reasonable option for patients, the future of AD treatment looks bright.