Serum Dupilumab Levels Do Not Predict Clinical Response in AD
The finding that serum dupilumab levels in patients with atopic dermatitis (AD) do not predict long-term response levels or adverse events (AEs) suggests that factors beyond interpatient variability of the interleukin-4 receptor subunit-alpha (IL-4R-alpha) may drive response levels, according to a study published in JAMA Dermatology.
The study results mean that researchers should continue exploring potential AD drugs with novel mechanisms to help patients who fail type 2 inflammatory inhibition, experts told this news organization. The search for accurate augurs of clinical performance also must continue.
Addressing Inadequate Response
Quantifying nonresponse and incomplete response levels with dupilumab is difficult, said Jonathan I. Silverberg, MD, PhD, MPH, offering perspective on the study. “True nonresponse is probably less than 20%, but many other patients are inadequate responders even if they are having partial response.” Silverberg, associate professor of dermatology and director of clinical research, at George Washington University, Washington, was not an investigator.
Dr Jonathan Silverberg
Robert Sidbury, MD, MPH, added, “When a patient doesn’t respond to a medication that you expect they should, we always ask ourselves why.” Dermatologists have long assumed that, as with biologics for psoriasis, low blood levels were to blame for dupilumab nonresponse, said Sidbury, who is division chief of dermatology at Seattle Children’s Hospital and was not involved with the study. “This study showed that there was no correlation between response and blood levels.”
Dr Robert Sidbury
In the study, Lotte S. Spekhorst, MD, of National Expertise Center for Atopic Dermatitis, department of dermatology and allergology, University Medical Center Utrecht (the Netherlands) and coinvestigators prospectively followed 295 consecutive adult patients with moderate AD who were treated with dupilumab for 1 year. All patients received the same loading (600 mg) and biweekly (300 mg) doses.
The median dupilumab level at 16 weeks was 86.6 mcg/mL, which is higher than serum levels observed with other monoclonal antibodies used for other indications, such as psoriasis and inflammatory bowel disease, the authors noted. More importantly, researchers found no significant relationship between median week 16 dupilumab levels and 1-year clinical responses measured either discretely (Eczema Area and Severity Index [EASI] < 50, 50, 75, or 90; P = .18) or as quartiles (P = .06).
“It may be that response is dependent on target availability of the IL-4R-alpha, with an interpatient variability producing heterogeneity in response,” the authors wrote. But because serum dupilumab levels were relatively high, they said, all patients’ IL-4R-alpha “was likely fully saturated” at 16 weeks.
“This would explain why serum dupilumab levels were not related to effectiveness,” they noted, “although we cannot rule out differential effects in the tissue associated with heterogeneity in serum dupilumab levels.”
Dr Eric Simpson
The study helps explain why some patients do not fully respond to dupilumab, said Eric L. Simpson, MD, professor of dermatology, Oregon Health & Science University, Portland, who was not involved with the study.
“One hypothesis would be that drug serum levels differ due to metabolism or absorption reasons,” Simpson said in an interview. Results also suggest that heterogeneity in disease biology, such as other uninhibited cytokine pathways, might explain differences in clinical results. “Thus, more therapeutics that target different inflammatory pathways are needed to capture responses in patients not adequately responding to type 2 inflammatory blockade,” he said.
Assessing AEs
As with response levels, serum dupilumab levels at week 16 did not predict AEs including dupilumab-associated ocular surface disease (DAOSD), which impacted 46.4% of 216 patients who reported AEs. These findings also contradict what happens with biologics in other diseases such as psoriasis and inflammatory bowel disease, said Sidbury, wherein serum drug levels may predict both clinical response and side-effect risks.
A previous study showed that lowering dupilumab levels led to improvement in DAOSD. Authors of the current study therefore surmised that DAOSD development might be more associated with interpatient variability in IL-4R-alpha expression than with serum drug levels. “More research is necessary to confirm the hypothesis of interpatient variability of the IL-4Ra and the pharmacokinetics of dupilumab,” they concluded.
For now, said Sidbury, the study helps clinicians look beyond serum drug levels when patients respond inadequately to dupilumab. Moreover, added Silverberg, study results mean that physicians must find other ways to predict dupilumab response levels. “We need better predictors of clinical response – theranostic markers that we could test the patient to and understand how well they’re going to do,” he said.
Be it dupilumab or any other medication, he said, physicians lack even confirmatory biomarkers to reflect when a drug is working well. “Right now, we go with clinical assessments. But if it’s not drug levels, we have to figure out why some patients do markedly better than others.”
It was not unreasonable, Silverberg said, for the investigators to seek a biomarker in blood rather than tissue. “But in this disease, we believe that the more important place to look for biomarkers and drug levels would be in the skin itself. So we are still left with the issue” that drug levels in tissue might reflect response when serum levels do not.
The study was supported by grants from AbbVie, Eli Lilly, Leo Pharma, Pfizer, and Sanofi. Study patients participated in the BioDay Registry, which is sponsored by Sanofi, Regeneron, AbbVie, Eli Lilly, LEO Pharma, and Pfizer; the sponsors had no role in the study design and conduct. Spekhorst discloses receiving speaking fees from Abbvie outside the work; disclosures of other authors included receiving advisory, speaking consulting, and/or investigator fees from Sanofi Genzyme during the study. Several authors had no disclosures.
Simpson has been an investigator and consultant for Regeneron and Sanofi, makers of dupilumab. Silverberg has been an investigator, consultant, and speaker for Regeneron and Sanofi. Sidbury has been a clinical investigator for all dupilumab pediatric trials. (His institution has a contract with Regeneron and Sanofi, but he receives no money from the arrangement.)
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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