Validation of Cutaneous Dermatomyositis Disease Area and Severity Index Activity Score and Other Efficacy Outcomes as Measures of Skin Disease in Dermatomyositis in the Lenabasum Phase 3 Trial

Abstract

In the past decade, there have been six industry-sponsored phase 3 trials in adult patients with dermatomyositis (DM), primarily focusing on improving muscle weakness. However, skin disease is a cardinal manifestation of DM. This study evaluated the sensitivity of Cutaneous Dermatomyositis Disease Area and Severity Index Activity score, Cutaneous Dermatomyositis Activity Investigator Global Assessment, Total Improvement Score, and other outcome measures used in DM clinical trials to detect improvement in DM skin disease activity. Data analyzed from the lenabasum phase 3 trial in DM showed that improvement in Cutaneous Dermatomyositis Disease Area and Severity Index Activity score increased proportionately with the degree of patient- or physician-reported improvement in skin disease, consistently measuring improvement when clinically meaningful improvement was reported at weeks 16-52. In contrast, Cutaneous Dermatomyositis Activity Investigator Global Assessment measured little change from baseline with reported no improvement in skin disease but also a similar change from baseline with slight improvement. No Skindex-29+3 subscale performed well at reflecting increasing degrees of improvement in skin disease. Extramuscular Global Assessment and Total Improvement Score generally showed increasing levels of improvement as the degree of patient- and physician-reported improvement in skin disease increased, but these are composite measures and are not specific to improvement in DM skin disease. To measure clinically meaningful improvement in skin disease in a DM trial, Cutaneous Dermatomyositis Disease Area and Severity Index Activity score is the more sensitive outcome measure across time points.