Development and Evaluation of the Dermatomyositis Outcomes for Muscle and Skin as an Outcome Measure in Dermatomyositis Clinical Trials

The Total Improvement Score (TIS), which is used as the primary efficacy measure in dermatomyositis (DM) clinical trials, lacks a skin-specific measure. However, skin is a defining feature of DM. In this study, data were analyzed from the phase 3 trial of lenabasum in DM. Cutaneous Dermatomyositis Disease Area and Severity Index-Activity scores and all components of the TIS were collected at baseline and weeks 16, 28, 40, and 52. From these assessments, a composite outcome was developed, named Dermatomyositis Outcomes for Muscle and Skin, which includes certain components of the TIS and the Cutaneous Dermatomyositis Disease Area and Severity Index-Activity scores. The relative sensitivities of the TIS and Dermatomyositis Outcomes for Muscle and Skin to detect improvement in DM skin and muscle disease activity were analyzed. A total of 174 patients with DM were included, 82% were female, and 75% were White. Mean (SD) age was 51.9 (12.20) years. Treatment effect using the TIS ranged between 17.6 and 21.7 points for muscle and skin responders versus nonresponders across time points. The Dermatomyositis Outcomes for Muscle and Skin score displayed a statistically significantly greater treatment effect of 25.9-40.0 points for responders than for nonresponders, depending on the response assessed and the time point. Dermatomyositis Outcomes for Muscle and Skin is a more sensitive composite measure that reflects improvement from baseline in both skin and muscle disease activity, suggesting usefulness for use in future DM clinical trials.