A phase 2, open label single arm study for evaluating safety & efficacy of apremilast in the treatment of cutaneous disease in patients with recalcitrant dermatomyositis.

Purpose: Studying the efficacy and safety of apremilast as an add-on therapy in patients with recalcitrant cutaneous dermatomyositis. Studying the mechanism of action of apremilast in dermatomyositis by performing RNA sequencing and immunohistochemistry on skin biopsies before and after treatment. Methods: We enrolled 8 patients with recalcitrant dermatomyositis. Apremilast 30 mg orally twice daily was added to a stable treatment regimen of steroids and/or steroids sparing agents and patients were followed for 7 months. A CDASI, muscle score, dermatology life quality index (DLQI), and depression assessments were performed at baseline and regularly till month 7. Skin biopsies were performed at baseline and 3-months post-apremilast to study gene expression alterations. Results: Our ORR assessed at 3 months post apremilast was 87.5%. The response was maintained at 6 months with continued decrease in CDASI and improvement in DLQI. The mean decrease in CDASI was 12.9 points (p<0.05). Apremilast was well tolerated and without any grade 3 or higher adverse events using CTCAE version 5. RNA sequencing was performed on skin biopsies from 7 patients before and 3 months after apremilast. Out of 39,076 expressed genes, there were 195 whose expression changed =2-fold at P<0.01 (123 down- and 72 up-regulated), several genes are known JAK-STAT targets. Using GSEA analysis, we identified 13 pathways significantly downregulated by apremilast, notably STAT1, STAT3, IL-2, IL-6, IL-12, IL-23, INF?, and TNFa pathways. Immunohistochemical staining confirmed JAK/STAT signaling inhibition at the protein level. Conclusions: Apremilast is a safe and efficacious add-on treatment in recalcitrant dermatomyositis with an overall response rate of 87.5%, and functions through downregulation of JAK/STAT signaling in dermatomyositis. Overall design: Phase 2 open label single arm clinical trial, RNA gene sequencing and immunohistochemical analysis of skin biopsies before and after treatment.