Enrichment strategies for clinical trials targeting skin fibrosis and interstitial lung disease in systemic sclerosis.

Abstract

This review gives an update on enrichment strategies for clinical trials in patients with systemic sclerosis (SSc) in two contexts - skin fibrosis in early diffuse cutaneous disease, and SSc-related interstitial lung disease (ILD) - focusing on reports from the last 18 months. Lessons have been learnt from recent studies, making this review timely. Recent trials have highlighted how patients included into trials must be carefully selected to include 'progressors', that is, those most likely to benefit from treatment, and how drug mechanism action of action will influence trial design. For skin fibrosis, current enrichment strategies are mainly on clinical grounds (including disease duration, extent of skin thickening, tendon friction rubs and anti-RNA polymerase III positivity). Gene expression signatures may play a role in the future. For ILD, current enrichment strategies (degree of lung involvement as assessed by pulmonary function and high-resolution computed tomography) may help to recruit the most informative patients, but should avoid being too stringent to be feasible or for findings to be generalizable. Both skin fibrosis and ILD trials are challenging in SSc. Ongoing work on enrichment strategies should help to differentiate effective new treatments from placebo with smaller sample sizes than have been included in recent studies.