Mycophenolate Mofetil in Systemic Sclerosis With Subclinical Interstitial Lung Disease

Overview

The goal of this pilot study is to assess the feasibility of a larger study on the efficacy of mycophenolate mofetil in people diagnosed with systemic sclerosis with mild lung involvement. Participants will be recruited over 12 months at 3 academic centers and assigned randomly to receive either mycophenolate mofetil or placebo, a look-alike substance that contains no active drug, for 96 weeks.

Background: Systemic sclerosis (SSc, scleroderma) is a rare but life-threatening systemic autoimmune disease characterized by microvasculopathy, serum autoantibodies, inflammation and fibrosis of the skin and internal organs. Early rapidly progressive SSc remains the most lethal autoimmune rheumatic disease, with over 60% mortality at 5 years in high-risk patients. Interstitial lung disease (ILD) is the leading cause of SSc-related mortality and affects over half of SSc patients. SSc-ILD is currently treated with immunosuppressive and anti-fibrotic drugs, with the first-line treatment being mycophenolate mofetil (MMF), although treatments have modest benefits when initiated in advanced stages of disease. Emerging data suggest that earlier treatment, when lung function is still normal despite evidence of ILD on computed tomography scan ("subclinical SSc-ILD"), may lead to improved outcomes, suggesting a window of treatment opportunity. Research Aims: The goal of the proposed pilot RCT is to establish the feasibility of a phase III RCT that will assess the efficacy of MMF in subclinical SSc-ILD. Specifically, we aim to: 1. Determine the rate of patient recruitment at three centers over one year, and identify barriers and solutions to recruitment; 2. Determine the proportion of participants receiving the allocated treatment and with complete primary efficacy outcome data at 48 and 96 weeks; and 3. Generate preliminary data on clinical efficacy outcomes that will contribute information to the analysis of the phase III trial through a Bayesian inference framework. Methods: Participants will be adults with SSc, ILD diagnosed within the past 3 years and a normal forced vital capacity (≥ 80%). Participants will be recruited over 12 months at 3 academic centers affiliated to the Canadian Scleroderma Research Group. Eligible participants will be assigned using stratified randomization to receive either MMF (up to 2 grams daily) or placebo for 96 weeks. The primary feasibility outcome will be the rate of recruitment per site over 12 months. A Bayesian approach will be used to estimate the probability of reaching the target sample size based on observed recruitment rates, with decision rules to continue, adapt, or stop the trial. Data collected on the primary clinical efficacy outcome (annual rate of decline in forced vital capacity over 96 weeks) will be used to inform the analysis of the phase III trial (as an informative prior) through a Bayesian inference framework.