A39-03 Factors Associated With Mycophenolate Discontinuation in Stable Systemic Sclerosis-associated Interstitial Lung Disease

Rationale Interstitial lung disease (ILD) affects approximately 50% of patients with systemic sclerosis (SSc). While many SSc-ILD patients experience progressive lung function decline, others maintain stable disease. Mycophenolate mofetil (MMF), the preferred first-line therapy, is typically prescribed long-term, but optimal treatment duration for patients achieving disease stability remains unknown. Indefinite treatment risks side effects, while premature discontinuation may allow disease progression. This study examined patient and disease characteristics associated with clinicians decisions to continue or discontinue MMF in stable SSc-ILD patients. Methods This retrospective cohort study included SSc-ILD from the Johns Hopkins Scleroderma Center patients who received MMF for ≥12 months and had pulmonary function tests (PFTs), including percent predicted forced vital capacity (ppFVC) and diffusion capacity (ppDLCO), at MMF initiation and ≥1 year later. Patients were required to achieve PFT stability,defined as PFT improvement or < 5% ppFVC decline with <10% ppDLCO decline. Groups were defined by whether MMF was discontinued after achieving PFT stability. Demographics, SSc disease characteristics, and PFT results were compared using t-tests, Mann-Whitney U, or Fisher’s exact tests. A LASSO logistic regression model identified factors independentlyassociated with MMF discontinuation. Results Of 307 eligible SSc patients, 124 met PFT stability criteria ≥1 year after MMF initiation. After achieving stability, 78 patients continued MMF and 46 discontinued. No significant differences existed between groups in age, race, SSc disease duration, cutaneous subtype, skin disease severity, or autoantibody status. Baseline and follow-up ppFVC were similar between groups, as was ppFVC change. However, patients discontinuing MMF had higher baseline and follow-up ppDLCO, though ppDLCO change was comparable. LASSO regression identified two factors independently associated with MMF discontinuation: higher baseline ppDLCO (20% greater odds of discontinuation per 10% higher baseline ppDLCO) and male sex (2.7-fold higher odds versus females). Conclusion In this retrospective study of SSc patients receiving MMF for <1 year with stable/improved PFTs, only male sex and higher baseline ppDLCO were associated with MMF discontinuation. Further investigation is needed to determine whether other variables, such as ILD pattern or CT severity, influence discontinuation decisions, and to characterize PFT trajectories following MMF discontinuation. This abstract is funded by: none