Mycophenolate Mofetil in Systemic Sclerosis With Subclinical Interstitial Lung Disease

Inclusion Criteria:

1. Able and willing to provide informed consent and adhere to study protocol;
2. Women and men of all race/ethnicity, aged 18 years and older;
3. SSc based on 2013 ACR-EULAR classification criteria;
4. Presence of interstitial lung disease on HRCT scan, obtained within 12 months before screening, that shows fibrosis affecting less than 20% of the lungs, as confirmed by an expert radiologist;
5. Diagnosis of ILD within 7 years before screening;
6. Forced vital capacity of 80% predicted and above, on pulmonary function tests obtained within 6 months before screening;
7. Able to communicate in French or English;

Exclusion Criteria:

1. Progressive pulmonary fibrosis, defined as at least two of three criteria (worsening symptoms, radiological progression, and physiological progression) occurring within the past year with no alternative explanation, as defined by the 2022 ATS/ERS/JRS/ALAT Clinical Practice Guideline;
2. Use of medications with putative lung disease-modifying properties:

   1. Current use of MMF, mycophenolic acid, azathioprine, calcineurin inhibitors (e.g. tacrolimus, cyclosporin A), tocilizumab, nintedanib, pirfenidone or corticosteroids (Prednisone equivalent dose \>10 mg/day) at time of screening
   2. Cyclophosphamide within one year prior to screening
   3. Rituximab within 6 months prior to screening
   4. Cell therapies (including stem cell transplantation) within one year prior to screening
3. Current use of other biological, targeted synthetic or investigational products with immunosuppressive effects (e.g. TNF inhibitors, abatacept, tofacitinib) at time of screening
4. Any contraindication to MMF, including:

   1. Pregnancy and/or breastfeeding
   2. Female of childbearing potential not using reliable method of contraception
   3. Persistent leucopenia (white blood cell count \<3.0 x103/μL)
   4. Persistent thrombocytopenia (platelet count \<100 x103/μL)
   5. Persistent anemia (hemoglobin \<100 g/L)
   6. Baseline liver enzymes (alanine transaminase (ALT) or aspartate transaminase (AST)) or bilirubin \>1.5 times the upper limit of normal, other than due to Gilbert's disease
   7. Uncontrolled congestive heart failure
   8. Active infection (lung or elsewhere)
   9. Active solid or hematological malignancy (other than basal cell cancer of the skin or cervical carcinoma in situ removed entirely by biopsy)
   10. Active peptic ulcer disease
   11. Other serious concomitant medical illness, unreliability or drug abuse that might compromise the patient's ability to safely take MMF
   12. Use of drugs or products with significant interactions with MMF