OPTION: A Trial to Assess the Safety & Efficacy of MS1819 in Patients With Exocrine Pancreatic Insufficiency Due to Cystic Fibrosis

This is a Phase 2, open-label, multi-center, 2x2 crossover study assessing the safety and
efficacy of MS1819-SD vs porcine PERT given at the same dose that was being administered
during the pre-study period.

MS1819-SD will be assessed in a 2x2 crossover including at least 30 patients completing both
periods.

Inclusion Criteria:

1. Cystic fibrosis, based on 2 clinical features consistent with CF, plus initial
diagnostic sweat chloride ≥ 60 mmol/L

2. Under stable dose of porcine PERT

3. A fair or better nutritional status

4. Fecal elastase <100 µg/g

5. Standard-of-care medications including CFTR modulators are allowed

Exclusion Criteria:

1. History or diagnosis of fibrosing colonopathy

2. Any chronic diarrheal illness unrelated to pancreatic insufficiency

3. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) level ≥5 ×upper
limit of normal (ULN), or total bilirubin level ≥1.5 ×ULN at the Screening visit

4. Feeding via an enteral tube during 6 months before screening

5. Forced expiratory volume ≤30% at the Screening visit