Part 1: Endpoints (through Day 7) Safety • Change from baseline in vital signs and clinical laboratory results • Incidence and severity of treatment-emergent AEs (TEAEs) Pharmacokinetics • Plasma PK parameters on Day 1 and Day 7 Pharmacodynamics (PD) • Change from baseline in SaO2/FiO2 ratio Additional Endpoints (through Day 28) Safety • Change from baseline in vital signs, and clinical laboratory results • Incidence and severity of TEAEs Part 2 The co-primary efficacy endpoints are: • Change from baseline in SaO2/FiO2 ratio in mmHg on Day 7 • Number of VFDs from randomization to Day 28

Part 1: Endpoints (through Day 7) Safety • Change from baseline in vital signs and clinical laboratory results • Incidence and severity of treatment-emergent AEs (TEAEs) Pharmacokinetics • Plasma PK parameters on Day 1 and Day 7 Pharmacodynamics (PD) • Change from baseline in SaO2/FiO2 ratio Additional Endpoints (through Day 28) Safety • Change from baseline in vital signs, and clinical laboratory results • Incidence and severity of TEAEs Part 2 The co-primary efficacy endpoints are: • Change from baseline in SaO2/FiO2 ratio in mmHg on Day 7 • Number of VFDs from randomization to Day 28