Study of Mavrilimumab (KPL-301) in Participants Hospitalized With Severe Corona Virus Disease 2019 (COVID-19) Pneumonia and Hyper-inflammation

The Phase 2 portion of the study will evaluate the efficacy and safety of 2 dose levels of mavrilimumab relative to placebo (standard of care) in participants who have tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with x-ray/computed tomography (CT) evidence of bilateral pneumonia and active or recent signs of hyperinflammation (fever or clinical laboratory results indicative of hyper-inflammation). The Phase 3 portion is intended to confirm Phase 2 efficacy and safety findings. In both Phase 2 and Phase 3, participants will be enrolled into 2 cohorts: Cohort 1 will include non-mechanically ventilated, hospitalized participants who require supplemental oxygen to maintain oxygen saturation (SpO2) ≥ 92% (ie, "non-mechanically ventilated" participants); Cohort 2 will include hospitalized participants for whom mechanical ventilation was recently initiated (ie, "mechanically ventilated" participants). Following Screening, enrolled participants in each cohort will be randomized 1:1:1 to receive one of 2 mavrilimumab dose levels, or placebo as a single intravenous (IV) infusion (Day 1). Participants will undergo primary study assessments through Day 29 and will be followed for safety through Day 90.