A Phase 1/2 Study to Assess the Safety, Tolerability and Pharmacokinetics of NGM621 in Healthy Subjects, and to Assess the Safety, PK and Efficacy in Subjects With Moderate to Severe ARDS Caused by COVID-19

Inclusion Criteria: * Female subjects of childbearing potential must have a negative serum pregnancy test result at Screening and a negative urine pregnancy test result prior to dosing. * Female subjects of childbearing potential and male subjects with a female partner of childbearing potential must use an effective method of contraception during the study, for at least 1 month following study completion, and must not plan to become pregnant for at least 1 month after her last study medication dose. * BMI 18-32 kg/m2 inclusive * Ability to understand and provide informed consent * Subjects confirmed with SARS-CoV-2 infection by PCR and hospitalized * If on mechanical support, less or equal than 2 days on mechanical ventilation or oxygenation Exclusion Criteria: * Currently enrolled in another investigational protocol to treat SARS-CoV-2 infection * Known history of complement deficiency * Active infection with, or history of, compllicated pneumococcal or Neisseria meningitis infection or history of unexplained, recurrent infection, within the last 60 days prior to dosing.