Inclusion Criteria:  Admitted to a hospital with symptoms suggestive of COVID-19 and requires ongoing medical care. Subject (or legally authorized representative) provides informed consent prior to initiation of any study procedures. Subject (or legally authorized representative) understands and agrees to comply with planned study procedures. Male or non-pregnant female adult >/=18 years of age at time of enrollment. Illness of any duration and has laboratory-confirmed SARS-CoV-2 infection as determined by polymerase chain reaction (PCR) or other commercial or public health assay (e.g., Nucleic Acid Amplification Test [NAAT], antigen test) in any respiratory specimen or saliva </=14 days prior to randomization.  Illness of any duration, and requiring, just prior to randomization, supplemental oxygen (any flow), mechanical ventilation or extracorporeal membrane oxygenation (ECMO) (ordinal scale category 5, 6, or 7).*  *If written documentation of the positive test result is not available at the time of enrollment (e.g., report came from other institution), the test should be repeated and the subject may be enrolled if positive.  Women of childbearing potential and men must agree to either abstinence or use at least one acceptable method of contraception** from the time of screening through 30 days after the last dose of danicopan for women and 90 days after the last dose for men.  **Acceptable methods include barrier contraceptives (condoms or diaphragm) with spermicide, intrauterine devices (IUDs), hormonal contraceptives, oral contraceptive pills, and surgical sterilization.  Agrees not to participate in another blinded clinical trial (both pharmacologic and other types of interventions) for the treatment of COVID-19 through Day 29  Exclusion Criteria:  aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 5 times the upper limit of normal.  Subjects with a low glomerular filtration rate (eGFR), specifically:  Subjects with an eGFR 15-30 mL/min are excluded unless in the opinion of the principal investigator (PI), the potential benefit of participation outweighs the potential risk of study participation. All subjects with an eGFR <15 mL/min (including hemodialysis and hemofiltration) are excluded. Pregnancy or breast feeding Anticipated discharge from the hospital or transfer to another hospital which is not a study site within 72 hours of enrollment. Allergy to any study medication. Received five or more doses of remdesivir prior to screening. Treatment with a complement inhibitor in the prior 8 weeks.* Has active uncontrolled opportunistic infection, or uncontrolled cirrhosis.* History of infection with N. meningitidis.* Known history of hypersensitivity to danicopan or its excipients.* Has a medical condition that could, in the judgment of the investigator, limit the interpretation and generalizability of trial results. Positive test for influenza virus during the current illness (influenza testing is not required by protocol). History of liver cirrhosis.* Previous participation in an ACTIV-5/BET trial. Refuses to refrain from breastfeeding from the time of screening through 30 days after the last dose of danicopan.* Refuses to receive prophylactic antibiotics against meningococcal infections if the subject has not been vaccinated in the 3 years prior to Study Day 1.