ACTIV-5 / Big Effect Trial (BET-B) for the Treatment of COVID-19

Inclusion Criteria:

1. Admitted to a hospital with symptoms suggestive of Coronavirus Disease 2019 (COVID-19)
and requires ongoing medical care.

2. Subject (or legally authorized representative) provides informed consent prior to
initiation of any study procedures.

3. Subject (or legally authorized representative) understands and agrees to comply with
planned study procedures.

4. Male or non-pregnant female adult >/= 18 years of age at time of enrollment.

5. Illness of any duration and has laboratory-confirmed severe acute respiratory syndrome
coronavirus 2 (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 randomization.

6. Illness of any duration, and requiring, just prior to randomization, supplemental
oxygen (any flow), mechanical ventilation or Extracorporeal Membrane Oxygenation
(ECMO) (ordinal score 5, 6, or 7).

7. Women of childbearing potential must agree to either abstinence or use at least one
acceptable method of contraception* from the time of screening through 5 months post
study intraperitoneal (IP) dosing.

* Acceptable methods include barrier contraceptives (condoms or diaphragm) with
spermicide, intrauterine devices (IUDs), hormonal contraceptives, oral contraceptive
pills, and surgical sterilization.

8. 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:

1. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 5 times the upper
limit of normal.

2. Subjects with a low glomerular filtration rate (eGFR), specifically:

1. Subjects with a glomerular filtration rate (eGFR) 20-30 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.

2. All subjects with a glomerular filtration rate (eGFR) <20 mL/min (including
hemodialysis and hemofiltration) are excluded.

3. Pregnancy or breast feeding.

4. Anticipated discharge from the hospital or transfer to another hospital which is not a
study site within 72 hours of enrollment.

5. Allergy to any study medication.

6. Received five or more doses of remdesivir prior to screening.

7. Received small molecule tyrosine kinase inhibitors, including Janus kinase (JAK)
inhibitors (e.g., baricitinib, ibrutinib, acalabrutinib, imatinib, gefitinib), in the
4 weeks prior to screening.

8. Received monoclonal antibodies targeting cytokines (e.g., tumor necrosis factor (TNF)
inhibitors, anti-IL-1 [e.g., anakinra, canakinumab], anti-IL-6 [e.g., tocilizumab,
sarilumab, sitlukimab]), or T-cells (e.g., abatacept) in the 4 weeks prior to
screening.

9. Received monoclonal antibodies targeting B-cells (e.g., rituximab, and including any
targeting multiple cell lines including B-cells) in the 3 months prior to screening.

10. Received granulocyte-macrophage colony-stimulating factor (GM-CSF) agents (e.g.,
sargramostim) within 2 months prior to screening.

11. Received other immunosuppressants in the 4 weeks prior to screening and in the
judgement of the investigator, the risk of immunosuppression with lenzilumab is larger
than the risk of Coronavirus Disease 2019 (COVID-19).

12. Received any live vaccine in the 4 weeks prior to screening.

13. Known active tuberculosis.

14. Known history of Human Immunodeficiency Virus (HIV), Hepatitis B (HBV) or untreated
hepatitis C (HCV) infection.

15. History of pulmonary alveolar proteinosis (PAP).

16. Has a malignancy currently receiving immunosuppressive chemotherapy, immunodeficiency,
uncontrolled opportunistic infection, or uncontrolled cirrhosis.

17. Has a medical condition that could, in the judgment of the investigator, limit the
interpretation and generalizability of trial results.

18. Positive test for influenza virus during the current illness (influenza testing is not
required by protocol).

19. Previous participation in an ACTIV-5/Big Effect Trial (BET).