Evaluating a new treatment to prevent severe COVID-19 complications

Inclusion Criteria:

1. Signed informed consent by the participant or legal representative prior to the initiation of any study-specific procedure.
2. Males and females aged ≥ 18 years old at the time of the consent.
3. Confirmed diagnosis of SARS-CoV-2, influenza virus A, influenza virus B or RSV pneumonia by positive RT-PCR (results of a PCR prior to screening will be valid only if the PCR has been done for all 4 viruses and in 3 days prior to the screening visit). PCR will include the analysis of SARS-Cov-2, influenza A, influenza B and RSV.
4. Diagnosis of systemic inflammatory response syndrome (SIRS), defined by the satisfaction of any two of the criteria below:

   1. Body temperature over 38 ºC or under 36 ºC.
   2. Heart rate greater than 90 beats/minute.
   3. Respiratory rate higher than 20 breaths/min or PaCO2 lower than 32 mmHg.
   4. Leukocyte count higher than 12000/μL, lower than 4000/μL or over 10% immature forms or bands.
5. Need for oxygen therapy.
6. Female participants must be, either surgically sterilized or at least 1 year postmenopausal (confirmed by follicle-stimulating hormone \[FSH\] more than 20 international units \[Ius\] only for women under 54) or using adequate birth control (hormonal contraception, intrauterine contraceptive device, double barrier methods \[condom with spermicide, diaphragm with spermicide, or condom and diaphragm\]) or sexual abstinence for up to 90 days after the last treatment administration. Male participants must be willing to use barrier contraception (condom) for up to 90 days after the last treatment administration.

Exclusion Criteria:

1. Failure to perform screening or baseline examinations.
2. Body Mass Index (BMI) more than or equal to 35.
3. Irreversible critical condition, as assessed by the investigator.
4. Active autoimmune diseases or severe immunosuppression, unless stable and controlled for at least 3 months prior to the inclusion in the study.
5. Clinically significant, advanced or unstable disease that may interfere with primary or secondary variable evaluations, may bias the clinical assessment, such as:

   1. Liver function test abnormalities or other signs of hepatic insufficiency not justified by a pulmonary acute inflammation process: Aspartate transaminase (AST), alanine transaminase (ALT) more than 3 per upper limit of the reference range, total bilirubin more than or equal to 2 mg/dL; except for subjects with isolated elevation of indirect bilirubin relating to Gilbert syndrome.
   2. Renal insufficiency (serum creatinine more than 2 mg/dL (more than 150 μmol/L) and creatinine clearance less than 30 (according to Cockcroft-Gault formula).
   3. Myocardial infarction, unstable angina, heart failure within 3 months before screening.
   4. Bradycardia (heartbeat less than 50/min).
   5. Atrioventricular block (type II / Mobitz II and type III), congenital long QT syndrome, sinus node dysfunction or prolonged QTcF interval (males more than 450 msec and females more than 470 msec using Fridericia's formula: QTc = QT/ RR\^2 ).
   6. Uncontrolled diabetes mellitus (blood glucose level above 500 mg/dL) at the time of admission.
   7. Malignant tumors within the last 5 years, unless stable during that time. Skin malignancies (other than melanoma) and indolent prostate cancer are excluded from this criterion.
   8. Metastases.
   9. Human Immunodeficiency Virus (HIV), HBV \[hepatitis B surface antigen (HBs Ag) positive (+), or detected sensitivity on the HBV deoxyribonucleic acid (DNA), polymerase chain reaction (PCR) qualitative test for hepatitis B core antibody (HBc Ab) positive subjects\] or HCV \[HCV ribonucleic acid (RNA) detectable in any subject with positive anti-HCV antibody (HCV Ab)\].
6. Inability to comply with the study and monitoring procedures.
7. Pregnant and breastfeeding females (pregnancy test positive).
8. Suspected or known active drug or alcohol abuse.
9. Enrollment in another investigational drug study within 1 month before the screening
10. Subject who has any condition, including any psychological or psychiatric condition, in the opinion of the Investigator, would compromise the safety of the subject or the quality of the data and renders the subject an unsuitable candidate for the study.