Safety Study of SLV213 for the Treatment of COVID-19.

Inclusion Criteria: 1. Provision of signed and dated informed consent form. 2. Able to understand and willing to be available for all study visits and comply with all study procedures including Lifestyle Considerations throughout the study. 3. Male and Female individuals, age 18-65 inclusive at time of enrollment. 4. Good general health by medical history (MH), physical examination (PE), and vital signs (VS), clinical laboratory tests and Electrocardiogram (ECG) within normal reference range. Note 1: Lab exceptions include: lab test values that are within Grade 1 range per the Toxicity Table (Appendix A) are acceptable if not considered to be clinically significant by the investigator (PI, sub-investigator, or authorized clinician), with the exception of liver function tests (LFT) (transaminases Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), alkaline phosphatase (AP), total and direct bilirubin, serum creatinine, estimated glomerular filtration rate (eGFR) per the CKD-EPI formula, and urine protein, which must be within the laboratory normal reference range. Note 2: Screening laboratory values that fall outside the laboratory normal reference ranges and the ranges are not listed within the Toxicity Table (Appendix A) (e.g., decrease activated partial thromboplastin time (aPTT)) that are deemed Not Clinically Significant by the PI will be acceptable. 5. Ability to take oral medication and be willing to adhere to the dosing regimen. 6. Women of childbearing potential1 must have practiced or use true abstinence2 or use at least one acceptable primary form of contraception3 for specified periods4 before, during and after dosing. Note 1: Not of childbearing potential - post-menopausal females (defined as having a history of amenorrhea for at least one year) or a documented status as being surgically sterile (hysterectomy, bilateral oophorectomy, salpingectomy, tubal ligation, or Essure placement with a history of documented radiological confirmation test at least 90 days after the procedure). Note 2: True abstinence is 100% of the time without sexual intercourse (the male's penis enters the female's vagina). Periodic abstinence \[e.g., calendar, ovulation, symptothermal, post-ovulation methods\] and withdrawal are not acceptable methods of contraception). Note 3: Acceptable forms of primary contraception include a monogamous relationship with a vasectomized partner who has been vasectomized for 180 days or more before the participant receiving the study product, tubal ligation, non-hormonal, intrauterine device, (and if in a monogamous relationship with a male partner who uses a barrier method without spermicide) Note 4: Specified periods include at least 30 days prior to screening, during the period between screening and completion of dosing, and until at least 30 days following receipt of the last dose of study product. 7. Women of childbearing potential must have a negative serum Beta-human chorionic gonadotropin (HCG) pregnancy test at screening and a negative urine HCG pregnancy test at check-in (Day-1) within 24 hours before receiving the initial study product. 8. Male participants receiving the study product must use acceptable contraception and refrain from donating sperm from the day of first dose until 30 days after the last dose or be vasectomized.1 Note 1: Acceptable contraception includes abstinence from intercourse with a female of childbearing potential or use of a male condom without spermicide when engaging in any activity that allows for the passage of ejaculate to a female during the intervention period and for at least 30 days after ending study dosing, or surgical sterilization for 180 days or more. 9. Willing to avoid excessive physical exercise starting within 48 h prior to dosing and until discharge from the CTU on Day 9. 10. No history of acute febrile or infectious illness for at least 7 days prior to the administration of study drug. Exclusion Criteria: 1. Pregnant or lactating. 2. History of any chronic disease that may increase risk to subject or interfere with endpoint assessment1: Note 1: With the exception of stable chronic medical conditions that do not require prescribed oral or injectable medications (e.g., Type 2 diabetes managed by diet only). 3. History of bradycardia, orthostatic hypotension or orthostatic tachycardia, Long COVID or history of dysautonomia.1 Note 1: Exception is sinus bradycardia (HR \<60 bpm) in healthy participants (e.g., conditioned athletes) could be enrolled per investigator's clinical judgement. 4. Known history of a clinically significant food or drug allergy/hypersensitivity including known allergy/hypersensitivity to ingredients of the study drug or placebo. 5. Current seasonal allergies with ongoing symptoms for more than a week prior to dosing requiring glucocorticoids and/or frequent use of antihistamines for treatment. 6. History of any clinically significant disease or disorder, medical/surgical procedure, or trauma within 4 weeks prior to initiation of administration of study product(s). 7. History of any psychiatric condition that has required hospitalization in the last 12 months or subject is considered psychologically unstable by the investigator. 8. History of any substance use disorder or positive urine drug screening (UDS) test for illicit substances at Screening or Check-in (Day -1)1. Note 1: Any approved medical use of amphetamines, barbiturates, benzodiazepines, cannabis, tricyclic antidepressants and opiates will not be acceptable. 9. History of alcoholism or of binge1 or heavy alcohol drinking2 at any time in the 6 months before study product administration or positive urine alcohol test at Screening or Check-in (Day -1). Note 1: Binge drinking is defined as 5 or more drinks during a single occasion if male, or 4 or more if female. Note 2: Heavy drinking of alcohol is defined as consumption of more than 14 drinks of alcohol per week if male, or more than 7 drinks if female. 10. History of \>/=10 pack-years of nicotine product1 consumption in the 5-year period before screening, or positive urine cotinine screen at Check-in (Day -1)2. Note 1: Nicotine products include cigarettes, e-cigarettes, pipe, cigar, chewing tobacco, nicotine patch. Note 2: Positive urine cotinine at Screening is allowed if negative at Check-in (Day -1). 11. Body mass index (BMI) \</= 18 kg/m2 or \>/= 32 kg/m2, or weight \</= 100 lbs at Screening. 12. Prior exposure to SLV213 or K777 or K11777. 13. Use of any prohibited prescription or non-prescription medication within 14 days or 5 half-lives of the drug, whichever is longer, prior to study Check-in. 14. Use of any investigational drug product within 30 days or 5 half-lives (whichever is longer) before investigational product administration in this study. 15. Planned participation in a clinical research study that requires treatment with a study drug, blood draws or other invasive assessments during the study period (screening until final visit). 16. Blood or plasma donation of 500 mL within 3 months or more than 100 mL within 30 days before signing informed consent or planned donation prior to completion of this trial. 17. Positive viral serology tests for Human Immunodeficiency Virus (HIV), hepatitis B virus, or hepatitis C virus (HCV) at screening1 with one exception2: Note 1: Viral serology tests include HIV 1 and HIV 2 antibodies, Hepatitis B virus surface antigen (HBsAg), and HCV antibodies. Note 2: Do not exclude participants with HCV antibodies who have been successfully treated for Hepatitis C, do not take any treatment medications currently, do not use prohibited medications, have normal transaminases and are generally healthy. 18. Positive SARS-CoV-2 (COVID-19) molecular diagnostic test (Cue Care™ test) at Check-in (Day -1).