A Study to Evaluate the Efficacy and Safety of Prothione™ Capsules for Mild to Moderate Coronavirus Disease 2019 (COVID-19)

Inclusion Criteria: Potential subjects are required to meet all of the following criteria for enrollment into the study: 1. Male or female adult ≥ 18 years of age at time of enrollment with mild to moderate symptoms caused by coronavirus 2019 confirmed infection with COVID-19 by PCR and one or more of the following: Mild (uncomplicated) Illness: * Diagnosed with COVID-19 by a standardized RT-PCR assay AND * Mild symptoms, such as fever, rhinorrhea, mild cough, sore throat, malaise, headache, muscle pain, or malaise, but with no shortness of breath AND * No signs of a more serious lower airway disease AND RR\<20, HR \<90, oxygen saturation (pulse oximetry) \> 93% on room air Moderate Illness: * Diagnosed with COVID-19 by a standardized RT-PCR assay AND * In addition to symptoms above, more significant lower respiratory symptoms, including shortness of breath (at rest or with exertion) OR * Signs of moderate pneumonia, including RR ≥ 20 but \<30, HR ≥ 90 but less than 125, oxygen saturation (pulse oximetry) \> 93% on room air AND * If available, lung infiltrates based on X-ray or CT scan \< 50% present 2. Subjects with normal level of Vitamin B2; Note: If the result was below the normal range, based on clinical judgment by physician, appropriate treatment to be added to the subject treatment regimen as per standard of care. A B complex daily supplement will be supplied, if needed. 3. Subject (or legally authorized representative) provides written informed consent prior to initiation of any study procedures; 4. Understands and agrees to comply with planned study procedures; and 5. Negative pregnancy test for female subjects. Women of child-bearing potential (WOCBP) and Women not of child-bearing potential are eligible to participate. Both women of child-bearing potential and women of no child-bearing potential should use an approved method of birth control and agrees to continue to use this method for the duration of the study (and for 30 days after taking the last dose of Prothione™ ). Acceptable methods of contraception include abstinence, female subject/partner's use of hormonal contraceptive (oral, implanted, or injected) in conjunction with a barrier method (WOCBP only), female subject/partner's use of an intrauterine device (IUD), or if the female subject/partner is surgically sterile or 2 years post-menopausal. All male subjects/partners must agree to consistently and correctly use a condom for the duration of the study. In addition, subjects may not donate sperm for the duration of the study and for 30 days after taking study drug. Exclusion Criteria: Potential subjects meeting any of the following criteria will be excluded from enrollment: 1. Subjects showing signs of acute respiratory distress syndrome (ARDS) or respiratory failure necessitating mechanical ventilation at the time of screening; 2. Subjects who have history of receiving NAC, Prothione™ Capsules or GSH supplements in the past 30 days before the screening visit; 3. Subjects who have history of receiving corticosteroids (topical corticosteroid is excluded) in the past 30 days; 4. Subjects who are currently receiving Chemotherapy or Immunotherapy for the treatment of cancer; 5. Any uncontrolled active systemic infection requiring admission to an intensive care unit (ICU); 6. Subject with active Hepatitis B and Hepatitis C; 7. Subjects who are participating in other clinical trials; 8. Subjects that have had any Covid19 Vaccination; 9. Subjects who have a history of allergic reactions attributed to compounds of similar chemical or biologic composition to Prothione™ are not eligible; 10. Inability to provide informed consent or to comply with study requirements; and 11. Subjects who are pregnant or breast-feeding.