* prior history of, or considered to be at risk for, agranulocytosis, nephropathy, liver disease, or interstitial pneumonia * serious hepatic disorder (child-pugh scores b or c) or alanine transaminase (alt) or aspartate transaminase (ast) \> 5 times the upper limit of normal (uln) at screening * chronic kidney disease (ckd) national kidney foundation (nkf) stages 3b - 5 chronic renal dysfunction (estimated glomerular filtration rate \[egfr\] \<45 ml/min/1.73m2 according to cockcroft gault formula) * proteinuria ≥ 1+ or ≥ 30 mg on dipstick urinalysis that is confirmed on repeat assessment within 24 hours * serum bun ≥ 2 × uln or cr ≥ 2 × uln * leukopenia with absolute granulocyte count \< 1500/µl * history of positive human immunodeficiency virus (hiv) test or organ transplant * receipt of cancer chemotherapy or immunomodulatory drugs including (but not limited to) biologics such as anti-cd20, anti-tnf, anti-il6; alkylating agents (e.g., cyclophosphamide); antimetabolites (e.g., azathioprine); or chronic corticosteroid use equivalent to prednisone \>10 gm/day, during preceding 2 months * confirmed positive for influenza at screening * confirmed positive for respiratory syncytial virus (rsv) at screening * pregnant or breastfeeding * current use of, or known allergy to bucillamine or penicillamine (e.g., for wilson's disease, rheumatoid arthritis) * current participation in any other clinical trial of an experimental treatment * receipt of any experimental treatment for covid-19 (herbal/homeopathic, off-label, compassionate use, or trial related) within the 30 days prior to screening

* prior history of, or considered to be at risk for, agranulocytosis, nephropathy, liver disease, or interstitial pneumonia * serious hepatic disorder (child-pugh scores b or c) or alanine transaminase (alt) or aspartate transaminase (ast) \> 5 times the upper limit of normal (uln) at screening * chronic kidney disease (ckd) national kidney foundation (nkf) stages 3b - 5 chronic renal dysfunction (estimated glomerular filtration rate \[egfr\] \<45 ml/min/1.73m2 according to cockcroft gault formula) * proteinuria ≥ 1+ or ≥ 30 mg on dipstick urinalysis that is confirmed on repeat assessment within 24 hours * serum bun ≥ 2 × uln or cr ≥ 2 × uln * leukopenia with absolute granulocyte count \< 1500/µl * history of positive human immunodeficiency virus (hiv) test or organ transplant * receipt of cancer chemotherapy or immunomodulatory drugs including (but not limited to) biologics such as anti-cd20, anti-tnf, anti-il6; alkylating agents (e.g., cyclophosphamide); antimetabolites (e.g., azathioprine); or chronic corticosteroid use equivalent to prednisone \>10 gm/day, during preceding 2 months * confirmed positive for influenza at screening * confirmed positive for respiratory syncytial virus (rsv) at screening * pregnant or breastfeeding * current use of, or known allergy to bucillamine or penicillamine (e.g., for wilson's disease, rheumatoid arthritis) * current participation in any other clinical trial of an experimental treatment * receipt of any experimental treatment for covid-19 (herbal/homeopathic, off-label, compassionate use, or trial related) within the 30 days prior to screening

- prior history of, or considered to be at risk for, agranulocytosis, nephropathy, liver disease, or interstitial pneumonia - serious hepatic disorder (child-pugh scores b or c) or alanine transaminase (alt) or aspartate transaminase (ast) > 5 times the upper limit of normal (uln) at screening - chronic kidney disease (ckd) national kidney foundation (nkf) stages 3b - 5 chronic renal dysfunction (estimated glomerular filtration rate [egfr] <45 ml/min/1.73m2 according to cockcroft gault formula) - proteinuria ≥ 1+ or ≥ 30 mg on dipstick urinalysis that is confirmed on repeat assessment within 24 hours - serum bun ≥ 2 × uln or cr ≥ 2 × uln - leukopenia with absolute granulocyte count < 1500/µl - history of positive human immunodeficiency virus (hiv) test or organ transplant - receipt of cancer chemotherapy or immunomodulatory drugs including (but not limited to) biologics such as anti-cd20, anti-tnf, anti-il6; alkylating agents (e.g., cyclophosphamide); antimetabolites (e.g., azathioprine); or chronic corticosteroid use equivalent to prednisone >10 gm/day, during preceding 2 months - confirmed positive for influenza at screening - confirmed positive for respiratory syncytial virus (rsv) at screening - pregnant or breastfeeding - current use of, or known allergy to bucillamine or penicillamine (e.g., for wilson's disease, rheumatoid arthritis) - current participation in any other clinical trial of an experimental treatment - receipt of any experimental treatment for covid-19 (herbal/homeopathic, off-label, compassionate use, or trial related) within the 30 days prior to screening

- prior history of, or considered to be at risk for, agranulocytosis, nephropathy, liver disease, or interstitial pneumonia - serious hepatic disorder (child-pugh scores b or c) or alanine transaminase (alt) or aspartate transaminase (ast) > 5 times the upper limit of normal (uln) at screening - chronic kidney disease (ckd) national kidney foundation (nkf) stages 3b - 5 chronic renal dysfunction (estimated glomerular filtration rate [egfr] <45 ml/min/1.73m2 according to cockcroft gault formula) - proteinuria ≥ 1+ or ≥ 30 mg on dipstick urinalysis that is confirmed on repeat assessment within 24 hours - serum bun ≥ 2 × uln or cr ≥ 2 × uln - leukopenia with absolute granulocyte count < 1500/µl - history of positive human immunodeficiency virus (hiv) test or organ transplant - receipt of cancer chemotherapy or immunomodulatory drugs including (but not limited to) biologics such as anti-cd20, anti-tnf, anti-il6; alkylating agents (e.g., cyclophosphamide); antimetabolites (e.g., azathioprine); or chronic corticosteroid use equivalent to prednisone >10 gm/day, during preceding 2 months - confirmed positive for influenza at screening - confirmed positive for respiratory syncytial virus (rsv) at screening - pregnant or breastfeeding - current use of, or known allergy to bucillamine or penicillamine (e.g., for wilson's disease, rheumatoid arthritis) - current participation in any other clinical trial of an experimental treatment - receipt of any experimental treatment for covid-19 (herbal/homeopathic, off-label, compassionate use, or trial related) within the 30 days prior to screening