1. Signed informed consent obtained prior to initiation of any study-specific procedures and study treatment 2. Laboratory confirmed SARS-CoV-2 infection as determined by qualitative polymerase chain reaction (PCR) by local laboratory from oro/nasopharyngeal exudate (or other respiratory specimen) collected no more than 24 hours prior to study treatment on Day 1 3. Admitted to hospital as clinically indicated for management of moderate SARS-CoV-2 (COVID-19) infection, defined by the following criteria: Positive PCR test for SARS-CoV-2 Symptoms of moderate illness with COVID-19, which could include any symptoms of mild illness or shortness of breath with exertion Clinical signs suggestive of moderate illness with COVID-19 such as respiratory rate ≥20 breaths but <30 breaths per minute, SpO2 >93% but <95% on room air at sea level, heart rate ≥90 but <125 beats per minute, and requiring O2 supplementation. If SpO2 on room air is not possible to be measured, the ratio PaO2/FiO2 should be >= 300 mm Hg (see Appendix 9), in addition, if the site is located at high altitude over sea level (> 1000 m), the ratio PaO2/FiO2 should be adjusted No clinical signs indicative of severe illness, which could include shortness of breath at rest or respiratory distress, or PaO2/FiO2 ratio < 300 mm Hg (sea level). 4. Onset of COVID-19 symptoms no later than 6 days prior to initiation of study treatment on Day 1 5. Male or female aged ≥18 years 6. Adequate bone marrow, liver, kidney, and metabolic function, defined by the following tests performed at local laboratory: Absolute neutrophil count ≥1000/mm3 (1.0 x 109/L) Lymphocyte count ≥500/mm3 (0.5 x 109/L) Platelet count ≥100 000/mm3 (100 x 109/L) Haemoglobin >9.0 g/dL Alanine transaminase (ALT), aspartate transaminase (AST) ≤3 x upper limit of normal (ULN) Serum bilirubin ≤1 x ULN Calculated creatinine clearance ≥30 mL/min (Cockcroft and Gault formula) Creatine phosphokinase ≤2.5 x ULN 7. Agree not to participate in another interventional clinical trial through Day 31 8. Females of reproductive capacity must have a negative serum pregnancy test by local laboratory at study enrolment and must be non-lactating 9. Females and males with partners of child-bearing potential must use effective contraception while on study treatment and for 6 months after last dose of plitidepsin.

1. Signed informed consent obtained prior to initiation of any study-specific procedures and study treatment 2. Laboratory confirmed SARS-CoV-2 infection as determined by qualitative polymerase chain reaction (PCR) by local laboratory from oro/nasopharyngeal exudate (or other respiratory specimen) collected no more than 24 hours prior to study treatment on Day 1 3. Admitted to hospital as clinically indicated for management of moderate SARS-CoV-2 (COVID-19) infection, defined by the following criteria: Positive PCR test for SARS-CoV-2 Symptoms of moderate illness with COVID-19, which could include any symptoms of mild illness or shortness of breath with exertion Clinical signs suggestive of moderate illness with COVID-19 such as respiratory rate ≥20 breaths but <30 breaths per minute, SpO2 >93% but <95% on room air at sea level, heart rate ≥90 but <125 beats per minute, and requiring O2 supplementation. If SpO2 on room air is not possible to be measured, the ratio PaO2/FiO2 should be >= 300 mm Hg (see Appendix 9), in addition, if the site is located at high altitude over sea level (> 1000 m), the ratio PaO2/FiO2 should be adjusted No clinical signs indicative of severe illness, which could include shortness of breath at rest or respiratory distress, or PaO2/FiO2 ratio < 300 mm Hg (sea level). 4. Onset of COVID-19 symptoms no later than 6 days prior to initiation of study treatment on Day 1 5. Male or female aged ≥18 years 6. Adequate bone marrow, liver, kidney, and metabolic function, defined by the following tests performed at local laboratory: Absolute neutrophil count ≥1000/mm3 (1.0 x 109/L) Lymphocyte count ≥500/mm3 (0.5 x 109/L) Platelet count ≥100 000/mm3 (100 x 109/L) Haemoglobin >9.0 g/dL Alanine transaminase (ALT), aspartate transaminase (AST) ≤3 x upper limit of normal (ULN) Serum bilirubin ≤1 x ULN Calculated creatinine clearance ≥30 mL/min (Cockcroft and Gault formula) Creatine phosphokinase ≤2.5 x ULN 7. Agree not to participate in another interventional clinical trial through Day 31 8. Females of reproductive capacity must have a negative serum pregnancy test by local laboratory at study enrolment and must be non-lactating 9. Females and males with partners of child-bearing potential must use effective contraception while on study treatment and for 6 months after last dose of plitidepsin.