The coronavirus (SARS-CoV-2) is a new strain of coronavirus found in human in 2019, which causes epidemic worldwide. A study found that the increase in hyaluronic acid levels is closely related to the clinical symptoms of COVID-19, including pulmonary ground glass lesions, lymphocytopenia, immune response and cytokine storms, systemic vascular diseases, thrombotic coagulation disorders, which suggests that hyaluronic acid could be an important target for COVID-19 treatment and could improve the clinical symptoms of COVID-19 patients.

The results from a recent clinical trial recruited 144 patients with COVID-19 show that the inhibitor of hyaluronic acid synthesis, hymecromone, can significantly improve clinical symptoms, such as lung lesions and lymphocytopenia in COVID-19 patients. Therefore, hymecromone has the potential to become one of the options of COVID-19 treatment.

This study is a single-center, randomized, parallel controlled, double-blind clinical trial designed to evaluate the efficacy and safety of Hymecromone tablets in subjects aged 18-90 years (with boundary values) with a confirmed mild or moderate form of COVID-19 infection. The aim of this study is to optimize the program of the combination of hymecromone in the treatment of COVID-19 to improve the therapeutic effect.

Inclusion Criteria:

1. Participants who have a positive SARS-CoV-2 test result ;
2. Participants who have been diagnosed with mild or ordinary type of COVID-19 infection;
3. Participants whose serum hyaluronic acid level was higher than the upper limit of normal value;
4. Participants who must agree to adhere to contraception restrictions;
5. Participants who understand and agree to comply with planned study procedures;
6. Participants who give signed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.

Exclusion Criteria:

1. Participants who have any of the following conditions when screening:

   1. ALT or AST > 5 ULN;
   2. Scr > 1.5 ULN or Ccr < 50 mL/min;
   3. TBIL > 2ULN ;
   4. HGB ≤ 90 g/ L;
   5. PLT ≤ 75×10^9/ L;

2. Participants who have suspected/active infections during the screening period including uncontrolled active bacterial, viral or fungal infections that require systemic treatment, except COVID-19 virus infections;

3. Participants who have any active autoimmune diseases during the screening period and need to be treated with immunosuppressants, including biological agents;

4. Participants who have a medical history of organ transplantation, or plan for organ transplantation including liver transplantation;

5. Participants who need a loading dose of anti-platelet drugs, such as aspirin (>300 mg/day) and clopidogrel (>300 mg/day);

6. Participants who have a medical history of central nervous system and digestive system bleeding, or a tendency of gastrointestinal bleeding, local active ulcer lesions included, in the last three months;

7. Participants who have biliary obstruction;

8. Female participants who are pregnant or breast-feeding or plan to be pregnant within this study period;

9. Male participants whose wife or partner plan to be pregnant within this study period.

10. Participants who have taken the drugs containing coumarin compounds, such as warfarin, within 3 days before screening;

11. Participants who have other diseases requiring hospitalization and/or in a need of surgical treatment within 7 days before screening, or have suffered from life-threatening diseases within 30 days before screening;

12. Participants who have known allergies to any of the components used in the formulation of the interventions;

13. Participants who have taken a part in a clinical study of an investigational intervention in the last 28 days. After 5 half-lives or 28 days, whichever is longer, can be allowed for screening;

14. Participants who are not suitable for this trial, and with any medical condition will compromise their own safety.