This is a randomized, double-blind, Phase 1b clinical trial to evaluate the safety, Pharmacodynamics, and Pharmacokinetic of SSD8432 combined with ritonavir tablets in adults with COVID-19.

This is a randomized, double-blinded, placebo-controlled, dose-climbing Phase Ib clinical trial, designed to evaluate the safety, pharmacodynamics, and pharmacokinetics of SSD8432/ ritonavir versus placebo in asymptomatic, mild, and common type adult COVID-19 subjects.

This clinical trial is planned to enroll 32 asymptomatic infected, mild or common type adult COVID-19 subjects, divided into 2 cohorts according to different doses of SSD8432:

Cohort 1: 16 subjects, 12 subjects will receive low-dose SSD8432/ ritonavir, and 4 subjects received placebo; Cohort 2: 16 subjects, 12 subjects will receive high-dose SSD8432/ ritonavir, and 4 subjects received placebo.

Inclusion Criteria:

1. Age ≥18 and ≤75, male or female.
2. Asymptomatic Infection, Mild, or Common Type of COVID-19.
3. Initial positive test of SARS-Cov-2 within 5 days of randomization.
4. Initial onset of COVID-19 signs/symptoms within 3 days of randomization.
5. The Ct value of SARS-COV-2 nucleic acid test before randomization is ≤ 25, or the Ct value is >25 and sarS-COV-2 serum IgG and IgM are negative.

Exclusion Criteria:

1. Transnasal high-flow oxygen therapy or non-invasive ventilation, invasive mechanical ventilation, or ECMO is required or anticipated to be urgently required.
2. Prior to current disease episode, any confirmed SARS-CoV-2 infection.
3. Known medical history of active liver disease (other than nonalcoholic hepatic steatosis).
4. Receiving dialysis or have known moderate to severe renal impairment.
5. Known human immunodeficiency virus (HIV) infection.
6. Suspected or confirmed concurrent active systemic infection other than COVID-19 that may interfere with the evaluation of response to the study intervention.s.
7. Oxygen saturation of ≤ 93% on room air obtained at rest within 24 hours prior to randomization..
8. Treatment with antivirals against SARS-CoV-2 within 14 days.
9. Current or expected use of any medications or substances that are highly dependent on CYP3A4 for clearance.
10. Concomitant use of any medications or substances that are strong inducers of CYP3A4 are prohibited within 28 days.
11. Has received or is expected to receive COVID-19 monoclonal antibody, convalescent COVID-19 plasma or other prohibited concomitant medication.
12. Females who are pregnant or breastfeeding.