cartoon of woman holding a tissue like she is about to sneeze, virus cartoons floating around behind her
Credit: NIH

A clinical research study looking at whether S-217622, an oral protease inhibitor, shortens the duration of COVID-19 symptoms and may reduce the risk of developing persistent COVID-related symptoms (long COVID).  

The study is enrolling a wide variety of participants, as COVID-19 may affect people differently based on their age, sex, gender, and race/ethnicity.

What Does the Study Involve?

Participants who meet all the study criteria will be randomly assigned to the treatment or placebo group. The study drug or the matching placebo is taken once daily by mouth for 5 consecutive days. This study will last up to 24 weeks. Participants will record their symptoms daily for 29 days, provide blood samples, and have nasopharyngeal swabs (deep nasal swabs) and swabs of the front of the nose (anterior nasal swabs) collected by the study staff. 

In-person visits are planned for screening, on days 1, 4, 8, 16, 29, week 12, week 24, and early discontinuation. An additional in-person visit (if applicable) will be scheduled if symptoms worsen at any time between day 6 and day 29. An extra visit (if applicable) for re-infection after day 29 will take place at the clinic, at home, or another non-clinic location if available. The participant and the study staff can discuss the location for each visit.  

The participant informed consent form will provide details about the study visits. 

Who Can Participate? 

Approximately 2000 participants will take part in the study. 

Eligible participants include outpatient adults (18 years of age or older) with

  • Documented positive SARS-CoV-2 nucleic acid or antigen test from a sample collected at 72 hours (3 days) or less prior to randomization
  • Onset of symptoms of COVID-19 at 3 days or less prior to randomization
  • Presence of 1 or more select COVID-19 symptoms within 24 hours prior to randomization

Participants will be eligible regardless of vaccination status Only standard risk patients will be enrolled in the United States. High-risk participants are defined as those who are 65 years of age or older or those with the presence of high-risk conditions. Standard-risk participants are defined as those not meeting the high-risk definition.  

Where Is It Taking Place?  

243 study sites in North America, South America, Europe, Africa, and Asia. 

Is There a Cost? 

Participants do not have to pay for the study visits or tests. All medications, tests, examinations, and procedures needed only for the study, including the study drugs, will be provided at no cost to the study participants. Study participants will be monitored by an experienced study team at no cost. The study will not supply or pay for medications to treat the symptoms of COVID-19 infection.  

Is Compensation Provided?  

Participants in the study will be compensated for their time and travel. The amount that participants will receive varies by study site. The study staff can provide more details. 

Number of Visits Required 

The study includes 8 visits plus additional visits if symptoms worsen at any time between day 6 and day 29 and/or re-infection occurs after day 29. 

Steps To Participate and Contact Information

Individuals interested in participating in the study can fill out the screening questionnaire on the website ( or call 1-866-516-0188 toll free. The initial eligibility process, including the questionnaire, will take about 5–7 minutes. 


Shionogi & Co., Ltd. 1-8, Doshomachi 3 chome, Chuo-ku, Osaka 541-0045, Japan


Antiviral Research Center 

Brigham and Women's Hospital Therapeutics (BWHT) CRS 

Center for Clinical AIDS Research and Education 

Kara Chew, M.D., M.S. 

Clinical AIDS Research and Education (CARE) Center 

Judith Currier, M.D., M.Sc. 

Eric Daar, M.D. 

Joseph Eron, M.D. 

Courtney Fletcher, Pharm.D. 

Harbor University of California Los Angeles

Linda Harrison, Ph.D. 

Harvard Medical School 

Harvard T.H. Chan School of Public Health 

Michael Hughes, Ph.D. 

Arzhang Javan, M.D., MPH, DTM&H 

Stuart Lacey, M.Sc. 

Jonathan Li, M.D., MMSc 

Annie Luetkemeyer, M.D. 

Simon Portsmouth, M.D., FRCP 

Shionogi B.V.

Shionogi Inc. 

David (Davey) Smith, M.D., MAS 

Statistical and Data Analysis Center 

The University of North Carolina, Chapel Hill 

The University of North Carolina Global HIV Prevention and Treatment 


University of California, Los Angeles 

University of California, San Diego 

University of California, San Francisco  

University of Nebraska Medical Center 

David Wohl, M.D. 

Zuckerberg San Francisco General

Contact Information

Office: Shionogi Clinical Trials Administrator Clinical Support Help Line 

Phone: 1-800-849-9707 


Participating in Research

Watch a series of short informational videos about participating in clinical trials. These videos are intended to help potential participants understand how research works, what questions they should consider asking, and things to think about when deciding whether or not to participate in a study.

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