Long COVIDPhase 2PREVAIL-LCNCT06161688
Ensitrelvir for Viral Persistence and Inflammation in People Experiencing Long COVID
A Phase 2 study testing Ensitrelvir in people with Long COVID and Post Acute Sequelae of COVID-19, run by Timothy Henrich at 1 site in United States.
Trial summary
Persistent viral infection with viral reservoirs and detection of circulating spike protein after the initial acute illness is one potential pathogenic mechanism for Long COVID. This mechanism may be susceptible to antiviral therapy that blocks viral replication, which has the potential to alleviate long COVID… Read more about this study
- Who is it for?
- Ages 18 to 69 years
- Conditions the study is for
- Long COVID, Post Acute Sequelae of COVID-19, Post-Acute COVID-19
- What is being tested?
- Ensitrelvir
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 40 participants
- Where
- 1 siteUnited States
- Study dates
- 9 Apr 2024to 31 Dec 2026
- Phase
- Phase 2
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 69 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Inclusion Criteria (note, additional eligibility criteria not listed here will be assessed at Screening):
- ≥18 and <70 years of age at Screening.
- History of confirmed SARS-CoV-2 infection.
- Long COVID attributed to a SARS-CoV-2 infection
- At least two moderate symptoms or one severe symptom that are new or worsened since the time of a SARS-CoV-2 infection, not known to be attributable to another cause upon assessment by the PI. Symptoms must have been present for at least 60 days prior to screening and must be reported to be at least somewhat bothersome.
- Body mass index (BMI) 18 to 50 kilograms/meter squared (kg/m2), inclusive, at the time of screening.
- Participants who are of childbearing potential (CBP) and male participants with sexual partner(s) who are females of CBP must agree to use adequate contraception from study consent through 14 days after the last dose of study intervention.
Exclusion Criteria (note, additional eligibility criteria not listed here will be assessed at Screening):
- Previously received SARS-CoV-2 antiviral within 90 days prior to planned Day 0 or plan to receive such treatment before exiting the study
- Previously received COVID-19 convalescent plasma treatment within 60 days prior to planned Day 0 or plan to receive such treatment before exiting the study.
- Plans to receive any investigational or approved vaccine or booster for SARS-CoV-2 within 60 days prior to Day 0 or before Day 30 following Day 0.
- Active cardiovascular disease or recent (within 3 months) stroke.
- Recent (within 6 months) or planned major surgery.
- Currently hospitalized or recent (within 1 month) unplanned hospitalization.
- Active Hepatitis B or C infection.
- Known HIV infection.
- Severe coagulopathy (international normalized ratio ((INR) >2.0, history of hemophilia).
- Severe anemia (hemoglobin <9 grams/deciliter (g/dL)).
- Moderate or severe immunocompromise, according to the current NIH COVID-19 Treatment Guidelines as of March 6, 2023.
- History of anaphylaxis or hypersensitivity to any components of the intervention, prescription or non-prescription drugs, or food products in the past.
- Known prior diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), preceding and not related to SARS-CoV-2 infection and not worsened since SARS-CoV-2 infection
- Pregnant, breastfeeding, or unwilling to practice birth control abide by the contraception requirements outlined in the inclusion criteria.
- Participation in a clinical trial with receipt of an investigational product within 28 days prior to Day 0.
- Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data.
Trial locations and contacts
1 site in 1 country.
United States1 site
UCSF/Zuckerberg San Francisco General Hospital
San Francisco, California, 94110
About this study
Official title: Placebo-Controlled, Randomized Trial of Ensitrelvir (S-217622) for Viral Persistence and Inflammation in People Experiencing Long COVID (PREVAIL-LC)
Persistent viral infection with viral reservoirs and detection of circulating spike protein after the initial acute illness is one potential pathogenic mechanism for Long COVID. This mechanism may be susceptible to antiviral therapy that blocks viral replication, which has the potential to alleviate long COVID symptoms. This trial will study the safety and efficacy of Ensitrelvir (S-217622), an antiviral, to treat individuals with Long COVID in an adult population.
Read the detailed description
The study will enroll approximately 40 participants who meet the World Health Organization (WHO) Long COVID criteria. Participants will be enrolled at a single center and randomized 1:1 to receive ensitrelvir fumaric acid (Ensitrelvir: S-217622), given orally for 5 days, or placebo. Subjects randomized to receive Ensitrelvir will take 375 mg on day 1, followed by 125 mg daily for 4 additional days. Evaluations will take place at baseline and at timepoints up to 60 days post-initiation of study drug.
- Being tested
- Ensitrelvir, Placebo
- Keywords
- Antiviral, Viral Persistence
- Medical subject headings
- Post-Acute COVID-19 Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
EnsitrelvirDrug
Also called ensitrelvir fumaric acid
Those randomized to the experimental arm will receive Ensitrelvir, a protease inhibitor, taken orally for 5 days
PlaceboOther
Matching placebo for Ensitrelvir
| Study group | Role | What they receive |
|---|---|---|
| Ensitrelvir (S-217622) | Experimental | Ensitrelvir fumaric acid (S-217622) given orally 375 mg on day 1 followed by 125 mg daily for 4 additional days Receives: Drug: Ensitrelvir |
| Placebo | Placebo comparator | Placebo administered orally for 5 days Receives: Other: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean PROMIS-29 Physical Health Summary Score at 10 post-[ADD]. PROMIS-29 is a validated scale assessing physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social activities, and pain. Each domain is scored on a 5-point scale (without any difficulty, with a little difficulty, with some difficulty, with much difficulty, unable to do). A T-score is calculated from each individual domain. A T score of 50 represents the mean for US general adult population, and 10 is the standard deviation. A lower T score indicates worse physical health.
Measured: Day 10
Secondary outcomes (13)
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean PROMIS-29 Physical Health Summary Score at Day 30 post-randomization. PROMIS-29 is a validated scale assessing physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social activities, and pain. Each domain is scored on a 5-point scale (without any difficulty, with a little difficulty, with some difficulty, with much difficulty, unable to do). A T-score is calculated from each individual domain. A T score of 50 represents the mean for US general adult population, and 10 is the standard deviation. A lower T score indicates worse physical health.
Measured: Day 30
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Mental Health Summary Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean PROMIS-29 Mental Health Summary Score at Day 10 post-randomization. PROMIS-29 is a validated scale assessing physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social activities, and pain. Each domain is scored on a 5-point scale (without any difficulty, with a little difficulty, with some difficulty, with much difficulty, unable to do). A T-score is calculated from each individual domain. A T score of 50 represents the mean for US general adult population, and 10 is the standard deviation. A lower T score indicates worse mental health.
Measured: Day 10
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Mental Health Summary Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean PROMIS-29 Mental Health Summary Score at Day 30 post-randomization. PROMIS-29 is a validated scale assessing physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social activities, and pain. Each domain is scored on a 5-point scale (without any difficulty, with a little difficulty, with some difficulty, with much difficulty, unable to do). A T-score is calculated from each individual domain. A T score of 50 represents the mean for US general adult population, and 10 is the standard deviation. A lower T score indicates worse mental health.
Measured: Day 30
Quality of Life (Global Health Score) on a 100-point Visual-Analogue Scale
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in the baseline adjusted mean Quality of Life 100-point Visual-Analogue-Scale at Day 10 post-randomization. 0 represents the worst health a person can imagine and 100 represents the best health a person can imagine.
Measured: Day 10
Quality of Life Score (5-Item EuroQol EQ-5D-5L) Index Value Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean Quality of Life (5-Item EuroQol EQ-5D-5L) Index Value Score at Day 10 post-randomization. 5-Item EuroQol EQ-5D-5L questions assess pain/difficulty in day-to-day activities over the past week. The 5-Item EuroQol EQ-5D-5L produces a score that typically ranges from 0 - 1, with a higher score indicating better quality of life.
Measured: Day 10
Duke Activity Status Index (DASI)
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean DASI at Day 10 post-randomization. The Duke Activity Status Index is a patient-reported estimate of functional capacity, maximal oxygen consumption (VO2 max) and maximum metabolic equivalent of tasks (METs). The DASI questionnaire produces a score between 0 and 58.2 points, which is linearly correlated with a patient's VO2 max and METs, as measured from cardiopulmonary exercise testing (CPET). It inquires about a person's ability to perform self-care, walk, climb stairs, run, do house and yard work, engage in sexual intercourse, and perform moderate recreational activities. A higher score indicates higher functional capacity.
Measured: Day 10
Orthostatic Hypotension Questionnaire (OHQ) Composite Score
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean OHQ composite score at Day 10 post-randomization.
The Orthostatic Hypotension Questionnaire (OHQ) was developed as a psychometric tool to capture patients' experience quantifying symptomatic burden and functional limitations caused by neurogenic orthostatic hypotension
The OHQ composite score range is 0 -10 with a higher score indicating higher burden.
Measured: Day 10
World Health Organization Disability Assessment Schedule 2.0 (WHO-DAS 2.0) Questionnaire
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean WHO-DAS 2.0 score at Day 10 post-randomization. The World Health Organization Disability Assessment Schedule 2.0 questionnaire asks about difficulties due to health conditions. Health conditions include diseases or illnesses, other health problems that may be short or long lasting, injuries, mental or emotional problems, and problems with alcohol or drugs. The range is scored from 0-48, with a higher score indicating a higher level of disability.
Measured: Day 10
Patient Global Impression of Change (PGIC)
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo on the Patient Global Impression of Change (PGIC) scale at Day 10 post-randomization. The self-reported PGIC reflects a patient's belief about the efficacy of treatment. We used a modified PGIC scale which has been used to study pain syndromes and has been employed in other Long COVID clinical trials. It is a common data element developed by the National Institutes of Mental Health. The PGIC ranges from 0 (Much better) to 10 (Much Worse). A score of 5 indicates no change.
Measured: Day 10
Everyday Cognition Form (ECog-41)
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean ECog-41 score at Day 10 post-randomization. The ECog-41 is an instrument that measures the decline in everyday cognitive and functional abilities that map to six cognitive domains, adapted specifically to describe change in abilities since having COVID. A summary ECog-41 score is calculated scored with a range of 1-4, with a higher score indicating greater cognitive impairment.
Measured: Day 10
6 Minute Walking Test (6MWT)
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean distance walked on the 6MWT at Day 10 post-randomization. The 6MWT requires an individual to walk at their normal pace for 6 minutes on a marked track (for example, a hallway). Vital signs are assessed, and the total distance covered is the primary outcome of interest. A larger distance is regarded as better.
Measured: Day 10
Active Stand Test
The active standing test is a non-invasive tool to assess orthostatic hypotension (OH) and postural orthostatic tachycardia syndrome (POTS). In short, blood pressure and heart rate measurements were obtained after 5 minutes of resting supine and 1, 3, 5, and 10 minutes of continuous standing. A positive active stand test is defined as: those with a decline >20 mmHg in systolic or > 10 mmHg in diastolic blood pressure in at least two consecutive measurements, or those with an increase in heart rate > 30 bpm on two consecutive measurements. Here we evaluate positive active stand tests as a binary outcome (yes, no), comparing the difference in proportion of participants with a positive active stand test at baseline and day 10 between the group treated with Ensitrelvir versus placebo.
Measured: Day 10
Neurocognition Index (NCI) Score From the CNS-VS
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean NCI standard score from the CNS-VS at Day 10 post-randomization The CNS Vital Signs is a a computer-based neurocognitive assessment comprised of seven tests: verbal and visual memory, finger tapping, symbol digit coding, the Stroop Test, a test of shifting attention and the continuous performance test. The battery gives a summary neurocognition index (NCI) score averaging five domain scores (Composite Memory, Psychomotor Speed, Reaction Time, Complex Attention, and Cognitive Flexibility) and representing a global score of neurocognition. NCI scores are normalized scores (mean 100, standard deviation 15) that are age matched relative to other people in a normative sample. A higher score indicates better cognitive function.
Measured: Day 10
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted8 Dec 2023
- Study start9 Apr 2024
- Primary completion20 Dec 2024
- Study completion31 Dec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Long COVIDStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 40 participants (actual)
Sponsor and investigators
- Lead sponsor
- Timothy Henrich
- Sponsor type
- University, hospital or other
- Collaborators
- Shionogi Inc.
- Responsible party
- Sponsor-investigator, Timothy Henrich, University of California, San Francisco
- Investigators
- Timothy Henrich, MD, Principal investigator, University of California, San FranciscoMichael Peluso, MD, Principal investigator, University of California, San Francisco
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06161688
- Sponsor's protocol ID
- 23-38752
- Acronym
- PREVAIL-LC
- Status last verified
- Mar 2026
- First submitted
- 6 Dec 2023
- Last updated
- 2 Apr 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Placebo-Controlled, Randomized Trial of Ensitrelvir (S-217622) for Viral Persistence and Inflammation in People Experiencing Long COVID (PREVAIL-LC)
- ClinicalTrials.gov ID
- NCT06161688
- Acronym / sponsor ID
- PREVAIL-LC / 23-38752
- Keywords
- Antiviral, Viral Persistence
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 40 participants (actual)
- Lead sponsor
- Timothy HenrichUniversity, hospital or other
- Collaborators
- Shionogi Inc.
- Study start
- 9 Apr 2024 (actual)
- Primary completion
- 20 Dec 2024 (actual)
- Study completion
- 31 Dec 2026 (estimated)
- First posted
- 8 Dec 2023 (actual)
- Results
- Posted 2 Apr 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Persistent viral infection with viral reservoirs and detection of circulating spike protein after the initial acute illness is one potential pathogenic mechanism for Long COVID. This mechanism may be susceptible to antiviral therapy that blocks viral replication, which has the potential to alleviate long COVID symptoms. This trial will study the safety and efficacy of Ensitrelvir (S-217622), an antiviral, to treat individuals with Long COVID in an adult population.
Detailed description
The study will enroll approximately 40 participants who meet the World Health Organization (WHO) Long COVID criteria. Participants will be enrolled at a single center and randomized 1:1 to receive ensitrelvir fumaric acid (Ensitrelvir: S-217622), given orally for 5 days, or placebo. Subjects randomized to receive Ensitrelvir will take 375 mg on day 1, followed by 125 mg daily for 4 additional days. Evaluations will take place at baseline and at timepoints up to 60 days post-initiation of study drug.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Ensitrelvir (S-217622) | Experimental | Drug: EnsitrelvirEnsitrelvir fumaric acid (S-217622) given orally 375 mg on day 1 followed by 125 mg daily for 4 additional days |
| Placebo | Placebo comparator | Other: PlaceboPlacebo administered orally for 5 days |
Who may qualify
- Ages
- 18 to 69 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| EnsitrelvirAlso: ensitrelvir fumaric acidThose randomized to the experimental arm will receive Ensitrelvir, a protease inhibitor, taken orally for 5 days | Drug | Ensitrelvir (S-217622) |
| PlaceboMatching placebo for Ensitrelvir | Other | Placebo |
Primary outcome
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score
Time frame: Day 10
This measure will evaluate whether there is a difference between treatment with Ensitrelvir versus placebo in baseline adjusted mean PROMIS-29 Physical Health Summary Score at 10 post-[ADD]. PROMIS-29 is a validated scale assessing physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social activities, and pain. Each domain is scored on a 5-point scale (without any difficulty, with a little difficulty, with some difficulty, with much difficulty, unable to do). A T-score is calculated from each individual domain. A T score of 50 represents the mean for US general adult population, and 10 is the standard deviation. A lower T score indicates worse physical health.
13 secondary outcomes
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score
Time frame: Day 30
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Mental Health Summary Score
Time frame: Day 10
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Mental Health Summary Score
Time frame: Day 30
Quality of Life (Global Health Score) on a 100-point Visual-Analogue Scale
Time frame: Day 10
Quality of Life Score (5-Item EuroQol EQ-5D-5L) Index Value Score
Time frame: Day 10
Duke Activity Status Index (DASI)
Time frame: Day 10
Orthostatic Hypotension Questionnaire (OHQ) Composite Score
Time frame: Day 10
World Health Organization Disability Assessment Schedule 2.0 (WHO-DAS 2.0) Questionnaire
Time frame: Day 10
Patient Global Impression of Change (PGIC)
Time frame: Day 10
Everyday Cognition Form (ECog-41)
Time frame: Day 10
6 Minute Walking Test (6MWT)
Time frame: Day 10
Active Stand Test
Time frame: Day 10
Neurocognition Index (NCI) Score From the CNS-VS
Time frame: Day 10
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Apr 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Individual participant dataSharing planned: No
Related trials for Long COVID
Not yet recruitingPhase 1
Phase I Open-Label Safety Trial of Pembrolizumab for Neurological Post- Acute Sequelae of SARS-CoV-2 (PD1-PASC I)
Post-Acute COVID-19 Syndrome
Recruiting
Whole-body Cryotherapy in Those With Chronic Fatigue: A Feasibility Study
ME/CFS, Fibromyalgia (FM)
Not yet recruitingPhase 3
The Study of Brave-LC LDN Treatment Trial
Post-acute COVID-19 Syndrome
Active, not recruitingObservational study
Epigenetic Changes in Long COVID Patients
Long COVID-19 Syndrome, Long COVID Symptoms
Enrolling by invitationPhase 2
Immunotherapy for Neurological Post-Acute Sequelae of SARS-CoV-2
Systemic Inflammation, Neuroinflammation
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Timothy Henrich, MD principal investigator
University of California, San Francisco
Michael Peluso, MD principal investigator
University of California, San Francisco
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Ensitrelvir in people with Long COVID and Post Acute Sequelae of COVID-19, run by Timothy Henrich at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 2 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 2 Apr 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score (time frame: Day 10). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Apr 2026.