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OpenTrials
Completed

NCT Number: NCT05576662

Paxlovid for Treatment of Long Covid

The purpose of this study is to compare whether being treated with nirmatrelvir plus ritonavir for 15 days works better than being treated with placebo plus ritonavir to reduce severe symptoms of Long Covid.

Participants will have 5 planned visits to the study clinic over 15 weeks and will take the drug (or placebo) for the first 15 days.

This study uses the term post-acute sequelae of SARS-CoV-2 (PASC), which is another name for "Long Covid."

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Key information

About this study

An exploratory sub-study will investigate the correlation of physical activity and biometric parameters from digital wearable devices with the subjective symptom severity and other patient-reported outcomes in the main study. All participants with iPhone 6S Plus or newer will be offered an opportunity to opt-in to this sub-study. An Apple Watch and Bluetooth-enabled blood pressure monitor will be provided to participants and data will be collected for the duration of the main study to track participants' physiological and behavioral trends in the Paxlovid versus placebo groups.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Normal or near-normal kidney function
  • History of confirmed COVID-19 infection that preceded the post-COVID symptoms
  • Post-COVID-19 symptoms persisting greater than three months
  • At least 2 post-COVID symptoms of moderate or severe intensity (fatigue, brain fog, shortness of breath, body aches, gastrointestinal symptoms, or cardiovascular symptoms)
  • Willing to report all vaccinations
  • Women of childbearing potential or men whose partners may become pregnant must use acceptable method of contraception during the treatment period and for 28 days after the last dose of the study drug
  • Willing and able to adhere to study procedures and available for the duration of the study

Exclusion criteria

  • Suspected or confirmed pregnancy or breastfeeding
  • Severe liver disease
  • Prior use of study drug or other COVID treatment within 30 days
  • Hypersensitivity or other contraindication to any components of the study drug
  • Current or expected use of any medication dependent on or inducer of CYP3A4
  • Current or expected use of supplements or herbs (unless medically necessary) that cannot be temporarily held (period as determined necessary by investigators)
  • HIV infection with viral load >50 copies/ml
  • Suspected or confirmed active COVID infection within 30 days
  • History of COVID vaccine within 28 days prior to enrollment, or other vaccine (influenza, shingles, etc.) within 14 days of enrollment, or planned use of any vaccine until the primary endpoint has been met (10 weeks)
  • Other medical condition(s) or concomitant therapy that would compromise participant's safety or compliance with the study protocol or significantly confound interpretation of study results, as determined by study investigators
  • Current enrollment in, or discontinuation within the last 30 days from, a clinical trial involving any investigational drug or device
  • Inability to provide informed consent
  • Currently hospitalized

Treatment and study plan

nirmatrelvir

Drug

Two 150 mg tablets taken by mouth every 12 hours

Placebo

Drug

Two tablets containing placebo matching nirmatrelvir taken by mouth every 12 hours

Ritonavir

Drug

One 100 mg capsule taken by mouth every 12 hours

Primary outcomes

  1. Number of Participants With No, Mild, Moderate, or Severe Symptoms at Week 10 According to the Core Symptoms Severity Scale Score

    Time frame: Week 10

    This measure was to evaluate whether there is a difference between treatment with Paxlovid versus placebo on any of the 6 core symptoms of PASC at week 10 (adjusting for patients' baseline levels). Each symptom (fatigue, brain fog, dyspnea, body aches, gastrointestinal symptoms, cardiovascular symptoms) was assessed on a 4-point Likert scale (range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms).

Secondary outcomes

  1. Number of Participants With No, Mild, Moderate, or Severe Symptoms at Day 15 According to the Core Symptoms Severity Scale Score

    Time frame: Day 15

    This measure was to evaluate whether there is a difference between treatment with Paxlovid versus placebo on any of the 6 core symptoms of PASC at week 10 (adjusting for patients' baseline levels). Each symptom (fatigue, brain fog, dyspnea, body aches, gastrointestinal symptoms, cardiovascular symptoms) was assessed on a 4-point Likert scale (range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms).

  2. Number of Participants Reporting Relief of at Least One Core Symptom for 2 Weeks

    Time frame: Baseline through week 10, assessed at week 10

    Relief defined as reduction of severity from moderate to none, or severe to mild/none (≥ 2-point Likert score change). Likert score range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms.

  3. Number of Participants With Overall Alleviation for 2 Weeks

    Time frame: Baseline through week 10, assessed at week 10

    Overall alleviation defined as both:

    • Any core symptom(s) that are none/mild (Likert 0 or 1) at baseline are none at 10 weeks, and
    • Any core symptom(s) that are moderate/severe (Likert 2 or 3) at baseline are none/mild at 10 weeks.

    Likert score range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms.

  4. Number of Participants With No, Mild, Moderate, or Severe Symptoms of Their Most Bothersome Symptom

    Time frame: Assessed at weeks 5, 10, and 15

    This outcome was to assess the severity of the most bothersome symptom experienced by participants. Each symptom was assessed on a 4-point Likert scale (range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms) using the Core Symptoms Severity Scale.

  5. Time to Relief of the 6 Core Symptoms

    Time frame: Up to 15 weeks

    Relief defined as reduction of severity from moderate to none, or severe to mild/none for 2 consecutive weeks (≥ 2-point Likert score change). Likert score range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms.

  6. Time to Relief of the Most Bothersome Symptom

    Time frame: Up to 15 weeks

    Relief defined as reduction of severity from moderate to none, or severe to mild/none for 2 consecutive weeks (≥ 2-point Likert score change). Likert score range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms.

  7. Change in Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function T-Score

    Time frame: Baseline and week 10

    The PROMIS-Physical Function Short Form (SF) assesses difficulty level performing activities of daily living such as doing chores, climbing stairs, walking, and running errands. The assessment consists of 4 items (questions) with each item scored on 5-point Likert scale (higher scores correspond to better physical function). Scores are computed to a T-score metric, where 50 represents the mean for US general adult population and 10 is the standard deviation. A higher physical function T-score indicates better physical function.

  8. Change in PROMIS Fatigue T-Score

    Time frame: Baseline and week 10

    The PROMIS Fatigue Score assesses level of fatigue and its interference on daily activities. The assessment consists of 7 items (questions) with each item scored on 5-point Likert scale (higher scores correspond to more fatigue). Scores are computed to a T-score metric, where 50 represents the mean for US general adult population and 10 is the standard deviation. A higher fatigue T-score indicates greater fatigue.

  9. Change in PROMIS Dyspnea-Severity T-Score

    Time frame: Baseline and week 10

    The PROMIS-Fatigue Dyspnea-Severity Short Form assesses shortness of breath and its interference on daily activities. The assessment consists of 5 items (questions) scored on 4-point Likert scale with a 7-day recall period (higher scores correspond to worse symptoms). Scores are computed to a T-score metric, where 50 represents the mean for US general adult population and 10 is the standard deviation. A higher Dyspnea-Severity T-score indicates worse symptoms.

  10. Change in PROMIS Cognitive Function Abilities T-Score

    Time frame: Baseline and week 10

    The PROMIS-Cognitive Function Abilities Short Form assesses brain fog and its interference on daily activities. The assessment consists of 4 items scored on 5-point Likert scale with a 7-day recall period (higher scores indicate better cognitive function). Scores are computed to a T-score metric, where 50 represents the mean for US general adult population and 10 is the standard deviation. A higher Cognitive Function T-score indicates better cognitive function.

  11. Change in Orthostatic Vitals Test

    Time frame: Baseline and week 10

    This outcome measures the difference in supine to standing systolic blood pressure (SBP) and diastolic blood pressure (DBP).

  12. Change in Heart Rate

    Time frame: Baseline and week 10

    This outcome measures the difference in supine to standing heart rate.

  13. Change in 1-minute Sit-to-stand Test

    Time frame: Baseline and week 10

    Number of times participant is able to go from sitting (in an armless chair) to standing in 1 minute (sit to stand cycles).

  14. Patient Global Impression of Severity (PGIS) Scale Score

    Time frame: Day 15, and weeks 5, 10, and 15

    The PGIS reflects a participant's perception about the overall severity of their disease symptoms, rated from 1 to 6 (1 = not present; 2 = very mild; 3 = mild; 4 = moderate; 5 = severe; 6 = extremely severe).

  15. Patient Global Impression of Change (PGIC) Scale Score

    Time frame: Day 15, and weeks 5, 10, and 15

    The PGIC reflects a participant's perception about the overall efficacy of treatment and their overall status since the start of the treatment, rated from 1 to 7 (1 = very much improved; 2 = much improved; 3 = minimally improved; 4 = no change; 5 = minimally worse; 6 = much worse; 7 = very much worse).

  16. Summative Severity Score for All Core Symptoms

    Time frame: Weeks 5, 10, and 15

    Core Symptoms Severity Scale Scores for each of the 6 core symptoms were summed to create a summative score. Each core symptom is assessed on a 4-point Likert scale (range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms). Summative score range: 0 to 18 (high scores correspond to greater severity).

  17. Percentage of Weeks 1-15 With Mild or no Symptoms

    Time frame: 15 weeks

    Each symptom (fatigue, brain fog, dyspnea, body aches, gastrointestinal symptoms, cardiovascular symptoms) is assessed on a 4-point Likert scale (range: 0 to 3; 0 = no symptoms; 1 = mild symptoms; 2 = moderate symptoms; 3 = severe symptoms).

Sponsors and collaborators

Lead sponsor

Stanford University

Other

Collaborators

  • Pfizer

Registry information

Official study title

Selective Trial Of Paxlovid for PASC (STOP-PASC): Randomized Double-Blind Placebo-Controlled Pilot Trial of Paxlovid for the Treatment of PASC

Acronym: STOP-PASC

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
Oct 12, 2022
Registry last updated
Sep 4, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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