A Phase 2 interventional study of Nirmatrelvir/ritonavir (e.g. PAXLOVID™) and Nitazoxanide in COVID-19, sponsored by University of Oxford. Recruiting at 7 sites in 5 countries. Open to participants aged 18 Years to 60 Years. Per ClinicalTrials.gov, last updated 2026-02-19.
Sponsored by University of Oxford · Phase 2, Interventional, and Treatment
The trial will develop and validate a platform for quantitative assessment of antiviral effects in low-risk patients with high viral burdens and uncomplicated COVID-19 to determine in-vivo antiviral activity. In this randomized open label, controlled, group sequential adaptive platform trial, we will assess the performance of three distinct types of intervention relative to control (no treatment):
A: Small molecule drugs; B: Monoclonal antibodies; C: Dose finding for the constituent parts of nirmatrelvir/ritonavir
PLATCOV study is supported by the Wellcome Trust Grant ref: 223195/Z/21/Z through the COVID-19 Therapeutics Accelerator.
The platform trial will assess drugs with potential SARS-CoV-2 antiviral activity of three general types:
A. Small molecule drugs: currently nitazoxanide, nirmatrelvir/ritonavir, hydroxychloroquine, atilotrelvir/ritonavir and metformin.
B. Monoclonal antibodies: Sotrovimab and any other monoclonal antibodies that become available. Monoclonal antibodies are vulnerable to viral escape mutations. Tracking their performance over time is important to characterise the impact and inform the therapeutics of mutant SARS-CoV-2 strains. This will also be important for other antivirals. Monoclonal antibodies are expensive and cannot be produced at large scale currently, but this may change in the near future. These drugs will be included if there is local availability and regulatory approval.
C. : Dose finding for the constituent parts of nirmatrelvir/ritonavir. Nirmatrelvir/ritonavir has shown clinical efficacy in phase III studies, however, there are disadvantages to using it (drug-drug interactions, side effects, cost). In the urgent context of the pandemic, a higher dose of ritonavir was chosen to guarantee maximum boosting effect. We do not know if the maximal boosting effect could have been achieved with less, or even without ritonavir. It will be investigated whether reducing the doses of the constituent parts can still retain the effectiveness.
Randomization to the no antiviral treatment control arm (no intervention) will be fixed at a minimum of 20% throughout the study. The randomization ratios will be uniform for all available interventions.
Recruitment into the ivermectin arm was stopped on April 18th 2022 due to meeting the pre- defined stopping criteria.
Recruitment into the remdesivir arm was stopped on June 10th 2022 due to meeting the pre- defined stopping criteria.
Recruitment into the REGN-COV2 arm was stopped on October 20th 2022 due to meeting the pre-defined stopping criteria.
Recruitment into the favipiravir arm was stopped on October 31st 2022 due to meeting the pre-defined stopping criteria.
Recruitment into the molnupiravir arm was stopped on February 22nd 2023 due to meeting the pre-defined stopping criteria.
Recruitment into the fluoxetine arm was stopped on May 8th 2023 due to meeting the pre-defined stopping criteria.
Recruitment into the evusheld arm was stopped on July 4th 2023 due to meeting the pre-defined stopping criteria.
Recruitment into the ensitrelvir arm was stopped on April 21st 2024 due to meeting the pre-defined stopping criteria.
Recruitment into the combination molnupiravir and nirmatrelvir/ritonavir (e.g. PAXLOVID™) arm was stopped on May 31st 2024 due to meeting the pre-defined stopping criteria.
7,990 studies on the registry are indexed under COVID-19; 466 are open to participants now.
This study's planned enrollment of 3,800 is above the median of 102 across 4,364 interventional studies indexed under COVID-19.
Browse COVID-19 studies →University of Oxford is the lead sponsor of 812 studies on the registry; 119 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
The patient may not enter the study if ANY of the following apply:
Evidence of pneumonia (although imaging is NOT required)
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Drug: Nirmatrelvir/ritonavir (e.g. PAXLOVID™)
Drug: Nitazoxanide
Drug: Molnupiravir and nirmatrelvir/ritonavir (e.g. PAXLOVID™)
Drug: Hydroxychloroquine
Other: No treatment
Drug: Monoclonal antibodies
Drug: Fluoxetine
Drug: Molnupiravir
Drug: Sotrovimab
Drug: Ensitrelvir
Drug: Monoclonal antibodies
Drug: Favipiravir
Drug: Ivermectin
Drug: Remdesivir
Drug: Atilotrelvir/ritonavir
Drug: Metformin
Drug: Nirmatrelvir/ritonavir
Drug: Nirmatrelvir/ritonavir
Drug: Nirmatrelvir
Nirmatrelvir 300mg BD for 5/7 Ritonavir 100mg BD for 5/7
Nitazoxanide 1.5g BD 7/7
Drug pages: Molnupiravir · Nirmatrelvir · Ritonavir
Molnupiravir 800mg BD for 5/7, Nirmatrelvir 300mg BD for 5/7, Ritonavir 100mg BD for 5/7
Hydroxychloroquine 400mg D0 BD and 400MG OD for a further 6/7
No treatment (except antipyretics- paracetamol)
Monoclonal antibodies: 300mg tixagevimab/ 300 mg cilgavimab given once on D0
Fluoxetine 40mg OD for 7/7
Molnupiravir 800mg BD for 5/7
Sotrovimab 500mg given once on D0
Ensitrelvir 375mg OD D0 and 125mg OD for a further 4/7
Monoclonal antibodies: 600mg casirivimab/ 600mg imdevimab given once on D0
Favipiravir 1800mg BD D0 and 800mg BD for a further 6/7
Ivermectin 600micrograms/kg/day for 7/7.
Remdesivir 200mg D0 and 100mg for a further 4/7.
Drug pages: Atilotrelvir · Ritonavir
Atilotrelvir 150mg BD for 5/7 Ritonavir 100mg BD for 5/7
Metformin 500mg TDS 5/7
Nirmatrelvir 300mg BD for 5/7 Ritonavir 50mg BD for 5/7
Nirmatrelvir 150mg BD for 5/7 Ritonavir 50mg BD for 5/7
Nirmatrelvir 300mg BD for 5/7
Rate of viral clearance for interventions relative to the no study arm (This is a superiority comparison)
Rate of viral clearance- estimated from the log10 viral density derived from qPCR of standardised duplicate oropharyngeal swabs/ saliva taken daily from baseline (day 0) to day 5 for each intervention compared with the no antiviral treatment control i.e., those not receiving study drug
Time frame: Days 0-5
Rate of viral clearance for interventions relative to the positive control arm (This is a non-inferiority or superiority comparison).
Rate of viral clearance- estimated from the log10 viral density derived from qPCR of standardised duplicate oropharyngeal swabs/ saliva taken daily from baseline (day 0) to day 5 for interventions compared with the current best antiviral treatment option (accelerated viral clearance relative to the positive control arm)
Time frame: Days 0-5
Viral kinetic levels in early COVID-19 disease
Rate of viral clearance estimated from the log10 viral density derived from qPCR of standardised duplicate oropharyngeal swabs/ saliva taken daily from baseline (day 0) to day 5 for each therapeutic arm compared with the no antiviral treatment control i.e., those not receiving study drug
Time frame: Days 0-5
Optimal dosing regimens through pharmacometric assessment for antiviral drugs with evidence of efficacy in the literature or from the trial data (e.g., Nirmatrelvir/ritonavir, Ensitrelvir etc).
Rate of viral clearance- estimated from the log10 viral density derived from qPCR of standardised duplicate oropharyngeal swabs/ saliva taken daily from baseline (day 0) to day 5 for each therapeutic arm compared with the no antiviral treatment control i.e., those not receiving study drug
Time frame: Days 0-5
Viral rebound of studied treatment arms in comparison to contemporaneous controls (e.g. no study drug arm, positive control)
After stopping treatment for at least 24 hours (or 5 days if no drug is given or a single dose monoclonal antibody is given), rebound is defined as an oropharyngeal eluate viral density estimate \>1000 genomes per ml for at least 1 timepoint (average 2 swabs), after \>2 consecutive days of average daily viral density estimate less than 100 genomes per ml
Time frame: Days 6-14
Rates of fever clearance and symptom resolution with respect to no treatment
The following endpoints will be used: * Time to resolution of fever * Area Under the Curve of recorded temperature * Time to resolution of symptoms
Time frame: Days 0-14
Rates of hospitalisation by treatment arm (hospitalisation for clinical reasons)
Number of hospitalisations up to Day 28 in a treatment arm with an increased rate of viral clearance compared with the negative control i.e. patients not receiving study drug
Time frame: Days 0-28
Relationship between viral clearance, randomisation arm and other measures (covariates) and development of post- acute COVID-19 (i.e. long COVID)
Score on post-acute COVID-19 (i.e. long COVID) questionnaire at day 120 - modified COVID-19 Yorkshire Rehabilitation Scale (C19 YRSm)
Time frame: Days 0-120
Not enrolling at this site.
Not enrolling at this site.
Not enrolling at this site.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Yes — With patient's consent, clinical data and results from blood analyses stored in the database may be shared according to the terms defined in the MORU data sharing policy with other researchers to use in the future. Data generated from this study will adhere to the 2016 "Statement on data sharing in public health emergencies"(https://wellcome.ac.uk/press-release/statement-data-sharing-public-health-emergencies).
Supporting information: Clinical study report, Analytic code
Time frame: after the main paper has been published
Access criteria: MORU Data Sharing Policy https://www.tropmedres.ac/units/moru-bangkok/bioethics-engagement/data-sharing. The criteria for authorship will be consistent with the international guidelines (http://www.icmje.org/#author).
Data sharing details ↗ · wellcome.ac.uk
Started Sep 2021 (actual). Primary completion is estimated for Jan 2027, 64 months after the start.
Of 359 non-industry phase 2 interventional studies under COVID-19, half reached primary completion within 11 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 18. This study's planned 64 months is above that.
Counting every sponsor, half of 582 studies reached it within 9 months; a quarter within 5 and three quarters within 16.
How these figures are worked out, and which studies are left out of them.
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Studies of the drugs tested here: Nitazoxanide · Molnupiravir · Nirmatrelvir · Ritonavir · Hydroxychloroquine · Antibodies, Monoclonal · Fluoxetine · Sotrovimab · Ensitrelvir · Favipiravir · Ivermectin · Remdesivir · Atilotrelvir · Metformin