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Molnupiravir

Phase 3

Coronavirus Disease (COVID-19) | Small molecule | Infectious Disease |Merck & Company, Inc.|Last Updated: Jul 6, 2026

Success Probability
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Market & Valuation
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Trial Design
RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials3
Total Enrollment7,258
FDA Designations
No designations recorded
Clinical trial landscape

Molnupiravir · 7 trials · 5 indications

Phase 3 2Phase 2 2Phase 1 3
NCT06667700A Clinical Study of Molnupiravir to Prevent Severe Illness From Coronavirus Disease 2019 (COVID-19) in People Who Are High Risk (MK-4482-023)Coronavirus Disease (COVID-19)
RECRUITING3,082 Analytics
NCT04939428Study of MK-4482 for Prevention of Coronavirus Disease 2019 (COVID-19) in Adults (MK-4482-013)Coronavirus Disease (COVID-19)
COMPLETED2,441 Analytics
PHASE3RECRUITING
A Clinical Study of Molnupiravir to Prevent Severe Illness From Coronavirus Disease 2019 (COVID-19) in People Who Are High Risk (MK-4482-023)
Coronavirus Disease (COVID-19)Unlock trial analytics
PHASE3COMPLETED
Study of MK-4482 for Prevention of Coronavirus Disease 2019 (COVID-19) in Adults (MK-4482-013)
Coronavirus Disease (COVID-19)Unlock trial analytics
Study Endpoints
Primary Endpoints
Percentage of Participants Who Experienced One or More of Following Through Day 29: All-cause Hospitalization, All-cause Mortality, or Covid-19-related Medically-attended Visit (MAV)
Up to 29 days

Hospitalization is defined as ≥24 hours of acute care in a hospital or similar acute care facility, including emergency rooms or facilities created to address hospitalization needs specifically for COVID-19. Hospitalization and death may be due to any cause. An MAV is defined as any unscheduled, nonroutine healthcare visit where the participant is evaluated by a licensed (according to local/national guidelines) healthcare provider. As prespecified by the protocol, the percentage of participants who experience ONE OR MORE of these 3 events (hospitalization, death, or COVID-19-related MAV) occurring from randomization through Day 29 will be presented.

Percentage of Participants Who Experienced an Adverse Event (AE)
Up to approximately 5 months

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The percentage of participants with at least 1 AE will be presented.

Percentage of Participants Who Discontinued Study Intervention Due to AE
Up to approximately 5 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The percentage of participants who discontinue study intervention due to an AE will be presented.

Percentage of Participants Who Had Undetectable SARS-CoV-2 in Baseline Nasopharyngeal (NP) Swabs and Developed COVID-19 (Laboratory-Confirmed SARS-CoV-2 Infection With Symptoms) Through Day 14
Day 14

Percentage of participants who had undetectable SARS-CoV-2 in baseline NP swabs and developed COVID-19 (laboratory-confirmed SARS-CoV-2 infection with symptoms) through Day 14 were reported.

Percentage of Participants With ≥1 Adverse Event
29 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Percentage of Participants Discontinuing From Study Therapy Due to AE
Up to 5 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Panel A vs Panel C: Peak Viral Load (PVL) Determined by Viral Quantitative Culture
From Day 2 up to Day 12

PVL was defined as the maximum viral load during a specified time period. PVL determined by viral quantitative culture (plaque assay) was measured from Day 2 up to Day 12 (end of participant quarantine). PVL (on the log10 scale) of RSV A Memphis 37b determined by viral quantitative culture (plaque assay) between Day 2 and Day 12 am after intranasal inoculation (Day 0) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

Panel B vs. Panel C: Area Under the Viral Load-time Curve (VL-AUC) Determined by Viral Quantitative Culture
From Day 2 up to Day 12

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by viral quantitative culture (plaque assay) from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) were included in the model. For both panels, only the participants with RSV infection were included.

Percentage of Participants Who Were Hospitalized and/or Died Through Day 29 (Primary Pre-specified Analysis)
Up to 29 days

The percentage of participants who were hospitalized and/or died through Day 29 is presented. Hospitalization (all cause) is defined as at least 24 hours of acute care in a hospital or similar acute care facility. Death was due to any cause. Any participants with an unknown survival status at Day 29 were treated as failure. The analysis in Part 2 was based on all participants enrolled by the pre-specified futility/early efficacy analysis and was used for demonstration of superiority to placebo for the primary efficacy outcome measure.

Number of Participants With an Adverse Event (AE)
Up to 318 days

The number of participants with at least 1 AE is presented. An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Number of Participants Who Discontinued Study Intervention Due to an AE
Up to 5 days

The number of participants who discontinued study intervention due to an AE is presented. An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Part 1: Infectivity Rate Based on Quantitative Reverse Transcriptase-Polymerase Chain Reaction (qRT-PCR) From Day 1 PM Through Day 8 AM
From Day 1 PM up to Day 8 post viral inoculation

Infectivity rate was defined as the number of participants with two quantifiable (≥lower limit of quantitation (LLOQ)) influenza challenge virus (A/France/759/21 \[H1N1\] strain) qRT-PCR measurements reported on ≥2 independent nasopharyngeal samples (from nasal wash samples collected twice daily - morning and evening). Infectivity rate based on qRT-PCR in Part 1 participants from baseline (day 1 PM - afternoon) up to planned discharge from quarantine (day 8 AM - post viral inoculation) is presented. Per protocol, only data for part 1 participants were presented for this endpoint.

Part 1: Infectivity Rate Based on Quantitative Reverse Transcriptase-Polymerase Chain Reaction (qRT-PCR) From Day 2 PM Through Day 8 AM
From Day 2 PM up to Day 8 post viral inoculation

The number of participants with two quantifiable (≥lower limit of quantitation (LLOQ)) influenza challenge virus qRT-PCR measurements reported on ≥2 independent nasopharyngeal samples (from nasal wash samples collected twice daily - morning and evening). Infectivity rate based on qRT-PCR in Part 1 participants from day 2 PM up to day 8 post viral inoculation is presented. Per protocol, only data for part 1 participants were presented for this endpoint.

Part 1: Number of Participants Experiencing ≥1 Viral Challenge-related Adverse Event (AE)
Up to approximately 31 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE is viral challenge-related as determined by the investigator. Number of participants experiencing ≥1 viral challenge-related AE in part 1 is presented. Per protocol, only data for part 1 participants were presented for this endpoint.

Part 2: Peak Viral Load (PVL) Determined by Quantitative Viral Culture Tissue Culture Infective Dose 50% (TCID50) Assay From Day 1 PM Through Day 8 AM After Intranasal Inoculation (Molnupiravir PEP and Placebo)
From Day 1 PM up to Day 8 post viral inoculation

PVL was defined as the maximum viral load of influenza challenge virus from nasopharyngeal samples (nasal wash samples collected twice daily - morning and evening). PVL as determined by quantitative viral culture (QVC) was measured starting from day 1 PM (baseline) up to planned discharge from quarantine (day 8 AM). PVL of the H1N1 strain was measured by quantitative viral culture (QVC) using TCID50 plaque assay and analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only data for Molnupiravir PEP and placebo were presented for this endpoint.

Part 2: Area Under the Viral Load-Time Curve (VL-AUC) Determined by QVC (TCID50 Assay) From Day 2 AM Through Day 8 AM After Intranasal Inoculation (Molnupiravir Tx and Placebo)
Days 2, 3, 4, 5, 6, 7 - twice daily (AM and PM), and day 8 AM post viral inoculation

VL-AUC is the area under the viral load-time curve of influenza challenge virus nasopharyngeal samples determined by QVC. H1N1 viral load was computed for each participant from nasopharyngeal samples collected twice daily (morning and evening) from day 2 AM to day 8 AM. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only data for Molnupiravir Tx and placebo were presented for this endpoint.

Area Under the Curve From Time 0 to Infinity (AUC0-inf) of N-hydroxycytidine (NHC)
Predose, 0.5,1.5, 2, 4, 6, 8, 12, 24, 48 and 72 hours postdose

Blood for plasma samples was collected at pre-specified time points to determine the AUC0-inf of NHC.

Maximum Plasma Concentration (Cmax) of NHC
Predose, 0.5,1.5, 2, 4, 6, 8, 12, 24, 48 and 72 hours postdose

Blood for plasma samples was collected at pre-specified time points to determine the Cmax of NHC.

Number of Participants Who Experienced an Adverse Event (AE)
Up to Day 15

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was therefore any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The number of participants who experienced an AE were reported.

Area Under the Plasma Concentration-Time Curve From Time Zero to Infinity (AUC0-∞) of Plasma N-Hydroxycitidine (NHC)
Day 1: Predose and 0.5, 1.5, 2, 4, 6, 8, 12, 24, 48, and 72 hours postdose

The plasma AUC0-∞ of NHC is reported.

Secondary Endpoints
Time to Sustained Alleviation (without relapse) of all selected 8 (5 prespecified and 3 determined by baseline prevalence), self-reported COVID-19 signs/symptoms
Up to 29 days
Change from Baseline in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) RNA Titer
Day 1 (baseline) and up to Day 29
Percentage of Participants with Undetectable SARS-CoV-2 RNA
Up to 29 days
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Study Design & Arms
AllocationRANDOMIZED
MaskingDOUBLE
ModelPARALLEL
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
MolnupiravirEXPERIMENTALParticipants will receive 800 mg molnupiravir orally every 12 hours for 5 days (a total of 10 consecutive doses)
PlaceboPLACEBO_COMPARATORParticipants will receive molnupiravir-matching placebo orally every 12 hours for 5 days (a total of 10 consecutive doses)
Panel A: Molnupiravir ProphylaxisEXPERIMENTALParticipants received molnupiravir 800 mg every 12 hours for 5 days beginning on Day -1, and are inoculated with RSV-A Memphis 37b on Day 0. Participants switch to placebo beginning on the evening of Day 4 to the morning of Day 10.
Panel B: Molnupiravir Triggered TreatmentEXPERIMENTALParticipants received placebo on Day -1, are inoculated with RSV-A Memphis 37b on Day 0, and continue to receive placebo until testing positive for RSV. Participants then received 800 mg of molnupiravir every 12 hours for 5 days.
Panel C: Matched PlaceboPLACEBO_COMPARATORParticipants received placebo beginning on Day -1, are inoculated with RSV-A Memphis 37b on Day 0, and continue receiving placebo until the morning of Day 10.
Part 1: Molnupiravir 200 mgEXPERIMENTAL200 mg molnupiravir administered orally every 12 hours for 5 days (10 doses total)
Part 1: Molnupiravir 400 mgEXPERIMENTAL400 mg molnupiravir administered orally every 12 hours for 5 days (10 doses total)
Part 1: Molnupiravir 800 mgEXPERIMENTAL800 mg molnupiravir administered orally every 12 hours for 5 days (10 doses total)
Part 1: PlaceboPLACEBO_COMPARATORPlacebo matching molnupiravir administered orally every 12 hours for 5 days (10 doses total)
Part 2: Molnupiravir 800 mgEXPERIMENTAL800 mg Molnupiravir (dose to be selected) administered orally every 12 hours for 5 days (10 doses total)
Part 2: PlaceboPLACEBO_COMPARATORPlacebo matching molnupiravir administered orally every 12 hours for 5 days (10 doses total)
Panel A: Molnupiravir Post-Exposure Prophylaxis (Part 2)EXPERIMENTALMolnupiravir 800 mg every 12 hours Day 0 PM through Day 5 AM, placebo molnupiravir every 12 hours Day 5 PM through Day 6 PM
Panel B: Molnupiravir Treatment (Part 2)EXPERIMENTALPlacebo molnupiravir every 12 hours Day 0 PM through Day 1 PM, molnupiravir 800 mg every 12 hours Day 2 AM through Day 6 PM
Panel C: Oseltamivir Treatment (Part 2)ACTIVE_COMPARATORPlacebo oseltamivir Day 0 PM through Day 1 PM, oseltamivir 75 mg plus placebo so the total number of capsules is always 4 per dose every 12 hours Day 2 AM through Day 6 PM
Panel D: Molnupiravir Placebo (Part 2)PLACEBO_COMPARATORPlacebo molnupiravir every 12 hours Day 0 PM through Day 6 PM
Virus Inoculation (Part 1 & 2)EXPERIMENTALInfluenza A challenge virus given once by intranasal administration
Panel A - Severe Renal Impairment GroupEXPERIMENTALParticipants with severe renal impairment will receive a single oral 800 mg dose of molnupiravir.
Panel B - Healthy Control GroupEXPERIMENTALParticipants in the healthy mean matched control group will receive a single oral 800 mg dose of molnupiravir.
Moderate Hepatic ImpairmentEXPERIMENTALParticipants with moderate hepatic impairment received a single oral dose of molnupiravir 800 mg on Day 1.
Healthy-Matched Control GroupEXPERIMENTALHealthy matched participants received a single oral dose of molnupiravir 800 mg on Day 1.
Interventions
NameTypeDescription
MolnupiravirDRUGMolnupiravir administered orally as two 400 mg film-coated tablets every 12 hours for 5 days (a total of 10 consecutive doses)
PlaceboDRUGMolnupiravir-matching placebo administered orally as two film-coated tablets every 12 hours for 5 days (a total of 10 consecutive doses)
RSV A Memphis 37bBIOLOGICALRSV A Memphis 37b viral challenge given once by intranasal administration at a dosage of \~4 Log10 plaque forming units (PFUs).
Placebo molnupiravirDRUGFour placebo capsules matched to molnupiravir taken twice daily by mouth.
Placebo oseltamivirDRUGPlacebo capsule matched to oseltamivir taken twice daily by mouth.
OseltamivirDRUGOne capsule of oseltamivir 75 mg taken twice daily by mouth.
Influenza A VirusBIOLOGICALInfluenza A challenge virus given once by intranasal administration at an inoculum concentration of between approximately 5 and 7 Log10 tissue culture infective dose 50% (TCID50/mL).
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Eligibility Criteria
Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites224

Inclusion Criteria The main inclusion criteria include but are not limited to the following: * Is an individual of any sex/gender, ≥18 years of age * Has documentation of SARS-CoV-2 infection with sample collection ≤4 days prior to randomization * Has initial onset of signs/symptoms attributable t...

Countries:United StatesArgentinaBrazilBulgariaColombiaFinlandFranceGeorgiaGermanyItalyJapanMexicoNew ZealandPeruPhilippinesPolandPuerto RicoRomaniaSouth KoreaSpainTaiwanThailandUkraineUnited KingdomDominican RepublicEgyptGuatemalaHungaryKenyaMalaysiaRussiaSouth AfricaTurkey (Türkiye)CanadaChileIsraelSweden
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Recent Changes (Last 90 Days)
LOWJul 6, 2026NCT06667700lastUpdatePostDate: changed
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LOWJun 26, 2026NCT06667700lastUpdatePostDate: changed
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LOWMay 26, 2026NCT06667700primaryCompletionDate: changed
LOWMay 24, 2026NCT06667700studyFirstPostDate: changed