Pharmacotherapeutic group: Antivirals for systemic use, direct acting antivirals, ATC code: J05AB18
Mechanism of action
Molnupiravir is a prodrug that is metabolised to the cytidine nucleoside analogue, ribonucleoside analogue N4-hydroxycytidine (NHC) which distributes into cells where it is phosphorylated to form the pharmacologically active ribonucleoside triphosphate (NHC-TP). NHC-TP acts by a mechanism known as viral error catastrophe. NHC-TP incorporation into viral RNA by the viral RNA polymerase, results in an accumulation of errors in the viral genome leading to inhibition of replication.
Antiviral Activity
NHC was active in cell culture assays against SARS-CoV-2 (USA-WA1/2020 isolate) with 50% effective concentrations (EC50) ranging between 0.67 to 2.66 µM in A-549 cells and 0.32 to 2.03 µM in Vero E6 cells. NHC had similar antiviral activity against SARS-CoV-2 variants, including Alpha (B.1.1.7), Beta (B.1351), Gamma (P.1), Delta (B.1.617.2), Lambda (C.37), Mu (B 1.621) and Omicron (BA.1.1.529/BA.1, BA.1.1, BA.2, BA.4, BA.4.6, BA.5, BQ.1.1, HK.3, JN.1, XBB.1, XBB.1.5 and XBB.1.16) with mean EC50 values of 0.25-2.95 µM. No impact was observed on the in vitro antiviral activity of NHC against SARS-CoV-2 when NHC was tested in combination with abacavir, emtricitabine, hydroxychloroquine, lamivudine, nelfinavir, remdesivir, ribavirin, sofosbuvir, or tenofovir.
Pharmacodynamic effects
The relationship between NHC and intracellular NHC-TP with antiviral efficacy has not been evaluated clinically.
Resistance
No amino acid substitutions in SARS-CoV-2 associated with resistance to NHC have been identified in Phase 2 clinical trials evaluating molnupiravir for the treatment of COVID-19. In cell culture studies, the susceptibility of SARS-CoV-2 to inhibition by NHC did not substantially change as the NHC IC50 values showed <2-fold change over the 30 passages.
Clinical efficacy and safety
Clinical data are based on data from 1433 randomised subjects in the Phase 3 MOVe-OUT trial. MOVe-OUT was a randomised, placebo-controlled, double-blind clinical trial studying molnupiravir for the treatment of non-hospitalised patients with mild to moderate COVID-19 who were at risk for progressing to severe COVID-19 and/or hospitalisation. Eligible subjects were 18 years of age and older and had one or more pre-defined risk factors for disease progression: 60 years of age or older, diabetes, obesity (BMI >30), chronic kidney disease, serious heart conditions, chronic obstructive pulmonary disease, or active cancer. The study included symptomatic subjects not vaccinated against SARS-CoV-2 and who had laboratory confirmed SARS-CoV-2 infection and symptom onset within 5 days of enrolment. Subjects were randomised 1:1 to receive 800 mg of Lagevrio or placebo orally twice daily for 5 days.
At baseline, in all randomised subjects, the median age was 43 years (range: 18 to 90 years); 17% of subjects were 60 years of age or older and 3% were over 75 years of age; 49% of subjects were male; 57% were White, 5% Black or African American, 3% Asian; 50% were Hispanic or Latino. The majority of subjects were enrolled from sites in Latin America (46%) and Europe (33%); 12% were enrolled in Africa, 6% were enrolled in North America and 3% were enrolled in Asia.
Forty-eight percent of subjects received Lagevrio or placebo within 3 days of COVID-19 symptom onset. The most common risk factors were obesity (74%), 60 years of age or older (17%), and diabetes (16%). Among 792 subjects (55% of total randomised population) with available baseline SARS-CoV-2 variant/clade identification results, 58% were infected with Delta (B.1.617.2 and AY lineages), 20% were infected with Mu (B.1.621), 11% were infected with Gamma (P.1) and the remainder were infected with other variants/clades. Overall, baseline demographic and disease characteristics were well balanced between the treatment arms.
Table 2 provides the results of the primary endpoint (the percentage of subjects who were hospitalised or died through Day 29 due to any cause).
Table 2: Efficacy Results in Non-Hospitalised Adults with COVID-19
| Interim Analysis |
| | Lagevrio (N=385) n (%) | Placebo (N=377) n (%) | Risk difference* (95% CI) | p-value† |
| All-cause hospitalisation or death through Day 29† | 28 (7.3%) | 53 (14.1%) | -6.8% (-11.3%, -2.4%) | 0.0012 |
| Hospitalisation | 28 (7.3%) | 52 (13.8%) | | |
| Death | 0 (0%) | 8 (2.1%) | | |
| Unknown‡ | 0 (0%) | 1 (0.3%) | | |
| All-Randomised Analysis |
| | Lagevrio (N=709) n (%) | Placebo (N=699) n (%) | Risk difference* (95% CI) | |
| All-cause hospitalisation or death through Day 29 | 48 (6.8%) | 68 (9.7%) | -3.0% (-5.9%, -0.1%) | |
| Hospitalisation‡ | 48 (6.8%) | 67 (9.6%) | | |
| Death | 1 (0.1%) | 9 (1.3%) | | |
| Unknown§ | 0 (0%) | 1 (0.1%) | | |
| * Risk difference of molnupiravir-placebo based on Miettinen and Nurminen method stratified by time of COVID-19 symptom onset (≤3 days vs. >3 [4-5] days). † 1-sided p-Value ‡ Defined as ≥24 hours of acute care in a hospital or an acute care facility (e.g., emergency room). § Subjects with unknown status at Day 29 are counted as having an outcome of all-cause hospitalisation or death in the efficacy analysis. Note: All subjects who died through Day 29 were hospitalised prior to death. For interim analysis subjects: Relative risk reduction of molnupiravir compared to placebo is 48% (95% CI: 20%, 67%) based on the Cochran-Mantel-Haenszel method stratified by time of COVID-19 symptom onset (≤3 days vs. >3 [4-5] days). For all randomised subjects: Relative risk reduction of molnupiravir compared to placebo is 30% (95% CI: 1%, 51%) based on the Cochran-Mantel-Haenszel method stratified by time of COVID-19 symptom onset (≤3 days vs. >3 [4-5] days). |
Efficacy results were consistent across the majority of sub-groups (Figure 1).
Figure 1. Subgroup Efficacy Results in Non-Hospitalised Adults with COVID-19 - All-Randomised Subjects

The corresponding confidence interval is based on Miettinen & Nurminen method.
The modified intent-to-treat population is the efficacy analysis population.
Baseline serum samples were evaluated with the Roche Elecsys anti-N assay to test for the presence of antibodies (IgM, IgG and IgA) against the SARS-CoV-2 nucleocapsid protein.
The findings of these subgroup analyses are considered exploratory.
Paediatric population
The Agency has deferred the obligation to submit the results of studies with Lagevrio in one or more subsets of the paediatric population (see section 4.2 for information on paediatric use).
Viral RNA Rebound
Post-treatment increases in SARS-CoV-2 RNA shedding levels (i.e., viral RNA rebound) in nasopharyngeal samples were observed on Day 10, Day 15, and/or Day 29 in a subset of LAGEVRIO and placebo recipients in the Phase 3 MOVe-OUT trial. Approximately 1% of both LAGEVRIO and placebo recipients had evidence of recurrent COVID-19 symptoms coinciding with a rebound in viral RNA levels in nasopharyngeal samples.
Post-treatment viral RNA rebound was not associated with the primary clinical outcome of hospitalization or death through Day 29 following the single 5-day course of LAGEVRIO treatment. Post-treatment viral RNA rebound also was not associated with the detection of cell culture infectious virus in nasopharyngeal swab samples.
Exceptional circumstances
This medicinal product has been authorised under 'exceptional circumstances'.
This means that it has not been possible to obtain complete information on this medicinal product.
The Medicines and Healthcare product Regulatory Agency (MHRA) will review any new information which may become available every year and this SmPC will be updated as necessary.