Nirmatrelvir combined with ritonavir for preventing and treating COVID-19

Oral nirmatrelvir/ritonavir (Paxlovid®) aims to avoid severe COVID-19 in asymptomatic people or those with mild symptoms, thereby decreasing hospitalization and death. Due to its novelty, there are currently few published study results. It remains to be evaluated for which indications and patient populations the drug is suitable.  OBJECTIVES: To assess the efficacy and safety of nirmatrelvir/ritonavir (Paxlovid®) plus standard of care compared to standard of care with or without placebo, or any other intervention for treating COVID-19 and for preventing SARS-CoV-2 infection. To explore equity aspects in subgroup analyses. To keep up to date with the evolving evidence base using a living systematic review (LSR) approach and make new relevant studies available to readers in-between publication of review updates.

We searched the Cochrane COVID-19 Study Register, Scopus, and WHO COVID-19 Global literature on coronavirus disease database, identifying completed and ongoing studies without language restrictions and incorporating studies up to 11 July 2022.  This is a LSR. We conduct monthly update searches that are being made publicly available on the open science framework (OSF) platform.

Studies were eligible if they were randomized controlled trials (RCTs) comparing nirmatrelvir/ritonavir plus standard of care with standard of care with or without placebo, or any other intervention for treatment of people with confirmed COVID-19 diagnosis, irrespective of disease severity or treatment setting, and for prevention of SARS-CoV-2 infection. We screened all studies for research integrity. Studies were ineligible if they had been retracted, or if they were not prospectively registered including appropriate ethics approval.

We followed standard Cochrane methodology and used the Cochrane risk of bias 2 tool. We rated the certainty of evidence using the GRADE approach for the following outcomes: 1. to treat outpatients with mild COVID-19; 2. to treat inpatients with moderate-to-severe COVID-19: mortality, clinical worsening or improvement, quality of life, (serious) adverse events, and viral clearance; 3. to prevent SARS-CoV-2 infection in post-exposure prophylaxis (PEP); and 4. pre-exposure prophylaxis (PrEP) scenarios: SARS-CoV-2 infection, development of COVID-19 symptoms, mortality, admission to hospital, quality of life, and (serious) adverse events. We explored inequity by subgroup analysis for elderly people, socially-disadvantaged people with comorbidities, populations from LICs and LMICs, and people from different ethnic and racial backgrounds.

As of 11 July 2022, we included one RCT with 2246 participants in outpatient settings with mild symptomatic COVID-19 comparing nirmatrelvir/ritonavir plus standard of care with standard of care plus placebo. Trial participants were unvaccinated, without previous confirmed SARS-CoV-2 infection, had a symptom onset of no more than five days before randomization, and were at high risk for progression to severe disease. Prohibited prior or concomitant therapies included medications highly dependent on CYP3A4 for clearance and CYP3A4 inducers.  We identified eight ongoing studies. Nirmatrelvir/ritonavir for treating COVID-19 in outpatient settings with asymptomatic or mild disease For the specific population of unvaccinated, high-risk patients nirmatrelvir/ritonavir plus standard of care compared to standard of care plus placebo may reduce all-cause mortality at 28 days (risk ratio (RR) 0.04, 95% confidence interval (CI) 0.00 to 0.68; 1 study, 2224 participants; estimated absolute effect: 11 deaths per 1000 people receiving placebo compared to 0 deaths per 1000 people receiving nirmatrelvir/ritonavir; low-certainty evidence, and admission to hospital or death within 28 days (RR 0.13, 95% CI 0.07 to 0.27; 1 study, 2224 participants; estimated absolute effect: 61 admissions or deaths per 1000 people receiving placebo compared to eight admissions or deaths per 1000 people receiving nirmatrelvir/ritonavir; low-certainty evidence). Nirmatrelvir/ritonavir plus standard of care may reduce serious adverse events during the study period compared to standard of care plus placebo (RR 0.24, 95% CI 0.15 to 0.41; 1 study, 2224 participants; low-certainty evidence). Nirmatrelvir/ritonavir plus standard of care probably has little or no effect on treatment-emergent adverse events (RR 0.95, 95% CI 0.82 to 1.10; 1 study, 2224 participants; moderate-certainty evidence), and probably increases treatment-related adverse events such as dysgeusia and diarrhoea during the study period compared to standard of care plus placebo (RR 2.06, 95% CI 1.44 to 2.95; 1 study, 2224 participants; moderate-certainty evidence). Nirmatrelvir/ritonavir plus standard of care probably decreases discontinuation of study drug due to adverse events compared to standard of care plus placebo (RR 0.49, 95% CI 0.30 to 0.80; 1 study, 2224 participants; moderate-certainty evidence). No study results were identified for improvement of clinical status, quality of life, and viral clearance.  Subgroup analyses for equity Most study participants were younger than 65 years (87.1% of the : modified intention to treat (mITT1) population with 2085 participants), of white ethnicity (71.5%), and were from UMICs or HICs (92.1% of study centres). Data on comorbidities were insufficient.  The outcome 'admission to hospital or death' was investigated for equity: age (< 65 years versus ≥ 65 years) and ethnicity (Asian versus Black versus White versus others). There was no difference between subgroups of age. The effects favoured treatment with nirmatrelvir/ritonavir for the White ethnic group. Estimated effects in the other ethnic groups included the line of no effect (RR = 1). No subgroups were reported for comorbidity status and World Bank country classification by income level. No subgroups were reported for other outcomes. Nirmatrelvir/ritonavir for treating COVID-19 in inpatient settings with moderate to severe disease No studies available. Nirmatrelvir/ritonavir for preventing SARS-CoV-2 infection (PrEP and PEP) No studies available.

There is low-certainty evidence that nirmatrelvir/ritonavir reduces the risk of all-cause mortality and hospital admission or death based on one trial investigating unvaccinated COVID-19 participants without previous infection that were at high risk and with symptom onset of no more than five days. There is low- to moderate-certainty evidence that nirmatrelvir/ritonavir is safe in people without prior or concomitant therapies including medications highly dependent on CYP3A4. Regarding equity aspects, except for ethnicity, no differences in effect size and direction were identified. No evidence is available on nirmatrelvir/ritonavir to treat hospitalized people with COVID-19 and to prevent a SARS-CoV-2 infection. We will continually update our search and make search results available on OSF.