Proportion of Patients in the United States Who Fill Their Nirmatrelvir/Ritonavir Prescriptions.

INTRODUCTION: Although real-world studies demonstrate that those prescribed nirmatrelvir/ritonavir (and particularly within 5 days of symptom onset) are less likely to experience severe COVID-19 outcomes, prior studies show that only a small fraction of patients with COVID-19 who are eligible for nirmatrelvir/ritonavir receive a prescription. Studies calculating the proportion of nirmatrelvir/ritonavir prescriptions filled and identifying individual- and pharmacy-level correlates of filling nirmatrelvir/ritonavir are lacking. METHODS: This retrospective cohort study included individuals aged ≥ 12 years with a nirmatrelvir/ritonavir prescription ordered at a large national retail pharmacy (December 22, 2021-August 12, 2023). Those taking contraindicated medications were excluded. For those with only one nirmatrelvir/ritonavir prescription ordered, the outcome was whether the prescription was filled (yes/no). In a subanalysis of these individuals, the outcome was whether the prescription was filled within 5 days of symptom onset (yes/no). For those with multiple prescriptions ordered, the outcome was whether > 1 (vs. 0 or 1) prescriptions were filled. A log-binomial regression with generalized estimating equations was used to identify individual (clinical and demographic) and pharmacy-level (percentage of trade area that is non-Hispanic white, urbanicity, US Census region, and tract-level area deprivation index) correlates. RESULTS: A total of 2,103,570 unique nirmatrelvir/ritonavir prescriptions were ordered for 1,985,990 individuals. Among the 95% of individuals prescribed only one nirmatrelvir/ritonavir course, 88% filled their prescription. Among those with > 1 prescription ordered, 77% (82,993/108,411) filled one and 13% (13,662/108,411) filled > 1. Patients ≥ 50 years of age and those with documented high-risk conditions were slightly more likely to fill prescriptions, regardless of whether one or multiple courses were ordered. Individuals with cancer, asthma, or taking corticosteroids or immunosuppressive medications were more likely to fill multiple prescriptions. CONCLUSIONS: Most patients filled their nirmatrelvir/ritonavir prescriptions. Interventions to improve uptake should focus on increasing patient and provider awareness, reducing nirmatrelvir/ritonavir prescribing disparities, and ensuring treatment initiation within 5 days.

Nirmatrelvir/Ritonavir (Paxlovid) Use Among Individuals at Risk of Severe COVID-19: An Analysis of the National COVID Cohort Collaborative (N3C).

PURPOSE: Paxlovid is effective in reducing COVID-19 hospitalization and mortality. This study characterized Paxlovid use and evaluated racial/ethnic disparities over time among community-dwelling adults at high risk of progression to severe COVID-19 disease. METHODS: This retrospective cohort study used the National COVID Cohort Collaborative (N3C) data and included individuals aged 18 years or older diagnosed with COVID-19 between January 2022 and December 2023. The study cohort included nonhospitalized individuals who were at high risk of COVID-19 progression, and selected the first COVID-19 episode in each quarter, including reinfection episodes. Paxlovid use was defined as receiving Paxlovid within ±5 days of a COVID-19 diagnosis. We used descriptive statistics to characterize Paxlovid use overall and by calendar quarter and race/ethnicity. We used a generalized estimating equations (GEE) models to quantify the association of race/ethnicity with Paxlovid use controlling for age, gender, and clinical characteristics. RESULTS: Among 1 264 215 individuals at high risk of disease progression (1 404 607 episodes), Paxlovid use increased from 1.2% in January-March 2022 to 35.1% in October-December 2023. Paxlovid use was more common among non-Hispanic White individuals (23.9%) than non-Hispanic Black (16.5%) and Latinx/e (16.7%) patients. After adjusting age, gender, and clinical characteristics, Paxlovid use was less likely among non-Hispanic Black (odds ratio [OR] 0.69, 95% confidence interval [CI] 0.68-0.70) and Latinx/e (OR 0.72, CI 0.71-0.73) patients than non-Hispanic White patients. CONCLUSIONS: Among a large, diverse cohort of community-dwelling individuals with COVID-19, nearly two out of three eligible individuals did not receive Paxlovid, and minoritized racial/ethnic groups were less likely to use Paxlovid than their non-Hispanic White individuals.

Nirmatrelvir/ritonavir: real world drug-drug interaction management experience.

BACKGROUND: In the UK, a regional vertical system for the delivery of COVID-19 medicines has been in place. This enabled centralization of expertise in risk stratification of patients, and in understanding and mitigating drug-drug interactions. RESEARCH DESIGN AND METHODS: We analyzed real-world drug-drug interactions in adult patients referred for nirmatrelvir/ritonavir therapy across one such geographic area covering 2.2 million London citizens. RESULTS: Among 208 who received NMV/r therapy, we identified 184 potential DDIs, 8% precluded nirmatrelvir/ritonavir use, 53% required management, but 56% of these did not have documented advice to hold therapy. CONCLUSIONS: This highlights the need to maintain and develop pathways for clinical pharmacology expertise in COVID-19 management.

Paxlovid reduces the 28-day mortality of patients with COVID-19: a retrospective cohort study.

PURPOSE: In this study, we aim to explore the efficacy of paxlovid on reducing mortality of COVID-19 patients in clinical setting, especially whether paxlovid modifies the risk of death in these severe and critical patients. METHODS: Our retrospective cohort study was conducted on the medical records of patients, consecutively admitted for COVID-19 to five hospitals in Chongqing, China from Dec 8, 2022 to Jan 20, 2023. Based on whether patients received paxlovid during their hospitalization, patients were grouped as paxlovid group and non-paxlovid group. We used 1:1 ratio propensity score matching (PSM) in our study to adjust for confounding factors and differences between groups. Statistical analysis were performed by SPSS 23.0. The differences in 28-day mortality between these two groups and its influencing factors were the main results we focused on. RESULTS: There were 1018 patients included in our study cohort. With 1:1 ratio PSM, each of the paxlovid group and non-paxlovid group included 237 patients. The results showed that patients using paxlovid have a lower 28-day mortality in overall population either before PSM (OR 0.594, 95% CI 0.385-0.917, p = 0.019) or after PSM (OR 0.458, 95% CI 0.272-0.774, p = 0.003) with multivariable adjusted logistic regression models. Meanwhile, in severe subgroup, it showed similar findings.With paxlovid treatment, it showed a significantly lower 28-day mortality in severe subgroup both before PSM (28% vs.41%, p = 0.008) and after PSM (19% vs.32%, p = 0.007). CONCLUSION: Paxlovid can significantly reduce the risk of 28-day mortality in overall population and severe subgroup patients.This study distinguished the severe subgroup patients with COVID-19 who benefit more from paxlovid treatment.

Efficacy and Safety of Azvudine in Patients With COVID-19 in China: A Meta-Analysis of Observational Studies.

BACKGROUND: Azvudine (FNC) is a novel small molecule antiviral drug for treating COVID-19 that is available only on the Chinese market. Despite being recommended for treating COVID-19 by the Chinese guidelines, its efficacy and safety are still unclear. This study aimed to evaluate the protective effect of FNC on COVID-19 outcomes and its safety. METHODS: We followed the PRISMA 2020 guidelines and searched the PubMed, Embase, Web of Science, Scopus, and China National Knowledge Infrastructure (CNKI) databases to evaluate studies on the effectiveness of FNC in treating COVID-19 in China, focusing on mortality and overall outcomes. Additionally, its impact on the length of hospital stay (LOHS), time to first nucleic acid negative conversion (T-FNANC), and adverse events was evaluated. The inclusion criterion was that the studies were published from July 2021 to April 10, 2024. This study uses the ROBINS-I tool to assess bias risk and employs the GRADE approach to evaluate the certainty of the evidence. RESULTS: The meta-analysis included 24 retrospective studies involving a total of 11 830 patients. Low-certainty evidence revealed no significant difference in mortality (OR = 0.91, 95% CI: 0.76-1.08) or LOHS (WMD = -0.24, 95% CI: -0.83 to 0.35) between FNC and Paxlovid in COVID-19 patients. Low-certainty evidence shows that the T-FNANC was longer (WMD = 1.95, 95% CI: 0.36-3.53). Compared with the Paxlovid group, low-certainty evidence shows the FNC group exhibited a worse composite outcome (OR = 0.77, 95% CI: 0.63-0.95) and fewer adverse events (OR = 0.63, 95% CI: 0.46-0.85). Compared with supportive treatment, low certainty shows FNC significantly reduced the mortality rate in COVID-19 patients (OR = 0.61, 95% CI: 0.51-0.74) and decreased the composite outcome (OR = 0.67, 95% CI: 0.50-0.91), and very low certainty evidence shows significantly decreased the T-FNANC (WMD = -4.62, 95% CI: -8.08 to -1.15). However, in very low certainty, there was no significant difference in LOHS (WMD = -0.70, 95% CI: -3.32 to 1.91) or adverse events (OR = 1.97, 95% CI: 0.48-8.17). CONCLUSIONS: FNC appears to be a safe and potentially effective treatment for COVID-19 in China, but further research with larger, high-quality studies is necessary to confirm these findings. Due to the certainty of the evidence and the specific context of the studies conducted in China, caution should be exercised when considering whether the results are applicable worldwide. TRIAL REGISTRATION: PROSPERO number: CRD42024520565.

Highly specific SARS-CoV-2 main protease (Mpro) mutations against the clinical antiviral ensitrelvir selected in a safe, VSV-based system.

In the SARS-CoV-2 pandemic, the so far two most effective approved antivirals are the protease inhibitors nirmatrelvir, in combination with ritonavir (Paxlovid) and ensitrelvir (Xocova). However, antivirals and indeed all antimicrobial drugs are sooner or later challenged by resistance mutations. Studying such mutations is essential for treatment decisions and pandemic preparedness. At the same time, generating resistant viruses to assess mutants is controversial, especially with pathogens of pandemic potential like SARS-CoV-2. To circumvent gain-of-function research with non-attenuated SARS-CoV-2, a previously developed safe system based on a chimeric vesicular stomatitis virus dependent on the SARS-CoV-2 main protease (VSV-Mpro) was used to select mutations against ensitrelvir. Ensitrelvir is clinically especially relevant due to its single-substance formulation, avoiding drug-drug interactions by the co-formulated CYP3A4 inhibitor ritonavir in Paxlovid. By treating VSV-Mpro with ensitrelvir, several highly-specific resistant mutants against this inhibitor were selected, while being still fully or largely susceptible to nirmatrelvir. We then confirmed several ensitrelvir-specific mutants in gold standard enzymatic assays and SARS-CoV-2 replicons. These findings indicate that the two inhibitors can have distinct viral resistance profiles, which could determine treatment decisions.

Low Prevalence of Nirmatrelvir-Ritonavir Resistance-Associated Mutations in SARS-CoV-2 Lineages From Botswana.

Background: We evaluated naturally occurring nirmatrelvir-ritonavir (NTV/r) resistance-associated mutations (RAMs) among severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains from Botswana, a country with no NTV/r use to date, in order to recommend the usage of the agent for high-risk patients with coronavirus disease 2019 (COVID-19). Methods: We conducted a retrospective analysis using 5254 complete SARS-CoV-2 sequences from Botswana (September 2020-September 2023). We evaluated the mutational landscape of SARS-CoV-2 3-Chymotrypsin-like protease (3CLpro) relative to the highlighted list of RAMs granted Food and Drug Administration Emergency Use Authorization in 2023. Results: The sequenced 5254 samples included Beta variants of concerns (VOCs; n = 323), Delta VOCs (n = 1314), and Omicron VOCs (n = 3354). Overall, 77.8% of the sequences exhibited at least 1 polymorphism within 76/306 amino acid positions in the nsp5 gene. NTV/rRAMs were identified in 34/5254 (0.65%; 95% CI, 0.43%-0.87%) and occurred at 5 distinct positions. Among the NTV/r RAMS detected, A191V was the most prevalent (24/34; 70.6%). Notably, T21I mutation had a prevalence of 20.6% (7/34) and coexisted with either K90R (n = 3) polymorphism in Beta sequences with RAMs or P132H (n = 3) polymorphism for Omicron sequences with RAMs. Other NTV/r RAMs detected included P108S, with a prevalence of 5.88% (2/34), and L50F, with a prevalence of 2.94% (1/34). NTV/r RAMs were significantly higher (P < .001) in Delta (24/35) compared with Beta (4/34) and Omicron (6/34) sequences. Conclusions: The frequency of NTV/r RAMs in Botswana was low. Higher rates were observed in Delta VOCs compared to Omicron and Beta VOCs. As NTV/r use expands globally, continuous surveillance for drug-resistant variants is essential, given the RAMs identified in our study.

Nirmatrelvir/Ritonavir Regimen for Mild/Moderately Severe COVID-19: A Rapid Review With Meta-Analysis and Trial Sequential Analysis.

BACKGROUND: The efficacy, effectiveness, and safety of the approved nirmatrelvir/ritonavir regimen for treatment of laboratory-confirmed mild/moderately severe COVID-19 remains unclear. METHODS: We systematically identified randomized controlled trials (RCTs) and real-world studies (RWS; observational studies) of the efficacy/effectiveness and/or safety of the approved nirmatrelvir/ritonavir regimen for COVID-19. We pooled appropriate data (adjusted estimates for RWS) using an inverse variance, random-effects model. We calculated statistical heterogeneity using the I 2 statistic. Results are presented as relative risk (RR) with associated 95% CI. We further assessed risk of bias/study quality and conducted trial sequential analysis of the evidence from RCTs. RESULTS: We included 4 RCTs (4,070 persons) and 16 RWS (1,925,047 persons) of adults (aged ≥18 years). One and 3 RCTs were of low and unclear risk of bias, respectively. The RWS were of good quality. Nirmatrelvir/ritonavir significantly decreased COVID-19 hospitalization compared with placebo/no treatment (RR = 0.17; 95% CI, 0.10-0.31; I 2 = 77.2%; 2 RCTs, 3,542 persons), but there was no significant difference for decrease of worsening severity (RR = 0.82; 95% CI, 0.66-1.01; I 2 = 47.5%; 3 RCTs, 1,824 persons), viral clearance (RR = 1.19; 95% CI, 0.93-1.51; I 2 = 82%; 2 RCTs, 528 persons), adverse events (RR = 1.41; 95% CI, 0.92-2.14; I 2 = 70.6%; 4 RCTs, 4,070 persons), serious adverse events (RR = 0.82; 95% CI, 0.41-1.62; I 2 = 0%; 3 RCTs, 3,806 persons), and all-cause mortality (RR = 0.27; 95% CI, 0.04-1.70; I 2 = 49.9%; 3 RCTs, 3,806 persons), although trial sequential analysis suggested that the current total sample sizes for these outcomes were not large enough for conclusions to be drawn. Real-world studies also showed significantly decreased COVID-19 hospitalization (RR = 0.48; 95% CI, 0.37-0.60; I 2 = 95.0%; 11 RWS, 1,421,398 persons) and all-cause mortality (RR = 0.24; 95% CI, 0.14-0.34; I 2 = 65%; 7 RWS, 286,131 persons) for nirmatrelvir/ritonavir compared with no treatment. CONCLUSIONS: Nirmatrelvir/ritonavir appears to be promising for preventing hospitalization and potentially decreasing all-cause mortality for persons with mild/moderately severe COVID-19, but the evidence is weak. More studies are needed.

Safety and Efficacy of Paxlovid in Pediatric Intensive Care Unit Patients with COVID-19.

INTRODUCTION: Paxlovid (nirmatrelvir/ritonavir) has received endorsement from several guidelines for treating COVID-19 in adults, but its use in children is still uncertain. OBJECTIVES: This study aimed to evaluate the safety and effectiveness of paxlovid in pediatric patients in the pediatric intensive care unit (PICU). METHODS: A retrospective analysis was performed on children with COVID-19. The children who received paxlovid comprised the paxlovid group; otherwise, they were referred to as the control group. RESULTS: A total of 31 children were enrolled, with 12 and 19 participants assigned to the paxlovid and control groups, respectively. Approximately 35% had received vaccination against the novel coronavirus. The control group exhibited a significantly lower mean age in comparison to the paxlovid group (p < 0.001). However, no significant differences were observed between the groups in terms of other baseline data and biochemical indexes at admission. However, on the fifth day of drug administration, the paxlovid group exhibited a statistically significant decrease in temperature compared to the control group (p < 0.05). Additionally, the paxlovid group exhibited a significantly shorter conversion time to negativity for novel coronary genes in the respiratory tract (9.5 days) compared to the control group (16 days, p < 0.05). The administration of paxlovid did not result in any observed adverse reactions. Merely two patients exhibited a transient elevation in liver enzyme levels. CONCLUSION: The application of paxlovid in critically ill pediatric patients with COVID-19 can effectively control symptoms and promote virus clearance, demonstrating efficacy and a relatively low-risk profile.

Telemedicine for Prescribing Nirmatrelvir/Ritonavir: Safety, Logistics, and Challenges.

Nirmatrelvir/ritonavir can be a useful COVID-19 treatment but is challenging to prescribe safely because of drug-drug interactions. This study describes our experience prescribing nirmatrelvir/ritonavir within a small interdisciplinary team with a specific focus on management of drug-drug interactions. Ascertaining and communicating modifications of concomitant medications is a key safety element.

Identifying Veterans Who Benefit From Nirmatrelvir-Ritonavir: A Target Trial Emulation.

BACKGROUND: Nirmatrelvir-ritonavir is recommended for persons at risk for severe coronavirus disease 2019 (COVID-19) but remains underutilized. Information on which eligible groups are likely to benefit from treatment is needed. METHODS: We conducted a target trial emulation study in the Veterans Health Administration comparing nirmatrelvir-ritonavir treated versus matched untreated veterans at risk for severe COVID-19 who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from April 2022 through March 2023. We measured incidence of any hospitalization or all-cause mortality at 30 days. Outcomes were measured for the entire cohort, as well as among subgroups defined by 30-day risk of death or hospitalization, estimated using an ensemble risk prediction model. RESULTS: Participants were 87% male with median age 66 years and 16% unvaccinated. Compared with matched untreated participants, those treated with nirmatrelvir-ritonavir (n = 24 205) had a lower 30-day risk for hospitalization (1.80% vs 2.30%; risk difference [RD], -0.50% points [95% confidence interval {CI}: -.69 to -.35]) and death (0.11% vs 0.30%; RD, -0.20 [95% CI: -.24 to -.13]). The greatest reductions in combined hospitalization or death were observed in the highest risk quartile (RD -2.85 [95% CI: -3.94 to -1.76]), immunocompromised persons (RD -1.91 [95% CI: -3.09 to -.74]), and persons aged ≥75 years (RD -1.16 [95% CI: -1.73 to -.59]). No reductions were observed in the 2 lowest risk quartiles or persons younger than 65 years. CONCLUSIONS: Nirmatrelvir-ritonavir was effective in reducing 30-day hospitalization and death in older veterans, those at highest predicted risk for severe outcomes, and immunocompromised groups. Benefit was not observed in younger veterans or groups at lower predicted risk for hospitalization and death.

Azvudine versus Paxlovid in COVID-19: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to compare the effectiveness and safety of azvudine versus nirmatrelvir/ritonavir (Paxlovid) in treating coronavirus disease 2019 (COVID-19). The researchers conducted searches on PubMed, Cochrane Library, Web of Science, medRxiv, and Google Scholar until January 2024. The Cochrane risk of bias tool was utilised to evaluate the quality of the included studies, and data analysis was performed using Comprehensive Meta-Analysis software. Thirteen studies, including 4949 patients, were analysed. The meta-analysis results showed no significant difference between the azvudine and Paxlovid groups in terms of mortality rate (odds rate [OR] = 0.84, 95% confidence interval [CI]: 0.59-1.21), negative polymerase chain reaction (PCR) conversion time (standard mean difference [SMD] = 1.52, 95% CI: -1.07-4.11), and hospital stay (SMD = -0.39, 95% CI: -1.12-0.33). However, a significant difference was observed between the two groups in terms of intensive care unit admission (OR = 0.42, 95% CI: 0.23-0.75) and the need for mechanical ventilation (OR = 0.61, 95% CI: 0.44-0.86) in favour of azvudine. The incidence of adverse events in the azvudine group was significantly lower (OR = 0.66, 95% CI: 0.43-0.99). The certainty of evidence was rated as low and moderate. Azvudine and Paxlovid demonstrated similar effectiveness in reducing mortality rates, negative PCR conversion time and hospital stay. However, azvudine showed better effectiveness in improving other outcomes. Regarding the level of certainty of evidence, further research is needed to validate or challenge these results.

Real-world effectiveness of molnupiravir, azvudine and paxlovid against mortality and viral clearance among hospitalized patients with COVID-19 infection during the omicron wave in China: A retrospective cohort study.

OBJECTIVES: In this retrospective cohort study, we aimed to assess clinical effectiveness and viral clearance following the use of molnupiravir, azvudine and paxlovid in hospitalized patients with COVID-19 in China dominated by the omicron BA.5.2 and BF.7 subvariant of SARS-CoV-2. METHODS: Enrolled patients were assigned to the molnupiravir group or the azvudine group or the paxlovid group or the control group (not taking any antiviral drugs). The primary outcome of the cohort study was viral clearance and viral burden rebound after treatment and the secondary outcome was 28-day all-cause mortality. The four groups were propensity score-matched (1:1). We plotted viral load trends for each antiviral drug intervention using locally weighted regression (LOWESS) smoothed data. Multivariate logistic regression (stepwise algorithm) models were used to determine any risk factors for 28-day mortality. RESULTS: Of the 1537 patients receiving any treatment, 886 (57.6 %) received molnupiravir, 390 (25.4 %) received azvudine, 94 (6.1 %) received paxlovid, and 167 (10.9 %) did not use any antiviral drugs. Our data analysis showed that age (OR = 1.05, 95 % CI: 1.03-1.07, P < 0.001), Charlson comorbidty index (OR = 1.32, 95 % CI: 1.18-1.48, P < 0.001), severity of COVID-19 (P < 0.001), gamma globulin (OR = 2.04, 95 % CI: 1.03-3.99, P = 0.039) and corticosteroids use (OR = 2.3, 95 % CI: 1.19-4.69, P = 0.017) were independent prognostic factors for 28-day mortality in COVID-19 patients. After propensity score matching (PSM), the paxlovid recipients (OR = 0.22, 95 % CI: 0.05-0.83, P = 0.036) or azvudine recipients (OR = 0.27, 95 % CI: 0.07-0.91, P = 0.046) had lower 28-day mortality compared to their matched controls. Viral rebound occurred in the control group around days 9-16, while no viral rebound was found in any of the three oral antiviral groups. We found that molnupiravir group performed comparably in terms of the rate of nucleic acid conversion negative compared with the paxlovid group, while azvudine group performed slightly worse compared with the paxlovid group or molnupiravir group. CONCLUSIONS: In our retrospective cohort of hospitalized patients with COVID-19 during the wave of omicron strain, the molnupiravir, paxlovid and azvudine recipients showed a faster and more stable decrease in viral load and rare virus rebound in response to antiviral treatments when compared to the controls. The study supported that initiation treatment with paxlovid and azvudine was associated with significantly lower risk of all-cause death within 28 days.

Supratherapeutic INR During Treatment With Nirmatrelvir/Ritonavir and Warfarin and Acute Illness With COVID-19: A Case Report.

Background: Several studies have examined INR fluctuations using pharmacokinetic (PK) models or post-hoc INR values after completing nirmatrelvir/ritonavir, but further study of the effects of the drug interaction with warfarin during treatment is necessary. Case Summary: Nirmatrelvir/ritonavir is largely utilized in the outpatient setting so data regarding INR trends in hospitalized patients on warfarin is limited. However, many who receive nirmatrelvir/ritonavir outpatient experience difficulty with presenting to clinic for INR checks due to feeling acutely ill along with isolation precautions. We present the case of a patient receiving warfarin and utilizing home INR testing for monitoring. After diagnosis of coronavirus disease of 2019 (COVID-19), she was started on nirmatrelvir/ritonavir on day five after testing positive. Most recent INR prior to the start of therapy was 2.7 and had been stable on the same dose for months prior to infection. On day two of nirmatrelvir/ritonavir, her INR rose to 4.0 on home point of care INR testing. Despite reducing her dose of warfarin by 15%, her INR remained supratherapeutic the day after completing nirmatrelvir/ritonavir (4.0) and for several checks after. One month after completion of therapy, her INR returned to therapeutic levels. Practice Implications: While PK models and case series have hypothesized both potential increases or decreases in INR with the nirmatrelvir/ritonavir and warfarin interaction, COVID-19 infection itself can cause several pharmacodynamic changes which can increase INR, including decreased appetite and, in severe cases, organ dysfunction. This case provides real-world insight into the drug interaction between nirmatrelvir/ritonavir and the drug-disease state interaction between warfarin and COVID-19.

A retrospective cohort study of Paxlovid efficacy depending on treatment time in hospitalized COVID-19 patients.

Paxlovid, a SARS-CoV-2 antiviral, not only prevents severe illness but also curtails viral shedding, lowering transmission risks from treated patients. By fitting a mathematical model of within-host Omicron viral dynamics to electronic health records data from 208 hospitalized patients in Hong Kong, we estimate that Paxlovid can inhibit over 90% of viral replication. However, its effectiveness critically depends on the timing of treatment. If treatment is initiated three days after symptoms first appear, we estimate a 17% chance of a post-treatment viral rebound and a 12% (95% CI: 0-16%) reduction in overall infectiousness for non-rebound cases. Earlier treatment significantly elevates the risk of rebound without further reducing infectiousness, whereas starting beyond five days reduces its efficacy in curbing peak viral shedding. Among the 104 patients who received Paxlovid, 62% began treatment within an optimal three-to-five-day day window after symptoms appeared. Our findings indicate that broader global access to Paxlovid, coupled with appropriately timed treatment, can mitigate the severity and transmission of SARS-Cov-2.

Erythema Multiforme in an HIV+ Patient on Highly Active Antiretroviral Therapy After Starting Paxlovid (Nirmatrelvir-Ritonivir).

In this report, we present a case of a woman currently on HIV antiretroviral therapy who presented with oral mucosal and cutaneous skin lesions with a target-like appearance following completion of a five-day course of Paxlovid™ for symptomatic COVID-19 infection. The patient was treated with intravenous steroids and oral antihistamines with mild improvement. However, she returned in one week with worsening skin lesions. The biopsy and infectious workup were non-contributory. It was determined that the patient had developed erythema multiforme (EM), secondary to Paxlovid™.

Reduced Viral Shedding Time in High-Risk COVID-19 Patients Infected by Omicron and Treated with Paxlovid: A Real-World Study from China.

Introduction: The purpose of this study was to compare the viral shedding time in patients infected with the Omicron variant during Paxlovid therapy and conventional therapy and to analyze the effects of Paxlovid on patients infected with COVID-19. Methods: In this study, the demographic and clinical characteristics and laboratory data of 3159 patients infected with the SARS-CoV-2 Omicron variant treated at Jilin Province People's Hospital were collected and analyzed. A total of 362 patients received Paxlovid therapy, and 2797 patients received conventional therapy. After propensity score matching (PSM), 1086 patients were obtained. Results: The difference in platelet (PLT) count between the two groups was statistically significant but within the normal range (P < 0.05). CT value revealed that the nucleic acid test results became negative more quickly in the Paxlovid therapy group. Analysis of the Paxlovid therapy group showed that IgG and IgM levels were increased after Paxlovid therapy administration. Conclusion: The CT value of the Paxlovid therapy group became negative more quickly. This finding suggests that Paxlovid treatment after early diagnosis of the Omicron variant may achieve good therapeutic efficacy.

The effect of molnupiravir and nirmatrelvir on SARS-CoV-2 genome diversity in severe models of COVID-19.

Objectives: Immunocompromised individuals are susceptible to severe COVID-19 and potentially contribute to the emergence of variants with altered pathogenicity due to persistent infection. This study investigated the impact of immunosuppression on SARS-CoV-2 infection in k18-hACE2 mice and the effectiveness of antiviral treatments in this context during the first 7 days of infection. Methods: Mice were immunosuppressed using cyclophosphamide and infected with a B lineage of SARS-CoV-2. Molnupiravir and nirmatrelvir, alone and in combination, were administered and viral load and viral sequence diversity was assessed. Results: Treatment of infected but immune compromised mice with both compounds either singly or in combination resulted in decreased viral loads and pathological changes compared to untreated animals. Treatment also abrogated infection of neuronal tissue. However, no consistent changes in the viral consensus sequence were observed, except for the emergence of the S:H655Y mutation. Molnupiravir, but not nirmatrelvir or immunosuppression alone, increased the transition/transversion (Ts/Tv) ratio, representative of A>G and C>U mutations and this increase was not altered by the co-administration of nirmatrelvir with molnupiravir.Notably, immunosuppression itself did not appear to promote the emergence of mutational characteristic of variants of concern (VOCs). Conclusions: Further investigations are warranted to fully understand the role of immunocompromised individuals in VOC development, especially by taking persistence into consideration, and to inform optimised public health strategies. It is more likely that immunodeficiency promotes viral persistence but does not necessarily lead to substantial consensus-level changes in the absence of antiviral selection pressure. Consistent with mechanisms of action, molnupiravir showed a stronger mutagenic effect than nirmatrelvir in this model.

Discovery and development of COVID-19 vaccines and therapeutics: nonclinical perspectives.

The development and regulatory review of BNT162b2, a COVID-19 vaccine, and PaxlovidTM (nirmatrelvir tablets/ritonavir tablets), a COVID-19 therapeutic, are benchmarks for accelerated innovation during a global pandemic. Rapid choice of the SARS-CoV-2 spike protein and main protease (Mpro) as targets for the vaccine and therapeutic, respectively, leveraged the available knowledge of the biology of SARS-CoV-2 and related viruses. The nonclinical immunogenicity and safety of BNT162b2 was rigorously assessed. Likewise, a comprehensive nonclinical safety assessment was conducted for the therapeutic candidates, lufotrelvir (PF-07304814) and nirmatrelvir (PF-07321332). The development and regulatory review of BNT162b2 and Paxlovid was enabled through close collaboration of the pharmaceutical industry with regulatory agencies and public health organizations. This experience highlights approaches that could be adopted for pandemic preparedness including risk-based investment strategies, conduct of activities in parallel that normally are conducted sequentially, quick kill decisions, simultaneous evaluation of multiple candidates, and use of flexible, established vaccine platforms.