Cost-Utility Model of Nirmatrelvir/Ritonavir in Brazil: Analysis of a Vaccinated Population

OBJECTIVES

The aim of this study is to conduct a cost-utility analysis of the use of the antiviral nirmatrelvir/ritonavir, applied to a vaccinated Brazilian population against COVID-19, from the perspective of the Brazilian Public Health System (SUS).

METHODS

A microsimulation model was created with individual-level data and daily cycles, with a 1-year time horizon, to compare the current scenario of standard care with a scenario in which nirmatrelvir/ritonavir is offered to the population. Adults of any age group that received ≥2 doses of the COVID-19 vaccine formed the investigated population. Direct medical costs of the outpatients and inpatients admitted to the ward or intensive care unit were included. The effectiveness of the model was measured in quality-adjusted life-years (QALYs).

RESULTS

In all simulations, the use of nirmatrelvir/ritonavir resulted in incremental costs per patient of US dollar (USD)245.86 and incremental effectiveness of 0.009 QALY, over a year. The incremental cost-utility ratio was USD27 220.70/QALY. The relative risk of the vaccinated population was the factor that affected the outcome most, according to the univariate sensitivity analysis. The probabilistic sensitivity analysis resulted in 100% of the simulations being more costly and effective, but that only 4% of them were below the established cost-effectiveness threshold of USD24 000.00/QALY. In the scenario considering only the population over 60 years old and immunosuppressed (of any age), the incremental cost-utility ratio was USD7589.37/QALY.

CONCLUSIONS

The use of nirmatrelvir/ritonavir in the treatment of COVID-19 in a vaccinated population was cost-effective only for immunosuppressed individuals and people over 60 years of age.

Development of a novel quality by design-enabled stability-indicating HPLC method and its validation for the quantification of nirmatrelvir in bulk and pharmaceutical dosage forms

A systematic and novel quality by design-enabled, rapid, simple, and economic stability-indicating HPLC method for quantifying nirmatrelvir (NMT) was successfully developed and validated. An analytical target profile (ATP) was established, and critical analytical attributes (CAAs) were allocated to meet the ATP requirements. The method used chromatographic separation using a Purosphere column with a 4.6 mm inner diameter × 250 mm (2.5 μm). The analysis occurred at 50°C with a flow rate of 1.2 mL/min and detection at 220 nm. A 10 μL sample was injected, and the mobile phase consisted of two components: mobile phase A, containing 0.1% formic acid in water (20%), and mobile phase B, containing 0.1% formic acid in acetonitrile (80%). The diluent was prepared by mixing acetonitrile and water at a 90:10 v/v ratio. The retention time for the analyte was determined to be 2.78 min. Accuracy exceeded 99%, and the correlation coefficient was greater than 0.999. The validated HPLC method was characterized as precise, accurate, and robust. Significantly, NMT was found to be susceptible to alkaline, acidic, and peroxide conditions during forced degradation testing. The stability-indicating method developed effectively separated the degradation products formed during stress testing, underlining its effectiveness in stability testing and offering accuracy, reliability, and sensitivity in determining NMT.

In vivo and in vitro metabolite profiling of nirmatrelvir using LC-Q-ToF-MS/MS along with the in silico approaches for prediction of metabolites and their toxicity

Nirmatrelvir (NRV), a 3C-like protease or Mpro inhibitor of SARS-CoV-2, is used for the treatment of COVID-19 in adult and paediatric patients. The present study was accomplished to investigate the comprehensive metabolic fate of NRV using in vitro and in vivo models. The in vitro models used for the study were microsomes (human liver microsomes, rat liver microsomes, mouse liver microsomes) and S9 fractions (human liver S9 fractions and rat liver S9 fractions) with the appropriate cofactors, whereas Sprague-Dawley rats were used as the in vivo models. Nirmatrelvir was administered orally to Sprague-Dawley rats, which was followed by the collection of urine, faeces and blood at pre-determined time intervals. Protein precipitation was used as the sample preparation method for all the samples. The samples were then analysed by liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-Q-ToF-MS/MS) using an Acquity BEH C18 column with 0.1% formic acid and acetonitrile as the mobile phase. Four metabolites were found to be novel, which were formed via amide hydrolysis, oxidation and hydroxylation. Furthermore, an in silico analysis was performed using Meteor Nexus software to predict the probable metabolic changes of NRV. The toxicity and mutagenicity of NRV and its metabolites were also determined using DEREK Nexus and SARAH Nexus.

Nirmatrelvir Resistance-de Novo E166V/L50V Mutations in an Immunocompromised Patient Treated With Prolonged Nirmatrelvir/Ritonavir Monotherapy Leading to Clinical and Virological Treatment Failure-a Case Report

Resistance of SARS-CoV-2 to antivirals was shown to develop in immunocompromised individuals receiving remdesivir. We describe an immunocompromised patient who was treated with repeated and prolonged courses of nirmatrelvir and developed de-novo E166V/L50F mutations in the Mpro region. These mutations were associated with clinical and virological treatment failure.

Population pharmacokinetics and pharmacodynamics of nirmatrelvir in Chinese patients with COVID-19

BACKGROUND

The pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of nirmatrelvir (NMV) are unknown in Chinese patients with COVID-19.

OBJECTIVES

To understand the PK, as well as PK-PD characteristics of NMV for optimizing the dose in Chinese patients with COVID-19.

METHODS

We enrolled 141 participants who received NMV 300 mg/ritonavir (RTV) 100 mg b.i.d. for 5 days. The NMV concentrations were analyzed using 251 blood samples. PK/PD of NMV was investigated in these COVID-19 patients using a nonlinear mixed-effects model.

RESULTS

The patients had a mean age of 82 years (range, 34-97). The absorption rate constant and apparent clearance of NMV in this Chinese cohort were 0.253 h-1 and 6.83 L/h, respectively, similar to Caucasian patients. No covariates affected NMV clearance. Predicted peak (Cmax ) and trough concentration (Cmin ) under 300 mg NMV/100 mg RTV b.i.d. were 4004 and 1498 ng/mL, respectively. Although higher AUC and Cmin were weakly associated with a slight increase in the number of cycle threshold (CT) of viral genes, no significant correlation was found, indicating a weak relationship between drug exposure and efficacy (CT).

CONCLUSIONS

In all, our findings suggest no ethnic PK differences, a weak and clinically insignificant relationship between drug exposure and efficacy, suitable dosage for Chinese patients (including the elderly) based on PK parameters, and the need for further studies to determine optimal regimens for high-risk patients due to inter-individual variability.

Simnotrelvir as a potential treatment for COVID-19

INTRODUCTION

Simnotrelvir is a selective 3-chymotrypsin-like oral protease inhibitor with activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

AREAS COVERED

On 18 January 2024, results of a double-blind, randomized, placebo-controlled trial of simnotrelvir as a treatment for mild-to moderate COVID-19-were published, indicating the drug, when given in combination with ritonavir, shortened the time to resolution of symptoms.

EXPERT OPINION

Treatment options for most outpatients with mild-to-moderate COVID-19 are limited. The protease inhibitor nirmatrelvir in combination with ritonavir has proven effective in patients who are high risk for progression to severe COVID-19, but there are no approved therapies for standard-risk patients, who now comprise the majority of the population. Simnotrelvir appears to be effective in standard-risk patients, including those who have completed primary vaccination against COVID-19 and have received a booster dose. This manuscript examines the rationale for the development of simnotrelvir and explores how this drug may be used in the future to treat COVID-19.

Effect of Hepatic Impairment on the Pharmacokinetics of Nirmatrelvir/Ritonavir, the First Oral Protease Inhibitor for the Treatment of COVID-19

Nirmatrelvir, a novel, potent, orally bioavailable severe acute respiratory syndrome coronavirus 2 main protease inhibitor, coadministered with ritonavir for pharmacokinetic (PK) enhancement is licensed for the treatment of mild to moderate COVID-19 in individuals at increased risk of progression to severe disease. Cytochrome P450 3A4 is the primary metabolic enzyme responsible for nirmatrelvir metabolism; however, when cytochrome P450 3A4 is inhibited by ritonavir, nirmatrelvir is primarily excreted, unchanged, in urine. Because of intended use of nirmatrelvir among individuals with hepatic impairment, this Phase 1 study (NCT05005312) evaluated the effects of hepatic impairment on nirmatrelvir PK parameters to assess the potential need for any dose adjustments in this population. Participants with normal hepatic function or moderate hepatic impairment (n = 8 each) were administered a single 100-mg nirmatrelvir dose, with 100 mg of ritonavir administered 12 hours before, together with, and 12 and 24 hours after nirmatrelvir. Nirmatrelvir median plasma concentrations and systemic exposure measured by area under the plasma concentration-time curve from time zero extrapolated to infinite time and maximum observed plasma concentration values were comparable in both groups. Nirmatrelvir/ritonavir had an acceptable safety profile in both groups, and no clinically significant changes in laboratory measurements, vital signs, or electrocardiogram assessments were observed. Based on these results, no dose adjustment is deemed necessary in patients with moderate hepatic impairment and, by extension, in patients with mild hepatic impairment.

Resistance-associated mutations to the anti-SARS-CoV-2 agent nirmatrelvir: Selection not induction

Mutations associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resistance to antiprotease nirmatrelvir were reported. We aimed to detect them in SARS-CoV-2 genomes and quasispecies retrieved in our institute before drug availability in January 2022 and to analyze the impact of mutations on protease (3CLpro) structure. We sought for 38 3CLpro nirmatrelvir resistance mutations in a set of 62 673 SARS-CoV-2 genomes obtained in our institute from respiratory samples collected between 2020 and 2023 and for these mutations in SARS-CoV-2 quasispecies for 90 samples collected in 2020, using Python. SARS-CoV-2 protease with major mutation E166V was generated with Swiss Pdb Viewer and Molegro Molecular Viewer. We detected 22 (58%) of the resistance-associated mutations in 417 (0.67%) of the genomes analyzed; 325 (78%) of these genomes had been obtained from samples collected in 2020-2021. APOBEC signatures were found for 12/22 mutations. We also detected among viral quasispecies from 90 samples some minority reads harboring any of 15 nirmatrelvir resistance mutations, including E166V. Also, we predicted that E166V has a very limited effect on 3CLpro structure but may prevent drug attachment. Thus, we evidenced that mutations associated with nirmatrelvir resistance pre-existed in SARS-CoV-2 before drug availability. These findings further warrant SARS-CoV-2 genomic surveillance and SARS-CoV-2 quasispecies characterization.

Clinical Effectiveness of Ritonavir-Boosted Nirmatrelvir-A Literature Review

Nirmatrelvir/Ritonavir is an oral treatment for mild to moderate COVID-19 cases with a high risk for a severe course of the disease. For this paper, a comprehensive literature review was performed, leading to a summary of currently available data on Nirmatrelvir/Ritonavir's ability to reduce the risk of progressing to a severe disease state. Herein, the focus lies on publications that include comparisons between patients receiving Nirmatrelvir/Ritonavir and a control group. The findings can be summarized as follows: Data from the time when the Delta-variant was dominant show that Nirmatrelvir/Ritonavir reduced the risk of hospitalization or death by 88.9% for unvaccinated, non-hospitalized high-risk individuals. Data from the time when the Omicron variant was dominant found decreased relative risk reductions for various vaccination statuses: between 26% and 65% for hospitalization. The presented papers that differentiate between unvaccinated and vaccinated individuals agree that unvaccinated patients benefit more from treatment with Nirmatrelvir/Ritonavir. However, when it comes to the dependency of potential on age and comorbidities, further studies are necessary. From the available data, one can conclude that Nirmatrelvir/Ritonavir cannot substitute vaccinations; however, its low manufacturing cost and easy administration make it a valuable tool in fighting COVID-19, especially for countries with low vaccination rates.

The Development of an Oral Solution Containing Nirmatrelvir and Ritonavir and Assessment of Its Pharmacokinetics and Stability

Paxlovid®, a co-packaged medication comprised of separate tablets containing two active ingredients, nirmatrelvir (NRV) and ritonavir (RTV), exhibits good effectiveness against coronavirus disease 2019 (COVID-19). However, the size of the NRV/RTV tablets makes them difficult for some patients to swallow, especially the elderly and those with dysphagia. Therefore, an oral liquid formulation that can overcome this shortcoming and improve patient compliance is required. In this study, we developed a liquid formulation containing NRV and RTV by adopting strategies that used co-solvents and surfactants to enhance the solubility and inhibit possible recrystallization. The in vitro release results showed that NRV and RTV could be maintained at high concentrations in solution for a certain period in the investigated media. In vivo studies in rats showed that the oral bioavailability of NRV/RTV solution was significantly enhanced. Compared to Paxlovid® tablets, the AUC(0-t) of NRV and RTV increased by 6.1 and 3.8 times, respectively, while the Cmax increased by 5.5 times for both. Furthermore, the promoting effect of the absorption of RTV on the bioavailability of NRV was confirmed. Experiments with a beagle showed a similar trend. Stability studies were also conducted at 4 °C, 25 °C, and 40 °C for 90 days, indicating that the oral liquid formulation was physically and chemically stable. This study can be used as a valuable resource for developing and applying oral liquid NRV/RTV formulations in a clinical context.

Exploring Paxlovid Efficacy in COVID-19 Patients with MAFLD: Insights from a Single-Center Prospective Cohort Study

This study investigates the intricate interplay between Metabolic-associated Fatty Liver Disease (MAFLD) and COVID-19, exploring the impact of MAFLD on disease severity, outcomes, and the efficacy of the antiviral agent Paxlovid (nirmatrelvir/ritonavir). MAFLD, affecting a quarter of the global population, emerges as a potential risk factor for severe COVID-19, yet the underlying pathophysiological mechanisms remain elusive. This study focuses on the clinical significance of Paxlovid, the first orally bioavailable antiviral agent granted Emergency Use Authorization in the United States. Notably, outcomes from phase II/III trials exhibit an 88% relative risk reduction in COVID-19-associated hospitalization or mortality among high-risk patients. Despite conflicting data on the association between MAFLD and COVID-19 severity, this research strives to bridge the gap by evaluating the effectiveness of Paxlovid in MAFLD patients with COVID-19, addressing the scarcity of relevant studies.

Stably-Inverted Apical-Out Human Upper Airway Organoids for SARS-CoV-2 Infection and Therapeutic Testing

Apical-out organoids produced through eversion triggered by extra-organoid extracellular matrix (ECM) removal or degradation are generally small, structurally variable, and limited for viral infection and therapeutics testing. This work describes ECM-encapsulating, stably-inverted apical-out human upper airway organoids (AORBs) that are large (~500 μm diameter), consistently spherical, recapitulate in vivo-like cellular heterogeneity, and maintain their inverted morphology for over 60 days. Treatment of AORBs with IL-13 skews differentiation towards goblet cells and the apical-out geometry allows extra-organoid mucus collection. AORB maturation for 14 days induces strong co-expression of ACE2 and TMPRSS2 to allow high-yield infection with five SARS-CoV-2 variants. Dose-response analysis of three well-studied SARS-CoV-2 antiviral compounds [remdesivir, bemnifosbuvir (AT-511), and nirmatrelvir] shows AORB antiviral assays to be comparable to gold-standard air-liquid interface cultures, but with higher throughput (~10-fold) and fewer cells (~100-fold). While this work focuses on SARS-CoV-2 applications, the consistent AORB shape and size, and one-organoid-per-well modularity broadly impacts in vitro human cell model standardization efforts in line with economic imperatives and recently updated FDA regulation on therapeutic testing.

SARS-CoV-2 Antiviral Prescribing Gaps Among Non-Hospitalized High-Risk Adults

Within a multi-state clinical cohort, SARS-CoV-2 antiviral prescribing patterns were evaluated from April 2022-June 2023 among non-hospitalized SARS-CoV-2-infected patients with risk factors for severe COVID-19. Among 3,247 adults, only 31.9% were prescribed an antiviral agent (87.6% nirmatrelvir/ritonavir, 11.9% molnupiravir, 0.5% remdesivir), highlighting the need to identify and address treatment barriers.

Transplacental passage of nirmatrelvir in pregnant women with COVID-19

The transplacental passage of nirmatrelvir in pregnant women with COVID‐19 is limited and reinforces the safety of using Paxlovid in pregnancy.

Effectiveness of Vaccines and Antiviral Drugs in Preventing Severe and Fatal COVID-19, Hong Kong

We compared the effectiveness and interactions of molnupiravir and nirmatrelvir/ritonavir and 2 vaccines, CoronaVac and Comirnaty, in a large population of inpatients with COVID-19 in Hong Kong. Both the oral antiviral drugs and vaccines were associated with lower risks for all-cause mortality and progression to serious/critical/fatal conditions (study outcomes). No significant interaction effects were observed between the antiviral drugs and vaccinations; their joint effects were additive. If antiviral drugs were prescribed within 5 days of confirmed COVID-19 diagnosis, usage was associated with lower risks for the target outcomes for patients >60, but not <60, years of age; no significant clinical benefit was found if prescribed beyond 5 days. Among patients >80 years of age, 3-4 doses of Comirnaty vaccine were associated with significantly lower risks for target outcomes. Policies should encourage COVID-19 vaccination, and oral antivirals should be made accessible to infected persons within 5 days of confirmed diagnosis.

Association of nirmatrelvir for acute SARS-CoV-2 infection with subsequent Long COVID symptoms in an observational cohort study

Oral nirmatrelvir/ritonavir is approved as treatment for acute COVID-19, but the effect of treatment during acute infection on risk of Long COVID is unknown. We hypothesized that nirmatrelvir treatment during acute SARS-CoV-2 infection reduces risk of developing Long COVID and rebound after treatment is associated with Long COVID. We conducted an observational cohort study within the Covid Citizen Science (CCS) study, an online cohort study with over 100 000 participants. We included vaccinated, nonhospitalized, nonpregnant individuals who reported their first SARS-CoV-2 positive test March-August 2022. Oral nirmatrelvir/ritonavir treatment was ascertained during acute SARS-CoV-2 infection. Patient-reported Long COVID symptoms, symptom rebound and test-positivity rebound were asked on subsequent surveys at least 3 months after SARS-CoV-2 infection. A total of 4684 individuals met the eligibility criteria, of whom 988 (21.1%) were treated and 3696 (78.9%) were untreated; 353/988 (35.7%) treated and 1258/3696 (34.0%) untreated responded to the Long COVID survey (n = 1611). Among 1611 participants, median age was 55 years and 66% were female. At 5.4 ± 1.3 months after infection, nirmatrelvir treatment was not associated with subsequent Long COVID symptoms (odds ratio [OR]: 1.15; 95% confidence interval [CI]: 0.80-1.64; p = 0.45). Among 666 treated who answered rebound questions, rebound symptoms or test positivity were not associated with Long COVID symptoms (OR: 1.34; 95% CI: 0.74-2.41; p = 0.33). Within this cohort of vaccinated, nonhospitalized individuals, oral nirmatrelvir treatment during acute SARS-CoV-2 infection and rebound after nirmatrelvir treatment were not associated with Long COVID symptoms more than 90 days after infection.

Oral Nirmatrelvir and Ritonavir for Coronavirus Disease 2019 in Vaccinated, Nonhospitalized Adults Aged 18-50 Years

BACKGROUND

The effects of nirmatrelvir/ritonavir (NMV/r [Paxlovid]) on coronavirus disease 2019 (COVID-19) outcomes in younger vaccinated adults are unclear. The objective of this study was to assess if NMV/r use in vaccinated adults aged ≤50 years is associated with improved outcomes and to identify beneficial and nonbeneficial subgroups.

METHODS

In this cohort study, we generated 2 propensity-matched cohorts of 2547 patients from an 86 119-person cohort assembled from the TriNetX database. Patients in 1 cohort received NMV/r, and patients in the matched control cohort did not. The main outcome was composite of all-cause emergency department visits, hospitalization, and mortality.

RESULTS

The composite outcome was detected in 4.9% of the NMV/r cohort and 7.0% of the non-NMV/r cohort (odds ratio, 0.683 [95% confidence interval, .540-.864]; P = .001), indicating a 30% relative risk reduction. The number needed to treat (NNT) for the primary outcome was 47. Subgroup analyses found significant associations for patients with cancer (NNT = 45), cardiovascular disease (NNT = 30), and both conditions (NNT = 16). No benefit was found for patients with only chronic lower respiratory disorders (asthma/chronic obstructive pulmonary disease [COPD]) or without serious comorbidities. Thirty-two percent of NMV/r prescriptions in the overall database were for 18- to 50-year-olds.

CONCLUSIONS

NMV/r use in vaccinated adults aged 18-50 years, especially with serious comorbidities, was associated with reduced all-cause hospital visits, hospitalization, and mortality in the first 30 days of COVID-19 illness. However, NMV/r in patients without significant comorbidities or with only asthma/COPD had no association of benefit. Therefore, identifying high-risk patients should be a priority and overprescription should be avoided.

Multidrug-resistant mutations to antiviral and antibody therapy in an immunocompromised patient infected with SARS-CoV-2

BACKGROUND

Antiviral and antibody therapies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are being recommended for high-risk patients, but the potential for the development of multidrug-resistant mutations in immunocompromised patients is unclear.

METHODS

To investigate the treatment course in cases of prolonged viral shedding in an immunocompromised patient with SARS-CoV-2 infection, we conducted longitudinal measurements of laboratory tests, chest computed tomography (CT) image evaluations, antibody titers, and antigen levels in nasopharyngeal swabs. Furthermore, we performed whole-genome sequencing and digital PCR analysis to examine the mechanisms of drug resistance.

FINDINGS

We present a case of a 65-year-old man with a history of malignant lymphoma who was treated with multiple antiviral and antibody therapies, including sotrovimab, remdesivir, paxlovid (nirmatrelvir/ritonavir), and molnupiravir. Initially, viral antigen levels decreased after treatments. However, after the virus rebounded, the patient showed no virologic response. The viral genome analysis revealed a single Omicron subvariant (BA.1.1), which evolved within the host during the disease progression. The viruses had acquired multiple resistance mutations to nirmatrelvir (3 chymotrypsin-like protease [3CLpro] E166 A/V), sotrovimab (spike P337L and E340K), and remdesivir (RNA-dependent RNA polymerase [RdRp] V166L).

CONCLUSIONS

Our results indicate that viruses with multidrug-resistant mutations and survival fitness persist in the infected subpopulation after drug selection pressure.

FUNDING

This study was supported by the JSPS KAKENHI Early-Career Scientists 18K16292 (Y.H.), Grant-in-Aid for Scientific Research (B) 20H03668 and 23H02955 (Y.H.), the YASUDA Medical Foundation (Y.H.), the Uehara Memorial Foundation (Y.H.), the Takeda Science Foundation (Y.H.), and Kato Memorial Bioscience Foundation (Y.H.).

Oral Molnupiravir and Nirmatrelvir/Ritonavir for the Treatment of COVID-19: A Literature Review with a Focus on Real-World Evidence

Vaccines remain the cornerstone of medical prevention and are highly effective in reducing the risk of severe disease and death due to coronavirus disease 2019 (COVID-19). In the context of expanding the therapeutic armamentarium against COVID-19, molnupiravir (Lagevrio) and ritonavir-boosted nirmatrelvir (Paxlovid) were developed, constituting the first effective oral treatments against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this narrative review, we retrospectively inquired into the clinical trials and real-world studies investigating the efficacy of these agents. Overall, clinical trials and real-world studies have demonstrated the efficacy of both agents in reducing hospitalization and death rates in COVID-19 patients. As per current recommendations, their use is suggested in patients with mild to moderate symptoms who are at high risk of developing severe disease. Nevertheless, limited data exist regarding their efficacy in specific subpopulations, such as immunocompromised patients, those with severe kidney disease, pregnant women, and children.

A comprehensive study of SARS-CoV-2 main protease (Mpro) inhibitor-resistant mutants selected in a VSV-based system

Nirmatrelvir was the first protease inhibitor (PI) specifically developed against the SARS-CoV-2 main protease (3CLpro/Mpro) and licensed for clinical use. As SARS-CoV-2 continues to spread, variants resistant to nirmatrelvir and other currently available treatments are likely to arise. This study aimed to identify and characterize mutations that confer resistance to nirmatrelvir. To safely generate Mpro resistance mutations, we passaged a previously developed, chimeric vesicular stomatitis virus (VSV-Mpro) with increasing, yet suboptimal concentrations of nirmatrelvir. Using Wuhan-1 and Omicron Mpro variants, we selected a large set of mutants. Some mutations are frequently present in GISAID, suggesting their relevance in SARS-CoV-2. The resistance phenotype of a subset of mutations was characterized against clinically available PIs (nirmatrelvir and ensitrelvir) with cell-based and biochemical assays. Moreover, we showed the putative molecular mechanism of resistance based on in silico molecular modelling. These findings have implications on the development of future generation Mpro inhibitors, will help to understand SARS-CoV-2 protease-inhibitor-resistance mechanisms and show the relevance of specific mutations in the clinic, thereby informing treatment decisions.

Substitutions in SARS-CoV-2 Mpro Selected by Protease Inhibitor Boceprevir Confer Resistance to Nirmatrelvir

Nirmatrelvir, which targets the SARS-CoV-2 main protease (Mpro), is the first-in-line drug for prevention and treatment of severe COVID-19, and additional Mpro inhibitors are in development. However, the risk of resistance development threatens the future efficacy of such direct-acting antivirals. To gain knowledge on viral correlates of resistance to Mpro inhibitors, we selected resistant SARS-CoV-2 under treatment with the nirmatrelvir-related protease inhibitor boceprevir. SARS-CoV-2 selected during five escape experiments in VeroE6 cells showed cross-resistance to nirmatrelvir with up to 7.3-fold increased half-maximal effective concentration compared to original SARS-CoV-2, determined in concentration-response experiments. Sequence analysis revealed that escape viruses harbored Mpro substitutions L50F and A173V. For reverse genetic studies, these substitutions were introduced into a cell-culture-infectious SARS-CoV-2 clone. Infectivity titration and analysis of genetic stability of cell-culture-derived engineered SARS-CoV-2 mutants showed that L50F rescued the fitness cost conferred by A173V. In the concentration-response experiments, A173V was the main driver of resistance to boceprevir and nirmatrelvir. Structural analysis of Mpro suggested that A173V can cause resistance by making boceprevir and nirmatrelvir binding less favorable. This study contributes to a comprehensive overview of the resistance profile of the first-in-line COVID-19 treatment nirmatrelvir and can thus inform population monitoring and contribute to pandemic preparedness.

Real-World Effectiveness of Nirmatrelvir/Ritonavir on Coronavirus Disease 2019-Associated Hospitalization Prevention: A Population-based Cohort Study in the Province of Quebec, Canada

BACKGROUND

Nirmatrelvir/ritonavir has shown to reduce COVID-19 hospitalization and death before Omicron, but updated real-world evidence studies are needed. This study aimed to assess whether nirmatrelvir/ritonavir reduces the risk of COVID-19-associated hospitalization among high-risk outpatients.

METHODS

A retrospective cohort study of outpatients with SARS-CoV-2 between March 15 and 15 October 2022, using data from the Quebec clinico-administrative databases. Outpatients treated with nirmatrelvir/ritonavir were compared with infected ones not receiving nirmatrelvir/ritonavir using propensity-score matching. Relative risk (RR) of COVID-19-associated hospitalization within 30 days was assessed using a Poisson regression.

RESULTS

A total of 8402 treated outpatients were matched to controls. Regardless of vaccination status, nirmatrelvir/ritonavir treatment was associated with a 69% reduced RR of hospitalization (RR: .31; 95% CI: .28; .36; number needed to treat [NNT] = 13). The effect was more pronounced in outpatients with incomplete primary vaccination (RR: .04; 95% CI: .03; .06; NNT = 8), while no benefit was found in those with a complete primary vaccination (RR: .93; 95% CI: .78; 1.08). Subgroups analysis among high-risk outpatients with a complete primary vaccination showed that nirmatrelvir/ritonavir treatment was associated with a significant decrease in the RR of hospitalization in severely immunocompromised outpatients (RR: .66; 95% CI: .50; .89; NNT = 16) and in high-risk outpatients aged ≥70 years (RR: .50; 95% CI: .34; .74; NNT = 10) when the last dose of the vaccine was received at least 6 months ago.

CONCLUSIONS

Nirmatrelvir/ritonavir reduces the risk of COVID-19-associated hospitalization among incompletely vaccinated high-risk outpatients and among some subgroups of completely vaccinated high-risk outpatients.

Recent Advances in SARS-CoV-2 Main Protease Inhibitors: From Nirmatrelvir to Future Perspectives

The main protease (Mpro) plays a pivotal role in the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is considered a highly conserved viral target. Disruption of the catalytic activity of Mpro produces a detrimental effect on the course of the infection, making this target one of the most attractive for the treatment of COVID-19. The current success of the SARS-CoV-2 Mpro inhibitor Nirmatrelvir, the first oral drug for the treatment of severe forms of COVID-19, has further focused the attention of researchers on this important viral target, making the search for new Mpro inhibitors a thriving and exciting field for the development of antiviral drugs active against SARS-CoV-2 and related coronaviruses.

Paxlovid as a potential treatment for long COVID

INTRODUCTION

On 31 July 2023, the United States Department of Health and Human Services announced the formation of the Office of Long COVID Research and Practice and the United States National Institutes of Health opened enrollment for RECOVER-Vital, a randomized study to evaluate new treatment options for long Coronavirus (long COVID).

AREAS COVERED

The RECOVER Initiative is a $1.15 billion research platform intended to describe, categorize, treat, and prevent long-term symptoms following infection by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‑CoV‑2), the virus that causes Coronavirus (COVID-19). More than 200 symptoms have been associated with long COVID, potentially affecting nearly all body systems, and current estimates suggest that between 7 million and 23 million Americans have developed long COVID. However, there are no approved treatments for this condition.

EXPERT OPINION

The first prospective, randomized study of the RECOVER research initiative, RECOVER-Vital, will evaluate the SARS-CoV-2 antiviral nirmatrelvir/ritonavir (Paxlovid) as a potential treatment for long COVID. This manuscript explores what is known about Paxlovid to treat and prevent long COVID and examines the rationale for addressing this condition with an antiviral agent.

Efficacy and safety of paxlovid (nirmatrelvir/ritonavir) in the treatment of COVID-19: An updated meta-analysis and trial sequential analysis

Our study is aimed to access the efficacy and safety outcomes for coronavirus disease 2019 (COVID-19) patients treated with Paxlovid. According to inclusion and exclusion criteria, databases were used to retrieve articles from 1 January 2020 to 1 January 2023. Article screening, quality evaluation and data extraction were completed and cross-checked. The meta-analysis and trial sequential analysis (TSA) were conducted using RevMan, StataMP, and TSA software. A total of 42 original articles were included. Overall meta-analysis results showed that for death, hospitalisation, death or hospitalisation, emergency department (ED) visit, intensive care unit (ICU) admission, and extra oxygen requirement outcomes, every odds ratio (OR) was <1 and p < 0.05. For rebound outcome, the OR was >1 and p > 0.05. For adverse events (AEs) outcome, the OR was >1 and p < 0.05. In conclusion, Paxlovid effectively reduced the risks of death, hospitalisation, death or hospitalisation, ED visit, ICU admission, and extra oxygen requirement. There was no significant statistical difference considering rebound, but people should pay attention to possible AEs. However, for rebound and AEs outcomes, observations in certain subgroups suggested conclusions contrary to the overall meta-analysis. Trial sequential analysis indicated these two outcomes have a risk of false negative or false positive conclusions, so additional original studies are needed for further validation.

Post-marketing safety concerns with nirmatrelvir: A disproportionality analysis of spontaneous reports submitted to the FDA Adverse Event Reporting System

AIMS

Nirmatrelvir is an antiviral drug with a novel mechanism of action, targeting the 3-CL protease, and is used in the treatment of COVID-19. However, the potential side effects have not yet been fully studied. The aim of this study was to identify potential safety signals of nirmatrelvir by analysing post-marketing safety data based on the largest publicly available worldwide pharmacovigilance database.

METHODS

We analysed nirmatrelvir adverse events to identify and characterize relevant safety signals based on the FDA Adverse Event Reporting System database in 2022. The case/non-case approach was used to estimate the reporting odds ratio (ROR) and information component (IC) with relevant confidence intervals (95% CI) for adverse events (AEs) that numbered 4 or more.

RESULTS

A total of 26 846 cases were included. Disease recurrence (ROR [95% CI] = 413.2 [395.6-431.59]), dysgeusia (ROR [95% CI] = 110.84 [106.04-115.85]), anosmia (ROR [95% CI] = 15.21 [12.76-18.11]), ageusia (ROR [95% CI] = 9.80 [8.50-11.3]) and urticaria (ROR [95% CI] = 1.91 [1.69-2.17]) were the main safety signals. In addition, abdominal pain upper and skin toxicity were two specific safety signals of nirmatrelvir. In the pregnant population, there was a significant increased ROR for life-threatening conditions (ROR [95% CI] = 8.00 [1.77-36.20]).

CONCLUSIONS

Our study identified that the main and specific safety signals of nirmatrelvir were disease recurrence, dysgeusia, abdominal pain upper and skin toxicity. Clinicians and pharmacists should be vigilant of these AEs, although differentiating between COVID-19 symptoms and AEs can be challenging. Notably, a potential safety concern of nirmatrelvir should be a warning based on a small number of events in the pregnant population. However, the available data are insufficient, and further continued pharmacovigilance and surveillance is needed to fully understand this issue.

Identifying Innate Resistance Hotspots for SARS-CoV-2 Antivirals Using In Silico Protein Techniques

The development and approval of antivirals against SARS-CoV-2 has further equipped clinicians with treatment strategies against the COVID-19 pandemic, reducing deaths post-infection. Extensive clinical use of antivirals, however, can impart additional selective pressure, leading to the emergence of antiviral resistance. While we have previously characterized possible effects of circulating SARS-CoV-2 missense mutations on proteome function and stability, their direct effects on the novel antivirals remains unexplored. To address this, we have computationally calculated the consequences of mutations in the antiviral targets: RNA-dependent RNA polymerase and main protease, on target stability and interactions with their antiviral, nucleic acids, and other proteins. By analyzing circulating variants prior to antiviral approval, this work highlighted the inherent resistance potential of different genome regions. Namely, within the main protease binding site, missense mutations imparted a lower fitness cost, while the opposite was noted for the RNA-dependent RNA polymerase binding site. This suggests that resistance to nirmatrelvir/ritonavir combination treatment is more likely to occur and proliferate than that to molnupiravir. These insights are crucial both clinically in drug stewardship, and preclinically in the identification of less mutable targets for novel therapeutic design.

Comparative Evaluation of GS-441524, Teriflunomide, Ruxolitinib, Molnupiravir, Ritonavir, and Nirmatrelvir for In Vitro Antiviral Activity against Feline Infectious Peritonitis Virus

Feline infectious peritonitis (FIP), caused by feline coronavirus (FcoV), is considered one of the most enigmatic diseases in cats. Developing effective drugs for FIP is crucial due to its global prevalence and severity. In this study, six antiviral drugs were tested for their cytotoxicity, cell viability, and antiviral efficacies in Crandell-Reese feline kidney cells. A cytotoxicity assay demonstrated that these drugs were safe to be used with essentially no cytotoxicity with concentrations as high as 250 µM for ruxolitinib; 125 µM for GS441524; 63 µM for teriflunomide, molnupiravir, and nirmatrelvir; and 16 µM for ritonavir. GS441524 and nirmatrelvir exhibited the least detrimental effects on the CRFK cells, with 50% cytotoxic concentration (CC50) values of 260.0 µM and 279.1 µM, respectively, while ritonavir showed high toxicity (CC50 = 39.9 µM). In the dose-response analysis, GS441524, nirmatrelvir, and molnupiravir demonstrated promising results with selectivity index values of 165.54, 113.67, and 29.27, respectively, against FIPV. Our study suggests that nirmatrelvir and molnupiravir hold potential for FIPV treatment and could serve as alternatives to GS441524. Continued research and development of antiviral drugs are essential to ensure the well-being of companion animals and improve our preparedness for future outbreaks of coronaviruses affecting animals and humans alike.

Viral target and metabolism-based rationale for combined use of recently authorized small molecule COVID-19 medicines: Molnupiravir, nirmatrelvir, and remdesivir

The COVID-19 pandemic remains a major health concern worldwide, and SARS-CoV-2 is continuously evolving. There is an urgent need to identify new antiviral drugs and develop novel therapeutic strategies. Combined use of newly authorized COVID-19 medicines including molnupiravir, nirmatrelvir, and remdesivir has been actively pursued. Mechanistically, nirmatrelvir inhibits SARS-CoV-2 replication by targeting the viral main protease (Mpro ), a critical enzyme in the processing of the immediately translated coronavirus polyproteins for viral replication. Molnupiravir and remdesivir, on the other hand, inhibit SARS-CoV-2 replication by targeting RNA-dependent RNA-polymerase (RdRp), which is directly responsible for genome replication and production of subgenomic RNAs. Molnupiravir targets RdRp and induces severe viral RNA mutations (genome), commonly referred to as error catastrophe. Remdesivir, in contrast, targets RdRp and causes chain termination and arrests RNA synthesis of the viral genome. In addition, all three medicines undergo extensive metabolism with strong therapeutic significance. Molnupiravir is hydrolytically activated by carboxylesterase-2 (CES2), nirmatrelvir is inactivated by cytochrome P450-based oxidation (e.g., CYP3A4), and remdesivir is hydrolytically activated by CES1 but covalently inhibits CES2. Additionally, remdesivir and nirmatrelvir are oxidized by the same CYP enzymes. The distinct mechanisms of action provide strong rationale for their combined use. On the other hand, these drugs undergo extensive metabolism that determines their therapeutic potential. This review discusses how metabolism pathways and enzymes involved should be carefully considered during their combined use for therapeutic synergy.

Successful treatment of persisting SARS-CoV-2 infection in an immunocompromised patient with repeated nirmatrelvir/ritonavir courses: a case report

BACKGROUND

In immunocompromised patients, persistent SARS-CoV-2 viral shedding and relapsing COVID-19 pneumonia have been described. Currently, little is known about the management of persisting COVID-19, and immunocompromised patients are recommended to be treated using antivirals and immunomodulatory therapies at similar doses and durations as the general population. Previous case reports have described treatment with repeated and prolonged courses of remdesivir and some evidence is emerging in the use of nirmatrelvir/ritonavir combination (NMV/r).

METHODS

We describe a patient with recent chemotherapy including rituximab for follicular lymphoma with persisting SARS-CoV-2 infection. Polymerase chain reaction tests (PCR), cycle threshold values and blood SARS-CoV-2 antigen levels were evaluated.

RESULTS

The patient presented with persisting SARS-CoV-2 with relapsing COVID-19 pneumonia. The patient was treated successfully with repeated courses of NMV/r without any observed adverse effects. After the third, prolonged course, the patient remained afebrile and PCR negative, and no relapses have been observed four months after the third NMV/r course.

CONCLUSIONS

Nirmatrelvir-ritonavir could offer a more accessible alternative to remdesivir. Further research and guidelines for persisting SARS-CoV-2 infection in immunocompromised patients are urgently needed.

Physiologically-Based Pharmacokinetic Modeling of PAXLOVID™ with First-Order Absorption Kinetics

PURPOSE

PAXLOVID™ is nirmatrelvir tablets co-packaged with ritonavir tablets. Ritonavir is used as a pharmacokinetics (PK) enhancer to reduce metabolism and increase exposure of nirmatrelvir. This is the first disclosure of Paxlovid physiologically-based pharmacokinetic (PBPK) model.

METHODS

Nirmatrelvir PBPK model with first-order absorption kinetics was developed using in vitro, preclinical, and clinical data of nirmatrelvir in the presence and absence of ritonavir. Clearance and volume of distribution were derived from nirmatrelvir PK obtained using a spray-dried dispersion (SDD) formulation where it is considered to be dosed as an oral solution, and absorption is near complete. The fraction of nirmatrelvir metabolized by CYP3A was estimated based on in vitro and clinical ritonavir drug-drug interaction (DDI) data. First-order absorption parameters were established for both SDD and tablet formulation using clinical data. Nirmatrelvir PBPK model was verified with both single and multiple dose human PK data, as well as DDI studies. Simcyp® first-order ritonavir compound file was also verified with additional clinical data.

RESULTS

The nirmatrelvir PBPK model described the observed PK profiles of nirmatrelvir well with predicted AUC and Cmax values within ± 20% of the observed. The ritonavir model performed well resulting in predicted values within twofold of observed.

CONCLUSIONS

Paxlovid PBPK model developed in this study can be applied to predict PK changes in special populations, as well as model the effect of victim and perpetrator DDI. PBPK modeling continues to play a critical role in accelerating drug discovery and development of potential treatments for devastating diseases such as COVID-19. NCT05263895, NCT05129475, NCT05032950 and NCT05064800.

Synergistic Activity of Remdesivir-Nirmatrelvir Combination on a SARS-CoV-2 In Vitro Model and a Case Report

BACKGROUND

This study aims to investigate the activity of the remdesivir-nirmatrelvir combination against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and to report a case of Coronavirus Disease 2019 (COVID-19) cured with this combination.

METHODS

A Vero E6 cell-based infection assay was used to investigate the in vitro activity of the remdesivir-nirmatrelvir combination. The SARS-CoV-2 strains tested were 20A.EU1, BA.1 and BA.5. After incubation, a viability assay was performed. The supernatants were collected and used for viral titration. The Highest Single Agent (HSA) reference model was calculated. An HSA score >10 is considered synergic.

RESULTS

Remdesivir and nirmatrelvir showed synergistic activity at 48 and 72 h, with an HSA score of 52.8 and 28.6, respectively (p < 0.0001). These data were confirmed by performing supernatant titration and against the omicron variants: the combination reduced the viral titer better than the more active compound alone. An immunocompromised patient with prolonged and critical COVID-19 was successfully treated with remdesivir, nirmatrelvir/ritonavir, tixagevimab/cilgavimab and dexamethasone, with an excellent clinical-radiological response. However, she required further off-label prolonged therapy with nirmatrelvir/ritonavir until she tested negative.

CONCLUSIONS

Remdesivir-nirmatrelvir combination has synergic activity in vitro. This combination may have a role in immunosuppressed patients with severe COVID-19 and prolonged viral shedding.

Nirmatrelvir and ritonavir combination: an antiviral therapy for COVID-19

INTRODUCTION

The emergence of the Omicron SARS-CoV-2 variant of concern in late November 2021 presaged yet another stage of the COVID-19 pandemic. Paxlovid, a co-packaged dosage form of two antiviral drugs (nirmatrelvir and ritonavir) developed by Pfizer, received its first FDA Emergency Use Authorization (EUA) and conditional marketing by European Medical Agency in patients at high risk of developing severe COVID-19.

AREAS COVERED

We reviewed the timeline of the drug nirmatrelvir from its discovery to authorization by FDA. After 1 year of its authorization, numerous studies and reports on paxlovid's use and post-use consequences are available. This review summarizes the complete journey of paxlovid from its development, preclinical studies, clinical trials, regulatory approvals, ongoing clinical trials, and safety measures, followed by discussions on recent updates on drug-drug interactions, adverse effects, and relapse of COVID-19.

EXPERT OPINION

Paxlovid, a new oral antiviral therapy for COVID-19, has shown promising results in clinical trials and has the potential to be effective against the pandemic, particularly for individuals at high risk of severe illness. Comorbidity usage and pharmacovigilance will play a significant stake in the future of paxlovid development. Second-generation Mpro inhibitors play an important role in the upcoming problems associated with COVID-19.

Clinical effectiveness of nirmatrelvir plus ritonavir in the treatment of COVID-19 in patients with cirrhosis

OBJECTIVES

This retrospective cohort study assessed the clinical effectiveness of nirmatrelvirplus ritonavir (NMV-r) in treating COVID-19 in patients with liver cirrhosis(LC).

METHODS

The data of non-hospitalized adult patients with LC who had COVID-19 were selected from the TriNetX platform for the period between 1 March 20201 March 2020, and 31 December 202231 December 2022. Propensity score matching was used to match patients receiving NMV-r (theNMV-r group) with those not receiving NMV-r (the control group). Hazard ratios(HRs) along with 95% confidence intervals (CIs) for the primary outcome - a composite of all-cause hospitalization or mortality during the 30-day follow-up period - were calculated and compared.

RESULTS

Two cohorts of 2,369 patients each with balanced baseline characteristics were identified.During the follow-up period, the NMV-r group had a lower risk of all-cause hospitalization or mortality (HR, 0.642;95% CI, 0.503-0.819) than did the control group.NMV-r was also associated with a reduced risk of individual all-cause hospitalization (HR 0.681, 95% CI 0.530-0.876])and all-cause mortality (HR, 0.270; 95% CI,0.129-0.562). This association was consistently observed in the subgroups of age, sex, vaccination status, and LC severity.

CONCLUSIONS

NMV-r can reduce all-cause hospitalization and mortality among patients with LC who have COVID-19.

Efficacy of the oral nucleoside prodrug GS-5245 (Obeldesivir) against SARS-CoV-2 and coronaviruses with pandemic potential

Despite the wide availability of several safe and effective vaccines that can prevent severe COVID-19 disease, the emergence of SARS-CoV-2 variants of concern (VOC) that can partially evade vaccine immunity remains a global health concern. In addition, the emergence of highly mutated and neutralization-resistant SARS-CoV-2 VOCs such as BA.1 and BA.5 that can partially or fully evade (1) many therapeutic monoclonal antibodies in clinical use underlines the need for additional effective treatment strategies. Here, we characterize the antiviral activity of GS-5245, Obeldesivir (ODV), an oral prodrug of the parent nucleoside GS-441524, which targets the highly conserved RNA-dependent viral RNA polymerase (RdRp). Importantly, we show that GS-5245 is broadly potent in vitro against alphacoronavirus HCoV-NL63, severe acute respiratory syndrome coronavirus (SARS-CoV), SARS-CoV-related Bat-CoV RsSHC014, Middle East Respiratory Syndrome coronavirus (MERS-CoV), SARS-CoV-2 WA/1, and the highly transmissible SARS-CoV-2 BA.1 Omicron variant in vitro and highly effective as antiviral therapy in mouse models of SARS-CoV, SARS-CoV-2 (WA/1), MERS-CoV and Bat-CoV RsSHC014 pathogenesis. In all these models of divergent coronaviruses, we observed protection and/or significant reduction of disease metrics such as weight loss, lung viral replication, acute lung injury, and degradation in pulmonary function in GS-5245-treated mice compared to vehicle controls. Finally, we demonstrate that GS-5245 in combination with the main protease (Mpro) inhibitor nirmatrelvir had increased efficacy in vivo against SARS-CoV-2 compared to each single agent. Altogether, our data supports the continuing clinical evaluation of GS-5245 in humans infected with COVID-19, including as part of a combination antiviral therapy, especially in populations with the most urgent need for more efficacious and durable interventions.

Nirmatrelvir/Ritonavir for hemodialysis patients with COVID-19

Background: Hemodialysis patients have a high risk of severe/critical COVID-19 and related high mortality, but nirmatrelvir/ritonavir is not recommended for hemodialysis patients with COVID-19 infection because of lack of evidence of safety. Objectives: Our study aims to evaluate the minimum plasma concentration (Cmin) of nirmatrelvir and its safety of different doses of nirmatrelvir/ritonavir in hemodialysis patients with mild COVID-19. Method: This was a prospective, two step, nonrandomized, open-label study. Participants were treated with nirmatrelvir 150 mg or 300 mg once a day (another 75 mg or 150 mg supplied after hemodialysis) and ritonavir 100 mg twice daily for 5 days, respectively. The primary outcome was the safety of nirmatrelvir/ritonavir, including the Cmin of nirmatrelvir and the number of adverse events (AE). The secondary outcome was the time of viral elimination in hemodialysis patients. Results: Adverse events were happened in 3 and 7 participants in the step 1 and step 2 group, respectively (p = 0.025). Among them, 2 and 6 participants were identified as drug-related adverse events (p = 0.054). No SAE or liver function damage happened. The Cmin of nirmatrelvir in step 1 and step 2 group were 5,294.65 ± 2,370.59 ng/mL and 7,675.67 ± 2,745.22 ng/mL (p = 0.125). The Cmin of the control group was 2,274.10 ± 1,347.25 ng/mL (p = 0.001 compared to step 2 and p = 0.059 compared to step 1). Compared to hemodialysis patients without nirmatrelvir/ritonavir, there were no statistical differences in overall viral elimination time (p = 0.232). Conclusion: In our study, two doses of nirmatrelvir/ritonavir appeared to be excessive for hemodialysis patients. Although all of the patients tolerated 5-day administration, nearly half of the patients experienced drug-related adverse events. In addition, the medication group did not show a significant advantage in the time of viral elimination.

Nirmatrelvir treatment of SARS-CoV-2-infected mice blunts antiviral adaptive immune responses

Alongside vaccines, antiviral drugs are becoming an integral part of our response to the SARS-CoV-2 pandemic. Nirmatrelvir-an orally available inhibitor of the 3-chymotrypsin-like cysteine protease-has been shown to reduce the risk of progression to severe COVID-19. However, the impact of nirmatrelvir treatment on the development of SARS-CoV-2-specific adaptive immune responses is unknown. Here, by using mouse models of SARS-CoV-2 infection, we show that nirmatrelvir administration blunts the development of SARS-CoV-2-specific antibody and T cell responses. Accordingly, upon secondary challenge, nirmatrelvir-treated mice recruited significantly fewer memory T and B cells to the infected lungs and mediastinal lymph nodes, respectively. Together, the data highlight a potential negative impact of nirmatrelvir treatment with important implications for clinical management and might help explain the virological and/or symptomatic relapse after treatment completion reported in some individuals.

Paxlovid for Treating COVID-19 Patients: A Case-Control Study From Two Hospitals in the Eastern Province of Saudi Arabia

Background Coronavirus disease 2019 (COVID-19) is an infectious disease that shortly progressed into an unprecedented pandemic spreading all over the world and causing millions of deaths. Many new COVID-19-specific therapies were suggested for the treatment of the patients at increased risk of progression to severe disease, especially those who were unvaccinated and those with a likely inadequate vaccine response. One of the preferred therapies in this setting is Paxlovid, a combination of the oral protease inhibitors nirmatrelvir and ritonavir. Paxlovid was authorized by the Saudi Ministry of Health for the treatment of mild to moderate COVID-19. This study aimed to report the effects of Paxlovid on the mortality of the COVID-19 patients at Dammam Medical Complex (DMC) and Qatif Complex Hospital (QCH), two hospitals in the Eastern Provence of Saudi Arabia, and compare the results with the international data. Methods The study was a retrospective study that included all the COVID-19 patients who were treated with Paxlovid at DMC and QCH between January and December 2022. Those patients were compared with control COVID-19 patients who did not receive Paxlovid. The patients were included irrespective of their COVID-19 vaccination status. All the patients were managed according to the Saudi Ministry of Health guidelines. They were followed up through the infectious disease virtual clinics and were monitored for ICU admissions and death of any cause for three months following their COVID-19 infections. Results A total of 92 COVID-19 patients were included. The patients consisted of 47 male and 45 female patients (51.09% and 48.91%, respectively). The mean ± standard deviation for the patients' age was 55.58±19.25 years. Twenty-eight patients were given Paxlovid (30.43%). Eighteen patients (19.57%) died. The use of Paxlovid was associated with lower ICU admissions (0.0% vs. 18.75%, P value <0.05) and with lower deaths (3.57% vs 26.56%, P value <0.05) but the Paxlovid group included less immunocompromised patients (7.14% vs. 60.94%, P value <0.001), cancer patients (0.0% vs. 42.19%, P value <0.001), and chronic kidney disease patients (7.14% vs. 29.69%, P value <0.05) than the control group. Conclusion This study suggests that Paxlovid is highly effective in reducing the risk of severe COVID-19 or mortality. However, larger studies with better qualities are needed for a full assessment of the role of Paxlovid in COVID-19 management in Saudi Arabia.

Clinical effectiveness of nirmatrelvir plus ritonavir in patients with COVID-19 and substance use disorders based on real-world data

This study assessed the clinical efficacy of nirmatrelvir plus ritonavir (NMV-r) in treating patients with coronavirus disease-2019 (COVID-19) and substance use disorders (SUDs). This study included two cohorts: the first examined patients with SUDs, with and without a prescription for NMV-r, while the second compared patients prescribed with NMV-r, with and without a diagnosis of SUDs. SUDs were defined using ICD-10 codes, related to SUDs, including alcohol, cannabis, cocaine, opioid, and tobacco use disorders (TUD). Patients with underlying SUDs and COVID-19 were identified using the TriNetX network. We used 1:1 propensity score matching to create balanced groups. The primary outcome of interest was the composite outcome of all-cause hospitalization or death within 30 days. Propensity score matching yielded two matched groups of 10 601 patients each. The results showed that the use of NMV-r was associated with a lower risk of hospitalization or death, 30 days after COVID-19 diagnosis (hazard ratio (HR), 0.640; 95% confidence interval (CI): 0.543-0.754), as well as a lower risk of all-cause hospitalization (HR, 0.699; 95% CI: 0.592-0.826) and all-cause death (HR, 0.084; 95% CI: 0.026-0.273). However, patients with SUDs had a higher risk of hospitalized or death within 30 days of COVID-19 diagnosis than those without SUDs, even with the use of NMV-r (HR, 1.783; 95% CI: 1.399-2.271). The study also found that patients with SUDs had a higher prevalence of comorbidities and adverse socioeconomic determinants of health than those without SUDs. Subgroup analysis showed that the benefits of NMV-r were consistent across most subgroups with different characteristics, including age (patients aged ≥60 years [HR, 0.507; 95% CI: 0.402-0.640]), sex (women [HR, 0.636; 95% CI: 0.517-0.783] and men [HR, 0.480; 95% CI: 0.373-0.618]), vaccine status (vaccinated <2 doses [HR, 0.514; 95% CI: 0.435-0.608]), SUD subtypes (alcohol use disorder [HR, 0.711; 95% CI: 0.511- 0.988], TUD [HR, 0.666; 95% CI: 0.555-0.800]) and Omicron wave (HR, 0.624; 95% CI: 0.536-0.726). Our findings indicate that NMV-r could reduce all-cause hospitalization and death in the treatment of COVID-19 among patients with SUDs and support the use of NMV-r for treating patients with SUDs and COVID-19.

Nirmatrelvir/ritonavir in COVID-19 patients with haematological malignancies: a report from the EPICOVIDEHA registry

Background

Nirmatrelvir/ritonavir treatment decreases the hospitalisation rate in immunocompetent patients with COVID-19, but data on efficacy in patients with haematological malignancy are scarce. Here, we describe the outcome of nirmatrelvir/ritonavir treatment in a large cohort of the latter patients.

Methods

This is a retrospective cohort study from the multicentre EPICOVIDEHA registry (NCT04733729) on patients with haematological malignancy, who were diagnosed with COVID-19 between January and September 2022. Patients receiving nirmatrelvir/ritonavir were compared to those who did not. A logistic regression was run to determine factors associated with nirmatrelvir/ritonavir administration in our sample. Mortality between treatment groups was assessed with Kaplan–Meier survival plots after matching all the patients with a propensity score. Additionally, a Cox regression was modelled to detect factors associated with mortality in patients receiving nirmatrelvir/ritonavir.

Findings

A total of 1859 patients were analysed, 117 (6%) were treated with nirmatrelvir/ritonavir, 1742 (94%) were treated otherwise. Of 117 patients receiving nirmatrelvir/ritonavir, 80% had received ≥1 anti-SARS-CoV-2 vaccine dose before COVID-19 onset, 13% of which received a 2nd vaccine booster. 5% were admitted to ICU. Nirmatrelvir/ritonavir treatment was associated with the presence of extrapulmonary symptoms at COVID-19 onset, for example anosmia, fever, rhinitis, or sinusitis (aOR 2.509, 95%CI 1.448–4.347) and 2nd vaccine booster (aOR 3.624, 95%CI 1.619–8.109). Chronic pulmonary disease (aOR 0.261, 95%CI 0.093–0.732) and obesity (aOR 0.105, 95%CI 0.014–0.776) were not associated with nirmatrelvir/ritonavir use. After propensity score matching, day-30 mortality rate in patients treated with nirmatrelvir/ritonavir was 2%, significantly lower than in patients with SARS-CoV-2 directed treatment other than nirmatrelvir/ritonavir (11%, p = 0.036). No factor was observed explaining the mortality difference in patients after nirmatrelvir/ritonavir administration.

Interpretation

Haematological malignancy patients were more likely to receive nirmatrelvir/ritonavir when reporting extrapulmonary symptoms or 2nd vaccine booster at COVID-19 onset, as opposed to chronic pulmonary disease and obesity. The mortality rate in patients treated with nirmatrelvir/ritonavir was lower than in patients with targeted drugs other than nirmatrelvir/ritonavir.

Funding

EPICOVIDEHA has received funds from Optics COMMIT (COVID-19 Unmet Medical Needs and Associated Research Extension) COVID-19 RFP program by GILEAD Science, United States (Project 2020-8223).

COVID-19 Management Strategies in Solid Organ Transplant Recipients

Solid organ transplant recipients are at high risk of severe coronavirus disease-2019 (COVID-19). If left untreated, it results in high rates of hospitalization, intensive care unit admission and death. Early diagnosis of COVID-19 is essential to ensure the early administration of therapeutics. Treatment of mild-to-moderate COVID-19 with remdesivir, ritonavir-boosted nirmatrelvir, or an anti-spike neutralizing monoclonal antibody may prevent progression to severe and critical COVID-19. Among patients with severe and critical COVID-19, treatment with intravenous remdesivir and immunomodulation is recommended. This review article discusses strategies in the management of solid organ transplant recipients with COVID-19.

Developmental safety of nirmatrelvir in zebrafish (Danio rerio) embryos

BACKGROUND

Nirmatrelvir, in combination with ritonavir, is one of the first orally available antiviral treatment for coronavirus disease 2019 (COVID-19). Symptomatic pregnant women are at increased risk for severe illness and complications that can affect the developing baby. No malformations or lower embryo-fetal survival have been observed when nirmatrelvir were administered to pregnant rats and rabbits. Safety evaluation of drugs used for treating COVID-19 also in pregnancy is urgent for public health, then in this study we further investigated nirmatrelvir developmental toxicity using zebrafish as in vivo model.

MATERIAL AND METHODS

Using the standardized Fish Embryo Toxicity (FET) test, we first determined the lethal concentration 50 (LC50), exposing embryos from gastrula stage up to 120 hr post fertilization (hpf) and daily recording lethality. Then, we exposed embryos to five doses comprising the human therapeutic one and up to the LC50 (25 μM). Morphology was evaluated at 72 and 120 hpf.

RESULTS

Nirmatrelvir did not affect survival rate and did not induce morphological defects up to the human therapeutic dose. Exposure at higher doses (2.4× and 3× the human C_max ) however resulted in decreased hatching rate, reduced growth, slower heartbeat with pericardial edema, reduction of eye dimension, absence of the swim bladder and disruption of the anterior-posterior axis, with lack of tail detachment, spinal curvature and straight and smaller head.

CONCLUSIONS

Our findings in zebrafish embryos add further information about developmental nirmatrelvir safety. Further studies are needed for pharmacological safety assessment of nirmatrelvir exposure during pregnancy.

Structural basis of nirmatrelvir and ensitrelvir activity against naturally occurring polymorphisms of the SARS-CoV-2 main protease

SARS-CoV-2 is the causative agent of COVID-19. The main viral protease (Mpro) is an attractive target for antivirals. The clinically approved drug nirmatrelvir and the clinical candidate ensitrelvir have so far showed great potential for treatment of viral infection. However, the broad use of antivirals is often associated with resistance generation. Herein, we enzymatically characterized 14 naturally occurring Mpro polymorphisms that are close to the binding site of these antivirals. Nirmatrelvir retained its potency against most polymorphisms tested, while mutants G143S and Q189K were associated with diminished inhibition constants. For ensitrelvir, diminished inhibition constants were observed for polymorphisms M49I, G143S, and R188S, but not for Q189K, suggesting a distinct resistance profile between inhibitors. In addition, the crystal structures of selected polymorphisms revealed interactions that were critical for loss of potency. In conclusion, our data will assist the monitoring of potential resistant strains, support the design of combined therapy, as well as assist the development of the next generation of Mpro inhibitors.

Outcome of early treatment of SARS-CoV-2 infection in patients with haematological disorders

Outcome of early treatment of COVID-19 with antivirals or anti-spike monoclonal antibodies (MABs) in patients with haematological malignancies (HM) is unknown. A retrospective study of HM patients treated for mild/moderate COVID-19 between March 2021 and July 2022 was performed. The main composite end-point was treatment failure (severe COVID-19 or COVID-19-related death). We included 328 consecutive patients who received MABs (n = 120, 37%; sotrovimab, n = 73) or antivirals (n = 208, 63%; nirmatrelvir/ritonavir, n = 116) over a median of two days after symptoms started; 111 (33.8%) had non-Hodgkin lymphoma (NHL); 89 (27%) were transplant/CAR-T (chimaeric antigen receptor T-cell therapy) recipients. Most infections (n = 309, 94%) occurred during the Omicron period. Failure developed in 31 patients (9.5%). Its independent predictors were older age, fewer vaccine doses, and treatment with MABs. Rate of failure was lower in the Omicron versus the pre-Omicron period (7.8% versus 36.8%, p < 0.001). During the Omicron period, predictors of failure were age, fewer vaccine doses and diagnosis of acute myeloid leukaemia/myelodysplastic syndrome (AML/MDS). Independent predictors of longer viral shedding were age, comorbidities, hospital admission at diagnosis, NHL/CLL, treatment with MABs. COVID-19-associated mortality was 3.4% (n = 11). The mortality in those who developed severe COVID-19 after early treatment was 26% in the Omicron period. Patients with HM had a significant risk of failure of early treatment, even during the Omicron period, with high mortality rate.

Paxlovid (Nirmatrelvir/Ritonavir): A new approach to Covid-19 therapy?

Despite the need for novel, effective therapeutics for the COVID-19 pandemic, no curative regimen is yet available, therefore patients are forced to rely on supportive and nonspecific therapies. Some SARS-CoV-2 proteins, like the 3C-like protease (3CLpro) or the major protease (Mpro), have been identified as promising targets for antiviral drugs. The Mpro has major a role in protein processing as well as pathogenesis of the virus, and could be a useful therapeutic target. The antiviral drug nirmatrelvir can keep SARS-CoV-2 from replicating through inhibiting Mpro. Nirmatrelvir was combined with another HIV protease inhibitor, ritonavir, to create Paxlovid (Nirmatrelvir/Ritonavir). The metabolizing enzyme cytochrome P450 3 A is inhibited by ritonavir to lengthen the half-life of nirmatrelvir, so rintonavir acts as a pharmacological enhancer. Nirmatrelvir exhibits potent antiviral activity against current coronavirus variants, despite significant alterations in the SARS-CoV-2 viral genome. Nevertheless, there are still several unanswered questions. This review summarizes the current literature on nirmatrelvir and ritonavir efficacy in treating SARS-CoV-2 infection, and also their safety and possible side effects.

Nirmatrelvir and COVID-19: development, pharmacokinetics, clinical efficacy, resistance, relapse, and pharmacoeconomics

Nirmatrelvir/ritonavir (N/R) is one of the most effective antiviral drugs against SARS-CoV-2. The preclinical development, pharmacodynamics and pharmacokinetics of N/R are reviewed herein. Randomized clinical trials have been conducted exclusively with pre-Omicron variants of concern, but in vitro studies show that efficacy against all Omicron sublineages is preserved, as confirmed by post-marketing observational studies. Nevertheless, investigations of large viral genome repositories have shown that mutation in the main protease causing resistance to N/R are increasingly frequent. In addition, virological and clinical rebounds after N/R discontinuation have been reported in immunocompetent patients. This finding is of concern when translated to immunocompromised patients, in whom N/R efficacy has not been formally investigated in clinical trials. Economical sustainability and perspectives for this therapeutic arena are discussed.

Nirmatrelvir-ritonavir treatment of COVID-19 in a high-risk patient population: A retrospective observational study

Background

Coronavirus disease 2019 (COVID-19) is a highly contagious, airborne viral infection that can infect anyone. Those with certain underlying conditions may be at higher risk for infection to develop into a severe disease requiring hospitalization. This report summarizes use of nirmatrelvir-ritonavir for the treatment of COVID-19 in high-risk patients at a single academic medical center through a pharmacist delegation protocol and demonstrates real-world efficacy and safety of treatment.

Methods

This retrospective, single-center, observational study analyzed all patients who received nirmatrelvir-ritonavir ordered by a clinical pharmacist for treatment of COVID-19 infection. The primary outcomes were safety and efficacy of nirmatrelvir-ritonavir. Safety was evaluated by analyzing drug interaction management and adverse events. Efficacy was evaluated through hospitalization and death within 28 days of nirmatrelvir-ritonavir use.

Results

Sixty patients were eligible for inclusion. No patients were hospitalized or died within 28 days after initiation of nirmatrelvir-ritonavir. Pharmacists identified 101 drug interactions with 60% considered clinically significant, requiring modification of home medications. Adverse outcomes associated with the use of nirmatrelvir-ritonavir were reported in 13 patients (21.7%).

Conclusions

A comprehensive program to mitigate drug interactions and prescribe nirmatrelvir-ritonavir ensured timely access to COVID-19 therapy, which may be associated with the prevention of hospitalization and death.