Oral #Nirmatrelvir – Ritonavir for #Covid19 in Higher-Risk #Outpatients

 

Abstract

Background

Nirmatrelvir–ritonavir has been shown to reduce progression to severe illness from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in unvaccinated high-risk outpatients. The effectiveness of nirmatrelvir–ritonavir in persons who have been vaccinated, infected naturally, or both is unclear.

Methods

In two open-label platform trials (PANORAMIC in the United Kingdom and CanTreatCOVID in Canada), we enrolled higher-risk adults (≥50 years of age or ≥18 years of age with coexisting conditions) in the community who tested positive for SARS-CoV-2 and had been unwell for 5 days or less. The participants were randomly assigned to receive usual care plus nirmatrelvir (300 mg)–ritonavir (100 mg) twice a day for 5 days or to receive usual care alone. The primary outcome was hospitalization or death from any cause within 28 days after randomization.

Results

From December 8, 2021, to September 30, 2024, a total of 3516 participants in the PANORAMIC trial and 716 participants in the CanTreatCOVID trial underwent randomization. In the PANORAMIC trial, 14 of 1698 participants (0.8%) in the nirmatrelvir–ritonavir group and 11 of 1673 participants (0.7%) in the usual-care group were hospitalized or died (adjusted odds ratio, 1.18; 95% Bayesian credible interval, 0.55 to 2.62; probability of superiority, 0.334). In the CanTreatCOVID trial, 2 of 343 participants (0.6%) in the nirmatrelvir–ritonavir group and 4 of 324 participants (1.2%) in the usual-care group were hospitalized or died (adjusted odds ratio, 0.48; 95% Bayesian credible interval, 0.08 to 2.23; probability of superiority, 0.830). In a substudy involving 634 participants, viral load was reduced by the end of treatment with nirmatrelvir–ritonavir. Serious adverse events with nirmatrelvir–ritonavir were reported in 9 participants in the PANORAMIC trial and in 4 participants in the CanTreatCOVID trial.

Conclusions

In two open-label trials, nirmatrelvir–ritonavir did not reduce the incidence of hospitalization or death among vaccinated higher-risk participants with SARS-CoV-2 infection. (Funded by the National Institute for Health and Care Research, and others; PANORAMIC ISRCTN number, 2021-005748-31; CanTreatCOVID ClinicalTrials.gov number, NCT05614349.)

Source: 

Link: https://www.nejm.org/doi/full/10.1056/NEJMoa2502457?query=TOC

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Next-generation #inhibitors of #SARS-CoV-2 #Mpro overcome the deficiencies of #Paxlovid

 

Abstract

It remains elusive to design peptidomimetic inhibitors of SARS-CoV-2 main protease (Mpro) refractory to multiple deficiencies of Paxlovid (ritonavir-boosted nirmatrelvir), pertaining mainly to E166X mutations-conferred drug resistance and inherent pharmacokinetic limitations to nirmatrelvir. We identify via virtual screening an iso-quinoline P1 moiety in place of the traditional γ-lactam and design iso-quinoline-containing inhibitors with high affinity for Mpro and its nirmatrelvir-resistant E166X mutants. Further optimization at P4 cultivates distinctive peptidomimetic inhibitors with drastically improved pharmacokinetic properties and significantly enhanced antiviral efficacy independent of ritonavir. Two such inhibitors, FD3-32 and FD3-36, also potent against SARS-CoV-1 and MERS-CoV Mpro, are more effective as a monotherapy regimen than Paxlovid in reducing viral loads in vivo and protecting infected male mice from acute lung injury. Here, we report the discovery of next-generation SARS-CoV-2 Mpro inhibitors that overcome the deficiencies of Paxlovid, promising efficacious antivirals critical for mitigating the current and future pandemics of coronaviruses.

Source: 

Link: https://www.nature.com/articles/s41467-026-71436-6

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Effectiveness of #nirmatrelvir/ritonavir and #molnupiravir in reducing the #risk of short-term and long-term #cardiovascular complications of #COVID19: a target trial emulation study

 

Abstract

While treatment with nirmatrelvir/ritonavir or molnupiravir is effective in lowering the rate of severe COVID-19, the effectiveness of these antivirals in reducing the risk of cardiovascular outcomes, especially among the hospitalized population, remains largely unknown. In this study, we assessed the real-world effectiveness of nirmatrelvir/ritonavir and molnupiravir on short- and long-term cardiovascular complications of COVID-19 using a target trial emulation design. Two target trials of COVID-19 antivirals were emulated by using a territory-wide, population-based, retrospective cohort of hospitalized patients in Hong Kong. Nine cardiovascular outcomes were evaluated in both short-term (day 0–21) and long-term (day 22–365) post-SARS-CoV-2 infection. Compared with the control group, the use of nirmatrelvir/ritonavir was associated with a significantly lower one-year risk of cardiovascular mortality, composite cardiovascular complications, major adverse cardiac events, cerebrovascular disorders, dysrhythmia, ischemic heart disease, and other cardiac disorders following infection. Molnupiravir use was associated with a short-term risk reduction in cardiovascular complications, but only a marginal risk reduction in long-term cardiovascular mortality among other complications. This study demonstrated the effectiveness of nirmatrelvir/ritonavir in reducing the risks of short- and long-term cardiovascular complications following a SARS-CoV-2 infection among the hospitalized population. Our findings suggested health-related benefits of prescribing nirmatrelvir/ritonavir over molnupiravir against severe cardiovascular post-acute sequelae of COVID-19 in the long term.

Source: 

Link: https://www.nature.com/articles/s41467-025-67776-4

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#Antiviral efficacy of oral #ensitrelvir versus oral ritonavir-boosted #nirmatrelvir in #COVID19 (PLATCOV): an open-label, phase 2, randomised, controlled, adaptive trial

 

Summary

Background

Ensitrelvir is an oral antiviral treatment for COVID-19 with the same molecular target (the main protease) as ritonavir-boosted nirmatrelvir—the current oral first-line treatment. We aimed to compare the clinical antiviral effects of the two drugs.

Methods

In an open-label, phase 2, randomised, controlled, adaptive pharmacometric platform trial, low-risk adult outpatients aged 18–60 years with early symptomatic COVID-19 (<4 days of symptoms) were recruited from hospital acute respiratory infection clinics in Thailand and Laos. Patients were randomly assigned in blocks (block sizes depended on the number of interventions available) to one of eight treatment groups, including oral ensitrelvir and oral ritonavir-boosted nirmatrelvir at standard doses, both given for 5 days, and no study drug. The primary endpoint was the oropharyngeal SARS-CoV-2 viral clearance rate assessed between day 0 and day 5 in the modified intention-to-treat population (defined as patients with at least 2 days of follow-up). Patients had four oropharyngeal swabs taken on day 0 and two swabs taken daily from days 1 to 7, then on days 10 and 14. Viral clearance rates were derived under a Bayesian hierarchical linear model fitted to log10 viral densities in standardised paired oropharyngeal swab eluates taken daily over the 5 days (14 samples). An individual patient data meta-analysis of all small molecule drugs evaluated in this platform trial using published results was also performed, adjusting for temporal trends in viral clearance. This trial is registered at ClinicalTrials.gov, NCT05041907.

Findings

Between March 17, 2023, and April 21, 2024, 604 of 903 patients enrolled were concurrently assigned to the three treatment groups (ensitrelvir n=202; ritonavir-boosted nirmatrelvir n=207; no study drug n=195). Median estimated SARS-CoV-2 clearance half-lives were 5·9 h (IQR 4·0–8·6) with ensitrelvir, 5·2 h (3·8–6·6) with nirmatrelvir, and 11·6 h (8·1–14·5) with no study drug. Viral clearance following ensitrelvir was 82% faster (95% credible interval 61–104) than no study drug and 16% slower (5–25) than ritonavir-boosted nirmatrelvir. In the meta-analysis of all unblinded small molecule drugs evaluated in the platform trial, nirmatrelvir and ensitrelvir had the largest antiviral effects (1157 patients). Viral rebound occurred in 15 (7%) of 207 patients in the nirmatrelvir group and 10 (5%) of 202 in the ensitrelvir group (p=0·45).

Interpretation

Both ensitrelvir and nirmatrelvir accelerate oropharyngeal SARS-CoV-2 viral clearance. Ensitrelvir is an effective alternative to currently available antivirals in treating COVID-19. Although COVID-19 is now generally a mild disease, it still causes substantial morbidity, particularly in vulnerable groups, and new variants or other coronaviruses could still emerge with pandemic potential. Safe effective and affordable antivirals are needed, and these are best assessed initially in pharmacometric platform trials assessing viral clearance.

Funding

Wellcome Trust through the COVID-19 Therapeutics Accelerator.

Source: The Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00482-7/fulltext?rss=yes

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#Placental transfer of #medications to treat #COVID19, #molnupiravir, #favipiravir and #nirmatrelvir/ritonavir, in the ex vivo human cotyledon model

 

Abstract

Objectives

There have been few studies in pregnant women of medications that are used to reduce severe complications from COVID-19 infection. Currently, nirmatrelvir/ritonavir (Paxlovid) is recommended by the National Institutes for Health to treat non-hospitalized pregnant patients with mild-to-moderate COVID-19 illness. The aim of this study was to determine the transplacental passage of molnupiravir, nirmatrelvir/ritonavir and favipiravir utilizing an ex vivo placental perfusion model.

Methods

Human placental cotyledons were continuously perfused in a double open circuit. The study molecules and antipyrine, a marker of placental viability, were dissolved in the maternal solution. The experiment was conducted over 90 minutes, and every 5 minutes, samples of the maternal solution and fetal exchange solutions were collected for analysis. We calculated the concentrations of study molecules, fetal transfer ratios and the clearance indexes to determine placental transfer.

Results

Of 18 placentas analysed, 14 were validated by antipyrine transfer. Nirmatrelvir alone had low placental transfer, with a fetal transfer ratio of 0.025. Its placenta transfer increased in the presence of ritonavir, with a fetal transfer ratio of 0.06. The molnupiravir metabolite, β-D-N-4-hydroxycytidine (EIDD 1931), showed low placental transfer, with an average fetal transfer ratio of 0.04. By contrast, favipiravir crossed the placenta with an average fetal transfer ratio of 0.425.

Conclusions

Placental transfer was high for the nucleoside analogue favipiravir, while it was low for molnupiravir and low for the protease inhibitor nirmatrelvir but increased by ritonavir. Clinical data are required to confirm the placental transfer and determine the safety of COVID antivirals in pregnancy.

Source: Journal of Antimicrobial Chemotherapy, https://academic.oup.com/jac/advance-article-abstract/doi/10.1093/jac/dkaf302/8245204?redirectedFrom=fulltext

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#SARS-CoV-2 #rebound and post-acute #mortality and hospitalization among patients admitted with #COVID19: cohort study

Abstract

Recent investigations have demonstrated a relationship between the persistence of SARS-CoV-2 and post-COVID-19 conditions. Building upon a potential connection between SARS-CoV-2 persistence and early virologic rebound, we examine the association of early virologic rebound with post-acute mortality and hospitalization due to post-acute sequelae among hospitalized patients with COVID-19 in Hong Kong. Our study includes 13,859, 3959, and 4502 patients in the all-patient, nirmatrelvir/ritonavir, and molnupiravir group, respectively. Results show that patients who experienced virologic rebound exhibited a significantly higher risk of post-acute mortality (hazard ratio [HR], 1.52; 95% confidence interval [CI], 1.36–1.70) with a risk difference [RD] of 7.19%, compared with patients without virologic rebound. A similar increase in the risk of post-acute mortality is also observed in nirmatrelvir/ritonavir-treated patients (HR, 1.78; 95% CI, 1.41–2.25; RD, 12.55%) and molnupiravir-treated patients (HR, 1.47; 95% CI, 1.18–1.82; RD, 4.90%). The virologic rebound may thus serve as an early marker for post-COVID-19 condition, enabling healthcare officials to monitor and provide timely intervention for long COVID.

Source: Nature Communications, https://www.nature.com/articles/s41467-025-61737-7

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Extended #nirmatrelvir–ritonavir #treatment durations for immunocompromised #patients with #COVID19 (EPIC-IC): a placebo-controlled, randomised, double-blind, phase 2 trial

Summary

Background

Nirmatrelvir–ritonavir is approved for adults with mild-to-moderate COVID-19 who are at risk of severe disease. There are little clinical data to guide the duration of therapy in patients who are immunocompromised. We aimed to compare the approved 5-day regimen of nirmatrelvir–ritonavir with 10-day and 15-day regimens.

Methods

This placebo-controlled, randomised, double-blind, phase 2 trial enrolled non-hospitalised, immunocompromised individuals aged 12 years or older with symptomatic COVID-19 from 73 sites across nine countries. Participants were randomly assigned (1:1:1) to receive 300 mg nirmatrelvir and 100 mg ritonavir orally twice per day for 5, 10, or 15 days. Randomisation was stratified according to whether participants were considered immunocompromised due to use of corticosteroids or tumour necrosis factor blockers. Investigators, participants, and caregivers were masked to the assigned study group. The primary endpoint was proportion of randomly assigned and dosed participants with sustained nasopharyngeal SARS-CoV-2 RNA concentrations below the lower limit of quantification (2·0 log10 copies per mL) from days 15 to 44. Secondary endpoints included the incidence of viral rebound after the end of treatment up to day 44. Safety, a secondary endpoint, was assessed in all randomly assigned participants who received at least one dose of nirmatrelvir–ritonavir. This trial was registered with ClinicalTrials.gov (NCT05438602) and is completed.

Findings

Among 156 participants (84 female, 72 male) randomly assigned from Aug 3, 2022 to July 17, 2023, 150 comprised the analysis population. The primary endpoint was reached in 32 (61·5%, 95% CI 48·3–74·8) of 52 participants in the 5-day treatment group, 34 (70·8%, 58·0–83·7) of 48 participants in the 10-day treatment group, and 33 (66·0%, 52·9–79·1) of 50 participants in the 15-day treatment group. Viral rebound occurred in 17·3% (95% CI 8·2–30·3) of participants in the 5-day group, 2·1% (0·1–11·1) in the 10-day group, and 2·0% (0·1–10·6) in the 15-day group. Adverse events occurred in 28 (52·8%) of 53, 34 (66·7%) of 51, and 31 (60·8%) of 51 participants across the 5-day, 10-day, and 15-day groups, respectively. Two COVID-19-related hospitalisations were reported, both in the 5-day treatment group.

Interpretation

No difference was observed between the three treatment durations in the primary endpoint. Extending nirmatrelvir–ritonavir treatment beyond 5 days resulted in a nominal improvement in the frequency of viral rebound and was generally well tolerated.

Funding

Pfizer.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00221-X/fulltext?rss=yes

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#Molnupiravir or #nirmatrelvir–ritonavir plus usual care vs usual care alone in patients admitted to #hospital with #COVID19 (RECOVERY)...

Summary

Background

Molnupiravir and nirmatrelvir–ritonavir are oral antivirals that have shown efficacy in preventing disease progression in outpatients with COVID-19. We aimed to evaluate these treatments for patients hospitalised with COVID-19 pneumonia, for whom data on these antivirals are scarce.

Methods

The RECOVERY trial is a randomised, controlled, open-label, adaptive platform trial testing treatments for COVID-19. In this study we report the molnupiravir and nirmatrelvir–ritonavir comparisons from the RECOVERY trial. In each comparison, participants aged 18 years and older were randomly allocated (1:1) to the relevant antiviral (5 days of molnupiravir 800 mg twice daily or 300 mg nirmatrelvir and 100 mg ritonavir twice daily) in addition to usual care, or to usual care alone. The molnupiravir comparison was conducted at 75 hospitals in the UK, two in Nepal, and two in Indonesia; the nirmatrelvir–ritonavir comparison was conducted at 32 hospitals in the UK. Participants could take part in both comparisons. The primary outcome was 28-day mortality, and secondary outcomes were time to discharge alive from hospital and progression to invasive ventilation or death. Analysis was by intention to treat. Both comparisons were stopped because of low recruitment. This study is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.

Findings

From Jan 24, 2022, to May 24, 2023, 923 participants were recruited to the molnupiravir comparison (445 allocated to molnupiravir and 478 to usual care), and from March 31, 2022, to May 24, 2023, 137 participants were recruited to the nirmatrelvir–ritonavir comparison (68 allocated to nirmatrelvir–ritonavir and 69 to usual care). More than three-quarters of participants were vaccinated and had antispike antibodies at randomisation, and more than two-thirds were receiving other SARS-CoV-2 antivirals. In the molnupiravir comparison, 74 (17%) participants allocated to molnupiravir and 79 (17%) allocated to usual care died within 28 days (hazard ratio [HR] 0·93 [95% CI 0·68–1·28], p=0·66). In the nirmatrelvir–ritonavir comparison, 13 (19%) participants allocated to nirmatrelvir–ritonavir and 13 (19%) allocated to usual care died within 28 days (HR 1·02 [0·47–2·23], p=0·96). In neither comparison was there evidence of any difference in the duration of hospitalisation or the proportion of participants progressing to invasive ventilation or death.

Interpretation

Adding molnupiravir or nirmatrelvir–ritonavir to usual care was not associated with improvements in clinical outcomes. However, low recruitment meant a clinically meaningful benefit of treatment could not be ruled out, particularly for nirmatrelvir–ritonavir.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00093-3/fulltext?rss=yes

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#Nirmatrelvir–ritonavir versus placebo–ritonavir in individuals with #longCOVID in the #USA (PAX LC): a double-blind, randomised, placebo-controlled, phase 2, decentralised trial

Summary

Background

The substantial burden of post-COVID-19 condition (also known as long COVID) underscores the need for effective pharmacological interventions. Given that viral persistence has been hypothesised as a potential cause of long COVID, antiviral therapy might offer a promising approach to alleviating long COVID symptoms. We therefore investigated the efficacy, safety, and tolerability of nirmatrelvir–ritonavir for treating long COVID.

Methods

In this phase 2, decentralised, double-blind, randomised controlled trial, adults (aged ≥18 years) from the 48 states across the contiguous USA, with previous documented SARS-CoV-2 infection and long COVID symptoms starting within 4 weeks of initial infection and persisting for at least 12 weeks, were eligible for inclusion. Key exclusion criteria were use of nirmatrelvir–ritonavir within the previous 2 months, CYP3A4-dependent medications, or strong CYP3A4 inducers; acute medical illness such as SARS-CoV-2 infection within the past 2 weeks; active liver disease; renal impairment; and immunocompromise. Using software for 1:1 stratified block random assignment, participants were randomly allocated to receive either two tablets of nirmatrelvir (150 mg each) and one tablet of ritonavir (100 mg), or placebo and one tablet of ritonavir (100 mg), orally administered twice daily for 15 days, stratified by age, sex at birth, and COVID-19 vaccination status. Participants, clinicians, and the study team were masked to treatment allocation. The primary efficacy endpoint was the change in the Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Physical Health Summary Score (PHSS) from baseline to day 28, analysed by intention to treat. Safety endpoints were reported from baseline to week 6 in all participants who were exposed to the study treatment. This trial is registered with ClinicalTrials.gov (NCT05668091) and is now closed to new participants.

Findings

Between April 14, 2023, and Feb 26, 2024, 119 participants were screened. 100 were enrolled (66 [66%] female participants and 34 [34%] male participants), with 49 assigned to the nirmatrelvir–ritonavir group and 51 to the placebo–ritonavir group (intention-to-treat population). Three participants in the nirmatrelvir–ritonavir group and two in the placebo–ritonavir group withdrew before starting treatment and were excluded from the safety population. The mean PROMIS-29 PHSS at baseline was 39·6 (95% CI 37·4 to 41·9) in the nirmatrelvir–ritonavir group and 36·3 (34·4 to 38·2) in the placebo–ritonavir group. The adjusted change from baseline to day 28 was 0·45 (–0·93 to 1·83) in the nirmatrelvir–ritonavir group and 1·01 (–0·30 to 2·31) in the placebo–ritonavir group (adjusted mean difference –0·55 [95% CI –2·32 to 1·21; p=0·54]). No deaths or serious adverse events were recorded between baseline and week 6. Study drug-related treatment-emergent adverse events were reported in more participants in the nirmatrelvir–ritonavir group (35 [76%] of 46) compared with the placebo–ritonavir group (27 [55%] of 49), mostly driven by dysgeusia. Early treatment termination due to an adverse event occurred in two participants in the nirmatrelvir–ritonavir group and one in the placebo–ritonavir group.

Interpretation

Nirmatrelvir–ritonavir administered for 15 days did not significantly improve health outcomes in participants with long COVID compared with placebo–ritonavir at day 28. However, the study showed the feasibility of large-scale, decentralised trials in long COVID.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00073-8/fulltext?rss=yes

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Modeling suggests #SARS-CoV-2 #rebound after #nirmatrelvir-ritonavir #treatment is driven by target cell preservation coupled with incomplete viral clearance

ABSTRACT

In a subset of SARS-CoV-2-infected individuals treated with the antiviral nirmatrelvir-ritonavir, the virus rebounds following treatment. The mechanisms driving this rebound are not well understood. We used a mathematical model to describe the longitudinal viral load dynamics of 51 individuals treated with nirmatrelvir-ritonavir, 20 of whom rebounded. Target cell preservation, either by a robust innate immune response or initiation of N-R near the time of symptom onset, coupled with incomplete viral clearance, appears to be the main factor leading to viral rebound. Moreover, the occurrence of viral rebound is likely influenced by the time of treatment initiation relative to the progression of the infection, with earlier treatments leading to a higher chance of rebound. A comparison with an untreated cohort suggests that early treatments with nirmatrelvir-ritonavir may be associated with a delay in the onset of an adaptive immune response. Nevertheless, our model demonstrates that extending the course of nirmatrelvir-ritonavir treatment to a 10-day regimen may greatly diminish the chance of rebound in people with mild-to-moderate COVID-19 and who are at high risk of progression to severe disease. Altogether, our results suggest that in some individuals, a standard 5-day course of nirmatrelvir-ritonavir starting around the time of symptom onset may not completely eliminate the virus. Thus, after treatment ends, the virus can rebound if an effective adaptive immune response has not fully developed. These findings on the role of target cell preservation and incomplete viral clearance also offer a possible explanation for viral rebounds following other antiviral treatments for SARS-CoV-2.

Source: Journal of Virology, https://journals.asm.org/doi/full/10.1128/jvi.01623-24?af=R

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Distal #protein-protein #interactions contribute to #nirmatrelvir #resistance

Abstract

SARS-CoV-2 main protease, Mpro, is responsible for processing the viral polyproteins into individual proteins, including the protease itself. Mpro is a key target of anti-COVID-19 therapeutics such as nirmatrelvir (the active component of Paxlovid). Resistance mutants identified clinically and in viral passage assays contain a combination of active site mutations (e.g., E166V, E166A, L167F), which reduce inhibitor binding and enzymatic activity, and non-active site mutations (e.g., P252L, T21I, L50F), which restore the fitness of viral replication. To probe the role of the non-active site mutations in fitness rescue, here we use an Mpro triple mutant (L50F/E166A/L167F) that confers nirmatrelvir drug resistance with a viral fitness level similar to the wild-type. By comparing peptide and full-length Mpro protein as substrates, we demonstrate that the binding of Mpro substrate involves more than residues in the active site. Particularly, L50F and other non-active site mutations can enhance the Mpro dimer-dimer interactions and help place the nsp5-6 substrate at the enzyme catalytic center. The structural and enzymatic activity data of Mpro L50F, L50F/E166A/L167F, and others underscore the importance of considering the whole substrate protein in studying Mpro and substrate interactions, and offers important insights into Mpro function, resistance development, and inhibitor design.

Source: Nature Communications, https://www.nature.com/articles/s41467-025-56651-x

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