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Oral outpatient treatment for Covid-19 is needed. In this phase 3, double-blind, randomized, controlled trial, molnupiravir, a small-molecule antiviral, was studied in unvaccinated patients with less than 5 days of Covid-19 illness. By day 29, hospitalization for progression of Covid-19 was lower with molnupiravir (6.8%) than with placebo (9.7%).

Molnupiravir, an antiviral medication widely used against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), acts by inducing mutations in the virus genome during replication. Most random mutations are likely to be deleterious to the virus and many will be lethal; thus, molnupiravir-induced elevated mutation rates reduce viral load 1 , 2 . However, if some patients treated with molnupiravir do not fully clear the SARS-CoV-2 infections, there could be the potential for onward transmission of molnupiravir-mutated viruses. Here we show that SARS-CoV-2 sequencing databases contain extensive evidence of molnupiravir mutagenesis. Using a systematic approach, we find that a specific class of long phylogenetic branches, distinguished by a high proportion of G-to-A and C-to-T mutations, are found almost exclusively in sequences from 2022, after the introduction of molnupiravir treatment, and in countries and age groups with widespread use of the drug. We identify a mutational spectrum, with preferred nucleotide contexts, from viruses in patients known to have been treated with molnupiravir and show that its signature matches that seen in these long branches, in some cases with onward transmission of molnupiravir-derived lineages. Finally, we analyse treatment records to confirm a direct association between these high G-to-A branches and the use of molnupiravir. A specific class of long phylogenetic branches, distinguished by a high proportion of G-to-A and C-to-T mutations, are almost exclusively found in sequences from 2022, after molnupiravir treatment was introduced, indicating that molnupiravir treatment can give rise to viable mutagenized viruses.

Molnupiravir, a wide-spectrum antiviral that is currently in phase 2/3 clinical trials for the treatment of COVID-19, is proposed to inhibit viral replication by a mechanism known as ‘lethal mutagenesis’. Two recently published studies reveal the biochemical and structural bases of how molnupiravir disrupts the fidelity of SARS-CoV-2 genome replication and prevents viral propagation by fostering error accumulation in a process referred to as ‘error catastrophe’.

Despite dire warnings, a stockpile of ready compounds to fight viral pandemics was sorely lacking. Can drugmakers finally do the right thing? Despite dire warnings, a stockpile of ready compounds to fight viral pandemics was sorely lacking. Can drugmakers finally do the right thing?

Molnupiravir (Lagevrio ® ) is an orally-administered antiviral prodrug that inhibits replication of RNA viruses through viral error induction. It is being developed by Merck and Ridgeback Biotherapeutics for the prevention and treatment of Coronavirus disease 2019 (COVID-19). Molnupiravir received its first approval on 4 November 2021 in the UK for the treatment of mild to moderate COVID-19 in adults with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic test and who have at least one risk factor for developing severe illness. Molnupiravir is filed for approval and has emergency use authorization for the treatment of COVID-19 in several countries, including the USA, Japan and those in the EU. This article summarizes the milestones in the development of molnupiravir leading to this first approval for COVID-19.

All coronaviruses known to have recently emerged as human pathogens probably originated in bats 1 . Here we use a single experimental platform based on immunodeficient mice implanted with human lung tissue (hereafter, human lung-only mice (LoM)) to demonstrate the efficient in vivo replication of severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as well as two endogenous SARS-like bat coronaviruses that show potential for emergence as human pathogens. Virus replication in this model occurs in bona fide human lung tissue and does not require any type of adaptation of the virus or the host. Our results indicate that bats contain endogenous coronaviruses that are capable of direct transmission to humans. Our detailed analysis of in vivo infection with SARS-CoV-2 in human lung tissue from LoM showed a predominant infection of human lung epithelial cells, including type-2 pneumocytes that are present in alveoli and ciliated airway cells. Acute infection with SARS-CoV-2 was highly cytopathic and induced a robust and sustained type-I interferon and inflammatory cytokine and chemokine response. Finally, we evaluated a therapeutic and pre-exposure prophylaxis strategy for SARS-CoV-2 infection. Our results show that therapeutic and prophylactic administration of EIDD-2801—an oral broad-spectrum antiviral agent that is currently in phase II/III clinical trials—markedly inhibited SARS-CoV-2 replication in vivo, and thus has considerable potential for the prevention and treatment of COVID-19. Human and bat coronaviruses replicate efficiently in immunodeficient mice implanted with human lung tissue, and treatment or prophylaxis using EIDD-2801 in this model suggests that this oral antiviral agent may be effective in preventing COVID-19.

The first crop of antivirals against SARS-CoV-2 is promising. But new drugs will be needed to counter the looming threat of resistance. The first crop of antivirals against SARS-CoV-2 is promising. But new drugs will be needed to counter the looming threat of resistance.

Two years into the pandemic, the COVID-19 drugs pipeline is primed to pump out novel treatments — and fresh uses for familiar therapies. Two years into the pandemic, the COVID-19 drugs pipeline is primed to pump out novel treatments — and fresh uses for familiar therapies.

Amyotrophic lateral sclerosis is a progressive neurodegenerative disorder leading to muscle weakness and respiratory failure. Arimoclomol, a heat-shock protein-70 (HSP70) co-inducer, is neuroprotective in animal models of amyotrophic lateral sclerosis, with multiple mechanisms of action, including clearance of protein aggregates, a pathological hallmark of sporadic and familial amyotrophic lateral sclerosis. We aimed to evaluate the safety and efficacy of arimoclomol in patients with amyotrophic lateral sclerosis. ORARIALS-01 was a multinational, randomised, double-blind, placebo-controlled, parallel-group trial done at 29 centres in 12 countries in Europe and North America. Patients were eligible if they were aged 18 years or older and met El Escorial criteria for clinically possible, probable, probable laboratory-supported, definite, or familial amyotrophic lateral sclerosis; had an ALS Functional Rating Scale-Revised score of 35 or more; and had slow vital capacity at 70% or more of the value predicted on the basis of the participant's age, height, and sex. Patients were randomly assigned (2:1) in blocks of 6, stratified by use of a stable dose of riluzole or no riluzole use, to receive oral arimoclomol citrate 1200 mg/day (400 mg three times per day) or placebo. The Randomisation sequence was computer generated centrally. Investigators, study personnel, and study participants were masked to treatment allocation. The primary outcome was the Combined Assessment of Function and Survival (CAFS) rank score over 76 weeks of treatment. The primary outcome and safety were analysed in the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT03491462, and is completed. Between July 31, 2018, and July 17, 2019, 287 patients were screened, 245 of whom were enrolled in the trial and randomly assigned. The modified intention-to-treat population comprised 239 patients (160 in the arimoclomol group and 79 in the placebo group): 151 (63%) were male and 88 (37%) were female; mean age was 57·6 years (SD 10·9). CAFS score over 76 weeks did not differ between groups (mean 0·51 [SD 0·29] in the arimoclomol group vs 0·49 [0·28] in the placebo group; p=0·62). Cliff's delta comparing the two groups was 0·039 (95% CI –0·116 to 0·194). Proportions of participants who died were similar between the treatment groups: 29 (18%) of 160 patients in the arimoclomol group and 18 (23%) of 79 patients in the placebo group. Most deaths were due to disease progression. The most common adverse events were gastrointestinal. Adverse events were more often deemed treatment-related in the arimoclomol group (104 [65%]) than in the placebo group (41 [52%]) and more often led to treatment discontinuation in the arimoclomol group (26 [16%]) than in the placebo group (four [5%]). Arimoclomol did not improve efficacy outcomes compared with placebo. Although available biomarker data are insufficient to preclude future strategies that target the HSP response, safety data suggest that a higher dose of arimoclomol would not have been tolerated. Orphazyme.

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. 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. 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. 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. UK Research and Innovation (UK Medical Research Council), the National Institute for Health and Care Research, and the Wellcome Trust.