Clinical rebound after treatment with nirmatrelvir/ritonavir in COVID-19.

BACKGROUND: Nirmatrelvir/ritonavir (NM/r) is a safe and effective oral antiviral therapeutic used for treatment of mild-to-moderate COVID-19. Case reports described a clinical rebound syndrome whereby individuals experience a relapse of symptoms shortly after completing successful treatment. There is a lack of information on frequency of COVID-19 rebound after NM/r in routine clinical care, contributing factors, and clinical outcomes. METHODS: We reviewed electronic medical records to verify COVID-19 diagnosis, symptoms, and treatment with NM/r from January-June 2022. We defined COVID-19 clinical rebound as clear improvement in symptoms followed by recurrence or worsening of symptoms within 30 days of a five-day course of NM/r. RESULTS: We studied 268 adults with median age 57 (IQR 47, 68), 80% White race, 85% non-Hispanic ethnicity, 55% female, 80% vaccinated and boosted against SARS-CoV-2, and 68% with any co-morbidity. Sixteen (6.0%) of studied patients were determined to have COVID-19 clinical rebound. The median time from starting NM/r to rebound was 11 days (IQR 9, 13). Notable demographic and clinical factors with higher proportion (not statistically significant) among COVID-19 rebound patients were female sex (75% rebound vs. 54.5% no rebound), Black race (12.5% rebound vs. 4.9% no rebound), presence of at least one co-morbidity (81.3% rebound vs. 67.5% no rebound), and lack of prior SARS-CoV-2 infection (100% rebound vs. 92.9% no rebound). Only one patient (6.25%) was hospitalized after COVID-19 rebound. CONCLUSIONS: COVID-19 clinical rebound after treatment with NM/r is mild with favorable outcomes and more common than previously reported from real-world clinical care studies.

Nirmatrelvir/ritonavir treatment and the risk of post-COVID condition over 180 days in Malaysia.

BACKGROUND: The effect of nirmatrelvir/ritonavir on preventing post-COVID condition (PCC) in the BA4, BA5, and XBB Omicron predominant periods is not well understood. The purpose of this study was to assess how nirmatrelvir/ritonavir treatment affected both PCC and health-related quality of life. METHODS: This retrospective cohort study enrolled 2,524 adults aged 18 years and older who were eligible for nirmatrelvir/ritonavir between July 14 to November 14, 2022. All outcomes were observed from the patient's first visit to the primary health clinic, 1 week, 1 month, 3 months, and 6 months after testing positive for COVID-19. The primary outcome was the presence of PCC. Secondary outcomes included the effects on health-related quality of life, such as walking, bathing and dressing, activities, cause adverse emotions or signs that prevent individuals from leading normal lives over a 180-day observation period. RESULTS: There were no significant differences observed between the nirmatrelvir/ritonavir and those not administered (control group) in terms of PCC symptoms at 3 months (OR 0.71 95% CI 0.31, 1.64) and 6 months (OR 1.30 95% CI 0.76, 2.21). At 3 months, the use of nirmatrelvir/ritonavir was associated with a 26% reduction in symptoms causing negative emotions (OR 0.74 95% CI 0.60, 0.92) and an increased likelihood of symptoms limiting walking (OR 1.58 95% CI 1.10, 2.27). However, there were no significant differences between the nirmatrelvir/ritonavir and the control group in terms of the impact of PCC on health-related quality of life at 6 months. CONCLUSIONS: Our study indicates that the administration of nirmatrelvir/ritonavir does not significantly reduce PCC after 3 months and 6 months in a population with high vaccination coverage.

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

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

Effective Treatment of COVID-19 Infection with Repurposed Drugs: Case Reports.

The COVID-19 pandemic response has been hindered by the absence of an efficient antiviral therapy for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The reason why the previous preventative approach to COVID-19 solely through vaccines has failed could be a lack of understanding of how quickly the SARS-CoV-2 virus evolves. Given the absence of specific treatments for the virus, efforts have been underway to explore treatment options. Drug repurposing involves identifying new therapeutic uses for approved drugs, proving to be a time-saving strategy with minimal risk of failure. In this study, we report the successful use of a multidrug approach in patients with COVID-19. Successful administration of multidrug therapy, such as combinations of hydroxychloroquine and azithromycin, doxycycline and ivermectin, or ivermectin, doxycycline, and azithromycin, has been reported. Multidrug therapy is effective because of the differing mechanisms of action of these drugs, and it may also mitigate the emergence of drug-resistant SARS-CoV-2 strains. The medicines were lopinavir/ritonavir (Kaletra), bamlanivimab (monoclonal antibody), glycopyrrolate-formoterol (Bevespi), ciclesonide (Alvesco), famotidine (Pepcid), and diphenhydramine (Benadryl).

Insights from a community-based survey on factors influencing acceptance and uptake of Paxlovid (nirmatrelvir and ritonavir) as a COVID-19 antiviral medication in Singapore.

INTRODUCTION: Antiviral treatment can reduce the burden of COVID-19. But utilisation can be suboptimal, even in a setting like Singapore where it is fully subsidized for those with selected medical conditions and older adults (≥ 50 years). We hence investigated the factors affecting awareness, acceptance, and initiative to request Paxlovid. METHODS: We assessed the Paxlovid awareness, factors impacting its uptake in a survey conducted from August 2022 to September 2022 through the SOCRATES cohort. Multivariable logistic regression was used to investigate associations between sociodemographics, perceptions, and attitudes with the key study outcomes. RESULTS: Among respondents to the Paxlovid survey, 54% were aware of Paxlovid. On being provided essential details about Paxlovid, 75% reported they would likely be receptive to taking it if prescribed, and 38% indicated the initiative to request for it if it was not suggested by their doctors. Factors associated with awareness of Paxlovid include aged 40 years old and above, higher education, citing websites as an information source, greater trust in healthcare providers (aOR: 1.65, 95% CI 1.26 - 2.15) and government communications (aOR: 0.69, 95% CI 0.55 - 0.86), and higher perceived risk of COVID-19 infection (aOR: 1.25, 95% CI 1.10 - 1.42). Factors associated with acceptance to take Paxlovid include male gender, citing trust in healthcare providers (aOR: 1.49, 95% CI 1.11 - 1.99) and government communications (aOR: 1.38, 95% CI 1.09 - 1.76), and higher perceived severity of COVID-19 (aOR: 1.23, 95% CI 1.07 - 1.42). Factors associated with initiative to request Paxlovid include male gender, having pre-existing diabetes and higher perceived severity of COVID-19 (aOR: 1.24, 95% CI 1.09 - 1.40). The most common reasons for why respondents might not take Paxlovid were concerns about side effects (64%), concerns about costs (29%), and the perception that COVID-19 is a mild (25%). CONCLUSION: The majority of our respondents would take Paxlovid if it was prescribed to them, but a much smaller proportion would have the initiative to request for this. Key factors that may influence uptake are COVID-19 threat perceptions, trust in healthcare and government, and perceptions of the drug's side effects and cost.

Efficacy of Combination of Antiviral Therapy With Neutralizing Monoclonal Antibodies for Recurrent Persistent SARS-CoV-2 Pneumonia in Patients With Lymphoma.

Despite the potential of neutralizing antibodies in the management of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), clinical research on its efficacy in Chinese patients remains limited. This study is aimed at investigating the therapeutic effect of combination of antiviral therapy with neutralizing monoclonal antibodies for recurrent persistent SARS-CoV-2 pneumonia in patients with lymphoma complicated by B cell depletion. A prospective study was conducted on Chinese patients who were treated with antiviral nirmatrelvir/ritonavir therapy and the neutralizing antibody tixagevimab-cilgavimab (tix-cil). The primary outcome was the rate of recurrent SARS-CoV-2 infection. Five patients with lymphoma experienced recurrent SARS-CoV-2 pneumonia and received tix-cil treatment. All patients had a history of CD20 monoclonal antibody use within the year preceding SARS-CoV-2 infection, and two patients also had a history of Bruton's tyrosine kinase (BTK) inhibitor use. These patients had notably low lymphocyte counts and exhibited near depletion of B cells. All five patients tested negative for serum SARS-CoV-2 IgG and IgM antibodies. None of the patients developed reinfection with SARS-CoV-2 pneumonia after antiviral and tix-cil treatment during the 6-month follow-up period. In conclusion, the administration of antiviral and SARS-CoV-2-neutralizing antibodies showed encouraging therapeutic efficacy against SARS-CoV-2 pneumonia in patients with lymphoma complicated by B cell depletion, along with the potential preventive effect of neutralizing antibodies for up to 6 months.

Novel combinatorial approach: Harnessing HIV protease inhibitors to enhance amphotericin B's antifungal efficacy in cryptococcosis.

Cryptococcosis is a fungal infection that is becoming increasingly prevalent worldwide, particularly among individuals with compromised immune systems, such as HIV patients. Amphotericin B (AmB) is the first-line treatment mainly combined with flucytosine. The scarcity and the prohibitive cost of this regimen urge the use of fluconazole as an alternative, leading to increased rates of treatment failure and relapses. Therefore, there is a critical need for efficient and cost-effective therapy to enhance the efficacy of AmB. In this study, we evaluated the efficacy of the HIV protease inhibitors (PIs) to synergize the activity of AmB in the treatment of cryptococcosis. Five PIs (ritonavir, atazanavir, saquinavir, lopinavir, and nelfinavir) were found to synergistically potentiate the killing activity of AmB against Cryptococcus strains with Æ©FICI ranging between 0.09 and 0.5 against 20 clinical isolates. This synergistic activity was further confirmed in a time-kill assay, where different AmB/PIs combinations exhibited fungicidal activity within 24 hrs. Additionally, PIs in combination with AmB exhibited an extended post-antifungal effect on treated cryptococcal cells for approximately 10 hrs compared to 4 hours with AmB alone. This promising activity against cryptococcal cells did not exhibit increased cytotoxicity towards treated kidney cells, ruling out the risk of drug combination-induced nephrotoxicity. Finally, we evaluated the efficacy of AmB/PIs combinations in the Caenorhabditis elegans model of cryptococcosis, where these combinations significantly reduced the fungal burden of the treated nematodes by approximately 2.44 Log10 CFU (92.4%) compared to the untreated worms and 1.40 Log10 ((39.4%) compared to AmB alone. The cost-effectiveness and accessibility of PIs in resource-limited geographical areas compared to other antifungal agents, such as flucytosine, make them an appealing choice for combination therapy.

Efficacy of COVID-19 Oral antivirals in hospitalised oldest-old with high morbidity burden: a target trial emulation study.

BACKGROUND: Molnupiravir and nirmatrelvir-ritonavir are orally administered pharmacotherapies for mild to moderate COVID-19. However, the effectiveness of these drugs among very old (≥80 years), hospitalised patients remains unclear, limiting the risk-benefit assessment of these antivirals in this specific group. This study investigates the effectiveness of these antivirals in reducing mortality among this group of hospitalised patients with COVID-19. METHODS: Using a territory-wide public healthcare database in Hong Kong, a target trial emulation study was conducted with data from 13 642 eligible participants for the molnupiravir trial and 9553 for the nirmatrelvir-ritonavir trial. The primary outcome was all-cause mortality. Immortal time and confounding bias was minimised using cloning-censoring-weighting approach. Mortality odds ratios were estimated by pooled logistic regression after adjusting confounding biases by stabilised inverse probability weights. RESULTS: Both molnupiravir (HR: 0.895, 95% CI: 0.826-0.970) and nirmatrelvir-ritonavir (HR: 0.804, 95% CI: 0.678-0.955) demonstrated moderate mortality risk reduction among oldest-old hospitalised patients. No significant interaction was observed between oral antiviral treatment and vaccination status. The 28-day risk of mortality was lower in initiators than non-initiators for both molnupiravir (risk difference: -1.09%, 95% CI: -2.29, 0.11) and nirmatrelvir-ritonavir (risk difference: -1.71%, 95% CI: -3.30, -0.16) trials. The effectiveness of these medications was observed regardless of the patients' prior vaccination status. CONCLUSIONS: Molnupiravir and nirmatrelvir-ritonavir are moderately effective in reducing mortality risk among hospitalised oldest-old patients with COVID-19, regardless of their vaccination status.

Population pharmacokinetics of rifabutin among HIV/TB co-infected children on lopinavir/ritonavir-based antiretroviral therapy.

In adults requiring protease inhibitor (PI)-based antiretroviral therapy (ART), replacing rifampicin with rifabutin is a preferred option, but there is lack of evidence to guide rifabutin dosing in children, especially with PIs. We aimed to characterize the population pharmacokinetics of rifabutin and 25-O-desacetyl rifabutin (des-rifabutin) in children and optimize its dose. We included children from three age cohorts: (i) <1-year-old cohort and (ii) 1- to 3-year-old cohort, who were ART naïve and received 15- to 20-mg/kg/day rifabutin for 2 weeks followed by lopinavir/ritonavir (LPV/r)-based ART with 5.0- or 2.5 mg/kg/day rifabutin, respectively, while the (iii) >3-year-old cohort was ART-experienced and received 2.5-mg/kg/day rifabutin with LPV/r-based ART. Non-linear mixed-effects modeling was used to interpret the data. Monte Carlo simulations were performed to evaluate the study doses and optimize dosing using harmonized weight bands. Twenty-eight children were included, with a median age of 10 (range 0.67-15.0) years, a median weight of 11 (range 4.5-45) kg, and a median weight-for-age z score of -3.33 (range -5.15 to -1.32). A two-compartment disposition model, scaled allometrically by weight, was developed for rifabutin and des-rifabutin. LPV/r increased rifabutin bioavailability by 158% (95% confidence interval: 93.2%-246.0%) and reduced des-rifabutin clearance by 76.6% (74.4%-78.3%). Severely underweight children showed 26% (17.9%-33.7%) lower bioavailability. Compared to adult exposures, simulations resulted in higher median steady-state rifabutin and des-rifabutin exposures in 6-20 kg during tuberculosis-only treatment with 20 mg/kg/day. During LPV/r co-treatment, the 2.5-mg/kg/day dose achieved similar exposures to adults, while the 5-mg/kg/day dose resulted in higher exposures in children >7 kg. All study doses maintained a median Cmax of <900 µg/L. The suggested weight-band dosing matches adult exposures consistently across weights and simplifies dosing.

Oral antivirals for COVID-19 among patients with cancer.

PURPOSE: Immunocompromised individuals, such as those diagnosed with cancer, are at a significantly higher risk for severe illness and mortality when infected with SARS-CoV-2 (COVID-19) than the general population. Two oral antiviral treatments are approved for COVID-19: Paxlovid® (nirmatrelvir/ritonavir) and Lagevrio® (molnupiravir). There is a paucity of data regarding the benefit from these antivirals among immunocompromised patients with cancer, and recent studies have questioned their efficacy among vaccinated patients, even those with risk factors for severe COVID-19. METHODS: We evaluated the efficacy and safety of nirmatrelvir/ritonavir and molnupiravir in preventing severe illness and death using our database of 457 patients with cancer and COVID-19 from Brown University-affiliated hospitals. RESULTS: Sixty-seven patients received nirmatrelvir/ritonavir or molnupiravir and were compared to 45 concurrent controls who received no antiviral treatment despite being eligible to receive it. Administration of nirmatrelvir/ritonavir or molnupiravir was associated with improved survival and lower 90-day all-cause and COVID-19-attributed mortality (p < 0.05) and with lower peak O2 requirements (ordinal odds ratio [OR] 1.52, 95% confidence interval [CI] 0.92-2.56). CONCLUSION: Acknowledging the small size of our sample as a limitation, we concluded that early antiviral treatment might be beneficial to immunocompromised individuals, particularly those with cancer, when infected with SARS-CoV-2. Larger-scale, well-stratified studies are needed in this patient population.

Effectiveness of the antiviral medications azvudine and nirmatrelvir-ritonavir in treating COVID-19 in patients with hematological malignancies.

BACKGROUND: Patients with Hematological Malignancies (HM) are at a high risk of mortality from Coronavirus disease 2019 (COVID-19). The available antivirals were different between China and other countries. In China, azvudine was obtained for emergency use to treat adult COVID-19 patients with moderate symptoms in July 2022. While nirmatrelvir-ritonavir was well-known and used in many countries. The purpose of the present study was to assess whether there was any difference in the efficacy and safety of the two drugs. METHODS: This study was a prospective observational study of patients with HM who developed COVID-19. Patients were divided into three treatment groups: nirmatrelvir-ritonavir, azvudine, and observation. Treatment outcomes, first nucleic acid test negative time, hospitalization time, and the conversion rate of mild or moderate disease to severe disease were recorded. RESULTS: First nucleic acid test negative time (23.5 days vs. 34 days, p = 0.015), hospitalization time (p = 0.015), and conversion rate (31.8 % vs. 8 %, p = 0.046) were statistically different between the nirmatrelvir-ritonavir and observation groups. First nucleic acid test negative time (20 days vs. 34 days, p = 0.009) and hospitalization time (p = 0.026) were statistically different between the azvudine and observation groups. ECOG score and liver disease were significantly associated with the conversion rate from mild or moderate disease to severe disease using multivariate analysis (p < 0.05). CONCLUSIONS: The authors found no significant differences existed in outcome measures between patients with HM and COVID-19 who were treated with nirmatrelvir-ritonavir or azvudine.

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

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

Characteristics and outcomes of patients with COVID-19 at high risk of disease progression receiving sotrovimab, oral antivirals or no treatment in England: a retrospective cohort study.

OBJECTIVE: To describe characteristics and acute clinical outcomes for patients with COVID-19 treated with sotrovimab, nirmatrelvir/ritonavir or molnupiravir, or untreated patients at highest risk per National Health Service (NHS) criteria. METHODS: Retrospective study of non-hospitalized patients between 1 December 2021 and 31 May 2022, using data from the Discover-NOW dataset (North-West London). Included patients were aged ≥12 years and treated with sotrovimab, nirmatrelvir/ritonavir or molnupiravir, or untreated but expected to be eligible for early treatment per NHS highest-risk criteria. COVID-19-related and all-cause hospitalizations were reported for 28 days from COVID-19 diagnosis (index). Subgroup analyses were conducted in patients with advanced renal disease, those aged 18-64 and ≥65 years, and by period of Omicron BA.1, BA.2 and BA.5 (post-hoc exploratory) predominance. RESULTS: Overall, 1503 treated and 4044 eligible high-risk untreated patients were included. A high proportion of patients on sotrovimab had advanced renal disease (29.3%), ≥3 high-risk comorbidities (47.6%) and were aged ≥65 years (36.9%). Five of 696 (0.7%) patients on sotrovimab, <5/337 (0.3-1.2%) on nirmatrelvir/ritonavir, 10/470 (2.1%) on molnupiravir and 114/4044 (2.8%) untreated patients were hospitalized with COVID-19. Similar results were observed across all subgroups. The proportion of patients dying within 28 days of the index period was similarly low across all cohorts (<2%). CONCLUSION: Patients receiving sotrovimab appeared to show evidence of multiple high-risk comorbidities. Low hospitalization rates were observed for all treated cohorts across subgroups and periods of predominant variants of concern. These results require confirmation with comparative effectiveness analyses adjusting for differences in underlying patient characteristics.

Fixing the Achilles Heel of Pfizer's Paxlovid for COVID-19 Treatment.

Nirmatrelvir (PF-07321332), a first-in-class inhibitor of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) main protease (Mpro), was developed by Pfizer under intense pressure during the pandemic to treat COVID-19. A weakness of nirmatrelvir is its limited metabolic stability, which led to the development of a combination therapy (paxlovid), involving coadministration of nirmatrelvir with the cytochrome P450 inhibitor ritonavir. However, limitations in tolerability of the ritonavir component reduce the scope of paxlovid. In response to these limitations, researchers at Pfizer have now developed the second-generation Mpro inhibitor PF-07817883 (ibuzatrelvir). Structurally related to nirmatrelvir, including with the presence of a trifluoromethyl group, albeit located differently, ibuzatrelvir manifests enhanced oral bioavailability, so it does not require coadministration with ritonavir. The development of ibuzatrelvir is an important milestone, because it is expected to enhance the treatment of COVID-19 without the drawbacks associated with ritonavir. Given the success of paxlovid in treating COVID-19, it is likely that ibuzatrelvir will be granted approval as an improved drug for treatment of COVID-19 infections, so complementing vaccination efforts and improving pandemic preparedness. The development of nirmatrelvir and ibuzatrelvir dramatically highlights the power of appropriately resourced modern medicinal chemistry to very rapidly enable the development of breakthrough medicines. Consideration of how analogous approaches can be used to develop similarly breakthrough medicines for infectious diseases such as tuberculosis and malaria is worthwhile.

Supply of nirmatrelvir/ritonavir and molnupiravir for patients with COVID-19 in the first eight months since listing on the Australian Pharmaceutical Benefits Scheme: A retrospective observational study.

OBJECTIVES: To compare the supply of molnupiravir and nirmatrelvir/ritonavir in relation to patient characteristics and other co-prescribed medicines and to estimate the number of patients without contraindications to nirmatrelvir/ritonavir who were treated with molnupiravir. STUDY DESIGN, SETTING: Retrospective observational study of patients identified in the Pharmaceutical Benefits Scheme (PBS) 10 % sample dataset who were supplied with either molnupiravir or nirmatrelvir/ritonavir between May and December 2022. We supplemented the PBS dataset with aggregated counts from published literature to determine prevalence of clinical contraindications to nirmatrelvir/ritonavir. MAIN OUTCOME MEASURES: We used multivariable Poisson regression to estimate risk ratios (RR) of receiving nirmatrelvir/ritonavir over molnupiravir. RESULTS: We identified 54,550 patients who received either nirmatrelvir/ritonavir (26.8 %) or molnupiravir (73.2 %). Their average age was 71.6 (SD = 13.4) years and 57.1 % were female. Patients were less likely to receive nirmatrelvir/ritonavir with increasing age (RR = 0.50; 95 % CI: 0.48-0.53; for ages 85 + compared to < 65 years) or who had received medicines contraindicated for use with nirmatrelvir/ritonavir (RR = 0.66; 95 % CI: 0.64-0.68). During the study period, we estimated that between 28.4 % and 45.4 % of patients aged ≥ 65 years had received molnupiravir in the absence of pharmacological and clinical contraindications to nirmatrelvir/ritonavir. CONCLUSION: Many prescriptions were written for molnupiravir where there were no contraindications to nirmatrelvir/ritonavir. The benefits that followed from prompt government action in approving and obtaining nirmatrelvir/ritonavir were therefore likely to be less than they could potentially have been. Governments should consider investing in quality improvement systems to ensure the best outcomes in terms of efficacy and safety.

Oral Nirmatrelvir-Ritonavir as Postexposure Prophylaxis for Covid-19.

BACKGROUND: Clinical trials of treatments for coronavirus disease 2019 (Covid-19) have not shown a significant benefit of postexposure prophylaxis. METHODS: We conducted a phase 2-3 double-blind trial to assess the efficacy and safety of nirmatrelvir-ritonavir in asymptomatic, rapid antigen test-negative adults who had been exposed to a household contact with Covid-19 within 96 hours before randomization. The participants were randomly assigned in a 1:1:1 ratio to receive nirmatrelvir-ritonavir (300 mg of nirmatrelvir and 100 mg of ritonavir) every 12 hours for 5 days or for 10 days or matching placebo for 5 or 10 days. The primary end point was the development of symptomatic SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection, confirmed on reverse-transcriptase-polymerase-chain-reaction (RT-PCR) or rapid antigen testing, through 14 days in participants who had a negative RT-PCR test at baseline. RESULTS: A total of 2736 participants were randomly assigned to a trial group - 921 to the 5-day nirmatrelvir-ritonavir group, 917 to the 10-day nirmatrelvir-ritonavir group, and 898 to the placebo group. Symptomatic, confirmed SARS-CoV-2 infection developed by day 14 in 2.6% of the participants in the 5-day nirmatrelvir-ritonavir group, 2.4% of those in the 10-day nirmatrelvir-ritonavir group, and 3.9% of those in the placebo group. In each nirmatrelvir-ritonavir group, the percentage of participants in whom symptomatic, confirmed SARS-CoV-2 infection developed did not differ significantly from that in the placebo group, with risk reductions relative to placebo of 29.8% (95% confidence interval [CI], -16.7 to 57.8; P = 0.17) in the 5-day nirmatrelvir-ritonavir group and 35.5% (95% CI, -11.5 to 62.7; P = 0.12) in the 10-day nirmatrelvir-ritonavir group. The incidence of adverse events was similar across the trial groups, with dysgeusia being the most frequently reported adverse event (in 5.9% and 6.8% of the participants in the 5-day and 10-day nirmatrelvir-ritonavir groups, respectively, and in 0.7% of those in the placebo group). CONCLUSIONS: In this placebo-controlled trial, postexposure prophylaxis with nirmatrelvir-ritonavir for 5 or 10 days did not significantly reduce the risk of symptomatic SARS-CoV-2 infection. (Funded by Pfizer; ClinicalTrials.gov number, NCT05047601.).

Extended remdesivir administration in haematological patients with malignancies and COVID-19 during the Omicron era: safety and outcomes.

OBJECTIVES: To describe the management of haematological patients experiencing prolonged SARS-CoV-2 viral shedding, as the optimal management strategy for this condition remains undetermined. METHODS: We conducted a retrospective evaluation of our prospectively followed cohort of haematological patients treated with remdesivir for more than 10 days. Starting January 2023, upon COVID-19 diagnosis, the treatment strategy was based on symptoms and PCR cycle threshold (Ct) as follows: (i) when Ct was 25 or less or if the patient had symptoms, a course of remdesivir for at least 10 days, nirmatrelvir/ritonavir for 5 days (whenever possible) and convalescent plasma was administered; and (ii) when the patient was asymptomatic and had a PCR Ct of more than 25, when possible, a course of 5 days of nirmatrelvir/ritonavir was administered. The patient was considered to have achieved viral clearance and, thus, remdesivir was stopped, in either of these cases: (i) PCR negativity, or (ii) subgenomic RNA negativity. RESULTS: From January to November 2023, 18 patients benefited from a safe extended remdesivir administration, resulting in detection of SARS-CoV-2 viral clearance in a median time of 3.5 weeks (IQR 2.6-3.9) (min-max 1.6-8.0). No clinical or biological side effects were detected. No patient died or needed further treatment for their COVID-19 episode. CONCLUSIONS: The extended course of remdesivir, combined with other active therapies for COVID-19 infection, was well tolerated. Cure and virus negativity were obtained in all these high-risk patients.