The Japanese package insert (J-PI) for nirmatrelvir/ritonavir (N/r) (specially approved pharmaceutical) includes numerous warnings about drug interactions. However, discrepancies in the information on drug interaction are reported between J-PI and foreign databases. This study aimed to evaluate various information sources on N/r drug interactions. We categorized and compared information on N/r drug interactions from the J-PI, prescribing information from foreign regulatory agencies, guidance from the National Institutes of Health and University Health Network, the Ontario coronavirus disease 2019 (COVID-19) Science Advisory Table, University of Liverpool, Lexicomp, and the Japanese Society of Pharmaceutical Health Care and Sciences (JSPHCS). We assessed information quantity, missing data in J-PI, predicted change of the area under the blood concentration-time curve (AUC) for nirmatrelvir or co-administered drugs, and the information source consistency. From these information sources, we compiled a dataset with 115 contraindications and 203 precautions for N/r co-administration, and 51 contraindications are missing in J-PI. Among them, at least 12 drugs have large predicted AUC changes with N/r (AUC ≥5-fold or <1/5 of the baseline value). Nine of these 12 drugs are included as contraindications in Lexicomp and the JSPHCS. The consistency among the information sources is low. Information in the J-PI alone may be insufficient and Lexicomp or the JSPHCS guidelines should be useful because of their large amounts of information and wide coverage of drugs with large AUC changes. Due to low source consistency, multiple sources are needed for clinical management.

In a pivotal trial (EPIC-HR), a 5-day course of oral ritonavir-boosted nirmatrelvir, given early during symptomatic SARS-CoV-2 infection (within three days of symptoms onset), decreased hospitalization and death by 89.1% and nasal viral load by 0.87 log relative to placebo in high-risk individuals. Yet, nirmatrelvir/ritonavir failed as post-exposure prophylaxis in a trial, and frequent viral rebound has been observed in subsequent cohorts. We develop a mathematical model capturing viral-immune dynamics and nirmatrelvir pharmacokinetics that recapitulates viral loads from this and another clinical trial (PLATCOV). Our results suggest that nirmatrelvir\'s in vivo potency is significantly lower than in vitro assays predict. According to our model, a maximally potent agent would reduce the viral load by approximately 3.5 logs relative to placebo at 5 days. The model identifies that earlier initiation and shorter treatment duration are key predictors of post-treatment rebound. Extension of treatment to 10 days for Omicron variant infection in vaccinated individuals, rather than increasing dose or dosing frequency, is predicted to lower the incidence of viral rebound significantly.

BACKGROUND: The COVID-19 pandemic has taken many forms and continues to evolve, now around the Omicron wave, raising concerns over the globe. With COVID-19 being declared no longer a \"public health emergency of international concern (PHEIC),\" the COVID pandemic is still far from over, as new Omicron subvariants of interest and concern have risen since January of 2023. Mainly with the XBB.1.5 and XBB.1.16 subvariants, the pandemic is still very much \"alive\" and \"breathing.\"
METHODS: This review consists of five highly concerning questions about the current state of the COVID Omicron peak. We searched four main online databases to answer the first four questions. For the last one, we performed a systematic review of the literature, with keywords \"Omicron,\" \"Guidelines,\" and \"Recommendations.\"
RESULTS: A total of 31 articles were included. The main symptoms of the current Omicron wave include a characteristically high fever, coughing, conjunctivitis (with itching eyes), sore throat, runny nose, congestion, fatigue, body ache, and headache. The median incubation period of the symptoms is shorter than the previous peaks. Vaccination against COVID can still be considered effective for the new subvariants.
CONCLUSIONS: Guidelines recommend continuation of personal protective measures, third and fourth dose boosters, along with administration of bivalent messenger RNA vaccine boosters. The consensus antiviral treatment is combination therapy using Nirmatrelvir and Ritonavir, and the consensus for pre-exposure prophylaxis is Tixagevimab and Cilgavimab combination. We hope the present paper raises awareness for the continuing presence of COVID and ways to lower the risks, especially for at-risk groups.

OBJECTIVE: Reports regarding the association of remdesivir use for the treatment of Coronavirus disease 2019 (COVID-19) with the development of acute kidney injury (AKI) are inconsistent, and the associations between the use of other antivirals and AKI remain unclear. Therefore, this study investigated whether the use of antiviral drugs for the treatment of COVID-19 is a risk factor for the development of AKI.
METHODS: This study analyzed 176,197 reports submitted to the Japanese Adverse Event Reporting Database between 2020 and 2022. Reporting odds ratios (RORs) and 95% confidence intervals (95%CIs) for AKI that were associated with the use of antiviral drugs in patients with COVID-19 were calculated after adjusting for potential confounders.
RESULTS: Overall, 5,879 of the reports analyzed were associated with AKI. Signs of AKI were detected with the use of remdesivir [crude ROR (cROR)=2.45; 95%CI=1.91-3.14] and nirmatrelvir/ritonavir (cROR=6.07; 95%CI=4.06-9.06). These results were maintained even after adjusting for potential confounders [remdesivir: adjusted ROR (aROR)=2.18; 95%CI=1.69-2.80, nirmatrelvir/ritonavir: aROR=5.24; 95%CI=3.48-7.90]. However, when analyzing data stratified by reporting year, the association between remdesivir and AKI appeared to diminish over time and was not sustained.
CONCLUSIONS: Nirmatrelvir/ritonavir use may be associated with developing AKI. This knowledge may be useful in helping patients with COVID-19 avoid AKI complications.

(1) Background: Geriatric patients are at high risk of complications of Coronavirus disease-2019 (COVID-19) and are good candidates for antiviral drugs. (2) Methods: A retrospective study of electronic health records (EHRs) aiming to describe antiviral (nirmatrelvir and ritonavir (nirmatrelvir/r) or remdesivir) use, drug-drug interactions (DDIs) and adverse drug reactions (ADRs) in elderly patients (75 and over), hospitalized with mild-to-moderate COVID-19 between July 2022 and June 2023. (3) Results: Out of 491 patients (mean age: 86.9 years), 180 (36.7%) received nirmatrelvir/r, 78 (15.9%) received remdesivir, and 233 (47.4%) received no antiviral therapy. No association was found between the choice of antiviral and the demographic or medical data. No serious ADR was observed. Nirmatrelvir/r dosage adjustment was inadequate in 65% of patients with renal impairment. In total, 128 patients (71%) on nirmatrelvir/r had potential pharmacokinetic DDIs, with 43 resulting in a possibly related ADR. In the remdesivir group, pharmacodynamic DDIs were more frequent, with QTc prolongation risk in 56 patients (72%). Only 20 patients underwent follow-up ECG, revealing QTc prolongation in 4. (4) Conclusions: There is an underutilization of antivirals despite their justified indications. Nirmatrelvir/r dosage was rarely adjusted to renal function. Dose adjustments and closer monitoring are needed due to the high risk of drug interactions.

Cobicistat is a derivative of ritonavir marketed as a pharmacoenhancer for anti-HIV therapy. This study investigated the interaction of cobicistat with the target protein, drug-metabolizing cytochrome P450 3A4 (CYP3A4), at the molecular level using spectral, kinetic, functional, and structural approaches. It was found that, similar to ritonavir, cobicistat directly coordinates to the heme via the thiazole nitrogen but its affinity and the binding rate are 2-fold lower: 0.030 μM and 0.72 s-1, respectively. The newly determined 2.5 Å crystal structure of cobicistat-bound CYP3A4 suggests that these changes arise from the inability of cobicistat to H-bond to the active site S119 and establish multiple stabilizing contacts with the F-F\' connecting fragment, which becomes disordered upon steric clashing with the bulky morpholine moiety. Nonetheless, cobicistat inhibits recombinant CYP3A4 as potently as ritonavir (IC50 of 0.24 μM vs 0.22 μM, respectively) due to strong ligation to the heme and formation of extensive hydrophobic/aromatic interactions via the phenyl side-groups. To get insights into the inhibitory mechanism, the K257 residue, known to be solely and irreversibly modified by the reactive ritonavir metabolite, was substituted with alanine. Neither this nor control K266A mutation changed the extent of time-dependent inhibition of CYP3A4 by cobicistat and ritonavir, suggesting the existence of alternative inactivation mechanism(s). More importantly, K257 was found to be functionally important and contributed to CYP3A4 allosterism, possibly by modulating protein-ligand interactions through conformational dynamics.

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The comparative crystallizability and polymorphic selectivity of ritonavir, a novel protease inhibitor for the treatment of acquired immune-deficiency syndrome, as a function of solvent selection are examined through an integrated and self-consistent experimental and computational molecular modeling study. Recrystallization at high supersaturation by rapid cooling at 283.15 K is found to produce the metastable \"disappeared\" polymorphic form I from acetone, ethyl acetate, acetonitrile, and toluene solutions in contrast to ethanol which produces the stable form II. Concomitant crystallization of the other known solid forms is not found under these conditions. Isothermal crystallization studies using turbidometric detection based upon classical nucleation theory reveal that, for an equal induction time, the required driving force needed to initiate solution nucleation decreases with solubility in the order of ethanol, acetone, acetonitrile, ethyl acetate, and toluene consistent with the expected desolvation behavior predicted from the calculated solute solvation free energies. Molecular dynamics simulations of the molecular and intermolecular chemistry reveal the presence of conformational interplay between intramolecular and intermolecular interactions within the solution phase. These encompass the solvent-dependent formation of intramolecular O-H...O hydrogen bonding between the hydroxyl and carbamate groups coupled with differing conformations of the hydroxyl\'s shielding phenyl groups. These conformational preferences and their relative interaction propensities, as a function of solvent selection, may play a rate-limiting role in the crystallization behavior by not only inhibiting to different degrees the nucleation process but also restricting the assembly of the optimal intermolecular hydrogen bonding network needed for the formation of the stable form II polymorph.

BACKGROUND: There is an urgent need for therapeutic strategies for inpatients with severe or critical COVID-19. The evaluation of the clinical benefits of nirmatrelvir and ritonavir (Nmr/r) for these patients beyond five days of symptom onset is insufficient.
METHODS: A new propensity score-matched cohort was constructed by using multicenter data from 6695 adult inpatients with COVID-19 from December 2022 to February 2023 in China after the epidemic control measures were lifted across the country. The severity of disease of the inpatients was based on the tenth trial edition of the Guidelines on the Diagnosis and Treatment of COVID-19 in China. The symptom onset of 1870 enrolled severe or critical inpatients was beyond five days, and they received either Nmr/r plus standard treatment or only standard care. The ratio of patients whose SOFA score improved more than 2 points, crucial respiratory endpoints, changes in inflammatory markers, safety on the seventh day following the initiation of Nmr/r treatment, and length of hospital stay were evaluated.
RESULTS: In the Nmr/r group, on Day 7, the number of patients with an improvement in SOFA score ≥ 2 was much greater than that in the standard treatment group (P = 0.024) without a significant decrease in glomerular filtration rate (P = 0.815). Additionally, the rate of new intubation was lower (P = 0.004) and the no intubation days were higher (P = 0.003) in the first 7 days in the Nmr/r group. Other clinical benefits were limited.
CONCLUSIONS: Our study may provide new insight that inpatients with severe or critical COVID-19 beyond five days of symptom onset benefit from Nmr/r. Future studies, particularly randomized controlled trials, are necessary to verify the above findings.

PAXLOVID™ (Co-packaging of Nirmatrelvir with Ritonavir) has been approved for the treatment of Coronavirus Disease 2019 (COVID-19). The goal of the experiment was to create an accurate and straightforward analytical method using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to simultaneously quantify nirmatrelvir and ritonavir in rat plasma, and to investigate the pharmacokinetic profiles of these drugs in rats. After protein precipitation using acetonitrile, nirmatrelvir, ritonavir, and the internal standard (IS) lopinavir were separated using ultra performance liquid chromatography (UPLC). This separation was achieved with a mobile phase composed of acetonitrile and an aqueous solution of 0.1% formic acid, using a reversed-phase column with a binary gradient elution. Using multiple reaction monitoring (MRM) technology, the analytes were detected in the positive electrospray ionization mode. Favorable linearity was observed in the calibration range of 2.0-10000 ng/mL for nirmatrelvir and 1.0-5000 ng/mL for ritonavir, respectively, within plasma samples. The lower limits of quantification (LLOQ) attained were 2.0 ng/mL for nirmatrelvir and 1.0 ng/mL for ritonavir, respectively. Both drugs demonstrated inter-day and intra-day precision below 15%, with accuracies ranging from -7.6% to 13.2%. Analytes were extracted with recoveries higher than 90.7% and without significant matrix effects. Likewise, the stability was found to meet the requirements of the analytical method under different conditions. This UPLC-MS/MS method, characterized by enabling accurate and precise quantification of nirmatrelvir and ritonavir in plasma, was effectively utilized for in vivo pharmacokinetic studies in rats.