Cystic fibrosis transmembrane conductance regulator (CFTR) modulating therapies, including elexacaftor‐tezacaftor‐ivacaftor, are primarily eliminated through cytochrome P450 (CYP) 3A–mediated ...metabolism. This creates a therapeutic challenge to the treatment of coronavirus disease 2019 (COVID‐19) with nirmatrelvir‐ritonavir in people with cystic fibrosis (CF) due to the potential for significant drug–drug interactions (DDIs). However, the population with CF is more at risk of serious illness following COVID‐19 infection and hence it is important to manage the DDI risk and provide treatment options. CYP3A‐mediated DDI of elexacaftor‐tezacaftor‐ivacaftor was evaluated using a physiologically‐based pharmacokinetic modeling approach. Modeling was performed incorporating physiological information and drug‐dependent parameters of elexacaftor‐tezacaftor‐ivacaftor to predict the effect of ritonavir (the CYP3A inhibiting component of the combination) on the pharmacokinetics of elexacaftor‐tezacaftor‐ivacaftor. The elexacaftor‐tezacaftor‐ivacaftor models were verified using independent clinical pharmacokinetic and DDI data of elexacaftor‐tezacaftor‐ivacaftor with a range of CYP3A modulators. When ritonavir was administered on Days 1 through 5, the predicted area under the curve (AUC) ratio of ivacaftor (the most sensitive CYP3A substrate) on Day 6 was 9.31, indicating that its metabolism was strongly inhibited. Based on the predicted DDI, the dose of elexacaftor‐tezacaftor‐ivacaftor should be reduced when coadministered with nirmatrelvir‐ritonavir to elexacaftor 200 mg–tezacaftor 100 mg–ivacaftor 150 mg on Days 1 and 5, with delayed resumption of full‐dose elexacaftor‐tezacaftor‐ivacaftor on Day 9, considering the residual inhibitory effect of ritonavir as a mechanism‐based inhibitor. The simulation predicts a regimen of elexacaftor‐tezacaftor‐ivacaftor administered concomitantly with nirmatrelvir‐ritonavir in people with CF that will likely decrease the impact of the drug interaction.
Cystic fibrosis (CF) patients present with a variety of symptoms, including mood and cognition deficits, in addition to classical respiratory, and autonomic issues. This suggests that brain injury, ...which can be examined with non-invasive magnetic resonance imaging (MRI), is a manifestation of this condition. However, brain tissue integrity in sites that regulate cognitive, autonomic, respiratory, and mood functions in CF patients is unclear. Our aim was to assess regional brain changes using high-resolution T1-weighted images based gray matter (GM) density and T2-relaxometry procedures in CF over control subjects.
We acquired high-resolution T1-weighted images and proton-density (PD) and T2-weighted images from 5 CF and 15 control subjects using a 3.0-Tesla MRI. High-resolution T1-weighted images were partitioned to GM-tissue type, normalized to a common space, and smoothed. Using PD- and T2-weighted images, whole-brain T2-relaxation maps were calculated, normalized, and smoothed. The smoothed GM-density and T2-relaxation maps were compared voxel-by-voxel between groups using analysis of covariance (covariates, age and sex; SPM12, p < 0.001).
Significantly increased GM-density, indicating tissues injury, emerged in multiple brain regions, including the cerebellum, hippocampus, amygdala, basal forebrain, insula, and frontal and prefrontal cortices. Various brain areas showed significantly reduced T2-relaxation values in CF subjects, indicating predominant acute tissue changes, in the cerebellum, cerebellar tonsil, prefrontal and frontal cortices, insula, and corpus callosum.
Cystic fibrosis subjects show predominant acute tissue changes in areas that control mood, cognition, respiratory, and autonomic functions and suggests that tissue changes may contribute to symptoms resulting from ongoing hypoxia accompanying the condition.
Abstract
Pulmonary function testing (PFT) allows for quantitative analysis of lung function. However, as a result of the coronavirus disease 2019 (COVID-19) pandemic, a majority of international ...medical societies have postponed PFTs in an effort to mitigate disease transmission, complicating the continuity of care in high-risk patients diagnosed with COVID-19 or preexisting lung pathologies. Here, we describe the development of a non-contact wearable pulmonary sensor for pulmonary waveform analysis, pulmonary volume quantification, and crude thoracic imaging using the eddy current (EC) phenomenon. Statistical regression analysis is performed to confirm the predictive validity of the sensor, and all data are continuously and digitally stored with a sampling rate of 6,660 samples/second. Wearable pulmonary function sensors may facilitate rapid point-of-care monitoring for high-risk individuals, especially during the COVID-19 pandemic, and easily interface with patient hospital records or telehealth services.
Acute pulmonary exacerbations (APE) involving
are associated with increased morbidity and mortality in cystic fibrosis (CF) patients. Drug resistance is a significant challenge to treatment. ...Ceftazidime-avibactam (CZA) demonstrates excellent
activity against isolates recovered from CF patients, including drug-resistant strains. Altered pharmacokinetics (PK) of several beta-lactam antibiotics have been reported in CF patients. Therefore, this study sought to characterize the PK of CZA and perform target attainment analyses to determine the optimal treatment regimen. The PK of CZA in 12 adult CF patients administered 3 intravenous doses of 2.5 g every 8 h infused over 2 h were determined. Population modeling utilized the maximum likelihood expectation method. Monte Carlo simulations determined the probability of target attainment (PTA). An exposure target consisting of the cumulative percentage of a 24-h period that the free drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (
) was evaluated for ceftazidime (CAZ), and an exposure target consisting of the cumulative percentage of a 24-h period that the free drug concentration exceeds a 1-mg/liter threshold concentration (
) was evaluated for avibactam (AVI). Published CAZ and CZA MIC distributions were incorporated to evaluate cumulative response probabilities. CAZ and AVI were best described by one-compartment models. The values of total body clearance (CL; CAZ CL, 7.53 ± 1.28 liters/h; AVI CL, 12.30 ± 1.96 liters/h) and volume of distribution (
; CAZ
, 18.80 ± 6.54 liters; AVI
, 25.30 ± 4.43 liters) were broadly similar to published values for healthy adults. CZA achieved a PTA (
, 50%) of >0.9 for MICs of ≤16 mg/liter. The overall likelihood of a treatment response was 0.82 for CZA, whereas it was 0.42 for CAZ. These data demonstrate improved pharmacodynamics of CZA in comparison with those of CAZ and provide guidance on the optimal dosing of CZA for future studies. (This study has been registered at ClinicalTrials.gov under registration no. NCT02504827.).
Elexacaftor/tezacaftor/ivacaftor (ETI) treatment has potential benefits in lung transplant recipients, including improvements in extrapulmonary manifestations, such as gastrointestinal and sinus ...disease; however, ivacaftor is an inhibitor of cytochrome P450 3A (CYP3A) and may, therefore, pose a risk for elevated systemic exposure to tacrolimus. The aim of this investigation is to determine the impact of ETI on tacrolimus exposure and devise an appropriate dosing regimen to manage the risk of this drug-drug interaction (DDI). The CYP3A-mediated DDI of ivacaftor-tacrolimus was evaluated using a physiologically based pharmacokinetic (PBPK) modeling approach, incorporating CYP3A4 inhibition parameters of ivacaftor and in vitro enzyme kinetic parameters of tacrolimus. To further support the findings in PBPK modeling, we present a case series of lung transplant patients who received both ETI and tacrolimus. We predicted a 2.36-fold increase in tacrolimus exposure when co-administered with ivacaftor, which would require a 50% dose reduction of tacrolimus upon initiation of ETI treatment to avoid the risk of elevated systemic exposure. Clinical cases (N = 13) indicate a median 32% (IQR: -14.30, 63.80) increase in the dose-normalized tacrolimus trough level (trough concentration/weight-normalized daily dose) after starting ETI. These results indicate that the concomitant administration of tacrolimus and ETI may lead to a clinically significant DDI, requiring the dose adjustment of tacrolimus.
Introduction
Elexacaftor/tezacaftor/ivacaftor (ETI) treatment is associated with significant improvement in lung function in people with cystic fibrosis (pwCF); however, some patients experience ...adverse effects (AEs) including hepatotoxicity. One potential strategy is dose reduction in ETI with the goal of maintaining therapeutic efficacy while resolving AEs. We report our experience of dose reduction in individuals who experienced AEs following ETI therapy. We provide mechanistic support for ETI dose reduction by exploring predicted lung exposures and underlying pharmacokinetics–pharmacodynamics (PK‐PD) relationships.
Method
Adults prescribed ETI who underwent dose reduction due to the AEs were included in this case series, and their percent predicted forced expiratory volume in 1 s (ppFEV1) and self‐reported respiratory symptoms were collected. The full physiologically based pharmacokinetic (PBPK) models of ETI were developed incorporating physiological information and drug‐dependent parameters. The models were validated against available pharmacokinetic and dose–response relationship data. The models were then used to predict lung concentrations of ETI at steady‐state.
Results
Fifteen patients underwent dose reduction in ETI due to AEs. Clinical stability without significant changes in ppFEV1 after dose reduction was observed in all patients. Resolution or improvement of AEs occurred in 13 of the 15 cases. The model‐predicted lung concentrations of reduced dose ETI exceeded the reported half maximal effective concentration (EC50) from measurement of in vitro chloride transport, providing a hypothesis as to why therapeutic efficacy was maintained.
Conclusion
Albeit in a small number of patients, this study provides evidence that reduced ETI doses in pwCF who have experienced AEs may be effective. The PBPK models enable exploration of a mechanistic basis for this finding by simulating target tissue concentrations of ETI that can be compared with drug efficacy in vitro.
Over the past decade, the prevalence of infections involving methicillin-resistant
(MRSA) in patients with cystic fibrosis (CF) has increased significantly. Tedizolid (TZD) demonstrates excellent ...activity against MRSA and a favorable safety profile. The pharmacokinetics of several antibiotics have been shown to be altered in CF patients. The purpose of this study was to characterize the pharmacokinetics of tedizolid in this population. Eleven patients with CF were randomized to receive tedizolid phosphate at 200 mg orally or intravenously once daily for 3 doses with a minimum 2-day washout, followed by crossover to the remaining dosage form. Plasma and expectorated sputum were collected following the third dose of each dosage form for analysis. Population pharmacokinetic analysis was performed using the maximum likelihood expectation maximization method, and the disposition of TZD was described by a two-compartment model. The sputum concentrations exceeded the unbound plasma concentrations with an estimated mean sputum-to-unbound plasma penetration ratio of 2.88 (coefficient of variation, 50.3%). The estimated population mean ± standard deviation of total clearance, central volume of distribution, and bioavailability were 9.72 ± 1.62 liters/h, 61.6 ± 6.94 liters, and 1.04 ± 0.232, respectively. The total clearance was higher in CF patients than in healthy volunteers; however, it was similar to published data for patients with complicated skin and skin structure infections (cSSSIs). This study demonstrates that the oral bioavailability of tedizolid is excellent in patients with CF and that the plasma pharmacokinetics are similar to those reported for patients with cSSSIs.
Chronic airway infection and inflammation contribute to the progressive loss of lung function and shortened survival of patients with cystic fibrosis (CF). Rhesus theta defensin-1 (RTD-1) is a ...macrocyclic host defense peptide with antimicrobial and immunomodulatory activities. Combined with favorable preclinical safety and peptide stability data, RTD-1 warrants investigation to determine its therapeutic potential for treatment of CF lung disease. We sought to evaluate the therapeutic potential of RTD-1 for CF airway infection and inflammation using
,
, and
models. We evaluated RTD-1's effects on basal and
induced inflammation in CF sputum leukocytes and CF bronchial epithelial cells. Peptide stability was evaluated by incubation with CF sputum. Airway pharmacokinetics, safety, and tolerance studies were performed in naive mice. Aerosolized RTD-1 treatment effects were assessed by analyzing lung bacterial burdens and airway inflammation using an established model of chronic
endobronchial infection in CF (ΔF508) mice. RTD-1 directly reduces metalloprotease activity, as well as inflammatory cytokine secretion from CF airway leukocyte and bronchial epithelial cells. Intrapulmonary safety, tolerability, and stability data support the aerosol administration route. RTD-1 reduced the bacterial lung burden, airway neutrophils, and inflammatory cytokines in CF mice with chronic
lung infection. Collectively, these studies support further development of RTD-1 for treatment of CF airway disease.
Oral azithromycin (AZM) has been shown to reduce airway inflammation and disrupt biofilm formation. However, chronic AZM therapy may result in QT interval (QTc) prolongation.
The goals of this study ...were twofold: (i) to characterize the risk of QTc prolongation in adult patients with cystic fibrosis (CF) receiving AZM and other potential QTc-prolonging agents, and (ii) to describe and capture the number of potential QTc-prolonging agents patients with CF are prescribed.
A retrospective study was conducted over a 3-year period in an adult CF center. QTc values were recorded from electrocardiograms. Univariate and multivariate analyses were conducted. Standard QTc prolongation definitions (males ≥ 450 msec, females ≥ 470 msec) were used.
A total of 89 adult CF patient's records were reviewed. Sixty-eight patients received chronic AZM therapy. Two male patients had prolonged QTc, but only 1 received chronic AZM therapy. The median QTc interval between patients receiving and not receiving AZM was not significantly different (405 interquartile range, IQR: 388-425 vs 394 IQR: 384-413 msec, respectively, p=0.14). Also, the QTc interval for patients taking chronic AZM 500 mg Monday/Wednesday/Friday or 250 mg daily was not significantly different (401 IQR: 383-419 vs 409 IQR: 394-427 msec, respectively, p=0.48). When stratified by the number of QTc-prolonging medications (AZM vs no AZM), there was no significant difference in median QTc values between patients receiving zero to ≥ 5 QTc-prolonging medications.
An association between chronic AZM therapy and longer QTc intervals or significant QTc prolongation was not shown.
Abstract A hallmark of cystic fibrosis is the massive recruitment of neutrophils into the lung compartment in response to chronic Pseudomonas aeruginosa infection. The overexuberant neutrophilic ...response results in release of proteases (e.g. neutrophil elastase and matrix metalloproteinase-9) leading to matrix breakdown, airway remodeling, and progressive loss of lung function. Doxycycline is used clinically for the management of periodontitis due to its potent direct inhibition of matrix metalloproteinases; however, little is known regarding its potential anti-inflammatory properties and clinical utility in the context of cystic fibrosis airway disease. CF (IB3-1) and corrected (S9) bronchial epithelial cell lines were used to determine the cytotoxicity and anti-inflammatory effects of doxycycline in-vitro . Exposure to doxycycline, at low concentrations, resulted in minimal cell death and dose dependent reductions in release of CXCL-8 and MMP-9 protein. To confirm these findings, mechanistic analysis revealed ERK 1/2, p38, and JNK, but not NF-κB p65 dependent cell signaling inhibition with doxycycline treatment. These findings indicate that doxycycline exhibits anti-inflammatory activity in CF lung epithelial cells at concentrations below the cytotoxic potential. These data are encouraging and indicate in-vivo studies are warranted.
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