Effects of rifampicin on the pharmacokinetics of roflumilast and roflumilast N-oxide in healthy subjects

Insights into Inhalation Drug Disposition: The Roles of Pulmonary Drug-Metabolizing Enzymes and Transporters

The past five decades have witnessed remarkable advancements in the field of inhaled medicines targeting the lungs for respiratory disease treatment. As a non-invasive drug delivery route, inhalation therapy offers numerous benefits to respiratory patients, including rapid and targeted exposure at specific sites, quick onset of action, bypassing first-pass metabolism, and beyond. Understanding the characteristics of pulmonary drug transporters and metabolizing enzymes is crucial for comprehending efficient drug exposure and clearance processes within the lungs. These processes are intricately linked to both local and systemic pharmacokinetics and pharmacodynamics of drugs. This review aims to provide a comprehensive overview of the literature on lung transporters and metabolizing enzymes while exploring their roles in exogenous and endogenous substance disposition. Additionally, we identify and discuss the principal challenges in this area of research, providing a foundation for future investigations aimed at optimizing inhaled drug administration. Moving forward, it is imperative that future research endeavors to focus on refining and validating in vitro and ex vivo models to more accurately mimic the human respiratory system. Such advancements will enhance our understanding of drug processing in different pathological states and facilitate the discovery of novel approaches for investigating lung-specific drug transporters and metabolizing enzymes. This deeper insight will be crucial in developing more effective and targeted therapies for respiratory diseases, ultimately leading to improved patient outcomes.

Prediction of drug-drug interactions between roflumilast and CYP3A4/1A2 perpetrators using a physiologically-based pharmacokinetic (PBPK) approach

This study aimed to develop a physiologically-based pharmacokinetic (PBPK) model to predict changes in the pharmacokinetics (PK) and pharmacodynamics (PD, PDE4 inhibition) of roflumilast (ROF) and ROF N-oxide when co-administered with eight CYP3A4/1A2 perpetrators. The population PBPK model of ROF and ROF N-oxide has been successfully developed and validated based on the four clinical PK studies and five clinical drug-drug interactions (DDIs) studies. In PK simulations, every ratio of prediction to observation for PK parameters fell within the range 0.7 to 1.5. In DDI simulations, except for tow peak concentration ratios (Cmax) of ROF with rifampicin (prediction: 0.63 vs. observation: 0.19) and with cimetidine (prediction: 1.07 vs. observation: 1.85), the remaining predicted ratios closely matched the observed ratios. Additionally, the PBPK model suggested that co-administration with the three perpetrators (cimetidine, enoxacin, and fluconazole) may use with caution, with CYP3A4 strong inhibitor (ketoconazole and itraconazole) or with dual CYP3A41A2 inhibitor (fluvoxamine) may reduce to half-dosage or use with caution, while co-administration with CYP3A4 strong or moderate inducer (rifampicin, efavirenz) should avoid. Overall, the present PBPK model can provide recommendations for adjusting dosing regimens in the presence of DDIs.

A Single-center, Open-label, Parallel Control Study Comparing the Pharmacokinetics and Safety of a Single Oral Dose of Roflumilast and Its Active Metabolite Roflumilast N-oxide in Healthy Chinese and Caucasian Volunteers

Roflumilast is a phosphodiesterase-4 inhibitor which treats chronic obstructive pulmonary disease (COPD). Roflumilast N-oxide is the major metabolite of roflumilast with a similar mechanism of action to roflumilast. Although racial differences in roflumilast drug disposition have been observed, the necessity of dose adjustment is subject to debate. This study compares the pharmacokinetics of a single 500 μg dose of roflumilast in healthy Chinese and Caucasian subjects under uniform conditions. Chinese subjects were found to have longer t_1/2 and higher AUC_0-t and C_max than Caucasian subjects. The point estimates on the geometric mean of AUC_0-t in Chinese subjects were 22% higher for roflumilast and 46% higher for roflumilast N-oxide. Point estimates on the geometric mean of C_max were 9% and 24% higher for roflumilast and roflumilast N-oxide, respectively. Total phosphodiesterase-4 (PDE4) inhibitory (tPDE4i) activity, a theoretical parameter that describes the combined contribution to PDE4 inhibitory activity of roflumilast and roflumilast N-oxide, was 44% higher in Chinese subjects than in Caucasian subjects. With about a 10-fold higher plasma AUC compared to the parent roflumilast and a much longer observed half-life, roflumilast N-oxide has been estimated to contribute about 90% of tPDE4i, with 10% attributed to the parent compound roflumilast. Following body weight normalization, these figures were lower but remained significant. Safety analysis showed signs of reduced tolerance or different pharmacodynamic response to roflumilast in Chinese recipients than in Caucasians. Our results suggest that Chinese patients should receive a dose of roflumilast lower than 500 μg daily during future clinical trials.

Clinical assessment of gepotidacin (GSK2140944) as a victim and perpetrator of drug-drug interactions via CYP3A metabolism and transporters

Gepotidacin is a novel triazaacenaphthylene antibiotic in phase III development. Based on nonclinical in vitro characterization of gepotidacin metabolism, two phase I studies were conducted in healthy participants to investigate clinical drug-drug interactions (DDIs). We assessed gepotidacin as a DDI victim with a potent cytochrome P450 (CYP) 3A4/P-glycoprotein (P-gp) inhibitor (itraconazole), potent CYP3A4 inducer (rifampicin), and nonspecific organic cation transporter (OCT)/multidrug and toxic extrusion transporter (MATE) renal transport inhibitor (cimetidine) via single doses of gepotidacin before and after co-administration with multiple doses of the modulator drugs. Gepotidacin DDI perpetrator potential for P-gp inhibition (digoxin) and CYP3A4 inhibition (midazolam) was evaluated via single doses of the two-drug cocktail without and with gepotidacin. The DDI magnitudes were interpreted based on area under the concentration-time curve (AUC). A weak DDI (AUC increase 48%-50%) was observed for gepotidacin co-administered with itraconazole. A clinically significant decrease in gepotidacin plasma AUC (52%) was observed with rifampicin coadministration, indicating a moderate DDI. There was no DDI for gepotidacin with cimetidine; a unique biomarker approach showed increased serum creatinine (24%), decreased renal clearance of creatinine (21%), and N1-methylnicotinamide (39%), which confirmed extensive MATE inhibition and partial OCT2 inhibition. Gepotidacin was not a P-gp DDI perpetrator, although the maximum plasma concentration of digoxin increased (53%) and is potentially clinically relevant given its narrow therapeutic index. Gepotidacin demonstrated weak CYP3A4 inhibition with midazolam (<2-fold AUC increase). There were no new safety-risk profile findings. These results will inform the safe and efficacious clinical use of gepotidacin when co-administered with other drugs.

Virtual Screening of DrugBank Reveals Two Drugs as New BCRP Inhibitors

The breast cancer resistance protein (BCRP) is an ABC transporter playing a crucial role in the pharmacokinetics of drugs. The early identification of substrates and inhibitors of this efflux transporter can help to prevent or foresee drug-drug interactions. In this work, we built a ligand-based in silico classification model to predict the inhibitory potential of drugs toward BCRP. The model was applied as a virtual screening technique to identify potential inhibitors among the small-molecules subset of DrugBank. Ten compounds were selected and tested for their capacity to inhibit mitoxantrone efflux in BCRP-expressing PLB985 cells. Results identified cisapride (IC₅₀ = 0.4 µM) and roflumilast (IC₅₀ = 0.9 µM) as two new BCRP inhibitors. The in silico strategy proved useful to prefilter potential drug-drug interaction perpetrators among a database of small molecules and can reduce the amount of compounds to test.

Roflumilast in the management of chronic obstructive pulmonary disease

PURPOSE

The pharmacology, pharmacokinetics, efficacy, and safety of roflumilast-the first in a new class of agents for managing chronic obstructive pulmonary disease (COPD)-are reviewed.

SUMMARY

Roflumilast (Daliresp, Forest Pharmaceuticals) is an oral phosphodiesterase-4 (PDE-4) inhibitor that targets inflammatory cells involved in triggering COPD exacerbations. The only PDE-4 inhibitor approved by the Food and Drug Administration, roflumilast is available in 500-μg tablets to be administered once daily. In six placebo-controlled trials involving nearly 4500 patients with COPD of varying severity, the use of roflumilast was associated with reduced COPD exacerbations and improved lung function, as determined by spirometry, with the greatest benefits observed in patients with severe COPD who had chronic bronchitis and a history of frequent exacerbations; clinical efficacy was demonstrated in patients receiving roflumilast alone as well as those receiving concomitant inhaled long-acting β2-agonist (LABA) therapy. The most common adverse events in clinical trials of roflumilast were diarrhea, nausea, and headache. Weight loss and an increased risk of psychiatric events have also been reported in association with roflumilast use. As roflumilast is rapidly converted to its active metabolite via cytochrome P-450 (CYP) isoenzymes, coadministration with strong CYP inducers is not recommended. Research to better define roflumilast's role in COPD management, including a study to determine whether it confers additive benefits when used in combination with standard inhaled therapies other than LABAs, is ongoing.

CONCLUSION

Roflumilast is a safe and effective option for controlling COPD exacerbations in a defined subset of patients for whom the available treatment alternatives are very limited.

Pharmacokinetic behavior presents drug therapy challenges

There are conditions that cause a substantial change in drug clearance to such a degree that how a specific drug is managed to optimize drug response and minimize drug toxicity presents a challenge. This review will focus on recent literature (within the past 5 years) that evaluates pathophysiologic and genetic conditions and drug interactions which can change drug clearance to the magnitude that response is affected. Situations discussed that cause an increase in drug clearance will include: augmented renal clearance in critically ill patients; ultrafast drug metabolism caused by gene duplication; and enzyme induction interactions caused by rifampin. Situations discussed that result in a reduction in clearance will include: multiple organ failure in critically ill, patients with non-functioning CYP2D6 and CYP2C8/9 alleles, and CYP3A4 drug interactions with erythromycin and clarithromycin. In each case evaluated clearance is changed to the magnitude such that managing drug therapy can be difficult.

Update on rifampin, rifabutin, and rifapentine drug interactions

BACKGROUND

Rifampin is a potent inducer of both cytochrome P-450 oxidative enzymes and the P-glycoprotein transport system. Among numerous well documented, clinically significant interactions, examples include warfarin, oral contraceptives, itraconazole, digoxin, verapamil, simvastatin, and human immunodeficiency virus-related protease inhibitors. Rifabutin reduces serum concentrations of antiretroviral agents, but less so than rifampin. Rifapentine is also an inducer of drug metabolism.

METHODS

A literature search of English language journals from 2008 to March 2012 was completed using several databases, including PubMed, EMBASE, and SCOPUS. Search terms included rifampin, rifabutin, rifapentine AND drug interactions.

FINDINGS

Examples of clinically relevant interactions with rifampin demonstrated by recent reports include posaconazole, voriconazole, oxycodone, risperidone, mirodenafil, and ebastine.

CONCLUSIONS

To avoid a reduced therapeutic response, therapeutic failure, or toxic reactions when rifampin, rifabutin, or rifapentine are added to or discontinued from medication regimens, clinicians need to be aware of these interactions. Recent studies have indicated that other transporter systems play a role in these drug interactions. As reports of rifampin drug interactions continue to grow, this review is a reminder to clinicians to be vigilant.

Clinical Considerations for Roflumilast: A New Treatment for COPD

Chronic obstructive pulmonary disease (COPD) causes significant morbidity and mortality and represents the fourth leading cause of death in the world. Roflumilast is the first oral phosphodiesterase inhibitor indicated to reduce the risk of COPD exacerbations in patients with severe COPD associated with chronic bronchitis and history of exacerbations. Roflumilast and its active metabolite have been associated with increased cyclic adenosine monophosphate (cyclic AMP) in the lungs and positive responses with inflammatory markers. Significant improvements in forced expiratory volume (1 sec) have been observed in clinical trials comparing roflumilast with placebo. Combination therapy of roflumilast (500 μg) with long-acting beta agonists resulted in reduced COPD exacerbations in patients with severe COPD. Adverse effects include weight loss, diarrhea, nausea, and psychiatric disturbances. Roflumilast may be associated with significant drug-drug interactions with CYP3A4 inducers (strong) and immunosuppressants. Roflumilast is a promising new agent in the treatment of COPD; however, additional studies comparing roflumilast with inhaled corticosteroids plus long-acting bronchodilators are needed.

Roflumilast: A Novel Treatment for Chronic Obstructive Pulmonary Disease

Objective:

To evaluate the efficacy and safety of roflumilast, approved by the Food and Drug Administration in February 2011 as a treatment to reduce the risk of chronic obstructive pulmonary disease (COPD) exacerbations in patients with severe COPD associated with chronic bronchitis and a history of exacerbations.

Data Sources:

Literature was retrieved through MEDLINE (1977-December 2011), using the terms roflumilast and COPD. In addition, US government Web sites, including clinicaltrials.gov and fda.gov, were reviewed for pertinent information. Lastly, reference citations from publications identified were reviewed.

Study Selection and Data Extraction:

All articles published in English identified from the data sources were evaluated. For the evaluation of clinical efficacy and safety, only Phase 3 studies were included.

Data Synthesis:

Limited treatment options are available for patients with moderate-to-severe COPD and repeated exacerbations. In 6 published Phase 3 trials to date, roflumilast 500 μg daily exhibited modest improvements in lung function, measured by pre- and postbronchodilator forced expiratory volume in 1 second, and reduced rates of moderate and severe exacerbations. Roflumilast was generally well tolerated, with diarrhea, nausea, and headache the most common adverse events seen in clinical trials, although it has also been associated with an increased risk of neuropsychiatric abnormalities and dose-limiting weight loss. The greatest benefit seen with roflumilast was among patients with moderate-to-severe COPD associated with chronic bronchitis along with a recent history of exacerbations. The benefits were demonstrated with monotherapy and in combination with long-acting β2-agonists or anticholinergic agents.

Conclusions:

Despite its only modest benefits in improving lung function and reducing exacerbation rates, roflumilast serves as a safe and effective option in the treatment of COPD.

Roflumilast, a Novel Phosphodiesterase 4 Inhibitor, for COPD Patients with a History of Exacerbations

Acute exacerbations of COPD (AECOPD) are major clinical events. They are associated with a more rapid decline in lung function, poorer quality of life scores, and an increased risk of dying. Exacerbations that require hospitalization have particular significance. Approximately 40% of the AECOPD patients who require hospitalization will die in the subsequent year. Since many AECOPD require hospitalization, they account for most of the expense of caring for COPD patients. Treatment with long-acting bronchodilators and combination inhaled corticosteroid/long-acting bronchodilator inhalers reduces but does not eliminate AECOPD. Roflumilast, a selective phosphodiesterase 4 (PDE4) inhibitor, is an anti-inflammatory medication that improves lung function in patients with COPD. In patients with more severe airway obstruction, clinical features of chronic bronchitis, and a history of AECOPD, roflumilast reduces the frequency of AECOPD when given in combination with short-acting bronchodilators, long-acting bronchodilators, or inhaled corticosteroids. It is generally well tolerated but the most common adverse effects include diarrhea, nausea, weight loss, and headaches. In clinical trials, patients treated with roflumilast experienced weight loss that averaged just over 2 kg but was primarily due to the loss of fat tissue. Weight loss was least in underweight patients and obese patients experienced the greatest weight loss. An unexpected benefit of treatment with roflumilast was that fasting blood glucose and hemoglobin A1c levels improved in patients with comorbid type 2 diabetes mellitus. Roflumilast, the first selective PDE4 inhibitor to be marketed, is a promising drug for the management of COPD patients with more severe disease.

Roflumilast

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The August 2011 monograph topics are on fidaxomicin, boceprevir, telaprevir, rilpivirine hydrochloride, and gabapentin enacarbil. The DUE/MUE is on fidaxomicin.

No relevant cardiac, pharmacokinetic or safety interactions between roflumilast and inhaled formoterol in healthy subjects: an open-label, randomised, actively controlled study

BACKGROUND

Roflumilast is an oral, selective phosphodiesterase 4 inhibitor with anti-inflammatory effects in chronic obstructive pulmonary disease (COPD). The addition of roflumilast to long-acting bronchodilators improves lung function in patients with moderate-to-severe COPD. The present study investigated drug-drug interaction effects between inhaled formoterol and oral roflumilast.

METHODS

This was a single-centre (investigational clinic), open, randomised, multiple-dose, parallel-group study. In Regimen A, healthy men were treated with roflumilast (500 μg tablet once daily; Day 2-18) and concomitant formoterol (24 μg twice daily; Day 12-18). In Regimen B, healthy men were treated with formoterol (24 μg twice daily; Day 2-18) and concomitant roflumilast (500 μg once daily; Day 9-18). Steady-state plasma pharmacokinetics of roflumilast, roflumilast N-oxide and/or formoterol (Cmax and AUC0-τ) as well as pharmacodynamics - blood pressure, transthoracic impedance cardiography (ZCG), 12-lead digital electrocardiography, peripheral blood eosinophils, and serum glucose and potassium concentrations - were evaluated through Day 1 (baseline), Day 8 (Regimen B: formoterol alone) or Day 11 (Regimen A: roflumilast alone), and Day 18 (Regimen A and B: roflumilast plus formoterol). Blood and urine samples were taken for safety assessment at screening, pharmacokinetic profiling days and Day 19. Adverse events were monitored throughout the study.

RESULTS

Of the 27 subjects enrolled, 24 were evaluable (12 in each regimen). No relevant pharmacokinetic interactions occurred. Neither roflumilast nor formoterol were associated with significant changes in cardiovascular parameters as measured by ZCG, and these parameters were not affected during concomitant administration. Formoterol was associated with a slight increase in heart rate and a corresponding shortening of the QT interval, without changes in the heart rate-corrected QTc interval. There were small effects on the other pharmacodynamic assessments when roflumilast and formoterol were administered individually, but no interactions or safety concerns were seen after concomitant administration. No severe or serious adverse events were reported, and no adverse events led to premature study discontinuation.

CONCLUSIONS

No clinically relevant pharmacokinetic or pharmacodynamic interactions were found when oral roflumilast was administered concomitantly with inhaled formoterol, including no effect on cardiac repolarisation. Roflumilast was well tolerated.

Update on roflumilast, a phosphodiesterase 4 inhibitor for the treatment of chronic obstructive pulmonary disease

Phosphodiesterase 4 (PDE4) is a member of the PDE enzyme superfamily that inactivates cyclic adenosine monophosphate and cyclic guanosine monophosphate, and is the main PDE isoenzyme occurring in cells involved in inflammatory airway disease such as chronic obstructive pulmonary disease (COPD). COPD is a preventable and treatable disease and is characterized by airflow obstruction that is not fully reversible. Chronic progressive symptoms, particularly dyspnoea, chronic bronchitis and impaired overall health are worse in those who have frequent, acute episodes of symptom exacerbation. Although several experimental PDE4 inhibitors are in clinical development, roflumilast, a highly selective PDE4 inhibitor, is the first in its class to be licensed, and has recently been approved in several countries for oral, once-daily treatment of severe COPD. Clinical trials have demonstrated that roflumilast improves lung function and reduces exacerbation frequency in COPD. Furthermore, its unique mode of action may offer the potential to target the inflammatory processes underlying COPD. Roflumilast is effective when used concomitantly with all forms of bronchodilator and even in patients treated with inhaled corticosteroids. Roflumilast thus represents an important addition to current therapeutic options for COPD patients with chronic bronchitis, including those who remain symptomatic despite treatment. This article reviews the current status of PDE4 inhibitors, focusing on the pharmacokinetics, efficacy and safety of roflumilast. In particular, it provides an overview of the effects of roflumilast on lung function and exacerbations, glucose homoeostasis and weight loss, and the concomitant use of long-acting beta(2)-adrenergic receptor agonists and short-acting muscarinic receptor antagonists.

Roflumilast for the treatment of chronic obstructive pulmonary disease

Roflumilast is a new phosphodiesterase 4 inhibitor that has recently completed Phase III trials for the treatment of chronic obstructive pulmonary disease (COPD). Preclinical studies have shown that roflumilast targets inflammatory processes in COPD, with beneficial effects on tobacco-induced lung inflammation, lung fibrosis and remodeling, mucociliary malfunction and oxidative stress. Two recent, 1-year Phase III trials in COPD have shown that roflumilast reduces exacerbations and improves lung function in patients with COPD who have symptoms of chronic bronchitis and a history of exacerbations. Two other 6-month Phase III trials have demonstrated the beneficial effects of roflumilast in patients already receiving treatment with the long-acting &#x03B2;-agonist salmeterol or the long-acting muscarinic antagonist tiotropium. This article reviews the pharmacology, pharmacokinetics and preclinical pharmacology of roflumilast, the clinical studies supporting its use in COPD and its side-effect profile.

Pharmacology, clinical efficacy, and tolerability of phosphodiesterase-4 inhibitors: impact of human pharmacokinetics

Since more than two decades anti-inflammatory effects of inhibitors of phosphodiesterase-4 have been described in numerous cellular and animal studies and were finally confirmed in clinical trials. The path from an early, pioneering study with Ro20-1724 showing reduction of psoriatric plaque size in 1979 to modern PDE4 inhibitors such as oral apremilast in development for psoriasis, the inhaled PDE4 inhibitor GSK256066 in development for asthma and COPD and finally roflumilast, the first PDE4 inhibitor approved and currently marketed as an oral, once-daily remedy for severe COPD was marked by large progress in chemical optimization based on improved understanding of PDE4 biology and drug-like properties determining the appropriate pharmacokinetic profile. In this chapter aspects of the pharmacology and clinical efficacy of PDE4 inhibitors, which have been in clinical development over the years are summarized with specific emphasis on their clinical pharmacokinetic properties.

Pharmacokinetic drug interactions with vandetanib during coadministration with rifampicin or itraconazole

BACKGROUND

Vandetanib, an inhibitor of vascular endothelial growth factor receptor 2 (VEGFR-2), epidermal growth factor receptor (EGFR), and rearranged during transfection (RET), is a developmental oncology drug, that is in part metabolized by cytochrome P450 (CYP) 3A4. Clinical studies were performed to assess the potential for 3A4 inhibitors and inducers to affect exposure to vandetanib.

OBJECTIVE

The aim of this study was to investigate the effects of a potent CYP3A4 inducer, rifampicin (Study A), and a potent CYP3A4 inhibitor, itraconazole (Study B), on the pharmacokinetics of a single 300 mg dose of vandetanib in healthy subjects.

STUDY DESIGN AND SETTING

Two phase I, randomized, open-label, two-way crossover, single-center studies.

PARTICIPANTS AND INTERVENTION

Study A: 18 healthy male subjects aged 21-44 years were randomized to receive each of the following two regimens, separated by a ≥6-week washout period: (i) oral rifampicin 600 mg/day on days 1-31 with a single oral dose of vandetanib 300 mg on day 10; and (ii) a single oral dose of vandetanib 300 mg on day 1. Study B: 16 healthy male subjects aged 20-44 years were randomized to receive each of the following two regimens, separated by a 3-month washout period: (i) oral itraconazole 200 mg/day on days 1-24 with a single oral dose of vandetanib 300 mg on day 4; and (ii) a single oral dose of vandetanib 300 mg on day 1.

MAIN OUTCOME MEASURE

Blood samples for measurement of vandetanib (both studies) concentrations and its metabolites, N-desmethylvandetanib and vandetanib N-oxide (Study A only), were collected before and at various timepoints after vandetanib administration for up to 28 days (Study A) and 37 days (Study B). Pharmacokinetic parameters were determined using non-compartmental methods. The area under the plasma concentration-time curve from time 0 to 504 hours (AUC(504)) and maximum plasma concentration (C(max)) of vandetanib were compared in the presence and absence of rifampicin, and in the presence and absence of itraconazole.

RESULTS

Study A: coadministration of vandetanib with rifampicin resulted in a statistically significant reduction in AUC(504) (geometric least square [GLS]mean ratio [vandetanib + rifampicin/vandetanib alone] 0.60; 90% CI 0.58, 0.63). There was no significant difference in C(max) of vandetanib (GLSmean ratio 1.03; 90% CI 0.95, 1.11). AUC(504) and C(max) of N-desmethylvandetanib increased by 266.0% and 414.3%, respectively, in the presence of rifampicin compared with vandetanib alone. Exposure to vandetanib N-oxide was very low compared with that of vandetanib, but was increased in the presence of rifampicin. Study B: coadministration of vandetanib with itraconazole resulted in a significant increase in AUC(504) (GLSmean ratio [vandetanib + itraconazole/vandetanib alone] 1.09; 90% CI 1.01, 1.18) and no significant change in C(max) (GLSmean ratio 0.96; 90% CI 0.83, 1.11). Vandetanib was well tolerated in both studies.

CONCLUSIONS

Exposure to vandetanib, as assessed by AUC(504) in healthy subjects, was reduced by around 40% when a single dose was given in combination with the potent CYP3A4 inducer rifampicin. Because of this, it may be appropriate to avoid coadministration of potent CYP3A4 inducers with vandetanib. Vandetanib exposure was increased by about 9% when it was taken in combination with the CYP3A4 inhibitor itraconazole. It is unlikely that coadministration of vandetanib and potent CYP3A4 inhibitors will need to be contraindicated.

Population pharmacokinetic modelling of roflumilast and roflumilast N-oxide by total phosphodiesterase-4 inhibitory activity and development of a population pharmacodynamic-adverse event model

BACKGROUND

Roflumilast is an oral, selective phosphodiesterase (PDE)-4 inhibitor in development for the treatment of chronic obstructive pulmonary disease (COPD). Both roflumilast and its metabolite roflumilast N-oxide have anti-inflammatory properties that contribute to overall pharmacological activity.

OBJECTIVES

To model the pharmacokinetics of roflumilast and roflumilast N-oxide, evaluate the influence of potential covariates, use the total PDE4 inhibitory activity (tPDE4i) concept to estimate the combined inhibition of PDE4 by roflumilast and roflumilast N-oxide, and use individual estimates of tPDE4i to predict the occurrence of adverse events (AEs) in patients with moderate-to-severe COPD.

METHODS

We modelled exposure to roflumilast and roflumilast N-oxide (21 studies provided the index dataset and five separate studies provided the validation dataset), extended the models to COPD (using data from two studies) and assessed the robustness of the parameter estimates. A parametric bootstrap estimation was used to quantify tPDE4i in subpopulations. We established logistic regression models for each AE occurring in >2% of patients in a placebo-controlled trial that achieved a p-value of <0.2 in a permutation test. The exposure variables were the area under the plasma concentration-time curve (AUC) of roflumilast, the AUC of roflumilast N-oxide and tPDE4i. Individual AUC values were estimated from population models.

RESULTS

Roflumilast pharmacokinetics were modelled with a two-compartment model with first-order absorption including a lag time. A one-compartment model with zero-order absorption was used for roflumilast N-oxide. The final models displayed good descriptive and predictive performance with no appreciable systematic trends versus time, dose or study. Posterior predictive checks and robustness analysis showed that the models adequately described the pharmacokinetic parameters and the covariate effects on disposition. For roflumilast, the covariates of sex, smoking and race influenced clearance; and food influenced the absorption rate constant and lag time. For roflumilast N-oxide, age, sex and smoking influenced clearance; age, sex and race influenced the fraction metabolized; bodyweight influenced the apparent volume of distribution; and food influenced the apparent duration of formation. The COPD covariate increased the central volume of distribution of roflumilast by 184% and reduced its clearance by 39%; it also reduced the estimated volume of distribution of roflumilast N-oxide by 21% and reduced its clearance by 7.9%. Compared with the reference population (male, non-smoking, White, healthy, 40-year-old subjects), the relative geometric mean [95% CI] tPDE4i was higher in patients with COPD (12.6% [-6.6, 35.6]), women (19.3% [8.2, 31.6]), Black subjects (42.1% [16.4, 73.4]), Hispanic subjects (28.2% [4.1, 57.9]) and older subjects (e.g. 8.3% [-11.2, 32.2] in 60-year-olds), and was lower in smokers (-19.1% [-34.0, -0.7]). Among all possible subgroups in this analysis, the subgroup with maximal tPDE4i comprised elderly, Black, female, non-smoking, COPD patients (tPDE4i 217% [95% CI 107, 437] compared with the value in the reference population). The probability of a patient with tPDE4i at the population geometric mean [95% CI] was 13.0% [7.5, 18.5] for developing diarrhoea, 6.0% [2.6, 9.4] for nausea and 5.1% [1.9, 8.6] for headache.

CONCLUSIONS

Covariate effects have a limited impact on tPDE4i. There was a general association between tPDE4i and the occurrence of common AEs in patients with COPD.

Roflumilast: first phosphodiesterase 4 inhibitor approved for treatment of COPD

In April 2010, the European Medicines Agency Committee for Medicinal Products for Human Use recommended approval of roflumilast, a selective phosphodiesterase 4 inhibitor, for the “maintenance treatment of severe chronic obstructive pulmonary disease (COPD, FEV₁ postbronchodilator less than 50% predicted) associated with chronic bronchitis in adult patients with a history of frequent exacerbations as add-on to bronchodilator treatment”. This decision was based, in part, on the results of several large, international, multicenter, randomized, placebo-controlled trials of either six or 12 months’ duration that had been undertaken in COPD patients. Roflumilast 500 μg daily improved lung function and reduced exacerbations in patients with more severe COPD, especially those with chronic bronchitis, frequent exacerbations, or who required frequent rescue inhaler therapy in the placebo-controlled trials. It also improved lung function and reduced exacerbations in patients with moderately severe COPD treated with salmeterol or tiotropium. Advantages of roflumilast over inhaler therapy are that it is an oral tablet and only needs to be taken once daily. While taking roflumilast, the most common adverse effects patients experienced were gastrointestinal upset and headache. Weight loss, averaging 2.2 kg, occurred in patients treated with roflumilast. Patients taking roflumilast were more likely to drop out of the trials than patients in the control groups. Patients who discontinued therapy usually did so during the first few weeks and were more likely to have experienced gastrointestinal side effects. Roflumilast is the first selective phosphodiesterase 4 inhibitor and will offer physicians another treatment option for patients with more severe COPD.

No dose adjustment on coadministration of the PDE4 inhibitor roflumilast with a weak CYP3A, CYP1A2, and CYP2C19 inhibitor: an investigation using cimetidine

This nonrandomized, fixed-sequence, 2-period crossover study investigated potential pharmacokinetic interactions between the phosphodiesterase 4 inhibitor roflumilast, currently in clinical development for the treatment of chronic obstructive pulmonary disease, and the histamine 2 agonist cimetidine. Participants received roflumilast, 500 µg once daily, on days 1 and 13. Cimetidine, 400 mg twice daily, was administered from days 6 to 16. Pharmacokinetic analysis of roflumilast and its active metabolite roflumilast N-oxide was performed, and the ratio of geometric means for roflumilast alone and concomitantly with steady-state cimetidine was calculated. The effect of cimetidine on the total PDE4 inhibitory activity (tPDE4i; total exposure to roflumilast and roflumilast N-oxide) was also calculated. Coadministration of steady-state cimetidine increased mean tPDE4i of roflumilast and roflumilast N-oxide by about 47%. The maximum plasma concentration (C(max)) of roflumilast increased by about 46%, with no effect on C(max) of roflumilast N-oxide. The increase in tPDE4i of roflumilast and roflumilast N-oxide following coadministration with cimetidine was mainly due to the inhibitory effect of cimetidine on cytochrome P450 (CYP) isoenzymes CYP1A2, CYP3A, and CYP2C19. These moderate changes indicate that dose adjustment of roflumilast is not required when coadministered with a weak inhibitor of CYP1A2, CYP3A, and CYP2C19, such as cimetidine.