Anti-TNF Thioester Glucocorticoid Antibody-Drug Conjugate Fully Inhibits Inflammation with Minimal Effect on Systemic Corticosterone Levels in a Mouse Arthritis Model

We describe the discovery of a thioester-containing glucocorticoid receptor modulator (GRM) payload and the corresponding antibody-drug conjugate (ADC). Payload 6 was designed for rapid hepatic inactivation to minimize systemic exposure of nonconjugated GRM. Mouse PK indicated that 6 is cleared 10-fold more rapidly than a first-generation GRM payload, resulting in 10-fold lower exposure and 3-fold decrease in Cmax. The anti-mTNF conjugate ADC5 fully inhibited inflammation in mouse contact hypersensitivity with minimal effects on corticosterone, a biomarker for systemic GRM effects, at doses up to and including 100 mg/kg. Concomitant inhibition of P1NP suggests potential delivery to cells involved in the remodeling of bone, which may be a consequence of TNF-targeting or bystander payload effects. Furthermore, ADC5 fully suppressed inflammation in collagen-induced arthritis mouse model after one 10 mg/kg dose for 21 days. The properties of the anti-hTNF conjugate were suitable for liquid formulation and may enable subcutaneous dosing.

Biochemical Behaviours of Salmeterol/Fluticasone Propionate in Treating Asthma and Chronic Obstructive Pulmonary Diseases (COPD)

Chronic obstructive pulmonary diseases (COPD) and asthma are fatal. The respiratory tract may be blocked, robbed of the adequate amounts of oxygen; hence, death ensues if a quick medical attention is not provided. The treatment available for the duo are inhaled corticosteroids (ICS). The ICS can work synergically with LABAS (long-acting β 2-antagonists) and so many other medicines like bronchodilators. The drugs used for the treatment of asthma and COPD are metabolised once in the body system and at the same time exerting the therapeutic effect provided the concentration of the drug is within the therapeutic window. The CYP3A isoforms metabolise the ICS, in this case, salmeterol and fluticasone propionate (FP). Methods of administration are not limited to inhalation. Specific doses are prescribed accurately paying attention to factors like age, gender, race, and genetic makeup since these affect drug metabolisms. Generally, the ICS work by translocating glucocorticoid receptors to the nucleus from the cytosol. The mechanism is potentiated by the β-antagonists and this brings about an anti-inflammatory effect which is greater than either of the two drugs alone. Once this happens, it is not necessary to increase ICS dose. The ICS, in addition, cause more production of β-receptors by activating the β-receptor genes. This mode of action begets the LABAs' bronchodilator-effects. The challenge is that ICS are not limited only to "double" therapy. Analysing such therapies is daunting since coadministration interferes with pharmacology and pharmacokinetics of drugs. This work focuses on salmeterol/fluticasone propionate combination and aspects which has to do with administration, monitoring, metabolism, toxicity, and adverse effects.

Drug metabolism in severe chronic obstructive pulmonary disease: A phenotyping cocktail study

AIMS

To evaluate the effect of severe chronic obstructive pulmonary disease (COPD) on drug metabolism by comparing the pharmacokinetics of patients with severe COPD with healthy volunteers and using the modified Inje drug cocktail.

METHODS

This was a single-centre pharmacokinetic study with 12 healthy participants and 7 participants with GOLD D COPD. Midazolam 1 mg, dextromethorphan 30 mg, losartan 25 mg, omeprazole 20 mg, caffeine 130 mg and paracetamol 1000 mg were simultaneously administered and intensive pharmacokinetic sampling was conducted over 8 hours. Drug metabolism by CYP3A4, CYP2D6, CYP2C9, CYP2C19, CYP1A2, UGT1A6 and UGT1A9 in participants with COPD were compared with phenotypes in healthy controls.

RESULTS

The oral clearance (95% confidence interval) in participants with COPD relative to controls was: midazolam 63% (60-67%); dextromethorphan 72% (40-103%); losartan 53% (52-55%); omeprazole 35% (31-39%); caffeine 52% (50-53%); and paracetamol 73% (72-74%). There was a 5-fold increase in AUC for omeprazole and approximately 2-fold increases for caffeine, losartan, dextromethorphan, and midazolam. The AUC of paracetamol, which is mostly glucuronidated, was increased by about 60%.

CONCLUSION

Severe COPD is associated with a clinically significant reduction in oral drug clearance. This may be greater for cytochrome P450 substrates than for glucuronidated drugs. This supports reduced starting doses when prescribing for patients with severe COPD.

Metabolic and Pharmaceutical Aspects of Fluorinated Compounds

The applications of fluorine in drug design continue to expand, facilitated by an improved understanding of its effects on physicochemical properties and the development of synthetic methodologies that are providing access to new fluorinated motifs. In turn, studies of fluorinated molecules are providing deeper insights into the effects of fluorine on metabolic pathways, distribution, and disposition. Despite the high strength of the C-F bond, the departure of fluoride from metabolic intermediates can be facile. This reactivity has been leveraged in the design of mechanism-based enzyme inhibitors and has influenced the metabolic fate of fluorinated compounds. In this Perspective, we summarize the literature associated with the metabolism of fluorinated molecules, focusing on examples where the presence of fluorine influences the metabolic profile. These studies have revealed potentially problematic outcomes with some fluorinated motifs and are enhancing our understanding of how fluorine should be deployed.

Evaluating fluticasone furoate + vilanterol for the treatment of chronic obstructive pulmonary disease (COPD)

INTRODUCTION

Inhaled corticosteroid/long-acting β-2 agonists (ICS/LABA) combination inhalers have been a lifeline for a generation of chronic obstructive pulmonary disease (COPD) and asthma patients. Fluticasone furoate and Vilanterol (FF/VI) as a once-daily ICS/LABA combination have an extensive clinical trial and real-world data to support its use in COPD patients. Areas covered: The authors provide pharmacological profiles of fluticasone furoate, vilanterol and the FF/VI fixed dose combination. Salient clinical trials evaluating efficacy and safety of the FF/VI combination, and studies demonstrating the impact on COPD exacerbation risk and mortality are also discussed. Expert opinion: ICS/LABA combinations provide bronchodilation and decrease the frequency of COPD exacerbations. Individualizing treatment of each COPD patient based on unique phenotypes will maximize chances of therapeutic responsiveness. Asthma-COPD overlap (ACO), patients with sputum and/or blood eosinophilia, patients with a brisk bronchodilator response, and patients with frequent exacerbations are more likely to show a therapeutic response to ICS than populations who have none of these features. FF/VI will likely remain a popular ICS/LBA combination to treat COPD, as a once-daily inhaled therapy delivered via the Ellipta device popular with COPD patients, with extensive clinical trial and real-world data to support its use.

Pharmacokinetics of Single and Repeat Doses of Fluticasone Furoate/Umeclidinium/Vilanterol in Healthy Chinese Adults

The pharmacokinetics (PK) and safety of single-inhaler fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) after single and repeat dosing in healthy Chinese adults were assessed. In this open-label study (NCT02837380), subjects received once-daily FF/UMEC/VI 100/62.5/25 µg on day 1 and repeat doses on days 2-7. PK parameters (days 1 and 7) included maximum observed concentration (C_max ) and area under the plasma concentration-time curve (AUC) from time zero (predose) to last time of quantifiable concentration (AUC_0-t ). Terminal phase half-life (t_½ ) on day 1 was estimated. The primary objective was to assess systemic exposure of FF 100 µg, UMEC 62.5 µg, and VI 25 µg following single-inhaler triple therapy on days 1 and 7. On day 1, geometric mean t_½ of UMEC and VI was 0.36 and 0.52 hours, respectively; t_½ of FF was not representative because of nonquantifiable concentration data. On days 1 and 7, geometric mean C_max of FF was 10.46 and 27.32 pg/mL, respectively; C_max of UMEC was 144.14 and 241.35 pg/mL, respectively; and C_max of VI was 120.42 and 196.78 pg/mL, respectively. AUC_0-t of FF was 1.77 and 276.96 pg·h/mL, respectively; AUC_0-t of UMEC was 28.44 and 117.19 pg·h/mL, respectively; and AUC_0-t of VI, 42.46 and 101.12 pg·h/mL, respectively. The PK of FF/UMEC/VI was as expected for the individual-component PK previously reported in healthy Chinese adults. No new safety signals were observed.

Open-Label, Crossover Study to Determine the Pharmacokinetics of Fluticasone Furoate and Batefenterol When Administered Alone, in Combination, or Concurrently

The study aim was to investigate the pharmacokinetics of single high doses and repeated therapeutic doses of fluticasone furoate (FF) and batefenterol (BAT; a bifunctional muscarinic antagonist and β₂ -agonist) administered in combination (BAT/FF) or as monotherapy. In this open-label, 6-period, crossover study of 48 subjects, the treatment sequences were (1) single high-dose BAT/FF 900/300 μg followed by repeated therapeutic doses of BAT/FF 300/100 μg (once daily for 7 days); (2) single high-dose BAT 900 μg administered concurrently with FF 300 μg; (3) single high-dose BAT 900 μg followed by repeated therapeutic-dose BAT 300 μg; (4) single high-dose FF 300 μg followed by repeated therapeutic-dose FF 100 μg; (5) single high-dose FF 300 μg (magnesium stearate); and (6) single high-dose FF/vilanterol 300/75 μg. Plasma FF area under the plasma drug concentration-time curve (AUC) was reduced after single high-dose BAT/FF versus FF alone (ratio of geometric least squares means: 0.79; 90% confidence interval: 0.75-0.83). After repeat dosing, FF AUC at the lower therapeutic dosage was similar for BAT/FF and FF (primary endpoint; AUC geometric least squares means: 1.03). Adverse events were minor, the most common being cough. These data support the feasibility of developing BAT/inhaled corticosteroid triple therapy in a single inhaler.

Selective Nonsteroidal Glucocorticoid Receptor Modulators for the Inhaled Treatment of Pulmonary Diseases

A class of potent, nonsteroidal, selective indazole ether-based glucocorticoid receptor modulators (SGRMs) was developed for the inhaled treatment of respiratory diseases. Starting from an orally available compound with demonstrated anti-inflammatory activity in rat, a soft-drug strategy was implemented to ensure rapid elimination of drug candidates to minimize systemic GR activation. The first clinical candidate 1b (AZD5423) displayed a potent inhibition of lung edema in a rat model of allergic airway inflammation following dry powder inhalation combined with a moderate systemic GR-effect, assessed as thymic involution. Further optimization of inhaled drug properties provided a second, equally potent, candidate, 15m (AZD7594), that demonstrated an improved therapeutic ratio over the benchmark inhaled corticosteroid 3 (fluticasone propionate) and prolonged the inhibition of lung edema, indicating potential for once-daily treatment.

Pharmacokinetic Comparison of a Unit Dose Dry Powder Inhaler with a Multidose Dry Powder Inhaler for Delivery of Fluticasone Furoate

BACKGROUND

The unit dose dry powder inhaler (UD-DPI) is being considered as an alternative inhaler platform that, if developed, has the potential to improve access to inhaled respiratory medicines in developing countries.

AIM

This study compared the systemic exposure of fluticasone furoate after delivery from the UD-DPI with that from the ELLIPTA^® inhaler.

METHODS

This open-label, five-way cross-over, randomized, single-dose study in healthy subjects evaluated fluticasone furoate systemic exposure of three dose strengths (using four inhalations), 4 × 80 μg [320 μg], 4 × 100 μg [400 μg], and 4 × 140 μg [560 μg]), and two percentages of drug in lactose blends (0.6% and 0.8% by weight) after delivery from the UD-DPI compared with systemic exposures from the ELLIPTA inhaler (4 × 100 μg [400 μg] dose, 0.8% lactose blend). The primary treatment comparisons were area under the concentration-time curve from time 0 to 6 hours [AUC_0-6] and maximum plasma concentration [C_max].

RESULTS

After single-dose administration of fluticasone furoate, systemic exposure was lower from all UD-DPI formulations versus the ELLIPTA inhaler in terms of both AUC_0-6 [AUC_0-6 geometric least squares mean (GLM) ratios confidence interval (90% CI) for: UD-DPI (400 μg 0.8% blend)/ELLIPTA: 0.61 (0.55-0.67) and C_max GLM (90% CI) for: UD-DPI (400 μg 0.8% blend)/ELLIPTA: 0.56 (0.49-0.64)]. Systemic exposures were ∼10% lower for fluticasone furoate UD-DPI for the 0.8% blend versus the 0.6% blend [GLM ratio (90% CI); 0.90 (0.81-1.00) for AUC_0-6 and 0.89 (0.77-1.01) for C_max], and increasing doses of fluticasone furoate from the UD-DPI showed systemic exposures that were approximately dose proportional. All treatments were well tolerated.

CONCLUSIONS

Fluticasone furoate systemic exposure was lower from the UD-DPI than from the ELLIPTA inhaler, but the UD-DPI formulations did demonstrate detectable systemic levels and approximate dose proportionality. Together with the good tolerability shown, these data support further evaluation of the UD-DPI as a potential device for delivering inhaled respiratory drugs.

Spotlight on fluticasone furoate/vilanterol trifenatate for the once-daily treatment of asthma: design, development and place in therapy

The use of inhaled corticosteroids (ICSs) plays a key role in the treatment of asthmatic patients, and international guidelines have designated ICSs as an early maintenance therapy in controlling asthma symptoms. When asthmatic patients remain symptomatic on ICSs, one common option is to add a long-acting beta₂ agonist (LABA) to the maintenance treatment. Fixed combination inhalers that contain both an ICS and a LABA have been popular for both chronic obstructive pulmonary disease (COPD) and asthma. Historically, these inhalers have been dosed twice daily. However, currently, there is a once-daily combination therapy with the ICS fluticasone furoate (FF) and the LABA vilanterol trifenatate (VI) with indications for use in both COPD and asthma. This dry powder inhaler (DPI) comes in two doses of FF (100 or 200 μg) both combined with VI (25 μg). This article reviews the clinical trial data for FF, VI and FF/VI combination inhalers and documents the efficacy and safety of once-daily inhaled maintenance therapy by DPI in asthmatic patients.

Phamacology of fluticasone furoate and vilanterol trifenatate combination therapy for asthma

INTRODUCTION

Fluticasone furoate (FF) is a novel inhaled corticosteroid (ICS). Vilanterol trifenate (VI) is a new inhaled, selective, long - acting β2 adrenergic agonist (LABA). It is now also marketed as a novel once daily combined ICS/LABA indicated for treatment of moderate and severe asthma.

AREAS COVERED

FF has a highly specific, fast association and slow dissociation from the glucocorticoid receptor, with a 24 hr duration of action. This, combined with a slow transport out of respiratory cells, creates a long tissue retention period. Vilanterol trifenate (VI) is a new inhaled, selective, long - acting β2 adrenergic agonist, also with a rapid onset of action with a maximal effect within 6 mins and prolonged lung retention with effects on lung function over 24 hours. Expert commentary: Multiple Phase I-III efficacy studies performed on FF and VI have shown an improvement in spirometry as well as symptom control in asthma. The development of once daily ICS/LABA combinations may potentially improve adherence to asthma therapy, but this has yet to be demonstrated.

Pharmacodynamic and pharmacokinetic assessment of fluticasone furoate + vilanterol for the treatment of asthma

INTRODUCTION

The pharmacokinetic (PK) and pharmacodynamic (PD) effects of long-acting β2-agonists and mostly inhaled corticosteroids (ICSs) shape the efficacy and safety of these agents in the treatment of asthma. In fact, the PK and PD characteristics of the drug largely determine the degree of pulmonary targeting Areas covered. In this review, we summarize the PK and PD properties of inhaled fluticasone furoate (FF) and vilanterol trifenatate (VI) and their fixed-dose combination (FDC) for the treatment of asthma Expert opinion. It is difficult to interpret the data that we have described because the preclinical and clinical development of FF/VI FDC was not really based on solid information on quantitative PK/PD approach. Unfortunately, for both FF and VI we only know concentrations in systemic blood, a compartment that is downstream of both target and non-target respiratory tissue. This lack of information does not allow us to understand the temporal relationship between the delivered dose and the drug concentration at the sites of action within the lungs. In addition, all studies performed with FF and VI did not address the fundamental issue that asthma can significantly alter lung deposition, absorption and also clearance of inhaled medicines.

Fluticasone furoate/vilanterol: a review of its use in patients with asthma

Fluticasone furoate/vilanterol (Relvar(®)) is a once-daily, fixed combination of an inhaled corticosteroid (ICS) and a long-acting β2-adrenoreceptor agonist (LABA), delivered via a dry powder inhaler (Ellipta(®)). It is approved for the treatment of asthma in the EU and Japan, and is the first once-daily ICS/LABA to be available for this indication. Fluticasone furoate is an enhanced-affinity glucocorticoid receptor agonist, with potent anti-inflammatory activity. Vilanterol produces rapid and prolonged bronchodilation. In phase III trials in adolescents and adults with various levels of asthma uncontrolled on ICS and/or ICS/LABA, fluticasone furoate/vilanterol 100/25 or 200/25 µg once daily (approved dosages in the EU) significantly improved pulmonary function compared with placebo or equivalent dosages of fluticasone furoate alone (in some trials) or fluticasone propionate. In similar trials, fluticasone furoate/vilanterol 100/25 µg once daily was as effective as fluticasone propionate/salmeterol 250/50 µg twice daily in improving pulmonary function and significantly reduced the risk of severe asthma exacerbation relative to fluticasone furoate alone. In clinical trials, fluticasone furoate/vilanterol was generally well tolerated with fewer than 15 % of patients experiencing treatment-related adverse events, the most common of which were oral/oropharyngeal candidiasis, dysphonia, extrasystoles and cough. The tolerability profile of fluticasone furoate/vilanterol was generally similar to that of fluticasone propionate/salmeterol. Thus, fluticasone furoate/vilanterol is an effective and generally well tolerated ICS/LABA option for the treatment of uncontrolled asthma.

Human absorption, distribution, metabolism and excretion properties of drug molecules: a plethora of approaches

Human radiolabel studies are traditionally conducted to provide a definitive understanding of the human absorption, distribution, metabolism and excretion (ADME) properties of a drug. However, advances in technology over the past decade have allowed alternative methods to be employed to obtain both clinical ADME and pharmacokinetic (PK) information. These include microdose and microtracer approaches using accelerator mass spectrometry, and the identification and quantification of metabolites in samples from classical human PK studies using technologies suitable for non-radiolabelled drug molecules, namely liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. These recently developed approaches are described here together with relevant examples primarily from experiences gained in support of drug development projects at GlaxoSmithKline. The advantages of these study designs together with their limitations are described. We also discuss special considerations which should be made for a successful outcome to these new approaches and also to the more traditional human radiolabel study in order to maximize knowledge around the human ADME properties of drug molecules.

Fluticasone furoate/vilanterol: a review of its use in chronic obstructive pulmonary disease

Fluticasone furoate/vilanterol (Relvar(®), Breo(®), Revinty(®)) is a fixed combination of a corticosteroid and a long-acting β2-adrenergic agonist (LABA) for once-daily use via a dry powder inhaler (Ellipta(®)). Fluticasone furoate/vilanterol 100/25 µg is approved for the treatment of chronic obstructive pulmonary disease (COPD) in several countries. This article reviews the clinical use of the combination in COPD and summarises pharmacological properties. Fluticasone furoate has enhanced affinity for the glucocorticoid receptor compared with other clinically used inhaled corticosteroids (ICS) and longer lung retention than fluticasone propionate. Vilanterol is highly selective for β2-adrenoreceptors and provides a rapid and prolonged duration of action. In phase 3 trials in patients with moderate to very severe COPD, overall, once-daily fluticasone furoate/vilanterol 100/25 µg improved pulmonary function more than placebo and fluticasone furoate alone and improved exacerbation rates more than vilanterol alone. With regard to pulmonary function, once-daily fluticasone furoate/vilanterol 100/25 μg was more effective than twice-daily fluticasone propionate/salmeterol 250/50 µg and similarly effective as twice-daily fluticasone propionate/salmeterol 500/50 μg. In 12-month trials, fluticasone furoate/vilanterol was generally well tolerated, and in 12- and 24-week trials, the incidence of adverse events was similar overall to that associated with the individual components or fluticasone propionate/salmeterol. However, as with the long-term use of all ICS agents, 12-month data indicate an increase in the risk of pneumonia with fluticasone furoate/vilanterol. In conclusion, fluticasone furoate/vilanterol is an effective and generally well tolerated additional LABA/ICS agent for the treatment of COPD with the added convenience of once-daily administration, which may improve treatment adherence in some patients.

A repeat-dose thorough QT study of inhaled fluticasone furoate/vilanterol combination in healthy subjects

AIMS

This study was designed as a thorough QT (TQT) study to evaluate the effects of fluticasone furoate (FF)/vilanterol (VI) in healthy subjects. Supportive data from a TQT study conducted with FF are also presented.

METHODS

This was a randomized, placebo- and positive-controlled, double-dummy, double-blind, four-way crossover study, in which healthy subjects (n = 85) were randomized to 7 days of once-daily treatment of FF/VI (200/25 or 800/100 μg) or placebo or single-dose oral moxifloxacin (single-blind, 400 mg). In the supportive TQT study, subjects (n = 40) were randomized to single-dose inhaled FF (4000 μg), oral moxifloxacin (400 mg) or placebo.

RESULTS

There was a lack of effect of FF/VI (200/25 μg) on QTcF (Fridericia's correction); all time-matched mean differences from baseline relative to placebo (0-24 h) were <5 ms, with upper 90% confidence intervals (CI) of <10 ms. At 800/100 μg, FF/VI had no significant clinical effect on QTcF except at 30 min postdose when the 90% CI was >10 ms [mean (90% CI), 9.6 ms (7.2, 12.0)]. No effect on QTci (individually corrected) was observed at either strength of FF/VI, with mean time-matched treatment differences <5 ms at all time points [upper 90% CIs <10 ms (0-24 h)]. Assay sensitivity was confirmed; moxifloxacin prolonged QTcF and QTci, with time-matched mean differences from baseline relative to placebo of >10 ms (1-8 h postdose).

CONCLUSIONS

Repeat once-daily dosing of FF/VI (200/25 μg), which is the highest therapeutic strength used in phase III studies, is not associated with QTc prolongation in healthy subjects. Supratherapeutic strength FF/VI (800/100 μg) demonstrated a small transient effect on QTcF but not on QTci.

Pharmacokinetics and pharmacodynamics of intravenous and inhaled fluticasone furoate in healthy Caucasian and East Asian subjects

AIM

The aim of the study was to evaluate the pharmacokinetics (PK) of inhaled and intravenous (i.v.) fluticasone furoate (FF) in healthy Caucasian, Chinese, Japanese and Korean subjects.

METHOD

This was an open label, randomized, two way crossover study in healthy Caucasian, Chinese, Japanese and Korean subjects (n = 20 per group). Inhaled FF (200 μg for 7 days, then 800 μg for 7 days from a dry powder inhaler [DPI]) was administered in one treatment period and i.v.FF (250 μg infusion) in the other. FF PK and serum cortisol (inhaled 200 μg only) were compared between the ethnic groups using analysis of variance. P450 CYP3A4 activity and safety were also assessed.

RESULTS

Ethnic differences in i.v. FF PK were accounted for by body weight differences. CYP3A4 activity was similar across the groups. Higher FF systemic exposure was seen following inhaled dosing in Chinese, Japanese and Korean subjects compared with Caucasian subjects. Absolute bioavailability was greater (36%-55%) in all East Asian groups than for Caucasian subjects following inhaled FF 800 μg. Deconvolution analysis suggested inhaled FF resided in the lung of East Asian subjects longer than for Caucasians (time for 90% to be absorbed [t90]: 29.1-30.8 h vs. 21.4 h). In vitro simulation method predicted comparable delivered lung dose across ethnic groups. Serum cortisol weighted mean was similar between Caucasians and Chinese or Koreans, while in Japanese was on average 22% lower than in Caucasians. All FF treatments were safe and well tolerated.

CONCLUSION

Modestly higher (<50%) FF systemic exposure seen in East Asian subjects following inhaled dosing was not associated with a clinically significant effect on serum cortisol, suggesting that a clinical dose adjustment in East Asian subjects is not required.

Fluticasone furoate, a novel inhaled corticosteroid, demonstrates prolonged lung absorption kinetics in man compared with inhaled fluticasone propionate

Background

Fluticasone furoate (FF; GW685698) is a novel inhaled corticosteroid that is active at 24 h and under development for once-daily administration in combination with the long-acting β₂-adrenoceptor agonist vilanterol (GW642444) for chronic obstructive pulmonary disease and asthma. In vitro studies examining the respiratory tissue-binding properties of corticosteroids showed FF to have the largest cellular accumulation and slowest rate of efflux compared with other clinically used inhaled corticosteroids, consistent with greater tissue retention. The enhanced affinity of the glucocorticoid receptor binding of FF, coupled with its extended tissue association, may be expected to lead to greater and more prolonged anti-inflammatory effects and should provide relevant once-daily efficacy.

Objective

The aim of this study was to assess the rate and extent of systemic absorption of FF from the lung following inhaled administration of FF from three exploratory dry powder formulations (via DISKHALER^®) compared with inhaled fluticasone propionate (FP) [via DISKHALER^®] using deconvolution analysis.

Methods

This open-label, part-randomized, six-way crossover study evaluated three early development dry powder inhaled formulations of FF administered as single doses via DISKHALER^®. Healthy male subjects (n = 24) each received FF (2,000 μg; three formulations), inhaled FP (1,000 μg; via DISKHALER^®) and 250 μg of each molecule by intravenous infusion. The bioavailability of both inhaled FF and FP represents absorption from the lung as the oral bioavailability from the swallowed portion of the inhaled dose is negligible (<1.5 %). To investigate the absorption kinetics from the lung, the inhaled concentration–time data were subjected to deconvolution analysis using derived pharmacokinetic parameters from fitting of the intravenous concentration–time data.

Results

The terminal elimination half-life (t_½β) for inhaled FF was considerably longer (range 17–24 h) than the t_½β estimated for intravenous FF (14 h), whereas t_½β for FP was similar whether inhaled or given intravenously (11 and 14 h, respectively). This would suggest that FF is exhibiting absorption rate-limited pharmacokinetics following inhaled FF dosing and that the apparent t_½β is an estimate of absorption rate. The lung mean absorption time for FF was approximately 7 h irrespective of formulation, which was considerably longer than FP (2.1 h). The time for 90 % absorption from the lung was significantly longer for FF (20–30 h) than for FP (8 h), indicating a significantly longer lung retention time for FF.

Conclusion

In comparison with inhaled FP, inhaled FF (independent of formulation) demonstrated prolonged absorption from the lung into the systemic circulation, indicating a longer lung retention time and suggesting the potential for maintained efficacy with once-daily administration.

Inhaled corticosteroid use in HIV-positive individuals taking protease inhibitors: a review of pharmacokinetics, case reports and clinical management

As a consequence of inhibition of the hepatic cytochrome P450 3A4 isozyme, treatment with HIV protease inhibitors can result in significant drug-drug interactions. One noteworthy interaction is between protease inhibitors and inhaled or intranasal corticosteroids. This interaction can result in adrenal insufficiency and iatrogenic Cushing's syndrome (with symptoms such as rapid weight gain, obesity, facial hirsutism and swelling), as well as hypertension, osteoporosis and decreased CD4 cell count. In this paper, we review and unite pharmacokinetic data, case reports and current research regarding this drug-drug interaction in order to suggest options for the clinical management of HIV-positive patients requiring treatment with protease inhibitors and inhaled or intranasal corticosteroids.

Metabolism of beclomethasone dipropionate by cytochrome P450 3A enzymes

Inhaled glucocorticoids, such as beclomethasone dipropionate (BDP), are the mainstay treatment of asthma. However, ≈ 30% of patients exhibit little to no benefit from treatment. It has been postulated that glucocorticoid resistance, or insensitivity, is attributable to individual differences in glucocorticoid receptor-mediated processes. It is possible that variations in cytochrome P450 3A enzyme-mediated metabolism of BDP may contribute to this phenomenon. This hypothesis was explored by evaluating the contributions of CYP3A4, 3A5, 3A7, and esterase enzymes in the metabolism of BDP in vitro and relating metabolism to changes in CYP3A enzyme mRNA expression via the glucocorticoid receptor in lung and liver cells. CYP3A4 and CYP3A5 metabolized BDP via hydroxylation ([M4] and [M6]) and dehydrogenation ([M5]) at similar rates; CYP3A7 did not metabolize BDP. A new metabolite [M6], formed by the combined action of esterases and CYP3A4 hydroxylation, was also characterized. To validate the results observed using microsomes and recombinant enzymes, studies were also conducted using A549 lung and DPX2 liver cells. Both liver and lung cells produced esterase-dependent metabolites [M1-M3], with [M1] correlating with CYP3A5 mRNA induction in A549 cells. Liver cells produced both hydroxylated and dehydrogenated metabolites [M4, M5, and M6], but lung cells produced only the dehydrogenated metabolite [M5]. These studies show that CYP3A4 and CYP3A5 metabolize BDP to inactive metabolites and suggest that differences in the expression or function of these enzymes in the lung and/or liver could influence BDP disposition in humans.

Metabolic pathways of inhaled glucocorticoids by the CYP3A enzymes

Asthma is one of the most prevalent diseases in the world, for which the mainstay treatment has been inhaled glucocorticoids (GCs). Despite the widespread use of these drugs, approximately 30% of asthma sufferers exhibit some degree of steroid insensitivity or are refractory to inhaled GCs. One hypothesis to explain this phenomenon is interpatient variability in the clearance of these compounds. The objective of this research is to determine how metabolism of GCs by the CYP3A family of enzymes could affect their effectiveness in asthmatic patients. In this work, the metabolism of four frequently prescribed inhaled GCs, triamcinolone acetonide, flunisolide, budesonide, and fluticasone propionate, by the CYP3A family of enzymes was studied to identify differences in their rates of clearance and to identify their metabolites. Both interenzyme and interdrug variability in rates of metabolism and metabolic fate were observed. CYP3A4 was the most efficient metabolic catalyst for all the compounds, and CYP3A7 had the slowest rates. CYP3A5, which is particularly relevant to GC metabolism in the lungs, was also shown to efficiently metabolize triamcinolone acetonide, budesonide, and fluticasone propionate. In contrast, flunisolide was only metabolized via CYP3A4, with no significant turnover by CYP3A5 or CYP3A7. Common metabolites included 6β-hydroxylation and Δ(6)-dehydrogenation for triamcinolone acetonide, budesonide, and flunisolide. The structure of Δ(6)-flunisolide was unambiguously established by NMR analysis. Metabolism also occurred on the D-ring substituents, including the 21-carboxy metabolites for triamcinolone acetonide and flunisolide. The novel metabolite 21-nortriamcinolone acetonide was also identified by liquid chromatography-mass spectrometry and NMR analysis.

Fluticasone furoate nasal spray: Profile of an enhanced-affinity corticosteroid in treatment of seasonal allergic rhinitis

Of the classes of pharmacotherapy for seasonal allergic rhinitis, intranasal corticosteroids are the preferred treatment and are recommended in practice guidelines as first-line pharmacotherapy for rhinitis with prominent nasal congestion. The enhanced-affinity intranasal corticosteroid fluticasone furoate nasal spray (GW685698X), is one of the newest additions to the armamentarium for allergic rhinitis. This review summarizes the preclinical and clinical data on fluticasone furoate nasal spray and discusses its place in pharmacotherapy for seasonal allergic rhinitis. Important attributes of fluticasone furoate in seasonal allergic rhinitis include low systemic bioavailability (<0.5%), onset of symptom relief as early as eight hours after initiation of treatment, 24-hour symptom relief with once-daily dosing, comprehensive coverage of both nasal and ocular symptoms, safety and tolerability with daily use, and availability in a side-actuated device that makes medication delivery simple and consistent. With these attributes, fluticasone furoate nasal spray has the potential to enhance patient satisfaction and compliance and reduce the need for polypharmacy in the management of seasonal allergic rhinitis.

Pharmacokinetics in special populations

Pharmacokinetics are typically dependent on a variety of physiological variables (e.g., age, ethnicity, or pregnancy) or pathological conditions (e.g., renal and hepatic insufficiency, cardiac dysfunction, obesity, etc.). The influence of some of these conditions has not always been thoroughly assessed in the clinical studies of antiallergic drugs. However, the knowledge of the physiological grounds of the pharmacokinetics can provide some insight for predicting the potential alterations and guiding the initial prescription strategies. It is important to recognize that both pharmacokinetic and pharmacodynamic differences between populations should be considered. The available information on drugs used for the therapy of allergic diseases is reviewed in this chapter.

Drug metabolism and pharmacokinetics

In this article, aspects of absorption, distribution, metabolism, and excretion have been described bearing in mind the pathogenesis of allergic diseases and their possible therapeutic opportunities. The importance of the routes of administration of the different therapeutic groups has been emphasized. The classical aspects of drug metabolism and disposition related to oral administration have been reviewed, but special emphasis has been given to intranasal, cutaneous, transdermal, and ocular administration as well as to the absorption and the subsequent bioavailability of drugs. Drug-metabolizing enzymes and transporters present in extrahepatic tissues, such as nasal mucosa and the respiratory tract, have been particularly discussed. As marketed antiallergic drugs include both racemates and enantiomers, aspects of stereoselective absorption, distribution, metabolism, and excretion have been discussed. Finally, a new and promising methodology, microdosing, has been presented, although it has not yet been applied to drugs used in the treatment of allergic diseases.