Nifurtimox for Treatment of Chagas Disease in Pediatric Patients: the Challenges of Applying Pharmacokinetic-Pharmacodynamic Principles to Dose Finding.

The antiparasitic drug nifurtimox was approved in the USA in 2020 for the treatment of patients with Chagas disease aged less than 18 years and weighing at least 2.5 kg, based on outcomes from the phase 3 CHICO study. Accordingly, pediatric patients with Chagas disease take nifurtimox thrice daily with food at one of two body weight-adjusted dose ranges. We investigated possible relationships between pharmacokinetic (PK) data, and pharmacodynamic efficacy and safety data collected in an analysis population of 111 participants in CHICO, using a published population PK model to estimate nifurtimox exposure at the patient level. Pediatric exposure to nifurtimox was benchmarked against levels of nifurtimox exposure known to be effective in adults with Chagas disease. Given the complex dosing regimen for nifurtimox, we also modeled nifurtimox exposure associated with simpler dosing strategies. We found no relationship between exposure to nifurtimox and efficacy measures (e.g., serological response to treatment), or between exposure and safety outcomes (including typical adverse events, e.g., headache, decreased appetite, nausea/vomiting). The analysis population appeared to represent the overall CHICO population based on the similarity of their baseline characteristics and the profiles of adverse events in the two groups. Modeled exposure based on the dosing regimen in CHICO was within the reference range derived from phase 1 data in adults. The relationship between nifurtimox exposure and cure is complex; a simplified pediatric dosing regimen is unlikely to be beneficial.

Clinical investigation of the biopharmaceutical characteristics of nifurtimox tablets - Implications for quality control and application.

Nifurtimox is approved in Chagas disease and has been used in endemic countries since the 1960s. Nifurtimox, available as a 120 mg tablet, is administered with food typically three times daily, and dose is adjusted for age and bodyweight. Accurately or reproducibly fragmenting the 120 mg tablet for dose adjustment in young children and those with low bodyweight is problematic. Based on the existing tablet formulation, new nifurtimox 30 mg and 120 mg tablets have been developed in a format that can be divided accurately into 15 mg and 60 mg fragments. In adults with chronic Chagas disease, we investigated whether nifurtimox bioavailability is affected by tablet dissolution rate, and whether different diets affect nifurtimox bioavailability. In an open-label, three-period cross-over study (n=36; ClinicalTrials.gov, NCT03350295), patients randomly received three 30 mg tablet formulations (slow, medium, or fast dissolution; a 4 × 30 mg dose of one formulation per period). In an open-label, four-period cross-over study (n=24; ClinicalTrials.gov, NCT03334838) patients randomly fasted or received one of three meal types (high-fat/high-calorie, low-fat, dairy-based) before ingesting nifurtimox (a 4 × 30 mg dose per period). Acceptance criteria for no difference between groups were 90% confidence intervals (CIs) of exposure ratios in the range 0.8-1.25. Nifurtimox bioavailability was unaffected by tablet dissolution kinetics. Ratios of area under the curve at final assessment (AUC(0-tlast) [90% CI]) were: fast/medium dissolution, 1.061 (0.990-1.137); slow/medium dissolution, 0.964 (0.900-1.033); fast/slow dissolution, 1.100 (1.027-1.179). Compared with a fasting state, nifurtimox bioavailability increased by 73% after a high-fat/high-calorie meal (AUC(0-tlast) ratio [90% CI], 1.732 [1.581-1.898]); smaller increases were seen with the other meal types (low-fat: 1.602 [1.462-1.755]; dairy-based: 1.340 [1.222-1.468]). Although type of diet can affect bioavailability, taking nifurtimox with food is most important.

Biopharmaceutical Characteristics of Nifurtimox Tablets for Age- and Body Weight-Adjusted Dosing in Patients With Chagas Disease.

Treatment of Chagas disease with nifurtimox requires age- and body weight-adjusted dosing, resulting in complex dosing instructions. Appropriate formulations are needed for precise and compliant dosing, especially in pediatric patients. We characterized the biopharmaceutical features of a standard nifurtimox 120-mg tablet and a 30-mg tablet developed to improve dose accuracy. Two open-label, randomized crossover studies were conducted in adult outpatients with Chagas disease. One study investigated whether 4 × 30-mg tablets and 1 × 120-mg tablet were bioequivalent and whether tablets can be administered as an aqueous slurry without affecting bioavailability. The second study investigated the effect of a high-calorie/high-fat diet versus fasting on the absorption of nifurtimox after a single 4 × 30-mg dose. Interventions were equivalent if the 90% confidence interval (CI) of their least-squares (LS) mean ratios for both AUC0-tlast and Cmax were in the range of 80%-125%. The 4 × 30-mg and 1 × 120-mg tablet doses were bioequivalent (AUC0-tlast : LS mean ratio, 104.7%; 90%CI, 99.1%-110.7%; Cmax : LS mean ratio, 101.7%; 90%CI, 89.4%-115.6%; n = 24). Exposure when giving the 4 × 30-mg dose as a slurry or as tablets was comparable, with an AUC0-tlast ratio of 93.2% (84.2%-103.1%; n = 12) and a slightly decreased Cmax ratio for the slurry of 76.5% (68.8%-85.1%). Food improved the bioavailability of nifurtimox substantially (AUC0-tlast ratiofed/fasted , 172%; 90%CI, 154%-192%; Cmax ratiofed/fasted , 168%; 90%CI, 150%-187%). The data indicate that the 30- and 120-mg tablets are suitable for dosing adult and pediatric patients accurately; nifurtimox should be administered under fed conditions.

Investigation of bioequivalence, safety, and tolerability of a fixed-dose combination of nifedipine GITS and candesartan compared with the corresponding loose-dose combination under fed conditions
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OBJECTIVE: To investigate the bioequivalence, safety, and tolerability of single-dose nifedipine gastrointestinal therapeutic system (GITS) and candesartan as a fixed-dose combination (FDC) relative to the loose combination in healthy males under fed conditions. MATERIALS AND METHODS: A total of 48 subjects received nifedipine GITS 60 mg and candesartan 32 mg as an FDC or loose combination in an open-label, 2-way crossover, 2-treatment sequence design, with a washout of at least 5 days between treatments. Study medications were administered following an overnight fast of at least 10 hours, and 30 minutes after ingestion of a high-fat test meal. Plasma samples were collected at intervals over a 48-hour period post-dosing. Safety and tolerability parameters were documented throughout the study. RESULTS: For nifedipine, 90% confidence intervals (CIs) for the ratios of FDC/loose combination were within acceptance limits of bioequivalence (i.e., 80 - 125%) for both AUC0-tlast (91.36%; 111.5%) and Cmax (87.93%; 100.5%). For candesartan, 90% CIs for the ratios of FDC/loose combination were within acceptance limits for AUC0-tlast (112.8%; 124.4%), but not for Cmax (120.5%; 137.8%). There were no serious adverse events (AEs) or AEs leading to treatment discontinuation and no clinically relevant changes in vital signs or laboratory parameters. CONCLUSION: A single dose of the FDC-containing nifedipine GITS 60 mg and candesartan 32 mg, when compared to the corresponding loose combination under fed conditions, met the criterion for bioequivalence based on AUC0-tlast, while the slightly higher Cmax for candesartan is not considered clinically relevant. The FDC displayed safety and tolerability profiles similar to the loose combination.

Ciprofloxacin Dry Powder for Inhalation: Inspiratory Flow in Patients with Non-cystic Fibrosis Bronchiectasis.

Background: As non-cystic fibrosis bronchiectasis (NCFB) progresses, patients suffer irreversible lung damage and deterioration in lung function. This study explored whether inhalational parameters (peak inspiratory flow [PIF, primary endpoint], inspiratory volume and time [secondary endpoints]) represent barriers to complete dosing in patients with poor lung function who are using Ciprofloxacin dry powder for inhalation (DPI) (a drug-device combination of the T-326 inhaler device and a Ciprofloxacin dry powder formulation). Methods: This open-label, multicenter study generated inspiratory flow rate data from patients with NCFB using the breath-actuated T-326 dry powder inhaler. These rates were compared against reference values to identify whether patients with all degrees of lung function impairment could generate sufficient flow rates to facilitate adequate drug delivery. Patients attended screening and a second visit 1 - 14 days later. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), FEV1/FVC, and inspiratory capacity were measured via spirometry at both visits. Forty-two patients were screened for inclusion; 33 met eligibility criteria and were stratified into one of three groups based on their FEV1% predicted value (group 1: 25% ≤ FEV1% predicted <45%; group 2: 45% ≤ FEV1% predicted <70%; group 3: FEV1% predicted ≥70%). Results: No significant between-group differences occurred in PIF (mean flow rates 68.21, 66.01, and 65.18 L/min in groups 1, 2, and 3, respectively). Individual minimum PIFs of 46.0-49.0 L/min were observed across groups. These results all exceeded the reference value (minimum PIF 45 L/min for Ciprofloxacin DPI) indicating that regardless of the level of airflow obstruction, patients were capable of achieving sufficient PIFs to aerosolize and inhale Ciprofloxacin dry powder with the T-326 inhaler. Conclusions: Our data indicate that T-326 is suitable for use in the drug-device combination Ciprofloxacin DPI to provide targeted pulmonary delivery in patients with NCFB, including those with significantly impaired lung function.

Ciprofloxacin Dry Powder for Inhalation in Patients with Non-Cystic Fibrosis Bronchiectasis or Chronic Obstructive Pulmonary Disease, and in Healthy Volunteers.

BACKGROUND: Ciprofloxacin dry powder for inhalation (Ciprofloxacin DPI) is in development as long-term intermittent therapy to reduce the frequency of acute exacerbations in non-cystic fibrosis bronchiectasis (NCFB) patients with respiratory bacterial pathogens. There is no approved therapy in this indication. Reliable, reproducible lung deposition is a prerequisite for inhaled drugs. METHODS: In this phase I study, six patients with NCFB, six with chronic obstructive pulmonary disease (COPD), and 12 healthy volunteers (HVs), received one dose of 99mTc-Ciprofloxacin DPI 32.5 mg to assess pulmonary drug deposition by quantitative scintigraphy. 81mKrypton ventilation scans were performed to map lung contours. Systemic exposure as mediated by absorption in the lung was measured using the charcoal block method. HVs ingested activated charcoal orally (20 g before and 2 × 10 g after inhalation) to block gastrointestinal absorption of drug swallowed during inhalation. Indirect determination of pulmonary drug deposition was based on plasma and urine pharmacokinetic (PK) data. RESULTS: Scintigraphic data revealed high, reproducible lung deposition in all participants (intrapulmonary deposition relative to nominal dose, mean [standard deviation; range]: NCFB, 53% [11%; 38%-64%]; COPD, 51% [10%; 34%-61%]; HVs, 51% [7%; 40%-64%] to 53% [8%; 44%-70%]). Similar ratios of central-to-peripheral airway deposition were seen across groups. Systemic exposure to ciprofloxacin was low. Relative bioavailability of Ciprofloxacin DPI was reduced by ∼60% after charcoal block, suggesting that systemic exposure was mainly caused by uptake via the lung. Lung deposition of 30% was estimated from PK data, but this may be an underestimation due to drug clearance from the lung and transintestinal secretion. Adverse events were no more frequent or severe in patients with lung diseases versus HVs, and no clinically relevant influence on vital signs or lung function was observed. CONCLUSION: This study supports the continued development of Ciprofloxacin DPI in NCFB patients with respiratory bacterial pathogens.

Tolerability and pharmacokinetic properties of ciprofloxacin dry powder for inhalation in patients with cystic fibrosis: a phase I, randomized, dose-escalation study.

BACKGROUND: Inhaled antibacterial agents are used to manage chronic pulmonary infections in cystic fibrosis (CF) and non-CF bronchiectasis. However, established nebulized preparations impose a substantial time burden on patients. A dry powder formulation of ciprofloxacin for inhalation (ciprofloxacin DPI) has been developed using PulmoSphere™ (Novartis, Pharma AG, Basel, Switzerland) technology (administered using a T-326 inhaler) to maximize antibacterial activity and convenience. OBJECTIVE: This study investigated the tolerability and pharmacokinetic properties of multiple-dose once-daily and twice-daily ciprofloxacin DPI in adults with CF. METHODS: A Phase I, randomized, single-blind, placebo-controlled, dose-escalation study in patients with CF (median age 29.0 years [19-40]), stable pulmonary status, and chronic Pseudomonas aeruginosa colonization. Sequential cohorts received ciprofloxacin DPI 32.5 mg qd (1 capsule for inhalation; n = 6), 65 mg qd (2 capsules for inhalation; n = 6), or 32.5 mg (n = 6) bid for 7 days. Each group was placebo controlled. RESULTS: Twenty-five patients were enrolled (12 men; median age, 29.0 years [range, 19-40 years]; 6, 6, 6, and 7 patients in the ciprofloxacin DPI 32.5 mg qd, 65 mg qd, and 32.5 mg bid and placebo groups, respectively). No serious treatment-emergent adverse events or clinically relevant changes in tolerability parameters, including lung function measurements, were reported. Twenty-one patients (ciprofloxacin, n = 17; placebo, n = 4) experienced 29 mild drug-related treatment-emergent adverse events, including bitter taste (ciprofloxacin, 17 patients; placebo, 2) and bronchospasm (ciprofloxacin, 3; placebo, 2). Ciprofloxacin DPI was absorbed rapidly after inhalation. Systemic exposure to ciprofloxacin was low and comparable between single and multiple dosing in all 3 dose groups, suggesting an absence of substantial drug accumulation. The geometric mean AUCs after the last dose were 0.383, 1.472, and 0.781 mg · h/L with ciprofloxacin DPI 32.5 mg qd, 65 mg qd, and 32.5 mg bid, respectively. The range of geometric mean t(½) in plasma was 3.4 to 9.5 hours. Sputum concentrations of ciprofloxacin were high, with substantial variability. Geometric mean ciprofloxacin concentrations (%CV) in induced sputum were 57.7 (118.2), 177.5 (53.4), and 149.7 (249.7) mg/L 0.75 hours after the last dose of ciprofloxacin DPI 32.5 mg qd, 65 mg qd, and 32.5 mg bid, respectively. CONCLUSIONS: Ciprofloxacin DPI was well tolerated, especially with respect to lung function, with minimal systemic exposure compared with data from previous studies of oral and intravenous administration, and with no apparent accumulation at steady state. Sputum ciprofloxacin concentrations above 100-times the minimum inhibitory concentration for P aeruginosa were detected. Ciprofloxacin DPI may be effectively delivered to the lungs at microbiologically active concentrations while minimizing the risk for systemic intolerabilities. Eudra clinical trial identifier: 2006-003690-26.

Investigation of bioequivalence of a new fixed-dose combination of nifedipine and candesartan with the corresponding loose combination as well as the drug-drug interaction potential between both drugs under fasting conditions.

OBJECTIVE: To determine the bioequivalence of a nifedipine and candesartan fixed-dose combination (FDC) with the corresponding loose combination, and to investigate the pharmacokinetic drug-drug interaction potential between both drugs. METHODS: 49 healthy, white, male subjects received: 60 mg nifedipine and 32 mg candesartan FDC, the loose combination of 60 mg nifedipine GITS and 32 mg candesartan, 60 mg nifedipine GITS alone, or 32 mg candesartan alone in a randomized, non-blinded, 4-period, 4-way crossover design with each dosing following overnight fasting. Treatment periods were separated by washout periods of ≥ 5 days. Plasma samples were collected for 48 hours after dosing and assayed using a validated LC-MS/MS method. RESULTS: Bioequivalence between the FDC and the loose combination as well as the impact of combined treatment with both drugs on candesartan pharmacokinetics was evaluated in 47 subjects, while the corresponding impact of treatment with both drugs on nifedipine pharmacokinetics was assessed in 46 patients. For AUC(0-tlast) and Cmax the 90% confidence intervals (CIs) for the ratios of the FDC vs. the corresponding loose combination were within the acceptance range for bioequivalence of 80 - 125%. When comparing AUC(0-tlast) and Cmax of nifedipine and candesartan after dosing with the loose combination vs. each drug alone, the 90% CIs remained within the range of 80 - 125% indicating the absence of a clinically relevant pharmacokinetic drug-drug interaction. Nifedipine and candesartan as well as the combinations were well tolerated. CONCLUSIONS: The FDC containing 60 mg nifedipine and 32 mg candesartan was bioequivalent to the corresponding loose combination following single oral doses under fasting conditions. No clinically relevant pharmacokinetic drug-drug interaction between nifedipine and candesartan was observed.

Pharmacokinetics of a new orodispersible tablet formulation of vardenafil: results of three clinical trials.

BACKGROUND: Vardenafil is a potent and highly selective oral phosphodiesterase type 5 (PDE-5) inhibitor that has been shown in numerous clinical trials and post-marketing surveillance studies to be safe and effective for improving erectile function in men with erectile dysfunction (ED). Until recently, the drug was only available as a film-coated tablet (FCT). A new orodispersible tablet (ODT) formulation of vardenafil has been developed that disintegrates in the subject's mouth without the need for water or other liquids. OBJECTIVE: To characterize the pharmacokinetics of a new 10 mg ODT formulation of vardenafil. METHODS: Three clinical trials were conducted: (i) a randomized 4-fold crossover study to assess the effect of food and water on the pharmacokinetics of vardenafil ODT, compared with vardenafil FCT, in healthy men; (ii) a phase I study to assess single and multiple doses of vardenafil ODT, compared with a single dose of vardenafil FCT, in young and elderly men with ED; and (iii) a pharmacokinetic substudy of a phase III trial in men of broad age range with ED. RESULTS: Vardenafil ODT was rapidly absorbed after oral administration without water, with a similar pharmacokinetic profile to vardenafil FCT, except that the ODT exhibited significantly greater bioavailability. After a single dose, the geometric mean area under the plasma concentration-time curve from time zero to infinity (AUC(∞)) of vardenafil ODT increased by 21-44% compared with the FCT. There was no consistent difference in geometric mean maximum vardenafil plasma concentration (C(max)) between the two formulations. Geometric mean AUC(∞) and C(max) were increased by 41% and 24%, respectively, in men with ED aged ≥65 years compared with those aged <65 years. Multiple dosing or administration of vardenafil ODT with food had no meaningful effect on the pharmacokinetics of vardenafil. Vardenafil ODT was well tolerated. CONCLUSION: Vardenafil ODT should be taken without water. Partial absorption of vardenafil through the oral mucosa results in an unexpected extent of suprabioavailability of the ODT formulation. Vardenafil ODT is a convenient formulation, with pharmacokinetic and safety characteristics that are appropriate for the treatment of ED.