Population pharmacokinetics of ibandronate in Caucasian and Japanese healthy males and postmenopausal females

Racial difference in bioavailability of oral ibandronate between Caucasian and Taiwanese postmenopausal women

Following 150 mg of oral ibandronate, Taiwanese females have greater serum and urine levels of this drug and bone resorption marker suppression than Caucasian women. These inter-ethnic differences seems to be partly explained by a 2.48-fold higher bioavailability of ibandronate in Taiwanese postmenopausal women.

INTRODUCTION

Interethnic differences in the pharmacokinetics of oral ibandronate for osteoporosis are unknown. We compared the disposition of oral ibandronate between Caucasian and Taiwanese postmenopausal women.

METHODS

Ibandronate 150 mg was administered to 35 Caucasian and 16 Taiwanese postmenopausal women in two separate phase 1 studies. Interethnic comparisons were performed to assess pharmacokinetic properties, including the area under the concentration-time curve (AUC), peak concentration (Cmax), elimination half-life, urinary drug recovery (Ae%), renal clearance (CLr), apparent total clearance (CL/F), and apparent volume of distribution (Vd/F).

RESULTS

The mean AUC, Cmax, and Ae% were 2.41-, 1.69-, and 2.95-fold greater in the Taiwanese than in the Caucasian subjects, and the average CL/F and Vd/F were 2.48- and 2.46-fold smaller. There were no significant differences in mean CLr and half-life between both groups. As bisphosphonates are not biotransformed but are mainly excreted in the urine, the total body clearance is close to the CLr. These results suggested a larger bioavailability in the Taiwanese group which resulted in the differences in the CL/F and Vd/F. Multiple linear regression analysis demonstrated ethnicity influences of the pharmacokinetic properties after adjusting for the other variables.

CONCLUSIONS

Bioavailability was largely responsible for the interethnic pharmacokinetic differences following oral administration of 150 mg ibandronate and seemed greater in the Taiwanese compared with the Caucasian subjects. Further dose-ranging studies are warranted to determine the optimal dosages of oral ibandronate in patients of Asian or Taiwanese ethnicity.

The optimal oral dose selection of ibandronate in Japanese patients with osteoporosis based on pharmacokinetic and pharmacodynamic properties

Ibandronate is a drug widely used outside Japan for the treatment of osteoporosis. It is available in formulations for intermittent intravenous (i.v.) administration and for intermittent (once monthly) oral administration. Ibandronate was recently approved in Japan as an i.v. injection with a dosing regimen of 1.0 mg once a month. To establish the optimal dose for oral administration of ibandronate in Japanese osteoporotic patients, we investigated the pharmacokinetics of and pharmacodynamic response to ibandronate following oral and intravenous administrations to Japanese subjects. Ibandronate (20, 50, 100, or 150 mg) was given orally to healthy postmenopausal Japanese women and to Japanese patients with primary osteoporosis. Serial measurements were obtained for the concentrations of serum ibandronate and urinary cross-linked C-telopeptide of Type I collagen (uCTX). Pharmacokinetic parameters and the time profiles of creatinine-corrected uCTX were compared with those obtained from postmenopausal Japanese women with osteopenia after administration of 1.0 mg i.v. ibandronate. Following oral administration of ibandronate, the area under the serum ibandronate concentration–time curve (AUC_inf) increased dose-proportionally for doses up to 100 mg; at 150 mg, AUC_inf increased beyond the dose-proportionality seen with doses up to 100 mg. The AUC_inf within the linear range following administration of 100 mg oral ibandronate was similar to that following 1.0 mg i.v. ibandronate. Additionally, corrected uCTX decreased after administration of 100 mg oral ibandronate and remained decreased for 1 month; the magnitude of the decrease was similar to or greater than that obtained after 1.0 mg i.v. ibandronate. From a clinical pharmacological perspective, administration of 100 mg/month oral ibandronate was equivalent to that of 1.0 mg/month i.v. ibandronate.

Application of modeling and simulation to a long-term clinical trial: a direct comparison of simulated data and data actually observed in Japanese osteoporosis patients following 3-year ibandronate treatment

Ibandronate, a nitrogen-containing bisphosphonate, is a bone resorption inhibitor widely used to prevent and treat osteoporosis. To optimize the design for a long-term clinical study of ibandronate, modeling and simulation (M&S) was performed based on the result of population pharmacodynamic analysis using the data of a short-term clinical study. A population pharmacodynamic model was constructed by the urinary C-terminal telopeptide of type I collagen (uCTx) and the lumbar spine bone mineral density (BMD) data obtained in clinical studies, including a phase II study of Japanese osteoporosis patients treated with ibandronate for 6 months. Changes in BMD over a period of 3 years were simulated from the population pharmacodynamic parameters of the patients in this phase II study. The relationship between uCTx and BMD was well described by this modeling. The functions of disease progression and supplemental treatment were incorporated into the model to simulate a long-term clinical study with high accuracy. A long-term clinical study with a 3-year treatment was conducted after this M&S. The percentage change from baseline in observed BMD values were found to be similar to the prospectively simulated values. This study showed that M&S could be a useful and powerful tool for designing and conducting long-term clinical studies when carried out in the following sequence: (1) conduct a short-term clinical study; (2) perform M&S; and (3) conduct the long-term clinical study. Application of this procedure to various other treatment agents will establish the usefulness of M&S for long-term clinical studies and bring further efficiencies to drug development.

Bone-targeted therapies for elderly patients with renal cell carcinoma: current and future directions

Bone metastases are very common in advanced renal cell carcinoma (RCC) and can have a huge impact on quality of life by leading to skeletal-related events (SREs), including pain, pathologic fractures and spinal cord compression with need for surgery or radiotherapy. Because of their osteolytic aspect and biologic behaviour, these SREs are more common in patients with bone metastases from RCC than from other malignancies. As overall survival is increased by new anti-angiogenic drugs like tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors, the incidence of SREs is rising, making the clinical management of bone metastases in RCC ever more important, especially in the more vulnerable elderly patient. In this review we discuss the current advances and future directions in bone-targeted therapies in patients with RCC with a special focus on the elderly population. Recently, two bone-targeted agents have been approved in the prevention of SREs in advanced RCC: zoledronic acid and denosumab. To date, there is no specific data on the use of bisphosphonates or denosumab in the elderly and specific studies in this setting are warranted. We compare the available evidence for the use and implications of both agents in the elderly patient and give general information on safety concerns that could be more important in these patients.

A network modeling approach for the spatial distribution and structure of bone mineral content

This study aims to develop a spatial model of bone for quantitative assessments of bone mineral density and microarchitecture. A spatially structured network model for bone microarchitecture was systematically investigated. Bone mineral-forming foci were distributed radially according to the cumulative normal distribution, and Voronoi tessellation was used to obtain edges representing bone mineral lattice. Methods to simulate X-ray images were developed. The network model recapitulated key features of real bone and contained spongy interior regions resembling trabecular bone that transitioned seamlessly to densely mineralized, compact cortical bone-like microarchitecture. Model-simulated imaging profiles were similar to patients' X-ray images. The morphometric metrics were concordant with microcomputed tomography results for real bone. Simulations comparing normal and diseased bone of 20-30 to 70-80 year-olds demonstrated the method's effectiveness for modeling osteoporosis. The novel spatial model may be useful for pharmacodynamic simulations of bone drugs and for modeling imaging data in clinical trials.

Perspectives in the elderly patient: benefits and limits of bisphosphonates and denosumab

Skeletal metastases affect a large percentage of the cancer population and contribute to a marked decrease in their quality of life and survival, in particular in elderly population. A future end-point of bone-protecting therapy is the demonstration of its ability to prevent or improve results in the treatment of metastatic disease, enlarging their clinical indications in metastatic and osteoporotic setting with different schedules. In this chapter we will discuss on pharmacokinetic and pharmacodynamic interactions of bisphosphonates in elderly, and the preclinical and clinical evidences of anticancer activity of bone-targeted therapies will be critically described. The clinical results of new targeted therapies (such as rank/rankl/OPG inhibition) will be reported both in bone metastatic and in adjuvant settings. Finally, the prevention of cancer treatment-induced bone loss (CTIBL) represents both in young and more in old patients an emerging issue in the bone health care. For this reason, this chapter will discuss the results of current therapies in this clinical setting.

Pharmacokinetic evaluation of the penetration of antituberculosis agents in rabbit pulmonary lesions

Standard antituberculosis (anti-TB) therapy requires the use of multiple drugs for a minimum of 6 months, with variable outcomes that are influenced by a number of microbiological, pathological, and clinical factors. This is despite the availability of antibiotics that have good activity against Mycobacterium tuberculosis in vitro and favorable pharmacokinetic profiles in plasma. However, little is known about the distribution of widely used antituberculous agents in the pulmonary lesions where the pathogen resides. The rabbit model of TB infection was used to explore the hypothesis that standard drugs have various abilities to penetrate lung tissue and lesions and that adequate drug levels are not consistently reached at the site of infection. Using noncompartmental and population pharmacokinetic approaches, we modeled the rate and extent of distribution of isoniazid, rifampin, pyrazinamide, and moxifloxacin in rabbit lung and lesions. Moxifloxacin reproducibly showed favorable partitioning into lung and granulomas, while the exposure of isoniazid, rifampin, and pyrazinamide in lesions was markedly lower than in plasma. The extent of penetration in lung and lesions followed different trends for each drug. All four agents distributed rapidly from plasma to tissue with equilibration half-lives of less than 1 min to an hour. The models adequately described the plasma concentrations and reasonably captured actual lesion concentrations. Though further refinement is needed to accurately predict the behavior of these drugs in human subjects, our results enable the integration of lesion-specific pharmacokinetic-pharmacodynamic (PK-PD) indices in clinical trial simulations and in in vitro PK-PD studies with M. tuberculosis.

Pharmacology of bisphosphonates

Four decades of preclinical and clinical research of the pharmacology of bisphosphonates have generated data and concepts that have considerably improved their clinical use. However, despite this progress several pharmacological aspects relevant to bisphosphonate action on bone are still incompletely understood. This is mainly due to the complex, unique pharmacological properties of bisphosphonates. We review here the pharmacokinetic and pharmacodynamic data of bisphosphonates that are relevant for their clinical application and for the potential choice of a given compound, focusing on uncertainties that still exist.

Review of osteoporosis pharmacotherapy for geriatric patients

BACKGROUND

Fractures are a significant problem in geriatric patients, and understanding the evidence for benefit and possible harm of osteoporosis treatments is critical to appropriate management of this patient population.

OBJECTIVE

The purpose of this article was to review the evidence and treatment considerations related to use of the approved osteoporosis treatments in the United States across the continuum of ages in the geriatric population.

METHODS

MEDLINE and the Web of Science were searched to find English-language articles published from 2000 through July 2009. Search terms included: practice guideline, osteoporosis, calcium, vitamin D, pharmacoeconomics, ethnicity, and treatment. The generic names of each of the osteoporosis treatments approved in the United States were searched to find relevant clinical trials and randomized controlled trials (RCTs). Pivotal trials that included fracture data or focused specifically on elderly patients (> or = 60 years of age) were selected. Bibliographies in the identified articles were searched for additional articles, and the prescribing information for each of the approved treatments was reviewed.

RESULTS

Many osteoporosis studies have a mean patient age >60 years, but data for older patients are limited. Subanalyses of older patient groups have found risedronate to be beneficial for vertebral fractures in patients aged 70 to 79 years (absolute risk reduction [ARR], 8.4%; P < 0.001) and teriparatide to be beneficial for both vertebral (ARR, 6.4%; P < 0.05) and new nonvertebral fragility fractures (ARR, 9.9%; P < 0.05) in women aged > or = 75 years. However, no RCTs of geriatric patients who were either nonambulatory or had multiple comorbidities were identified in the literature.

CONCLUSIONS

Evidence indicates that the osteoporosis treatments currently available in the United States are beneficial for treating osteoporosis in geriatric patients. However, data are limited for the oldest patients (> or = 80 years) and those with significant comorbidities. Because of the limited availability of data for geriatric patients with significant comorbidities, the properties of the various agents, including efficacy, tolerability, and potential contraindications, should be considered carefully for each geriatric patient.

New and emerging treatments for osteoporosis

A variety of new treatments for osteoporosis have become available within the last several years, and a number of emerging treatments remain in late clinical stage development. New and emerging treatments include more potent members, or more convenient formulations, of existing classes of therapy, but a number of the emerging treatments are first-generation compounds addressing specific therapeutic targets based on recent advances in understanding of basic bone biology. These new and emerging treatments include agents with anticatabolic effects, compounds with anabolic effects, and one agent possibly containing both anticatabolic and anabolic effects. The increasing variety of new and emerging treatments increases the possibility that effective therapy will be targeted to the specific needs of the individual patient.