Andrew Denker

Odanacatib in the treatment of postmenopausal women with low bone mineral density: five years of continued therapy in a phase 2 study.

Odanacatib (ODN) is a selective inhibitor of the collagenase cathepsin K that is highly expressed by osteoclasts. In this 2‐year, phase 2, dose‐ranging trial, postmenopausal women with bone mineral density (BMD) T‐scores −2.0 to −3.5 at spine or hip were randomized to weekly placebo or ODN 3, 10, 25, or 50 mg plus vitamin D3 and calcium. Prespecified trial‐extensions continued through 5 years. In year 3, all women were re‐randomized to ODN 50 mg or placebo. For years 4 and 5, women who received placebo or ODN 3 mg in years 1 and 2 and placebo in year 3 received ODN 50 mg; others continued year 3 treatments. Endpoints included lumbar spine (primary), hip, 1/3 radius, and total body BMD; markers of bone metabolism; and safety. Women in the year 4 to 5 extension receiving placebo (n = 41) or ODN 50 mg (n = 100) had similar baseline characteristics. For women who received ODN (10–50 mg) for 5 years, spine and hip BMD increased over time. With ODN 50 mg continually for 5 years (n = 13), mean lumbar spine BMD percent change from baseline (95% confidence interval [CI]) was 11.9% (7.2% to 16.5%) versus −0.4% (−3.1% to 2.3%) for women who were switched from ODN 50 mg to placebo after 2 years (n = 14). In pooled results of women receiving continuous ODN (10–50 mg, n = 26–29), year 5 geometric mean percent changes from baseline in bone resorption markers cross‐linked N‐telopeptide of type I collagen (NTX)/creatinine and cross‐linked C‐telopeptide (CTX) were approximately −55%, but near baseline for bone formation markers bone‐specific alkaline phosphatase (BSAP) and amino‐terminal propeptide of type I procollagen (P1NP). In women switched from ODN 10 to 50 mg to placebo after 2 years (n = 25), bone turnover markers were near baseline. In summary, women receiving combinations of ODN (10–50 mg) for 5 years had gains in spine and hip BMD and showed larger reductions in bone resorption than bone formation markers. Discontinuation of ODN resulted in reversal of treatment effects. Treatment with ODN for up to 5 years was generally well‐tolerated.

Pharmacokinetic considerations in determining the terminal elimination half-lives of bisphosphonates.

AbstractBackground and objective: Bisphosphonates are commonly used to treat and prevent osteoporosis. These compounds have unusual pharmacokinetic characteristics because they bind strongly to bone, and a portion becomes buried under newly formed bone. Once incorporated into bone tissue, the subsequent release during bone remodeling is probably the rate-limiting step in the terminal elimination of bisphosphonates. Because of this unique property of bisphosphonates, pharmacokinetic studies with insufficient lengths of follow-up might entirely miss the true terminal elimination phase. A terminal half-life (t1/2γ) of approximately 11 years, similar to that of calcium and other minerals in bone, was reported from an 18-month study of alendronic acid in postmenopausal women with osteoporosis. We are not aware of any other published reports in which the elimination of a bisphosphonate has been followed for more than a few weeks post-dose. The purpose of the present study was to reanalyse the alendronic acid data to examine the effect of truncating the length of follow-up on the calculated t1/2γ. Patients and methods: Twenty-one postmenopausal women with osteoporosis (mean age 66 years) received intravenous alendronic acid 30mg over 4 consecutive days (7.5 mg/day), and urinary excretion of alendronic acid was monitored over the following 18–24 months. Terminal elimination half-life was originally calculated by log-linear regression of the percentage retained versus time curve between days 240 and 540 and substituting the slope of the regression line into the equation, t1/2γ = −log 2/slope. These data were reanalysed based on the period up to 30 days. Results: Data were sufficient for analysis of pharmacokinetics in 11 patients. A mean t1/2γ of approximately 11 years was reported previously, based on analysis of data between days 240 and 540. Recalculating the ‘terminal’ half-life of alendronic acid using only data from the first 30 days resulted in an ‘observed’ half-life of only 11 days. Conclusion: This analysis illustrates the importance of sufficient length of follow-up to accurately characterise the true terminal elimination half-life of bisphosphonates. The relatively short (expressed in units of days rather than years) terminal elimination half-lives reported for some bisphosphonates based on only 30 days of follow-up or less are likely to substantially underestimate the true terminal elimination half-lives.

A Phase 2, Randomized, Placebo-Controlled, Dose-Ranging Study of the Calcium-Sensing Receptor Antagonist MK-5442 in the Treatment of Postmenopausal Women With Osteoporosis

CONTEXT MK-5442 is an orally bioavailable calcium-sensing receptor antagonist that is hypothesized to stimulate bone formation by stimulating endogenous secretion of a pulse of PTH. Earlier clinical and preclinical studies demonstrated increased bone mineral density (BMD) after treatment. OBJECTIVE Our objective was to identify a dose of MK-5442 that produces osteoanabolic effects without excessive hypercalcemia. DESIGN AND SETTING This was a randomized, double-blind, placebo-controlled, parallel-group trial of private or institutional practice. PARTICIPANTS AND INTERVENTION In total, 383 postmenopausal women with osteoporosis were administered daily oral MK-5442 (2.5, 5, 7.5, 10, or 15 mg) or placebo. MAIN OUTCOME MEASURES Serum PTH and calcium, bone turnover markers, areal BMD, and safety were evaluated. RESULTS A dose-dependent transient increase in PTH occurred after an MK-5442 dose and lasted more than 3.5 hours. Compared with placebo, significant increases in bone formation markers (serum procollagen 1 N-terminal peptide and bone-specific alkaline phosphatase) were observed by 6 months, whereas bone resorption markers (serum C-telopeptide of type 1 collagen, urine N-telopeptides of type 1 collagen) initially decreased but were also significantly increased by 6 months. Despite the biochemical marker changes suggestive of an anabolic response, there were no statistically significant differences between any dose of MK-5442 and placebo in percent change from baseline at month 6 in any of the BMD endpoints. The frequency of hypercalcemia (trough serum calcium ≥ 10.8 mg/dL) was greater with higher MK-5442 doses. CONCLUSION In postmenopausal women with low bone mass, treatment with MK-5442 resulted in transient pulses of PTH. Bone formation markers increased quickly and bone resorption markers decreased temporarily, suggestive of an anabolic window. However, there were no increases in BMD versus placebo.

A semimechanistic model of the time‐course of release of PTH into plasma following administration of the calcilytic JTT‐305/MK‐5442 in humans

JTT‐305/MK‐5442 is a calcium‐sensing receptor (CaSR) allosteric antagonist being investigated for the treatment of osteoporosis. JTT‐305/MK‐5442 binds to CaSRs, thus preventing receptor activation by Ca2+. In the parathyroid gland, this results in the release of parathyroid hormone (PTH). Sharp spikes in PTH secretion followed by rapid returns to baseline are associated with bone formation, whereas sustained elevation in PTH is associated with bone resorption. We have developed a semimechanistic, nonpopulation model of the time‐course relationship between JTT‐305/MK‐5442 and whole plasma PTH concentrations to describe both the secretion of PTH and the kinetics of its return to baseline levels. We obtained mean concentration data for JTT‐305/MK‐5442 and whole PTH from a multiple dose study in U.S. postmenopausal women at doses of 5, 10, 15, and 20 mg. We hypothesized that PTH is released from two separate sources: a reservoir that is released rapidly (within minutes) in response to reduction in Ca2+ binding, and a second source released more slowly following hours of reduced Ca2+ binding. We modeled the release rates of these reservoirs as maximum pharmacologic effect (Emax) functions of JTT‐305/MK‐5442 concentration. Our model describes both the dose‐dependence of PTH time of occurrence for maximum drug concentration (Tmax) and maximum concentration of drug (Cmax), and the extent and duration of the observed nonmonotonic return of PTH to baseline levels following JTT‐305/MK‐5442 administration.

Bioavailability of Alendronate and Vitamin D3 in an Alendronate/Vitamin D3 Combination Tablet

These studies were designed to demonstrate that the alendronate (ALN) component of an ALN/vitamin D3 combination tablet was bioequivalent to the 70‐mg ALN tablet and that the pharmacokinetic parameters of vitamin D3 were similar with or without ALN. These were open‐label, randomized, 2‐part, 2‐period, crossover studies. In part I, participants received either a single combination tablet or ALN 70 mg. In part II, participants received either a single combination tablet or vitamin D3 alone. Results from part I showed that the geometric mean ratio (GMR) for total urinary excretion of ALN for both studies fell within the prespecified bioequivalence bounds. Results from part II showed that the pharmacokinetic profiles of vitamin D3 with or without ALN were also similar. The combination tablets are bioequivalent to the ALN 70‐mg tablet with respect to ALN bioavailability. The bioavailability of vitamin D3 is similar in the combination tablets and when administered alone. No serious adverse experiences were reported.

Bioavailability and Short-Term Tolerability of Alendronate in Glucocorticoid-Treated Children

BACKGROUND Children receiving glucocorticoids (GCs) are at an increased risk of fragility fractures. Conservative measures may be inadequate in treating low bone mass, giving rise to fractures in this population; as such, attention has turned to the use of bisphosphonates. OBJECTIVE The goal of this study was to evaluate the bioavailability and single-dose tolerability of alendronate (ALN) in children receiving a stable dose of GCs. METHODS Children (ages 4-17 years) receiving GC treatment for their chronic illnesses received intravenous (125 μg) and oral (35 mg) ALN in a 2-period, randomized crossover study, with doses separated by at least a 7-day washout period. Urine was collected for either 8 or 24 hours after drug administration to determine urinary excretion of ALN and bioavailability. Tolerability was assessed by continuous collection of adverse events reported during the study. The main outcome measures were total urinary excretion rates, oral bioavailability of ALN, and adverse events. RESULTS There were 12 patients in the 4- to 11-year-old group (mean age, 8.1 years; 5 girls) and 12 patients in the 12- to 17-year-old group (mean age, 14.3 years; 5 girls). The least-squares mean bioavailability (90% CI) for children aged 4 to 11 years (n = 12) was 0.43% (0.27-0.67) and for children aged 12 to 17 years (n = 12) it was 0.39% (0.26-0.60). The least-squares mean bioavailability for all ages combined was 0.41% (0.30-0.56), with no statistical difference between the 2 age groups. The total urinary excretion of ALN after the intravenous dose was similar between groups. Fifteen patients reported a total of 36 transient clinical nonserious adverse events, all of which were mild or moderate in intensity; the most common were headache (n = 13), abdominal pain (n = 3), limb, neck, or facial pain (n = 6), and ankle or knee swelling (n = 3). CONCLUSIONS The mean oral bioavailability of ALN was similar to previous pharmacokinetic studies in children with osteogenesis imperfecta and slightly lower than that observed in historical adult controls. Alendronate was generally well tolerated, with minor adverse events that resolved uneventfully. Elucidation of the full adverse-effect profile of this agent was limited by the single-dose nature of this study, and robust comparisons of the pharmacokinetics of ALN in different age groups may need a larger number of patients.

Pharmacokinetics of digoxin in healthy subjects receiving taranabant, a novel cannabinoid-1 receptor inverse agonist

IntroductionInteraction studies with digoxin (Lanoxin®; GlaxoSmithKline, Research Triangle Park, NC, USA), a commonly prescribed cardiac glycoside with a narrow therapeutic index and a long half-life, are typically required during the development of a new drug, particularly when it is likely that digoxin may be given to patients also treated with the new agent, taranabant—a cannabinoid-1 receptor inverse agonist—for weight loss. This study was designed to establish if this combination of therapy has the potential of a significant pharmacokinetic interaction.MethodsThis open-label, fixed-sequence, two-period study investigated whether taranabant, administered to steady state, affects the well-described single-dose pharmacokinetics of digoxin. During the first period, 12 healthy men and women ranging in age from 21 to 35 years received a single oral dose of digoxin 0.5 mg. Following a 10-day wash out, they started a 19-day taranabant dosing regimen (6 mg once daily from day −14 to day 5) designed to establish and maintain steady-state levels of taranabant. On study day 1, subjects received a single oral dose of digoxin 0.5 mg. The plasma levels of digoxin were followed for an additional 4 days while the dosing of taranabant continued.ResultsThe geometric mean ratio and 90% confidence intervals for digoxin AUC0-∞ were 0.91 (0.83, 0.99), falling within the prespecified comparability intervals (CI) of (0.8, 1.25), which is within the usually allowed interval for bioequivalence. The geometric mean ratio and 90% CI for digoxin maximum plasma concentration (Cmax) were 1.23 (1.09, 1.40). The median time to Cmax was the same for both treatments.ConclusionMultiple doses of 6 mg taranabant do not have a clinically meaningful effect on the pharmacokinetics of a single oral dose of digoxin.

Diary of hot flashes reported upon occurrence: results of a randomized double-blind study of raloxifene, placebo, and paroxetine.

ObjectiveThis trial examined diaries of hot flash events reported upon occurrence to assess the test/retest reliability of the diaries and their ability to measure treatment effects on hot flash frequency and severity. MethodsForty-two postmenopausal women (aged ≥40 y; 5-50 hot flashes/wk) were randomized (3:3:1) to placebo, raloxifene 60 mg, or paroxetine 20 mg daily for 12 weeks. Diaries of hot flash frequency and severity were evaluated at 1-week intervals (twice before study treatment and thrice during study treatment). ResultsForty-one women were evaluated. Baseline characteristics were similar between groups (eg, mean, 29.8 hot flashes/wk). Concordance correlation coefficients between screening (week −2) and baseline (week −1) measures of hot flash frequency and severity were 0.73 and 0.71, respectively. After 12 weeks, the mean (95% CI) percent changes from baseline in weekly hot flash frequency were as follows: placebo, −37.4% (−60.9 to −14.0); raloxifene, −14.2% (−37.7 to 9.3); paroxetine, −49.8% (−88.6 to −11.0); the mean (95% CI) percent changes in hot flash severity were as follows: placebo, −39.9% (−69.1 to −10.8); raloxifene, −9.6% (−38.8 to 19.6); paroxetine, −36.6% (−84.7 to 11.5). There were no significant differences in hot flash diary results between treatment groups. ConclusionsMeasures of hot flash frequency and severity show acceptable test/retest reliability between screening and baseline. Reductions in vasomotor symptoms by raloxifene are numerically less than those seen with placebo, but no statistically significant treatment differences have been documented in this small study. The large effect of placebo and the significant reduction in vasomotor symptoms by paroxetine are consistent with other studies. The diary seems to be suitable for use in hot flash clinical trials.

Pharmacokinetics and Pharmacodynamics of Anacetrapib Following Single Doses in Healthy, Young Japanese and White Male Subjects

Anacetrapib is a cholesteryl ester transfer protein (CETP) inhibitor being developed for the treatment of mixed dyslipidemia. The aim of the study was to evaluate the pharmacokinetic, pharmacodynamic, and safety characteristics of anacetrapib following single doses in healthy, young Japanese men. In a double‐blind, randomized, placebo‐controlled, 3‐panel, single‐rising‐dose study, 6 healthy young Japanese male or white male subjects (aged 19 to 44 years) received single oral doses of 5 to 500 mg anacetrapib, and 2 received placebo. Plasma and urine drug concentrations were measured 0–168 hours postdose, and plasma CETP inhibition was measured 0–24 hours postdose. Urinary anacetrapib levels were all below quantitation limits. Plasma concentrations of anacetrapib increased approximately less than dose‐proportionally. Consumption of a traditional Japanese breakfast prior to dosing increased the plasma pharmacokinetics of anacetrapib in Japanese subjects compared with fasted conditions, to a similar extent as in white subjects. CETP activity measured over 0–24 hours postdose resulted in significant inhibition. Anacetrapib was generally well tolerated, and there were no serious adverse experiences. No clinically meaningful differences in PK and CETP inhibition parameters were found between Japanese and white subjects.

Effects of Laropiprant, a Selective Prostaglandin D2 Receptor 1 Antagonist, on the Steady‐State Pharmacokinetics of Digoxin in Healthy Adult Subjects

Laropiprant, a prostaglandin D2 receptor‐1 antagonist shown to reduce flushing symptoms, has been combined with niacin for treatment of dyslipidemia. This open‐label, randomized, 2‐period crossover study assessed the effects of laropiprant on the pharmacokinetics of digoxin, with 13 healthy subjects randomized to 2 treatments administered in random order with a 10‐day or longer washout period: (A) single‐dose digoxin 0.5 mg on day 1 and once‐daily oral doses of laropiprant 40 mg for 10 days beginning 5 days prior to digoxin dosing (day −5 to day 5); (B) single‐dose digoxin 0.5 mg on day 1. Blood was collected over the course of 120 hours post digoxin dose to assess pharmacokinetics of immunoreactive digoxin. Comparability was declared if the 90% confidence interval for the geometric mean ratio of laropiprant+digoxin to digoxin alone of the area under the plasma concentration—time curve from time 0 to infinity (AUC0‐∞) for immunoreactive digoxin fell within 0.80 to 1.25. The AUC0‐∞ and maximum observed plasma concentration (Cmax) geometric mean ratios of immunoreactive digoxin were 0.91 (90% confidence interval, 0.76–1.10) and 1.04 (90% confidence interval, 0.91–1.21), respectively. Median time of occurrence of Cmax and mean half‐life of immunoreactive digoxin were comparable in the presence and absence of laropiprant. Coadministration of digoxin and laropiprant was generally well tolerated. The small decrease in exposure to immunoreactive digoxin (∼10%) following coadministration of laropiprant and digoxin is not considered to be clinically meaningful.