RM-493, a melanocortin-4 receptor (MC4R) agonist, increases resting energy expenditure in obese individuals.

CONTEXT: Activation of the melanocortin-4 receptor (MC4R) with the synthetic agonist RM-493 decreases body weight and increases energy expenditure (EE) in nonhuman primates. The effects of MC4R agonists on EE in humans have not been examined to date. OBJECTIVE, DESIGN, AND SETTING: In a randomized, double-blind, placebo-controlled, crossover study, we examined the effects of the MC4R agonist RM-493 on resting energy expenditure (REE) in obese subjects in an inpatient setting. STUDY PARTICIPANTS AND METHODS: Twelve healthy adults (6 men and 6 women) with body mass index of 35.7 ± 2.9 kg/m(2) (mean ± SD) received RM-493 (1 mg/24 h) or placebo by continuous subcutaneous infusion over 72 hours, followed immediately by crossover to the alternate treatment. All subjects received a weight-maintenance diet (50% carbohydrate, 30% fat, and 20% protein) and performed 30 minutes of standardized exercise daily. Continuous EE was measured on the third treatment day in a room calorimeter, and REE in the fasting state was defined as the mean of 2 30-minute resting periods. RESULTS: RM-493 increased REE vs placebo by 6.4% (95% confidence interval, 0.68-13.02%), on average by 111 kcal/24 h (95% confidence interval, 15-207 kcal, P = .03). Total daily EE trended higher, whereas the thermic effect of a test meal and exercise EE did not differ significantly. The 23-hour nonexercise respiratory quotient was lower during RM-493 treatment (0.833 ± 0.021 vs 0.848 ± 0.022, P = .02). No adverse effect on heart rate or blood pressure was observed. CONCLUSIONS: Short-term administration of the MC4R agonist RM-493 increases REE and shifts substrate oxidation to fat in obese individuals.

Inhibition of prostacyclin and thromboxane biosynthesis in healthy volunteers by single and multiple doses of acetaminophen and indomethacin.

This double-blind, randomized crossover study assessed the effect of acetaminophen (1000 mg every 8 hours) versus indomethacin (50 mg every 8 hours) versus placebo on cyclooxygenase enzymes (COX-1 and COX-2). Urinary excretion of 2,3-dinor-6-keto-PGF1α, (prostacyclin metabolite, PGI-M; COX-2 inhibition) and 11-dehydro thromboxane B2 (thromboxane metabolite, Tx-M; COX-1 inhibition) were measured after 1 dose and 5 days of dosing. Peak inhibition of urinary metabolite excretion across 8 hours following dosing was the primary end point. Mean PGI-M excretion was 33.7%, 55.9%, and 64.6% on day 1 and 49.4%, 65.1%, and 80.3% on day 5 (placebo, acetaminophen, and indomethacin, respectively). Acetaminophen and indomethacin inhibited PGI-M excretion following single and multiple doses (P = .004 vs placebo). PGI-M excretion inhibition after 1 dose was similar for indomethacin and acetaminophen, but significantly greater with indomethacin after multiple doses (P = .006). Mean Tx-M excretion was 16.2%, 45.2%, and 86.6% on day 1 and 46.2%, 58.4%, and 92.6% on day 5 (placebo, acetaminophen, and indomethacin, respectively). Tx-M excretion inhibition following 1 dose was reduced by acetaminophen (P ≤ .003). Indomethacin reduced Tx-M excretion significantly more than acetaminophen and placebo after single and multiple doses (P ≤ .001). Acetaminophen and indomethacin inhibited COX-1 and COX-2 following a single dose, but acetaminophen was a less potent COX-1 inhibitor than indomethacin.

Pharmacokinetic-pharmacodynamic studies of the 11ß-hydroxysteroid dehydrogenase type 1 inhibitor MK-0916 in healthy subjects.

AIMS: To characterize pharmacokinetic parameters of MK-0916 and its safety and tolerability in lean, healthy male subjects following single and multiple oral doses. To assess (by stable-isotope labelling) the in vivo inhibition of cortisone-to-cortisol conversion following oral MK-0916. METHODS: Data are presented from two randomized, controlled, double-blind, rising-dose phase I studies. In the first study, subjects received single oral doses of 0.4-100 mg MK-0916 (n = 16). In the second study, subjects received 0.2-225 mg MK-0916 followed by daily doses of 0.2-100 mg for 13 days beginning on day 2 or day 15 (n = 80). Plasma and urine drug concentrations were measured for pharmacokinetic analysis. For pharmacodynamic analysis, concentrations of plasma [(13)C4]cortisol were measured by high-pressure liquid chromatography and tandem mass spectrometry following a single oral dose of 5 mg [(13)C4]cortisone. RESULTS: Doses ≥3 mg were rapidly absorbed (time at which maximal concentration was achieved in plasma, 1.1-1.8 h). Exposure (measured as the area under the concentration-time curve from 0 to 168 h) increased approximately in proportion to dose. Values for the maximal plasma concentration and the plasma concentration at 24 h increased in excess of dose proportionality at doses <6 mg and roughly in proportion to dose at doses >6 mg. In subjects dosed with 6 mg MK-0916 once daily for 14 days, the mean trough plasma concentration was 240 nm and in vivo cortisone-to-cortisol conversion was inhibited by 84%. The relationship between plasma MK-0916 and hepatic 11ß-hydroxysteroid dehydrogenase type 1 inhibition was well represented by a simple Emax model with an IC50 of 70.4 nm. Exposure to MK-0916 was generally well tolerated. CONCLUSIONS: These findings indicate that 11ß-hydroxysteroid dehydrogenase type 1 is effectively inhibited in human subjects by doses of MK-0916 that are well tolerated.

Refinement of stopping rules during treatment of hepatitis C genotype 1 infection with boceprevir and peginterferon/ribavirin.

UNLABELLED: In comparison with peginterferon/ribavirin alone, boceprevir with peginterferon/ribavirin significantly improves sustained virological response (SVR) rates in patients with chronic hepatitis C virus (HCV) genotype 1 infections, but treatment failure remains a significant problem. Using phase 3 trial databases, we sought to develop stopping rules for patients destined to fail boceprevir-based combination therapy in order to minimize drug toxicity, resistance, and costs in the face of ultimate futility. Exploratory post hoc analyses using data from the Serine Protease Inhibitor Therapy 2 (SPRINT-2) study (treatment-naive patients) and the Retreatment With HCV Serine Protease Inhibitor Boceprevir and Pegintron/Rebetol 2 (RESPOND-2) study (treatment-experienced patients) were undertaken to determine whether protocol-specified stopping rules (detectable HCV RNA at week 24 for SPRINT-2 and at week 12 for RESPOND-2) could be refined and harmonized. In SPRINT-2, a week 12 rule with an HCV RNA cutoff of ≥ 100 IU/mL would have discontinued therapy in 65 of 195 failures (sensitivity = 33%) without sacrificing a single SVR among 475 successes (specificity = 100%). Viral variants emerged after week 12 in 36 of the 49 evaluable patients (73%) who would have discontinued at week 12 using a ≥ 100 IU/mL stopping rule. In RESPOND-2, five of six patients with week 12 HCV RNA levels between the lower limit of detection (9.3 IU/mL) and the lower limit of quantification (25 IU/mL) who continued therapy despite the protocol-stipulated futility rule achieved SVR; one additional patient with a week 12 HCV RNA level of 148 IU/mL also continued therapy, had undetectable HCV RNA at week 16, and attained SVR. CONCLUSION: Although a stopping rule of detectable HCV RNA at week 12 would have forfeited some SVR cases, week 12 HCV RNA levels ≥ 100 IU/mL almost universally predicted a failure to achieve SVR in both treatment-naive and treatment-experienced patients. In boceprevir recipients, the combination of 2 stopping rules-an HCV RNA level ≥ 100 IU/mL at week 12 and detectable HCV RNA at week 24--maximized the early discontinuation of futile therapy and minimized premature treatment discontinuation.

Raltegravir: the first HIV-1 integrase strand transfer inhibitor in the HIV armamentarium.

Raltegravir is the first integrase strand transfer inhibitor approved for the treatment of HIV-1 infection. As the first agent in this new class of antiretroviral therapies, raltegravir has demonstrated safety and efficacy in treatment-naive as well as heavily pretreated HIV-infected patients failing therapy with multidrug-resistant virus. Raltegravir has a favorable drug interaction profile that permits both administration to a wide, demographically diverse patient population and coadministration with many other therapeutic agents, including antiretroviral agents and supportive medications, without restrictions or dose adjustment. Data through 96 weeks of follow-up in three phase III studies, protocol 021 (STARTMRK) in treatment-naive patients, and protocols 018 (BENCHMRK-1) and 019 (BENCHMRK-2) in treatment-experienced patients, demonstrated the potent and durable antiretroviral and immunologic effects and the favorable long-term safety profile of raltegravir in both treatment-naive and treatment-experienced patients. Raltegravir represents an important addition to the current armamentarium for the treatment of HIV infection.

Evaluation of pharmacokinetic parameters and dipeptidyl peptidase-4 inhibition following single doses of sitagliptin in healthy, young Japanese males.

AIMS: Sitagliptin is a selective inhibitor of dipeptidyl peptidase-4 (DPP-4) used to treat type 2 diabetes. The present aim was to evaluate pharmacokinetic (PK), pharmacodynamic (PD) and safety characteristics of sitagliptin following single doses in healthy, young Japanese males. METHODS: In this alternating two-panel, randomized, controlled double-blind study, six healthy Japanese male subjects (aged 20-46 years) in each panel received single oral doses of 5-400mg sitagliptin and two received placebo. Plasma and urine drug concentrations were measured from 0-48h post dose and plasma DPP-4 inhibition from 0-24h post dose. The results were compared with historical data from young, healthy non-Japanese males. RESULTS: Plasma concentrations of sitagliptin increased approximately in proportion to dose; maximum concentrations occurred 2-6h post-dose. The mean apparent terminal half-life for plasma sitagliptin was 9-14h, with the half-life slightly decreasing as the dose increased. The mean dose fraction excreted unchanged in the urine was 0.73-1.00. Ingestion of a traditional Japanese breakfast prior to dosing had only a minor effect on PK parameters. After correction for dilution and competition effects during assay, doses of sitagliptin ≥50mg resulted in weighted average DPP-4 inhibition from 0-24h post-dose >94% (without correction, >78%). No clinically meaningful differences in PK and DPP-4 inhibition parameters were found between Japanese and non-Japanese subjects. Sitagliptin was generally well tolerated and there were no serious adverse experiences or episodes of hypoglycaemia. CONCLUSIONS: The PK and PD findings from this study are consistent with once daily dosing of sitagliptin in Japanese patients with type 2 diabetes.

Double-blind crossover study to assess potential differences in cytochrome P450 3A4 activity in healthy subjects receiving ondansetron plus dexamethasone, with and without aprepitant.

PURPOSE: Because glucocorticoids and the neurokinin-1 receptor antagonist aprepitant influence CYP3A4 activity, this study assessed whether aprepitant added to a 5-HT(3) antagonist and glucocorticoid would affect CYP3A4 induction. METHODS: In this double-blind, 2-period crossover study, 12 subjects were randomized to receive a triple regimen (oral aprepitant [A] 125 mg, intravenous ondansetron [O] 32 mg, and oral dexamethasone [D] 12 mg day 1; A 80 mg and D 8 mg days 2-3; D 8 mg day 4) in 1 of 2 periods, and a dual regimen (O 32 mg and D 20 mg day 1; D 8 mg bid days 2-4); the D dose was adjusted to account for known dexamethasone/aprepitant interaction. Oral (2 mg) and intravenous (1 mg) stable isotope ((13)C(5) (15)N(1))-labeled midazolam were simultaneously given as probes on days -1, 6, 8, 15, and 22 of each period. If the a priori 90% confidence interval for the day 6 geometric mean oral midazolam AUC(0-∞) ratio (triple/dual regimen) of fold-change from baseline was above 0.5, it would be concluded that there was no clinically meaningful between-regimen difference in CYP3A4 activity. RESULTS: Day 6 oral midazolam AUC(0-∞) geometric mean fold-change from baseline was 0.84 (0.30-1.58 with A, 0.46-1.69 without A). The ratio of geometric mean oral midazolam AUC(0-∞) fold-changes was 1.00 (90% confidence interval 0.80, 1.25). CONCLUSIONS: Aprepitant plus a 5-HT(3) antagonist and dexamethasone is unlikely to have a significant additional inductive effect on CYP3A4 activity beyond that of the dual regimen.

Bioequivalence of sitagliptin/metformin fixed-dose combination tablets and concomitant administration of sitagliptin and metformin in healthy adult subjects: a randomized, open-label, crossover study.

BACKGROUND: Treatment with an oral antihyperglycaemic agent administered as monotherapy is often unsuccessful at achieving or maintaining glycaemic control in patients with type 2 diabetes mellitus. The combined use of sitagliptin and metformin is an effective treatment for type 2 diabetes mellitus, consistent with the complementary mechanisms of action by which these two agents improve glucose control. OBJECTIVES: To establish bioequivalence between sitagliptin/metformin fixed-dose combination (FDC) tablets (Janumet®) and co-administration of corresponding doses of sitagliptin and metformin as individual tablets. METHODS: This was an randomized, open-label, two-part, two-period crossover study, which included a total of 48 healthy subjects, 24 subjects per part (parts I and II). Within each part, subjects were assigned to receive treatments in random order; treatment periods were separated by a washout interval of at least 7 days. Eligible study participants included healthy, non-smoking (within previous 6 months), male and female subjects aged between 18 and 45 years with a body mass index ≤32 kg/m². Part I consisted of treatments A (co-administration of sitagliptin 50 mg and metformin 500 mg) and B (sitagliptin/metformin 50 mg/500 mg FDC tablet); part II consisted of treatments C (co-administration of sitagliptin 50 mg and metformin 1000 mg) and D (sitagliptin 50 mg/metformin 1000 mg FDC tablet). Blood samples were collected pre-dose and up to 72 hours post-dose in each treatment period for determination of plasma sitagliptin and metformin concentrations and calculation of the respective pharmacokinetic parameters. The area under the plasma concentration-time curve from time zero to infinity (AUC(∞)) and the maximum plasma concentration (C(max)) for both sitagliptin and metformin were designated as the primary and secondary study endpoints, respectively, and analysed using an ANOVA model after logarithmic transformation of the data. Bioequivalence was established if the 90% confidence intervals (CIs) for the geometric mean ratios (GMRs; FDC tablet/co-administration) of the AUC(∞) and C(max) for both sitagliptin and metformin fell within pre-specified bounds of (0.80, 1.25). RESULTS: The GMRs (90% CI) for the AUC(∞) of sitagliptin 50 mg and metformin 500 mg were 0.98 (0.96, 1.00) and 1.0 (0.95, 1.04), respectively, and for C(max) of sitagliptin and metformin were 1.00 (0.94, 1.06) and 1.00 (0.94, 1.06), respectively. The GMRs (90% CI) for the AUC(∞) of sitagliptin 50 mg and metformin 1000 mg (part II) were 0.97 (0.95, 0.99) and 1.00 (0.94, 1.07), respectively, and for the C(max) of sitagliptin and metformin were 0.94 (0.88, 1.01) and 1.01 (0.93, 1.10), respectively. In both part I and part II, the 90% CIs of the GMRs of the AUC(∞) and C(max) for both sitagliptin and metformin all fell within the pre-specified bioequivalence bounds of (0.80, 1.25). Administration of single doses of sitagliptin/metformin 50 mg/500 mg (part I) and 50 mg/1000 mg FDC tablets (part II) and co-administration of corresponding doses of sitagliptin and metformin as individual tablets were generally well tolerated. CONCLUSION: The sitagliptin/metformin 50 mg/500 mg and 50 mg/1000 mg FDC tablets are bioequivalent to co-administration of corresponding doses of sitagliptin and metformin as individual tablets and support bioequivalence to the sitagliptin/metformin 50 mg/850 mg tablet strength. These results indicate that the safety and efficacy profile of co-administration of sitagliptin and metformin can be extended to the sitagliptin/metformin FDC tablets.

A thorough QTc study to assess the effect of sitagliptin, a DPP4 inhibitor, on ventricular repolarization in healthy subjects.

A randomized, double-blind, placebo-controlled, 4-period crossover study was performed with a single oral dose of sitagliptin (100 mg, 800 mg), moxifloxacin (400 mg), and placebo in order to provide a rigorous assessment of the effect of sitagliptin on ventricular repolarization based on the ICH E14 guidance. The clinical dose of sitagliptin 100 mg was not associated with an increase in QTc interval, corrected using the Fridericia correction (QTcf), at any time point. The supratherapeutic 800-mg dose of sitagliptin was generally well tolerated and was associated with minimal, clinically insignificant prolongation of the QTcf interval at concentrations approximately 11-fold higher than maximal concentrations following the 100-mg clinical dose. The PK/QTc model demonstrated a shallow relationship between the plasma concentration of sitagliptin and the placebo-subtracted QTcf change from baseline, with a 0.59-millisecond increase in QTc for every 1000-nM increment in sitagliptin plasma concentration. The sensitivity of the assay to detect modest increases in QTc interval was established with the active control moxifloxacin. In conclusion, at clinically relevant concentrations, sitagliptin is not associated with clinically meaningful QTcf prolongation.

Effect of rifampin, a potent inducer of drug-metabolizing enzymes, on the pharmacokinetics of raltegravir.

Raltegravir is a human immunodeficiency virus type 1 integrase strand transfer inhibitor that is metabolized by glucuronidation via UGT1A1 and may be affected by inducers of UGT1A1, such as rifampin (rifampicin). Two pharmacokinetic studies were performed in healthy subjects: study 1 examined the effect of administration of 600-mg rifampin once daily on the pharmacokinetics of a single dose of 400-mg raltegravir, and study 2 examined the effect of 600-mg rifampin once daily on the pharmacokinetics of 800-mg raltegravir twice daily compared to 400-mg raltegravir twice daily without rifampin. Raltegravir coadministered with rifampin resulted in lower plasma raltegravir concentrations: in study 1, the geometric mean ratios (GMRs) and 90% confidence intervals (90% CIs) for the plasma raltegravir concentration determined 12 h postdose (C(12)), area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)), and maximum concentration of drug in plasma (C(max)) (400-mg raltegravir plus rifampin/400-mg raltegravir) were 0.39 (0.30, 0.51), 0.60 (0.39, 0.91), and 0.62 (0.37, 1.04), respectively. In study 2, the GMRs and 90% CIs for raltegravir C(12), AUC(0-12), and C(max) (800-mg raltegravir plus rifampin/400-mg raltegravir) were 0.47 (0.36, 0.61), 1.27 (0.94, 1.71), and 1.62 (1.12, 2.33), respectively. Doubling the raltegravir dose to 800 mg when coadministered with rifampin therefore compensates for the effect of rifampin on raltegravir exposure (AUC(0-12)) but does not overcome the effect of rifampin on raltegravir trough concentrations (C(12)). Coadministration of rifampin and raltegravir is not contraindicated; however, caution should be used, since raltegravir trough concentrations in the presence of rifampin are likely to be at the lower limit of clinical experience.

Effect of tipranavir-ritonavir on pharmacokinetics of raltegravir.

Raltegravir (RAL) is a novel and potent human immunodeficiency virus type 1 integrase inhibitor that is predominantly metabolized via glucuronidation. The protease inhibitor combination tipranavir (TPV) at 500 mg and ritonavir (RTV) at 200 mg (TPV-RTV) has inhibitory and inductive effects on metabolic enzymes, which includes the potential to induce glucuronosyltransferase. Because RAL may be coadministered with TPV-RTV, there is the potential for the induction of RAL metabolism. Consequently, we assessed the effect of TPV-RTV on the pharmacokinetics of RAL and the safety and tolerability of this combination. Eighteen healthy adults were enrolled in this open-label study. The participants received RAL at 400 mg twice daily for 4 days (period 1) and TPV-RTV twice daily for 7 days (period 2), followed immediately by 400 mg RAL with TPV-RTV twice daily for 4 days (period 3). Under steady-state conditions, the RAL concentration at 12 h (C(12)) was decreased when RAL was administered with TPV-RTV (geometric mean ratio [GMR], 0.45; 90% confidence interval [CI] 0.31, 0.66; P = 0.0021); however, the area under the concentration-time curve from time zero to 12 h (GMR, 0.76; 90% CI, 0.49, 1.19; P = 0.2997) and the maximum concentration in serum (GMR, 0.82; 90% CI, 0.46, 1.46; P = 0.5506) were not substantially affected. There were no serious adverse experiences or discontinuations due to study drug-related adverse experiences, and RAL coadministered with TPV-RTV was generally well tolerated. Although the RAL C(12) was decreased with TPV-RTV in this study, favorable efficacy data collected in phase III studies substantiate that TPV-RTV may be coadministered with RAL without dose adjustment.

Efficacy assessment of a cell-mediated immunity HIV-1 vaccine (the Step Study): a double-blind, randomised, placebo-controlled, test-of-concept trial.

BACKGROUND: Observational data and non-human primate challenge studies suggest that cell-mediated immune responses might provide control of HIV replication. The Step Study directly assessed the efficacy of a cell-mediated immunity vaccine to protect against HIV-1 infection or change in early plasma HIV-1 levels. METHODS: We undertook a double-blind, phase II, test-of-concept study at 34 sites in North America, the Caribbean, South America, and Australia. We randomly assigned 3000 HIV-1-seronegative participants by computer-generated assignments to receive three injections of MRKAd5 HIV-1 gag/pol/nef vaccine (n=1494) or placebo (n=1506). Randomisation was prestratified by sex, adenovirus type 5 (Ad5) antibody titre at baseline, and study site. Primary objective was a reduction in HIV-1 acquisition rates (tested every 6 months) or a decrease in HIV-1 viral-load setpoint (early plasma HIV-1 RNA measured 3 months after HIV-1 diagnosis). Analyses were per protocol and modified intention to treat. The study was stopped early because it unexpectedly met the prespecified futility boundaries at the first interim analysis. This study is registered with ClinicalTrials.gov, number NCT00095576. FINDINGS: In a prespecified interim analysis in participants with baseline Ad5 antibody titre 200 or less, 24 (3%) of 741 vaccine recipients became HIV-1 infected versus 21 (3%) of 762 placebo recipients (hazard ratio [HR] 1.2 [95% CI 0.6-2.2]). All but one infection occurred in men. The corresponding geometric mean plasma HIV-1 RNA was comparable in infected male vaccine and placebo recipients (4.61 vs 4.41 log(10) copies per mL, one tailed p value for potential benefit 0.66). The vaccine elicited interferon-gamma ELISPOT responses in 75% (267) of the 25% random sample of all vaccine recipients (including both low and high Ad5 antibody titres) on whose specimens this testing was done (n=354). In exploratory analyses of all study volunteers, irrespective of baseline Ad5 antibody titre, the HR of HIV-1 infection between vaccine and placebo recipients was higher in Ad5 seropositive men (HR 2.3 [95% CI 1.2-4.3]) and uncircumcised men (3.8 [1.5-9.3]), but was not increased in Ad5 seronegative (1.0 [0.5-1.9]) or circumcised (1.0 [0.6-1.7]) men. INTERPRETATION: This cell-mediated immunity vaccine did not prevent HIV-1 infection or reduce early viral level. Mechanisms for insufficient efficacy of the vaccine and the increased HIV-1 infection rates in subgroups of vaccine recipients are being explored.

Minimal effects of ritonavir and efavirenz on the pharmacokinetics of raltegravir.

Raltegravir is a novel human immunodeficiency virus type 1 (HIV-1) integrase strand transfer inhibitor with potent in vitro activity against HIV-1 (95% inhibitory concentration = 31 nM in 50% human serum). The possible effects of ritonavir and efavirenz on raltegravir pharmacokinetics were separately examined. Two clinical studies of healthy subjects were conducted: for ritonavir plus raltegravir, period 1, 400 mg raltegravir; period 2, 100 mg ritonavir every 12 h for 16 days with 400 mg raltegravir on day 14; for efavirenz plus raltegravir, period 1, 400 mg raltegravir; period 2, 600 mg efavirenz once daily for 14 days with 400 mg raltegravir on day 12. In the presence of ritonavir, raltegravir pharmacokinetics were weakly affected: the plasma concentration at 12 h (C(12 h)) geometric mean ratio (GMR) (90% confidence interval [CI]) was 0.99 (0.70, 1.40), area under the concentration-time curve from zero to infinity (AUC(0-infinity)) was 0.84 (0.70, 1.01), and maximum concentration of drug in serum (C(max)) was 0.76 (0.55, 1.04). In the presence of efavirenz, raltegravir pharmacokinetics were moderately to weakly reduced: C(12 h) GMR (90% CI) was 0.79 (0.49, 1.28); AUC(0-infinity) was 0.64 (0.52, 0.80); and C(max) was 0.64 (0.41, 0.98). There were no substantial differences in the time to maximum concentration of drug in plasma or the half-life. Plasma concentrations of raltegravir were not substantially affected by ritonavir. Though plasma concentrations of raltegravir were moderately to weakly reduced by efavirenz, the degree of this reduction was not clinically meaningful. No dose adjustment is required for raltegravir with coadministration with ritonavir or efavirenz.

Concomitant use of the oral pentavalent human-bovine reassortant rotavirus vaccine and oral poliovirus vaccine.

OBJECTIVES: The live oral pentavalent rotavirus vaccine (PRV) is well tolerated and highly efficacious against rotavirus gastroenteritis. This open-label, multicenter study evaluated the immunogenicity and safety of coadministering oral poliovirus vaccine (OPV) with PRV. METHODS: From 2005 to 2006, healthy 6- to 12-week-old Latin American infants were randomized to PRV and OPV concomitantly or PRV 2-4 weeks before OPV. Three doses of each vaccine were administered 8-10 weeks apart. Subjects did not receive OPV at birth. Routine licensed pediatric vaccines were allowed. Antibody responses to PRV and OPV were evaluated 42 days after the last dose of each vaccine. Adverse events were recorded for 14 days after each study visit. RESULTS: In the concomitant-use group (n = 372), more than 98% of subjects achieved serum-neutralizing antibody titer > or = 1:8 against poliovirus types 1, 2, and 3. The poliovirus seroprotection rate in the concomitant-use group was statistically noninferior to the staggered-use group (n = 363). The immunoglobulin A (IgA) antirotavirus geometric mean titer was 46% lower in the concomitant-use group than in the staggered-use group. However, concomitant use elicited a > or = 3-fold increase (from predose 1 to postdose 3) in serum antirotavirus IgA in 93% of subjects and achieved the definition of noninferiority. Both regimens were similarly well tolerated. CONCLUSIONS: PRV did not interfere with immune responses to OPV. Although coadministration with OPV reduced serum antirotavirus IgA geometric mean titer, seroresponse rates were high and consistent with those observed in previous studies showing high vaccine efficacy. These results support including PRV in vaccination schedules involving OPV.

Lack of a significant drug interaction between raltegravir and tenofovir.

Raltegravir is a novel human immunodeficiency virus type 1 (HIV-1) integrase inhibitor with potent in vitro activity (95% inhibitory concentration of 31 nM in 50% human serum). This article reports the results of an open-label, sequential, three-period study of healthy subjects. Period 1 involved raltegravir at 400 mg twice daily for 4 days, period 2 involved tenofovir disoproxil fumarate (TDF) at 300 mg once daily for 7 days, and period 3 involved raltegravir at 400 mg twice daily plus TDF at 300 mg once daily for 4 days. Pharmacokinetic profiles were also determined in HIV-1-infected patients dosed with raltegravir monotherapy versus raltegravir in combination with TDF and lamivudine. There was no clinically significant effect of TDF on raltegravir. The raltegravir area under the concentration time curve from 0 to 12 h (AUC(0-12)) and peak plasma drug concentration (C(max)) were modestly increased in healthy subjects (geometric mean ratios [GMRs], 1.49 and 1.64, respectively). There was no substantial effect of TDF on raltegravir concentration at 12 h postdose (C(12)) in healthy subjects (GMR [TDF plus raltegravir-raltegravir alone], 1.03; 90% confidence interval [CI], 0.73 to 1.45), while a modest increase (GMR, 1.42; 90% CI, 0.89 to 2.28) was seen in HIV-1-infected patients. Raltegravir had no substantial effect on tenofovir pharmacokinetics: C(24), AUC, and C(max) GMRs were 0.87, 0.90, and 0.77, respectively. Coadministration of raltegravir and TDF does not change the pharmacokinetics of either drug to a clinically meaningful degree. Raltegravir and TDF may be coadministered without dose adjustments.

Atazanavir modestly increases plasma levels of raltegravir in healthy subjects.

Raltegravir is an HIV integrase inhibitor that is metabolized through glucuronidation by uridine diphosphate glucuronosyltransferase 1A1, and its use is anticipated in combination with atazanavir (a uridine diphosphate glucuronosyltransferase 1A1 inhibitor). Two pharmacokinetic studies of healthy subjects assessed the effect of multiple-dose atazanavir or ritonavir-boosted atazanavir on raltegravir levels in plasma. Atazanavir and atazanavir plus ritonavir modestly increase plasma levels of raltegravir.

Sitagliptin, an dipeptidyl peptidase-4 inhibitor, does not alter the pharmacokinetics of the sulphonylurea, glyburide, in healthy subjects.

AIMS: Sitagliptin, a dipeptidyl peptidase-4 inhibitor, is an incretin enhancer that is approved for the treatment of Type 2 diabetes. Sitagliptin is mainly renally eliminated and not an inhibitor of CYP450 enzymes in vitro. Glyburide, a sulphonylurea, is an insulin sensitizer and mainly metabolized by CYP2C9. Since both agents may potentially be co-administered, the purpose of this study was to examine the effects of sitagliptin on glyburide pharmacokinetics. METHODS: In this open-label, randomized, two-period crossover study, eight healthy normoglycaemic subjects, 22-44 years old, received single 1.25-mg doses of glyburide alone in one period and co-administered with sitagliptin on day 5 following a multiple-dose regimen for sitagliptin (200-mg q.d. x 6 days) in the other period. RESULTS: The geometric mean ratios and 90% confidence intervals [(glyburide + sitagliptin)/glyburide] for AUC(0-infinity) and C(max) were 1.09 (0.96, 1.24) and 1.01 (0.84, 1.23), respectively. CONCLUSION: Sitagliptin does not alter the pharmacokinetics of glyburide in healthy subjects.

Effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on blood pressure in nondiabetic patients with mild to moderate hypertension.

The effect of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on ambulatory blood pressure was assessed in nondiabetic patients with mild to moderate hypertension in a randomized, double-blind, placebo-controlled, 3-period crossover study. Nineteen patients on stable treatment with antihypertensive agent(s) received sitagliptin 100 mg b.i.d., 50 mg b.i.d., or placebo for 5 days, with at least a 7-day washout interval between periods. Twenty-four-hour ambulatory blood pressure, including systolic blood pressure, diastolic blood pressure, and mean arterial pressure, were monitored on days 1 and 5. Relative to placebo on day 1, the mean difference in 24-hour systolic blood pressure was -0.9 mm Hg (90% confidence interval: -2.9 to 1.1; P = .46) with sitagliptin 50 mg b.i.d. and -2.8 mm Hg (90% confidence interval: -4.9 to -0.8; P < .05) with 100 mg b.i.d. On day 5, the mean difference in 24-hour systolic blood pressure was -2.0 mm Hg (90% confidence interval: -3.5 to -0.4; P < .05) with 50 mg b.i.d. and -2.2 mm Hg (90% confidence interval: -3.7 to -0.6; P < .05) with 100 mg b.i.d. relative to placebo. For 24-hour diastolic blood pressure, there were no between-group differences in mean 24-hour diastolic blood pressure on day 1. On day 5, sitagliptin 50 mg and 100 mg b.i.d significantly (P < .05) lowered mean 24-hour diastolic blood pressure by -1.8 mm Hg (90% confidence interval: -2.8 to -0.8) and -1.6 mm Hg (90% confidence interval: -2.6 to -0.7), respectively, relative to placebo. Sitagliptin produced small but statistically significant reductions of 2 mm Hg to 3 mm Hg in 24-hour ambulatory blood pressure measurements acutely (day 1) and at steady state (day 5), and was generally well tolerated in nondiabetic patients with mild to moderate hypertension.

Lack of a pharmacokinetic effect of raltegravir on midazolam: in vitro/in vivo correlation.

Raltegravir is a novel HIV-1 integrase inhibitor with potent in vitro activity (95% inhibitory concentration = 33 nM in 50% human serum). In vitro characterization of raltegravir inhibition potential was assessed against a panel of cytochrome P450 (CYP) enzymes. An open-label, 2-period study was conducted to assess the effect of raltegravir on the pharmacokinetics of midazolam, a sensitive CYP 3A4 probe substrate: period 1, 2.0 mg of midazolam; period 2, 400 mg of raltegravir every 12 hours for 14 days with 2.0 mg of midazolam on day 14. There was no meaningful in vitro effect of raltegravir on inhibition of a panel of CYP enzymes and induction of CYP 3A4. In the presence of raltegravir, midazolam area under the curve extrapolated to infinity (AUC(0-infinity)) and maximum plasma concentration (C(max)) geometric mean ratios were similar (geometric mean ratios and 90% confidence intervals: 0.92 [0.82, 1.03] (P = .208) and 1.03 [0.87, 1.22] (P = .751), respectively). No substantial differences were observed in T(max) (P = .750) or apparent half-life (P = .533) of midazolam. Plasma levels of midazolam were not substantially affected by raltegravir, which implies that raltegravir is not a clinically important inducer or inhibitor of CYP 3A4 and that raltegravir would not be expected to affect the pharmacokinetics of other drugs metabolized by CYP 3A4 to a clinically meaningful extent.

Effect of the cholesteryl ester transfer protein inhibitor, anacetrapib, on lipoproteins in patients with dyslipidaemia and on 24-h ambulatory blood pressure in healthy individuals: two double-blind, randomised placebo-controlled phase I studies.

BACKGROUND: The inhibition of cholesteryl ester transfer protein (CETP) is considered a potential new mechanism for treatment of dyslipidaemia. Anacetrapib (MK-0859) is a CETP inhibitor currently under development. We aimed to assess anacetrapib's effects as monotherapy on low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) and on 24-h ambulatory blood pressure. METHODS: We did two double-blind, randomised, placebo-controlled phase I studies. In the first study, 50 patients with dyslipidaemia (LDL-C 100-190 mg/dL; 40 active, 10 placebo) aged 18-75 years received anacetrapib doses of 0, 10, 40, 150, or 300 mg orally once a day with a meal for 28 days. Standard lipid and lipoprotein monitoring, safety monitoring, and anacetrapib concentrations for pharmacokinetics were done. In the second study, 22 healthy participants aged 45-75 years received either 150 mg of anacetrapib once a day or matching placebo with a meal for 10 days in each crossover period, in a randomised sequence, with at least a 14-day washout between the treatment periods. Continuous 24-h ambulatory blood pressure monitoring was done on day -1 and day 10 of each treatment period in this study. The primary or secondary endpoints of safety and tolerability were assessed in both studies by monitoring clinical adverse experiences, physical examinations, vital signs, 12-lead electrocardiogram, and laboratory safety. Analysis was per protocol. These trials are registered with ClinicalTrials.gov, number NCT00565292 and NCT00565006. FINDINGS: In the dyslipidaemia study, one patient withdrew consent and one was excluded from the data analysis for HDL-C and LDL-C because complete pre-dose measurements were not available. Anacetrapib produced dose-dependent lipid-altering effects with peak lipid-altering effects of 129% (mean 51.1 [SD 3.8]-114.9 [7.9] mg/dL) increase in HDL-C and a 38% (138.2 [11.4]-77.6 [7.9] mg/dL) decrease in LDL-C in patients with dyslipidaemia. In the 24-h ambulatory blood pressure study in healthy individuals, least squares difference between anacetrapib and placebo groups on day 10 were 0.60 (90% CI -1.54 to 2.74; p=0.634) mm Hg for systolic blood pressure and 0.47 (90% CI -0.90 to 1.84; p=0.561) mm Hg for diastolic blood pressure. INTERPRETATION: Anacetrapib seems to exhibit HDL-C increases greater than those seen with other investigational drugs in this class and LDL-C lowering effects similar to statins. Despite greater lipid-altering effects relative to other members of this class, anacetrapib seems not to increase blood pressure, suggesting that potent CETP inhibition by itself might not lead to increased blood pressure.