Real-time effects of Cd(II) on the cellular membrane permeability.

Cell membrane permeability is one of the main indicators of cytotoxicity and related to many critical biological pathways. Here, we determined the Cd2+-induced membrane permeability of human MCF-7 cells using ferrocene methanol molecular probes based on scanning electrochemical microscopy (SECM). The cell height and topography were examined with an impermeable Ru(NH3)6Cl3 probe. The membrane permeability exhibited no significant changes when the Cd2+ incubation time was less than 2 h and its concentration was less than 40 µM. The permeability increased when the Cd2+ concentration was greater than 60 µM, or when the incubation time was longer than 3 h. From the combined 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and cytoskeleton imaging experiments, it was found that the changes occurred because the cells exhibited a defensive mode and their membranes contracted when treated with a low concentration of Cd2+ for a short time. However, the cell membranes were irreversibly damaged when the cytoskeleton structures were destroyed, and the cell activities decreased at high concentrations over long periods. Interestingly, through the comparison with an x-scan study, it was found that DPV technology shows a higher performance in the detection of changes in the membrane permeability. Using a combination of cytoskeleton fluorescence imaging and cell-viability tests, the effect of the cadmium metal on the cell membrane permeability can be explored deeper and more comprehensively. This study provides a new idea for exploring the changes in the cell membrane permeability and may be helpful for rapid evaluation of cytotoxicity.

Randomized, controlled study of telcagepant in patients with migraine and coronary artery disease.

OBJECTIVE: To evaluate the efficacy of telcagepant in patients with migraine and coronary artery disease. BACKGROUND: Calcitonin gene-related peptide receptor antagonists, such as telcagepant, may be useful for acute migraine treatment in patients with cardiovascular disease, a population for whom triptans are contraindicated. METHODS: Randomized, double-blind, two-period (6 weeks per period) crossover study in patients with stable coronary artery disease and migraine. Patients were randomized 1:1 to either: (1) Period 1: telcagepant (280-mg tablet/300-mg capsule), Period 2: acetaminophen (1000-mg); or (2) Period 1: placebo for attack 1 then acetaminophen for subsequent attacks, Period 2: telcagepant. Patients could treat up to 12 migraine attacks per period to assess the tolerability of telcagepant. The primary efficacy analysis evaluated telcagepant vs placebo on 2-hour pain freedom during the first attack of Period 1. RESULTS: One hundred and sixty-five of the planned 400 patients were enrolled, and 114 took at least one dose of treatment. Telcagepant was not statistically different from placebo for 2-hour pain freedom (25.0% vs 18.9%, odds ratio = 1.62 [95% confidence interval: 0.62, 4.25]). The median number of attacks treated per period was 3. No cardiovascular thrombotic adverse events occurred within 14 days of dosing. CONCLUSION: The study was underpowered due to enrollment difficulties and did not demonstrate a significant efficacy difference between telcagepant and placebo for the treatment of a migraine attack in patients with stable coronary artery disease. Telcagepant was generally well tolerated for acute intermittent migraine treatment in these patients.

Inhibitory effects of zinc chloride (ZnCl2), n-acetyl-L-cysteine (NAC), and calcium/calmodulin dependent protein kinase II inhibitor (KN93) on Cd2+-induced abnormal cell morphology and membrane permeability.

Cadmium (Cd) could reduce abnormal cell morphology and membrane permeability, however, there are few studies on the detoxification of Cd-reduced cell membrane toxicity. In the present study, we firstly studied the effects of zinc chloride (ZnCl2), n-acetyl-L-cysteine (NAC), and calcium/calmodulin dependent protein kinase II inhibitor (KN93) on cell membrane permeability, respectively; then, we studied the inhibitory effects of ZnCl2, NAC, and KN93 on Cd2+-induced abnormal cell membrane permeability by scanning electrochemical microscopy (SECM) scanning imaging, transverse scanning curve and DPV technology. Our results showed that 10 µmol·L-1 ZnCl2, 0.5 mmol·L-1 NAC and 5 µmol·L-1 KN93 could significantly improve the activity of MCF-7 cells, while did not destroy the cell morphology and membrane permeability. 0.5 mmol·L-1 NAC and 5 µmol·L-1 KN93 could significantly inhibit the effects of Cd2+ on the morphology and membrane permeability of MCF-7 cells (p < 0.01). 10 µmol·L-1 ZnCl2 could significantly inhibit the effect of Cd on the membrane permeability of MCF-7 cells, however, it cannot completely eliminate the morphological changes of MCF-7 cells caused by Cd2+. The results of cell activity experiment showed that 10 µmol·L-1 ZnCl2, 0.5 mmol·L-1 NAC and 5 µmol·L-1 KN93 could inhibit the effect of Cd2+ on the activity of MCF-7 cells. By comparing the inhibitory effects of ZnCl2, NAC and KN93 on Cd2+- induced cytotoxicity, 5 µmol·L-1 KN93 had the robust effect on the maintenance of MCF-7 cell morphology and cell membrane integrity. Our research provided evidence on Zn supplement, NAC as antioxidant drugs, and KN93 as special inhibitor for the detoxification of Cd2+-reduced abnormal cell morphology and membrane permeability.

Efficacy and tolerability of rizatriptan for the treatment of acute migraine in sumatriptan non-responders.

OBJECTIVE: The study was carried out to assess the efficacy and tolerability of rizatriptan orally disintegrating tablet (ODT) for treating acute migraine in patients who are non-responders to sumatriptan. BACKGROUND: Many migraineurs report dissatisfaction with sumatriptan efficacy. It is unclear whether sumatriptan 100 mg non-responders will respond to other triptans. METHODS: This was a randomized, placebo-controlled, double-blind study in adults with >1-year history of ICHD-II (International Classification of Headache Disorders, second edition) migraine who reported that they generally do not respond to sumatriptan (≥50% unsatisfactory response). In the baseline phase, participants treated a single moderate/severe migraine attack with open-label generic sumatriptan 100 mg. Those who continued to experience moderate/severe pain at two hours post-dose were eligible to enter the double-blind treatment phase, during which participants treated three migraine attacks in crossover fashion (two with rizatriptan 10-mg ODT, one with placebo) after being randomly assigned to one of three treatment sequences (1 : 1 : 1 ratio). The primary endpoint was two-hour pain relief. RESULTS: A total of 102 (94%) participants treated at least one study migraine. Pain relief at two hours was significantly greater with rizatriptan compared with placebo (51% vs. 20%, p < .001). Response rates also favored rizatriptan on two-hour pain freedom (22% vs. 12%, p = .013) as well as 24-hour sustained pain relief (38% vs. 14%, p < .001) and sustained pain freedom (20% vs. 11%, p = .036). Treatment was generally well tolerated. CONCLUSION: Rizatriptan 10-mg ODT was superior to placebo at providing two-hour pain relief and two-hour pain freedom in the treatment of acute migraine in those who do not respond to sumatriptan 100 mg. Rizatriptan was generally well tolerated in this population.

Randomized controlled trial of the CGRP receptor antagonist MK-3207 in the acute treatment of migraine.

BACKGROUND: This study evaluated the CGRP receptor antagonist MK-3207 for acute treatment of migraine. METHODS: Multicenter, double-blind, randomized, placebo-controlled, parallel-group, two-stage adaptive study with two interim efficacy analyses to facilitate optimal dose selection. Migraine patients were initially randomized to MK-3207 2.5, 5, 10, 20, 50 and 100 mg or placebo to treat a moderate/severe migraine. One or more doses were to be discontinued based on the first interim analysis and a lower or higher dose could be added based on the second interim analysis. The primary endpoint was two-hour pain freedom. RESULTS: A total of 547 patients took study medication. After the first interim analysis, the two lowest MK-3207 doses (2.5, 5 mg) were identified as showing insufficient efficacy. Per the pre-specified adaptive design decision rule, only the 2.5-mg group was discontinued and the five highest doses (5, 10, 20, 50, 100 mg) were continued into the second stage. After the second interim efficacy analysis, a 200 mg dose was added due to insufficient efficacy at the top three (20, 50, 100 mg) doses. A positive dose-response trend was demonstrated when data were combined across all MK-3207 doses for two-hour pain freedom (p < .001). The pairwise difference versus placebo for two-hour pain freedom was significant for 200 mg (p < .001) and nominally significant for 100 mg and 10 mg (p < .05). The incidence of adverse events appeared comparable between active treatment groups and placebo, and did not appear to increase with increasing dose. CONCLUSIONS: MK-3207 was effective and generally well tolerated in the acute treatment of migraine.

Efficacy and tolerability of MK-0974 (telcagepant), a new oral antagonist of calcitonin gene-related peptide receptor, compared with zolmitriptan for acute migraine: a randomised, placebo-controlled, parallel-treatment trial.

BACKGROUND: Calcitonin gene-related peptide (CGRP) probably has a role in migraine pathophysiology, and antagonism of its receptors might provide treatment without the vasoconstrictor effects of triptans. We aimed to assess the clinical profile of MK-0974 (telcagepant), an orally bioavailable antagonist of CGRP receptor. METHODS: In a randomised, parallel-treatment, placebo-controlled, double-blind, trial at 81 sites in the Europe and the USA, adults with migraine diagnosed by International Headache Society criteria treated moderate or severe attacks with either oral telcagepant 150 mg or 300 mg, zolmitriptan 5 mg, or placebo. The five co-primary endpoints were pain freedom, pain relief, or absence of photophobia, phonophobia, or nausea at 2 h after treatment. Analysis was by the full analysis set and multiplicity was controlled for with a step-down closed-testing procedure. This trial is registered with ClinicalTrials.gov, number NCT00442936. FINDINGS: 1380 patients were randomly assigned to receive telcagepant 150 mg (n=333) or 300 mg (354), zolmitriptan (345), or placebo (348). Telcagepant 300 mg was more effective than placebo for pain freedom (95 [27%] of 353 patients vs 33 [10%] of 343 [p<0.0001]), pain relief (194 [55%] of 353 vs 95 [28%] of 343 [p<0.0001]), and absences of phonophobia (204 [58%] of 353 vs 126 [37%] of 342 [p<0.0001]), photophobia (180 [51%] of 353 vs 99 [29%] of 342 [p<0.0001]), and nausea (229 [65%] of 352 vs 189 [55%] of 342 [p=0.0061]). Efficacy of telcagepant 300 mg and zolmitriptan 5 mg were much the same, and both were more effective than telcagepant 150 mg. Adverse events were recorded for 31% taking telcagepant 150 mg, 37% taking telcagepant 300 mg, 51% taking zolmitriptan 5 mg, and 32% taking placebo. INTERPRETATION: Telcagepant 300 mg is effective as an acute treatment for migraine with efficacy comparable to that of zolmitriptan 5 mg, but with fewer associated adverse effects. FUNDING: Merck Research Laboratories.

A proof-of-concept-to-confirmatory multiple adaptation design in the development of an anti-viral treatment.

In the clinical development of some new infectious disease drugs, early clinical pharmacology trials may predict with high confidence that the efficacious doses are well below the range of the safety margin. In this case, a dose-ranging study may be unnecessary after a proof-of-concept (PoC) study testing the highest dose. A multi-stage adaptive design spanning both PoC and confirmatory stages is proposed in this context. The design incorporates two interim analyses allowing strategies for stopping, continuing, or expanding the study. A conditional power threshold for a binary endpoint is proposed to assess futility. Additional components of early efficacy and sample size adjustment are also included to enhance the design's flexibility and robustness. Design operating characteristics are evaluated by numerical calculation. We show that the proposed streamlined trial design has the same statistical rigor as a conventional phase 3 clinical trial with adequate power and a properly controlled type 1 error rate. Additional adaptive design options are also investigated and discussed.

Addressing Challenges and Opportunities of "Less Well-Understood" Adaptive Designs.

The draft adaptive design guidance released by FDA in 2010 included references to adaptive study designs that were described as "less well-understood." At that time, there was relatively little regulatory experience with such designs, and their properties were felt to be insufficiently understood. In order to promote greater use of adaptive designs, especially those categorized as less well-understood, the Best Practice Subteam of the DIA Adaptive Designs Scientific Working Group (ADSWG) has worked on describing and characterizing these designs, identifying challenges associated with them and suggesting improvements to design or study conduct aspects that might make them more acceptable. This paper summarizes the work from the subteam.

Estimation of response from longitudinal binary data with nonignorable missing values in migraine trials.

In migraine trials pain relief responses from a headache at specific time points and sustained pain relief response over a period of time are important efficacy measures. When there are missing records of individual time point pain scores and/or headache recurrences during a migraine trial, the common approach used in practice to estimate the sustained response is statistically inconsistent even if the data are missing completely at random. Methods dealing with nonignorable longitudinal missing data usually assume certain models for the missing mechanism which can not be checked as they involve unobserved data. Taking advantage of the specific definition of the 'sustained pain relief' response, we propose two estimating methods based on intuitive imputation, which do not require model assumptions on the missing probability or specification of the correlation structure among the longitudinal observations. The consistency of the proposed methods is discussed in theory and their empirical performances are assessed through intensive simulation studies. The simulation results show that the proposed methods perform well in terms of reducing bias and mean square error except in several extreme cases which are unlikely to happen in real trials. The application of the proposed methods is illustrated in a real data analysis.

Randomized controlled trial of the CGRP receptor antagonist telcagepant for migraine prevention.

OBJECTIVE: To evaluate whether the calcitonin gene-related peptide (CGRP) receptor antagonist telcagepant might be effective for migraine prevention. METHODS: In this randomized, double-blind, placebo-controlled, multicenter trial (ClinicalTrials.gov NCT00797667), patients experiencing 3-14 migraine days during a 4-week baseline were randomized to telcagepant 140 mg, telcagepant 280 mg, or placebo twice daily for 12 weeks. Efficacy was assessed by mean monthly headache days and migraine/probable migraine days (headache plus ≥ 1 associated symptom). RESULTS: The trial was terminated following a recommendation from the Safety Monitoring Board due to hepatotoxicity concerns. At termination, the planned 660 patients had been randomized, 656 had been treated with ≥ 1 dose of study medication, and 14 had completed the trial. The mean treatment duration was 48-50 days. Thirteen patients, all in the telcagepant groups, had an alanine aminotransferase (ALT) elevation ≥ 3 × the upper limit of normal and 7 of these also had an aspartate aminotransferase elevation ≥ 3 × the upper limit of normal. Two patients had very high symptomatic transaminase elevations that occurred within 2-6 weeks of treatment initiation and resolved after treatment discontinuation. The originally planned efficacy analysis over 12 weeks was not performed due to limited data at later time points, but there was evidence that telcagepant resulted in a larger reduction from baseline than placebo for mean monthly headache days (month 1: 140 mg = -2.9, 280 mg = -3.1, placebo = -1.7; p < 0.05) and migraine/probable migraine days (month 1: 140 mg = -2.7, 280 mg = -3.0, placebo = -1.6; p < 0.05). CONCLUSIONS: These data suggest a potential role for CGRP receptor antagonism in migraine prophylaxis. However, the observed aminotransferase elevations do not support the use of telcagepant for daily administration. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that in patients with migraine, telcagepant taken daily reduces headache days by 1.4 days per month compared to placebo and causes 2.5% of patients to have elevations of serum ALT levels.

Adaptive vs. group sequential self-designing trials.

This is a discussion of the paper. 'Repeated Confidence Intervals in Self-Designing Clinical Trials and Switching between Non-Inferiority and Superinferiority' by Joachim Hartung and Guido Knapp, appearing in this special issue on adaptive designs.

Conditional and unconditional confidence intervals following a group sequential test.

After a group sequential test, the naive confidence interval (CI) is usually biased in the sense that it does not cover the true parameter at the correct nominal level. Furthermore, when the stopping time is taken into account, the actual conditional confidence coverage probability can be much less accurate. In this article, we study the conditional coverage probability and other related properties of the naive CI and different versions of exact CI's. It is demonstrated that only correcting the overall confidence level does not necessarily improve the confidence level at any given stopping stage. Conditional inference can be applied to construct an exact conditional CI but it is not without serious undesirable properties. We propose a two-step restricted conditional confidence interval (RCCI) which considerably improves the conditional confidence level while minimizing the undesirable properties. Numerical comparisons are made between the proposed method and existing methods. The results show that the RCCI not only improves the conditional coverage probability considerably from the exact CI's but also is free of the major undesirable properties displayed by the pure conditional CI. Differences between the conditional and unconditional CI's and their respective strengths are also discussed.

Conditional bias of point estimates following a group sequential test.

Repeated significance testing in a sequential experiment not only increases the overall type I error rate of the false positive conclusion but also causes biases in estimating the unknown parameter. In general, the test statistics in a sequential trial can be properly approximated by a Brownian motion with a drift parameter at interim looks. The unadjusted maximum likelihood estimator can be potentially very biased due to the possible early stopping rule at any interim. In this paper, we investigate the conditional and marginal biases with focus on the conditional one upon the stopping time in estimating the Brownian motion drift parameter. It is found that the conditional bias may be very serious for existing point estimation methods, even if the unconditional bias is satisfactory. New conditional estimators are thus proposed, which can significantly reduce the conditional bias from unconditional estimators. The results of Monte-Carlo studies show that the proposed estimators can provide a much smaller conditional bias and MSE than the naive MLE and a Whitebead's bias reduced estimator.