Randomized trial of AT-1015 for treatment of intermittent claudication. A novel 5-hydroxytryptamine antagonist with no evidence of efficacy

Quality of the assessment of primary and secondary endpoints in claudication and critical leg ischemia trials

Clinical trials in peripheral arterial disease (PAD) require an accurate definition of the disease for inclusion; they typically use treadmill testing, questionnaires and hemodynamic measures as primary and secondary endpoints. Trials of new pharmacologic therapies for PAD often employ multiple clinical sites with presumed expertise in the diagnosis and management of PAD as well as in clinical trials. However, considerable variability has been observed in the assessment of endpoints used in PAD trials, as well as a marked placebo response with treadmill testing. This variability and placebo response impact adversely on overall trial integrity, necessitate an inflated sample size, and may contribute to the large number of recently negative claudication trials. We hypothesized that site monitoring visits for evaluating testing methods would identify and characterize several critical issues that would contribute to poor testing quality. One hundred sites participating in three claudication trials for which peak walking time on the treadmill was the primary endpoint, and 16 sites participating in a critical leg ischemia study for which transcutaneous oxygen tension (TcPO2) was the primary endpoint were evaluated. Each site was visited one or more times by a clinical monitor trained in conducting a ‘site endpoint evaluation visit’ focusing on equipment, physical set-up of the room in which testing was to be conducted, and the site staff’s ability to conduct each of the specific measurements. Full reports were generated that covered a number of technical issues for each measurement and data were extracted from these reports to summarize the testing problems encountered at each site. Problems with treadmill testing were common. For example, 92% of sites had problems with their treadmill equipment, 58% did not perform proper treadmill familiarization, 24% did not start the treadmill test appropriately, 24% did not conduct the test properly, and 15% did not properly conclude the test to determine the peak walking time of the participant. Similar problems were encountered with the ankle-brachial index test, the administration of questionnaires and measurement of the TcPO2. Major deficiencies were identified at the majority of sites in the assessment of primary and secondary endpoints in PAD trials. These errors and improper testing provide a potential explanation for the wide variability and placebo responses observed in claudication and critical leg ischemia trials. Site interventions need to address these deficiencies in measurement to improve the quality of PAD trials.

Sarpogrelate, a 5-HT2A receptor antagonist in intermittent claudication. A Phase II European study

This was a multinational, multicentre, double-blind Phase II study in Europe to evaluate the efficacy and safety of two dose regimens (200 mg bid and 200 mg tid) of sarpogrelate (MCI-9042, 5-HT2A receptor antagonist) compared to placebo in patients with stable, moderately severe intermittent claudication. Following a single-blind placebo run-in period of 6 weeks, 364 (309 male and 55 female) patients (59.2 ± 8.4 years, mean SD) were randomized to receive sarpogrelate 200 mg bid, 200 mg tid or placebo for 24 weeks with a follow-up of 8 weeks. The primary objective was the increase of absolute claudication distance (ACD) at the end of treatment (week 24) compared to placebo. Analysis of covariance (ANCOVA) was performed on the log-transformed percentage of baseline ACD: loge (ACD/baseline). A responder analysis (defined as a 50% improvement in ACD) was also performed. There was a marked training/placebo effect on the ACD which persisted up to 16 weeks. At 24 weeks the primary objective did not reach statistical significance (200 mg bid vs placebo, p = 0.225; 200 mg tid vs placebo, p = 0.580). In the responder analysis, 200 mg bid showed a statistically significant difference vs placebo ( p = 0.035). In the exploratory analysis with completers (patients completing all treadmill tests), there was a statistical difference in ACD/baseline change for 200 mg bid ( p = 0.035) and in the responder analysis for 200 mg tid ( p = 0.044) at 24 weeks compared to placebo. Both treatments showed a carry-over effect for ACD during the 8-week follow-up (weeks 28-32). The treatment was well tolerated and no clinically significant safety concerns were reported. In conclusion, the study results confirm that sarpogrelate is well tolerated and although the primary endpoint failed to reach statistical significance, the responder analysis showed an increased absolute walking distance, which makes a further trial warranted, including a larger population, and possibly also a longer treatment period.

Exercise performance and peripheral vascular insufficiency improve with AMPK activation in high-fat diet-fed mice

Intermittent claudication is a form of exercise intolerance characterized by muscle pain during walking in patients with peripheral artery disease (PAD). Endothelial cell and muscle dysfunction are thought to be important contributors to the etiology of this disease, but a lack of preclinical models that incorporate these elements and measure exercise performance as a primary end point has slowed progress in finding new treatment options for these patients. We sought to develop an animal model of peripheral vascular insufficiency in which microvascular dysfunction and exercise intolerance were defining features. We further set out to determine if pharmacological activation of 5'-AMP-activated protein kinase (AMPK) might counteract any of these functional deficits. Mice aged on a high-fat diet demonstrate many functional and molecular characteristics of PAD, including the sequential development of peripheral vascular insufficiency, increased muscle fatigability, and progressive exercise intolerance. These changes occur gradually and are associated with alterations in nitric oxide bioavailability. Treatment of animals with an AMPK activator, R118, increased voluntary wheel running activity, decreased muscle fatigability, and prevented the progressive decrease in treadmill exercise capacity. These functional performance benefits were accompanied by improved mitochondrial function, the normalization of perfusion in exercising muscle, increased nitric oxide bioavailability, and decreased circulating levels of the endogenous endothelial nitric oxide synthase inhibitor asymmetric dimethylarginine. These data suggest that aged, obese mice represent a novel model for studying exercise intolerance associated with peripheral vascular insufficiency, and pharmacological activation of AMPK may be a suitable treatment for intermittent claudication associated with PAD.

Perspectives on optimizing trial design and endpoints in peripheral arterial disease: a case for imaging-based surrogates as endpoints of functional efficacy

Surrogate endpoints are important for validation of mechanism, early proof of concept, and the rational design of clinical trials for regulatory approval of drugs. The recent failure of several drugs in peripheral arterial disease (PAD) and in atherosclerosis highlights the importance of understanding drug effect and is a clarion call for better endpoints. This review focuses on aspects relating to the current state of surrogate endpoints in PAD and reviews emerging endpoints using imaging approaches that may have the potential of improving study design in PAD.

Assessment of functional status and quality of life in claudication

BACKGROUND

Treadmill walking is commonly used to evaluate walking impairment and efficacy of treatment for intermittent claudication (IC) in clinical and research settings. Although this is an important measure, it does not provide information about how patients perceive the effects of their treatments on more global measures of health-related quality of life (HRQOL).

METHODS

PubMed/Medline was searched to find publications about the most commonly used questionnaires to assess functional status and/or general and disease-specific HRQOL in patients with peripheral artery disease (PAD) who experience IC. Inclusion criteria for questionnaires were based on existence of a body of literature in symptomatic PAD.

RESULTS

Six general questionnaires and seven disease-specific questionnaires are included, with details about the number of domains covered and how each tool is scored. The Medical Outcomes Study Short Form 36-item questionnaire and Walking Impairment Questionnaire are currently the most used general and disease-specific questionnaires at baseline and after treatment for IC, respectively.

CONCLUSIONS

The use of tools that assess functional status and HRQOL has importance in both the clinical and research areas to assess treatment efficacy from the patient's perspective. Therefore, assessing HRQOL in addition to treadmill-measured walking ability provides insight as to the effects of treatments on patient outcomes and may help guide therapy.

Peripheral artery disease: current insight into the disease and its diagnosis and management

Peripheral artery disease (PAD), which comprises atherosclerosis of the abdominal aorta, iliac, and lower-extremity arteries, is underdiagnosed, undertreated, and poorly understood by the medical community. Patients with PAD may experience a multitude of problems, such as claudication, ischemic rest pain, ischemic ulcerations, repeated hospitalizations, revascularizations, and limb loss. This may lead to a poor quality of life and a high rate of depression. From the standpoint of the limb, the prognosis of patients with PAD is favorable in that the claudication remains stable in 70% to 80% of patients over a 10-year period. However, the rate of myocardial infarction, stroke, and cardiovascular death in patients with both symptomatic and asymptomatic PAD is markedly increased. The ankle brachial index is an excellent screening test for the presence of PAD. Imaging studies (duplex ultrasonography, computed tomographic angiography, magnetic resonance angiography, catheter-based angiography) may provide additional anatomic information if revascularization is planned. The goals of therapy are to improve symptoms and thus quality of life and to decrease the cardiovascular event rate (myocardial infarction, stroke, cardiovascular death). The former is accomplished by establishing a supervised exercise program and administering cilostazol or performing a revascularization procedure if medical therapy is ineffective. A comprehensive program of cardiovascular risk modification (discontinuation of tobacco use and control of lipids, blood pressure, and diabetes) will help to prevent the latter.

Drug therapy for improving walking distance in intermittent claudication: a systematic review and meta-analysis of robust randomised controlled studies

OBJECTIVES

To evaluate the efficacy of pharmacological interventions in improving walking capacity and health-related quality of life for people with intermittent claudication. DATASOURCES: We searched Medline, EMBASE, Cochrane library and relevant websites for studies published from the start of the databases to February 2009. In addition, reference lists were manually searched.

REVIEW METHODS

Based upon a power calculation, only robust (n>56), peer-reviewed, double-blinded, randomised and placebo-controlled trials were included. The main outcomes evaluated were maximal walking distance (MWD) and pain-free walking distance on a treadmill. Random models were used in the statistical analysis, and chi-square test were used to test for heterogeneity.

RESULTS

Among 220 trials, only 43 trials fulfilled the quality criteria. Treatment periods, follow-up and treadmill protocols varied substantially. Vasodilator agents and phosphodiesterase inhibitors show robust significant results compared to placebo, but the improvements in MWD are modest. The highest benefit was caused by lipid-lowering agents, which in mean gained above 160 m in MWD, while the other agents only improved MWD about 50 m.

CONCLUSION

Several drugs have shown to improve MWD, but with limited benefits. Statins seem to be the most efficient drug at the moment.

Review of mortality and cardiovascular event rates in patients enrolled in clinical trials for claudication therapies

Pharmacological and non-pharmacological interventions to improve function and quality of life in patients with claudication are being evaluated in clinical research trials. An important component of clinical development programs is assessing the safety of the intervention and monitoring for adverse impact of the therapy on research participants. The conduct of both of these safety assessments is facilitated by the ability to estimate the anticipated rates of cardiovascular events and death in the target population. To obtain estimates of these rates, data were abstracted from randomized, double-blind, placebo-controlled trials performed in patients with claudication and designed to show functional improvement, and which have been published since 1990. Patient-year exposures and the number of deaths, serious adverse events and cardiovascular serious adverse events in the placebo arms of these trials were tabulated, and summed event rates calculated. The mortality rate was 1.9 deaths per hundred patient-years (27 deaths observed in 1446 patient-years). The mortality rate in claudication trials is lower than that reported in natural history studies. Cardiovascular serious adverse events in claudication trials were observed at a rate of 8.5 per hundred patient-years (65 events in 762 patient-years). Thus, cardiovascular morbidity and mortality should be expected in clinical trials enrolling claudicants. The current analyses provide benchmark data for ensuring that development programs are large enough to allow meaningful safety conclusions, and to assist in data and safety monitoring of these trials.