Randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of AS-013, a prostaglandin E1 prodrug, in patients with intermittent claudication

Surrogate and clinical endpoints for studies in peripheral artery occlusive disease: Are statistics the brakes?

BACKGROUND

The aim of this review is to present the available clinical and surrogate endpoints that may be used in future studies performed in patients with peripheral artery occlusive disease (PAOD). Importantly, we describe statistical limitations of the most commonly used endpoints and offer some guidance with respect to study design for a given sample size. The proposed endpoints may be used in studies using surgical or interventional revascularization and/or drug treatments.

METHODS

Considering recently published study endpoints and designs, the usefulness of these endpoints for reimbursement is evaluated. Based on these potential study endpoints and patient sample size estimates with different non-inferiority or tests for difference hypotheses, a rating relative to their corresponding reimbursement values is attempted.

RESULTS

As regards the benefit for the patients and for the payers, walking distance and the ankle brachial index (ABI) are the most feasible endpoints in a relatively small study samples given that other non-vascular impact factors can be controlled. Angiographic endpoints such as minimal lumen diameter (MLD) do not seem useful from a reimbursement standpoint despite their intuitiveness. Other surrogate endpoints, such as transcutaneous oxygen tension measurements, have yet to be established as useful endpoints in reasonably sized studies with patients with critical limb ischemia (CLI).

CONCLUSIONS

From a reimbursement standpoint, WD and ABI are effective endpoints for a moderate study sample size given that non-vascular confounding factors can be controlled.

PGE1 and Other Prostaglandins in the Treatment of Intermittent Claudication: A Meta-analysis

In intermittent claudication, pharmacologic drugs and invasive measures are indicated in patients who do not benefit from exercise training. To evaluate the therapeutic role of prostaglandins (PGs), especially of prostaglandin E1 (PGE1), for this indication, the author performed a meta-analysis of all published prospective, randomized, controlled clinical studies in which descriptive sample statistics of the pain-free walking distance (PFWD) and the maximum walking distance (MWD) were available. In total, 9 studies with PGE1 and 4 studies with other PGs (beraprost, iloprost, AS-013) that met these selection criteria could be analyzed. In patients treated with PGE1 (n=344), PFWD increased significantly (p<0.001) more (+107%) than in patients treated with other PGs (n=402; +42%) or placebo (n=470; +24%). Similar results were also found for the MWD. Side effects were significantly (p<0.001) fewer with PGE1 therapy than with other PGs (14.0% vs 30.8% of patients). In conclusion, PGE1 proved to be the most effective and best tolerated of the PGs evaluated.

Medical Management of Intermittent Claudication

The symptoms of intermittent claudication (IC) lead sufferers to seek medical attention, potentially leading to substantial workup and invasive testing. However, only a minority of people with IC develop limb-threatening ischemia or symptoms of significant lifestyle-limiting claudication. Patients with IC have a substantial risk of concomitant cardiovascular and cerebrovascular disease. Assessment of co-morbidities and control of risk factors reduce the cardiovascular risk of these patients. A multitude of drugs have been developed and tested in numerous trials for the symptoms of IC. Although no drug alone offers a “cure” to IC, some are used as adjuvant therapy to reduce claudication symptoms.

Current therapies and investigational drugs for peripheral arterial disease

Peripheral artery disease (PAD) is associated with elevated morbidity and mortality with cardiovascular (CV) disease. The guideline recommends smoking cessation and antiplatelet/antithrombotic drugs for asymptomatic and symptomatic PAD patients. It also recommends that PAD patients with critical limb ischemia (CLI) should be considered to receive endovascular and open surgical treatment for limb salvage. Although PAD patients with CLI receive these treatments, they are sometimes unable to deliver sufficient blood flow to eliminate their symptoms. Thus specific strategies are needed to promote enough blood flow. To establish the effective method, many investigations have been performed using cell-based therapy. Endothelial progenitor cells, mononuclear cells and mesenchymal stem cells have been well investigated in clinical settings. To induce angiogenesis, vascular endothelial growth factor, fibroblast growth factor and hepatocyte growth factor (HGF) have also been transfected in PAD patients. Among them, HGF is the most promising factor because it can induce angiogenesis without the induction of vascular inflammation and increased permeability. In this review article, we summarize current treatments and investigational drugs of PAD.

Comparison of beraprost and ticlopidine in Chinese patients with chronic peripheral arterial occlusion: a multicenter, single-blind, randomized, controlled study

BACKGROUND

Chronic peripheral arterial occlusion (CPAO) is a progressive disease that is associated with a variety of symptoms, the 4 most common being a sensation of coolness in the limbs, intermittent claudication (in which pain occurs on walking), limb pain (which occurs spontaneously at rest), and ischemic leg ulcers. Beraprost sodium is an oral prostaglandin I2 analogue that may ameliorate these symptoms.

OBJECTIVE

The aim of this study was to compare the efficacy and tolerability of beraprost sodium and ticlopidine hydrochloride in the treatment of patients with CPAO in China.

METHODS

In this multicenter, single-blind, controlled study, patients with CPAO were randomly assigned to receive beraprost 120-μg tablet TID or ticlopidine 500-mg tablet BID, both administered orally. The clinical efficacy of the drugs was assessed using the 4 main symptoms of CPAO. Ankle-brachial index (ABI) also was measured as a clinical pharmacologic procedure. Adverse events were assessed throughout the study.

RESULTS

A total of 124 patients (96 men, 28 women; mean [SD] age, 65 [12] years) were enrolled in 3 hospitals. Data from 119 patients (93 men, 26 women; mean [SD] age, 65 [12] years) were included in the efficacy analysis (64 and 55 patients in the beraprost and ticlopidine groups, respectively). Although all 4 symptoms of CPAO were ameliorated after 3 and 6 weeks of treatment with both drugs, only the cool sensation was significantly improved with beraprost compared with ticlopidine at 6 weeks (P<0.05). ABI was significantly increased with both beraprost and ticlopidine at 6 weeks versus baseline (P<0.001 and P<0.01, respectively), suggesting that this pharmacologic action may have led to their beneficial effect on various symptoms. The tolerability analysis included 123 patients (65 and 58 patients in the beraprost and ticlopidine groups, respectively). The numbers of patients who (1) experienced adverse events (AEs), (2) experienced adverse drug reactions, and (3) withdrew due to AEs were significantly smaller in the beraprost group than in the ticlopidine group (P<0.001, P<0.05, and P<0.05, respectively).

CONCLUSIONS

In this study population of patients with CPAO, beraprost ameliorated cool sensation in the limbs, intermittent claudication, limb pain, and ischemic/leg ulcers. Beraprost was more efficacious in relieving CPAO symptoms and was better tolerated than ticlopidine. Beraprost may be useful for the treatment of patients with CPAO, but more studies are needed.

Effects of Beraprost sodium on subjective symptoms in diabetic patients with peripheral arterial disease

Background

This study evaluated the effects of Beraprost sodium (Berasil) on subjective leg symptoms in patients with peripheral arterial disease caused by diabetes mellitus.

Methods

Ninety-four diabetic patients with peripheral arterial disease were treated with Beraprost in a fixed-dose, prospective, multicenter, cohort study. Beraprost (40 µg) was administered orally 3 times daily (120 µg/day) for 12 weeks. We developed a new disease-specific symptom questionnaire, which evaluated the effect of peripheral arterial disease on leg discomfort in daily life and assessed therapeutic responses to treatment. Patients were asked for their subjective assessment of symptoms on a written questionnaire before treatment and after 12 weeks of therapy.

Results

There was significant improvement in all estimated subjective symptoms (burning, coldness, edema, exertional pain, stabbing, and paresthesias) in the lower extremities at 12 weeks (p < 0.001). There were 18 patients with neuropathy in whom significant improvement was noted for 6 subjective symptoms at 12 weeks (p < 0.05). Adverse events considered to be drug-related were observed in 4 patients (4.3%), all of which were mild and resolved with discontinuation of the medication.

Conclusions

Beraprost is effective as a treatment for improving various subjective symptoms in the lower extremities, such as burning, coldness, edema, exertional pain, stabbing, and paresthesias, in diabetic patients with peripheral arterial disease.

Prostanoids for intermittent claudication

BACKGROUND

Peripheral arterial disease (PAD) is a common cause of morbidity in the general population. While numerous studies have established the efficacy of prostanoids in PAD stages III and IV, the question of the role of prostanoids as an alternative or additive treatment in patients suffering from intermittent claudication (PAD II) has not yet been clearly answered. This is an update of a Cochrane Review first published in 2004.

OBJECTIVES

To determine the effects of prostanoids in patients with intermittent claudication (IC) Fontaine stage II.

SEARCH METHODS

For this update, the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched January 2013) and CENTRAL (2012, Issue 12). Clinical trials databases were searched for details of ongoing or unpublished studies. In addition, reference lists of relevant articles were checked.

SELECTION CRITERIA

Randomised clinical trials of prostanoids versus placebo or alternative ('control') treatment in people with intermittent claudication were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Primary outcomes included pain-free walking distance (PFWD) and maximum walking distance (MWD), presented as mean change in walking distance during the course of the trial (% improvement) and as final walking distance (that is walking distance, in metres, after treatment) for the prostanoid and control groups.

MAIN RESULTS

Eighteen trials with a total of 2773 patients were included (16 in the original review and a further two in this update). As the majority of trials did not report standard deviations for the primary PFWD and MWD outcomes, it was often not possible to test for the statistical significance of any improvements in walking distance between groups. The quality of individual trials was variable and usually unclear due to insufficient reporting information. Comparison between trials was hampered by the use of different treadmill testing protocols, including different walking speeds and gradients. Such limitations in the data and the trial heterogeneity meant it was not possible to meaningfully pool results by meta-analysis.Four trials compared prostaglandin E1 (PGE1) with placebo; individual trials showed significant increases in walking distances with administration of PGE1 and in several trials the walking capacity remained increased after termination of treatment. Compared with pentoxifylline, PGE1 was associated with a higher final PFWD and MWD but these results were based on final walking distances rather than changes in walking distance from baseline. When PGE1 was compared with other treatments including laevadosin, naftidrofuryl and L-arginine, improvements in walking distances over time were observed for both PGE1 and the alternative treatment, but it was not possible from the data available to analyse statistically whether or not one treatment was more effective than the other.Six studies compared various preparations of prostacyclins (PGI2) with placebo. In one study using three different dosages of iloprost, PFWD and MWD appeared to increase in a dose-dependent manner; iloprost was associated with headache, pain, nausea and diarrhoea, leading to a higher rate of treatment withdrawal. Of three studies using beraprost sodium, one showed an improvement in PFWD and MWD compared with placebo while two showed no significant benefit. Beraprost sodium was associated with an increased incidence of drug-related adverse events. Of two studies on taprostene, the results of one in particular must be interpreted with caution due to an imbalance in walking capacity at baseline.Comprehensive, high quality data on outcomes such as quality of life, ankle brachial index, venous occlusion plethysmography and haemorrheological parameters were lacking.

AUTHORS' CONCLUSIONS

Whilst results from some individual studies suggested a beneficial effect of PGE1, the quality of these studies and of the overall evidence available is insufficient to determine whether or not patients with intermittent claudication derive clinically meaningful benefit from the administration of prostanoids. Further well-conducted randomised, double blinded trials with a sufficient number of participants to provide statistical power are required to answer this question.

Treatment strategies for peripheral artery disease

Peripheral arterial disease is an underecognized manifestation of systemic atherosclerosis associated with high rates of cardiovascular morbidity and mortality. The rationale of therapy is to reduce cardiovascular risk, improve symptoms of intermittent claudication, and prevent the development of critical limb ischemia and amputation. Exercise therapy and several pharmacologic agents have been shown to improve walking distance in patients with intermittent claudication. Patients with lifestyle-interfering symptoms despite exercise, or those who progress to critical limb ischemia, frequently undergo revascularization. Endovascular techniques are commonly used in these patients. Combined pharmacological and endovascular strategies will play an increasing role in management of these patients in the future.

Accelerated blood clearance phenomenon upon repeated injection of PEG-modified PLA-nanoparticles

PURPOSE

We recently developed prostaglandin E(1) (PGE(1))-encapsulated nanoparticles, prepared with a poly(lactide) homopolymer (PLA, Mw = 17,500) and monomethoxy poly(ethyleneglycol)-PLA block copolymer (PEG-PLA) (NP-L20). In this study, we tested whether the accelerated blood clearance (ABC) phenomenon is observed with NP-L20 and other PEG-modified PLA-nanoparticles in rats.

METHODS

The plasma levels of PGE(1) and anti-PEG IgM antibody were determined by EIA and ELISA, respectively.

RESULTS

Second injections of NP-L20 were cleared much more rapidly from the circulation than first injections, showing that the ABC phenomenon was induced. This ABC phenomenon, and the accompanying induction of anti-PEG IgM antibody production, was optimal at a time interval of 7 days between the first and second injections. Compared to NP-L20, NP-L33s that were prepared with PLA (Mw = 28,100) and have a smaller particle size induced production of anti-PEG IgM antibody to a lesser extent. NP-L20 but not NP-L33s gave rise to the ABC phenomenon with a time interval of 14 days. NP-L33s showed a better sustained-release profile of PGE(1) than NP-L20.

CONCLUSIONS

This study revealed that the ABC phenomenon is induced by PEG-modified PLA-nanoparticles. We consider that NP-L33s may be useful clinically for the sustained-release and targeted delivery of PGE(1).

Pharmacologic therapy for intermittent claudication

Peripheral artery disease, defined as atherosclerosis in the lower extremities, affects nearly 8.5 million people in the United States. Due to the frequent asymptomatic manifestation of peripheral artery disease, diagnosis may be delayed and its true incidence underestimated. However, some patients may experience aching pain, numbness, weakness, or fatigue, a condition termed intermittent claudication. Peripheral atherosclerosis is associated with cardiovascular risk and physical impairment; therefore, treatment goals are aimed at decreasing cardiovascular risk, as well as improving quality of life. Little debate exists regarding the management of cardiovascular risk reduction, which consists of both antiplatelet therapy and risk factor modification. Despite recently published guidelines, the treatment of intermittent claudication is less well established and the management remains controversial and uncertain. Exercise remains the first-line therapy for intermittent claudication; however, pharmacologic treatment is often necessary. Although only two prescription drugs have been approved by the U.S. Food and Drug Administration for the treatment of intermittent claudication, several supplements and investigational agents have been evaluated. Therapeutic optimization should balance the anticipated improvements in quality of life with the potential safety risks.

A randomized trial of iloprost in patients with intermittent claudication

Abstract

Prostanoids, which promote vasodilation and reduce platelet aggregation, have been proposed as candidate therapies for intermittent claudication due to peripheral arterial disease (PAD). However, studies of these medications have yielded inconsistent results. This study tested the hypothesis that iloprost, an oral prostacyclin analogue, would improve walking distance and quality of life in patients with intermittent claudication. The study was a multi-center, randomized, double-blind, placebo-controlled trial comparing three doses of oral iloprost (50 μg, 100 μg, or 150 μg twice daily), pentoxifylline, or placebo in 430 patients with intermittent claudication. The primary outcome measure was improvement in absolute claudication distance (ACD) after 6 months. Secondary outcomes included initial claudication distance and quality of life assessment. Placebo increased ACD by 3.3%, and iloprost increased peak ACD by 7.7%, 8.8% and 11.2% at the 50 μg, 100 μg, and 150 μg twice-daily doses, respectively (all insignificant relative to placebo). Pentoxifylline increased ACD by 13.9% relative to placebo ( p = 0.039). Neither iloprost nor pentoxifylline enhanced quality of life. These results indicate that oral iloprost is not effective in improving exercise performance or quality of life in patients with PAD who have intermittent claudication.

Pharmacological interventions for peripheral artery disease

Peripheral arterial disease (PAD) encompasses the vascular diseases caused primarily by atherosclerosis and thromboembolic pathophysiological processes that alter the normal structure and function of the aorta, its visceral arterial branches and the arteries of the upper and lower extremities. PAD is associated with an increased risk for cardiovascular morbidity and mortality. The goals for pharmacological therapy in PAD should focus on reducing cardiovascular risk, improving walking distance and preventing critical limb ischaemia. Exercise training plays a key role in the therapeutic assessment, as well stopping smoking. Antiplatelet therapy (aspirin) should be given to every PAD patient if there are no contraindications. Neither their combination nor anticoagulant therapy has shown additional benefit in PAD patients. Several pharmacological agents have been developed to improve the functional state of the claudicant and to relieve the symptoms. Many studied drugs have shown either no, a small or a potential benefit. With future development of new drugs for PAD, there is an absolute need for very strict well-designed protocols in order to evaluate the claudication distance, the progression of the disease and the reduction in cardiovascular morbidity and mortality. New developments should focus on improvement of endothelial function, vascular repair and enhancement of collateral circulation.

Parenteral therapy with lipo-ecraprost, a lipid-based formulation of a PGE1 analog, does not alter six-month outcomes in patients with critical leg ischemia

PURPOSE

Eicosanoids with vasodilating and angiogenic properties have been postulated to be effective therapies for critical leg ischemia (CLI) secondary to atherosclerotic peripheral arterial disease. The ability to deliver active drug to the site of action at adequate doses for sufficient duration has been a major limitation in the clinical development of such therapies. Lipo-ecraprost is a lipid-encapsulated prostaglandin E1 prodrug with the potential to deliver active prostaglandin to the site of critical arterial ischemia. The current trial was designed to test the hypothesis that lipo-ecraprost would improve amputation-free survival in patients with CLI who had no revascularization options.

METHODS

The study was randomized, multicenter, double blind, and placebo controlled. Patients who met clinical and hemodynamic criteria were randomized to receive placebo or lipo-ecraprost (60 microg) administered intravenously on each of 5 days per week, for a total of 8 weeks. The study's primary endpoint was the rate of a composite end point of death or amputation above the level of the ankle at 180 days (6 months).

RESULTS

The study was terminated on a recommendation from the Data and Safety Monitoring Board after the completion of a protocol-specified interim analysis for futility. At the time of termination, 383 of the planned 560 patients had been randomized, of which 379 received at least one dose of study medication and thus were included in the intention-to-treat population. Twenty-three patients were lost to follow-up and were not available for 6-month assessments. At 6 months of follow-up, there were 23 amputations in the 177 patients who received placebo, and 29 amputations in the 179 patients randomized to lipo-ecraprost. At 6 months, 10 deaths had occurred in the placebo group and 18 deaths had occurred in the lipo-ecraprost arm. Changes in lower-extremity hemodynamics over the 6-month study period did not differ between the placebo and lipo-ecraprost treatment arms.

CONCLUSION

Intensive treatment with lipo-ecraprost failed to modify the 6-month amputation rate in patients with CLI who were not candidates for revascularization.

Antithrombotic Therapy in Peripheral Arterial Occlusive Disease

This chapter about antithrombotic therapy for peripheral arterial occlusive disease is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004;126:179S-187S). Among the key recommendations in this chapter are the following: For patients with chronic limb ischemia, we recommend lifelong aspirin therapy in comparison to no antiplatelet therapy in patients with clinically manifest coronary or cerebrovascular disease (Grade 1A) and in those without clinically manifest coronary or cerebrovascular disease (Grade 1C+). We recommend clopidogrel over no antiplatelet therapy (Grade 1C+) but suggest that aspirin be used instead of clopidogrel (Grade 2A). For patients with disabling intermittent claudication who do not respond to conservative measures and who are not candidates for surgical or catheter-based intervention, we suggest cilostazol (Grade 2A). We suggest that clinicians not use cilostazol in patients with less-disabling claudication (Grade 2A). In these patients, we recommend against the use of pentoxifylline (Grade 1B). We suggest clinicians not use prostaglandins (Grade 2B). In patients with intermittent claudication, we recommend against the use of anticoagulants (Grade 1A). In patients with acute arterial emboli or thrombosis, we recommend treatment with immediate systemic anticoagulation with unfractionated heparin (UFH) [Grade 1C]. We also recommend systemic anticoagulation with UFH followed by long-term vitamin K antagonist (VKA) in patients with embolism [Grade 1C]). For patients undergoing major vascular reconstructive procedures, we recommend UFH at the time of application of vascular cross-clamps (Grade 1A). In patients undergoing prosthetic infrainguinal bypass, we recommend aspirin (Grade 1A). In patients undergoing infrainguinal femoropopliteal or distal vein bypass, we suggest that clinicians do not routinely use a VKA (Grade 2A). For routine patients undergoing infrainguinal bypass without special risk factors for occlusion, we recommend against VKA plus aspirin (Grade 1A). For those at high risk of bypass occlusion and limb loss, we suggest VKA plus aspirin (Grade 2B). In patients undergoing carotid endarterectomy, we recommend aspirin preoperatively and continued indefinitely (Grade 1A). In nonoperative patients with asymptomatic or recurrent carotid stenosis, we recommend lifelong aspirin (Grade 1C+). For all patients undergoing extremity balloon angioplasty, we recommend long-term aspirin (Grade 1C+).

Ecraprost

Ecraprost [AS 013, Circulase] is a prodrug of prostaglandin E(1) within lipid microspheres that is being developed in Japan by Mitsubishi Pharma Corporation and Asahi Glass. It was originally in development with Welfide Corporation. On 1 October 2001, Welfide Corporation (formerly Yoshitomi) merged with Mitsubishi-Tokyo Pharmaceuticals to form Mitsubishi Pharma Corporation. The new company is a subsidiary of Mitsubishi Chemical. Taisho and Seikagaku Corporation had been involved in the development of ecraprost but discontinued their licences to do so. The effects of ecraprost on reperfusion injury, in preclinical studies, had been reported by Taisho. Ecraprost is in phase II in Japan and was in phase II in Europe for the treatment of peripheral arterial disease. It was also in a phase II study in the treatment of diabetic neuropathies. However, this is no longer an active indication. A phase III trial using a lipid emulsion of ecraprost [Circulase] is underway with Mitsubishi Pharma Corporation in the US, using ecraprost for the treatment of patients with severe peripheral arterial disease, which, because of decreased blood flow to the extremities, can lead to painful ulcers on the legs and feet and subsequent amputation. Alpha Therapeutic Corporation (a former subsidiary of Mitsubishi Pharma) was initially involved in trials of ecraprost in the US, but this responsibility has been taken over by the parent company.

Prostanoids for intermittent claudication

BACKGROUND

Peripheral arterial occlusive disease (PAOD) is a common cause of morbidity in the general population. While numerous studies have established the efficacy of prostanoids in PAOD stages III and IV the question of the role of prostanoids as an alternative or additive treatment in patients suffering from claudicatio intermittens (PAOD II) has not yet been clearly answered.

OBJECTIVES

The aim of this review was to evaluate effects of prostanoids in patients with intermittent claudication.

SEARCH STRATEGY

Computerised searches of the Cochrane Peripheral Vascular Diseases Specialised Register (last searched April 2003), The Cochrane Central Register of Controlled Trials (CENTRAL) (last searched Issue 1, 2003), MEDLINE and EMBASE were undertaken. In addition relevant journals were hand-searched.

SELECTION CRITERIA

Randomized clinical trials describing the effects of prostanoids in the treatment of patients suffering from intermittent claudication have been considered for inclusion.

DATA COLLECTION AND ANALYSIS

All reviewers assessed the quality of studies and extracted data unblinded. Statistical analysis including tests for heterogeneity and overall effect were performed by using MetaView of Review Manager 4.2. All numeric values are expressed as mean +/- Standard deviation (SD).

MAIN RESULTS

Eighteen studies were included for analysis. A significant heterogeneity between the included studies was detected in most of the subgroup analysis. Five studies compared the effects of prostaglandin E1 (PGE1) versus placebo, and reported in their individual results significant increases in walking distances after the administration of PGE1. The attained increase in walking distances appears to be not merely a short-term effect because several studies reported that walking capacity remained increased even after termination of treatment. On the other hand, oral or intravenous prostacyclin did not increase the walking distances significantly. At least one adverse reaction was reported from 23.6% of the patients treated with prostacyclin (PGI2), and its analogues and from 13.7% of the patients treated with PGE1.

REVIEWER'S CONCLUSIONS

Because of the heterogeneity between most of the included studies, we did not pool relevant parts of the data by meta-analysis. Based on the individual results of the published literature, patients with intermittent claudication seem to benefit from administration (intravenous or intra-arterial) of PGE1 by a significant improvement of their walking capacity. Further well-conducted randomized, double blinded trials, with a sufficient number of patients to provide statistical powerful information, should be performed to confirm the results of this review.

Pharmacologic treatment for intermittent claudication

In contradistinction to chronic critical limb ischemia, the peripheral arterial disease patient with intermittent claudication is at relatively low risk for limb loss. As a result, initial claudication management should employ non-interventional therapies rather than immediate catheter-based or surgical revascularization. Although exercise therapy is the most efficacious conservative treatment for claudication, supervised exercise programs are not widely available at present. Consequently, a pharmacologic agent can be utilized to lessen the symptoms and improve the function of the claudicant. This manuscript provides a comprehensive review of the various pharmacotherapies that have been investigated for improving walking distance in the setting of intermittent claudication. Cilostazol, a phosphodiesterase III inhibitor, appears to provide the greatest benefit, significantly improving not only walking distance but quality of life as well. Early trials indicate that propionyl-L-carnitine, oral prostaglandins, L-arginine, and therapeutic angiogenesis may eventually yield significant benefit in lessening the symptoms of intermittent claudication.

Developing pharmaceutical treatments for peripheral artery disease

Peripheral artery disease (PAD) is a debilitating atherosclerotic disease of the lower limbs and is associated with an increased risk of cardiovascular morbidity and mortality. Treatment goals should be aimed at providing symptom relief (claudication) and reducing the risk of systemic cardiovascular morbidity and mortality. In the development of pharmaceutical treatment for PAD, aggressive non-pharmacological intervention and pharmacological treatment of the risk factors associated with PAD should be given. Antiplatelet therapy, aspirin, should be given to every PAD patient if there are no contraindications. Should symptoms worsen or intolerance to aspirin develop, ticlopidine or clopidogrel would be the alternative. Several pharmacological agents have been developed to improve the functional state of the claudicant and to relieve the symptoms. Many studied drugs have shown either no, small or potential benefit. With future development of new drugs for PAD, there is an absolute need for very strict, well-designed protocols in order to evaluate the claudication distance and progression of the disease, as well as the reduction in cardiovascular morbidity and mortality.

Management of intermittent claudication

Medical management of PAD is a considerable challenge. Although patients typically present with IC, there is a substantial pool of subclinical PAD patients. PAD, whether symptomatic or not, confers a marked cardiovascular risk; with affected patients dying of heart attack or stroke, identification of index patients and aggressive medical treatment can offer health benefits far in excess of improvement in IC or related symptoms. Management of risk factors, lifestyle interventions, and pharmacologic treatment with agents to provide symptomatic relief have a central role in improving function and quality of life and slowing the progression to advanced endpoints, such as the rest pain, nonhealing ulcers, gangrene, and cardiac death. Surgical or percutaneous revascularization for aorto-iliac disease provides durable treatment for individuals with disabling symptoms. Newer treatments, such as angiogenic growth factor treatments, are being tested in clinical trials and seem promising. There are limited treatment choices for individuals with predominant infra-popliteal disease. In the future, the availability of newer stents and therapies to prevent re-stenosis may extend the applicability of endovascular treatment to difficult-to-treat infra-inguinal lesions.

Intravenous prostaglandin E1 reduces soluble vascular cell adhesion molecule-1 in peripheral arterial obstructive disease

OBJECTIVES

Elevated levels of soluble (s) vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1, pointing to activation of cells involved in vascular inflammation, have been previously reported in peripheral arterial obstructive disease (PAOD). We tested the hypothesis that intravenous prostaglandin E(1) (PGE(1)) treatment, which produces clinical benefits in this condition, might decrease such levels.

METHODS

Ten subjects (age range 58 +/- 10 years, 6 male, 4 female) with characterized Fontaine stage IIa to IV PAOD (ankle/arm pressure index <0.96) were entered into a treatment protocol with twice daily intravenous infusions of PGE(1) (alprostadil) at 120 microg per day, repeated for 10 consecutive days. Preinfusion and postinfusion plasma samples were stored for blind enzyme immunoassays of soluble adhesion molecules and the fibrinolytic marker tissue plasminogen activator, type-1 plasminogen-activator inhibitor, and D -dimer.

RESULTS

Estimates of severity of pain at rest, consumption of analgesics, magnitude of trophic lesions, remission to lower Fontaine stages, and favorable changes in the venoarteriolar reflex documented significant beneficial effects of the treatment. Significant (P <.01) pretreatment and posttreatment reductions of in all soluble markers explored were found. Particularly, sVCAM-1 exhibited a significant decrease after each infusion, which was sustained at the last day of treatment (from 854 +/- 214 ng/mL to 775 +/- 215 ng/mL across the first infusion, from 773 +/- 146 ng/mL to 680 +/- 110 ng/mL across the last infusion).

CONCLUSION

Thus a global decrease of vascular cell activation appears to occur as a result of PGE(1) administration and may contribute to the observed clinical benefits in PAOD.

Medical management of peripheral arterial disease

Peripheral arterial disease affects approximately 8-10 million people in the United States. Approximately one-third to one-half of these individuals are symptomatic. The risk factors that contribute to peripheral arterial disease are similar to those associated with other forms of atherosclerosis, including diabetes mellitus, cigarette smoking, hypercholesterolemia, high blood pressure, and hyperhomocysteinemia. Of these, diabetes and cigarette smoking pose the greatest risk for developing peripheral arterial disease. The prognosis of patients with these risk factors is limited because of their greater risks for myocardial infarction, stroke, and cardiovascular death. Cardiovascular mortality correlates inversely with the ankle/brachial index, and the risk of death is greatest in those with the most severe peripheral arterial disease. Treatment regimens to reduce cardiovascular morbidity and mortality in patients with peripheral arterial disease should include risk factor modification and antiplatelet therapy. The cardinal symptoms of peripheral arterial disease include intermittent claudication and rest pain, with the latter being indicative of critical limb ischemia. Therapeutic strategies that focus on improving the patient's quality of life, reducing the severity of claudication, and improving limb viability include supervised exercise training, pharmacotherapy, and revascularization. Two drugs-pentoxifylline and cilostazol-currently are approved by the Food and Drug Administration for the treatment of patients with claudication. Meta-analyses have suggested that, compared with placebo, pentoxifylline improves maximal walking distance by approximately 20-25%. Cilostazol is a phosphodiesterase type 3 inhibitor. In clinical trials, cilostazol has consistently improved maximal walking distance as compared with placebo, with the range of improvement being approximately 40-60%. Drugs that are currently under investigation include propionyl-L-carnitine, vasodilator prostaglandins, L-arginine, and the angiogenic factors, vascular endothelial growth factor and basic fibroblast growth factors.

Marked hypotensive and blood flow-increasing effects of a new lipo-PGE(1) (lipo-AS013) due to vascular wall targeting

Lipo-AS013 is being developed as an improved formulation of lipo-PGE(1), which is widely used in clinical practice in Japan and some Asian countries. We have previously reported that lipo-AS013, which is a lipid microsphere (LM) preparation of a chemically stable and lipophilic PGE(1) prodrug (AS013, Fig. 1), slowly releases small amounts of the active ingredient (AS013) in human plasma. In the present study, to estimate the vascular wall targeting ability and efficacy of lipo-AS013, we determined the hypotensive and blood flow-increasing effects of lipo-AS013, lipo-PGE(1), PGE(1)CD, and AS013. Lipo-AS013 was found to have longer-lasting hypotensive and blood flow-increasing effects than the other agents. The two LM preparations, lipo-PGE(1) and lipo-AS013, had a markedly stronger effect than PGE(1)CD and AS013 alone, demonstrating the benefit of drug delivery using LM. In spontaneously hypertensive rats (SHR), lipo-AS013 also had a significant hypotensive effect. To confirm vascular wall targeting by lipo-AS013, the localization of PGE(1) in the aorta and neovascular capillaries of rat was investigated by immunostaining. The results indicated that lipo-AS013 was more efficient at delivering the active ingredient (AS013) to the vessel wall. In conclusion, lipo-AS013 could supersede lipo-PGE(1) and PGE(1)CD in clinical use.

Interleukin-8 (IL-8) may contribute to the activation of neutrophils in patients with peripheral arterial occlusive disease (PAOD)

OBJECTIVES

to investigate the levels of interleukin-8 (IL-8) in patients with peripheral arterial occlusive disease (PAOD) and healthy control subjects both before and after an acute exercise test.

MATERIALS AND METHODS

twenty-six patients with intermittent claudication and 22 matched healthy control subjects each had IL-8 levels measured before and after a standard acute treadmill-exercise test. Subjects walked for 10 min or until stopped by claudication pain. Serum IL-8 levels were measured before exercise was commenced and 1, 5 and 10 min after exercise was stopped.

RESULTS

patients with PAOD had statistically significantly higher levels of IL-8 than healthy control subjects, before and after an acute exercise test (p <0.00001, Mann-Whitney). Ratios of the change of IL-8 levels post-exercise showed a statistically significant difference at the post-5-min time point (p =0.005), showing a difference in the change of IL-8 levels at this time point between the patient group and control group.

CONCLUSIONS

The increased levels and the failure of the cytokine levels to fall by the same extent after exercise in the patient group may be due to a combination of increased neutrophil activation, reduced blood flow and increased cytokine production during ischaemia-reperfusion, which is not observed in the healthy controls.

Abnormal markers of endothelial cell activation and oxidative stress in children, adolescents and young adults with type 1 diabetes with no clinical vascular disease

BACKGROUND

Endothelial cell dysfunction is an early feature of vascular disease and oxidative stress may be involved in its pathogenesis.

METHODS

Fifty-one children, adolescents and young people with Type 1 diabetes with no clinical diabetic angiopathy, mean age+/-SD of 16+/-4 years, diabetes duration of 8+/-5 years, and HbA(1c) of 8.5+/-1.6%, and 29 age, sex matched normal controls had blood samples assayed for E-selectin, intercellular cell adhesion molecule-1, von Willebrand Factor, red cell superoxide dismutase, plasma thiol and red cell glutathione.

RESULTS

E-selectin and ICAM-1 levels were significantly higher in the diabetic patients at 72+/-24 ng/ml and 287+/-57 ng/ml, respectively vs 43+/-16 ng/ml and 248+/-71 ng/ml in the normal controls (p<0.0002 and p<0.013). Von Willebrand Factor levels were not different between the two groups. Superoxide dismutase activity was significantly higher in the diabetic group at 220+/-58 micro/ml vs 175+/-24 micro/ml in the normal controls p<0.001, and those of plasma thiol and red cell glutathione were significantly lower in the diabetic group, at 1267+/-202 micromol/l and 458+/-38 micromol/l, respectively vs 1403+/-278 micromol/l and 487+/-70 micromol/l in the controls p<0.02 and p<0.03. Levels of superoxide dismutase correlated negatively with plasma thiol, age and diabetes duration r=-0.318, p<0.02; r=-0. 328, p<0.02; and r=-0.286, p<0.05, respectively.

CONCLUSION

These results confirm evidence of endothelial perturbation in young people with diabetes mellitus, and they also suggest that free radical generation may contribute to this dysfunction. This supports the hypothesis that vascular disease starts early in the course of childhood diabetes, akin to the situation in adults with diabetes.

Pharmacologic management of peripheral vascular disease

Although our understanding of the pathophysiology of atherosclerosis and peripheral vascular disease continues to grow, we have yet to discover a medication that can safely and efficaciously be given to most claudicants that will alleviate their symptoms to prevent disease progression. Many patients with intermittent claudication improve or remain stable without therapy if they attempt to alter their risk factors (e.g., control of diabetes, smoking cessation, lowering of cholesterol levels). However, many require concomitant drug therapy to alleviate symptoms of PVD, and some require surgical intervention. Even with the recent advances in therapeutic development and the promise of agents currently in clinical trials, the questions of who to treat, when treatment should begin, and which agent to use remain uncertain.

Current and future drug therapies for claudication

The primary objectives of claudication treatment are to reduce cardiovascular mortality and improve walking ability. Patients with claudication have 60% mortality over 10 years, with most deaths due to myocardial infarction and stroke. Aggressive risk-factor modification is required in all these patients, particularly smoking cessation, lipid modification, and treatment of hypertension, diabetes and elevated homocysteine levels. Aspirin, ticlopidine and clopidogrel are all effective in reducing the risk of myocardial infarction, stroke and vascular death, and thus antiplatelet therapy should be considered in all claudicants. Patients with disabling claudication should be considered for therapies that relieve claudication pain and improve exercise performance, the most effective being exercise training and smoking cessation. Pentoxifylline, the only approved claudication drug in the United States, has modest efficacy in improving treadmill exercise performance. Other drugs shown to be of some benefit in patients with claudication include propionyl-L-carnitine, cilostazol and possibly prostaglandin derivatives. Several antiplatelet agents and angiogenic growth factors are also being evaluated for the treatment of claudication.