Quantitative evaluation of local drug delivery using the InfusaSleeve catheter

Local Endovascular Delivery, Gene Therapy, and Cell Transplantation for Peripheral Arterial Disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

Local endovascular delivery, gene therapy, and cell transplantation for peripheral arterial disease

Advances in catheter technology, gene identification, and cell biology may provide novel treatment options for patients with peripheral arterial disease (PAD) who are not candidates for standard revascularization procedures. Animal studies and recent results in human beings suggest that transfer of growth factors or regulatory genes and transplantation of progenitor cells may provide novel therapy options by inducing therapeutic angiogenesis or by inhibiting restenosis. This review will discuss the development of a variety of catheters for localized endovascular delivery, as well as the various cellular and genetic strategies that exist to restore blood flow to ischemic tissue and to reduce neointimal hyperplasia.

Development of a water-soluble matrix metalloproteinase inhibitor as an intra-arterial infusion drug for prevention of restenosis after angioplasty

To prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA) and/or stenting of atherosclerotic stenosed arteries, we designed and developed two water-soluble matrix metalloproteinases (MMPs) inhibitors. The first inhibitor was monomeric in type and was chemically synthesized by succinylation of the synthetic MMP inhibitor, N-hydroxy-5-hydroxy-2(S)-methyl-4(S)-(4-phenoxybenzoyl)aminopentanamide (ONO-M11-335). The second inhibitor was polymeric and was a radical copolymer of the vinyl derivative of ONO-M11-335 and a water-soluble monomer, N,N-dimethylacrylamide (DMAAm). For the second inhibitor, NMR analyses and UV-vis spectra measurements showed that the content of the ONO-M11-335 unit in the copolymers (M(n); ca. 10 000 and 20 000 by GPC measurements) was about 8 per molecule. The MMP inhibitors were all highly soluble in water, even under neutral pH. The succinylated derivative markedly inhibited MMP-2, MMP-9, and MMP-12 in vitro, as did ONO-M11-335. In contrast the copolymers, which can maintain effective plasma levels for extended periods by prevention of hepatic uptake, showed a ca. 100-fold reduced inhibition activity. Such water-soluble MMP inhibitors, developed in this study, may potentially be useful as an intra-arterial infusion drug for vascular injury.

Imaging of vascular gene therapy

Gene therapy is an exciting frontier in medicine today. Many genes have been shown to be useful for treatment of various vascular diseases, including chronic cardiac and limb ischemia syndromes, vasculoproliferative disorder, hypercholesterolemia, atherosclerosis, thrombosis, and hypertension. Precise delivery of genes into target vessels, efficient transfer of genes into vascular cells of the target, and prompt assessment of gene expression over time are three challenging tasks for successful vascular gene therapy. Thus, in vivo imaging methods that can be used to monitor gene delivery and localize gene expression are needed. Modern imaging techniques provide an opportunity to monitor and direct vascular gene therapy. Radiologists play a key role not only in developing and mastering endovascular genetic interventions but also in assessing the success of vascular gene therapy and directing further refinement of vascular gene therapy technology. This article provides an overview of the current status of imaging of vascular gene therapy.

PhotoPoint photodynamic therapy with local drug delivery eliminates vessel wall cells in arteriovenous graft models

PURPOSE

To demonstrate the feasibility of PhotoPoint photodynamic therapy (PDT) with local drug delivery, optimize dosimetry in a rabbit jugular vein model, and investigate its ability to deplete potential neointimal precursor cells in the vessel wall in a canine arteriovenous graft (AVG) model.

METHODS AND MATERIALS

Photosensitizer MV2101 was administered locally in rabbit veins, incubated for 0-40 min and activated with external laser light. In canine veins, MV2101 was incubated for 30 min and activated by light. Tissues were excised at acute and chronic timepoints.

RESULTS

PhotoPoint PDT reduced cell populations in both models with maximum depletions occurring at 20 min (> or = 100 J/cm2) in rabbit veins (> 90% depletion) and 30 min (200 J/cm2) in canine veins (> 85% depletion). Chronic veins revealed no evidence of PhotoPoint PDT-related abnormalities.

CONCLUSIONS

PhotoPoint PDT with local MV2101 dramatically depleted potential neointimal precursor cells in the vessel wall. This suggests local drug delivery is feasible and that PhotoPoint PDT may be an efficacious treatment that could prolong AVG patency in the clinic.

Long-term retention of a novel antioxidant sulphur-substituted fatty acid analogue after local delivery in porcine coronary arteries

OBJECTIVE

Antioxidants have been suggested to reduce restenosis after balloon angioplasty. A novel sulphur-containing fatty acid, tetradecylthioacetic acid (TTA), with antioxidant properties, is efficiently incorporated into cellular phospholipids. We have determined the uptake and retention of TTA after local coronary artery delivery in 20 pigs.

DESIGN

Radiolabelled TTA was delivered to 40 main coronary arteries via a multiporous coronary angioplasty balloon catheter inflated before, after, or without overstretch vessel injury. The animals were killed at intervals of up to 6 weeks post-procedure. The radioactivity of the tissue sections was determined as nmol TTA/g tissue.

RESULTS

Concentrations of TTA in the coronary arteries were 1.84 +/- 0.45 nmol/g up to 24 h, 1.50 +/- 0.96 nmol/g at 2 weeks, 0.22 +/- 0.11 nmol/g at 4 weeks and a trace was present at 6 weeks (p-value for trend <0.01). The arterial wall uptake at the delivery site was higher than distal to delivery (1.84 +/- 0.37 vs 0.55 +/- 0.13 nmol/g, p = 0.006) and perivascular fat (p < 0.01) but not higher than in the myocardium. Infusion before, after or without vessel injury was not important for tissue concentration.

CONCLUSIONS

After local coronary artery delivery, the antioxidant TTA is taken up by the arterial wall in which it is retained for at least 4 weeks.

Local drug delivery: an emerging approach in the treatment of restenosis

Very limited success has been demonstrated with systemic pharmacological treatment to reduce the incidence of restenosis following angioplasty in patients. The lack of success of many of the pharmacotherapeutic agents in reducing the restenosis rates post-angioplasty and following stent implementation is believed to arise from inadequate concentrations of the agents at the lesion site. This has led to the development of various local delivery devices that would ideally deliver and retain adequate amounts of drug to the vessel wall for sufficient periods of time to ensure a therapeutic effect without inducing further injury or compromising blood flow. Local dosing would avoid systemic toxicity, and the use of modified balloon catheters or coated stents might enable percutaneous approaches.

Local drug delivery: impact of pressure, substance characteristics, and stenting on drug transfer into the arterial wall

Injection parameters for local drug delivery are frequently determined by studies with marker substances. However, the pharmacologic properties of the actual drug may influence delivery efficiency and lead to different results. Aim of this study was to assess the delivery capacities of two device-drug combinations in order to verify this approach for further in vivo studies. Tritiated (3H) preparations (5 ml) of the hydrophylic low-molecular-weight heparin reviparin and the lipophilic taxane paclitaxel were injected into the left anterior descending artery of freshly explanted porcine hearts with the Infusasleeve II catheter system. A balloon support pressure of 6 atm and infusion pressures of 40, 60, 80, or 100 psi were used. In three additional groups, reviparin was injected following stent implantation and paclitaxel was injected prior to or following stent implantation. Arteries along with surrounding myocardium were harvested. The artery was carefully dissected, and artery and myocardium were separately homogenized, and activity was measured. Of the totally delivered activity, 0.09%+/-0.03% (40 psi) to 0.17%+/-0.13% (100 psi) of reviparin and 2.03%+/-0.67% (60 psi) to 2.68%+/-1.57% (100 psi) of paclitaxel were found in the vessel wall. The results for different injection pressures were not significantly different for either drug. The percentage activity delivered to the vessel wall was substantially larger in the paclitaxel group as compared to reviparin delivery (P < 0.01 at 60, 80, and 100 psi). The mean concentration of reviparin in the artery was 20 to 33 times higher than in the myocardium. For paclitaxel the factors were 110 to 243. Stent implantation prior to or following local delivery did not result in a different delivery efficiency. The results demonstrate that the characteristics of the delivered drug contribute largely to the delivery efficiency. Using identical injection parameters, drug concentrations in the arterial wall were significantly higher for the lipophilic paclitaxel as compared to the hydrophilic reviparin. Stenting of the artery did not influence delivery efficiency.