Safety and efficacy of local periadventitial delivery of sirolimus for improving hemodialysis graft patency: first human experience with a sirolimus-eluting collagen membrane (Coll-R).

Background: Neointimal hyperplasia causes a high rate of hemodialysis synthetic graft failure. Thus, therapies that inhibit neointimal hyperplasia are urgently needed. The Coll-R is a sirolimus-eluting collagen matrix designed for intra-operative perivascular implantation around the graft-venous anastomosis. Sirolimus is an anti-proliferative drug that has proven clinical utility in suppressing neointimal tissue growth in coronary artery disease when delivered locally to the vascular wall by an endovascular drug eluting stent.

Methods: A cohort of 12 chronic hemodialysis patients underwent surgical placement of 13 polytetrafluoroethylene grafts + Coll-R and were followed for up to 24 months. The primary endpoint was safety (freedom from device related adverse events). Secondary endpoints were pharmacokinetics of sirolimus release, success of Coll-R implantation and primary unassisted graft patency.

Results: There were no technical failures, infections, vascular anastomotic or wound-healing problems. Whole blood sirolimus levels rose to a mean peak of 4.8 ng/mL at 6 h and fell to <1 ng/mL at 1 week (n = 5). Twelve and 24-month primary unassisted patencies were 76 and 38%, respectively, and the thrombosis rate was 0.37/patient-year.

Conclusions: Perivascular implantation of the Coll-R during graft surgery safely delivered sirolimus to the vascular wall. Systemic sirolimus levels were sub-therapeutic for immunosuppression. This small first-in-human study supports the concept that the Coll-R can safely deliver sirolimus to the graft-venous anastomosis. Safety and patency in this small study were sufficiently encouraging to justify randomized controlled trials to further test the efficacy of the Coll-R.