US Patients on Dialysis
AV Fistulae Not Suitable for Dialysis at 6 Months
Begin Dialysis on a Central Venous Catheter

Globally, hemodialysis represents the most common type of renal replacement therapy for End Stage Renal Disease (ESRD) patients. In the U.S., more than 400,000 patients are currently on hemodialysis.

During hemodialysis, two needles are inserted into the vein, one to draw the blood out, the other to return it after passing it through a dialyzer. The ideal vascular access should (a) provide longevity of use with minimal complication rates from infection and thrombosis and (b) sustain high blood flow rates to deliver the prescribed dialysis dose. A functional vascular access, therefore, is the lifeline for patients.

Physicians utilize one of two types of permanent, vascular accesses to support hemodialysis: An arteriovenous fistula (AVF) and an arteriovenous graft (AVG):

Arteriovenous Fistula
Arteriovenous Fistula
An artery and a vein are connected (anastomosed) directly to each other. Over the ensuing weeks (typically around 6 weeks), the diameter of the upstream vein enlarges and the wall of the vein thickens in response to the increased blood flow and wall stress – a process referred to as “fistula maturation.” Fistula maturation is a key event because it signals readiness for cannulation and the end of catheter dependence
Arteriovenous Graft
Arteriovenous Graft
One end of a synthetic (usually PTFE) graft is anastomosed to an artery and the other end is anastomosed to a vein. Approximately 3 4 weeks post-surgery, the body of the PTFE graft can be cannulated for hemodialysis.

Current practice guidelines recommend an AV fistula as the preferred vascular access. However, today in the U.S., approximately 80% of incident patients begin dialysis using a central venous catheter (CVC), the least preferred option.

These patients will continue to be dialyzed using a catheter until a mature AV fistula or an AV graft is ready for insertion of needles to support dialysis (the process of needle insertion is referred to as “access cannulation”). The use of catheters is associated with serious mortality and morbidity events that include infection, thrombosis and stenosis or occlusion of the central vein.

ESRD health care providers are fully cognizant of the drawbacks of catheter use for hemodialysis and recognize the urgent need to minimize dependence on catheters.


At the present time over 50% of AV fistulae and 75% of AV grafts either require follow‑on procedures or fail within 6-12 months of their creation.

[Ref: The Dialysis Access Consortium Studies (DAC)]

A flow-limiting stenosis caused by neointimal hyperplasia is responsible for a majority of the arteriovenous access failures. Venous outflow segment stenosis (above) is responsible for over 50% of the cases of fistula non-maturation.

Approximately 85% of AV graft dysfunction (presenting as graft thrombosis and access closure) results from a flow-limiting stenosis (above) caused by neointimal hyperplasia at the graft‑venous anastomosis.

Sirogen™: A Potential Solution

Sirogen™ is a novel bio-resorbable collagen-based drug delivery system. Vascular Therapies is evaluating local (perivascular) delivery of sirolimus, which starts intra-operatively soon after the surgical creation of the vascular access is successfully completed.

The lipophilic sirolimus molecule combines with the lipid elements in the wall of the blood vessel and reduces (down regulates) cellular proliferation, a known effect of the drug when delivered to the vessel wall. Tissue pharmacokinetic studies in animal model pre-clinical studies show persistence of drug sirolimus for at least eight weeks after the surgical implant commencement of drug delivery.

The collagen delivery system is designed to maintain its cylindrical shape without the need for sutures and to permit the expected increase in vein diameter – an integral part of fistula maturation.

Approximately 80% of patients in the United States initiate dialysis with a catheter. These patients will continue to be catheter-dependent until a fistula (or an AV graft) becomes ready for dialysis.

Increasing the proportion of fistulae that can be used for successful hemodialysis is one of the important clinical goals for Sirogen™. Additionally, reducing the time between surgery and when the fistula can be used, cannulated successfully for dialysis and minimizing the need for supplementary interventions to help maintain fistula functionality are extremely clinically relevant outcomes. Achieving these endpoints are expected to reduce catheter dwell time and catheter dependence – a much-desired outcome with important implications for patients, dialysis providers and payors.

See How it Works

Caution: FDA has tentatively approved the proprietary tradename Sirogen™  for Vascular Therapies’ formulation of sirolimus. Sirogen™ is an investigational product that is not available for sale in any country.