Vascular Therapies has raised $12.4 million from 29 investors as part of a $21.1 million round, according to a document filed last week with the SEC.

The Cresskill, N.J.-based company is developing a sirolimus-eluting collagen implant for patients with end-stage renal disease. The bioresorbable drug-delivery system is designed to keep open a portal of entry into a patient’s vascular system for hemodialysis.

Roughly 70% of ESRD patients depend on hemodialysis, according to Vascular Therapies, and patients traditionally undergo treatment three times a week.

To prepare a patient’s body for dialysis, a surgeon connects an artery and a vein in the forearm or upper arm, establishing a “vascular anastomosis” – or an arteriovenous fistula. Once the fistula is created and blood begins to flow, it begins to widen in a process known as fistula maturation. This process is essential to successfully treating patients using hemodialysis.

But this approach brings about its own set of problems, Vascular Therapies noted. Over time, cells surrounding the fistula begin to rapidly multiply, causing tissue growth. This process narrows the vascular access port, rendering the fistula useless.

Until a fistula is fully mature, patients undergo dialysis using a catheter. Vascular Therapies is investigating whether it can help limit the time patients spend using catheters and lessen the fistula maturation failure rate using its localized drug-delivery implant.

“Reducing the time between surgery and when the fistula can be cannulated successfully for dialysis and minimizing the need for additional, 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,” the company wrote on its website.