Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Drug delivery
Reexamination Certificate
2000-01-20
2002-03-12
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Drug delivery
Reexamination Certificate
active
06355063
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to medical devices, and more particularly, to an expanded polytetrafluoroethylene (ePTFE) based graft for delivering an agent into a natural tissue conduit, e.g., a blood vessel.
2. Description of Related Art
Providing frequent, direct delivery of bioactive agents to a natural tissue conduit has become a necessity for many medical treatments such as those requiring frequent intravenous administration of drugs. To meet this need, many types of devices including stents and vascular grafts have been used to deliver agents into natural tissue conduits.
Local delivery is advantageous in that the effective local concentration of a delivered drug can be much higher than can normally be achieved by systemic administration. Delivery of agents to vascular tissue to prevent restenosis is especially useful. U.S. Pat. No. 5,399,352 to Hanson discloses a device for delivering an effective concentration of a therapeutic agent locally at a target site within the body without producing unwanted systemic side effects. However, the device described in this reference differs considerably from existing vascular grafts. It would be especially advantageous to deliver drugs with a device more similar to currently used vascular grafts.
Stents and other existing devices are frequently coated with or impregnated with therapeutic agents for the treatment of diseases. A concern related to the use of stents and existing devices for drug delivery is that drug delivery may not be sustainable. Over time the concentration of drug on the stent or other similar delivery devices will diminish, through drug inactivation, degradation, or dilution. Thus, the therapeutic agent may need to be refreshed or even changed after implant of the device. Moreover, these existing devices are not capable of delivering drugs to an internal lumen along the entire length of the graft.
Accordingly, it would be desirable to provide a drug delivery graft capable of delivering a drug or any other agent to the internal lumen along the entire length of the graft, or restrict delivery to a finite area on the graft such that the agent may be renewed or altered after implant of the graft. Furthermore, a desirable drug delivery graft could be implanted in the same fashion as regular vascular grafts.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, an improved expanded polytetrafluoroethylene (ePTFE) drug delivery graft is provided. The invention can be used, for example, as a vascular graft providing sustained release of a selected bioactive or diagnostic agent directly into a blood or other fluid flow pathway. The graft is capable of delivering the bioactive or diagnostic agent to the internal lumen of a vascular graft along the entire length, or of restricting delivery to a finite area of the vascular graft. Various ePTFE grafts that are reinforced by external beading are well known in the art. However, unlike previous designs that utilize a solid beading for reinforcing purposes, the present design utilizes a hollow tubing as a drug conduit. Also, the hollow tubing behaves much like the existing low profile solid beading in that it has a small diameter and can be readily implanted into the body. The hollow tubing of the present invention serves as both a spiral support and drug conduit.
A simple tubular ePTFE graft is used, which is well known to be extremely porous. A hollow tubing of non-porous PTFE, fluoroethylene polymer (FEP) or other implantable polymer is wrapped around the graft and laminated or adhered in place. The hollow tubing may be wrapped helically; alternatively other arrangements (e.g., end to end loops) can be used. Before the wrapping occurs one surface of the hollow tubing is cut away (for example, laser cut), punctured repeatedly or otherwise rendered porous. When an agent such as a drug is injected into the hollow tubing, e.g., from an infusion pump or a subcutaneous access port, the drug flows through the hollow tubing and leaks through the cut or porous region and diffuses into the outer surface of the ePTFE graft. The drug diffuses into the graft where it mixes into the blood flowing therethrough and influences biological processes along the circulatory system. Depending on the drug used and the precise configuration of the device the dispensed material could have either systemic effect or have limited local effect. One particularly attractive use of the device is to dispense drugs to limit the restenosis that frequently occurs due to tissue proliferation at the site of anastimosis of an ePTFE graft to a blood vessel.
The invention takes advantage of the well-known porosity of an ePTFE graft. Impregnation of ePTFE grafts with therapeutic agents has been previously disclosed. However, the present invention allows the therapeutic agents to be renewed or altered following implant of the graft, something that is not possible with simple drug-impregnated graft materials.
A more complete understanding of the ePTFE drug delivery graft will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings that will first be described briefly.
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“Directions for Use” for XP-000945424, IMPRA, 1988 (whole document).
Impra, Inc.
Jackson Suzette J.
Morrison & Foerster
Wight Todd W.
Willse David H.
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