Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
1999-11-29
2002-07-23
Naff, David M. (Department: 1651)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C106S124100, C106S424000, C106S001150, C106S001150, C435S174000, C514S002600, C530S350000, C530S402000, C530S810000
Reexamination Certificate
active
06423333
ABSTRACT:
INTRODUCTION
1. Technical Field
The field of this invention is physiologically acceptable compositions for use as tissue adhesives and sealants.
2. Background
In many situations, there is a need to bond separated tissues. Sutures and staples are effective and well established wound closure devices. However, there are surgical procedures where classical repair procedures are unsatisfactory, limited to highly trained specialists (e.g. microsurgery), or not applicable due to tissue or organ fragility, inaccessibility (e.g. endoscopy procedures), or fluid loss, including capillary “weeping”. Tissue adhesives and sealants have been developed to meet these needs. They may be used to seal or reinforce wounds that have been sutured or stapled, as well as finding independent use. The leading commercial products are fibrin glues and cyanoacrylates. However, both products have significant limitations which have prevented their widespread use.
Cyanoacrylates are mainly used for cutaneous wound closure in facial and reconstructive surgery. The appeal of cyanoacrylates is their speed of bonding, which is almost immediate, and its great bond strength. However, its speed of bonding can be a disadvantage, since glued tissue must be cut again in order to reshape it to the desired conformation. Additionally, it can only be used on dry substrates since its mode of action is through a mechanical interlock, limiting its use as a sealant, and it is relatively inflexible compared to surrounding tissue. Cyanoacrylates are also known to be toxic to some tissues and although it is not considered to be biodegradable, potential degradation products are suspected to be carcinogenic.
Fibrin glues comprising blood-derived fibrinogen, factor-XIII and thrombin function primarily as a sealant and hemostat and have been used in many different surgical procedures within the body. They have been shown to be non-toxic, biocompatible and biodegradable. They are able to control excessive bleeding and decrease fibrosis. However, tissues bonded with fibrin cannot be subjected to even moderate tensile stress without rupturing the bond. It takes about three to ten minutes for an initial bond to develop, but requires about 30 minutes to several hours for full strength to develop. Depending upon the application, the product may also resorb too quickly. Use of recombinantly produced fibrinogen, factor XIII, thrombin and related components (e.g. fibrin, activated factor XIII) has not been demonstrated to improve the setting time or strength of fibrin glues. Fibrin glues derived from heterologous, human and animal, serum may provoke undesirable immune responses, and expose the patient to the potential risk of viral infection. Autologous fibrin glues may be impractical to obtain and use and may compromise patient safety.
There is, therefore, substantial interest in developing products which have the biocompatibility of fibrin glues, but which set more quickly and have enhanced strength. These products should be readily available, desirably from other than natural sources, be easily administered and capable of resorption over time.
Relevant Literature
Tissue adhesives are described in: Tissue Adhesives in Surgery, Matsumoto, T., Medical Examination Publishing Co., Inc. 1972 and Sierra, D. H.,
J. Biomat. App.
7:309-352, 1993. Methods of preparation of protein polymers having blocks of repetitive units are described in U.S. Pat. No. 5,243,038 and EPA 89.913054.3.
SUMMARY OF THE INVENTION
Polymeric compositions and methods for their use are provided, where the polymeric compositions are capable of in situ chemical crosslinking to provide novel crosslinked polymeric products, which have good mechanical and biological properties, as exemplified by strong adherent bonds to tissue. The compositions can be used in a variety of applications related to their physical, chemical and biological properties, to bond to separated tissue to provide at least one of the characteristics of a stable, flexible, resorbable bond.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
The subject compositions comprise high molecular weight recombinant polymers having one or a combination of repeating units related to naturally occurring structural proteins. Of particular interest are the repeating units of fibroin, elastin, collagen, and keratin, particularly collagen and combinations of fibroin and elastin. The polymers have functional groups which can be chemically crosslinked under physiological conditions with physiologically acceptable crosslinkers, so as to form a composition which has strong adherent properties to a variety of substrates, has strong mechanical properties in maintaining the joint between the substrates, and can be formulated to have good resorption properties.
Of particular interest, the subject compositions provide strongly adherent bonds to tissue to maintain separated tissue in a contiguous spacial relationship. The subject compositions may also be employed as sealants, where the compositions may serve to fill a defect void in tissue, to augment tissue mass or bond synthetic materials to tissues. The subject compositions may also serve as depots in vivo by being mixed with a drug composition, either when used as an adhesive for bonding tissue together or for other bonding or solely as a slow release source of the drug.
The functionalities for crosslinking may be all the same or combinations of functionalities and may include the functionalities of naturally occurring amino acids, such as amino, e.g. lysine, carboxyl, e.g. aspartate and glutamate, guanidine, e.g. arginine, hydroxyl, e.g. serine and threonine, and thiol, e.g. cysteine. Preferably, the functionality is amino (including guanidine).
The polymers will have molecular weights of at least about 15 kD, generally at least about 30 kD, preferably at least about 50 kD and usually not more than 250 kD, more usually not more than about 150 kD. The polymers will have at least two functionalities, more usually at least about four functionalities, generally having an equivalent weight per functionality in the range of about 1 kD to 40 kD, more usually in the range of about 3 kD to 20 kD, preferably in the range of about 3kD to 10 kD, there being at least 3, usually at least 6, functionalities available for crosslinking. If desired, one may use mixtures of polymers, where the polymers have combinations of functionalities or have different functionalities present e.g. carboxyl and amino, thiol and aldehyde, hydroxyl and amino, etc. Thus, depending upon the functionalities and the crosslinking agent, one can form amides, imines, ureas, esters, ethers, urethanes, thioethers, disulfides, and the like.
The individual units in the polymer may be selected from fibroin, GAGAGS (SEQ ID NO:01); elastin, GVGVP (SEQ ID NO:02); collagen GXX, where the X's may be the same or different, and at least 10 number % and not more than 60 number % of the X's are proline, and keratin, AKLK/ELAE (SEQ ID NO:3). The desired functionality may be substituted for one of the amino acids of an individual unit or be present as an individual amino acid or part of an intervening group of not more than about 30 amino acids, usually not more than about 16 amino acids. In the former case, within a block of repeats, one or more of the repeats is modified to introduce a crosslinking functionality which would otherwise not normally be present. Thus a valine may be replaced with a lysine, a glycine with an arginine, an alanine with a serine, and the like. In the latter case, there would be an intervening functionality between a block of repeat units, where the number of intervening functionalities would be based on the ranges indicated previously.
Of particular interest are copolymers, either block or random, preferably block, where in the case of elastin and fibroin, the ratio of elastin units to fibroin units is in the range of 16-1:1, preferably 8-1:1, where blocks may have different ratios. Normally, in block copolymers, each block will have at least two units and not more than about 32 units, usually not more than a
Cappello Joseph
Stedronsky Erwin R.
Flehr Hohbach Test Albritton & Herbert
Naff David M.
Protein Polymer Technologies, Inc.
Trecartin Esq. Richard F.
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