Injectable implants for tissue augmentation and restoration

Details Injectable implants for tissue augmentation and restoration Injectable implants for tissue augmentation and restoration

2001-04-23

2003-03-18

McDermott, Corrine (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Implantable prosthesis

Bone

Reexamination Certificate

active

06533819

ABSTRACT:

TECHNICAL FIELD
The present invention relates to the field of polymeric materials that can be used as implants (injectable or otherwise insertable) in mammals for hard and soft tissue augmentation.
BACKGROUND
A number of methods exist for plastic or reconstructive surgery using injectable implants. The implants have been used for cosmetic reasons, such as filling in dermal creases, and for medical reasons, such as in the treatment of urinary incontinence. Concerning urinary incontinence, this medical condition affects 10 million, mostly elderly, Americans at a cost conservatively estimated at more than $10 billion annually. Clearly, the commercial applications of a successful material or family of materials for tissue augmentation, including urinary incontinence, would be substantial.
An additional example of the potential for soft tissue is seen in the area of intervertebral disc repair. Each year in the U. S. low back pain results in productivity losses that are greater than for any other medical condition and results in health care costs of more than $33 billion. When disability and lost productivity are added, the economic losses exceed $100 billion per year. The common cause of low back pain is pathology of a soft tissue, the intervertebral disc. When disc degeneration occurs, a collapse of the disc space occurs, which leads to neuroforaminal narrowing and nerve impingement. Soft tissue restoration or repair of an injured intervertebral disc could theoretically occur at two levels. One level is to improve the outcome of a discectomy or laminectomy procedure by using materials to prevent the adhesions and fibrosis that result in failed back surgery syndrome. Another level is to use a material to regain the correct disc dimensions and viscoelastic properties and at the same time to provide for cellular attachment where cells can sense the forces that an approximately configured disc would sustain. To date, satisfactory materials for these purposes have not been developed.
Among the materials that have previously received serious consideration as periurethral bulking agents to combat urinary incontinence arising from such conditions as intrinsic sphincter deficiency (ISD) are a synthetic organic polymer, polytetrafluoroethylene (PTFE) (Blaivas and Jacobs,
J. Urol.
145:1214-1218 (1991); Malizia, et al.,
JAMA
251:3277-3281 (1984)), autologous fat (Santarosa and Blaivas,
J. Urol.
151:607-611 (1994)), sodium morrhuate (Murless,
J. Obstet. Gynaecol.
45:67-73 (1938)), and paraffin (Quackels,
Acta. Urol. Belg.
23:259-262 (1955)). While the initial use of PTFE indicated a 73% improvement rate for stress urinary incontinence (Blaivas and Jacobs (1991)), distant particle migration to the lungs, liver, spleen and brain was subsequently observed with formation of foreign body granulomas (Malizia, et al., supra). Other materials have been reviewed by Canning (
Dial. Ped. Urol.
14 (1991)). Injectable bioglass has also been considered, but a 16- to 18-gauge needle appears to be required for injection, which results in tissue damage and leakage of the bioglass (Walker, et al.,
J. Urol.
148:645-647 (1992)).
Collagen, a natural component of connective tissue, has also been used for soft tissue augmentation (U.S. Pat. No. 5,428,022; Richardson, et al.,
Adult Urology,
46:378-381 (1995); Frank, et al.,
Plastic and Reconstructive Surgery
87:1080-1088 (1991); WO95/26761), as have polymer conjugates, such as polyethyleneglycol (U.S. Pat. No. 5,476,666). A glyceraldehyde cross-linked bovine dermal collagen with reduced antigenicity and increased resistance to fibroblast-secreted collagenases emerged as a promising material with about 80% of treated patients being either cured or improved after injection with this material (Richardson, et al. (1995); Stricker and Haylen,
The Medical Journal of Australia,
158:89-91 (1993)). However, recent studies have shown that the cure rate is actually 25%, with 46% of the successful cases needing repeated injections within 3 years, i.e., a cure rate of 10-15% at the 3 year mark. Herschorn, et al.,
J. Urol.
156:1305-1309 (1996). In addition, up to 5% of patients exhibit a hypersensitivity reaction following the required intradermal skin test with this material (Siegle, et al.,
Arch. Dermatol.
120:183-187 (1984)), and are thus not suitable candidates for collagen therapy. The injection results in a mild inflammatory response in which the injected collagen attracts nearly equal amounts of host collagen over a period of about six months, resulting in permanent scarring (Stricker and Haylen (1993)). Such scarring can complicate further efforts at treatment. Furthermore, the material is completely degraded in 9 to 19 months, resulting in a need for repeated injections (Appell,
The Craft of Urological Surgery
21(1):177-182 (1994)).
Artificial bioelastic polypeptides are a relatively new development that arose in the laboratories of the present inventor and are disclosed in a series of previously filed patents and patent applications. For example, U.S. Pat. No. 4,474,851 describes a number of tetrapeptide and pentapeptide repeating units that can be used to form a bioelastic polymer. Specific bioelastic polymers are also described in U.S. Pat. Nos. 4,132,746; 4,187,852; 4,589,882; and 4,870,055. U.S. Pat. No. 5,064,430 describes polynonapeptide bioelastomers. Bioelastic polymers are also disclosed in related patents directed to polymers containing peptide repeating units that are prepared for other purposes but which can also contain bioelastic segments in the final polymer: U.S. Pat. Nos. 4,605,413; 4,976,734; and 4,693,718, entitled “Stimulation of Chemotaxis by Chemotactic Peptides”; U.S. Pat. No. 4,898,926, entitled “Bioelastomer Containing Tetra/Pentapeptide Units”; U.S. Pat. No. 4,783,523 entitled “Temperature Correlated Force and Structure Development of Elastin Polytetrapeptide”; U.S. Pat. No. 4,500,700, entitled “Elastomeric Composite Material Comprising a Polypeptide”; U.S. Pat. No. 5,250,516 entitled “Bioelastomeric Materials Suitable for the Protection of Wound Repair Sites”; U.S. Pat. No. 5,527,610 entitled “Elastomeric Polypeptide Matrices for Preventing Adhesion of Biological Materials”; and U.S. Pat. No. 5,336,256 entitled “Elastomeric Polypeptides as Vascular Prosthetic Materials”.
A number of other bioelastic materials and methods for their use are described in pending U.S. patent applications, including: U.S. Ser. No. 08/316,802, filed Oct. 3, 1994, entitled “Bioelastomeric Drug Delivery System”; U.S. Ser. No. 08/187,441, filed Jan. 24, 1994, entitled “Photoresponsive Polymers”; U.S. Ser. No. 08/487,594, filed Jun. 7, 1995, entitled “Polymers Responsive to Electrical Energy” and published as PCT/US96/09776; U.S. Ser. No. 08/735,692, filed Oct. 16, 1995 entitled “Bioelastomers Suitable as Food Product Additives” and published as PCT/US96/05266; U.S. Ser. No. 08/542,051 filed Oct. 13, 1995, entitled “Hyperexpression of Bioelastic Polypeptides”; U.S. Ser. No. 08/543,020 filed Oct. 13, 1995, entitled “A Simple Method for the Purification of a Bioelastic Polymer” and published as PCT/US96/05186. All of the aforementioned patents and patent applications are herein incorporated by reference, as they describe in detail bioelastomers and/or components thereof and their preparation.
Artificial bioelastic materials are based on elastomeric and related polypeptides comprised of repeating peptide sequences (Urry,
Angew. Chem.
(German) 105:859-883 (1993);
Angew. Chem. Omt. Ed. Engl.
32:819-841 (1993)). As a result of work conducted by the present inventor, the bioelastic polypeptides based on VPGVG have been found to be soluble in water below 25° C., but on raising the temperature they associate reversibly to form a dense, water-containing viscoelastic phase in the polypentapeptide (“PPP”) and polytetrapeptide (“PTP”) cases, whereas the polyhexapeptide (“PHP”) associates irreversibly in water to form a granular precipitate, which usually requires the addition of trifluoroethanol to the aggregate for redissolution. The viscoelastic phase

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