WO2004071547A1

WO2004071547A1 - Bone filling material comprising anabolic steroid

Info

Publication number: WO2004071547A1
Application number: PCT/EP2004/001227
Authority: WO
Inventors: Stephen Wohlert
Original assignee: Ethicon Gmbh
Priority date: 2003-02-12
Filing date: 2004-02-10
Publication date: 2004-08-26
Also published as: DE10305810A1

Abstract

A bone filling material comprises a matrix and an anabolic steroid. The bone filling material is preferably designed to release the anabolic steroid after the implantation. The bone filling material brings about an increased rate of bone growth, so that loading of the bone is possible earlier.

Description

BONE FILLING MATERIAL COMPRISING ANABOLIC STEROID

The invention relates to a bone filling material which shows an osteoinductive effect.

Bone becomes weak through lack of loading through long immobilization of bones, e.g. associated with trauma, fractures and tumour resections or in connection with osteogenesis for alveolar augmentations (preparation for implantation of, for example, a dental prosthesis) .

It has proved particularly suitable for osteogenesis to transplant autologous (endogenous) bone into the defect site. In the jaw region it is bone from the jaw or the iliac crest which is transplanted in particular. However, this represents additional stress for the patient .

Conventional artificial bone filling materials show only an osteoconductive, but no osteoinductive, effect. They guide the natural bone growth in the desired direction, but are unable to speed up bone growth in the defect. Loading of the bone is impossible during the healing of the defect (ingrowth of bone) . The lack of loading results in degeneration, atrophy, of the bone during this^" time. It is attempted to counteract this decline in bone substance (about 1 mm per year) by increased introduction of bone filling material.

WO 01/39812 Al discloses a bone filling material having a synthetic absorbable polymer matrix into which are introduced an antibiotic as active substance and a bactericidal absorbable glass. This material has anti- inflammatory effects but otherwise has only the osteoconductive effects mentioned.

Carriers (matrix) known for bone filling materials are blocks, porous or sintered structures, granules, pastes, gels, microspheres and composites' of these forms .

Hydroxyapatite is a widespread matrix material; it is nonabsorbable and the oldest bone substitute material. Further conventional materials are calcium phosphate in various compositions and modifications (absorbable) , e.g. dicalcium phosphate, alpha-tricalcium phosphate, beta-tricalcium phosphate, octacalcium phosphate and various mixed phosphates (Epple M, Dorozhkin SV, Die biologische und medizinische Bedeutung von Calciumphosphaten, Angew. Che . , 114, 2002, 3260-77). It is also known to use glasses and absorbable bioglass varying in composition (Hamadouche M, Meunier A, Greenspan DC, Blanchat C, Zhong JP, La Torre GP, Sedel L, Long-term in vivo bioactivity and degradability of bulk sol-gel bioactive glasses, J. Bio ed. Mat. Res., 54, 2001, 560-66, and various publications by Hench et al . ) .

Also used as matrix material are absorbable polymers

(Gerla.cn KL, Absorbierbare Polymere in der Mund- und

Kieferchirurgie, Zahnarztl. Mitt., 9, 1988, 1020-24;

Hollinger JO, Battistone GC, Biodegradable bone repair materials, CliήT' Orth. Related Res., 207, 1986, 290- 305) , which are mostly polylactides, poly-D-lactides and copolymers of glycolide and lactide, but also poly- p-dioxanone. Self-reinforced polymers increase the stability of bone (Tormala P, Biodegradable self- reinforced composite materials, Manufacturing Structure and Mechanical Properties, Clin. Mat., 10, 1992, 29-34; and as patent publications by Tormala et al.: US 6 200 318, US 6 221 075, EP 1 233 794 Al, EP 1 112 047 Al, EP 1 233 714 Al) . EP 0 878 205 Al discloses an implant with predegraded absorbable polymer, which can also be used to stop bleeding in the bone region. There is also use of collagen -(Mitchell R, The use of collagen in oral surgery, Ann. Acad. Med., 15(3), 1986, 355-60), a natural polymer, e.g. in the products "Septocoll" from Biomed Merck and "InFuse" from Medtronic, which additionally contain an active substance .

Numerous publications exist on the effect of growth factors and other active substances.

A review of the effect of growth factors on bone growth is given for example in the article of Salata LA, Franke-Stenport V, Rasmusson L, Recent outcomes and perspectives of the application of bone morphogenetic proteins in implant dentistry, Clin. Implant. Dent. Relat. Res., 4(1), 2002, 27-32.

The use of special growth factors is described in- the patent literature, e.g. BMP-2 (WO 02/085422 Al, WO 00/45871 Al, US 5 948 428), BMP-7 (WO 00/45870 Al, US 2002/0127261) and GDF-5 (US 6 281 195) .

The use of steroids is likewise known, e.g. from the literature (Falanga V, Greenberg AS, Zhou L,. Ochoa SM, Roberts AB, Falabella A, Yamaguchi Y, Stimulation of collagen .synthesis by the anabolic steroid stanozolol, J. Invest. Derm'atiol. , 111(6), 1998, 1193-97; Welder AA, Robertson JW, Melchert RB, . Toxic effects of anabolic- androgenic steroids in primary rat epithelial cell cultures, J. Pharmacol. Toxicol. Meth., 33(4), 1995, 187-95) and from the patent literature (e.g. on the release of steroids US 6 221 379 with the title "Buccal drug administration in female hormone replacement therapy" and US 2002/0004065 with^* the title "Compositions and methods to effect the release profile in the transdermal administration of active agents" and on the use of stanozolol as therapeutic agent EP 0 738 275 BI) . Anabolic steroids have for some time been administered systemically in the therapy of osteoporosis, in particular over periods of more than one year.

It is an object of the invention to provide a bone filling material which shows an osteoinductive effect.

This object is achieved by a, bone filling material having the features of claim 1. Advantageous embodiments of the invention are evident from the dependent claims .

The bone filling material of the invention has a matrix and an anabolic steroid. The bone filling material is preferably designed to release the anabolic steroid after the implantation.

The matrix may be absorbable, nonabsorbable or partially absorbable. It is introduced into the bone and fills the defect. It moreover preferably has an osteoconductive effect. The matrix acts simultaneously (directly or indirectly) as carrier of the anabolic steroid. The anabolic steroid is an active substance and has an osteoinductive effect. In this way, the formation of hew bone substance is induced and the natural bone healing is speeded up. This makes earlier loading of the bone possible, and degeneration of bone is prevented. If, for example, a dental prosthesis is to be implanted in the jaw, this is possible at an earlier time on pretreatment with the bone filling material of the invention. The main benefit for the patient is a shorter healing time, so that the bone needs to be immobilized only for a shorter period, and that the damaged bone can be loaded more quickly thereby. In the specific case of filling a defect in the jaw, this means that a change to solid food can be made earlier. The anabolic steroid displays a local effect. It is therefore possible to avoid side effects like those which may occur on systemic administration. The bone filling material of the invention may release the anabolic steroid immediately after introduction into the bone, i.e. after the implantation, or with a time lag, and over a prolonged period. This induces faster growth of osteoblasts in the vicinity of the implant. The time course of the release of the anabolic steroid can be predetermined by the mode of introduction into or onto the matrix. For example, the anabolic steroid can diffuse relatively rapidly out of pores of the matrix if it is bound therein for example only superficially by inter olecular forces. If, on the- other hand, the anabolic steroid is present in the interior of an absorbable polymer, the release over time depends on the progressive absorption of the polymer.

In one example, the anabolic steroid is mixed into a melt of polylactide, and microspheres or nanospheres shaped therefrom are introduced into a bone defect

(e.g. a bone cyst cavity). The steroid diffuses out of the spheres or is released on degradation thereof and brings about, """in the osteoblasts in the direct vicinity, an increased induction of TGF-beta2, which in turn leads to increased bone formation.

The amount of anabolic steroid in the bone filling material of the invention (expressed as absolute mass or in per cent by weight based on the weight of the matrix) may vary over a wide range depending on the application and can be established by experiment for the individual case. Data from systemic use may serve as starting point: depending on the steroid, for example, administration is between 0.5 μg/kg/day

(fluoxymesterone) via 0.1 to 3 mg/kg/day (tibolone) up to 10 mg/kg/day (testosterone) over prolonged periods (in each of these cases based on 1 kg of body weight) or, for example, single doses of 50 mg injected intramuscularly are known. When applying these dose ranges to the bone filling material, account must be taken of the local area of action (i.e. smaller weight of body tissue influenced) and the usually greater tolerability at the desired site of action (bone defect) .

Numerous different -forms are possible for the matrix of the bone filling material of the invention. For example, three-dimensional coherent implant structures, of which one piece or a few pieces (which can also be cut appropriate for requirements) are inserted into the bone defect, are suitable. Examples thereof are fleecelike structures, blocks, porous structures and sintered structures, but also basically areal implant structures and implant meshes, which may be folded if required in order to increase the thickness. Other possibilities are noncoherent materials, e.g. granules (also beads) and spheres (microspheres, nanospheres) , or pastes and gels. Combinations or composites of the aforementioned forms are likewise conceivable.

The matrix may^'"comprise inorganic or organic material. Examples of inorganic materials are: hydroxyapatite, calcium phosphates (e.g. dicalcium phosphate and octacalcium phosphate, but especially tricalcium phosphate and its modifications such as alpha- tricalcium phosphate and beta-tricalcium phosphate) , mixed phosphates, nonabsorbable glasses and absorbable glasses. So-called bioglasses varying in composition are also suitable. Examples of organic materials are: polymers (nonabsorbable or absorbable) , reinforced polymers, predegraded absorbable polymers (e.g. a copolymer of glycolide and lactide in the ratio 90:10, the absorption time of which is shortened by pretreatment in a hydrolysis buffer) , polylactides (e.g. poly-L-lactides and poly-D-lactides) , polyglycolides, copolymers of glycolides and lactides, poly-p-dioxaone and polycaprolactones, but also natural polymers, such as collagens and celluloses (e.g. alginate, starch and derivatives thereof) . The matrix may in principle comprise a plurality of different materials .

Suitable examples of anabolic steroid are tibolone, fluoxymesterone, stanozolol, nandrolone, nandrolone decanoate, nandrolone octydecanoate and testosterone, and derivatives of these substances. It is also conceivable to provide more than one anabolic steroid, so that the effects of the individual steroids can supplement one another.

For the purposes of the invention, vitamin D3 and its derivatives (e.g. 1-alpha-hydroxy-vitamin D3) are also to be regarded as anabolic steroid. Vitamin D3 is chemically related to anabolic steroids and shows in the low dose range an osteoinductive effect by promoting incorporation of calcium into the bone.

There is a large^' number of possible ways for the anabolic steroict to be introduced into or attached to the matrix and, where appropriate, to be connected to the matrix, optionally also in such a way that the anabolic steroid is released in a predetermined manner over time. For example, anabolic steroid can be present in a coating of the matrix. If the coating comprises an absorbable base substance, the anabolic steroid is released during the absorption process. A further possibility is for anabolic steroid to be present inside the matrix, for example in a matrix of absorbable material. The release of active substances from spheres is described in the literature (e.g. Matsumoto J, Nakada Y, Sakurai K, . Nakamura T, Takahashi Y, Preparation of nanoparticles consisting of poly (L-lactide) -poly (ethylene glycol) -poly (L-lactide) and their evaluation in vitro, Int. J. Pharm. , 185(1), 1999, 93-101) .

Coatings with the anabolic steroid can be applied to the matrix for example- by spraying on or by dipping processes. If the anabolic steroid is to be introduced into the interior of the matrix, suitable processes are, for example, swelling in a solvent^' with the anabolic steroid,. diffusion processes, dipping processes (in the case of a porous matrix) , the shaping of the matrix from a melt containing the anabolic steroid, and the use of emulsions or supercritical carbon dioxide.

A possibility supplementary to the statements heretofore is also to use the bone filling material of the invention in order to speed up, through increased collagen I synthesis, settling of an implant in contact with soft tissue if increased scar contraction does not represent a major problem.

The invention is explained further by means of examples below.

Example 1

The general effect of anabolic steroids on osteogenesis can be revealed by the following examples which are known from the literature.

In rats, intake of 1-alpha-hydroxy-vitamin D3 (0.5 μg/kg/day) , tibolone (0.1 to 5 mg/kg/day) or stanozolol (0.2 to 15 mg/kg/day), in each case orally with the feed, over a period of 16 weeks brings about an increase by a factor of about 2 in the rate of closure of femoral defects. Nandrolone and nandrolone decanoate (25 g every 3 weeks as single dose) in monkeys significantly increase bone density, bone mass and serum marker concentration compared with the control group.

In humans with osteoporosis, tibolone significantly increases bone mass (in the spine) on administration of 1.25 or 2.5 mg/day over a period of 2 years, compared with the control group. The results are similar with both doses, indicating that lower doses can likewise be employed successfully.

Stanozolol in a dose of 5 mg/day over a period of one year increases the rate of formation of new bone and the quality of the newly formed bone in humans.

Example 2 '

To fill a socket after tooth extraction, microspheres loaded with stanozolol are packed into the defect and sealed with membrane and/or periosteum. The controlled release of the active ingredient ensures the required dose over a period of from one week to 16 weeks. Compared with the control group, the rate of settling is increased and"no collapse of the defect occurs.

Comparable results are obtained on filling of bone splinter defects. The bone filling material loaded with anabolic steroid is introduced in this case in exactly the same way as a corresponding unloaded commercially available filling material.

Example 3

To produce steroid-loaded polylactide microspheres, 40 mg of polylactide (M_w 100 000) and 4 mg of 1-alpha- hydroxy-vitamin D3 are dissolved in 20 ml of methylene chloride and added dropwise from a syringe to a 0.5% strength (w/v) PVA solution. The mixture is stirred at room temperature for 2 min (Polytron reactor, Kinematica AG, Switzerland) and the solvent is slowly evaporated to precipitate the particles.

The release characteristics are determined in PBS buffer by direct concentration -determination using a calibration line by HPLC measurement. There was 80% release of the steroid from the particles after 4 weeks.

Example 4

In analogy _ to the production described in Example 3, particles with 10% by weight stanozolol are produced and are introduced into non-critical cranial defects in rabbits. Compared with an unfilled defect and with a defect filled with unloaded particles, the bony infiltration of the defect is significantly faster. This was checked by radiological and histological methods .

Example 5

5 g of poly-p-dϊόxanone with 5% by weight tibolone are extruded through a twin screw extruder (Minilab, Haake) at 130 °C, and the extrudate is cut up. After addition of liquid nitrogen, the cut pieces are ground in a hammer mill (Ika) . Particles with a size of 200 μm to 250 μm are separated out by screening and then inserted into cranial defects in miniature swine. Compared with defects filled with unloaded particles, histological investigations showed that bone healing was speeded up.

Example 6

In order to produce a foam-matrix with active ingredient, initially a 10% strength solution (w/w) of epsilon-caprolactone-co-glycolide ^" ("Monocryl", Ethicon) with 1% by weight fluoxymesterone in 1,4-dioxane is prepared by dissolving the freshly prepared polymer with subsequent filtration. The solution is then put into a silanized glass dish and equilibrated at 20 °C for half an hour in a Virtis freeze dryer

("Freeze obile 6") . It is then slowly cooled to -5°C.

In order to remove 1,4-dioxane, after 1 h a vacuum is applied (about 50 mTorr) . The temperature is then raised stepwise to_ 5°C (1 h) and then to 20°C (1 h) .

The end of the drying period is followed by flushing with dry nitrogen at room temperature (about 30 min) , and the resulting finished foams are removed. Storage likewise takes place in a dry nitrogen atmosphere.

Example 7

A polymer solution with 1% by weight of anabolic steroid as described in Example 6 is subjected to the following additional steps in the drying procedure:

- the solution is cooled in a silanized glass dish to -17°C (15 min)

- a vacuum of 100 mTorr is applied (1 h) .

Further processing then takes place as described in Example 6. This results in a foam-like matrix with vertical pores.

Example 8

In analogy to the production of a steroid-containing sponge material described in Example 6, an Ethicon "Vicryl" implant mesh PNicryl" : copolymer of glycolide and lactide in the ratio 90:10) is coated with three layers of "Monocryl" sponge with different inherent viscosities (3 dl/g, 1 dl/g, 0.5 dl/g from the inside to the outside) . The release characteristics in this case are determined by HPLC in analogy to Example 3.

Claims

1. Bone filling material having a matrix and an anabolic steroid.

2. Bone filling material according to Claim 1, characterized in that the bone filling material is designed to release the anabolic steroid after implantation .

3. Bone filling material according to Claim 1 or 2, characterized in that the matrix has one _. of the forms selected from the following group: three- dimensional coherent implant structures, fleece- like structures, blocks, porous structures, sintered structures, areal implant structures, implant meshes, granules, microspheres, pastes, gels, combinations of the aforementioned forms, composites of the aforementioned forms.

. Bone filling material according to any of Claims 1 to 3, characterized in that the matrix comprises at least one of the substances selected from the following group: hydroxyapatite, calcium phosphates"^'',^,''"' dicalcium phosphate, alpha-tricalcium phosphate, beta-tricalcium phosphate, octacalcium phosphate, mixed phosphates, nonabsorbable glasses, absorbable glasses.

5. Bone filling material according to any of Claims 1 to 4, characterized in that the matrix comprises at least one of the substances selected from the following group: polymers, absorbable polymers, reinforced polymers, predegraded absorbable polymers, polylactides, poly-L-lactides, poly-D- lactides, polyglycolides, copolymers of glycolides and lactides, poly-p-dioxanone, polycaprolactones, collagens, celluloses.

6. Bone filling material according to any of Claims 1 to 5, characterized in that the anabolic steroid comprises at least one of the substances selected from the following group: tibolone, fluoxymesterone, stanozolol, nandrolone, nandrolone decanoate, nandrolone octydecanoate, testosterone, 1-alpha-hydroxy-vitamin D3, derivatives of the aforementioned substances.

7. Bone filling material according to any of Claims 1 to 6, characterized in that anabolic steroid is present in a coating of the matrix.

8. Bone filling material according to any of Claims 1 to 7, characterized in that anabolic steroid is present in the interior of the matrix.