A number of drug delivery systems are known in the prior art.

For example, a controlled drug-release preparation using as a carrier a hydrophobic polymer material, which is non-degradable after administration into the living body. There are two methods of controlling release of a drug from such preparation; one, using an additive such as an albumin, and another, by forming an outer layer consisting of hydrophobic polymer alone.

However, where a disease indication requires the achievement of a high threshold blood plasma level and/or requires the delivery of multiple pharmaceutical and/or requires sustained release to be continued over an extended period at high levels, the drug delivery systems known in the prior art generally exhibit insufficient drug carrying capacity.

In addition, techniques known in the prior art for producing sustained release implants utilise a silicone based technology based on an extrusion system.

Difficulties have been encountered in attempting to scale up such techniques to commercial volumes. Difficulties have also been encountered in applying such extrusion techniques to pharmaceutical actives such as Recombinant Porcine Somatotropin (rPST). For example, such activities interfere with silicone chemistry due to their chemical composition or exhibit temperature sensitivity.

Further, sustained release drug delivery systems have been proposed for delivery of, for example, growth hormones. However, treatments providing a sustained or constant dosage of growth hormone, such as the Alza-type osmotic

pump system, have been found to be deleterious to growth and leading to reduced food intake and other negative results in animals so treated.

This has lead to treatments via daily injections or injections every second day to provide a pulsed treatment. Such treatments are, however, recognised as sub-optimal and highly labour intensive.

It is, accordingly, an object of the present invention to overcome or at least alleviate one or more of the difficulties and deficiencies related to the prior art.

Accordingly, in a first aspect of the present invention, there is provided a sustained release delivery apparatus including a silicone support material; a pharmaceutically active composition carried in or on the silicone support material ; the pharmaceutical active composition including at least one growth and/or reproduction-associated pharmaceutical component; analogue thereof or derivative thereof; and a carrier therefor.

It has surprisingly been found that the sustained release delivery apparatus according to the present invention may be utilised to deliver pharmaceutical actives, for example growth hormones, which heretofore have proved ineffective and/or sub-optimal in a sustained release form.

The sustained release delivery apparatus may take the form of a coated molded rod or dispersed matrix structure. The sustained release delivery apparatus may be of the type described in International patent applications PCT/AU02/00865, PCT/AU02/00866 and PCT/AU02/00868 and Australian provisional patent application PR9515 and to Applicants, the entire disclosures of which are incorporated herein by reference.

A sustained release mini-implant or pellet is preferred.

The sustained release delivery apparatus according to the present invention preferably exhibits loading capacities of pharmaceutical active of 20% to 65% by weight, more preferably 25% to 50% by weight, most preferably approximately 30% to 40% by weight, based on the total weight of the pharmaceutical active composition.

Preferably the sustained release delivery apparatus may provide approximately zero order release of pharmaceutical active.

The pharmaceutical active composition, as described above, includes at least one growth and/or reproduction-associated pharmaceutical component.

The pharmaceutical component may be selected from one or more of cytokines, hormones, hormones (eg. growth hormone, growth hormone releasing factor, calcitonin, leuteinizing hormone, leuteinizing hormone releasing hormone, and insulin), growth factors (eg. somatomedin, nerve growth factor, insulin-like growth factor (IGF)), neurotrophic factors, fibroblast growth factor, and hepatocyte proliferation factor; growth factors, live vectors and live cells secreting growth hormones and RNA and DNA coding for growth hormones.

More preferably the pharmaceutical active includes one or more selected from the group consisting of cytokines, hematopoietic factors, hormones, growth factors, neurotrophic factors, fibroblast growth factor, and hepatocyte proliferation factor; and cell adhesion factors.

Recombinant porcine somatotropin (rPST) is particularly preferred.

The pharmaceutical active composition of the present invention may contain two or more drugs depending on the indication and mode of application.

The pharmaceutical active component may accordingly further include one or more actives selected from the group consisting of:

Acetonemia preparations Anabolic agents Anaesthetics Analgesics Anti-acid Anti-arthritic Antibodies Anti-convulsivants Anti-fungals Anti-histamine Anti-infectives Anti-inflammatories Anti-microbials Anti-parasitic Anti-protozoals Anti-ulcer Antiviral pharmaceuticals Behaviour modification drugs Biologicals Blood and blood substitutes Bronchodilators and expectorants Cancer therapy and related Cardiovascular pharmaceuticals Central nervous system pharma Coccidiostats and coccidiocidals Contraceptives Contrast agents Diabetes therapy Diuretics Fertility pharmaceuticals Hematinics Hemostatics Hormone replacement therapy Immunostimulants Minerals Muscle relaxants Natural products Nutraceuticals and nutritionals Obesity therapeutics Ophthalmic pharmaceuticals Osteoporosis drug Over the Counter (OTC) pharma Pain therapeutics Respiratory pharmaceuticals Sedatives and tranquilizers Transplantation products Urinary acidifiers Vaccines and adjuvants Vitamins The water-soluble pharmaceuticals useful in the sustained release delivery apparatus according to the present invention include such drugs as peptides, proteins, glycoproteins, polysaccharides, and nucleic acids.

The present invention is particularly appropriate for pharmaceuticals that are very active even in extremely small quantities and whose sustained long-term administration is sought. When used in substantially increased quantities, such pharmaceuticals may be applied to disease and related indications heretofore

untreatable over an extended period. The pharmaceutical may be exemplified by, but not limited to, one or more selected from the group consisting of cytokines (eg. interferons and interleukins), hematopoietic factors (eg. colony-stimulating factors and erythropoietin), cell adhesion factors; immunosuppressants; enzymes (eg. asparaginase, superoxide dismutase, tissue plasminogen activating factor, urokinase, and prourokinase), blood coagulating factors (eg. blood coagulating factor VIII), proteins and peptides including proteins involved in bone metabolism (eg. BMP (bone morphogenetic protein) ), antibodies and the like, derivatives thereof and analogues thereof.

The interferons may include alpha, beta, gamma, or any other interferons or any combination thereof. Likewise, the interleukin may be IL-1, IL-2, IL-3, or any others, and the colony-stimulating factor may be multi-CSF (multipotential CSF), GM-CSF (granulocyte-macrophage CSF), G-CSF (granulocyte CSF), M-CSF (macrophage CSF), or any others. Other actives may include vaccine antigens, including live vaccines.

The silicone support material may be formed from a silicone elastomer.

The silicone support material may include a liquid silicone.

The silicone support material may be of any suitable form. The sustained release support material may take the form of a support matrix or rod, preferably a coated molded rod structure.

A partially coated rod may be used. Such a structure permits further modification of the release characteristics of the sustained release delivery apparatus according to the present invention. An eccentric or asymmetric rod, optionally partially or fully coated, may be used.

In the process according to the present invention, the silicone support material may be formed from a silicone base polymer. The silicone base polymer may be of any suitable type. A biocompatible silicone base polymer is preferred.

A biosilicon component may be included. A methyl/vinyl silicone polymer is preferred.

A reinforcing filler, e. g. a fumed silica, may be included in the silicone base polymer. A silicone elastomer including fumed silica sold under the trade designations CS10401 or CS10701, and blends thereof, available from IMMIX Technologies LLC, Cri-Sil Division, have been found to be suitable. A silicone elastomer (and blends thereof) sold under the trade designations CSM 4050-1, PLY-7511 and MED 4104, available from NuSil, have also been found to be suitable.

The silicone base polymer component may be present in amounts of from approximately 15 to 80% by weight, preferably greater than 25% by weight, based on the total weight of the sustained release apparatus. The silicone base polymer can be either liquid form or"gum stock. "Preference is dictated by the type of process used to form and coat the sustained release apparatus. Blending of multiple forms is a typical procedure for obtaining the desired physical properties.

Injection-molding processes may utilize up to 100% liquid silicone base polymer. Compression-molding or transfer-molding may utilise approximately 0. 5 to 20% by weight, preferably approximately 2.5 to 7.5% by weight of a liquid silicone component.

The cross-linking agent utilised in the process according to the present invention may be of any suitable type. A siloxane polymer ; e. g. a partially methylated polysiloxane polymer, may be used.

Accordingly, in a still further aspect of the present invention there is provided a sustained release composition including at least one growth and/or reproduction-associated pharmaceutical component ; analogue thereof or derivative thereof; and a non-silicone pharmaceutical carrier therefor, in a unit dosage form.

The applicants have surprisingly found that a sustained release composition may be formulated in an effective unit dosage form, e. g. a compressed or extruded tablettimplant form without the necessity to include a silicone component.

The sustained release composition may be utilised alone, or preferably in combination with the sustained release delivery apparatus described above.

The sustained release composition may be included as a further component in the sustained release kit as described above.

The growth and/or reproduction associated pharmaceutical component may be as described above. The pharmaceutical component may be selected from one or more of the group consisting of hormones (eg. growth hormone, e. g. recombinant porcine somatotropin rPST, growth hormone releasing factor, calcitonin, leuteinizing hormone, leuteinizing hormone releasing hormone, and insulin), growth factors (eg. somatomedin, nerve growth factor, neurotrophic factors, fibroblast growth factor, and hepatocyte proliferation factor. A growth hormone, e. g. a natural or synthetic human, porcine, bovine, ovine or like growth hormone may be used. A recombinant porcine somatotropin (rPST) is preferred.

The pharmaceutical carrier may be the same as, or similar to, the pharmaceutical carriers utilised in the preparation of the mini tablet implants described above.

A water-soluble substance, or a combination of two or more water-soluble substances, is preferred. Sucrose, sodium chloride or sodium deoxycholic acid or a mixture thereof are preferred carriers. Sodium chloride or a mixture of sucrose and sodium deoxycholic acid (DCA) is particularly preferred.

The sustained release growth composition may take the form of a compressed tablet or extruded rod, optionally a covered rod or tablet. A mini- tablet implant is preferred. A silicone coating may be applied to the tablet or rod, but is not essential.

The compressed tablet formulation may include suitable fillers or excipients as discussed above. A lubricant, such as magnesium stearate, is particularly preferred.

The growth and/or reproduction-associated composition may accordingly include approximately 1 % to 20% by weight alkali metal chloride ; approximately 0.5% to 5% by weight lubricant ; and approximately 75% to 97.5% by weight growth hormone.

Preferably the composition may include approximately 5% to 15% by weight sodium chloride ; approximately 0.5% to 5% by weight magnesium stearate; and approximately 80% to 94.5% by weight recombinant porcine somatotropin.

The pharmaceutical carrier of the sustained release apparatus may be selected to permit release of the pharmaceutically active component over an extended period of time from the composition.

The carrier may include a water-soluble substance. A water-soluble substance is a substance which plays a role of controlling infiltration of water into the inside of the drug dispersion. There is no restriction in terms of the water- soluble substance so long as it is in a solid state (as a form of a preparation) at the body temperature of an animal or human being to which it is to be administered, and a physiologically acceptable, water-soluble substance.

One water-soluble substance, or a combination of two or more water- soluble substances may be used. The water-soluble substance specifically may be selected from one or more of the group consisting of synthetic polymers (eg. polyethylene glycol, polyethylene polypropylene glycol), sugars (eg. sucrose, mannitol, glucose, dextran, sodium chondroitin sulfate), amino acids (eg. glycine and alanine), mineral salts (eg. sodium chloride), organic salts (eg. sodium citrate) and proteins (eg. gelatin and collagen and mixtures thereof). A sugar, preferably mannitol, or salt, preferably sodium chloride, or mixtures thereof, are preferred.

The pharmaceutical carrier may constitute from approximately 0% to 30% by weight, preferably approximately 5% to 15% by weight based on the total weight of the pharmaceutically active composition.

The sustained release delivery apparatus may include additional carrier or excipients, fillers, plasticisers, binding agents, pigments and stabilising agents.

Suitable fillers may be selected from the group consisting of talc, titanium dioxide, starch, kaolin, cellulose (microcrystalline or powdered) and mixtures thereof.

Where the sustained release delivery apparatus takes the form of a biocompatible article, e. g. an implant, calcium fillers, e. g. calcium phosphate, are particularly preferred.

Suitable binding agents include polyvinyl pyrrolidine, hydroxypropyl cellulose and hydroxypropyl methyl cellulose and mixtures thereof.

In a preferred aspect of the present invention the sustained release delivery apparatus may take the form of a biocompatible article suitable for insertion into the body of an animal to be treated.

The biocompatible article may include a medical instrument, apparatus or prosthetic device, or part thereof.

For example, the biocompatible article may include a catheter, or prosthetic appliance, or medical implant, e. g. for reconstructive, dental or cosmetic surgery.

Implant materials for replacing or filling bone or like defects are particularly preferred.

It will be understood that by incorporating a pharmaceutical active composition in or on such biocompatible articles, a sustained therapeutic effect may be achieved at the site of insertion.

For example, growth factors, e. g. nerve growth factors, may be included, for example to assist the healing process, e. g. after surgical procedures.

The sustained release delivery apparatus of the present invention may have a rod-like shape, for example it is selected from circular cylinders, prisms, and

elliptical cylinders. When the device will be administered using an injector-type instrument, a circular cylindrical device is preferred since the injector body and the injection needle typically have a circular cylindrical shape, though other shaped objects may be used.

The size of the pharmaceutical formulation of the present invention may, in the case of subcutaneous administration, be relatively small, e. g. 1/4 to 1/10 normal size. For example using an injector-type instrument, the configuration may be circular cylindrical, and the cross-sectional diameter in the case is preferably 0.2 to 15 mm, more preferably 1 to 4 mm, and the axial length being preferably approximately 1 to 40 mm, preferably approximately 5 to 30 mm, more preferably approximately 10 to 20 mm.

The thickness of the outer layer should be selected as a function of the material properties and the desired release rate which can be regulated by varying the number of times the molded rod is coated. The outer layer thickness is not critical as long as the specified functions of the outer layer are fulfilled. The outer layer thickness is preferably 0.05 mm to 3 mm, more preferably 0.05 mm to 0.25 mm, and even more preferably 0.05 mm to 0.1 mm.

Sustained release implants according to the present invention may preferably have a double-layer structure, in order to achieve long-term zero-order release.

The ratio of the axial length of the pharmaceutical formulation to the cross- sectional diameter of the inner layer may, in any case, be one or more and is more preferably two or more and most preferably three or more.

Where a double-layer structure is used, the pharmaceutical-containing inner layer and the drug-impermeable outer layer may be fabricated separately or simultaneously. Silicone is known for swelling with water and being gas- permeable.

A pharmaceutical formulation with an open end at one terminal may be fabricated by dipping one terminal of the pharmaceutical formulation into a solution which dissolves the outer-layer material and drying it, or by coating one terminal end of the pharmaceutical formulation with a cap made from the outer-layer material. In addition, the fabrication may comprise insertion of the inner layer into an outer-layer casing with a closed-end at one terminal, which are separately produced, and also formation of the inner layer in said casing.

In a further aspect of the present invention there is provided a method for the therapeutic or prophylactic treatment of a condition in an animal (including a human) requiring such treatment, or to improve a physiological characteristic of an animal, which method includes administering to the animal a sustained release composition including at least one growth and/or reproduction-associated pharmaceutical component; analogue thereof or derivative thereof; and a non-silicone pharmaceutical carrier therefor, in a unit dosage form.

Preferably the method includes administering to the animal a sustained release delivery apparatus including a silicone support material ; a pharmaceutical active composition carried in or on the silicone support material ; the pharmaceutically active composition including at least one growth and/or reproduction-associated pharmaceutical component; analogue thereof or derivative thereof; and a carrier therefor.

The method according to this aspect of the present invention is particularly applicable to the treatment of an animal to improve nutritional and/or growth related characteristics. Accordingly, in a preferred embodiment of this aspect of the present invention there is provided a method for the treatment of an animal to improve nutritional and/or growth related characteristics, which method includes administering to the animal a sustained release delivery apparatus including

a silicone support material ; and a growth-associated pharmaceutical composition carried in or on the support material including at least one growth-associated pharmaceutical component ; and a carrier therefor; the sustained release delivery apparatus exhibiting generally zero order release administering to the animal at least one sustained release delivery apparatus, the size and/or number thereof being selected to improve at least one growth-associated physiological characteristic.

Applicants have surprisingly found that utilising the sustained release composition, improvement in nutritional and/or growth-related characteristics in an animal may be achieved while reducing or eliminating one or more of the deleterious effects of sustained release treatment encountered in the prior art. For example, the sustained release delivery apparatus may be administered using a weekly, bi-weekly, monthly or up to 6 monthly dosage regimen.

The nutritional and/or growth-related characteristics in which improvement may be made according to this aspect of the present invention include one or more selected from the group consisting of growth rate (including food conversion ratio), carcass quality (including back fat measurement), plasma urea concentrations and plasma glucose levels.

The sustained release composition may take any suitable form as described above. In a preferred embodiment of this aspect of the present invention the delivery apparatus includes one or more mini implants or pellets, as described above.

The number and/or size of the mini implants or pellets may be selected to improve one or more of the characteristics described above.

For example, for pigs, preferably 1 to 20 4 mm x 4 cm, more preferably 2 to 10 4 mm x 4 cm mini implants have been found to be suitable.

Alternatively 2 to 20 2 mm x 2 cm, preferably 5 to 20 2 mm x 2 cm mini implants may be used.

Most preferably, 1 to 20, preferably 5 to 20 3 mm x 4 cm mini implants may be used.

The growth-associated pharmaceutical component of the pharmaceutical composition according to this aspect of the present invention may be of any suitable type including live vectors and live cells secreting growth hormones as well as RNA and DNA coding for growth hormones. Preferably, the growth- associated pharmaceutical component includes a growth hormone, more preferably at least one exogenous growth hormone selected from homologous, natural or synthetic growth hormones, analogues, derivatives or fragments thereof.

A recombinant growth hormone, e. g. recombinant porcine somatotropin (rPST) is preferred.

The growth-associated pharmaceutical component may alternatively or in addition include other growth hormone and/or factors. Optionally other pharmaceutical components, as described above, may be included.

The carrier utilised in the growth-associated pharmaceutical composition may be of any suitable type. The carrier may include a salt (NaCI) and/or a sugar component as described above. Applicants have surprisingly found that the inclusion of such a component may assist in the performance of the growth associated component, e. g. growth hormone, in vivo. Whilst we do not wish to be restricted by theory, it is postulated that the carrier may assist in maintaining the biological activity and preventing aggregation of the growth hormone in vivo.

The carrier may alternatively or in addition include one or more refolding agents. The refolding agent may be of any suitable type.

The refolding agent may be selected from one or more of the group consisting of urea, anionic surfactants and cationic surfactants. A cationic surfactant is preferred.

The cationic surfactant may include a cation selected from the group consisting of : Cetyl timethylammonium cations Cetyl pyriudinium cations Tetradecyl trimethylammonium cations Dodecyl trimethylammonium cations Mixed n-alkyl dimethyl benzyl ammonium cations N, N-dimethyl-N- [2- [2- [4- (1, 1,3, 3,-tetramethyl butyl) phenoxy] ethoxy] ethyl] benzenemethanaminium cations Dodecyldimethylamine oxide N-lauroylsarcosine sodium salt N lauroyl-N methyltaurine sodium salt N-lauryl-ß-iminodipropionate sodium salt 3- (N, N-Dimethyl laurylammonio) propane sulphonate sodium salt The method of administration may include subcutaneous, intraperitoneal intramuscular injection, intranasal insertion or indwelling, intrarectal insertion or indwelling, for example as a suppository or utilising oral administration.

In a preferred form the sustained release delivery apparatus may take the form of a kit.

Accordingly, in this aspect of the present invention there is provided a sustained release kit including a plurality of sustained release mini-implants or pellets packaged for delivery in a single treatment, each mini-implant including a silicone support material ; and a pharmaceutically active composition carried in or on the silicone support material ;

the pharmaceutically active composition including at least one growth and/or reproduction-associated pharmaceutical ; analogue thereof or derivative thereof; and a carrier therefor; each implant being of insufficient size and/or payload individually to provide a predetermined desired threshold blood level of pharmaceutical active for treatment of a selected growth and/or reproduction-associated indication.

Preferably the multiple sustained release mini-implants are packaged in a biodegradable sheath Alternatively or in addition the sustained release kit may include at least one sustained release mini tablet implant packaged for delivery in a single treatment, the or each mini tablet implant including a sustained release composition including at least one growth and/or reproduction-associated pharmaceutical component; analogue thereof or derivative thereof; and a non-silicone pharmaceutical carrier therefor, in a unit dosage form; the or each implant together being of substantially reduced size and/or payload relative to an equivalent immediate release treatment.

Preferably the or each mini tablet implant has a payload of approximately 30% to 70% by weight of the total payload of an equivalent immediate release treatment for an equivalent period.

More preferably when a plurality of sustained release mini tablets implants are used, each implant is of insufficient size and/or payload individually to provide a predetermined required threshold blood level of pharmaceutical active for treatment of a selected indication.

In a preferred form, the multiple sustained release mini tablet implants are packaged in a biodegradable sheath.

The animals to be treated may be selected from mice, rats, sheep, cattle, goats, horses, camels, pigs, dogs, cats, ferrets, rabbits, marsupials, buffalo, yacks, birds, humans, chickens, geese, turkeys, rodents, fish, reptiles and the like.

The method according to the present invention is particularly applicable to larger animals, e. g. cattle, sheep, pigs, dogs and humans where high dosage levels are required to achieve the prerequisite threshold pharmaceutical active blood levels for successful achievement of improved results in growth characteristics and the like.

The present invention will now be more fully described with reference to the accompanying figures and examples. It should be understood, however, that the description following is illustrative only and should not be taken in any way as a restriction on the generality of the invention described above.

EXAMPLE 1 An A-part of the PST formulation was prepared as follows.

First a platinum masterbatch (Pt MB) was prepared by mixing on a two-roll mill : 7.0 g 60 durometer silicone-base material (base 1) 0.06 g of a platinum catalyst composition The platinum catalyst composition was diluted 1: 3 with silicone fluid.

This completed the A-part of the PST formulation.

A B-part of the PST formulation was then prepared as follows : First the following were mixed on a two-roll mill : 23.5 g rPST (freeze dried) 1. 80 g of Hydride MB (which contained 33% by weight hydride fluid)

5.2 g of silicone fluid 17.5 g 40 durometer silicone base material containing 20% w/w sugar or salt.

Table 1 below gives the amounts of each ingredient used to make each shot : Table 1 Preparation B-side Pre-Mixed Base EX849 Base Pt MB No. 1 3. 0 g 1. 10 g 80% w/w Fine Salt 0 g 0. 30 g 2 3. 0 g 1.10 g 80% w/w Fine Salt 0 g 0. 30 g 3 3. 0 g 1.10 g 80% w/w Fine Salt 0 g 0. 30 g 4 3. 5 g 0.64 g 80% w/w Fine Salt 0. 64 g 0. 35 g 5 3. 5 g 0.64 g 80% w/w Fine Salt 0. 64 g 0. 35 g 6 3.5 g 0.64 g 80% w/w Fine Salt 0.64 g 0.35 g 7 3. 5 g 0.32 g 80% w/w Fine Salt 0. 96 g 0. 35 g 8 3. 5 g 0.32 g 80% w/w Fine Salt 0. 96 g 0. 35 g 9 3. 5 g 0.32 g 80% w/w Fine Salt 0. 96 g 0. 35 g 10 3. 5 g 1. 28 g 80% w/w Fine Sugar 0 g 0. 35 g 11 3. 5 g 0.64 g 80% w/w Coarse Salt 0. 64 g 0. 35 g 12 3. 5 g 0.64 g 80% w/w Coarse Salt 0. 64 g 0. 35 g 13 3.5 g 1.28 g 205 w/w PEPPG 0 g 0.35 g 14 3. 5 g 1. 28 g 20% w/w PEPPG 9 0. 35 g

Each implant was"cold"compression molded (<20°C) and subsequently placed in an incubation oven at 70°C for fifteen minutes. The heat treatment had no apparent effect on the efficacy of the implants. All samples were then dip coated with liquid silicone and dried at 65°C for 10 minutes. This process of coating with liquid silicone can be repeated numerous times to achieve different release rates.

EXAMPLE 2 Example 1 was repeated to produce mini implants having the dimensions 3 mm x 4 cm and the composition set forth in Table 2 below.

Table 2

NaCI PST NaCI Silicone 5% 122 mg 18. 5 mg 229. 4 mg 10% 121 mg 37. 0 mg 210. 00 mg 20% 110 mg 68. 00 mg 153. 00 mg EXAMPLE 3 Mini implants having the composition of various preparations described above were subcutaneously administered to various animals including pigs, sheep and cattle. Whole blood was collected from the animal via the jugular vein daily to day 14 where the animal was sacrificed. Plasma analyses of plasma urea concentration and plasma glucose concentration were conducted utilising standard techniques.

Pigs were monitored daily by measuring feed intake, growth rate and by blood sampling in order to calculate feed conversion ratios, blood urea and glucose levels. Back fat measurements were undertaken by ultrasound at day 15.

The results are presented in Tables 3 to 6.

Table 3 Plasma Urea Concentrations-mmol/L Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 (3 mm (% NaCI) Diameter) 4xlcm 5 7 6. 8 3.9 3.6 4. 6 7.1 4 x 1cm 5 16 4.9 3.5 4.0 4.3 5.3 4 x 1cm 5 44 5.4 3.9 4.7 5.9 6.7 4 x 1cm 10 2 4.9 3.7 3.5 3.5 5.9 4 x 1cm 10 4 5.7 3.3 3.2 3.2 5.4 4xicm 10 6 4. 6 2. 2 3. 0 2. 8 4. 6 4 x 1cm 20 8 5.8 2.5 2.8 3.6 5.0 4xlcm 20 12 4. 7 2. 7 2. 3 2. 4 5. 4 4 x 1cm 20 14 6.6 3.5 4.4 5.1 2.9 Mean 5. 5 3. 2 3. 5 3. 9 5. 4 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 2 x 2cm 5 3 4.8 4.4 4.5 4.2 4.8 2 x 2cm 5 5 5.0 3.8 4.4 4.6 3.7 2 x 2cm 5 13 5.2 4.6 4.1 3.7 5.6 2 x 2cm 10 21 5. 9 3. 7 3. 8 3. 2 5. 9 2 x 2cm 10 26 6.4 3.8 5.0 3.2 4.7 2 x 2cm 10 35 6. 7 5. 4 5. 2 4. 1 5. 4 2 x 2cm 20 38 5. 2 3. 7 4. 3 3. 6 4. 9 2 x 2cm 20 40 5. 6 4. 6 5. 8 6. 0 4. 3 2 x 2cm 20 43 6.1 4.0 5.2 5.0 3.9 Mean 5. 7 4. 2 4. 7 4. 2 4. 8 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 4 x 2cm 5 23 4. 6 3. 4 3. 8 3. 0 3. 2 4 x 2cm 5 32 4. 9 3. 9 3. 9 4. 1 5. 5 4 x 2cm 5 33 6.3 4.8 3.2 3.1 7.1 4 x 2cm 10 37 6.9 4.8 4.1 3.4 3.8 4 x 2cm 10 46 4. 9 3. 3 3. 3 2. 7 4. 5 4 x 2cm 20 36 6. 7 3. 6 3. 2 2. 8 3. 2 Mean 5. 7 4. 0 3. 6 3. 2 4. 5 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 PST inj 17 5. 2 4. 1 3. 7 5. 6 5. 5 PST inj 18 6. 6 4. 5 3. 3 3. 3 4. 7 PST inj 24 4. 5 3. 9 4. 0 3. 7 3. 8 PST inj 25 6.8 5.2 4.4 4.8 6.5 PST inj 27 4. 4 3. 1 3. 5 3. 3 4. 4 PST inj 29 6. 4 4. 5 3. 9 3. 8 6. 8 PST inj 30 6. 3 4. 3 4. 2 4. 0 6. 6 PST inj 31 4. 7 3. 1 3. 1 2. 8 4. 9 PST inj 47 6. 9 4. 8 3. 7 3. 8 4. 6 Mean 5. 8 4. 1 3. 8 3. 9 5. 3 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 Control 1 4. 6 5. 8 5. 3 4. 8 4. 7 Control 9 4. 4 4. 7 4. 7 5. 1 4. 3 Control 10 8. 2 8. 5 8. 3 8. 8 8. 6 Control 11 6.6 6.7 6.6 5.3 7.0 Control 20 6. 8 7. 5 6. 6 7. 0 8. 2 Control 22 6.0 6.4 7.0 6.4 6.8 Control 34 3.9 4.6 4.9 5.0 5.6 Control 39 5.8 6.5 6.0 4.9 5.3 Control 42 5.5 5.6 6.8 6.0 6.5 Mean 5. 7 6. 2 6. 2 5. 9 6. 3 Mean Blood Urea Levels-Comparison with Negative Controls P values lcm 0.62 0.00001 0.00002 0.00314 0.15210 T test (paired) 2cm 0. 846 0. 0005 0. 003 0. 004 0. 015 2 x2cm 0. 9543 0. 0014 0. 0001 0. 0003 0. 0426 PST inj 0. 97794 0.00047 0.00001 0.00124 0.11997 Table 4 Plasma Glucose-mmol/L Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 (3 mm (% NaCI) diameter) 4xlcm 5 7 5.4 6.7 6.0 6.8 5.0 4 x 1cm 5 16 5.1 5.7 5.1 5.8 4.6 4 x 1cm 5 44 6.0 6.1 5.6 6.4 5.6 4 x 1cm 10 2 5.8 6.8 7.8 9.8 6.5 4xlcm 10 4 5. 2 6. 2 6. 2 6. 0 5. 2 4 x 1cm 10 6 5.4 5.3 6.0 6.3 4.8 4 x 1cm 20 8 5.8 7.6 6.7 7.2 5.6 4 x 1cm 20 12 5.3 7.5 7.5 8.4 5.2 4 x 1cm 20 14 4.8 6.7 5.6 6.2 5.6 Mean 5. 4 6. 5 6. 3 7. 0 5. 4 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 2 x 2cm 5 3 5.6 5.3 5.8 7.2 5.1 2 x 2cm 5 5 5.3 5.7 5.4 6.0 5.0 2 x 2cm 5 13 5.3 6.1 5.5 6.8 5.0 2 x 2cm 10 21 5.2 6.4 6.1 6.9 5.1 2 x 2cm 10 26 5. 4 6. 4 6. 9 9. 2 9. 0 2 x 2cm 10 35 6.0 6.1 6.1 7.0 6.3 2 x 2cm 20 38 5.7 5.7 5.4 6.5 5.9 2 x 2cm 20 40 6.6 7.2 6.1 7.2 8.8 2 x 2cm 20 43 5. 4 6. 0 5. 6 5. 8 5. 7 Mean 5.6 6.1 5.9 7.0 6.2 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 4 x 2cm 5 23 5. 7 6. 4 6. 0 7. 6 6. 5 4 x 2cm 5 32 5. 6 6. 1 6. 4 5. 9 5. 6 4 x 2cm 5 33 5. 8 7. 0 6. 8 8. 8 6. 0 4 x 2cm 10 37 4. 8 6. 2 5. 7 8. 0 6. 4 4 x 2cm 10 46 5. 1 5. 8 6. 3 6. 3 5. 1 4 x 2cm 20 36 5. 4 8. 5 6. 6 8. 5 6. 8 Mean 5. 4 6. 7 6. 3 7. 5 6. 1 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 PSTinj17 5.0 5.0 5.0 5.5 4.9 PST inj 18 5.2 5.9 5.7 6.2 5.1 PST inj 24 4.9 5.2 5.0 5.4 5.0 PST inj 25 5. 4 5.2 5.9 5.8 5.0 PST inj 27 5.4 4.5 5.3 5.8 4.9 PST in'29 4.8 5. 5 5. 5 6.0 5.1 PST in'30 5.4 5.5 5.7 6.3 5. 3 PST inj 31 5.6 6.0 6.0 6.5 5.1 PST inj 47 5. 1 5.5 5.6 5.7 5.8 Mean 5. 2 5. 3 5. 5 5. 9 5.1 Size Implant Pen No Day 0 Day 1 Day 2 Day 4 Day 7 Control 1 5.1 4.6 4.8 5.6 5.9 Control 9 5.3 5.1 5.1 6.3 5.1 Control 10 5.3 5.4 5.4 5.3 5.3 Control 11 5.9 5.4 5.2 4.8 5.3 Control 20 4.7 4.6 5.1 4.8 4.8 Control 22 4. 8 4. 6 4. 8 5. 4 4. 9 Control 34 5. 9 5. 4 5. 4 5. 7 5. 2 Control 39 5. 0 5. 1 4. 9 5. 2 5. 1 Control 42 5.5 5.4 5.3 5.4 7.8 Mean 5. 3 5. 0 5. 1 5. 4 5. 5 Table 5 PST Backfat Measurements at day 15 (mm) Controls PST 4 x cm 1 cm 2cm 1 14 17 9 23 11 2 11 3 12.5 9 15.5 18 12 32 11.5 4 9.5 5 10.5 10 15 24 10.5 33 9.5 6 9 13 12.5 11 14.5 25 13.5 37 11.5 8 10 21 12 20 14. 5 27 11. 5 46 13 12 12 26 13 22 12.5 29 12.5 14 14 35 13. 5 34 10 301 1 39 14 31 10 16 13. 5 42 11 47 10. 5 Mean 13. 4 11. 3 11. 3 11. 5 12. 3 SD 1. 9 1. 4 1. 25 1. 91 1. 03 P value 0. 016 0. 04 0. 05 0. 21

Compare all implanted pigs with negative controls, mean backfat is 11.6 cm and p value = 0. 01 Compare each implanted group with positive controls p value > 0.05 Table 6 Feed Conversion Ratios- Day 0 to Day 7-1 cm Day 0 to Day 14-1 cm Pen No Feed Weight FCR Pen No Feed Weight FCR 7 13. 54 5. 6 2. 42 7 26. 66 6. 8 3. 92 16 14.63 5.2 2.81 16 29.6 10.6 2. 79 44 15. 99 6 2. 67 44 32. 8 11. 8 2. 78 2 18.95 9.4 2.02 2 38.87 14.8 2. 63 4 15. 79 8. 8 1. 79 4 34. 59 15. 8 2. 19 6 13. 54 6. 4 2. 12 6 28. 77 11 2. 62 8 17. 32 9 1. 92 8 36. 65 13. 6 2. 69 12 16. 72 7. 6 2. 20 12 39. 28 14. 6 2. 69 14 11.63 3.8 3.06 14 22.67 5.8 3.91 Mean 15. 35 6. 87 2. 33 Mean 32.21 11. 64 2. 91 Day 0 to Day 7-2cm Day 0 to Day 14-2cm Pen No Feed Weight FCR Pen No Feed Weight FCR 3 13. 21 6. 2 2. 13 3 27. 23 11. 8 2. 31 5 11. 57 4. 2 2. 75 5 22. 44 7 3. 21 13 15. 65 7. 4 2. 11 13 33. 26 12. 4 2. 68 21 12. 71 7. 2 1. 77 21 29. 33 12. 8 2. 29 26 14. 46 8. 4 1. 72 26 32. 43 14. 2 2. 28 35 16. 35 6. 4 2. 55 35 33. 13 12. 8 2. 59 38 16 6. 4 2. 50 38 33. 2 14. 2 2. 34 40 21. 65 10. 6 2. 04 40 45. 05 17. 2 2. 62 43 16. 27 6. 6 2. 47 43 30. 33 9. 6 3. 16 Mean 15. 32 7. 04 2. 23 Mean 31. 82 12.44 2.61 Day 0 to Day 7-4 x 2cm Day 0 to Day 14-4 x 2cm Pen No Feed Weight FCR Pen No Feed Weight FCR 23 19. 87 9 2. 21 23 40. 97 17. 2 2. 38 32 19 8. 4 2. 26 32 38. 35 16. 4 2. 34 33 18. 89 10. 2 1. 85 33 36. 99 15. 4 2. 40 37 17. 69 9. 2 1. 92 37 35. 87 15 2. 39 46 15. 64 8. 8 1. 78 46 35. 05 15 2. 34 36 16. 46 7. 8 2. 11 36 Mean 17.925 8. 90 2. 02 Mean 37. 45 15. 80 2. 37 Day 0 to Day 7-PST Injection Day 0 to Day 14-PST Injection Pen No Feed Weight FCR Pen No Feed Weight FCR 17 14.61 5.4 2.71 17 30.61 14 2.19 18 12.81 5.6 2.29 18 25.28 11.6 2. 18 24 17. 9 10. 8 1. 66 24 38. 25 20. 2 1. 89 25 15.93 7.8 2.04 25 30.6 14.2 2. 15 27 14. 67 7. 2 2. 04 27 32. 36 17. 4 1. 86 29 16.7 9.4 1.78 29 32.71 16.2 2. 02 30 17.28 9.2 1.88 30 34.14 18.8 1.82 31 17. 56 7. 2 2. 44 31 35. 54 16. 6 2. 14 47 15. 96 7. 8 2. 05 47 30. 45 13. 8 2. 21 Mean 15. 94 7. 82 2. 10 Mean 32.22 15. 87 2. 05 Day 0 to Day 7-Controls Day 0 to Day 14-Controls Pen No Feed Weight FCR Pen No Feed Weight FCR 1 15.36 4.6 3.34 1 32.66 11.8 2. 77 9 15. 71 7. 2 2. 18 9 32. 31 13. 4 2. 41 10 21. 22 6. 4 3. 32 10 43. 28 14. 2 3. 05 11 20. 82 7. 4 2. 81 11 42. 46 13. 6 3. 12 20 20.92 7.8 2.68 20 41.24 14.4 2. 86 22 20. 89 8. 6 2. 43 22 42. 71 16. 6 2. 57 34 19.13 8 2.39 34 39.82 18 2. 21 39 16. 91 3. 4 4. 97 39 33. 14 10. 2 3. 25 42 19. 26 7. 6 2. 53 42 36. 32 15 2. 42 Mean 18.91 6.78 2. 96 Mean 38.22 14.13 2.74 New formulations allowing the controlled release have been developed based on the number of liquid silicone coatings. These are shown in Table 7.

Table 7 New formulations for PST-in vitro release data for 1 cm x 4 implants (3 mm diameter). Amount of rPST released per day (mg). Day 2 Day 3 Day 4 Day 7 Day 9 Day 14 15% NaCl 1 coat silicone 1. 857 0.961 2.669 4.236 5. 23 4. 15 10% NaCI 1 coat silicone 1. 919 1.218 3.382 5.369 6. 628 5. 26 5% NaCI 1 coat silicone 1. 379 0.354 0.984 1.562 1. 929 1. 531 10 % NaCI 2 coats silicone 1. 302 0.231 0.642 1.019 1. 258 0. 998 10% NaCI 3 coats silicone 1. 534 15% mannitol 1 coat silicone 1. 981 0. 879 2. 44 3.873 4. 782 3. 795 10% mannitol 1 coat silicone 1. 703 0. 457 1. 27 2.016 2. 486 1. 975 5% mannitol 1 coat silicone 0.917 0.056 0.156 0.258 0.307 0.2043 105 mannitol 2 coats silicone 1.657 0.097 0.271 0.43 0.53 0.421 10% mannitol 3 coats silicone 1. 672 0.231 0.642 1.019 1. 258 0. 998 5% NaCI 5 % mannitol 1 coat 2. 058 0. 334 0.927 1.472 1. 817 1. 442 5% NacCl 10% mannitol 1 coat 2. 906 0. 93 2. 583 4. 1 5. 062 4. 017 10% NaCl 5 % mannitol 1 coat 3. 029 0.961 2.669 4. 2365. 234. 14 7. 5% NaCI 7. 5% mannitol 1 coat 2. 674 0. 93 2. 583 4. 1 5. 062 4. 017 7. 5% NaCI 7. 5% mannitol 2 coats 1. 749 0. 57 1. 584 2.514 3. 104 2. 463 7. 5% NaCI 7. 5% mannitol 3 coats 1.873 0.159 0. 442 0.702 0. 866 0. 687

EXAMPLE 4 Laboratory-scale formulation of compressed tablet implants of recombinant porcine somatotropin (rPST).

The tableting procedure was as follows : the"base-formulation"was weighed into a polyethylene terephthalate container (polyethylene lid), and the weight recorded; the requisite amount of magnesium stearate was calculated and weighed into the polyethylene terephthalate container; the formulation was mixed by tumbling for ca. 15 minutes; tablets were prepared (details below) ; and subsequent to tableting (described below), the tablets were placed in polyethylene sample vials, sealed, labelled (with the sample number, study number, type of sample, date collected, and storage conditions) and placed in storage (4 °C).

The tableting protocol involved : filling the tableting die cavity with powder; compression of the powder; repeat of the above steps until the requisite loading (ca. 5,10, 30, 40,60 and 70 mg) was achieved; ejection of the full tablet (or parts thereof) from the die cavity by raising the lower punch.

Pressing pressure : ca 1200 psi Conditions : Temperature = 20°C Humidity = ambient Tablet properties : Dimension : nominal 2.95 mm diameter x length (in mm) as required Mass per tablet : nominal 5 mg per 1.0 mm tablet Sodium chloride (NaCI) is finely ground utilising a mortar and pestle prior to tableting.

Details of the tablet batches are provided in Table 8.

TABLE 8 Batch rPST-NaCI mass (g) Mg stearate Tablet data ID (% rPST-NaCI) mass (g) 1 2.217 (97.3) 0.062 154 tablets Smart Tab M average length = 3 mm/tablet average mass = 14.8 mg/tablet Pure rPST 13 mg/tablet 2 2. 325 (97.3) 0. 065 144 tablets Smart Tab A average length = 3.4 mm/tablet average mass = 16.6 mg/tablet Pure rPST 13 mg/tablet (PST only 90% pure)

A number of the compressed tablets were implanted via sub-cutaneous injection in pigs. The results illustrating improved feed conversion efficiency, fat reduction, etc are shown in Table 9.

TABLE 9 0-7 days No of Implant size Feed intake Weight FCR pigs PST (kgs) increase (kgs) Group 1 6 5 mg/day 16.33 8.30 1.97 PST Injection A Group 2 6 5 mg/day 16. 78 9.43 1.78 PST Injection M Group 8 6 17. 18 6.03 2.85 Sham Control Group 4 6 13 mg 13.95 7.53 1.85 Smart Tab M 3 x per week Group 5 6 14 mg 16.77 8.00 2.10 Smart Tab A 3 x per week

EXAMPLE 5 The pig experiments illustrated in Example 4 were repeated over 7,14 and 21 days with varying numbers of implants.

The results are shown in Tables 10 and 11.

TABLE 10 0-7 days No of Days Implant Feed Weight FCR P2 mm P2 mm pigs size PST intake increase change k s k s Group 4 6 0-7 3 x 13 mg 13.95 7.53 1.85 10.2-0. 1 Smart Tab M Group 5 6 0-7 3 x 14 mg 16.77 8.00 2.10 11.0 +0.8 Smart Tab A Group 8 6-17. 18 6.03 2.85 12.2 +0.9 Sham Control 7-14 days No of Days Implant Feed Weight FCR P2 mm P2 mm pigs size PST intake increase change ks ks Group 4 6 7-14 1 x 6. 5mg 14. 59 4.53 2.69 10.7 +0.5 Smart Tab M Group 5 6 7-14 3 x 14 mg 17. 68 7.27 2.43 12.2 +1.2 Smart Tab A Group 8 6 - 18.10 6.63 2.73 12.9 +0.7 Sham Control 14-21 days No of Days Implant Feed Weight FCR P2 mm P2 mm pigs size PST intake increase change (kgs) (kgs) Group 4 6 14-21 1 x 13 mg 16.75 6.97 2.40 11.3 +0.6 Smart Tab M Group 5 6 14-21 3 x 14 mg 19.50 7.47 2.61 12.1-0. 1 Smart Tab A Group 8 6-18. 64 7.00 2.66 13.1 +0.2 Sham Control TABLE 11 0-21 days No of Days Implant Feed Weight FCR P2 mm P2 mm pigs size PST intake increase change ks ks Group 4 6 0-7 3 x 13 mg 45.30 18.27 2.51 11.3 +1.0 Smart Tab M 7-14 1 x 1. 6mg 14-21 1 x 13m Group 5 6 0-7 3 x 14 mg 53.91 22.73 2.37 12.1 +1. 8 Smart Tab A 7-14 3 x 14 mg 14-21 3x14m Group 8 6--53. 91 19.67 2.74 13.1 +1.8 Sham Control

Surprisingly, for the Smart Tab M formulation, the feed conversion ratio utilising a single 13 mg implant is approximately equivalent to the daily injection regimen.

The best fat reduction (as measured by P2) is achieved utilising the Smart Tab M formulation.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

It will also be understood that the term"comprises" (or its grammatical variants) as used in this specification is equivalent to the term"includes"and should not be taken as excluding the presence of other elements or features.