FORM 2
THE PATENTS ACT 1970
(39 of 1970)
AND
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See section 10 and rule!3)
1. TITLE OF THE INVENTION:
"Pharmaceutical Formulation"

2. APPLICANT:
(a) NAME: CIPLA LTD.
(b)NATIONALITY: Indian Company incorporated under the Indian Companies ACT, 1956
(c) ADDRESS: 289, Bellasis Road, Mumbai Central, Mumbai - 400 008, Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION:
The following specification describes the invention.

Field of Invention:
The present invention relates to a pharmaceutical formulation that is a solid dosage form comprising an immunosuppressant drug, namely sirolimus. There is also provided a process of preparing a formulation as provided by the present invention and the use thereof in the treatment and / or prevention of disorders or conditions that respond to, or are alleviated by, the administration of sirolimus.
Background & Prior Art:
Sirolimus, also known as rapamycin, is the international non-proprietary name for
the macrolide antibiotic
(3S,6R,7E,9R,10R,12R,14S,15E,17E319E,21S,23S,26R,27R,34aS) 9,10,12,13,14,21,22,23)24,25,26327,32,33,34,34a-hexadecahydro-9,27-dihydroxy-3-[(I R)-2-[(I S,3 R,4R)-4-hydroxy-3-methoxycycIohexy!]-1 -methylethy I]-10,21 -dimethoxy-6,8,12,14,20,26-hexamethyl-23,27-epoxy-3H-pyrido[2,l-c][l,4]-oxaazacyclohentriacontine-1,5,11,28,29(4H,6H,3 lH)-pentone. Sirolimus has the following structural formula


Sirolimus inhibits T-lymphocyte activation and proliferation that occurs in response to antigenic and cytokine stimulation by a mechanism that is distinct from that of other immunosuppressants. Sirolimus also inhibits antibody production. In cells, sirolimus binds to the immulophilin, FK Binding Protein-12, to generate an immunosuppressive complex. This complex has no effect on caJcineurin activity. The complex binds to and inhibits the activation of the mammalian "target of rapamycin" (nTOR), a key regulatory kinase. This inhibition suppresses cytokine-driven T-cell proliferation, inhibiting the progression from the Gi to the S phase of the cell cycle.
Sirolimus is a substrate for both cytochrome P450 IIIA4 (CYP3A4) and P-glycoprotein. Sirolimus is extensively metabolized by O-demethylation and / or hydroxy lation. Seven major metabolites, including hydroxy, demethyl and hydroxydemethyl are identifiable in whole blood. In particular, sirolimus is extensively metabolized by the CYP3A4 isoenzyme in the gut wall and liver. Therefore, absorption and the subsequent elimination of systemically absorbed sirolimus may be influenced by drugs that affect this isoenzyme. Inhibitors of CYP3A4 may decrease the metabolism of sirolimus and increase sirolimus levels, while inducers of CYP3A4 may increase the metabolism of sirolimus and decrease sirolimus levels.
Sirolimus can be produced by Streptomyces hygroscopicus and was discovered first for its properties as an antifungal agent. It adversely affects the growth of fungi such as Candida albicans and Microsporum gypseum. Sirolimus, its preparation and its antibiotic activity were first disclosed in US 3,929,992, which states that sirolimus was readily distinguished from prior art compounds of its class by its profound antifungal activity and its relatively low order of toxicity. Sirolimus is characterized in US 3,929,992 as:
being a colourless, crystalline compound with a melting point of 183°C to 185°C, after recrystallization from ether;
being soluble in ether, chloroform, acetone, methanol and dimethylformamide, very sparingly soluble in hexane and petroleum ether and substantially insoluble in water;

showing a uniform spot on thin layer plates of silica gel; having a characteristic elemental analysis of about C, 66.84%, H, 8.84%; N, 1.37%;
exhibiting the following characteristic absorption maxima in its ultraviolet absorption spectrum (95% ethanol): 267 nm (EIcm1% 417), 277 nm (E,cmi% 541) and288nm(Eicm1%416);
having a characteristic infrared absorption spectrum as shown in FIG. 1 of US 3,929,992;
having a characteristic nuclear magnetic resonance spectrum as shown in FIG. 2 of US 3,929,992;
having a minimum inhibitory concentration of 0.02 to 0.1 ug/ml against Candida albicans', and
exhibiting a LD50 (i.p., mice) of 597.3 ± 28.1 mg/kg and a LD50 (p.o., mice) of >2,500 mg/kg.
In 1977, Martel, R. R. et al reported on immunosuppressive properties of sirolimus against experimental allergic encephalitis and adjuvant arthritis in the Canadian Journal of Physiological Pharmacology, 55, 48-51 (1977). In 1989, Calne, R. Y. et al in Lancet, 1989, no. 2, p. 227, and Morris, R. E. and Meiser, B. M. in Medicinal Science Research, 1989, No. 17, P. 609-10, separately reported on the effectiveness of sirolimus in inhibiting rejection in vivo in allograft transplantation. Numerous articles have followed describing the immunosuppressive and rejection inhibiting properties of sirolimus. Sirolimus is now approved as an immunosuppressive agent indicated for the prophylaxis of organ rejection in patients receiving renal transplants and is available in tablet or solution form under the trade mark Rapamune.
Sirolimus alone (US 4,885,171), or in combination with picibanil (US 4,401,653), has also been shown to have antitumor activity. Martel et al (Can. J. Physiol. Pharmacol.

55, 48, 1977) disclosed that sirolimus is effective in the experimental allergic encephalomyelitis model, a model for multiple sclerosis; in the adjuvant arthritis model, a model for rheumatoid arthritis; and effectively inhibited the formation of IgE-like antibodies.
Sirolimus has been shown to inhibit transplantation rejection in mammals (US 5,100,899). Sirolimus, its derivatives and prodrugs, have also been shown to be useful in treating pulmonary inflammation (US 5,080,899): immunoinflammatory skin disorders, such as psoriasis (US 5,286,730); immunoinflammatory bowel disorders (US 5,286,731); ocular inflammation (US 5,387,589); hyperproliferative vascular disorders, such as restenosis (US 5,288,711); carcinomas (US 5,206,018 and US 4,885,171); and cardiac inflammatory disease (US 5,496,832); and in preventing the onset of insulin dependent diabetes mellitus (US 5,321,009). Additionally, sirolimus has been shown to be useful in treating adult T-cell leukemia / lymphoma (EP 0 525 960 Bl).
Sirolimus has poor oil and water solubility, and only a few formulations of sirolimus have proven satisfactory, in terms of providing formulations with acceptable pharmacokinetic and stability profiles.
US 5,516,770 and US 5,530,006 disclose intravenous sirolimus formulations. More specifically, US 5,516,770 discloses an aqueous, injectable sirolimus solution based on a concentrate solution of sirolimus in propylene glycol; US 5,530,006 discloses an aqueous, injectable sirolimus solution based on a concentrate solution of sirolimus in N.N-dimethylacetamide.
US 5,536,729 and US 5,559,121 disclose liquid oral sirolimus formulations. The oral solutions are based on sirolimus, surfactant and a phospholipid or lecithin solution.
EP 0 868 911 Bl and EP 0 994 697 Bl disclose sirolimus formulations for oral administration. EP 0 868 911 Bl discloses a sirolimus solid dosage unit which comprises a core and a sugar overcoat, the sugar overcoat comprising: (a) sirolimus, (b) one or more surface modifying agents, and (c) one or more sugars. EP 0 994 697 Bl discloses a sirolimus solid dosage unit which comprises a core and a sugar overcoat, the sugar

overcoat comprising: (a) sirolimus, (b) one or more sugars, and (c) one or more binders, provided the overcoat does not contain one or more surface modifying agents.
WO 01/37808 Al discloses solid pharmaceutical formulations for improved delivery of a wide variety of pharmaceutical active ingredients contained therein or separately administered. In one embodiment, the solid pharmaceutical composition includes a solid carrier, the solid carrier including a substrate and an encapsulation coat on the substrate. The encapsulation coat can include different combinations of pharmaceutical active ingredients, hydrophilic surfactants, lipophilic surfactants and triglycerides. In another embodiment, the solid pharmaceutical composition includes a solid carrier, the solid carrier being formed of different combinations of pharmaceutical active ingredients, hydrophilic surfactants, lipophilic surfactants and triglycerides. Sirolimus is identified in the extensive listing of hydrophobic active ingredients suitable for administration by the compositions of WO 01/37808 Al. Furthermore, Example 21 of WO 01/37808 Al specifically discloses a sirolimus composition, which comprises sirolimus in combination with surfactants and triglyceride, namely PEG-40 stearate, PEG-150 stearate and miglyol 812.
EP 1 938 800 Al discloses a nanodispersion comprising sirolimus and surface modifiers, wherein the effective average particle size of sirolimus is above 400nm. There is also disclosed a corresponding pharmaceutical composition including the nanodispersion. More specifically, a composition according to EP 1 938 800 Al comprises a) a nanodispersion comprising sirolimus and surface modifiers b) an inert core coated with said nanodispersion, wherein the effective average particle size of sirolimus is more than 400nm.
US 2009/0068266 A1 discloses sirolimus particles having dgo value of from about 2um to about 10^m. There is also disclosed a corresponding pharmaceutical composition including the sirolimus particles. More specifically, a composition according to US 2009/0068266 Al comprises: a) a dispersion of sirolimus particles and one or more pharmaceutically acceptable excipients in a vehicle; b) an inert core coated with said dispersion; and c) optionally, coating the drug coated cores to obtain the desired dosage form; wherein the sirolimus particles have d90 value of from about 2u.m to about 10um.

As hereinbefore mentioned, sirolimus is now approved and commercially available under the trade mark Rapamune as an immunosuppressive agent. For oral administration, sirolimus is currently formulated and marketed as an oral solution containing 1 mg/ml sirolimus, and is also available in tablet form as a white, triangular-shaped tablet containing 1 mg sirolimus or as a yellow to beige triangular-shaped tablet containing 2 mg sirolimus. Rapamune oral solutions contain sirolimus and as inactive ingredients polysorbate 80 and a standardized phosphatidylcholine concentrate, available under the trade mark Phosal 50 PG (which comprises phosphatidylcholine, propylene glycol, mono- and di-glycerides, ethanol, soy fatty acids, and ascorbyl palmitate). Rapamune tablets contain sirolimus in a sugar overcoat and the inactive ingredients present are macrogol, glyceryl monooleate, pharmaceutical glaze, anhydrous calcium sulphate, microcrystalline cellulose, sucrose, titanium dioxide, poloxamer 188, a-tocopherol, povidone and carnauba wax. In addition, 2mg Rapamune tablets contain iron oxides as colouring materials to distinguish them from the Img (white) tablets.
It has been found, however, that a problem associated with the above mentioned prior art and commercially available Rapamune tablets is that degradation of the active sirolimus often occurs, generally as a result of exposure of sirolimus to prolonged elevated temperatures that are employed in the tablet coating process of applying the sirolimus containing sugar overcoat to the inert core. There is a need, therefore, to be able to provide a sirolimus solid dosage form having acceptable pharmacokinetic profiles, and which solid dosage form could be provided substantially free of sirolimus degradation products. There is also a need for an improved manufacturing process for a sirolimus solid dosage form, which would avoid the use of operating conditions that might induce or facilitate the formation of sirolimus degradation products, and as such would manufacture a solid dosage form comprising sirolimus in such a way so as to obviate the occurrence of sirolimus degradation products in the solid dosage form.
Object of the Invention:
The object of the present invention is to provide a solid dosage form of sirolimus which is substantially free of sirolimus degradation products.

Another object of the present invention is to provide an improved process of manufacturing the solid dosage form of sirolimus.
Yet another object of the present invention is to provide a sirolimus solid dosage form having improved pharmacokinetic profiles.
Summary of the Invention:
In one aspect of the present invention, there is provided a solid dosage form comprising (i) a core comprising a therapeutically effective amount of sirolimus, and (ii) at least one sugar overcoat.
In another aspect of the present invention, there is provided a process of substantially preventing the formation, in a solid dosage form, of degradation products associated with sirolimus, which process comprises (i) providing a core comprising a therapeutically effective amount of sirolimus, and (ii) providing at least one sugar overcoat on said core.
In a further aspect of the present invention, there is provided a process of preparing a solid dosage, which process comprises (i) providing a core comprising a therapeutically effective amount of sirolimus.. and (ii) providing at least one sugar overcoat on said core.
In a still another aspect of the present invention, there is provided a solid dosage form for use in treating disorders or conditions that respond to, or are prevented, ameliorated or eliminated by, the administration of sirolimus.
In a still further aspect of the present invention, there is provided a solid dosage form for use in treating and / or prophylaxis of organ rejection.
Detailed description:
The above problems are now alleviated by the present invention as follows.
More particularly, there is now provided by the present invention a pharmaceutical solid dosage form comprising (i) a core comprising a therapeutically effective amount of sirolimus, and (ii) at least one sugar overcoat. By including sirolimus

in the core of a solid dosage form as provided by the invention, as opposed to the sugar overcoat, the inventors have thus found that degradation of the sirolimus during manufacturing of the solid dosage form is substantially avoided and that a solid dosage form with improved sirolimus stability is achieved.
As used herein, the term "therapeutically effective amount" means an amount of sirolimus which is capable of treating conditions in a human patient substantially as hereinafter described in greater detail. More particularly, the term "therapeutically effective amount" means an amount of sirolimus which is capable of treating disorders or conditions that respond to, or are alleviated by, the administration of sirolimus substantially as hereinafter described in greater detail.
Within the scope of the present invention, reference to "sirolimus" as used herein can denote any physical form, such as crystalline or amorphous form, any possible polymorphs, in particular known polymorph forms I or II or a polymorphous mixture thereof, any possible solvate, including a hydrate or anhydrate, or any suitable complex. It is also envisaged that any therapeutically active and pharmaceutically acceptable analogue of sirolimus could be employed in the context of the present invention, such as pharmaceutically acceptable salts, and prodrugs thereof. Additionally, sirolimus is chiral (15 stereogenic centres) and reference to sirolimus as used herein can denote any isomeric form. For example, sirolimus can be present in any of known isomeric forms A, B or C. The preparation of sirolimus to be used in a solid dosage form according to the present invention can be carried out by following any known suitable preparation process, for example such as culturing Streptomyces hygroscopicus as disclosed in US 3,929,992, substantially as hereinbefore described. Preferably, however, preparation of sirolimus is such so as to provide a single defined stereoisomer thereof in the solid state.
In a particularly preferred embodiment a solid dosage form as provided by the present invention comprises a tablet and sirolimus is generally present in the core together with one or more pharmaceutically acceptable carriers, diluents or excipients thereof. By "pharmaceutically acceptable" it is meant that the carrier, diluent or excipient must be compatible with sirolimus as employed according to the present invention, and not be deleterious to a recipient thereof.

Examples of suitable pharmaceutically acceptable carriers, diluents, fillers or excipients for use in the core of a solid dosage form as provided by the present invention include lactose (for example, spray-dried lactose, a-lactose, p-Iactose, lactose available under the trade mark Tabletose, various grades of lactose available under the trade mark Pharmatose or other commercially available forms of lactose), lactitol, saccharose, sorbitol, mannitol, dextrates, dextrins, dextrose, maltodextrin, croscarmellose sodium, microcrystalline cellulose (for example, microcrystalline cellulose available under the trade mark Avicel), hydroxypropylcellulose, L-hydroxypropylcellulose (low substituted), hydroxypropyl methylcellulose (HPMC), methylcellulose polymers (such as. for example, Methocel A, Methocel A4C, Methocel A15C, Methocel A4M), hydroxy ethyl cellulose, sodium carboxymethylcellulose, carboxym ethylene, carboxymethylhydroxy ethyl cellulose and other cellulose derivatives, starches or modified starches (including potato starch, maize starch and rice starch), and the like. It is particularly preferred that at least lactose and microcrystalline cellulose are present in the core as pharmaceutically acceptable excipients for use with sirolimus in a solid dosage form according to the present invention. In particular, it is preferred that lactose and / or microcrystalline cellulose are present in a dry mix component of the core as described hereinafter in greater detail.
The amount of diluent may be present in the range upto about 90 % by weight of the solid dosage form preferably in the range of about 2 % to about 70 % by weight of the solid dosage form.
Typically glidants and lubricants may also be included in the core of a solid dosage form as provided by the present invention. Examples include stearic acid and pharmaceutically acceptable salts or esters thereof (for example, magnesium stearate, calcium stearate, sodium stearyl fumarate or other metallic stearate), talc, waxes (for example, microcrystalline waxes) and glycerides, light mineral oil, PEG, silica acid or a derivative or salt thereof (for example, silicates, silicon dioxide, colloidal silicon dioxide and polymers thereof, magnesium aluminosilicate and / or magnesium aluminometasilicate), sucrose ester of fatty acids, hydrogenated vegetable oils (for example, hydrogenated castor oil), or mixtures thereof or any other suitable lubricant. It is particularly preferred that a lubricant present in a solid dosage form as provided by the

present invention is selected from the group consisting of magnesium stearate and silicon dioxide, such as silicon dioxide commercially available under the trade mark Aerosil.
The amount of lubricant may be present in the range upto about 5% by weight of
the solid dosage form, preferably in the range of about 0.25% to about 2% by weight of
the solid dosage form.
Suitably one or more binders are also present in the core of a solid dosage form as provided by the present invention and specific examples of suitable binders are, for example, polyvinyl pyrrolidone (also known as povidone), acacia, alginic acid, agar, calcium carrageenan, cellulose derivatives such as ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, sodium carboxymethylcellulose, dextrin, gelatin, gum arabic, guar gum, tragacanth, sodium alginate, or mixtures thereof or any other suitable binder. Povidone is particularly preferred for use as a binder in the core of a solid dosage form according to the present invention.
The amount of binder may be present in the range from about 10% by weight of the solid dosage form, preferably in the range of about 2% to about 6% by weight of the solid dosage form.
Suitable disintegrants may also be present in the core of a solid dosage form, according to the present invention, which includes, but are not limited to hydroxylpropyl cellulose (HPC), low density HPC, carboxymethylcellulose (CMC), sodium CMC, calcium CMC, croscarmellose sodium; starches exemplified under examples of fillers and also carboxymethyl starch, hydroxylpropyl starch, modified starch; crystalline cellulose, sodium starch glycolate; alginic acid or a salt thereof, such as sodium alginate or their equivalents and any combination thereof. The preferable disintegrant is croscarmellose sodium.
The amount of disintegrant may be present in the range of upto about 20% by weight of the solid dosage form, preferably about 2% to about 10% by weight of the solid dosage form.
Sirolimus suffers from poor oral bioavailability due, in large part, to extensive presystemic metabolism by cytochrome P450 IIIA4 (CYP3A4) substantially as

hereinbefore described. In order to improve the bioavailability of sirolimus as provided
in a solid dosage form according to the present invention, it is preferred that sirolimus is
present as a nanocrystal colloidal dispersion, hereinafter referred to as nanodispersion. In
this way, the sirolimus particles are reduced to nanometer dimensions using techniques
well known in the art, substantially as hereinafter described in greater detail. Preferably
the nanodispersion further comprises one or more stabilizing agents, including, but not
limited to polyoxyethylenated esters of sorbitan (for example, polysorbate 20, polysorbate
60 & polysorbate 80), sorbitan fatty acid esters (for example, Span 20, Span 40, Span 60
& Span 85), polyoxyethylene-polyoxypropylene block copolymers, sodium lauryl
sulphate, propylene glycols and fatty acid esters of propylene glycol (for example,
propylene glycol monocaprylate, propylene glycol monolaurate); oleoyl macrogol
glycerides (for example, Labrafil); Caprylocaproyl macrogol glycerides (e.g. Labrasol);
polyethylene glycols (for example, PEG 600, PEG 6000) or combinations thereof and a
particularly preferred stabilizing agent can be one or more of the commercially available
polyoxyethylene-polyoxypropylene block copolymers generically known as
"poloxamers". Poloxamers have the polymeric formula:
HO(CH2CH20)a(CH(CH3)CH20H)b(CH2CH20)cH where generally b is at least 15 and (CH2CH2O)a + c is varied from about 20 to 90% by weight. Poloxamer 188 is particularly preferred as a stabilizing agent in a solid dosage form according to the present invention, for which in the above formula a = 75, b = 30 and c = 75.
It is also preferred that the core of a solid dosage form according to the present invention further comprises one or more antioxidants, which are suitably present in the sirolimus nanodispersion. Suitable antioxidants can include, for example, ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, hypophosphorous acid, monothioglycerol, potassium metabisulfite, propyl gallate, sodium formaldehylde sulfoxylate, sodium metabi sulfite, sodium thiosulfate, sulfur dioxide, tocopherol, a-tocopherol, tocopherol acetate, tocopherol hemisuccinate, or other tocopherol derivatives, or mixtures thereof, or any other suitable antioxidant. Typically, an antioxidant used in a solid dosage form according to the present invention is a tocopherol, and a-tocopherol is particularly preferred.

The amount of antioxidant may be present in the range of about 0.001 to 1.5 % by weight of the solid dosage form, preferably about 0.01% to about 1% by weight of the solid dosage form.
A sugar overcoat as used in a solid dosage form according to the present invention includes a sugar based coating applied directly or indirectly to the sirolimus containing core. Preferably the sugar overcoat is substantially free of sirolimus. The sugar used in the overcoat may comprise one or more of lactose, mannitol, sorbitol, sucrose and mixtures thereof, with the use of sucrose being particularly preferred in a solid dosage form according to the present invention. Typically, the sugar overcoat further comprises one or more binders so as to advantageously increase strength of the sugar overcoat and / or to increase bonding strength between the sirolimus containing core and the sugar overcoat when the latter is directly applied to the former. Substantially as hereinbefore described, suitable binders are, for example, povidone, acacia, alginic acid, agar, calcium carrageenan, sodium carboxymethylcellulose, dextrin, gelatin, guar gum, or any other suitable binder, with the use of povidone being particularly preferred for use as a binder in the sugar overcoat. The use of a sugar overcoat in the present invention in this way can provide a beneficial protective barrier around the sirolimus containing core. The coating is preferably substantially water soluble and dissolves after swallowing of the solid dosage form according to the present invention by a patient.
In one embodiment of the present invention, the solid dosage form further comprises at least one intermediate seal coat between the core and the sugar overcoat. This intermediate seal coat can advantageously further protect the sirolimus present in the core, for example by protecting against moisture introduced in the sugar coating process, and in this way can further assist in substantially preventing, or at least reducing, degradation of sirolimus present in the core of the solid dosage form. Preferably the intermediate seal coat comprises one or more waterproofing substances typically applied to the core in an alcoholic carrier. Typically, the waterproofing substance can comprise a wax or other suitable pharmaceutically acceptable material with appropriate waterproofing properties.

Waxes suitable for use in an intermediate seal coat to be employed according to the present invention are typically water-resistant materials made up of various substances, including hydrocarbons (n-alkanes), ketones, diketones, primary and secondary alcohols, aldehydes, alkanoic acids, terpenes (squalene) and monoesters, all with long carbon chains (from 12-38 carbon atoms), which are solid over a wide temperature range. More commonly, waxes are esters of a monohydric alcohol and a long chain acid. Preferably a wax suitable for use in a formulation according to the present invention can be selected from the group consisting of beeswax, shellac, carnauba wax, spermaceti, lanolin, jojoba oil, candellila wax, ozocerite, opaglos 6000 P and the like. The use of shellac in an alcoholic carrier, such as isopropyl alcohol, is particularly preferred in an intermediate seal coat employed in a solid dosage form according to the present invention.
The combination of the protective properties provided by the above mentioned preferred use of an intermediate seal coat in a solid dosage form according to the present invention, and the inclusion of sirolimus in the core of the solid dosage form (compared to inclusion in the sugar overcoat of the prior art formulations, for example as described in EP 0 868 911 Bl and EP 0 994 697 Bl), is particularly beneficial in obviating formation of thermal degradation products of sirolimus. A solid dosage form according to the present invention is, therefore, associated with less impurities and / or degradants compared with prior art formulations and this is advantageous in avoiding variable contamination levels and unpredictable bioavailability of sirolimus that can often be associated with prior art dosage forms.
There is further provided by the present invention a pharmaceutical solid dosage form comprising (i) a core comprising a therapeutically effective amount of sirolimus, (ii) at least one sugar overcoat, and preferably also (iii) at least one intermediate seal coat between the core and the overcoat, wherein the solid dosage form is substantially free of sirolimus degradation products. Typically, the presence of such sirolimus degradation products as avoided by the present invention comprises thermal degradation products that generally occur further to exposure of sirolimus to elevated temperatures. The wording "substantially free of degradation products" as used herein denotes the presence of minimal impurities, such as the above mentioned thermal degradation products of

sirolimus, or at least denotes the presence of impurities in an amount within or below the pharmaceutically defined or recognized level of impurities acceptable for sirolimus and sirolimus containing formulations.
, There is also provided by the present invention a process of substantially preventing the formation, in a solid dosage form, of degradation products associated with sirolimus, in particular thermal degradation products associated with exposure of a sirolimus to elevated temperatures, which process comprises (i) providing a core comprising a therapeutically effective amount of sirolimus, (ii) providing at least one sugar overcoat (directly or indirectly) on said core, and preferably also (iii) providing at least one intermediate seal coat between the core and the overcoat. In this way. the overcoat of the solid dosage form is preferably substantially free of sirolimus.
There is also provided by the present invention a process of preparing a solid dosage form substantially as hereinbefore described, which process comprises (i) providing a core comprising a therapeutically effective amount of sirolimus, (ii) providing at least one sugar overcoat (directly or indirectly) on said core, and preferably also (iii) providing at least one intermediate seal coat between the core and the overcoat. Suitably, a process according to the present invention comprises preparing a tablet.
The core of the solid dosage form is typically prepared by providing a dry mix component and a binder component, granulating the dry mix component and the binder component, suitably in a fluid bed processor, followed by lubrication and compression to form the desired core. Optionally, an intermediate seal coat is applied to the thus formed core of the solid dosage form. The sugar overcoat is then applied directly or indirectly to the core of the solid dosage form.
The dry mix component is preferably prepared by dry mixing suitable pharmaceutically acceptable carriers, diluents or excipients for use in the core of a solid dosage form as provided by the present invention substantially as hereinbefore described. It is particularly preferred that at least lactose and microcrystalline cellulose are dry mixed to provide a dry mix component of the core of the solid dosage form according to the present invention.

It is also preferred that a process according to the present invention further comprises preparing a nanodispersion comprising sirolimus. Typically, the nanodispersion is prepared using known wet milling techniques, which are particularly suited to preparing particles reduced to nanometer dimensions and also provide the further advantage in reducing particle size of drugs such as immunosuppressants, wherein it is beneficial to control the dust produced. Various mills are available for wet milling, such as ball mill, an attritor mill, a vibratory mill, and media mills, such as a sand mill and a bead mill. The grinding media used in wet milling can include zirconium oxide, such as 95% ZrO stabilized with magnesia, zirconium silicate, and glass grinding media, stainless steel, titania, alumina, and 95% ZrO stabilized with yttrium. Preferably a ball milling process is employed in a process according to the present invention.
It is particularly preferred in a process according to the present invention to carry out the above milling in the presence of one or more stabilizing agents, so that the resulting nanodispersion comprises nanoparticles of sirolimus together with the one or more stabilizing agents. Substantially as hereinbefore described, a particularly preferred stabilizing agent can be one or more of the commercially available polyoxyethylene-polyoxypropyJene block copolymers generically known as "poloxamers". Poloxamer ] 88 is particularly preferred as a stabilizing agent to be used in the preparation of the nanodispersion employed in a process according to the present invention.
It is also preferred that a process according to the present invention further comprises including one or more antioxidants in the above described nanodispersion. Suitable antioxidants can include, for example, ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, hypophosphorous acid, monothioglycerol, potassium metabisulfite, propyl gallate, sodium formaldehylde sulfoxylate, sodium metabisulfite, sodium thiosulfate, sulfur dioxide, tocopherol, a-tocopherol, tocopherol acetate, tocopherol hemisuccinate, or other tocopherol derivatives, or any other suitable antioxidant. Substantially as hereinbefore described, a preferred antioxidant to be used in a process according to the present invention is a tocopherol, and a-tocopherol is particularly preferred.

It is also preferred that a process according to the present invention further comprises including one or more binders in the above described nanodispersion. Suitable binders can include, for example, povidone, acacia, alginic acid, agar, calcium carrageenan, sodium carboxymethylcellulose, dextrin, gelatin, guar gum, or mixtures thereof, or any other suitable binder. Povidone is particularly preferred for use as a binder in a nanodispersion as prepared in a process according to the present invention.
The thus formed nanodispersion (including nanoparticles of sirolimus, one or more stabilizing agents, one or more antioxidants and one or more binders) provides the above described binder component of the core of a solid dosage form according to the present invention. The dry mix component and binder component are then granulated using techniques and apparatus well known in the art, for example a fluid bed processor, to form granulates. However, it will also be apparent to the skilled artisan that various granulation techniques may be adopted to achieve the granules of sirolimus, which techniques comprises dry granulation, slugging, solvent evaporation, extrusion, hot melt extrusion, hot melt granulation, extrusion-spheronization, spray drying and the like.
The resulting granulates are preferably then blended and lubricated with a suitable glidant and / or lubricant. It is particularly preferred that magnesium stearate and silicon dioxide, such as silicon dioxide commercially available under the trade mark Aerosii, are used to lubricate the granulates prepared in a process according to the present invention. The lubricated granulates are then compressed to form the core of a solid dosage form according to the present invention.
Suitably a sugar overcoat applied in a process according to the present invention includes a sugar based coating applied directly or indirectly to the sirolimus containing core. The sugar used in the overcoat may comprise one or more of lactose, mannitol, sorbitol, sucrose, dextrose and mixtures thereof, with the use of sucrose being particularly preferred. Typically, a process according to the present invention comprises including one or more binders in the sugar overcoat, with a preferred binder being povidone substantially as hereinbefore described.

In a particularly preferred embodiment of the present invention, a process of the invention further comprises providing at least one intermediate seal coat between the core and the sugar overcoat. This intermediate seal coat preferably comprises one or more waterproofing substances typically applied to the core in an alcoholic carrier, and a preferred seal coat comprises shellac in an alcoholic carrier, such as isopropyl alcohol, substantially as herein before described. Typically, the intermediate seal coat can be poured or sprayed onto the cores of the solid dosage form as prepared in accordance with the present invention, the cores suitably rotating in coating pans or other suitable manufacturing apparatus. Suitably, warm air can be introduced into a coating pan or other apparatus during the coating of the intermediate seal coat, which can be beneficial to hasten drying and to prevent the solid dosage forms from sticking together.
One or more coats of a sugar overcoat are preferably applied to the above described intermediate seal coat in the above preferred embodiment of a process according to the present invention; alternatively, one or more coats of a sugar overcoat are applied directly to the core of the solid dosage form in the process according to the invention. The presence of one or more binders in the sugar overcoat enhances application thereof to either the intermediate seal coat or the core of the solid dosage form. The thus applied one or more coats of the sugar overcoat are suitably at least partially dried in a process according to the present invention and can be sprinkled with a dusting powder, such as talc or the like. The thus coated cores are then suitably dried further to provide the final solid dosage forms of the invention.
There is further provided by the present invention a method of treating disorders or conditions that respond to, or are prevented, ameliorated or eliminated by, the administration of sirolimus, which method comprises administering to a human patient suffering from or susceptible to such a disorder or condition in a solid dosage form according to the present invention substantially as hereinbefore described. As hereinbefore described with reference to the prior art, in addition to the main therapeutic utility of sirolimus as an immunosuppressant, sirolimus has utility in other therapeutic treatments. For example, sirolimus has been shown to possess immunosuppressive, anti-rejection, antifungal and anti-inflammatory activity in vivo and to inhibit thymocyte proliferation in vitro. Sirolimus thus has utility in -the treatment or inhibition of

transplantation rejection such as kidney, heart, liver, lung, bone marrow, pancreas (islet cells), cornea, small bowel, and skin allografts, and heart valve xenografts; in the treatment or inhibition of graft vs. host disease; in the treatment or inhibition of autoimmune diseases such as lupus, rheumatoid arthritis, diabetes mellitus, myasthenia gravis, and multiple sclerosis; and diseases of inflammation such as psoriasis, dermatitis, eczema, seborrhea, inflammatory bowel disease, pulmonary inflammation (including asthma, chronic obstructive pulmonary disease, emphysema, acute respiratory distress syndrome, bronchitis, and the like), and eye uveitis. Sirolimus has also been shown to have antitumor and anti-proliferative activities and thus has utility for the treatment of solid tumors, including sarcomas and carcinomas, such as astrocytomas, prostate cancer, breast cancer, small cell lung cancer, and ovarian cancer; adult T-cell leukemia/Iymphoma; and hyperproliferative vascular diseases such as restenosis and atherosclerosis. Reference herein to "disorders or conditions that respond to, or are prevented, ameliorated or eliminated by, the administration of sirolimus" can, therefore, include reference to any one of the above mentioned disorders or conditions, or any other disorders or conditions known in the art to be susceptible to treatment by sirolimus.
In particular, however, the present invention provides a method for the prophylaxis of organ rejection, particularly in adult patients at low to moderate immunological risk, and even more particularly in such patients receiving a renal transplant, which method comprises administering to a human patient susceptible to such organ rejection, a solid dosage form according to the present invention substantially as hereinbefore described. The term "treatment" as used herein encompasses both prophylaxis, and the treatment of established organ rejection, but as indicated above prophylaxis of organ rejection is a particularly important aspect of the present invention. The "treatment" can also include maintenance therapy.
Suitably, the above mentioned prophylactic treatment involves for 2 to 3 months post-transplantation, administration of a solid dosage form according to the present invention that typically provides an initial 6 mg oral loading dose of sirolimus, administered as soon as possible after transplantation, suitably followed by 2 mg once daily. The sirolimus dose should preferably then be individualised, to obtain whole blood trough levels of typically 4 to 12 ng/ml. Suitably, sirolimus therapy should be optimised

with a tapering regimen of steroids and cyclosporine. Suggested cyclosporine trough concentration ranges for the first 2-3 months after transplantation are typically 150-400 ng/ml.
Suitably, the above mentioned maintenance therapy involves cyclosporine administration that should be progressively discontinued over 4 to 8 weeks and administration of a solid dosage form according to the present invention that provides sirolimus dosing to obtain whole blood trough levels of typically 12 to 20 ng/ml. Sirolimus can also be advantageously administered with corticosteroids in such maintenance therapy.
There is further provided by the present invention a solid dosage form substantially as hereinbefore described, for use in treating disorders or conditions that respond to, or are prevented, ameliorated or eliminated by, the administration of sirolimus. More preferably, there is further provided by the present invention a solid dosage form substantially as hereinbefore described, for use in treating, preferably as prophylaxis, organ rejection, particularly in adult patients at low to moderate immunological risk, and even more particularly in such patients receiving a renal transplant.
It can be appreciated from the above mentioned method of treatment description in accordance with the present invention that it can be beneficial to provide, recommend or label, a solid dosage form according to the present invention for administration with one or more other therapeutically active compounds. In particular, a solid dosage form according to the present invention can advantageously be administered, or recommended or labeled for use, in combination with cyclosporine and / or one or more corticosteroids.
There is further provided by the present invention, therefore, a solid dosage form substantially as hereinbefore described, for use in treating organ rejection in combination with cyclosporine.

There is still further provided by the present invention, therefore, a solid dosage form substantially as hereinbefore described, for use in treating organ rejection in combination with one or more corticosteroids.
There is still further provided by the present invention a product containing a solid dosage form substantially as hereinbefore described, and a cyclosporine dosage form, as a combined preparation, for separate or sequential use in treating organ rejection.
There is still further provided by the present invention a product containing a solid dosage form substantially as hereinbefore described, and one or more corticosteroids, as a combined preparation, for separate or sequential use in treating organ rejection.
There is still further provided by the present invention a product containing (i) a solid dosage form substantially as hereinbefore described, (ii) a cyclosporine dosage form, and (iii) one or more corticosteroids, as a combined preparation, for separate or sequential use in treating organ rejection.
It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope of the invention. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be falling within the scope of the invention, which is limited only by the scope and interpretation of the following claims.
The present invention is now further illustrated by, but not limited to, the following Example.

Process:
Sirolimus was ball milled with PolOxamer 188 solution to form a nanodispersion. Povidone and a- Tocopherol were added and solubilized in the nanodispersion with stirring.
Lactose, PEG 8000 and microcrystalline cellulose were dry mixed.
The thus formed nanodispersion and the dry mix were granulated using a fluidized bed processor. The resulting granules were then blended and lubricated with Aerosil and magnesium stearate. The lubricated granules were then compressed into the tablet cores.
Finally, the seal coat was applied on the tablet cores followed by sugar coating.