NZ767015B2 - Colonic drug delivery formulation - Google Patents

Abstract

Disclosed is a delayed release drug formulation for delivery of a drug to the colon comprising a particle with a core and a coating for the core, the core comprising a drug and the coating comprising a single layer of a mixture of a first material which is susceptible to attack by colonic bacteria and a second material which is a film-forming polymeric material having a pH threshold at about pH 6.5 or above, wherein the first material is chitosan; and wherein the pH threshold of the second material is the pH below which it is insoluble and at or above which it is soluble. nd a second material which is a film-forming polymeric material having a pH threshold at about pH 6.5 or above, wherein the first material is chitosan; and wherein the pH threshold of the second material is the pH below which it is insoluble and at or above which it is soluble.

Description

COLONIC DRUG DELIVERY FORMULATION This application is a divisional of New Zealand patent application 748404, itself a onal of New Zealand patent ation 730261, itself a divisional of New Zealand patent application 712908, itself a divisional of New Zealand patent application 622939, itself a divisional of New Zealand patent application 602907, itself a divisional of New Zealand patent application 572760, which is the national phase entry in New Zealand of PCT international application , filed 13 April 2007. The entire content of each of these applications is incorporated by nce herein.

The present invention relates to a delayed e formulation with a core sing a drug and a delayed release coating. In ular, it relates to a delayed release formulation for a drug for delivering to the colon.

The targeting of drugs to the colon can be utilised as a means of achieving local y or systemic treatment. The colon is susceptible to a number of disease states, including inflammatory bowel disease, irritable bowel syndrome, constipation, diarrhoea, infection and carcinoma. In such conditions, drug targeting to the colon would maximise the therapeutic effectiveness of the treatment. The colon can also be utilised as a portal for the entry of drugs into the systemic circulation. Various formulations have been developed for colonic drug delivery, ing pro-drugs as well as ated dosage forms, with the latter being more popular since the concept once proved can be applied to other drugs.

The higher bacterial population in the colon has also been exploited in developing colonic drug delivery dosage forms through the use, as carrier materials, of naturally occurring complex polysaccharides that constitute substrates for the numerous s of the resident colonic bacteria. These materials are able to pass through the upper gastrointestinal regions intact but are digested upon entry into the colon. Those studied so far include amorphous amylose, pectin, an and galactomannan.

Amorphous amylose is resistant to digestion by the enzymes of the upper gastrointestinal tract. It is, however, fermented in the colon by α-amylase enzymes ed by over half of the 400 bacteria species resident in the colon.

One major tion of using polysaccharides in this bacterial enzyme approach to colonic drug ry is that materials used are of food grade and so would be safe for use in humans. They are usually applied as gs or incorporated in the core al as a matrix carrier, and their digestion on entry into the colon by the colonic bacterial enzymes leads to the release of the drug load. An e of such a ation, which employs an amylose coating, is disclosed in EP–A-0343993 (BTG International Limited).

A major limitation with these naturally occurring materials, however, is that they swell excessively in aqueous media leading to leaching of the drug load in the upper gastrointestinal regions. To circumvent this problem, they have been utilised in a mixture with impermeable materials (e.g. amorphous amylose mixed with the water- ble polymer ethylcellulose). However, the problem with such modifications/mixtures is in finding the right balance between hydrophobicity and hydrophilicity that would prevent rtune drug release in the upper gastrointestinal regions, but which would also at the same time permit enzyme access to the polysaccharide substrate and ensure drug release at an adequate rate in the colon.

An attempt to solve the problem of the excessive swelling of amylose is sed in 502032 (British Technology Group Ltd). This employs an outer coating comprising a film forming cellulose or acrylate polymer material and amorphous e for a tablet comprising an active compound. One embodiment has the active compound coated first with an inner coating of amylose and then a separate outer g of the ose or acrylate polymer material. Another embodiment has an outer coating which is an admixture of amylose and a cellulose or acrylate polymer. The reference makes clear that the degradation of the cellulose alsin vivo is, in general, not pH dependent and it is preferred that this is also true for the acrylate materials. Every example disclosed in the reference is of a pH independent cellulosic or acrylate polymer.

An article in Journal of Controlled Release (Milojevicet al; 38; (1996); 75-84) reports the results of investigations concerning the incorporation of a range of insoluble polymers into an amylose coating in order to control amylose swelling. A range of cellulose and acrylate based co-polymers are assessed, and a cially available ethyl ose el®) is found to control the swelling most effectively.

Another single layer coating that is investigated is a mixture of amylose and two pH independent acrylic polymers, namely Eudragit® RS and RL, but this coating is found not to give such effective results. A pH dependent soluble coating of Eudragit® L100 is employed but only in a multi-layer system comprising a bioactive coated with an inner coating of amylose and then an outer coating of Eudragit® L100.

A further amylose-based coating composition is disclosed in WO–A-99/21536 (BTG International Limited). The coating composition comprises a mixture of amylose and a water insoluble film-forming polymer which is formed from a water-insoluble cellulosic or acrylate polymer material. As with EP–A-0502032, it is made clear that degradation of the cellulose materials in vivo is, in general, not pH dependent and it is preferred that this is also true for the acrylate materials. It would appear that the PCT specification contains a typographical error, e it goes on to say that a preferred form of te material is git L whose degradation is independent of pH". It is believed that this should refer to "Eudragit® RL" whose ation is indeed independent of pH. It cannot be intended to refer to Eudragit® L, as the ation of this polymer is pH ent.

WO–A-99/25325 (BTG International Limited) also discloses a delayed release coating comprising amylose and (preferably) ethyl cellulose or atively an te polymer the degradation of which is independent of pH. The coating composition also includes a plasticiser and the method finds particular application in the preparation of dosage forms comprising active materials that are unstable at temperatures in excess of 60°C, as the composition is formed at lower temperatures than this. It should be noted that this reference also es the typographical error relating to Eudragit® L described above.

The Inventors note that the formulations disclosed in the BTG references discussed above use in the coatings amylose rather than starch and that release from the formulations is sustained along a portion of the gut.

WO–A-03/068196 (Alizyme Theraputics Ltd) discloses a specific delayed release coating for the bioactive prednisolone sodium metasulphobenzoate comprising glassy amylose, ethyl cellulose and dibutyl sebacate.

The use of polysaccharides other than amorphous amylose in a delayed release coating is disclosed in GB–A-2367002 (British Sugar PLC). Examples include guar gum, karaya gum, gum tragacanth and xanthan gum. Microparticles of these polysaccharides are dispersed in a insoluble film-forming polymer matrix formed for example from a cellulose derivative, an c polymer or a .

WO-A-01/76562 (Tampereen Patenttitoimisto Oy) discloses a peroral pharmaceutical formulation ning a drug and a an (a polysaccharide obtained from chitin) for controlling its release. The drug and the chitosan are mixed into a homogeneous mechanical powder mixture which is granulated and then optionally tabletised. The ation may be performed with an enteric polymer (such as a coploymer of methacrylic acid) or the granules may be provided with a porous enteric coating.

WO-A-2004/052339 (Salvona LLC) discloses a pH dependent drug release system which is a free-flowing powder of solid hobic nano-spheres comprising a drug encapsulated in a pH-sensitive micro-sphere. The nano-spheres are formed from the drug in combination with a wax material, and the pH-sensitive micro-sphere formed from a pH-sensitive polymer (such as a Eudragit® r) in combination with a water-sensitive material such as a polysaccharide. The present applicant believes however that the very small particle sizes involved in this reference would not in practice delay the e of the bioactive core, beyond the stomach or duodenum.

An article in the European Journal of Pharmaceutical Sciences riet al; 28; March 2006; 307-314) reports the results of investigations into the use of certain thacrylate rs to, inter alia, control the swelling of inulin. The polymethacrylate polymers tested were it® RS; Eudragit® RL; 1 : 1 mixtures of Eudragit® RS and Eudragit® RL; Eudragit® FS; and 1 : 1 es of Eudragit® RS and Eudragit® S. Results indicated that polymer compositions comprising ned release polymethacrylates (Eudragit® RS and Eudragit® RL; pH insensitive polymers) with inulin displayed swelling profiles indicating a ility for use as coatings for colonic release. However, other results indicated that polymer compositions sing inulin with either Eudragit® FS or 1 : 1 mixtures of Eudragit® RS and Eudragit® S (pH dependent polymers) would not be suitable for such use due to undesirable swelling profiles.

US-A-5422121 (Röhm GmbH) discloses an oral dosage form containing at least one active ingredient ed within a shell material which comprises a polysaccharide that decomposes in the colon. The shell material contains a filmforming polymer in admixture with the polysaccharide. The ratio by weight of polysaccharide to film forming polymer is from 1 : 2 to 5 : 1, preferably from 1 : 1 to 4 : 1. Examples of le polysaccharides include those polysaccharides that are decomposable by glycosidic enzymes. Polysaccharides containing considerable amounts, preferably about 20 wt % to 100 wt %, of galactose and e units are particularly suitable with locust bean gum and guar gum being preferred. Preferred film-forming polymers include te polymers that are pH ndent (insoluble throughout the GI tract) and pH dependent (insoluble in stomach juice but soluble in intestinal juice at pH 5.5 or above). The reference exemplifies the use of a mixture of guar gum with either Eudragit RL 30 D (in a ratio of 4:1), Eudragit® L 30 D (in a ratio of 3 : 1) or Eudragit® S 100 (in a ratio of 2.5 : 1) as a tablet g.

An article in the European Journal of Pharmaceutical Sciences (Krogarset al; 17; (2002); 23-30) discloses the use of Hylon™ VII (an amylose-rich (~70 wt%) maize starch; National Starch, Germany) as a film coating for tablets containing a drug (theophylline). Dissolution of the tablets in acidic medium was rapid with more than 75% of the drug being dissolved within 15 minutes. The coating did not contain a second film forming polymer.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external nts is not to be construed as an admission that such documents, or such sources of ation, in any iction, are prior art, or form part of the common general knowledge in the art.

The term "comprising" as used in this specification means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and ises" are to be interpreted in the same manner.

In accordance with a first aspect of the present invention, there is provided a delayed release drug formulation for delivery of a drug to the colon comprising a particle with a core and a g for the core, the core comprising a drug and the coating comprising a single layer of a mixture of a first material which is susceptible to attack by colonic bacteria and a second material which is a film-forming polymeric material having a pH threshold at about pH 6.5 or above, wherein the first material is chitosan; and n the pH threshold of the second material is the pH below which it is insoluble and at or above which it is soluble.

In accordance with a further aspect of the present invention, there is provided use of a formulation of the first aspect, n the drug is an nflammatory agent and/or the drug is a steroid, in the manufacture of a medicament for the ent of inflammatory bowel disease.

In accordance with another aspect of the present invention, there is ed use of a formulation of the first aspect, wherein the drug is an antineoplastic agent, in the manufacture of a medicament for the treatment of carcinoma.

In accordance with another aspect of the present invention, there is provided use of a formulation of the first aspect, n the drug is 5-aminosalicylic acid, in the manufacture of a medicament for the laxis of carcinoma.

In accordance with another aspect of the t invention, there is provided a method of preparing a delayed release drug formulation of the first aspect, said method comprising: forming a core comprising a drug; and g the core in a single layer with a polymer coating preparation comprising a mixture of a first material which is susceptible to attack by c bacteria and a second material which is a filmforming polymeric material having a pH threshold at about pH 6.5 or above, n the first material is chitosan.

Disclosed herein is a delayed release drug formulation comprising a particle with a core and a coating for the core, the core comprising a drug and the coating comprising a mixture of a first material which is tible to attack by colonic bacteria and a second material which has a solubility threshold at about pH 5 or above, wherein the first material comprises a polysaccharide selected from the group consisting of starch; amylose; amylopectin; chitosan; chondroitin e; cyclodextrin; dextran; pullulan; carrageenan; scleroglucan; chitin; curdulan and levan.

The first material comprises a polysaccharide, preferably containing a plurality of glucose units. Preferably the polysaccharide is starch, amylose or amylopectin, most ably starch.

It has surprisingly been discovered that the disadvantageous ng of materials susceptible to attack by colonic bacteria, e.g. amylose, can be controlled by a pH dependent material which is soluble at pH 5 or above. In addition, the Inventors have discovered that, unexpectedly, gs containing large proportions of amylopectin would also work to provide colonic release of a drug from an oral dosage formulation.

A further technical advantage of the present invention (compared, for example, to the formulation sed in WO–A-01/76562) is that ntially no drug is released for an extended period (that is, whilst the g is being dissolved), following which the drug is released relatively quickly. This is in contrast to homogeneous tablets from which the drug release profile is gradual from the outset rather than delayed then pulsatile.

The person skilled in the art is capable of determining whether a material is susceptible to attack by colonic bacteria using techniques comprising part of the common general knowledge. For example, a pre-determined amount of a given material could be exposed to an assay ning an enzyme from a bacterium found in the colon and the change in weight of the material over time may be measured.

The polysaccharide is preferably starch. Starches are usually extracted from natural sources such as cereals; pulses; and tubers. Suitable es for use as disclosed herein are typically food grade starches and include rice starch; wheat starch; corn (or maize) starch; pea starch; potato starch; sweet potato starch; tapioca starch; sorghum starch; sago starch; and arrow root starch. The use of maize starch is exemplified below.

Starch is actually a mixture of two different polysaccharides, namely amylose and amylopectin. Different starches may have different proportions of these two ccharides. Most natural (unmodified) maize starches have from about 20 wt % to about 30 wt % amylose with the remainder being at least substantially made up of amylopectin. Starches suitable for use as disclosed herein typically have at least 0.1 wt %, e.g. at least 10% or 15%, preferably at least 35 wt %, e. "High amylose" starches, are starches having at least 50 wt % amylose. Particularly suitable starches have from about 65 wt % to about 75 wt %, e.g. about 70 wt % amylose.

Starches le for use as disclosed herein may have up to 100% amylopectin, more typically from about 0.1 wt % to about 99.9 wt % amylopectin.

"Low amylose" starches, i.e. starches having no more than 50 wt % amylose and at least 50 wt % amylopectin, e.g. up to 75 wt % amylopectin and even as much as up to 99 wt % amylopectin, are suitable. The starch may be, for instance, fied waxy corn starch. This lly comprises about 100% amylopectin. "Low amylose" starch was not expected to be le, since low amylose starch is typically degraded by pancreatic enzymes in the small intestine. Preferred starches have no more than 50 wt % ectin. Particularly suitable starches have from about 25 wt % to about 35 wt % amylopectin, e.g. about 30 wt % amylopectin.

The person skilled in the art is capable of determining the relative proportions of amylose and amylopectin in any given starch. For e, near-infrared ("NIR") spectroscopy could be used to determine the e and amylopectin content of a starch using calibration curves obtained by NIR using tory-produced mixtures of known amounts of these two components. r, starch could be hydrolysed to glucose using amyloglucosidase. A series of phosphorylation and oxidation reactions catalysed by enzymes result in the formation of d nicotinamide adenine dinucleotide phosphate ("NADPH"). The quantity of NADPH formed is stochiometric with the al glucose content. le test kits for this procedure are available (e.g., R-Biopharm GmbH, Germany). Another method that could be used involves subjecting the coating to digestion by bacterial enzymes, e.g. α-amylase, to e short chain fatty acids ("SCFA") which can be quantified by gas-liquid chromatography using a capillary column.

Preferred starches have amylose in its glassy form although amylose in its amorphous form may also be used as disclosed herein.

Preferred starches are "off-the-shelf" starches, i.e. starches which require no processing prior to use in the t of the present disclosure. Examples of particularly suitable "high amylose" starches include Hylon™ VII (National Starch, Germany) or Eurylon™ 7 tte, Lestrem, France) or Amylogel 03003 (Cargill, Minneapolis, USA) all of which are examples of a maize starch having about 70 wt% amylose.

The present ion involves the use of a second material which dissolves in a pH dependent manner. The second material has a "pH threshold" which is the pH below which it is insoluble and at or above which it is soluble. The pH of the surrounding medium triggers dissolution of the second material. Thus, none (or ially none) of the second material dissolves below the pH threshold. Once the pH of the surrounding medium reaches (or exceeds) the pH threshold, the second material becomes soluble. By "insoluble" we mean that 1 g of the second material requires more than 10,000 ml of solvent (surrounding medium) to dissolve at a given pH. By "soluble", we mean that 1g of the second material es less than 10,000 ml, preferably less than 5,000 ml, more preferably less than 1000 ml, even more ably less than 100 ml or 10 ml of solvent to dissolve at a given pH. Surrounding medium preferably means the medium in the gastro intestinal tract, such as the gastric juice or intestinal juice. Alternatively, the surrounding medium may be in the vitro equivalent of the medium in the gastrointestinal tract.

The normal pH of gastric juice is usually in the range of 1 to 3. The second material is insoluble below pH 5 and soluble at about pH 5 or above and soluble at about pH 5 or above and, thus, is usually insoluble in gastric juice. Such a material may be referred to as an "enteric" material.

The second material is soluble at pH 5 or above, e.g. in intestinal juice. The pH of intestinal juice gradually increases from about 6 in the duodenum to about 7 to 8 in the colon. The second material is ably insoluble below pH 6.5 (and soluble at about pH 6.5 or above) and, more preferably, is insoluble below pH 7 (and soluble at about pH 7 or above).

The pH threshold at which a material becomes soluble may be determined by a simple ion technique which would be part of the common general knowledge to the person skilled in the art.

The second al is typically a orming polymeric material such as an acrylate r, a cellulose polymer or a polyvinyl-based polymer. Examples of suitable cellulose polymers e cellulose acetate phthalate ("CAP"); cellulose acetate litate ("CAT"); and ropylmethylcellulose acetate succinate.

Examples of suitable polyvinyl-based rs include nyl acetate phthalate ("PVAP").

The second material is preferably a co-polymer of a (meth)acrylic acid and a (meth)acrylic acid C1-4 alkyl ester, for instance, a copolymer of methacrylic acid and methacrylic acid methyl ester. Such a polymer is known as a poly(methacrylic acid/methyl methacrylate) co-polymer. Suitable examples of such co-polymers are usually anionic and not sustained release polymethacrylates. The ratio of carboxylic acid groups to methyl ester groups (the "acid:ester ratio") in these co-polymers determines the pH at which the co-polymer is soluble. The acid:ester ratio may be from about 2:1 to about 1:3, e.g. about 1:1 or, preferably, about 1:2. The molecular weight ("MW") of preferred anionic co-polymers is usually from about 120,000 to 150,000, preferably about 135,000.

Preferred anionic poly(methacrylic acid/methyl rylate) co-polymers include Eudragit® L (acid:ester ratio about 1:1; MW about 135,000; pH threshold of about 6.0); Eudragit® S (acid:ester ratio about 1:2; MW about 0; pH threshold of about 7); and Eudragit® FS (a ethyl acrylate/methyl methacrylate/methacrylic acid); acid:ester ratio of about 1:10; MW about 220,000; pH threshold of about 7.) The second material may be a copolymer of methacrylic acid and ethyl acrylate. Eudragit® L100-55 poly(methacrylic acid/ethyl acrylate); acid:ester ratio of about 1:1; MW about 250,000; pH threshold of about 5.5 is suitable. The Eudragit® co-polymers are manufactured and/or buted by Degussa AG, Darmstadt, Germany.

Mixtures of film forming polymer materials may be used as riate. An example of a suitable mixture would include a mixture, e.g. a 1:1 e, of Eudragit® L and Eudragit® S. However, the use of a particular film g polymer material, e.g. a poly(methacrylic acid/methyl methacrylate) co-polymer, alone is preferred.

The use of Eudragit® S alone as the second material is particularly preferred.

In a red embodiment, it has been found that a mixture of two suitable polymers at an appropriate ratio, applied as a film coating on to a core, at least minimises, and can substantially eliminate, drug release in the stomach and small intestine. Subsequent drug release in the colon is believed to occur by the combined active physiological rs: i.e. by dissolution of the second material, particularly Eudragit® S, and digestion of the first material, e.g. starch or amylose.

The proportion of the first material to the second material is typically less than 99:1 and may in some circumstances be up to 50:50. The tion is usually up to :65 and is preferably from 15:85 to 35:65, e.g. 15:85 to 30:70. The Inventors have has discovered that a ratio of first material to second material from about 25:75 to about 35:65, e.g. about 30:70, is particularly suitable for targeting release of the drug to the colon, particularly if the first material is starch and the second material is it® S. The mixture of first and second materials is preferably substantially homogenous.

Optionally, conventional excipients such as plasticisers for film formation (for example, triethyl citrate) and ack agents (such as glyceryl monostearate) may be included in amounts up to 30% by weight of the final composition of the polymer coating preparation.

The ess of the coating of the particle is typically from about 10 μm to about 150 μm. The thickness of a specific coating will, however, depend on the composition of the g. For e, coating thickness is directly proportional to the amount of polysaccharide in the coating. Thus, in embodiments where the coating ses high amylose starch and Eudragit™ S at a ratio of about 30 : 70, the coating thickness may be from about 70 μm to about 130 μm, and preferably from about 90 μm to about 110 μm. The thickness (in μm) for a given coating composition is independent of core size.

The thickness of the coating may also be measured by the "theoretical weight gain" ("TWG") of the coated formulation. The TWG for the present formulation will depend on a number of factors including the composition of the coating and the size of the core to be coated. For example, in ments where the core is a small tablet (e.g. having a diameter of about 8 mm) and the coating comprises high amylose starch and Eudragit™ S (e.g. in a ratio of about 30 : 70), the TWG is typically from about 4% to about 12%, e.g. from about 5% to about 10%, preferably from about 8% to about 9%. In embodiments where the core is a pellet (e.g. having a diameter of about 1 mm) having the same coating, the TWG may be from about 15% to about 35%, e.g. from about 20% to about 30%, preferably about 25%.

By saying that the coating ses a mixture of the first and second materials, it is intended to exclude the known multi-layer dosage form (disclosed for example in Milojevic et al. bed above) in which an active core is coated first with an inner coating of amylose and then with an outer coating of Eudragit® L100. In the context of the present disclosure, such a multi-layer dosage form does not comprise a mixture of starch and Eudragit® L100. The coating is preferably a single layer of a mixture of the first and second materials, preferably a homogenous mixture.

The formulation of the present invention may however have an additional layer either between the active core and the layer sing the delayed release composition of the present invention and/or an outer layer coating the delayed release composition layer of the t invention. For example, if the d release composition layer comprises a e of Eudragit® L and starch, the addition of an outer layer of a pH dependent release coating material having a pH threshold of about 7, e.g. Eudragit® S, may be preferable. In preferred embodiments, the delayed release coating of the present invention is applied directly to the active core, i.e. there is no additional layer between this coating and the active core. The delayed release coating of the t invention is preferably the outer coating of the formulation.

Advantageously, it has been found that no additional outer layer is required to ensure that the ition is a delayed e composition.

The ition preferably forms a coating around the ive which is most preferably mixture of starch and Eudragit® S. The "bioactive" is usually the core comprising the drug.

The ation comprises at least one particle with a core and a coating for the core. The formulation may comprise any suitable coated oral dosage form ing capsules; tablets; mini-tablets; pellets; granules; and crystals.

The minimum diameter of each le is typically at least about 10-4m, usually at least about 5 x 10-4m and, preferably, at least about 10-3m. The maximum diameter is usually no more than 30 mm, typically no more than 20 mm and, ably, no more than 10 mm. In preferred embodiments, the particle has a diameter from about 0.2 mm to about 15 mm, preferably from about 1 mm to about 4 mm (e.g. for pellets or mini-tablets) or from about 6 mm to about 12 mm (e.g. for certain tablets or capsules).

The term "diameter" refers to the largest linear dimension through the le.

The formulation may comprise a plurality of particles in order to e a single dose of the drug(s), particularly in embodiments in which the particle is "small", e.g. having a diameter of less than 5 mm. Multi unit dosage forms comprising particles having a diameter of less than 3 mm are preferred.

The present invention has application in a multi-phasic drug e formulation comprising at least two ities of particles, e.g. coated pellets, in the same dosage form, e.g. a capsule, in which the particles of one plurality are differentiated from the particles of the or each other plurality by the g. The coatings may differ from one plurality to the next in terms of coating thickness or composition, e.g. the ratio and/or identity of components. Multi-phasic drug release formulations would be particularly suitable for suffers of Crohn’s disease affecting different regions along the intestine.

The "core" is usually a single solid body. The core may consist of the drug(s) alone or may be a bead of edible material, e.g. sugar, which is coated with a layer comprising the drug(s). More usually, r, the core consists of a mixture of the drug(s) with a filler or t material, e.g. lactose or cellulose material such as microcrystalline cellulose; a binder, e.g. polyvinylpyrrolidone ("PVP"); a disintegrant, e.g. Ac-Di-Sol™ (i.e. croscarmellose sodium); and/or a lubricant, e.g magnesium stearate. The core may be a compressed granulate comprising at least some of these materials.

Release from formulations according to the present invention is delayed until the intestine and preferably the colon. Release from certain formulations may also be sustained. However, in preferred formulations, release is pulsatile.

A formulation is y defined as gastric resistant if there is less than 10 wt % drug release in acidic media after 2 hours. Formulations according to the present invention typically display far less than 10 wt % drug release in acidic media and may be considered to be gastric resistant. The formulations usually y less than 1 wt % drug release in acidic media and, typically, display substantially no drug release in acidic media. When starch is combined with an acrylate film g material to form the coating for the core, typically less than 5% drug e occurs over 5 hours in conditions ting the stomach and small intestine. On combination of starch with a cellulosic film forming material for the coating for the core, typically less than 10% drug release occurs over 5 hours in conditions simulating the stomach and small intestine.

The time between initial exposure to conditions suitable for drug e and the start of drug e is known as the "lag time". The "lag time" depends on a number of factors including coating thickness and composition. Formulations according to the present invention usually display a lag time in colonic conditions of at least 30 minutes. In most embodiments of the t invention, the lag time is from about 30 minutes to about 3 hours and, in preferred formulations, the lag time is ably from about 45 minutes to about 2 hours.

The time between initial exposure to conditions suitable for drug release and complete drug release also depends on a number of factors including coating composition and the nature of the drug. In most embodiments of the present invention, this time is usually no more than 5 hours. In preferred embodiments, this time is usually no more than 4 hours.

By way of an example, in embodiments in which a tablet core is coated to a thickness of from 8% to 9% TWG with a coating comprises a high amylose starch and Eudragit S (30:70), the time between l release and complete release may be less than about 2 hours, preferably less than about 1.5 hours.

In a preferred embodiment, the core is a pellet having a diameter of about 1 mm. In another ment, the core is a tablet having a diameter of about 8 mm. In both cases, the coating is preferably a 30:70 mixture of high amylose starch, e.g.

Eurylon™ 7, and an acrylic polymer, e.g. Eudragit™ S. In both preferred embodiments, the core is coated to a thickness of about 100 μm which is from about 8% to about 9% TWG for the tablet and from about 27% to about 32 wt % for the pellet.

According to a further aspect of the present invention, there is provided a ation according to the first aspect for use in a method of l treatment of the human or animal body by therapy.

The core comprises at least one drug. The formulation is y used to administer a single drug as the sole therapeutically active component. However, more than one drug may be administered in a single formulation.

The formulation of the present invention is designed to ster a wide range of drugs. Suitable drugs include those drugs which are known for intestinal administration using known delayed e oral formulations. The present invention may be used to administer drugs having a local or a systemic effect.

The formulation of the t invention has particular application in the intestinal administration of a drug comprising at least one acidic group such as a carboxylic acid group. Such drugs may be acidic drugs or zwitterionic drugs. An example of such a drug is 5-aminosalicylic acid ("5-ASA").

The identity of the drug(s) in the formulation obviously depends on the condition to be treated. In this connection, the formulation has ular application in the treatment of IBD (including Crohn’s disease and ulcerative colitis); IBS; constipation; diarrhoea; infection; and carcinoma, particularly colon or colorectal cancer).

For the treatment or prevention of IBD, the formulation may comprise at least one drug selected from the group consisting of anti-inflammatory agents (e.g. 5-ASA); steroids (e.g. prednisolone; budesonide or fluticasone); suppressants (e.g. azathioprine; cyclosporin; and methotrexate); and antibiotics.

For the treatment or prevention of cancer, the formulation may comprise at least one antineoplastic agent. Suitable antineoplastic agents include uracil; methotrexate; dactinomycin; bleomycin; etoposide; taxol; vincristine; doxorubicin; cisplatin; daunorubicin; VP-16; raltitrexed; oxaliplatin; and pharmacologically able derivatives and salts thereof. For the prevention of colon cancer or colorectal cancer, primarily in patients suffering from colitis, the formulation may comprise the anti-inflammatory agent, 5-ASA.

For the ent or prevention of IBS, constipation, oea or infection, the formulation may comprise at least one active agent suitable for the treatment or tion of these conditions.

Pharmacologically able derivatives and/or salts of the drugs may also be used in the ation. An example of a suitable salt of prednisolone is methyl prednisolone sodium ate. A further example is fluticasone propionate.

The present invention has particular application in either the treatment of IBD (particularly, ulcerative colitis) or the prevention of colon cancer or colorectal cancer (primarily in s patients), both using 5-ASA. It also has application as a portal of entry of drugs into the systemic circulation via the colon. This is particularly advantageous for e and protein drugs which are unstable in the upper intestinal tract. The present invention may also be utilised for the purpose of chronotherapy.

Disclosed herein is a method of targeting a drug to the colon sing administering to a patient a formulation as defined above.

In a further aspect of the invention, there is ed the use of a formulation of the first aspect in the manufacture of a medicament for the treatment or prevention of IBD (particularly ulcerative colitis); IBS; constipation; diarrhoea; infection; and cancer.

There is also provided the use of at least one drug selected from antiinflammatory agents and steroids in the manufacture of a medicament comprising a formulation of the first aspect for use in the treatment of IBD. In addition, there is also provided the use of at least one antineoplastic agent in the cture of a medicament comprising a formulation of the first aspect for use in the ent of carcinoma. Further, there is also provided use of 5-ASA in the manufacture of a medicament comprising a formulation of the first aspect for use in the prevention of colon cancer or colorectal cancer.

Disclosed is a method of medical treatment or prevention of IBD or carcinoma ses administering to a patient a therapeutic amount of a formulation as defined above.

The formulation will typically comprise a therapeutically effective amount of the or each drug which may be from about 0.01 wt % to about 99 wt %, based on the total weight of the formulation. The actual dosage would be determined by the skilled person using his common general knowledge. However, by way of example, "low" dose formulations typically comprise no more than about 20 wt % of the drug, and preferably comprise from about 1 wt % to about 10 wt %, e.g. about 5 wt %, of the drug. "High" dose formulations typically comprise at least 40 wt % of the drug, and preferably from about 45 wt % to about 85 wt %, e.g. about 50 wt % or about 80 wt %.

Disclosed is a method of preparing a delayed e drug formulation disclosed herein, said method comprising: forming a core sing at least one drug; and coating the core with a polymer coating preparation comprising a mixture of a first material which is susceptible to attack by colonic ia and a second material which has a pH threshold at about pH 5 or above, wherein the first material comprises a polysaccharide selected from the group consisting of starch; e; amylopectin; chitosan; chondroitin sulfate; extrin; dextran; pullulan; carrageenan; scleroglucan; chitin; curdulan and levan. Preferred polysaccharides are as detailed above. The core is preferably spray coated with said r coating preparation.

In embodiments in which the core is formed from a compressed granulate, the method preferably comprises: dry mixing the drug(s) with at least one excipient to form a dry mixture; wet granulating at least a portion of said dry e to form a wet granulate; compressing at least a n of said wet granulate to form said core; and spray coating said core with said polymer coating preparation to form said delayed release drug ation. A fluidised bed spray coating machine is preferably used to coat the core(s) with the polymer coating preparation to form the particle(s) of the formulation.

In preferred embodiments, the method ses: forming an aqueous dispersion comprising said first material; forming an alcoholic or aqueous solution comprising said second material; and adding, preferably drop-wise, at least a n of said aqueous dispersion of said first material to at least a portion of said alcoholic or aqueous solution of said second material to form said polymer coating preparation.

The first material is usually dispersed in at least one alcohol, preferably a C1 to C6 alcohol, e.g. methanol; ethanol; propanol; propanol; butanol; butanol; and es thereof, particularly butanol alone, and then water is usually added subsequently with good ion. The resulting aqueous dispersion is usually heated to boiling and then cooled with stirring overnight. The purpose of the alcohol(s) is to solvate the first material ready to form the aqueous dispersion. Alternatively, the al can be dispersed directly in water.

The second material is typically dissolved in at least one solvent, for instance water or an organic solvent. The organic solvent may be an alcohol, e.g. methanol; ethanol; propanol; methyl glycol; butyl glycol; acetone; methyl glycol acetate; and mixtures thereof such as acetone and isopropyl alcohol (e.g. in a ratio of about 4:6).

The second material is preferably dissolved in ethanol (preferably from 85 to 98%), under high speed stirring.

The polymer coating preparation is preferably formed by adding an appropriate quantity of the aqueous dispersion to the alcoholic solution, drop-wise under fast stirring. The further excipient(s) such as a plasticiser (e.g. triethyl citrate) and/or a lubricant (e.g. glyceryl earate) is usually added to the preparation while stirring.

In the description in this specification reference may be made to subject matter which is not within the scope of the appended . That subject matter should be readily identifiable by a person skilled in the art and may assist in g into practice the invention as d in the appended claims.

A number of preferred embodiments of the present invention will now be described with reference to the drawings, in which:- Figure 1 is a graph depicting the dissolution profiles of mixed film coated prednisolone s at 5% TWG and Eudragit® S coated s at 5% TWG in pH 7.0 buffer; Figure 2 is a graph depicting the dissolution profiles of mixed film coated s as for Figure 1 but with 6% TWG; Figure 3 is a graph depicting the dissolution profiles of mixed film coated tablets as for Figure 1 but with 7.4% TWG; Figure 4 is a graph depicting the dissolution profiles of mixed film coated tablets as for Figure 1 but with 8.3% TWG; Figure 5 is a graph ing the dissolution profiles of prednisolone s coated with 30% starch : 70% Eudragit S at s polymer weight gains and Eudragit® S coated tablets at 5% TWG; Figure 6 is a graph depicting the dissolution profile of prednisolone tablets coated with 30% starch : 70% Eudragit® S in pH 6.8 buffer, with and without atin; Figure 7 is a graph depicting drug release from prednisolone tablets coated to 8.3% TWG in pH 6.8 buffer containing 50 U/ml amylase; Figure 8 is a graph depicting the ution profile of 5-ASA tablets coated with 30% starch : 70% Eudragit® S to 8.3% TWG in pH 6.8 buffer; Figure 9 is a graph depicting the dissolution profiles of 5-ASA tablets coated with 30% starch : 70% Eudragit® S to various polymer weight gains in pH 6.8 buffer containing 50 U/ml amylase; Figure 10 is a graph depicting the dissolution profiles of prednisolone tablets coated with 70% Eudragit® S : 30 wt % starch having either 70 wt % or 27 wt % amylose in pH 7 buffer; Figure 11 is a graph depicting the dissolution profiles of prednisolone tablets as for Figure 10 in pH 6.8 buffer; Figure 12 is a graph depicting the dissolution es of the prednisolone tablets as for Figure 10 in pH 6.8 buffer containing 50 U/ml amylase; Figure 13 is a graph depicting the dissolution profile of prednisolone s coated with 70% Eudragit® L : 30% starch to 8.3% TWG in pH 5.5 buffer; Figure 14 is a graph depicting the dissolution e of prednisolone tablets as for Figure 13 in pH 5.5 buffer ning 50 U/ml amylase; Figure 15 is a graph depicting the dissolution profile of prednisolone tablets coated with 70% HPMCAS-HG : 30% starch in pH 6.5 buffer; Figure 16 is a graph depicting the dissolution profile of the prednisolone s as for Figure 15 in pH 6.5 buffer containing 50 U/ml amylase; and Figure 17 is a graph depicting the ution profile of the prednisolone tablets as for Figure 15 in pH 6.8 buffer.

EXAMPLE 1 Preparation of Prednisolone tablets Prednisolone tablets (weight 200 mg, diameter 8 mm and standard bi-concave) were ed according to the following formula: Lactose 85% Prednisolone 5% PVP 5% 4% (2/3 intragranular and 1/3 Ac-Di-Sol™ extragranular) Magnesium stearate 1% (extragranular) solone was dry mixed with the excipients and then wet granulated.

Granules of 500-710 μm size fraction were compressed using a single punch tabletting machine (Manesty, UK).

Formulation for Starch aqueous sion Eurylon™ 7 16g Butanol 32g Water 352g Eurylon™ 7 starch was sed well in the butanol and water subsequently added with good agitation. The resulting dispersion was then heated to boiling, and cooled with stirring ght. The % solids t of the cooled dispersion was calculated based on the final weight of the dispersion (allowing for evaporation during heating).

Formulation for Eudragit® S solution Eudragit® S solution was prepared by dissolution of Eudragit® S 100 r in 96% ethanol under high speed stirring. The final solution contained approximately 6% polymer solids.

Mixed Starch-Eudragit® coating dispersion Appropriate quantities of the starch dispersion and Eudragit® solution were mixed to give the required ratios stated as the dry polymer substance. The starch was always added to the Eudragit® solution drop-wise under fast stirring. The resulting sions were left stirring for two hours before the addition of the excipients and for another two hours after adding excipients. The added excipients were: Triethyl citrate 10% of dry polymer substance Glyceryl earate 5% of dry polymer substance The final mixed polymer coating preparation was film coated onto the s using a fluidised bed spray coating machine. g thickness was estimated as % weight increase of the tablets following coating (% TWG) The spray coating ters were as follows: Flow rate 0.7 ml/minute Atomising pressure 0.2 bar Coating temperature 40°C In Vitro Tests Starch dispersion was prepared from Eurylon 7, a "high amylose" starch, and mixed with a solution of Eudragit® S in ethanol. The composition and preparation method for the coating dispersions are as described above. Various starch/Eudragit® S combinations were prepared containing 15%, 20%, 25%, 30% and 35% starch. The mixed Eudragit®/starch coating dispersions were then film coated onto solone tablets prepared according to the method described above. Tablets were coated to g thicknesses, calculated as total weight gain on the polymer, to also ine the optimum coating thickness. The g mixture yielded good quality films up to a ratio of 30% starch.

Coated tablets were then testedin vitro for drug release in varying pH buffer solution. The optimum starch/Eudragit® S ratio and g weight gain was primarily based on comparison of the dissolution profile with conventional Eudragit® S coated tablets.

Results are shown in s 1-7.

Very surprisingly, these mixed film coated tablets were able to resist drug release in pH 1.2 HCl simulating the gastric media (see the left-hand side of the graphs of Figures 1-6).

There was also no drug release from any of the coated tablets for up to 12 hours in pH 6.8 simulating the small intestinal media (see Figure 6). Previous in vitro studies using mixed amylose/acrylate polymers based on the water-insoluble Eudragit® RL and RS products showed uncontrollable ng and rapid drug release in acid and buffer (Milojevic et al., 1996).

Drug release profiles from the coated tablets in pH 7.0 buffer media are shown in Figures 1 to 5. Based on an analysis of the dissolution profiles, tablets coated with a 30% starch/Eudragit® mixture to a film thickness equivalent to a TWG of 8.3% was judged to be optimal, and were further tested to assess the digestibility of the starch component of the film.

The tablets were dissolution tested in pH 6.8 buffer containing 50 U (units)/ml ase d fromB. licheniformis (see Figure 7). A dissolution test was also carried out in pH 6.8 media with pancreatin to test whether the starch is ible by pancreatic α-amylase (see Figure 6).

Results of the ution tests in the presence of the enzymes show that the starch ent of the film is indigestible in the presence of the pancreatin (suggesting resistance in the small intestine), but drug release occurred within three hours in the presence of α-amylase from B. licheniformis. These results provide evidence that the mixed film s drug release in simulated conditions of the upper gastrointestinal tract but is digestible in the presence of bacterial enzymes (even at a pH lower than the threshold pH of the Eudragit® S polymer for dissolution).

In vivo study in healthy volunteers Following the surprising success of the in vitro studies with the mixed starch/Eudragit® S film coated s; the performance of the dosage form was tested in y human ts. The tablets were radio-labelled with Indium-111 and administered to eight healthy male volunteers on three separate occasions. The transit and disintegration site of the tablet in the gastrointestinal tract was followed using a gamma camera.

The time and site of disintegration of these mixed film tablets can be seen in Table 1. The results show surprisingly excellent colonic targeting, with tablet disintegration occurring primarily in the colon.

The results from the healthy volunteer study provides evidence that starch and Eudragit® mixed at a proportion of 30% starch to 70% Eudragit® S and coated onto tablets at approximately 8.3% TWG, is able to resist tablet disintegration in the stomach and small intestine but trigger disintegration in the colon.

Table 1 shows the site and time of disintegration of 30% starch and 70% Eudragit® S coated tablets in eight healthy male volunteers on three separate occasions.

Key to Table 1: "Fasted" - tablet given on an empty stomach; ed" - tablet given on an empty stomach, but meal administration 30 minutes post dose; and "Fed" - tablet given after breakfast.

"ICJ" - ileocolonic on; "AC" - ascending colon; "HF" - hepatic flexure; and "SF" - splenic flexure.

TABLE 1 Treatment 1 (Fasted) Treatment 2 (Pre-fed) Treatment 3 (Fed) t Site Time Site Time Site Time 1 ICJ 237 ICJ 244 AC 240 2 AC 200 ICJ 339 AC 316 3 AC 201 ICJ 350 AC 510 4 AC 292 HF 390 AC 415 TC 465 SF 678 AC 555 Subject did 6 not attend - AC 523 AC 523 study day 7 AC 274 AC 244 SF 465 Tablet did not 8 AC 614 empty from - AC 455 stomach EXAMPLE 2 Tablets (weight 200 mg; diameter 8 mm; standard bi-concave) containing 5 wt % -aminosalicylic acid in place of 5 wt % prednisolone were prepared and coated with a polymer mixture comprising 70% Eudragit® S : 30% starch on™ 7) to 5%, 6%, 7% and 8.3% TWG in accordance with the procedure given in Example 1.

The 5-ASA tablets with different weight gains of 5,6, 7 and 8.3% were then tested in vitro for drug release in pH 6.8 buffer in the absence of α-amylase. Figure 8 indicates that for the 5-ASA tablet coated to 8.3% TWG there was no release of 5-ASA for about 9 hours with almost complete release after about 11 hours.

The 5-ASA tablets with each of the different TWGs were then testedin vitro for drug release in the presence of 50 U/ml α-amylase. Figure 9 indicates that drug release was much faster for all TWGs in the presence of α-amylase.

The 5-ASA tablet coated to 7% TWG gave a similar me in pH 6.8 buffer (about 2 hours) as a 5 wt % prednisolone tablet coated to 8.3% TWG. Without wishing to be bound by any particular theory, this result may be explained by 5-ASA exhibiting acidic properties as it dissolves in the near neutral buffer, thus reducing the pH at the tablet core/polymer boundary layer relative to the bulk medium and consequently retarding dissolution of the polymer coating.

EXAMPLE 3 s (weight 200 mg; er 8 mm; standard bi-concave) containing 5 wt % solone were prepared and coated with a polymer mixture comprising 70% Eudragit® S : 30% starch to 8.3% TWG in accordance with the procedure given in Example 1. The starch used was either a "high" e maize starch (Eurylon™ 7; ~70 wt % e) or a "low" amylose starch (natural maize starch; ~27 wt % amylose; Sigma, Poole, UK).

The tablets were then tested in vitro for drug release in pH 7 buffer without amylase and then in pH 6.8 buffer, with and without 50 U/ml α-amylase.

Figures 10 and 11 indicate that drug release is quicker using "low" amylose starch.

Figure 11 indicates that there is a me of about 2.5 hours in small intestinal conditions for the "low" amylose starch tablets which was shorter than the lag time for the "high" e starch tablets. This result may be ned by noting that amylopectin is more water soluble than amylose. Thus, the greater the proportion of amylopectin, the r the coating dissolves in aqueous solution. Figure 12 indicates that drug release is substantially quicker in the presence of α-amylase.

The tablets having the coating containing "low" amylose starch have also been demonstrated (using the same procedure as for Figure 6) to be indigestible to pancreatin for l hours, further substantiating the resistance of the "low" amylose system in the small intestine. Such ance is surprising as amylopectin is a substrate of pancreatic amylase (present in pancreatin) and, therefore, ion of the coating and drug release would have been expected.

EXAMPLE 4 Tablets (weight 200 mg; diameter 8 mm; standard bi-concave) ning 5 wt % prednisolone were prepared and coated with a polymer mixture comprising 70% Eudragit® L : 30% starch (Eurylon™ 7) to 8.3% TWG in accordance with the procedure given in Example 1.

The tablets were then tested in vitro for drug e in pH 5.5 buffer, first without amylase and then with 50 U/ml α-amylase.

Figure 13 indicates a lag time of just under 4 hours in small intestinal conditions. r, in the presence of ase, the lag-time was about 3 hours (Figure 14). The results indicate that this coating system could be used for drug release in the proximal small intestine.

Tablets (weight 200 mg; diameter 8 mm; standard bi-concave) containing 5 wt % prednisolone were prepared and coated with a polymer mixture comprising 70% hydroxypropyl methylcellulose acetate succinate AS") : 30% starch (Eurylon™ 7) to 8.3% TWG generally in accordance with the procedure given in Example 1. The HPMCAS (ShinEtsu, Japan) used had the granular grade HG with a pH threshold of 6.8.

The HPMCAS-HG was ved in 90% ethanol and the aqueous dispersion of starch added to it.

The tablets were then tested in vitro for drug e in pH 6.5 buffer, first without amylase and then with 50 U/ml α-amylase. Further tablets were then testedin vitro for drug release in pH 6.8 buffer in the absence of α-amylase.

Figure 15 indicates that the coating had a tendency to swell below the pH threshold of the HMPCAS-HG, allowing slow ion of the drug out of the formulation prior to dissolution of the coating and a burst of drug release. The lag-time prior to the onset of diffusion in pH 6.5 buffer in the absence of ase was about 2 hours which would be ient to retard release until the distal small intestine. Diffusion continued for approximately an additional 4.5 hours resulting in almost 40% of the drug diffusing out prior to the burst release.

In the presence of α-amylase, there was no lag time in pH 6.5 buffer with diffusion starting immediately and releasing 20% of the drug prior to the onset of the burst release (Figure 16). r, at pH 6.8, this diffusion phenomenon does not exist, presumably due to the faster dissolution of the system (Figure 17).

It will be appreciated that the invention is not restricted to the details bed above with reference to the preferred embodiments but that numerous modifications and variations can be made without departing from the spirit or scope of the invention as defined by the following claims.

Claims (27)

WHAT WE CLAIM IS:

1. A delayed release drug formulation for delivery of a drug to the colon comprising a particle with a core and a coating for the core, the core comprising a drug and the coating 5 comprising a single layer of a mixture of a first material which is susceptible to attack by colonic bacteria and a second material which is a orming polymeric material having a pH threshold at about pH 6.5 or above, wherein the first material is an; and wherein the pH threshold of the second material is the pH below which it is insoluble and at or above which it is soluble.

2. A formulation according to claim 1, wherein the second material is an acrylate polymer.

3. A formulation as claimed in claim 1 or claim 2, wherein the second material is an 15 anionic copolymer of (meth)acrylic acid and (meth)acrylic acid C1-4 alkyl ester.

4. A formulation as claimed in claim 3, wherein the second material is an anionic copolymer of methacrylic acid and methacrylic acid methyl ester. 20

5. A formulation as claimed in claim 4, n the ratio of methacrylic acid to methacrylic acid methyl ester is about 1:2.

6. A formulation as claimed in any one of the preceding , wherein the second material is an anionic poly(methacrylic acid/methyl methacrylate) comprising an 25 ster ratio of about 1:2 and having a MW of about 135,000 and a pH old of about 7.

7. A formulation as claimed in claim 1, wherein the second al is a cellulose polymer.

8. A formulation as d in claim 7, wherein the cellulose polymer is hydropropylmethylcellulose e succinate.

9. A formulation as claimed in any one of the preceding claims, wherein the 5 tion of the first material to the second material is up to about 35:65.

10. A ation as claimed in claim 9, wherein the proportion of the first al to the second material is from 15:85 to 35:65. 10

11. A ation as claimed in any one of the preceding claims, wherein the minimum diameter of the particle is at least about 5 x 10-4m.

12. A formulation as claimed in any one of the preceding claims, wherein the thickness of the coating as measured by the theoretical weight gain (“TWG”) of the 15 coated formulation is from 5 to 10%.

13. A formulation as claimed in any one of claims 1 to 11, wherein the thickness of the coating as measured by the theoretical weight gain (“TWG”) of the coated formulation is from 15 to 35%.

14. A ation as claimed in any one of claims 1 to 11, wherein the coating has a thickness of from about 10 μm to about 150 μm.

15. A formulation as claimed in any one of the preceding claims, wherein the drug 25 comprises at least one acidic group.

16. A formulation as claimed in any one of the preceding claims, wherein the drug is an anti-inflammatory agent. 30

17.A formulation as claimed in claim 15 or claim 16, wherein the drug is 5- aminosalicylic acid.

18. A formulation as claimed in any one of claims 1 to 14, wherein the drug is a steroid. 5

19. A formulation as claimed in claim 18, wherein the drug is selected from prednisolone; budesonide; fluticasone and derivatives f.

20. A formulation as claimed in any one of claims 1 to 14, n the drug is an antineoplastic agent.

21. A formulation as claimed in any one of the ing claims, for use in a method of medical treatment of the human or animal body by y.

22. Use of a formulation as claimed in any one of claims 16 to 19, in the manufacture 15 of a medicament for the treatment of inflammatory bowel disease.

23. Use of a formulation as claimed in claim 20, in the manufacture of a medicament for the treatment of carcinoma. 20

24. Use of a formulation as claimed in claim 17, in the manufacture of a medicament for the prophylaxis of carcinoma.

25. A method of preparing a delayed release drug formulation as claimed in claim 1, said method comprising: 25 forming a core comprising a drug; and coating the core in a single layer with a polymer coating preparation comprising a mixture of a first material which is susceptible to attack by colonic bacteria and a second material which is a film-forming polymeric material having a pH old at about pH 6.5 or above, 30 wherein the first material is chitosan.

26. A method as claimed in claim 25, n the core is spray coated with said polymer coating preparation.

27. A method as claimed in claim 25 or claim 26, comprising: 5 forming an aqueous dispersion of said first material; forming an alcoholic or aqueous solution of said second al; and adding at least a portion of said aqueous dispersion of said first material to at least a portion of said alcoholic or aqueous solution of said second material to form said polymer coating preparation. g 66 a! do 0 ‘ 0 30 6O 90 120 150 180 210 240 270 300 330 360 -393 420 450 480 ‘ ' 11me(nunutea) 3: +15%Stard1 E 60 alch a! *25%Sialch +30%Slaroh 3.2 +Eud1aah$only 0 so 60 90 120 150 180 210 240 270 300 330 360 390 420 450 430 11me(mlnutas) 2-/ 9