Staniforth, John (1 Prospect West, Chippenham Wiltshire SN14 6FH, GB)
|1.||A pharmaceutical composition comprising a chemotherapeutic agent, wherein the composition provides a therapeutic effect over a period of at least 8 hours following administration and the release of the chemotherapeutic agent from the composition over that period is controlled to provide an optimised effect.|
|2.||A composition as claimed in claim 1, wherein the composition is for oral administration.|
|3.||A composition as claimed in either or the preceding claims, wherein the composition further comprises one or more therapeutic and/or prophylactic agents.|
|4.||A composition as claimed in any one of the preceding claims, wherein the optimised effect is observed where the release of the chemotherapeutic agent maintains the concentration at a therapeutically effective level in order to provide the therapeutic effect.|
|5.||A composition as claimed in any one of claims 1 to 3, wherein the optimised effect is observed where the release of the chemotherapeutic agent provides a series of concentration peaks and troughs.|
|6.||A composition as claimed in any one of the preceding claims, wherein the composition provides a period of effect of at least about 12 hours or at least about 24 hours.|
|7.||A composition as claimed in any one of the preceding claims, wherein the chemotherapeutic agent is included in its base form.|
|8.||A pharmaceutical composition as claimed in any one of the preceding claims, wherein the composition is for gastrointestinal deposition and comprises a non compressed freeflowing plurality of particles.|
|9.||A composition as claimed in claim 8, wherein the particles have a mean diameter of greater than lOμm to about l mm.|
|10.||A composition as claimed in either of claims 8 or 9, further comprising a watersoluble excipient, the composition being capable of dissolving or dispersing in a subject's mouth within 1 minute after administration, preferably without the coadministration of a fluid.|
|11.||A pharmaceutical composition as claimed in any of the preceding claims, wherein the chemotherapeutic agent is an antibiotic, a cancer chemotherapeutic agent, an antifungal agent, an antiprotozoal agent, an antiviral agent, an anthelminthic agent, or any combination thereof.|
|12.||A pharmaceutical composition as claimed in any of the preceding claims, wherein the chemotherapeutic agent is ciprofloxacin, preferably ciprofloxacin base.|
|13.||A pharmaceutical composition comprising an enhancing agent and a chemotherapeutic agent, wherein the enhancing agent increases the efficacy of the chemotherapeutic agent and the composition is prepared for separate, sequential or simultaneous administration of the enhancing agent and the chemotherapeutic agent.|
|14.||A composition as claimed in any one of claim 1 to 7, further comprising an enhancing agent.|
|15.||A composition as claimed in claim 13 or 14, wherein the enhancing agent achieves an effective concentration before the chemotherapeutic agent achieves an effective concentration.|
|16.||A composition as claimed in any one of claims 13 to 15, wherein the enhancing agent is a steroidal emulsifier, is clavulanate, or a salt thereof, or is a monoclonal antibody.|
The present invention relates to pharmaceutical compositions for use in chemotherapy and, in particular, compositions that exhibit greater efficacy through optimisation of the administration of the chemotherapeutic agent. Compositions of this type are particularly useful for treating bacterial infections, fungal infections, protozoal infections, viral infections, worm infections and cancer.
Chemotherapeutic agents make useful medicines because of the toxic effect they have on infective agents and/or on parasitic cells. Infective agents or parasitic cells can either be killed, or their growth or reproduction inhibited, by chemotherapeutic agents. Chemotherapeutic agents can be antibiotics, cancer chemotherapeutic agents, anti-fungal agents, anti-protozoal agents, anti-viral agents and/or anthelminthic agents.
Despite their usefulness, chemotherapeutic agents can be harmful to the organism being treated and so must be used with great care. As well as treating a host organism by attacking the infective agents or the parasitic cells within the host organism, chemotherapeutic agents may attack the cells of the host organism. This is a particular problem if inappropriate chemotherapeutic agents are chosen (i.e. those that are not selective for infective agents or parasitic cells), or inappropriate dosages of chemotherapeutic agents are used. Accordingly, there are a number of serious side affects that are associated with the use of chemotherapeutic agents, for example, depression of the bone marrow, alopecia, nausea, vomiting, fever, headache, myalgia and gastro-mtestinal symptoms.
In order to reduce the number and scale of the aforementioned side effects, it is advantageous for as low a dose of chemotherapeutic agent as possible to be used in any given course of treatment. There are further good reasons for favouring lower doses of chemotherapeutic agents. For example, it is particularly important that nursing mothers being treated with chemotherapeutic agents are given as small a dose of the chemotherapeutic agent as possible as the agents can be expressed in the mother's milk. Another group that should only be administered with low doses
of chemotherapeutic agent is animals that are bred for food, including farmed fish. Because chemotherapeutic agents fed to animals may end up in their tissue or, in the case of farmed fish, may end up in the water, it is possible for chemotherapeutic agents fed to animals to end up in the food chain.
A further problem associated with the use of chemotherapeutic agents is that their widespread use has, in some cases, led to the creation of strains of infective agents and parasitic cells that have developed resistance to them. In particular, the risk of such resistance developing is increased where the chemotherapeutic agent is not administered in the correct dose and/or according to the preferred regimen.
Ultimately, the development of resistance has meant a loss of some hitherto useful chemotherapeutic agents from the armoury of therapeutic agents used for treating various types of infections or cancer, and, in some cases, a lack of any means of treating some multi-resistant infections.
The correct dose and regimen of a chemotherapeutic agent will result in an effective percentage of a population of infective agent or parasitic cell being killed or inhibited so that only a non-viable population remains.
Normally, killing or inhibiting an effective percentage of a population of infective agents or parasitic cells, such that only a non-viable population remains following a course of treatment, requires dosing regimens of chemotherapeutic agents that are spread over an extended period of time, such as a 7 to 10-day period. This presents problems as patients can find it difficult to remember to take their medication over such a long period of time. Even more problematic is the fact that many patients can feel better almost as soon as they start taking the medication, despite the fact that the treatment is not complete and an effective percentage of a population of infective agents or parasitic cells have not yet been killed or inhibited. Because they feel better, patients frequently stop taking the medication prematurely, which leads to a relapse of the condition. Such incomplete treatment also increases the risk of the infective agents or parasitic cells acquiring resistance to the chemotherapeutic agent.
Antibiotics are good examples of chemotherapeutic agents which suffer from the above mentioned problems.
Thus, it is an object of the present invention to solve the aforementioned problems by providing chemotherapeutic agents in compositions which control the release of the agents, thereby enhancing the efficacy of the agents compared to the efficacy of the same chemotherapeutic agents when they are administered in the usual way in conventional compositions.
It is a further object of the present invention to make chemotherapeutic agents effective against more infections or conditions, particularly those which are difficult to treat when the agents are used in the conventional manner.
According to a first aspect of the present invention, a composition comprising a chemotherapeutic agent is provided, wherein the composition provides a therapeutic effect over a period of at least 8 hours following administration and the release of the chemotherapeutic agent from the composition over that period is controlled to provide an optimised effect.
Preferably, the compositions of the invention are administered orally. The compositions may include one or more chemotherapeutic agents. The compositions may also include one or more further pharmaceutically active agents which provide a therapeutic effect, in addition to the chemotherapeutic agent.
The exact nature of the optimised effect will depend upon the chemotherapeutic agent included in the composition and/or will depend upon the condition to be treated.
In the case of some chemotherapeutic agents, the optimised effect is observed where the plasma concentration of the agent is maintained at a constant level over the period of treatment. In such cases, it will clearly be desirable for the plasma concentration to be sufficient for the agent to have the desired therapeutic effect,
whilst being low enough to avoid adverse side effects or to keep such side effects to a minimum.
Other chemotherapeutic agents are most effective when they are administered to provide plasma concentrations with spikes or peaks and troughs. In the case of such agents, the optimised effect will be achieved by the intermittent release of the chemotherapeutic agent from the composition, so that the plasma concentration fluctuates in a controlled manner, providing "on" and "off periods.
The compositions of the present invention allow chemotherapeutic agents to be administered in reduced numbers of doses, whilst at the same time ensuring that the therapeutic effect of each dose is optimised. Each dose will have an effect over a period of at least 8 hours, and preferably over a period of 8 hours, 12 hours or 24 hours. These periods of effect mean that the doses may be conveniently taken three times, twice or once a day to provide 24-hour therapeutic effect without disruption to normal sleep patterns.
The effect of the chemotherapeutic agent is greatly enhanced by avoiding periods during which treatment is either not optimised or is temporarily interrupted. This increase in efficacy allows the overall dose of chemotherapeutic agent required for the desired therapeutic effect to be reduced. It may also reduce the period over which the chemotherapeutic agent must be administered in order to achieve he desired therapeutic effect.
Normally, killing or inhibiting an effective percentage of a population of infective agents or parasitic cells requires the administration of chemotherapeutic agents over a period of several days, for example over a 7 to 10-day period. It has been found that the compositions according to the present invention can have the same effect over a shorter period of time than the same chemotherapeutic agent when it is administered in conventional compositions. In a preferred embodiment of the present invention, an effective percentage of the population of infective agents or parasitic cells are killed or inhibited following treatment over a period of just 4, 3, 2 or 1 days.
Preferably, the release of the chemotherapeutic agent from the compositions according to the present invention is controlled or delayed in order to achieve the desired release profile and plasma concentrations by employing known measures, including controlled release coatings and matrices. Such coatings and matrices are well known to the person skilled in the art. Materials commonly used to provide sustained release coatings include hydrophobic polymers such as ethylcellulose, polyvinylacetate, polymers or copolymers of acrylates or methacrylates, and mixtures thereof, and such coating materials are commercially available as Kollicoat®, Aquacoat®, Surelease®, Ethocel® and Methocel®. Materials commonly used to provide sustained release matrices in oral solid dosage forms include excipients which are hydrogel formers such as HPMC, HPC, xanthan gum, alginates, polyvinyl acetate and polyvinylpyrrolidone, and such matrix excipients are commercially available as Timerx®, Kollidon® and Methocel®.
In a preferred embodiment of the invention, the compositions comprise one or more coatings and/ or excipients which control the release of the chemotherapeutic agent.
In one embodiment, the pharmaceutical composition is provided in the form of a layered oral solid dosage form. Such layered tablets are known to the skilled person. The different layers of the dosage form may provide release of the chemotherapeutic agent at different times or at different rates, using known coatings or matrices. Alternatively or additionally, the different layers may include different chemotherapeutic agents or different forms of the same chemotherapeutic agent, these different agents or forms being released at different rates or having different rates of onset of their therapeutic effect, for example as a result of differing absorption and/or degradation characteristics.
Oral delivery of solid dosage forms is more convenient and accepted than other modes of administration. However, the manufacture, dispensing and administration of solid dosage forms are not without associated problems and drawbacks.
Where large doses of active agents are to be administered, tablets can become unacceptably large, being uncomfortable or impossible to swallow, especially for the elderly or the young.
There are also many patients who are unable or unwilling to take conventional orally administered dosage forms. For some patients, the perception of unacceptable taste or mouth feel of a solid dosage form leads to a gag reflex action that makes swallowing difficult or impossible. Other patients, e.g., paediatric and geriatric patients, find it difficult to ingest typical solid oral dosage forms, for example due to their size.
Other patients, particularly elderly patients, have conditions such as achlorhydria which hinder the successful use of oral solid dosage forms. Achlorhydria is a condition wherein there is an abnormal deficiency or absence of free hydrochloric acid in the gastric secretions of the stomach. This condition hinders the disintegration and/or dissolution of oral solid dosage forms, particularly dosage forms with large or insoluble excipient components.
Due to the disadvantages of the drug delivery methods discussed above, the compositions of the present invention may be prepared in multiparticulate form, such as the compositions disclosed in International Publication No. WO 03/020241. Preferably, the compositions according to the present invention are pharmaceutical compositions for gastrointestinal deposition and comprise a non- compressed, free-flowing plurality of particles comprising the chemotherapeutic agent and a pharmaceutically acceptable carrier. Preferably, the particles have a mean diameter of greater than lOμm, greater than 20, 50 or lOOμm.
Preferably, the particles of the invention comprise at least about 40, 50, 60, 70, 80 or 90% by weight chemotherapeutic agent.
Preferably, greater than about 80, 85, 90, 95, 96, 97, 98 or 99% of a dose of the multiparticulate composition of the present invention is deposited in the gastrointestinal tract.
In some embodiments, the composition comprises two or more populations of particles, each population releasing the chemotherapeutic agent at different rates to produce different release profiles. In other embodiments, the composition includes just one population of particles, all of which are essentially the same and provide the same desired release profile.
A dose of multiparticulate composition according to the present invention is preferably from about O.Olmg to about 1.5g in weight, depending on the dose of the chemotherapeutic agent being delivered. Preferably, the dose is from about 1 mg to about lOOmg, or from about lOmg to about 50mg.
Preferably, the dose is administered to the tongue, most preferably towards the front of the tongue behind the teeth, where it can be easily swallowed with or without the need for an additional fluid. However, the invention does contemplate delivery to any portion of the tongue, taking into account, e. g., the taste sensations of different sections of the tongue and/or individual patient preference associated with comfort, e. g. mouth position.
Preferably, the mean diameter of the particles is of a size which minimizes their capacity to be inhaled into the lower lung. Typically, the mean particle size of the particles is greater than lOμm, preferably greater than about 50μm or greater than about 75μm. In certain embodiments of the invention, the mean particle size range of the particles is from about lOOμm to about lmm, preferably from about 50μm to about 500μm. The particles referred to here may be granulated particles made up of smaller particles or agglomerates of smaller particles. These smaller particles are preferably nanoparticles, with a diameter of between approximately 10 nanometers and approximately 1 micron, and more preferably with a diameter of approximately 100 nanometers. The use of such small particles in the compositions of the present invention is particularly attractive where the particles in question comprise an active agent which is poorly soluble in water, such as ciprofloxacin.
In preferred embodiments, greater than 80% of the particles have the above disclosed diameter (not mean diameter), e.g. 80% of the drug particles have a diameter of greater than lOμm, or a diameter of from about lOOμm to about lmm. In other embodiments, greater than about 90% of the drug particles have the above disclosed diameter.
Preferably, the multiparticulates comprise a pharmaceutically acceptable excipient. The excipient preferably does not comprise more than about 60% by weight of the composition, more preferably not more than about 50%, more preferably not more than about 40%, more preferably not more than about 20%, and most preferably not more than about 10% by weight of the composition.
Fast melt compositions are known and they are typically in the form of tablets or lozenges that dissolve or disperse in a patient's mouth within a minute without the need of water or chewing. Drug delivery compositions which exhibit fast melt properties can improve patient compliance due to the ease of swallowing as well as the absence of a need for the co-administration of water or another fluid. Further, fast melt systems can be formulated so as to have a superior taste and improved accuracy of dosing as compared to liquid preparations.
Fast melt drug multiparticulate compositions have been developed to facilitate the oral administration of oral agents to patients normally having difficulty ingesting conventional solid oral dosage forms, and such compositions are, for example, disclosed in International Publication No. WO 03/074029.
In one embodiment of the present invention, the compositions are fast melt compositions. Preferably, the compositions of the present invention are multiparticulate and combine the benefits of the free flowing multiparticulate compositions described above with those of fast melt drug compositions.
Thus, in a preferred embodiment of the present invention the multiparticulate pharmaceutical compositions described above further comprise a water-soluble
excipient and the composition is capable of dissolving or dispersing in a subject's mouth within 1 minute after ingestion without the co-administration of a fluid.
Preferably, the water-soluble excipient has a negative heat of solution. A significant advantage associated with such excipients, when administered via the oral cavity, is that the local cooling caused by the water-soluble excipient dissolving in saliva serves to mask the taste of the active agent in a manner which does not delay the release, or dissolution of the active agent itself.
Both non-fast melt and fast melt multiparticulate compositions according to the present invention are preferably arranged for direct, un-encapsulated administration to a patient's oral cavity. It is also preferred for the particles to be non-compressed.
The multiparticulate pharmaceutical compositions (both fast melt and non-fast melt compositions) of the present invention can be formulated in order to provide the aforementioned release profile and plasma concentrations by employing controlled release coatings and/or matrices. The skilled person would be aware of which materials to use and how much of them to use in order to prepare particles which release their payload of chemotherapeutic agent in the desired manner.
In one embodiment, the fast melt multiparticulate compositions have at least two coatings, a water-soluble excipient coating and a delayed release excipient coating. Preferably the water-soluble coating is the outermost coating.
A wide variety of chemotherapeutic agents may be incorporated into the compositions of the present invention.
Suitable antibacterial agents include acrosoxacin, amifloxacin, amoxycillin, ampicillin, aspoxicillin, azidocillin, azithromycin, aztreonam, balofloxacin, benzylpenicillin, biapenem, brodimoprim, cefaclor, cefadroxil, cefatrizine, cefcapene, cefdinir, cefetamet, cefmetazole, cefprozil, cefroxadine, ceftibuten, cefuroxime, cephalexin, cephalonium, cephaloridine, cephamandole, cephazolin, cephradine, chlorquinaldol, chlortetracycline, ciclacillin, cinoxacin, ciprofloxacin,
clarithromycin, clavulanic acid, clindamycin, clofazimine, cloxacillin, danofloxacin, dapsone, demeclocycline, dicloxacillin, difloxacin, doxycycline, enoxacin, enrofloxacin, erythromycin, fleroxacin, flomoxef, flucloxacillin, flumequine, fosfomycin, isoniazid, levofloxacin, mandelic acid, mecillinam, metronidazole, minocycline, mupirocin, nadifloxacin, nalidixic acid, nifuirtoinol, nitrofurantoin, nitroxoline, norfloxacin, ofloxacin, oxytetracycline, panipenem, pefloxacin, phenoxymethylpenicillin, pipemidic acid, piromidic acid, pivampicillin, pivmecillinam, prulifloxacin, rufloxacin, sparfloxacin, sulbactam, sulfabenzamide, sulfacytine, sulfametopyrazine, sulphacetamide, sulphadiazine, sulphadimidine, sulphamethizole, sulphamethoxazole, sulphanilamide, sulphasomidine, sulphathiazole, temafloxacin, tetracycline, tetroxoprim, tinidazole, tosufloxacin, trimethoprim and salts or esters thereof.
Suitable antifungal agents include bifonazole, butoconazole, chlordantoin, chlorphenesin, ciclopirox olamine, clotrimazole, eberconazole, econazole, fluconazole, flutrimazole, isoconazole, itraconazole, ketoconazole, miconazole, nifuroxime, tioconazole, terconazole, undecenoic acid and salts or esters thereof.
Suitable antiprotozoal agents include acetarsol, azanidazole, chloroquine, metronidazole, nifuratel, nimorazole, omidazole, propenidazole, secnidazole, sineflngin, tenonitrozole, temidazole, tinidazole and salts or esters thereof.
Suitable antiviral agents include acyclovir, brivudine, cidofovir, curcumin, desciclovir, 1-docosanol, edoxudine, fameyclovir, fiacitabine, ibacitabine, imiquimod, lamivudine, penciclovir, valacyclovir, valganciclovir and salts or esters thereof.
Cancer chemotherapeutic drugs fall into the following categories: alkylating agents, antimetabolites, anthracyclines, plant alkaloids, topoisomerase inhibitors, and antitumour agents.
Suitable alkylating agents include: alkyl sulfonates such as busulfan; ethyleneimines and methylmelamines such as hexamethylmelamine and thiotepa; nitrogen mustards
such as cyclophosphamide, mechlorethamine, uramustine, melphalan and chlorambucil; nitrosoureas such as carmustine and streptozocin; triazenes such as dacarbazine and temozolomide; and other agents such as cisplatin, carboplatin and ifosfamide.
Suitable anti-metabolites include: folic acid analogues such as methotrexate; purine analogues such as azathioprine, mercaptopurine and fludarabine; and pyrimidine analogues such as 5-fluorouracil.
Suitable plant alkaloids and terpenoids include: vinca alkaloids such as vincristine, vinblastine, vinorelbine and vindesine; taxanes such as paclitaxel and docetaxel; and podophyllotoxin .
Suitable topoisomerase inhibitors include: type I topoisomerase inhibitors such as irinotecan and topotecan; and type II inhibitors such as amsacrine, etoposide, etoposide phosphate and teniposide.
Suitable antitumour antibiotics include: actinomycin such as dactinomycin; anthracyclines such as doxorubicin, daunorubicin and epirubicin; and others such as bleomycin; plicamycin and mitomycin.
Mixtures of antibacterial agents, mixtures of antifungal agents, mixtures of antiviral agents, mixtures of antiprotozoal agents, mixtures of cancer chemotherapeutic agents and mixtures of agents from two or more of these categories may be included in the compositions of the present invention.
The coatings and/or matrix excipients that are included in the compositions of the present invention will be selected to complement the chemotherapeutic agent(s) also included, and must be chosen for their ability to control the release of the chemotherapeutic agent(s) to provide the desired release profile. This will involve providing a therapeutic effect for a period of at least 8 hours from administration of the composition, as well as providing desired local and/or plasma concentrations.
In a preferred embodiment of the present invention, the chemotherapeutic agent will rapidly reach a therapeutic concentration following administration of the composition. In some cases, this will involve selection of a particularly active form of the chemotherapeutic agent, a form which is readily soluble in an aqueous environment such as that to which the composition is exposed to following oral administration, and/ or a form which is quickly absorbed via the gastro-intestinal tract into the bloodstream (for systemically active chemotherapeutic agents).
Various known techniques may be used to prepare chemotherapeutic agents in forms which are more readily dissolved in an aqueous environment. Examples of such techniques are disclosed in WO 2004/011537 and WO 2005/073296, WO 2005/07330, WO 2005/075546 and WO 2005/075547.
The techniques disclosed in the prior art involve solubilising otherwise poorly soluble active agents and they are useful because they enable compositions to be formulated with otherwise "difficult" chemotherapeutic agents, such as those in their base form which are normally only poorly soluble. Normally, the poor solubility of the base form of some pharmaceutically active agents severely restricts their use, with salt forms being employed instead. However, the base form often exhibits faster onset of the therapeutic effect and, in some cases, better absorption. Fluoroquinolones, such as ciprofloxacin, are an example of a group of therapeutic agent which are usually used in their salt form because the base form is usually not soluble enough. However, the base form has a number of advantages, such as a faster onset of action and better absorption, in particular better absorption to the brain. As a result, the base form may be more effective than the commonly used salt form when treating meningitis and other infections of the cerebrospinal fluid.
Thus, in a preferred embodiment of the present invention, the compositions comprise the base form of the chemotherapeutic agent. Where necessary, a solubilisation technique is used, in order to enhance the solubility of the base form. In a particularly preferred embodiment, the chemotherapeutic agent is ciprofloxacin base.
Alternatively or additionally, the chemotherapeutic agent may be provided in the form of nano-sized particles. This will also enhance solubilisation and absorption. Known techniques from the art may be used to produce these ultra-fine particles.
5 In a further embodiment of the present invention, the composition includes a therapeutically active agent other than the chemotherapeutic agent. Such therapeutically active agents are preferably selected to have an effect which complements that of the chemotherapeutic agent. For example, where the composition of the present invention is intended for treating an infection, the
10 composition may include a chemotherapeutic agent selected from those mentioned herein, together with an additional therapeutic agent which is known for use in treating the underlying cause of the infection, such as a homeopathic remedy, and/or an additional therapeutic agent which treats the symptoms of the infection or a related condition. t5
Alternatively, the chemotherapeutic agent may be combined with an agent with a prophylactic effect to complement the therapeutic effect of the chemotherapeutic agent. This would mean that the single composition could be administered to a subject even before a final diagnosis of the subject's condition has been made. For
20 example, if a subject has been exposed to an infectious agent, such as tuberculosis, but it has not yet been established whether that subject is infected, a combined therapeutic/prophylactic composition could be effectively administered without delay. In the case of tuberculosis, a chemotherapeutic agent such as ciprofloxacin could be combined with a preventative agent such as isoniazid. 5
It has also now been discovered that it is also possible to increase the efficacy of a chemotherapeutic agent by administering it in conjunction with an enhancing agent.
An enhancing agent, as referred to herein, is an agent which is capable of increasing 0 the efficacy of the chemotherapeutic agent. The enhancing agent must be selected to complement the chemotherapeutic agent and the precise manner in which the enhancing agent increases the efficacy of the chemotherapeutic agent will depend on the way in which the chemotherapeutic agent works, including the nature of the
target against which it is effective (i.e. the specific infective agent or parasitic cell), as well as the defences that such a target or the organism being treated may have against attack from the chemotherapeutic agent.
For example, the enhancing agent may act as a sensitising agent. Preferably, a sensitising agent is capable of disrupting the integrity of a parasitic cell or infective agent, or is capable of disrupting the parasitic cell's or infective agent's defences against attack by a chemotherapeutic agent. Accordingly, a sensitising agent can render a parasitic cell or infective agent more vulnerable to attack by a chemotherapeutic agent.
A targeting agent is an agent which directs the actions of a chemotherapeutic agent to the parasitic cells or to the infective agents. This may for example, be achieved by the targeting agent attracting the chemotherapeutic agent after selectively binding to the parasitic cells or infective agents. Alternatively, the targeting agent may work by selectively sensitising the parasitic cells or infective agents to attack from a chemotherapeutic agent. Such selective sensitisation means that, by subsequently administering the chemotherapeutic agent at a dose below that at which it is normally effective, the effect of the chemotherapeutic agent may be focussed on and/or limited to the sensitised parasitic cells or infective agents.
The enhancing agent may alternatively act by extending the period of residence of the chemotherapeutic agent in the subject's body following administration. This may be achieved, for example, by preventing or slowing the body's elimination of the chemotherapeutic agent. Probenesid is an example of an agent which can act as an enhancing agent in this way, as it prevents antibiotics and other chemotherapeutic agents from being excreted by the kidneys. This means that the agents remain in the body for longer and so may have a longer period of effect following administration. Another example of such an enhancing agent is cilostatin.
The use of an enhancing agent can, therefore, increase the efficacy of the chemotherapeutic agent, thereby reducing the dose of chemotherapeutic agent required in order to achieve a desired therapeutic effect and/or reducing the period
over which the chemotherapeutic agent must be administered in order to kill or inhibit an effective percentage of a population of infective agents or parasitic cells. In addition, the use of an enhancing agent can ensure that the effect of the chemotherapeutic agent is limited to the infective agents or parasitic cells it is desired to kill or inhibit.
Thus, according to a further aspect of the invention, there is provided a pharmaceutical composition comprising an enhancing agent and a chemotherapeutic agent, wherein the enhancing agent increases the efficacy of the chemotherapeutic agent and the composition is prepared for separate, sequential or simultaneous administration of the enhancing agent and the chemotherapeutic agent.
In some embodiments, the enhancing agent can have a therapeutic effect independent of that of the chemotherapeutic agent. Indeed, in one preferred embodiment, the enhancing agent is also a chemotherapeutic agent. Preferably, the actions of the enhancing agent are selectively directed to parasitic cells or infective agents,- and preferably not to host cells.
The enhancing agent can be administered before, after or at the same time as the chemotherapeutic agent. The timing of the administration is dictated by the nature of the interaction between the enhancing agent's activity and that of the chemotherapeutic agent.
For example, where the enhancing agent acts by preparing the target agent or cell, or by preparing the subject organism, for the administration of the chemotherapeutic agent, it will clearly be desirable for the enhancing agent to be administered in such a way that it reaches an effective concentration before the chemotherapeutic agent. Where the enhancing agent protects the chemotherapeutic agent against defensive mechanisms of the subject organism or of the infective agent or parasitic cell to be killed or inhibited, it will be desirable for the concentration of the enhancing agent to be maintained at an effective level for as long as the chemotherapeutic agent is at an effective concentration.
Accordingly, in a preferred embodiment of the present invention, the pharmaceutical composition comprising a chemotherapeutic agent and an enhancing agent provides controlled release of the agents to provide an optimised effect.
In some embodiments of the present invention, the enhancing agent is released from the composition so that it reaches an effective concentration in the subject to be treated before the chemotherapeutic agent reaches an effective concentration. Figure 1 illustrates an example of a release profile for a chemotherapeutic agent and an enhancing agent, where the enhancing agent is released prior to the chemotherapeutic agent.
In such embodiments, the delay between the enhancing agent reaching its effective concentration and the chemotherapeutic agent reaching its effective concentration should be selected to optimise the ability of the enhancing agent to increase the efficacy of the chemotherapeutic agent.
Where the enhancing agent is released before the chemotherapeutic agent, it is believed that the aforementioned delay provides time for the enhancing agent to have its effect on the infective agents or parasitic cells, or their defences, which in turn leads to the increase in the efficacy of the chemotherapeutic agent when it is subsequently released. Therefore, the length of delay should be selected based upon the length of time required for the enhancing agent to exert its effects on the infective agents or parasitic cells, or their defences. Not wishing to be restricted further, but in the interest of clarity, the delay may be between about 1 and about 480 minutes, between about 5 and about 240 minutes, between about 10 and about 120 minutes or between about 15 and about 60 minutes.
In a preferred embodiment of the present invention, the enhancing agent and the chemotherapeutic agent are administered to the subject at the same time, most preferably in the same composition. The composition is formulated to control the release of the agents, so that the enhancing agent is released before the chemotherapeutic agent and the release of these agents is staggered to provide the
optimum delay for the enhancing agent to increase the efficacy of the chemotherapeutic agent.
As touched upon above, the administration of some chemotherapeutic agents preferably produces peaks followed by troughs in the concentration, rather than a constant concentration being maintained over a period of time. Figure 2 shows an example of a release profile providing successive concentration peaks of a chemotherapeutic agent in combination with a constant concentration of an enhancing agent.
However, in some embodiments of the present invention, the enhancing agent may better enhance the activity of the chemotherapeutic agent if it too is released to produce concentration peaks. Figure 3 shows a further example of a possible release profile providing staggered peaks in the concentration of enhancing agent and chemotherapeutic agent.
In some embodiments of the present invention, the release profile of the chemotherapeutic agent and or the release profile of the enhancing agent is/are repeated in a cyclical manner. Figure 2 shows a single such cycle, whilst Figure 3 shows three cycles.
Preferably, each cycle occurs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 times a day over the period of 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 days. Preferably, the period is 1, 2, 3 or 4 days. Preferably the cycles are spread evenly throughout the day.
Each cycle can be produced by separate dosing. However, it is difficult to maintain the desired regularity and frequency of dosing by controlling the ingestion of the enhancing agent and the chemotherapeutic agent, particularly if the subject to be treated is an infant or an elderly person. Such regimens are also inconvenient to maintain, and it is easy to miss a timed dose. Additionally, it is difficult to spread the multiple doses equally over a 24-hour period without disrupting sleep. Hence,
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even if the subject being treated can stick to the strict and complicated regimen, ingested doses are usually only spread evenly throughout the subject's waking hours.
Accordingly, in a preferred embodiment of the present invention, the pharmaceutical composition comprising a chemotherapeutic agent and an enhancing agent provides a therapeutic effect over a period of at least 8 hours following administration and the release of the agents over that period is controlled to provide an optimised effect.
Preferably, a single dose of the composition according to the present invention is formulated so that the release profile of the chemotherapeutic agent and or the release profile of the enhancing agent is/are repeated in a cyclical manner.
As referred to herein, the concentration of the chemotherapeutic agent and of the enhancing agent refers to the plasma concentration where the agents must be absorbed into the bloodstream in order to have their desired effect. Alternatively, if the agents have a local (rather than systemic) effect, the references to concentration relate to the local concentration of the agents.
The enhancing agents co-administered with a given chemotherapeutic agent are selected on the basis of how the efficacy of the chemotherapeutic agent could be enhanced.
Many infective agents and parasitic cells have developed resistance to chemotherapeutic agents by developing various defences against attack. For example, some strains of bacteria have become resistant to β-lactam antibiotics by producing β-lactamase, an enzyme that cleaves the β-lactam ring from β-lactam antibiotics, thereby rendering them ineffective. Accordingly, an agent that inhibits the action of β-lactamase would be an appropriate enhancing agent to administer with the chemotherapeutic agents in the compositions of the present invention.
Accordingly, in one embodiment of the present invention the enhancing agent is an anti-β-lactamase, most preferably clavulanate, or a salt thereof. In such an
embodiment of the present invention the chemotherapeutic agent is preferably a β- lactam antibiotic such as cloxacillin, flucloxacillin, oxacillin, dicloxacillin, methicillin, nafcillin, ampicillin, pivampicillin, talampicillin, bacampicillin amoxycillin, carbenicillin, ticarcillin, azlocillin or mecillinam, most preferably amoxicillin.
Preferably, the β-lactamase inhibiting enhancing agent is administered before the β- lactam antibiotic.
Alternatively, the enhancing agent may act as a sensitising agent by directly weakening the infective agent or parasitic cell. For example, the enhancing agent can stimulate the host's immune response (i.e. the immune response of the subject being treated) to attack the parasitic cell or infective agent. For example, a monoclonal antibody (such as retuximab) may be a suitable enhancing agent. Retuximab is useful for treating B-cell non-Hodgkin lymphoma as it binds specifically to B cells, thereby inducing antibody-dependent cell-mediated cytotoxicity or complement dependent cytotoxicity (CDC) directed at B-cells. Cells weakened by the immune response to retuximab are more easily killed, or their growth and reproductive abilities attenuated, by a chemotherapeutic agent.
Steroidal emulsifiers such as squalamine are another group of agents that can act as sensitising agents. Steroidal emulsifiers are able to weaken cells by creating holes in their plasma membranes. The contents of the cell is able to leak from these holes and so destabilise the electrochemical gradient across the cell membrane, which is crucial for the proper functioning of any cell. Additionally, these holes make the bacterial cell more permeable to, for example, chemotherapeutic agents.
Thus, in a further embodiment of the present invention, the enhancing agent is a monoclonal antibody (such as retuximab), or a steroidal emulsifier (such as squalamine). Any chemotherapeutic agents can be used in association with these enhancing agents. However, in a preferred embodiment, the chemotherapeutic agents are those which target intracellular sites. This is particularly preferred when, in the case of steroidal emulsifiers, the permeability of the bacterial cell is increased
by the enhancing agent. For example, the chemotherapeutic agent may be a DNA gyrase inhibitor, examples of which are nalidixic acid, cinoxacin, ciprofloxacin, oxolinic acid and acrosaxacin. Preferably the chemotherapeutic agent is ciprofloxacin.
Preferably, the monoclonal antibody or steroidal emulsifier enhancing agent is administered before the chemotherapeutic agent.
If the enhancing agent is capable of selectively weakening infective agents or parasitic cells (e.g. squalamine selectively attacks bacterial plasma membranes) then low doses of even non-specific chemotherapeutic agents can be used in the compositions of the present invention. Low doses of chemotherapeutic agents can be chosen to be low enough so as not to adversely affect the host's cells but high enough so as to be lethal for the weakened or sensitised parasitic cells or infective agents. In this way the enhancing agent can act as a targeting agent for the chemotherapeutic agent.
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