Field of the Invention

This invention relates to the use of acetazolamide and methazolamide for the control and monitoring of thrombosis and clotting. In particular, the invention relates to acetazolamide and methazolamide and their use as anti -thrombotic agents and for the control and monitoring of thrombosis and clotting. Background of the Invention

Platelets are central to the process of haemostasis, rapidly aggregating at sites of blood vessel injury and acting as coagulation nidus sites. Platelets play complex roles in haemostasis and arterial thrombosis, rapidly adhering to sub-endothelial structures and to each other to generate a platelet aggregate which is stabilised by the local production of thrombin and subsequently fibrin. Upon interaction with a sub- endothelial matrix platelets are transformed into balloon-like structures as part of the haemostatic response, and this is critical for normal haemostasis and for thrombosis. Importantly, thrombosis is mediated by two distinct but concurrent and inter-related mechanisms: platelet activation and blood coagulation (clotting). Interestingly, platelet ballooning sits at the interface between these two, providing a mechanism whereby the coagulation process can occur on the massively enlarged surface of the platelet balloon (the procoagulant response).

While clotting is important in the case of injury, if clotting occurs within the body when not required, it can lead to conditions such as a stroke and heart attack (myocardial infarction). If a clot, or thrombus, blocks the smooth flow of blood, the result, called thrombosis, can be serious and even cause death. Diseases arising from clots in blood vessels include heart attack and stroke, among others. These disorders collectively are the most common cause of death and disability in the developed world.

Furthermore, if an individual is going to be treated where bleeding is likely to occur, it is crucial that medical practitioners are aware of the clotting characteristics of that individual. Currently if there is a risk of bleeding, platelet packs are held on standby and if they are not required then the packs are disposed of. This is costly and also wasteful.

Thrombosis sometimes occurs for no apparent reason. However, the risk of developing thrombosis is increased in circumstances where vascular damage occurs, e.g. surgical procedures or interventions, inactivity, blood vessel damage, pregnancy, obesity or medical and genetic conditions that cause the blood to clot more easily than normal. Most importantly here, the most common causes of vascular damage that induce platelet activation are those that occur secondary to atherosclerosis, which occurs principally in the coronary arteries and the cerebral arteries, and underlies heart attacks and stroke. Other common causes of vascular damage leading to thrombosis include cancer treatments, heart and lung disease, infectious diseases, such as hepatitis, inflammatory conditions, such as rheumatoid arthritis, thrombophilia and Hughes syndrome, amongst others. Platelets are also incorporated into the structure of venous thrombi, such as in deep vein thrombosis, and are therefore causally involved in the development of this condition.

Coronary artery disease (CAD) is the most common form of heart disease. It occurs when arteries in the heart are blocked, leading to complications including angina (chest pain) if the heart does not have enough oxygen or heart attack if the heart does not get any oxygen at all. Over many years, plaque builds up on artery walls. Plaque is a sticky substance that can narrow and clog the arteries, slowing the flow of blood. This condition is called atherosclerosis and can occur anywhere in the body, but it usually affects large and medium-sized arteries. Sometimes plaque in an artery can rupture and the body's repair system in turn creates a blood clot to heal the wound. The clot, however, can block the artery, leading to either a heart attack or stroke.

Many surgical interventions, including coronary angioplasty and percutaneous coronary intervention can lead to procedure-related thrombotic complications. The current strategy to deal with these procedures involves the use of aspirin and a P2Yi ₂ blocker combined with a low-molecular weight heparin or a thrombin inhibitor such as bivalirudin. Cheaper drugs, with superior safety profile relative to conventional adjunct agents such as bivalirudin, are desirable. Antithrombotic agents, commonly known as blood thinning agents, are drugs that reduce the formation of blood clots (thrombi). Antithrombotics can be used therapeutically for prevention (primary prevention, secondary prevention) or treatment of a dangerous blood clot (acute thrombus). Current antithrombotic drugs include anticoagulant drugs such as heparin and warfarin and antiplatelet drugs such as aspirin, clopidogrel, dipyridamole or prasugrel. It is known that some patients are intolerant to some drugs, e.g. it is estimated that between 0.3% and 1% of the population are aspirin intolerant.

The use of antithrombotic drugs carries a risk of bleeding and haemorrhagic complications and requires regular monitoring. This monitoring is even more important for long-term or chronic therapy. Anticoagulation, especially in some patient groups (e.g. elderly patients) often needs an assessment of the overall risk/benefit ratio.

There are particular pharmacokinetic disadvantages associated with the current antiplatelet treatments. Firstly, aspirin, clopidogrel and prasugrel are all irreversible inhibitors, and as a result, their effects cannot be readily washed out. This can present issues, for example, when patients are overdosed with the drugs, meaning that reversal of the bleeding problems caused can be very slow. Secondly, both clopidogrel and prasugrel are pro-drugs of the actual active agent. There are therefore limitations associated with these drugs, particularly in the treatment of individuals with liver dysfunction (relatively common in more elderly patients). This can also be the cause of significant 'tolerance' to these drugs, where individuals do not properly metabolise the drugs, at appropriate rates, to generate the active metabolite.

Alternative options to known antithrombotic drugs are highly desirable.

Acetazolamide (I), a carbonic anhydrase inhibitor and a water channel inhibitor, usually sold under the name Diamox, is beneficial in the control of fluid secretion (e.g., some types of glaucoma), in the treatment of certain convulsive disorders (e.g. epilepsy) and in the promotion of diuresis in instances of abnormal fluid retention (e.g., cardiac edema). Indications and usage of acetazolamide include adjunctive treatment of: edema due to congestive heart failure, drug-induced edema; centrencephalic epilepsies (petit mal, unlocalized seizures), chronic simple (open- angle) glaucoma, secondary glaucoma and preoperatively in acute angle-closure glaucoma where delay of surgery is desired in order to lower intraocular pressure and for the treatment of acute altitude sickness.

(I)

Acetazolamide is usually administered by mouth (tablets or controlled release capsules) or by intravenous injection (500mg of sterile powder requiring reconstitution). Intramuscular injection is preferably avoided because of alkalinity. The dosage employed usually ranges from 250mg to lg acetazolamide for 24 hours.

Methazolamide (II), is indicated in the treatment of ocular conditions where lowering intraocular pressure is likely to be of therapeutic benefit, such as chronic open-angle glaucoma, secondary glaucoma and preoperatively in acute angle-closure glaucoma where lowering the intraocular pressure is desired before surgery. It is available as 25 mg and 50 mg tablets.

(Π)

There is a medical need for both the treatment and prevention of unnecessary clotting and for the monitoring of a patient's clotting characteristics. The present invention seeks to overcome the problems with the prior art by providing antithrombotic agents, for the suppression of clot formation in susceptible individuals and which can also be used to monitor clot formation.

Summary of the Invention

The present invention relates to the use of acetazolamide or methazolamide for the therapy (including treatment and prophylaxis or preventative therapy) of clot formation and thrombosis. Acetazolamide and methazolamide can be used as antithrombotic agents. These agents may be particularly useful for the treatment or prevention of thrombosis and diseases arising from clots in blood vessels, e.g. heart attack and stroke, amongst others. The thrombosis or risk of thrombosis may have any cause, e.g. atherosclerosis, surgical procedure or others, but the inhibitor may be particularly useful in the management of coronary artery disease (CAD) and stroke.

Preferably the agent is acetazol amide. Acetazolamide has actions as a carbonic anhydrase inhibitor and a water channel blocker and both of these activities may contribute to, and may be necessary for its antithrombotic activity. Methazolamide is also preferred.

The invention is based at least in part on data showing that acetazolamide is able to markedly diminish in vitro platelet ballooning and also act to potently inhibit thrombus formation in vivo. Acetazolamide can block platelet ballooning, and thereby affect platelet activation and also inhibit the procoagulant response of platelets. This places it in an unusual place as an antithrombotic therapeutic, since this dual action will effectively counteract both aspects of the thrombotic mechanism (platelet activation and blood coagulation or clotting) providing an effective 'dual' antiplatelet and anticoagulant activity in vivo.

Acetazolamide has actions as both a carbonic anhydrase inhibitor and a water channel blocker and both of these activities are likely to contribute to, and be necessary for, its antithrombotic activity.

Our data also show that, at equivalent concentrations, methazolamide has a greater ability to block platelet ballooning than acetazolamide. Methazolamide may therefore be useful as a drug with more potent platelet procoagulant activity than acetazolamide. This may have additional benefits, such as the potential for using lower doses and the reduction or avoidance of side effects. The data also shows (Fig 3) that methazolamide' s in vitro overall profile is different from the profile shown by aspirin and acetazolamide and may therefore provide a very useful antithrombotic alternative.

Furthermore, in vitro data shows that acetazolamide and methazolamide inhibit platelet procoagulant response by mechanisms distinct from aspirin. Consequently, acetazolamide and methazolamide can be used as alternatives to aspirin or as adjunct antithrombotic treatments, for example in patients with aspirin tolerance. The use of acetazolamide and methazolamide may also be advantageous due to better pharmacodynamics and pharmacokinetic profile at concentrations of equivalent clinical efficacy. In contrast to, for example aspirin, which blocks platelet function irreversibly (as explained above), the antithrombotic agents of the invention are reversible inhibitors. This is beneficial as it minimises the risk in potential overdose situations, since the activity of the drug will diminish with time much more rapidly than the activity of irreversible inhibitors, whose activity lasts for the lifetime of the platelet (7-10 days). Furthermore, the agents of the invention are not "prodrugs" and their activity is therefore less affected by metabolism than those drugs requiring metabolism to release the active metabolite. The potential variability of metabolism from patient to patient is well known.

Another aspect of the invention is therefore the use of acetazolamide as an antithrombotic agent in patients with known drug tolerance. In another aspect of the invention, methazolamide is used as an antithrombotic agent in patients with known drug tolerance. Acetazolamide and methazolamide are particularly useful for the treatment of patients with a tolerance to aspirin, clopidogrel or prasugrel. Preferably, the patients are aspirin tolerant.

In another aspect of the invention, acetazolamide or methazolamide can be used when the patient is also administered at least another drug. They can be used as an adjunct agent, in combination or by co-administration.

A further aspect of the invention is a test kit for testing blood clotting characteristics from an individual, said kit comprising a sample receiver and an agent of the invention, to add to a sample of blood contained within the sample receiver.

Preferably the test kit includes a sample receiver having a window to allow for observation of the clotting characteristics of the sample of blood contained in the sample receiver. It is preferred that the window of the sample receiver is arranged so that observation of the sample of blood can be carried out using image microscopy. The kit can include one or more further reagents to add to the sample of blood. Preferably at least one of the further reagents is an anticoagulant or an antiplatelet drug.

Another aspect of the invention is a method of monitoring clotting by adding acetazolamide or methazolamide to a blood sample and observing clotting characteristics of said sample over a period of time.

A further aspect of the invention provides for the use of acetazolamide or methazolamide to monitor clotting in a blood sample. Description of the Figures

Figure 1 shows that water entry drives platelet membrane ballooning and procoagulant spreading.

Figure 2 shows the effect of acetazolamide on thrombus formation in vivo in a mouse model system.

Figure 3 represents the pharmacological inhibition of human platelet procoagulant response to collagen by aspirin, acetazolamide at 2 concentrations and methazolamide.

Detailed description of an embodiment of the invention

Any suitable form of the active agent can be chosen. These include salts, prodrugs and active metabolites.

A preferred agent of the invention is acetazolamide. Methazolamide is also preferred.

Acetazolamide and methazolamide according to the invention are used as antithrombotic agents. Uses include but are not limited to: the treatment and prevention of clot formation, i.e. the treatment and prevention of thrombosis; therapy (prevention and treatment) of diseases arising from clots in blood vessels, e.g. heart attack and stroke. The thrombosis or risk of thrombosis may have any cause, e.g. atherosclerosis, a surgical procedure, inactivity, blood vessel damage, pregnancy, obesity or medical and genetic conditions that cause the blood to clot more easily than normal, cancer, some cancer treatments, heart and lung disease, infectious diseases, such as hepatitis, inflammatory conditions, such as rheumatoid arthritis, thrombophilia and Hughes syndrome. The thrombosis or risk of thrombosis may have no known cause. Surgical procedures or interventions that can lead to procedure-related thrombotic complications include, but are not limited to, coronary angioplasty and percutaneous coronary intervention. An agent of the invention is also useful to protect against these procedure-related thrombotic complications. Many of the common cardiovascular disorders (especially in elderly people) are linked to thrombosis. These include, but are not limited to, ischaemic heart disease, atrial fibrillation, valve disease, hypertension and atherosclerotic vascular disease.

The compounds described herein may be formulated for administration in any convenient way, and the invention therefore also includes pharmaceutical compositions comprising acetazolamide or methazolamide or pharmaceutically acceptable salts thereof together, if desirable, in admixture with one or more pharmaceutically acceptable diluents or carriers.

Any suitable route of administration can be used. For example, any of oral, intravenous, transdermal, topical, parenteral, ocular, rectal, vaginal, inhalation, buccal, sublingual and intranasal delivery routes may be suitable. For the purpose of the present invention, acetazolamide or methazolamide may be preferably administered by the intravenous or oral route. Transdermal administration is also preferred.

Pharmaceutical compositions of acetazolamide or a pharmaceutical salt thereof, suitable for systemic administration, represent another aspect of the invention. Oral pharmaceutical compositions may be preferred. Examples of various types of preparation for oral administration include capsules, tablets, pellets and liquid compositions. Intravenous compositions, such injectable solutions may also be preferred.

The dose of the active agent will depend on the nature and degree of the condition, the age, body weight, general health, sex, diet, time of administration, any other drugs being administered to the patient and other factors known to those skilled in the art. A typical dose is from 0.1 to lg, for example, 100 to 500 mg of the active ingredient dependent upon the type of preparation involved. Preferably the dose is given one to three times per day.

A typical dosage of acetazolamide, e.g. for intravenous administration, is from 100 to 1000 mg, e.g. up to 1000 mg, preferably 250 to 500 mg. Human doses of 100 to 1000 mg may be effective. The drug may be given once, twice or more often each day.

For intravenous injection, the agent of the invention may be in the form of a salt, hydrate or solvate. Salts include pharmaceutically acceptable salts, for example salts derived from inorganic or organic bases, for example alkali metal salts such as sodium, magnesium or calcium salts, and organic amine salts, such as ammonium, morpholine, arginine, piperidine, piperazine, dimethyleamine, diethylamine or N'methylglucamide salts. A pharmaceutical composition containing the active ingredient may be in any suitable form, for example aqueous or non-aqueous solutions or suspensions, dispersable powders or granules, transdermal or transmucosal patches, creams, ointments or emulsions.

The pharmaceutical compositions may be in the form of a sterile injectable aqueous or non-aqueous solution or suspension. The sterile injectable preparation may also be in a sterile injectable solution or suspension in a non-toxic parenterally- acceptable diluent or solvent.

It may be advantageous to administer the agents of the invention or a pharmaceutically acceptable salt with other classes of drug which can add additional benefits of efficacy and/or result in fewer side effects. Acetazolamide and methazolamide may be used according to the invention when the patient is also administered another therapeutic agent or in combination with another therapeutic agent. The therapeutic agent may be selected from drug classes including, but not limited to, antiplatelet agents, such as aspirin, clopidogrel, prasugrel, ticagrelor and dipyridamole; anticoagulants, such as rivaroxaban, hirudin, bivalirudin and dabigatran; lipid/cholesterol modulating drugs, such as statins and antihypertensive drugs.

It is particularly preferred that acetazolamide or methazolamide should be used in combination with another antiplatelet drug. Suitable such agents are aspirin, clopidogrel, prasugrel, ticagrelor.

In a further aspect of the invention, a test kit for testing blood clotting characteristics from an individual is provided. The kit comprises a sample receiver and an agent of the invention to add to a sample of blood contained within the sample receiver.

Preferably the test kit includes a sample receiver having a window to allow for observation of the clotting characteristics of the sample of blood contained in the sample receiver. It is preferred that the window of the sample receiver is arranged so that observation of the sample of blood can be carried out using image microscopy. The kit can include one or more further reagents to add to the sample of blood. The one or more further reagents may be for example an anticoagulant, such as aspirin or clopidogrel. Preferably at least one of the further reagents is an anticoagulant. A preferred anticoagulant is heparin, dabigatran, rivaroxaban, hirudin or bivalirudin.

Another aspect of the invention is a method of monitoring clotting by adding acetazolamide or methazolamide to a blood sample and observing clotting characteristics of said sample over a period of time. A further aspect of the invention provides for the use of acetazolamide or methazolamide to monitor clotting in a blood sample.

The following studies provide evidence on which the invention is based. MATERIALS & METHODS

Platelet-rich plasma (PRP) was prepared from blood drawn from healthy human volunteers. This was anticoagulated with 0.4% trisodium citrate and acidified with 16%) acid citrate dextrose (85 mmol/L trisodium citrate, 71 mmol/L citric acid, 1 1 1 mmol/L glucose). Platelet-rich plasma (PRP) was obtained by centrifugation at 180 g for 17 min. For washed human platelets, PRP was centrifuged at 650 g for 10 min in the presence of 10 μπιοΙ/L indomethacin and 0.02 U/mL apyrase, and resuspended in HEPES-Tyrode' s buffer modified with 0.1%> (w/v) glucose, 10 μιηοΙ/L indomethacin, and 0.02 U/mL apyrase. To measure thrombin generation, PRP was incubated with fluorogenic thrombin substrate, Z-GGR-AMC (450 μιηοΙ/L). PRP was re-calcified and thrombin generation initiated with 5 pmol/L tissue factor. Thrombin substrate was measured on platelet membrane surfaces and traces for single platelets and platelet aggregates were converted into first-derivative curves. Live imaging was by confocal microscopy. Here, washed human platelets were pre- incubated (10 minutes) with calcium dye Fluo-4 AM and Alexa Fluor 568 annexin-V conjugate (1%> ^ν /γ). Hyperosmolar Tyrodes' was prepared by adding 40 mmol/L sucrose to HEPES-Tyrode' s buffer. MatTek dishes were pre-coated with collagen (20 μg/mL) and aliquots of platelet suspensions were added (2xl0 ⁷ cells/mL), supplemented with 1 mmol/L CaCl ₂ . Changes in relative fluorescence intensity (F/Fo) over time were monitored.

In vivo thrombus formation assays were performed as described here. Mice were bred and experimental procedures performed under UK Home Office licence PPL30/2908, held by AWP. Mice were anaesthetised with ketamine 100 mg/kg (Vetalar V, Pfizer) and 10 mg/kg xylazine (Rompun, Bayer). Acetazolamide or control vehicle was administered by intravenous bolus and platelets were labelled by intravenous administration of 100 mg/kg Dylight-488 conjugated anti-GPIbp antibody, 10 min prior to induction of thrombosis. Right carotid arteries were exposed and 2x1 mm 15% ferric chloride-soaked filter paper was placed on the arterial adventitia for 3 min. Time-lapse microscopy of the injury site for 20 min was performed and images processed using ImageJ. Background fluorescence values measured upstream of the injury site were subtracted from thrombus-specific fluorescence and data expressed as integrated densities.

Data analysis was by GraphPad Prism 6 (San Diego, CA) and presented as interleaved box plots with whiskers showing min to max values and interquartile ranges. We determined statistical significance by the Friedman test, followed by Dunn's multiple comparison test or by Wilcoxon Signed Rank Test. p<0.05 (*) or p<0.01 (**) was considered significant.

Assessment of platelet ballooning in vitro. Studies to investigate the effects of acetazolamide, methazolamide and aspirin on the procoagulant response in vitro

Platelets were untreated (control), or preincubated with acetazolamide (30 or 100 μιηοΙ/L), Aspirin (30 μιηοΙ/L) or methazolamide (100 μιηοΙ/L) and allowed 1 hour to settle onto a collagen-coated surface. The percentage of adherent platelets showing different phenotypes (non-ballooned non-spread platelets [ BNS], ballooned non- spread platelet [BNS], conventional spread non-ballooned platelet [CS B], and ballooned and procoagulant-spread platelet [BAPS]) in interleaved box plots with whiskers was observed. Representative images of Alexa568-Annexin-V (AnxV)- stained platelets superimposed on corresponding calcium dye (FLUO-4) or phase- contrast images were produced. Data analysis was by the Friedman test, followed by the Dunn multiple comparison test. P<0.05 (*) or P<0.01 (**) was considered significant.

RESULTS

Platelet ballooning and procoagulant-spreading requires water entry

The requirement of water entry for ballooning was assessed by increasing extracellular osmolality by 40 mmol/L, using sucrose; this significantly attenuated both ballooning (Figure 1A) and procoagulant spreading (BAPS, Figure IB. BAPS formation is the key response that measures ballooning and procoagulant activity of the platelets), but not blebbing (Figure 1 A). Acetazolamide has been shown to block aquaporin water channels (Gao J, Wang X, Chang Y, Zhang J, Song Q, Yu H, Li X. Acetazolamide inhibits osmotic water permeability by interaction with aquaporin- 1. Anal Biochem. 2006; 350: 165-170), and it induced a characteristic retraction of the ballooning membrane (Figure 1A) and attenuated membrane accumulation of annexin-V. Importantly, there was also a marked reduction in formation of ballooned and procoagulant-spread (BAPS) platelets (Figure IB), suggesting a requirement for water entry in procoagulant-spreading. In addition, acetazolamide and hyperosmotic challenge significantly reduced phosphatidylserine (PS) exposure and thrombin generation on the platelet surface (Figures 1C&D). The mean intensity of thrombin substrate per unit membrane area was similar in BAPS and BNS platelets (Figure IE), suggesting that the greater thrombin generation seen in controls was due to increased membrane surface area provided by ballooning and procoagulant- spreading.

Acetazolamide significantly reduces in vivo thrombus formation.

Mice were treated by bolus intravenous administration of acetazolamide (7 mg/kg) and carotid artery damage was induced by application of FeCl ₃ (10% _V ). Accumulation of platelets, labelled with DyLight 488-antiGplbp, was visualised by video epifluorescence microscopy. Whereas control mice showed rapid and sustained accumulation of platelets in a growing and eventually occlusive thrombus, mice treated with acetazolamide were markedly spared from this event (Figure 2). Balloon-enhanced local generation of thrombin will therefore likely form a positive feedback system to further activate platelets and promote coagulation.

Acetazolamide and methazolamide inhibit human platelet procoagulant response to collagen in a manner distinct from aspirin.

The effects of acetazolamide, methazolamide and aspirin on the procoagulant response were investigated in human platelets allowed to adhere to collagen in the presence of physiological levels of calcium. The results shown in Figure 3 revealed acetazolamide and methazolamide inhibited human platelet procoagulant response in a manner that differed from aspirin. While ballooning and procoagulant-spreading (BAPS) were unaffected by the presence of aspirin, the formation of the BAPS platelet phenotype, where platelets balloon and procoagulant spread, was significantly attenuated by acetazolamide and methazolamide. Methazolamide, however, caused a greater loss in PS exposure and greater inhibition of procoagulant spreading, suggesting potentially a greater potency for methazolamide than acetazolamide (Figure 3).