# Patent

## Title
Compounds and their use related to compositions for treating disease

## Abstract

Novel compounds and their uses are disclosed herein.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser. No. 11/551,385, filed Oct. 20, 2006, now U.S. Pat. No. 7,534,795, which claims the benefit of, U.S. Provisional Application No. 60/730,548, filed Oct. 25, 2005, and which is incorporated herein by reference.


DESCRIPTION
Ocular hypotensive agents are useful in the treatment of a number of various ocular hypertensive conditions, such as post-surgical and post-laser trabeculectomy ocular hypertensive episodes, glaucoma, and as presurgical adjuncts.
Glaucoma is a disease of the eye characterized by increased intraocular pressure. On the basis of its etiology, glaucoma has been classified as primary or secondary. For example, primary glaucoma in adults (congenital glaucoma) may be either open-angle or acute or chronic angle-closure. Secondary glaucoma results from pre-existing ocular diseases such as uveitis, intraocular tumor or an enlarged cataract.
The underlying causes of primary glaucoma are not yet known. The increased intraocular tension is due to the obstruction of aqueous humor outflow. In chronic open-angle glaucoma, the anterior chamber and its anatomic structures appear normal, but drainage of the aqueous humor is impeded. In acute or chronic angle-closure glaucoma, the anterior chamber is shallow, the filtration angle is narrowed, and the iris may obstruct the trabecular meshwork at the entrance of the canal of Schlemm. Dilation of the pupil may push the root of the iris forward against the angle, and may produce pupilary block and thus precipitate an acute attack. Eyes with narrow anterior chamber angles are predisposed to acute angle-closure glaucoma attacks of various degrees of severity.
Secondary glaucoma is caused by any interference with the flow of aqueous humor from the posterior chamber into the anterior chamber and subsequently, into the canal of Schlemm. Inflammatory disease of the anterior segment may prevent aqueous escape by causing complete posterior synechia in iris bombe, and may plug the drainage channel with exudates. Other common causes are intraocular tumors, enlarged cataracts, central retinal vein occlusion, trauma to the eye, operative procedures and intraocular hemorrhage.
Considering all types together, glaucoma occurs in about 2% of all persons over the age of 40 and may be asymptotic for years before progressing to rapid loss of vision. In cases where surgery is not indicated, topical β-adrenoreceptor antagonists have traditionally been the drugs of choice for treating glaucoma.
Disclosed herein is a compound having the structural formula




One compound has the structural formula





This compound is 8-(5-bromoquinoxalin-6-yl)-5-oxo-2,3,5,6,7,8-hexahydroimidazo[1,2-a]pyrimidine-7-carboxylic acid.

Another compound has the structural formula




For the purposes of this disclosure, a “compound” includes the compound, pharmaceutically acceptable salts of these compound, tautomers of the compound, or combinations thereof.
Thus, a compound having the structural formula




is intended to mean the species depicted by the structural formula, a salt of the species depicted by the structural formula, or a tautomer of the species depicted by the structural formula.

Similarly, if a composition comprises from about 0.0005% to about 0.2% of a compound having the structural formula




it means that the sum of:

    
    
        1. the concentration of the species depicted by the structural formula,
        2. the total concentration of all pharmaceutically acceptable salts of the species depicted by the structural formula that are present in the composition, and
        3. the concentrations of all the tautomers of the species depicted by the structural formula that are present in the composition, is from about 0.0005% to about 0.2%.
    
    


Unless otherwise indicated, all concentrations in the claims and description herein given as % are meant to indicate concentration by weight/volume %.
The compound disclosed herein may be prepared by dissolving brimonidine free base in chloroform and adding maleic anhydride. This solution is stirred for about 2 hours. Evaporation of the solvent will yield about 80% pure product, which may be further purified by methods known in the art, such as recrystallization, chromatography, etc.
One embodiment is a composition comprising about 0.5% timolol, from about 0.15% to about 0.2% brimonidine tartrate, and from about 0.0005% to about 0.2% of a compound having the structural formula




In certain compositions said compound has the structural formula




In other compositions said compound has the structural formula




Another composition comprises about 0.5% timolol, from about 0.15% to about 0.2% brimonidine tartrate, and from about 0.0005% to about 0.003% of a compound having the structural formula




In one composition said compound has the structural formula




In another composition said compound has the structural formula




The compositions may be prepared by combining the compound prepared as described above with brimonidine tartrate and timolol in a single composition.
Alternatively, compositions disclosed herein may be prepared by combining the ingredients shown in Table 1 below into a single formulation.









TABLE 1





Ingredient
Function
Concentration, % (w/v)







Brimonidine Tartrate
Active
0.2 


Timolol Maleate, EP
Active
 0.681


Benzalkonium Chloride, NF, EP
Preservative
 0.005


Sodium Phosphate, monobasic
Buffer
0.43


monohydrate, USP




Sodium Phosphate, dibasic
Buffer
2.15


heptahydrate, USP




Sodium Hydroxide, NF
pH adjust
Adjust pH to 6.9


Hydrochloric Acid, NF
pH adjust
Adjust pH to 6.9


Purified Water, USP, EP
Solvent
q.s. ad





1Equivalent to 0.5% (w/v) Timolol, free base






This composition is then allowed to stand at 25-40° C. for 3-6 months to yield the desired composition. While not wishing to be bound by theory, it is believed that above compound is formed by reaction of brimonidine and maleic acid or maleate ion over time to yield the compound. These compositions are useful for one or more of treating and/or preventing ocular hypertension and/or glaucoma.


While not intending to limit the scope of the invention in any way, the compounds disclosed herein are useful as standards for determining the purity of a composition prepared having brimonidine and maleic acid and/or maleate salts. Purity may be determined by combining a measured amount of brimonidine with a measured amount of the compound and subjecting the mixture to liquid chromatography, and comparing the peaks to those of brimonidine and the compound analyzed alone. The relative responses of the two compounds to the detection system of the liquid chromatography system is determined by comparing the peak area of brimonidine and the compound to the known amount of each compound added. A response factor K, is obtained by equation 1

BAC/CAB=K  [eq. 1]

where B is the concentration of brimonidine, C is the concentration of the compound, AC is the area of the compound peak, and AB is the area of the brimonidine peak.

The sample is then injected into the liquid chromatography system and the ratio of the area of the brimonidine in the sample (ABo) and the compound in the sample (ACo) is used to determine the ratio of the concentration of brimonine (Bo) and the concentration of the compound C (Co) in the sample according to equation 2, which uses K from equation 1.

Bo/Co=KABo/ACo  [eq. 2]

The compound disclosed herein can also be used to estimate the age of a composition, stored at ambient temperature, initially comprising brimonidine tartrate and timolol maleate of known amounts and having a pH of 6.9. The age of the compound (λ) in months is determined by equation 3, where Bo, To, and Co are the initial concentrations of brimonidine, timolol maleate, and the compound respectively, in % (w/v).

λ=Co/(1.1×10−3(BoTo))  [eq. 3]

Equation 3 is an approximation which assumes that Bo and To>>Co. If that is not the case, the age is determined using the rate constant k=1.1×10−3 month−1%−1 and the appropriate rate expression.

If the composition initially comprises 0.2% brimonidine tartrate and 0.68% timolol maleate. The age of the composition may be determined according to Table 2 below. Alternatively, up to about 36 months, the age is determined by multiplying the concentration of the compound in % (w/v) by 9100.









TABLE 2






Compound




Concentration (% weight/vol)
Age (months)


















0.0001
1



0.0002
2



0.0003
3



0.0004
4



0.0006
5



0.0007
6



0.0008
7



0.0009
8



0.001
9



0.0011
10



0.0012
11



0.0013
12



0.0014
13



0.0016
14



0.0017
15



0.0018
16



0.0019
17



0.0020
18



0.0021
19



0.0022
20



0.0023
21



0.0024
22



0.0026
23



0.0027
24









Other uses of the compound may include, but are not limited to, chelating agent, buffering agent, pH indicator, cation selection, solubilizing agent, emulsifier, and surfactant. In particular, the compound may be useful as a pH sensitive agent, in for example, making the emulsification and demulsification of a composition pH sensitive, thus giving greater control in the making and breaking of the emulsion. It may also be useful in controlling chelation, such that chelation occurs at a certain pH but the chelated cation is released at another pH, thus providing use in separation.
Brimonidine tartrate is an alpha adrenergic agonist represented by the following formula:




The chemical name for brimonidine tartrate is 5-Bromo-6-(2-imidazolidinylideneamino)quinoxaline L-tartrate.
Timolol maleate is a beta adrenergic agent represented by the following formula:




As used herein concentrations of timolol refer to equivalent the concentration of the free base, regardless of any salt that may be used. Timolol maleate is often the salt of choice herein for providing timolol to a composition.

Brimonidine tartrate is available from Allergan, Inc., Irvine, Calif. as an ophthalmic pharmaceutical product having the name Alphagan®.
Timolol is available from various sources, including Merck Co., Rahway, N.J.
The compositions of the present invention are administered topically. The dosage is 0.001 to 1.0, e.g. mg/per eye BID; wherein the cited mass figures represent the sum of the two components, brimonidine and timolol. The compositions of the present invention can be administered as solutions in a suitable ophthalmic vehicle.
In forming compositions for topical administration, mixtures may also be formulated as 0.01 to 0.5 percent by weight brimonidine and 0.1 to 1.0 percent by weight timolol solution in water at a pH of 4.5 to 8.0, e.g. about 6.9, and with about 0.0005% to about 0.2% of a compound having the structural formula:




While the precise regimen is left to the discretion of the clinician, it is recommended that the solution be topically applied by placing one drop in each eye two times a day.

Other ingredients in addition to those already mentioned which may be desirable to use in the ophthalmic preparations of the present invention include preservatives, co-solvents and viscosity building agents.
Antimicrobial Preservative:
Ophthalmic products are typically packaged in multidose form. Preservatives are thus required to prevent microbial contamination during use. Suitable preservatives include: benzalkonium chloride, thimerosal, chlorobutanol, methyl paraben, propyl paraben, phenylethyl alcohol, edetate disodium, sorbic acid, Onamer M, or other agents known to those skilled in the art. In the prior art ophthalmic products, typically such preservatives are employed at a level of from 0.004% to 0.02%. In the compositions of the present application the preservative, preferably benzalkonium chloride, may be employed at a level of from 0.001% to less than 0.01%, e.g. from 0.001% to 0.008%, preferably about 0.005% by weight. It has been found that a concentration of benzalkonium chloride of 0.005% is sufficient to preserve the compositions of the present invention from microbial attack. This concentration may be advantageously compared to the requirement of 0.01% benzalkonium chloride to preserve timolol in the individual, commercially-available ophthalmic products.
Co-Solvents:
The solubility of the components of the present compositions may be enhanced by a surfactant or other appropriate co-solvent in the composition. Such cosolvents include polysorbate 20, 60, and 80, Pluronic F68, F-84 and P-103, cyclodextrin, or other agents known to those skilled in the art. Typically such co-solvents are employed at a level of from 0.01% to 2% by weight.
Viscosity Agents:
Viscosity increased above that of simple aqueous solutions may be desirable to increase ocular absorption of the active compound, to decrease variability in dispensing the formulation, to decrease physical separation of components of a suspension or emulsion of the formulation and/or to otherwise improve the ophthalmic formulation. Such viscosity building agents include as examples polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, hydroxy propyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxy propyl cellulose or other agents known to those skilled in the art. Such agents are typically employed at a level of from 0.01% to 2% by weight.
The present invention further comprises an article of manufacture comprising packaging material and a pharmaceutical agent contained within said packaging material, wherein the pharmaceutical agent is therapeutically effective for lowering intraocular pressure and wherein the packaging material comprises a label which indicates the pharmaceutical agent can be used for lowering intraocular pressure and wherein said pharmaceutical agent comprises an effective amount of brimonidine and an effective amount of timolol and from about 0.0005% to about 0.2% of a compound having the structural formula:




EXAMPLE 1
The composition of Table 2 is prepared and stored in containers at ambient temperatures for later dispensing. Nine months later, the composition is administered topically to the eyes of patient for the treatment of glaucoma. Administration is carried out twice a day. A significant reduction in intraocular pressure is observed, and continues while the patient continues to receive the treatment.
EXAMPLE 2
Brimonidine (7.0 g) and maleic anhydride (3.53 g) were added to ethanol free chloroform (200 ml) and heated to 50° C. overnight. The solvent was evaporated and the residue slurried in MeCN (50 ml) at 30° C. for 2 h. The resultant solid was filtered washed with MeCN (25 ml) and dried in an oven at 40° C. to yield 10.5 g of 8-(5-bromoquinoxalin-6-yl)-5-oxo-2,3,5,6,7,8-hexahydroimidazo[1,2-a]pyrimidine-7-carboxylic acid.

## Claims

1. A method comprising administering a composition topically to an eye of a mammal, wherein said method is effective for treatment of glaucoma and/or ocular hypertension, said composition comprising about 0.5% timolol, from about 0.15% to about 0.2% brimonidine tartrate, and from about 0.0005% to about 0.2% of a compound having the structural formula

2. The method of claim 1 wherein the concentration of said compound in said composition is from about 0.0005% to about 0.003%.

3. A method of determining the age of a composition initially consisting of 0.2% Brimonidine Tartrate, 0.68% Timolol Maleate, 0.005% Benzalkonium Chloride, 0.43% Sodium Phosphate monobasic monohydrate, 2.15% Sodium Phosphate dibasic heptahydrate, a sufficient quantity of NaOH or HCl to adjust the pH to 6.9, and the remainder water,
wherein said method comprises:
providing a solution with a known concentration of a compound having a formula




and a known concentration of brimonidine tartrate,
analyzing said solution by a chromatographic method,
determining the detector response for brimonidine and the compound based upon the known concentrations,
analyzing said composition by said chromatographic method,
obtaining the concentration of the compound in said composition using the detector response,
obtaining the age of the composition in months by multiplying the concentration of the compound by 9100,
with the proviso that the concentration of the compound is greater than 0.0001% and less than about 0.004%.