HK1011685B - Compounds having both potent calcium antagonist and antioxidant activity and use thereof as cytoprotective agents - Google Patents

Description

Background of Invention: 1. Field of the Invention

The present invention is directed to the provision of compounds having potent calcium antagonist and antioxidant activity, and to the use of those compounds as cellular protective agents. The invention is further directed to the provision of methods for synthesizing the compounds of the invention and to compounds formed as intermediates during the synthesis. The invention is particularly directed to the use of the compounds of the present invention to prevent or reduce cellular damage associated with ophthalmic diseases or injuries.

2. Discussion of Related Art

In a biological system under stress induced by trauma, ischemia-reperfusion, depletion of natural defenses, inflammation, light damage (especially laser or intense operating room light), or degenerative conditions, damage occurs which can result in an increase in cellular free calcium and/or an increase in oxidative damage. Both these changes are components of the common pathway of cell death. The result of these changes is the initiation of a cascade of cellular destruction, loss of cellular function and ultimately cell loss. The loss of critical cellular components can result in organ damage and loss of organ function. Loss of function can be caused by an acute insult or may be the result of the cumulative effects of chronic insult. The following texts may be referred to for further details concerning these phenomena:

• Prog. Neuro-Psychopharmacol. and Biol. Pysch., volume 17, pages 21-70 (1993);
• Age, volume 16, pages 23-30 (1993);
• Chem. Res. Tox., volume 32, pages 2-18 (1993); and
• Ann. Neurol., volume 32, pages S33-42 (1992).

Calcium flux is a necessary part of normal cell function. The level of intracellular free calcium is highly regulated. Both receptor-operated and voltage-sensitive channels control cell signaling and stimulus response. Multiple voltage-sensitive calcium channels have been identified. These include the N, T, P, and L channels. The following publications may be referred to for further background concerning the regulation of intracellular free calcium levels:

• Med. Res. Review, volume 9, pages 123-80 (1989);
• Pharmacol. Review, volume 38(4), pages 321-416 (1986);
• Cardiovasc. Drugs and Therapy, volume 6, pages 35-39 (1992);
• Science, volume 235, pages 46-52 (1987);
• Chem.-Biol. Interactions, pages 1-23 (1991); and
• Biochemical Pharmacol., volume 43(1), pages 39-46 (1992).

Over-stimulation of the cell or cellular system or the defective regulation of intracellular free calcium can result in increased intracellular free calcium levels. This can lead to the initiation of a chain of biochemical processes which can lead to cell death. Agents that modulate increases in intracellular free calcium concentration can moderate the deleterious effects of over-stimulation or defective regulation. See PNAS, volume 89, pages 435-39 (1992), and references cited above. In addition, a compound that acts as a calcium antagonist can provide an additional beneficial effect by improving blood flow, reducing ischemic insult and facilitating repair. See Naunyn-Schmiedeberg's Acta Pharmacol., volume 335, pages 680-685 (1987). As utilized herein, the term "calcium antagonists" refers to organic molecules which inhibit increases in intracellular free calcium concentrations.

Agents that act as antioxidants can protect against oxidative damage associated with cellular stress. Such protection has been the subject of numerous scientific publications, including the following:

• Arch. Pharmacol., volume 325, pages 129-146 (1992);
• Free Rad. Biol. Med., volume 6, pages 209-224;
• Free Rad. Biol. Med., volume 11, pages 215-232 (1991);
• Eur. J. Pharmacol., volume 210, pages 85-90 (1992);
• J. Photochem., Photobiol. Biol., volume 8, pages 211-224 (1991);
• Pharmacol. and Tox., volume 70, pages 271-277 (1992); and
• Medicinal Res. Rev., volume 13(2), pages 161-182 (1993).

The combined use of two or more compounds having calcium antagonist and antioxidant activity, respectively, is discussed in Experimental Eye Research, volume 5, pages 71-78 (1993). The provision of compounds having both calcium antagonist and antioxidant activity is discussed in the following patent publications: EP 267 155A and WO 89/05803 Al.

WO87/05020 discloses 3,4-dihydro-2H-benzopyran derivatives which inhibit 5-lipoxygenase and inhibit platelet agglutination and which have an antiallergenic effect, antihistaminic effect, and the effect of preventing peroxidation of lipids. They are useful as drugs for treating bronchial asthma, allergic disease, immune disease, inflammatory disease, Psoriasis vulgaris, brain blood trouble, ischemic disease, thrombosis, etc. From these uses it can be seen that these compounds act as calcium antagonists and have antioxidant activity.

EP-A-0487510 discloses bicyclic amines which are capable of acting as calcium antagonists and antioxidants and which are useful as pharmaceutical agents for treating a number of conditions including spinal trauma and head injury.

GB-A-705979 discloses a number of 1,4-aralkyl piperazines and a process for their preparation. Such derivatives are known to have remarkable therapeutic properties.

DE-A-2900810 and US-A-3868377 disclose substituted N-benzhydryl-N'-p-hydroxybenzyl-piperazines and methods for their preparation. The compounds disclosed and pharmacologically acceptable salts thereof have valuable pharmacological properties.

EP-A-0159566 discloses 1-benzyl-4-benzhydrylpiperazine derivatives, and processes for the production thereof, which are useful for improving cerebrovascular diseases.

FR-A-2159369 discloses substituted N-styryl-N-benzhydrylpiperazines and pharmacologically active salts thereof which are useful for inhibiting the activity of a complex array of proteins found in bodily fluids, particularly blood serum, which participate in immunochemical and immunopathological reactions.

EP-A-0152799 discloses the compound 1-(4,4'-difluoro-benzhydryl) -4-(3,4-dimethoxycinnamyl)piperazine, processes for the preparation thereof and pharmaceutical compositions thereof. This compound exhibits potent peripheral calcium antagonist, anticonvulsive and eumetabolic activities.

One compound known to have calcium antagonist activity, flunarizine, has also been reported to have free radical scavenging activity. See:

• Arch. int. Pharmacodyn., volume 272, pages 283-295 (1984);
• Eur. J. Pharmacol., volume 204, pages 315-322 (1991); and
• Meth. and Find Exp. Clin. Pharmacol., volume 11(10), pages 607-612 (1989).

In addition, other classes of calcium antagonists have been reported to have antioxidant activity. See:

• Free Rad. Biol. and Med., volume 12, pages 183-187 (1992);
• Res. Commun. in Chem. Path. and Pharmacol., volume 76(3), pages 367-370 (1992);
• J. Mol. Cell Cardiol., volume 22, pages 1199-1208 (1990);
• Circulation Res., volume 66(5), pages 1449-1452 (1990);
• J. Cardiovas. Pharmacol., volume 18(Suppl. 1) pages S6-S10 (1991);
• Basic Res. in Cardiology, volume 87, pages 148-160 (1992);
• Free Rad. Res. Comms., volume 15(2), pages 91-100 (1991); and
• Biochem. Pharmacol., volume 37(21), page 4197 (1988).

However, in most cases the antioxidant effect reported is weak and not clinically relevant. This is pointed out in Biochem. Pharmacol., volume 42(4), pages 735-743 (1991), and Biochem. Pharmacol., 38(20), pages 3601-3610 (1989). In addition, it is believed that a number of the effects attributed to the free radical scavenging effect of flunarizine might actually be an effect of its calcium antagonist activity since this activity was poorly understood in the early 1980's.

The present invention is directed to the provision of new compounds that have both potent calcium antagonist and potent antioxidant activity in a single molecule. The use of a single chemical entity with potent antioxidant and potent calcium antagonist activity provides increased protection relative to the use of a compound with singular activity. The advantage of a single agent with both activities over a combination of two components would be realized by the uniform delivery of an active molecule simplifying issues of drug metabolism and delivery.

Summary of the Invention:

The present invention provides new compounds having potent calcium antagonist and antioxidant activity. The dual therapeutic action of the compounds provides a distinct advantage over prior therapies. The dual therapeutic actions act in a complementary manner to prevent or reduce cellular damage.

The compounds of the present invention are effective cytoprotective agents. These compounds were conceived by making modifications in known calcium antagonists which confer antioxidant activity while maintaining calcium antagonist activity. More specifically, the invention is based in part on the discovery of appropriate structural modifications of compounds having calcium antagonist activity which maintain the calcium antagonist activity of the compounds while adding potent antioxidant activity. By taking advantage of the limited allowed substitution in the piperidine or piperazine rings of known calcium antagonists, modifications have been made to instill potent antioxidant activity while retaining the calcium antagonist activity.

The compounds and associated pharmaceutical compositions of the present invention may be used to prevent or alleviate damage to various types of tissues. However, the use of the compounds to prevent or reduce damage to ophthalmic tissues at the cellular level is a particularly significant aspect of the present invention. Conditions which may be treated include cataracts, retinopathies, heredodegenerative diseases, macular degeneration, ocular ischemia, neovascular diseases, glaucoma, and damage associated with injuries to ophthalmic tissues, such as ischemia reperfusion injuries, photochemical injuries, and injuries associated with ocular surgery, particularly injuries to the retina, cornea or other tissues caused by exposure to light or surgical instruments.

The compounds of the present invention are capable of protecting against cellular damage caused by a wide range of insults. Since the compounds provide this protection by decreasing free radical or oxidative damage and by reducing the increase in intracellular free calcium, it represents a two-prong approach to cytoprotection. Both of these mechanisms are responsible for the loss of cellular viability associated with stress regardless of the source. In addition, the expected increase in blood flow due to the calcium antagonist activity contributes to the therapeutic effect. Among other things, the advantage of a single compound over a combination of two or more compounds is that the single entity offers uniform delivery of an active molecule having both antioxidant and calcium antagonist properties. The use of a single compound rather than a combination of compounds greatly simplifies issues of pharmacokinetics, drug metabolism, and delivery.

Detailed Description of the Invention

According to a first embodiment of this invention there is provided a compound of the formula:         A - Y- B     (I) wherein:

• A is an antioxidant selected from the group consisting of: wherein R is C1 to C6 alkyl;
• Y is (CH2)n or CH=CH(CH2)n, wherein n is a whole number of from 1 to 6; and
• B is selected from the group consisting of:

wherein:

• n' is a whole number of from 1 to 6;
• Z is H, CN or OH;
• X is F, Cl, I, Br, OH, OR', SH, S(O)mR', CN or NO2, wherein R' is C1 to C6 alkyl and m is 0, 1 or 2; and
• o is 0, 1, 2 or 3, or a pharmaceutically acceptable salt thereof.

According to a second embodiment of this invention there is provided a pharmaceutical composition for preventing or alleviating damage to mammalian tissues, comprising an amount of a compound of the following formula effective to decrease free radical or oxidative damage and control intracellular free calcium levels in said tissues:         A-Y-B wherein:

• A is an antioxidant selected from the group consisting of: wherein
• R is C1 to C6 alkyl;
• Y is (CH2)n or CH=CH(CH2)n, wherein n is a whole number of from 1 to 6; and
• B is selected from the group consisting of: wherein:

• n' is a whole number of from 1 to 6;
• Z is H, CN or OH;
• X is F, Cl, I, Br, OH, OR', SH, S(O)mR', CN or NO2, wherein R' is C1 to C6 alkyl and m is 0, 1 or 2; and
• o is 0, 1, 2 or 3, or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable vehicle therefor.

The compounds of Formula (I) are further illustrated by the representative species identified in the following tables, wherein R is C₁ to C₆ branched or unbranched alkyl, but is preferably methyl.

Criteria for selecting specific antioxidant moieties and for evaluating antioxidant and calcium antagonist activity in relation to compounds of Formula (I) are described below.

The antioxidant moieties of the above-described compounds are substances such as an organic molecule, which are known to be capable of reacting with the free radicals encountered in physiological systems. For a substance to have a protective effect as an antioxidant in a physiological system, it must act to prevent the damaging activity of free radicals by: (i) inhibiting the process leading to their generation, (ii) suppressing the amplification of the process by scavenging primary free radicals, or (iii) inhibiting theamplification of free radical-initiated damage by intercepting secondary free radicals. The therapeutic activity of an antioxidant in a biological system depends on the source and nature of the damaging free radical, the site of damage, and the delivery of a therapeutically effective concentration of the antioxidant to the appropriate site. This invention is concerned with substances that demonstrate antioxidant activity by reacting with free radicals to reduce the damage caused by these species. The antioxidant component contributes to the cytoprotective activity of these compounds by quenching the primary free radicals or the free radicals generated as the primary damage process is amplified.

The preferred antioxidant moieties in the compounds of Formula (I) are phenolic compounds. The antioxidant activity of these compounds is thought to reside in their ability to react with free radicals and therefore terminate radical chain reactions. The reaction of these phenolic compounds with peroxyl free radicals in biological systems is particularly important. The phenoxyl radicals formed by the reaction of a free radical with a phenol are resonance stabilized and typically do not continue the chain reaction. In biological systems, the parent phenol from phenolic antioxidants such as α-tocopherol (vitamin E) can be regenerated from the phenoxyl free radical by vitamin C and/or glutathione (GSH), thereby providing a way to complete the detoxification process. See Free Radical Biology & Medicine, volume 15, pages 311-328 (1993).

The antioxidant activity of the phenolic compounds is enhanced by stabilizing the phenoxyl free radical or by facilitating the transfer of the free radical to other components of the detoxification mechanism, such as GSH or vitamin C. Alkyl substituents stabilize the phenoxyl free radical by electron donation and the stearic bulk of ortho substituents reduces the propensity of the phenoxyl radical to participate in free radical chain reactions. An increase in stearic bulk ortho dimethyl to ortho di-tert-butyl groups decreases the reactivity due to the excessive crowding of the reactive phenolic hydroxy groups. In addition, overcrowding reduces the rate of exchange with the biological detoxification mechanisms, thereby reducing the efficiency of the antioxidant. The introduction of a parasubstituent such as an OH or O-alkyl group increases the stability of the phenoxyl free radical by delocalizing the electron density through p orbital overlap. By including the para oxygen in a five or six membered ring, the p orbital of the oxygen is constrained in a position that approaches being perpendicular to the aromatic ring, providing near optimum overlap and allowing efficient delocalization of the electron density. Combining ortho methyl substituents with a para alkoxy group constrained in a five or six membered ring provides a phenolic compound with potent antioxidant activity. Antioxidant activity can be enhanced by selectively incorporating modifications such as those discussed above.

Based on the foregoing considerations and the known structure-activity relationships of the calcium antagonists, the above described phenolic groups are preferred as the antioxidant moiety of the present compounds. The most preferred antioxidant moieties are benzofuran derivatives, which provide potent antioxidant activity but do not interfere with calcium antagonist activity.

The compounds of the present invention have free radical scavenging activity that can be measured by the ability of the above-described antioxidant moieties of the compounds to quench a stable free radical dye, such as 1,1'-diphenyl-2-picrylhydrazie (DPPH), as described in Free Radical Research Communications, volume 15, pages 91-100 (1991), or by the ability of the compound to protect against oxidative insult in liposomes or microsomes, as described in Biochimica, Biophysica Acta, volume 1081, pages 181-187 (1991) and Chemical andBiological Interactions, volume 74, pages 233-252 (1990), respectively. Thus, the antioxidant moieties in the compounds of the present invention will:

• 1) provide greater than 20% quench of the free radical at concentrations of DPPH and the test agent equal to 10-4M, in accordance with the above-cited DPPH assay;
• 2) demonstrate an IC50 of less than 20 µM, in accordance with the above cited liposome assay; or
• 3) demonstrate an IC50 of less than 20 µM, in accordance with the above-cited liver microsome assay.

Antioxidant moieties which satisfy the foregoing criteria are referred to herein as having "therapeutically significant free radical scavenging activity".

The calcium antagonist moieties of the compounds of the present invention are organic compounds which inhibit increases in intracellular-free calcium. Increased intracellular-free calcium may arise from the influx of calcium from extracellular sources or the release of sequestered calcium from intracellular stores. Intracellular-free calcium concentration is regulated by many mechanisms, including, for example, receptor-operated calcium channels, voltage-sensitive calcium channels, sodium-calcium exchangers, and calcium flux through sodium channels. A sustained increase in intracellular-free calcium results in events such as the deregulation of cellular metabolism and the activation of catabolic enzymes, such as calcium-activated proteases and phospholipases. This process can ultimately lead to cell loss. Calcium antagonists can inhibit the increase in intracellular calcium by various mechanisms including but not limited to:

• a) preventing the flux through voltage-sensitive calcium channels (N,L,T,P);
• b) blocking flux through receptor operated calcium channels;
• c) preventing the release of calcium sequestered in sarcoplasmic reticulum; or
• d) blocking nonspecific channels (i.e., reversing sodium/calcium exchangers or blocking calcium flux through a sodium channel).

The compounds of the present invention act as calcium antagonists by inhibiting increases in intracellular calcium. The calcium antagonist activity of the compounds may be determined in accordance with one or more of the assays listed below:

• 1) radioligand binding assays, wherein radiolabeled nitrendipine is displaced from rat brain cortices (minimum activity: IC50 of less than 20 µM), as described in Life Science, volume 30, pages 2191-2202 (1979) and Procedures of the National Academy of Science, USA, volume 79, pages 3656-3650 (1982);
• 2) calcium antagonist binding assays, such as the relaxation of pre-contracted rabbit aortic strips of greater than 7.0, as described in Journal of Medicinal Chemistry, volume 34, pages 3011-3022 (1991) and references cited therein (minimum activity: IC50 value less than 20 µM);
• 3) inhibition of calcium flux in a cellular system, as measured by a fluorescent dye, in accordance with the procedures described in Journal of Cardiovascular Pharmacology, volume 17, pages 41-53 (1991), and references cited therein, (minimum activity: IC50 of less than 100 nm); or
• 4) inhibition of calcium induced contractions of rabbit thoracic aortic strips, in accordance with the procedures described in Journal Cardiovascular Pharmacology, volume 17, pages 41-53 (1991), and references cited therein (minimum activity: pA2 greater than 7).

Although the above-described activities define the upper limits for compounds expected to have cytoprotective activity afforded by the combined antioxidant/calcium antagonist mechanisms described herein, it is also necessary for the compounds to be delivered to the target tissue and for tissue levels to reach therapeutically effective levels, in order for the compounds to demonstrate cytoprotective activity. It is also to be understood that each of the compounds of Formula (I) is useful to different degrees for treating patients afflicted with or prone to various types of cellular damage. The success of treatment will depend on the type of cellular insult and the route of administration used to treat those conditions.

The preferred compounds are those wherein: the antioxidant moiety A is a, b or c and R, if present, is methyl; n is 1 to 4; and the calcium antagonist moiety is a' or d', Z is H or OH, and X is F, Cl, CN, S(O)_mR' or OR', wherein m is 1 or 2 and R' is branched or unbranched C₁ to C₄ alkyl

Compounds of the formula A-Y-B, as defined above, may be prepared in accordance with the following general schemes as well as modifications thereof which will be apparent to those skilled in the art: $\text{Method 1}\text{\hspace{1em}\hspace{1em}\hspace{1em}A-Y-L + B → A-Y-B}$ Amines of the general form B, as defined above, can be reacted with the activated alcohol derivative A-Y-L, where L is a leaving group such as a Cl, Br, I or organic sulfonate (such as mesylate or tosylate) and A-Y are as described above, under standard conditions using solvents such as acetonitrile, dimethylformamide, 1-butanol or tetrahydrofuran in the presence of a base such as potassium carbonate, potassium bicarbonate, sodium carbonate or sodium bicarbonate. The use of certain protecting groups and deprotection steps may be necessary, as will be appreciated by those skilled in the art. Compounds A-Y-L and B are commercially available or can be prepared using known reactants and procedures. $\underline{\text{Method 2}}{\text{\hspace{1em}\hspace{1em}\hspace{1em}A-W-CHO + B → A-W-CH}}_{\text{2}}\text{-B = A-Y-B}$

Amines of the general formula B, as defined above, can be condensed with the aldehyde A-W-CHO, wherein W is (CH₂)_n-1, or CH=CH(CH₂)_n-1, n is 1 to 6, and A is as described above, and then the resulting species can be reduced using a reducing agent such as sodium borohydride, sodium cyanoborohydride, lithium aluminum hydride or Red-Al to give the product, A-Y-B. The use of certain protecting groups and deprotection steps may be necessary, as will be appreciated by those skilled in the art. $\underline{\text{Method 3}}{\text{\hspace{1em}\hspace{1em}\hspace{1em}A-W-CO}}_{\text{2}}{\text{H + B → A-W-CH}}_{\text{2}}\text{-B = A-Y-B}$

Amines of the general formula B, as defined above, can be coupled with the acid, A-W-CO₂H, wherein A and W are as defined above, using standard conditions such as 1-3-dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1-hydroxybenzotriazole or 4-dimethylaminopyridine in a solvent such as dimethylformamide, acetonitrile, methylene chloride or a mixture thereof. The resulting amide can be reduced using a reducing agent such as lithium aluminum hydride borane-dimethyl sulfide of Red-Al. The use of certain protecting groups and deprotection steps may be necessary, as will be appreciated by those skilled in the art.

The compounds of Formula (I) are typically converted to amine salts by reacting the amine with acids of sufficient strength to produce an organic or inorganic salt. The anions of the preferred pharmaceutically acceptable salts include acetate, bromide, chloride, citrate, maleate, fumurate, mesylate, phosphate, sulfate and tartarate.

Since there is an asymmetric carbon atom on the benzofuran or benzothiophene ring, the compounds may occur as either the R or S enantiomers, or mixtures thereof. The preparation of the individual enantiomeric form may be effected by resolving the acids by conventional means such as the use of diastereomeric salt with optically active amines. The alcohols could be resolved by forming the esters with optically active carboxylic acids, carrying out the resolution and then hydrolyzing the resolved diastereomers.

The compounds of Formula (I) may be contained in various types of pharmaceutical compositions, in accordance with formulation techniques known to those skilled in the art. For example, the compounds may be included in tablets, capsules, solutions, suspensions and other dosage forms adapted for oral administration; solutions and suspensions adapted for parenteral use; and suppositories for rectal use. Solutions, suspensions and other dosage forms adapted for topical application to the involved tissues, such as tissue irrigating solutions, are particularly preferred for treatment of acute conditions associated with surgery or other forms of trauma.

The present invention is particularly directed to the provision of compositions adapted for treatment of ophthalmic tissues. The ophthalmic compositions of the present invention will include one or more compounds of Formula (I) and a pharmaceutically acceptable vehicle for said compound(s). Various types of vehicles may be utilized. The vehicles will generally be aqueous in nature. Aqueous solutions are generally preferred, based on ease of formulation, as well as patients' ability to easily administer such compositions by means of instilling one to two drops of the solutions in the affected eyes. However, the compounds of Formula (I) may also be readily incorporated into other types of compositions, such as suspensions, viscous or semi-viscous gels or other types of solid or semi-solid compositions. Suspensions may be preferred for compounds of Formula (I) which are relatively insoluble in water. The ophthalmic compositions of the present invention may also include various other ingredients, such as buffers, preservatives, co-solvents and viscosity building agents.

An appropriate buffer system (e.g., sodium phosphate, sodium acetate or sodium borate) may be added to prevent pH drift under storage conditions.

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. Such preservatives are typically employed at a level of from 0.001% to 1.0% by weight.

Some of the compounds of Formula (I) may have limited solubility in water and therefore may require a surfactant or other appropriate co-solvent in the composition. Such co-solvents include: Polysorbate 20, 60 and 80; Pluronic F-68, F-84 and P-103; cyclodextrin; or other agents known to those skilled in the art. Such co-solvents are typically employed at a level of from 0.01% to 2% by weight.

Viscosity greater than that of simple aqueous solutions may be desirable to increase ocular absorption of the active compound, to decrease variability in dispensing the formulations, to decrease physical separation of components of a suspension or emulsion of formulation and/or otherwise to improve the ophthalmic formulation. Such viscosity building agents include, for example, 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 pharmaceutical compositions containing one or more compounds of Formula (I) may be used to treat patients afflicted with or prone to various types of cellular damage. The concentrations of the compounds in the compositions will depend on various factors, including the nature of the condition to be treated with the compositions. However, the compositions will generally contain one or more of the compounds in a concentration of from about 0.001 to about 5 percent by weight, based on the total weight of the composition ("wt.%").

The route of administration (e.g., topical, parenteral or oral) and the dosage regimen will be determined by skilled clinicians, based on factors such as the exact nature of the condition being treated, the severity of the condition, the age and general physical condition of the patient, and so on.

As indicated above, use of the compounds of Formula (I) to prevent or reduce damage to ophthalmic tissues at the cellular level is a particularly important aspect of the present invention. Ophthalmic conditions which may be treated include, but are not limited to, cataracts, retinopathies, heredodegenerative diseases, macular degeneration, ocular ischemia, neovascular diseases, glaucoma, and damage associated with injuries to ophthalmic tissues, such as ischemia reperfusion injuries, photochemical injuries, and injuries associated with ocular surgery, particularly injuries to the retina, cornea or other tissues caused by exposure to light or surgical instruments. The compounds may also be used as an adjunct to ophthalmic surgery, such as by vitreal or subconjunctival injection following ophthalmic surgery. The compounds may be used for acute treatment of temporary conditions, or may be administered chronically, especially in the case of degenerative disease. The compounds may also be used prophylactically, especially prior to ocular surgery or noninvasive ophthalmic procedures, or other types of surgery.

The use of physiologically balanced irrigating solutions as pharmaceutical vehicles for the compounds of Formula (I) is preferred when the compounds are administered intraocularly. As utilized herein, the term "physiologically balanced irrigating solution" means a solution which is adapted to maintain the physical structure and function of tissues during invasive or noninvasive medical procedures. This type of solution will typically contain electrolytes, such as sodium, potassium, calcium, magnesium and/or chloride; an energy source, such as dextrose; and a buffer to maintain the pH of the solution at or near physiological levels. Various solutions of this type are known (e.g., Lactated Ringers Solution). BSS® Sterile Irrigating Solution and BSS Plus® Sterile Intraocular Irrigating Solution (Alcon Laboratories, Inc., Fort Worth, Texas, USA) are examples of physiologically balanced intraocular irrigating solutions. The latter type of solution is described in United States Patent No. 4,550,022 (Garabedian, et al.), the entire contents of which are hereby incorporated in the present specification by reference.

The doses utilized for any of the above-described purposes will generally be from about 0.01 to about 100 milligrams per kilogram of body weight ("mg/kg"), administered one to four times per day.

Formulations

The following formulation is provided to further illustrate the pharmaceutical compositions of the present invention, particularly compositions intended for topical application to the eye. In this example, the term "Compound" is intended to represent any of the compounds of Formula (I).

Compound (free base)	1.0	Active ingredient
Polyvinyl alcohol, USP	1.4	Excipient
Monobasic sodium phosphate (Monohydrate), USP	0.05	Buffering agent
Dibasic sodium phosphate (Anhydrous), USP	0.15	Buffering agent
Sodium chloride, USP	0.5	Tonicity agent
Disodium EDTA (Edetate disodium), USP	0.01	Preservative
Polysorbate 80, NF	0.05	Surfactant
Benzalkonium chloride solution, NF	0.01 + 5 excess	Preservative
Sodium hydroxide, NF	q.s.	pH adjustment
Hydrochloric acid, NF	q.s.	pH adjustment
Water for injection, USP	q.s. 100	Vehicle

Claims (15)

1. A compound of the formula:         A - Y - B wherein:

   A is an antioxidant selected from: wherein

   R is C₁ to C₆ alkyl,

   Y is (CH₂)_n or CH=CH(CH₂)_n, wherein n is a whole number of from 1 to 6; and

   B is selected from:

   wherein:

   n' is a whole number of from 1 to 6;

   Z is H, CN or OH;

   X is F, Cl, I, Br, OH, OR', SH, S(O)_mR',

   CN or NO₂, wherein R' is C₁ to C₆ alkyl and m is 0, 1 or 2; and

   o is 0, 1, 2 or 3,

   or a pharmaceutically acceptable salt thereof,
2. A pharmaceutical composition for preventing or alleviating damage to mammalian tissues, comprising an amount of a compound of the following formula effective to decrease free radical or oxidative damage and control intracellular free calcium levels in said tissues:         A - Y - B wherein:

   A is an antioxidant selected from: wherein R is C₁ to C₆ alkyl,

   Y is (CH₂)_n or CH=CH(CH₂)_n, wherein n is a whole number of from 1 to 6; and

   B is selected from:

   wherein:

   n'is a whole number of from 1 to 6;

   Z is H, CN or OH;

   X is F, Cl, I, Br, OH, OR', SH, S(O)_mR', CN or NO₂, wherein R' is C₁ to C₆ alkyl

   and m is 0, 1 or 2; and

   o is 0, 1, 2 or 3,

   or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable vehicle therefor.
3. A compound according to Claim 1 or a composition according to Claim 2, wherein Z (if present) is H or OH; and X is F, Cl, CN, S(O)_mR' or OR', wherein m is 1 or 2 and R' is C₁ to C₄ alkyl.
4. A compound according to Claim 1 or Claim 3 or a composition according to Claim 2 or Claim 3 wherein the antioxidant A is;    wherein R is C₁ to C₆ alkyl
5. A compound according to any one of Claims 1, 3, or 4 or a composition according to any one of Claims 2 to 4, wherein R is methyl.
6. A compound according to Claim 1 or any one of Claims 3 to 5 or a composition according to any one of Claims 2 to 5, wherein B is
7. A compound according to Claim 1 or any one of Claims 3 to 6 or a composition according to any one of Claims 2 to 6 wherein X is F, Cl, CN, S(O)_mR', or OR', wherein m is 1 or 2 and R' is C₁ to C₄ alkyl.
8. A compound according to Claim 1 or any one of Claims 3 to 7 or a composition according to any one of Claims 2 to 7 wherein Y is (CH₂)_n and wherein n is a whole number of from 1 to 6.
9. A compound or a composition according to Claim 8 wherein n is 1 or 2.
10. A compound or a composition according to Claim 9 wherein the compound has the following formula.
11. A compound or a composition according to Claim 9 wherein the compound has the following formula:
12. A composition as claimed in any one of claims 2 to 11 wherein the pharmaceutically acceptable vehicle comprises a physiologically balanced irrigating solution.
13. A compound as claimed in any one of claims 1 or 3 to 11 or a composition as claimed in any one of claims 2 to 12 for use in the prevention or alleviation of damage to mammalian tissues by decreasing free radical or oxidative damage and control of intracellular free calcium levels in the tissues.
14. A compound or a composition as claimed in Claim 13 wherein the mammalian tissues are ophthalmic tissues.
15. A compound or a composition as claimed in Claim 14 wherein the use is by topical application, optionally in conjunction with ophthalmic surgical procedure.