USING OPTICALLY PURE R-OR RR-ISOMERS OF

ADRENERGIC BETA-2 AGONISTS

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a method of improving retinal blood flow, and decreasing intraocular pressure by administering a pure eutomer of an adrenergic beta-2 agonist (ex albuterol, terbutaline, salmeterol, fenoterol, formoterol), while eliminating all side effects associated with the distomer

2. Background Art

Many biologically active molecules exists as enantiomers Although structurally identical, enantiomers can have different effects in biological systems one enantiomer may have specific therapeutic activities, while the other enantiomer may have no therapeutic activity or may have entirely different biological activities

The form in which adrenergic beta-2 agonists presently are used are as racemic mixtures of two isomers (e g , R- and S-albuterol, R- and S-terbutaline, R-and S-salmeterol, RR- and SS-fenoterol, and RR- and SS -formoterol) An R-isomer of a racemic compound is structurally identical to the S-isomer and the isomers differ only in that one isomer is a mirror image of the other When a molecule has two chiral centers, there are four possible isomers, called RR, SS, RS, and SR The commercially available racemic beta-agonists formoterol and fenoterol each have two chiral centers and each consists of a mixture of an RR-isomer (50%) together with an SS-isomer (50%)

Prior art teaches that non-beta-active isomers of various beta-agonists (I e S- terbutaline, S-albuterol, etc ) loweis intraocular pressure This observation seems not to have been verified and the compounds have not found clinical usefulness (US Pat 3,885,047 to Dungan, et al , 1973)

All drugs against glaucoma have side effects, thus adrenergic betablockers cannot be used in patients with asthma or in patients with heart problems Adrenergic agonists like epinephπne and isoprenaline can cause incapacitating irritation ("burning"), discomfort, dryness, itching, hypotony, blurred or dimmed vision, allergic responses, conjunctival microhemorrhages, cardiovascular effects, CNS effects and upon repeated administration of sympathomimetic drugs to the eye, increased ocular pressure is a very serious side effect,

particularly in individuals with pre-existing glaucoma (Potter et al Ocular hypertensive response to beta-adrenoceptor agonists Curr Eye Res (Engl) 1982, 83 71 1-719)

It is therefore of substantial interest to identify compounds that decrease the intracellular smooth muscle calcium ion concentration and thereby relax the smooth muscle cells of the retinal blood vessels Such drugs are believed to be useful in therapeutic or prophylactic treatment of patients suffering from vasculopathies and neuropathies associated with the eye Furthermore, it is important that such drugs do not increase intracellular calcium ion concentrations and thereby cause contraction of the ietinal smooth muscle cells which will lead to obstruction of retinal blood flow It is therefore an objective of the present invention to provide a method for treating retinal ischemia and glaucoma which is safe, effective, and has minimum side effects

DISCLOSURE OF THE INVENTION

The present invention provides a method of improving retinal blood flow, and decreasing intraocular pressure, by administering a pure eutomer of an adrenergic beta-2 agonist (ex albuterol, terbutaline, salmeterol, fenoterol, formoterol) while eliminating all side effects associated with the distomer The method is particularly useful in ti eating subjects that have various forms of retinal vasculopathy, ischemia or glaucoma induced by known or unknown causes In these cases, it is important to have a therapeutic composition that does not cause an increase of the intracellular smooth muscle calcium or intraocular pressure or induce vascular constriction and thereby worsen the lschemic condition of the eye and does not exhibit other adverse side effects

The present method provides a safe, effective method for treating individuals suffering from retinal vasculopathy or glaucoma while reducing undesirable side effects, for example tremor, nervousness shakiness, dizziness, increased appetite, cardiac tachycardia, bronchial hyperactivity, and particularly ocular hypertension and ocular vasoconstπctions or ocular vasospasms, associated with the distomers of adrenergic beta-2 stimulating diugs

BEST MODE OF THE INVENTION The present invention relies on the therapeutic activity of the eutomer of a beta-agonist to provide relief from ocular conditions such as retinal vasculopathy, retinal ischemia and glaucoma As explained below, a decrease in intracellular smooth muscle calcium

concentration leads to a smooth muscle relaxation and retinal vasodilatation, while an increase in intracellular calcium causes augmented smooth muscle contractility

The present composition and method provide a safe, effective method for treating individuals suffering from retinal vasculopathy, retinal ischemia, or glaucoma, while reducing the highly undesirable side effects

The method for treating retinal vasculopathy or retinal ischemia comprises contacting the surface of the eye with a composition, comprising a therapeutically effective amount of an

R- or RR-isomer of an adrenergic beta-2 receptor agonist so as to improve the retinal blood flow and maintain it on an improved level The method for treating glaucoma comprises contacting the surface of the eye with a composition, comprising an effective amount of an R- or RR-isomer of an adrenergic beta-2 receptor agonist, so as to reduce or normalize the intraocular pressure

The R-isomer of albuterol, terbutaline and salmeterol carry all the beta-2 agonistic activity (eutomer) while the S-isomer has no affinity for adrenergic beta-2 receptors (distomer) In the cases of formoterol and fenoterol, the RR-isomers are eutomers and the SS-isomers are distomers

The R-isomer of albuterol as used herein refers to the optically pure isomer of al [(tert- butylamino) methyl]-4hydroxy-m-xylene-a, a' -diol, and to any biologically acceptable salt or ester thereof The RR-isomer of fenoterol as used herein refers to the optically pure RR- isomer of l-(3,5-dιhydroxyphenyl)-l-hydroxy-2[(4-hydroxyphenyl) ιsopropylamιno]ethane, and to any biologically acceptable salt or ester thereof The RR-isomer of formoterol as used herein refers to the optically pure isomer of (+/-)-2'-hydroxy-5 ^, -[(RS)-l-hydroxy-2-[[(RS)-/?- methoxy-a-methylphenethyl]amιno]ethyl]-formanιlιde, and to any biologically acceptable salt or ester thereof The R-isomer of terbutaline as used herein refers to the optically pure isomer of !-(3,5-dιhydroxyphenyl)-2-(tert-butylamιno)ethanol, and to any biologically acceptable salt or ester thereof The R-isomer of salmeterol as used herein refeis to the optically pure isomer of (+/-)-4-hydroxy-a'-[[[6-(4-phenylbutoxy)-hexyl]amιnoJmethyl ]-/»-xylene-a, a'-diol, and to any biologically acceptable salt or ester thereof

The term "optically pure" or "substantially free of the S- or SS- enantiomer' as used herein means that the composition contains at least 85% by weight of the R- or RR-isomer of a beta-agonist and 15% by weight or less of the S- or SS-isomer It is known to those skilled in the art that optical purity is often 99% or higher

Optically pure adrenergic beta-agonists are readily obtainable by methods known to those skilled in the art, for example, by synthesis from an optically pure intermediate or resolution of the racemic compound into its isomers

By the term "effective amount" of a compound, product, or composition as provided herein is meant a sufficient amount of the compound, product or composition to provide the desired result As will be pointed out below, the exact amount required will vary, depending on the particular compound, oi composition used, its mode of administration, and the like

Thus, it is not always possible to specify an exact "effective amount " However, an appropriate effective amount may be determined by one of ordinary skill in the art using only routine experimentation

Retinal vascular disease and ischemia are associated with malfunction of neuroendocπne regulation and autoregulation of the choroidal and retina] circulations, respectively It has been postulated that excessive elevation of intracellular calcium (calcium overload) in the smooth muscle of retinal blood vessels and in neurons may be involved in the pathogenesis of retinal vasculopathy, ischemia and ultimately, retinal damage Edema of the retina or optic nerve can follow or accompany the aforementioned ischemia Some specific pathologic events triggered by excess intracellular calcium ions include generation of free radicals, activation of proteases, endonucleases and lipases, and interference with energy production in mitochondria Blood flow to the retina is supplied by two separate vascular systems the retinal vessels supplying the inner retinal layers and choroidal vessels supplying the outer retinal layers In primates, approximately 35% of the total retinal blood flow is derived from the retinal vessels, while 65% is derived from the choroidal vessels Although the choroidal blood flow is of greater magnitude, retinal ischemia is usually associated with a reduction of flow in the inner retinal vessels This greater propensity for ischemia in the inner retina may result from several factors (1) the high rate of choroidal blood flow over that required to meet the metabolic needs of the outer retina, (2) the large diameter capillaries in the choroid are less likely to be occluded by emboli, (3) the lack of anastomoses in the retinal vessels, and (4) the larger percentage of oxygen extracted from the retinal arteπoles/capillaπes ( %) as compared to the choroidal circulation (3-4%) To maintain an adequate supply of nutrients to the inner retina under various systemic and ocular conditions, blood flow through normal ietinal vessels

is highly autoregulated by metabolic (oxygen and carbon dioxide), myougenic and possibly local hormonal (paracπne and autocπne) factors

A number of systemic and ocular disorders have been associated with lschemic conditions of the retina or optic nerve Ocular manifestations of systemic disorders include diabetes, atherosclerosis, hyperlipidemia, and hypertension Specific ocular disorders include retinitis of ALUs, macular degeneration, anterior lschemic optic neuropathy, ocular hypertension, glaucoma, retinopathy of prematurity, retinal vessel occlusion, diabetic retmopathy, and hypertensive retinopathy In addition, edemic conditions of the retina or optic nerve are evidenced in diabetes, hypertension and cyctoid macular edema Evidence demonstrates that excessively high concentrations of intracellular calcium ions in smooth muscle cells of vascular tissues and in neuronal tissue ("calcium overload") is a primary contributor to the pathogenesis of lschemic injury and the development of vasculopathy and neuropathy

Although the drugs that are presently used in the treatment of glaucoma are generally effective, they have known side effects that may be dangerous to the patient Thus, adrenergic beta blockers such as timolol cannot be used in patients with concomitant asthma or heart problem Epinephπne may cause systemic side effects such as increased blood pressure and increased heart rate, faintness, and headaches The local side effects of epinephπne include irritation ("burning"), slow wound healing, pigment deposition and eyelash loss Particularly old solutions of epinephπne, containing oxidized epinephπne may have very severe local side effects such as a very marked and incapacitating burning sensation, sometimes accompanied by tearing and conjunctival deposits of pigment The reported side effects of alpha adrenergic agents include systemic gastrointestinal, cardiovascular, and central nervous system side effects The local side effects of alpha adrenergic drugs include ocular burning, foreign body sensation, dryness, itching, blurred or dimmed vision, and conjunctival microhemorrhages The use of carbonic anhydrase inhibitor in glaucoma may give some patients significant malaise, fatigue, depression, paresthesias and nephrolithiasis A newer carbonic anhydrase inhibitor is still being investigated

Glaucoma of the eye is characterized by increased intraocular pressure The most common cause of glaucoma is restricted outflow of aqueous fluid (humor) from the anterior chamber of the eye through Schlemm's canal, the trabecular meshwork and the aqueous veins

If untreated, glaucoma can cause excavation and degeneration of the optic disc and nerve damage, producing vision defects and eventual blindness

Glaucoma may have different causes Angle-closure glaucoma occurs because the outflow of aqueous humor is prevented by contact of the ins with the trabecular drainage meshwork and peripheral cornea Capsu/ar glaucoma occurs in association with deposition of degenerative substances on the lens capsule, ocular blood vessels, ins and ciliary body orticoster id-induced glaucoma is due to increased intraocular pressure aftei local installation of corticosteroids to the eye Other types of glaucoma include hypersecretion glaucoma due to excessive formation of aqueous humor, malignant glaucoma due to forward displacement of the ins and lens obliterating the anterior chamber, and open-angle glaucoma, due to the aqueous humor having free access to the trabecular meshwork

Glaucoma is treated with surgery or with antiglaucoma medication Medication include parasympathomimetic agents (ex pilocarpine) and cholinesterase inhibitors (e g , echothiphate) that increase the outflow of aqueous humor to decrease pressui e, adrenergic beta-blockers (e g , timolol) that reduce the rate of humor formation and beta-agonists (e g , epinephπne) that increase the outflow of humor from the eye

The therapeutic action of beta-2 adrenergic drugs is to activate adrenergic beta-2 receptors and thereby initiate cellular responses, the most well-known is the relaxation of bronchial smooth muscles Racemic beta-2 agonists are commonly used to treat bronchial spasms associated with asthma These drugs have also been used to decrease high intraocular pressure (glaucoma) but when used for this indication, the drugs have been shown to carry certain side-effects

It was surprisingly found that the optically pure eutomer of n adrenergic beta-2 agonist was more effective in decreasing intracellulai smooth muscle calcium concentration than its corresponding racemate, which actually was found to increase intracellular calcium It was also found that the distomer of adrenergic beta-2 agonists can increase intracellular calcium concentration and cause smooth muscle contractions or augment smooth muscle contractions In these experiments, single smooth muscle cells are dissociated from the tissues by incubation with a mixture of collagenase and elastase The cells are loaded with 0 5μM fura-2, thereafter placed under an inverted microscope and illuminated by short bursts of UV light Fluorescence images are captured by a camera and digitized The intracellular calcium concentration is determined as described by Grynkiewitcz et al (1985) J Biol Chem 260-

3340-3350 In other experiments, strips of smooth muscle tissues are mounted in tissue baths and contracted by spasmogens before and after exposure to the single isomers or the racemates of adrenergic beta-2 agonists

In the present method, the R- or the RR-isomer of a beta agonist is administered to an individual, who suffers from retinal vasculopathy, retinal ischemia or glaucoma For example,

R-albuterol or RR-formoterol is administered to an individual after the onset of the condition to reduce or eliminate the condition In another embodiment, an optically pure R- or RR- isomer of a beta-agonist is administered prophylactically, that is, before the unwanted ocular condition begins, to prevent its occurrence or to reduce the extent to which it occurs As used herein, the term "treating" shall include both remedial and prophylactic administration

In the present method, the optically active R- or RR-isomer of a beta-agonist can be administered topically to the eye as a solution, suspension or ointment The ophthalmically compatible carrier which may be used in this invention comprises e g an aqueous solution, such as saline solution, oil solution or ointments containing ophthalmically compatible preservatives, surfactants, buffers and agents such as polymers to increase the viscosity Also drug inserts either soluble or insoluble may be used The drug can also be administered by inhalation, parenterally, subcutaneoulsy, intravenously, intramuscularly or other injection or by infusion, orally, sub ngually, transdermally, vagmally, rectally or via an implanted reservoir containing the drug The form in which the drug will be administered (e g inhalant, powder, tablet, capsule, solution, emulsion, ointment, etc ) will depend on the route by which it is administered

The quantity of the drug to be administered will be determined on an individual basis, and will be based on the pharmacological potency of the drug, the route of administration and at least in part on the consideration of the individual's size, the severity of the symptoms to be treated and the results sought In general, quantities of optically a pure eutomer sufficient to eliminate the unwanted ocular condition will be administered The actual dosage (quantity administered at a time) and the number of administrations per day will depend on the pharmacokinetic property of the drug and the mode of drug administrations, for example, by topical doses of solution, suspension or ointment to the eye, by transdermal applications, by inhalers such as nebulizer, metered dose inhalers or dry powder inhalers or by the oral or sublingual route of administration

For example, about 10 to 3,000 meg of the optically pure R(-)-isomer of albuterol given topically to the eye or by various forms of inhalation devices (metered dose inhalers, dry powder inhalers, nebulizers etc ), 1 to 50 mg given by the oral route (tablets, caplets, controlled release formulations, sublingual formulations, etc ) once or more times per day may be adequate in most individuals to produce the desired effect For oral administration of R- albuterol, e g tablet or syrup, a does of about 1 mg to about 15 mg one to four times daily is administered to produce the desired effect Controlled-release, sustained-release or delayed release formulations of R-albuterol, containing 4 mg to 50 mg may be used to obtain controlled, sustained or delayed therapeutic effect If a more potent compound or a compound with longer duration of therapeutic activity than R-albuterol is chosen, the dose and the dosing frequency will be decreased Thus the does of RR-formoterol may be half or less than half the does of R-albuterol and the dosing may also be less frequent

The optically pure R- or RR-isomer os a beta-2 agonist can be administered together with one or more auxiliary pharmaceuticals For example, parasympathomimetics, chohnesterase inhibitors, carbonic anhydrase inhibitors, prostaglandins, prostaglandin-like compounds, metabolic sulfation inhibitors, thromboxane atagonists, thromboxane blockers, PAF atagonists, PAF blockers, steroids, sympathomimetics, sympatholytics, andrenegic beta- blockers, and ganglion blockers can be administered with or between the doses of the selected beta-2 agonistic eutomer The eutomer of a short-acting beta-agonist (e g , R-albuterol) can be combined with the eutomer of a long-acting beta-agonist (e g , R-salmeterol) Compounds that improve or prolong the therapeutic effect of the selected eutomer, e g, compounds that inhibit the metabolic degredation of the selected eutomer (e g , acetominophen), may also be co- administered to patients given the selected eutomer Two or more drugs can be administered in one composition or administered separately For example, they can be administered in an eye drop formulation, in capsule, tablet, powder form, or as a liquid, mist aerosol, injection, transdermal delivery system The components included in a particular formulation in addition to the optically pure eutomer are determined primarily by the manner in which the composition is to be administered For example, a composition to be administered as an inhalant can include a liquid carrier or propellant Compositions in tablet for may include a filler (e g , lactose), a binder (e g , carboxymethyl cellulose, gum arable, and/or gelatin), an adjuvant, a flovoring agent, a coloring agent, and a coating material such as wax or a pla ticizer

Formulations in liquid form may include an emulsifying agent, a flavoring agent, and/or a coloring agent.

In general, the optically pure eutomer of a beta-agonist, such as R-albuterol, R- terbutaline, R-salmeterol, R-fenoterol, or R-formoterol, alone or in combination with an auxialiary pharmaceutical, is administered to an individual, periodically, as necessary, to cause therapeutic improvement of retinal vasculopathy, or retinal ischemia, and/or to reduce intraocular pressure

EXAMPLE

Intraocular pressure was measured in the rabbit eye after topical drug administration into the conjuctival sac. Elevated intraocular pressure was obtained by intravenous injection of glucose ( 5ml /kgof 5% glucose over 20 sec ) The effects on intraocular pressure of increasing concentrations of R-albuterol and of the adrenergive beta-receptor blocking drug

Timolol were studies in parallel in the conscious rabbits Measurements were made at the time point where intraocular pressure (IOP) was highest in the untreated control animals ( 10- 15 minutes agyer glucose injection) The results shown in Table 1 indicate that R-albuterol effectively reduced intraocular pressure at a concentration of 0 875 mg/ml while a concentration in excess of 6 8 mg/ml of timolol was needed to obtain a similar effect

TABLE 1

Test Compound Cone (mg/ml) Change in IOP (%)

Vehicle — +25 9

R-albuterol 0 875 +3 2

R-albuterol 3.5 +3 4

Vehicle — 425 9

R-albuterol 14.00 - 12 3

Vehicle ~ +32. 1

Timolol 3.5 +25 0

Timolol 6.80 +6 6

Timolol 14.00 - 18 6

Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, many eqivalents to the specific embodiments of the invention described herein Such equivalents are inteded to be encompassed in the scope of the following claims