The present invention relates to the treatment of glaucoma and ocular hypertension.

In particular, the present invention relates to the use of certain prostaglandin D-series

compounds to treat glaucoma and hypertension.

Background ofthe Invention

Glaucoma is a progressive disease which leads to optic nerve damage, and,

ultimately, total loss of vision. The causes of this disease have been the subject of extensive

studies for many years, but are still not fully understood. The principal symptom of and/or

risk factor for the disease is elevated intraocular pressure or ocular hypertension due to

excess aqueous humor in the anterior chamber ofthe eye.

The reasons why aqueous humor accumulates are not fully understood. It is known

that the elevated intraocular pressure ("IOP") can be at least partially controlled by

administering drugs which reduce either the production of aqueous humor within the eye,

such as beta-blockers and carbonic anhydrase inhibitors, or increase the flow of aqueous

humor out ofthe eye, such as miotics and sympathomimetics.

All types of drugs currently being used to treat glaucoma have potentially serious

side effects. Miotics such as pilocarpine can cause blurring of vision and other visual side

effects, which may lead either to decreased patient compliance or to termination of therapy.

Systemically administered carbonic anhydrase inhibitors can also cause serious side effects,

such as nausea, dyspepsia, fatigue, and metabolic acidosis which can affect patient

compliance and/or necessitate the withdrawal of treatment. Moreover, some beta-blockers have increasingly become associated with serious pulmonary side effects attributable to their effects on beta-2 receptors in pulmonary tissue. Sympathomimetics cause tachycardia,

arrhythmia and hypertension. There is therefore a continuing need for therapies which control the elevated intraocular pressure associated with glaucoma.

Prostaglandins, which are metabolite derivatives of arachidonic acid, have recently been pursued for possible efficacy in lowering IOP. The arachidonic acid cascade is initiated by the conversion of arachidonic acid to prostaglandin G ₂ and subsequent conversion to prostaglandin H ₂ . Other naturally occurring prostaglandins are derivatives of prostaglandin H ₂ . A number of different types of prostaglandins have been discovered including A, B, D, E, F and I-Series prostaglandins. Of interest in the present invention are compounds which exhibit similar IOP lowering mechanisms as PGD (a D-series prostaglandin) shown in formula (I):

HO

The relationship of PGD ₂ receptor activation and IOP lowering effects is not well known, but the IOP lowering effect is thought to be due to activation of the PGD ₂ receptor. Various publications have reported that PGD ₂ receptor activation leads to second messenger activation and in particular, to the stimulation of adenylate cyclase and resultant increases in cAMP levels (Thierauch, Prostaglandins and their Receptors: II. Receptor Structure and Signal Transduction, Journal of Hypertension, volume 12, pages 1- 5 (1994). Regardless of mechanism, PGD ₂ has been shown to lower IOP (Nakajima,

Effects of Prostaglandin D ₂ and its analogue, BW245C, on Intraocular Pressure in

Humans, Graefe's Archive Ophthalmology, volume 229, pages 411-413 (1991)). Thus, it

has been of interest in the field to develop synthetic PGD ₂ analogs with IOP lowering efficacy. Synthetic PGD ₂ -type analogs have been pursued in the art (Graefe's Archive

Ophthalmology, volume 229, pages 411-413 (1991)). Though PGD ₂ , BW245C and these synthetic analogs lower IOP, they have also been associated with undesirable side effects which are thought to arise from activation of other prostaglandin receptors within the eye. Such effects include an initial increase in IOP, conjunctival hyperemia, increases in microvascular permeability, and increases in eosinophile infiltration (Aim, The Potential of Prostaglandin Derivatives in Glaucoma Therapy, Current Opinion in Ophthalmology. volume 4, No. 11, pages 44-50 (1993)). The activation of the PGD ₂ receptor with other types of molecules may lead to IOP lowering effects, but with fewer or reduced side effects

as those analogs discussed above. Therefore, a need exists for the development of agonists that will bind the PGD ₂ receptor, which are more efficacious in lowering IOP and exhibiting fewer or reduced side effects.

Certain 3-oxa-D-prostaglandins have been disclosed in WIPO Publication No. WO 94/05631.

Summary ofthe Invention

The present invention is directed to compositions and methods of their use in treating IOP and ocular hypertension. In particular, the present invention provides certain

classes of 3-Oxa-D-prostaglandins having functional PGD receptor agonist activity, and methods of their use in treating glaucoma and ocular hypertension

Detailed Description ofthe Invention

It has unexpectedly been found that 3-Oxa-D-prostaglandins ("3-O-DP") are more efficacious in lowering and controlling IOP than their 3 -carba analogs Consequently, these 3-O-DPs can be administered at lower doses than their 3 -carba analogs. The lower doses are believed to reduce their activity on other prostaglandin receptors and thereby reduce many ofthe aforementioned undesirable side effects

The 3-O-DPs of the present invention are functionally defined by their ability to bind to prostaglandin-D ₂ receptors of cells and evoke similar responses as when PGD ₂ binds to these receptors. As used herein, "DP-agonists" refer to any agent which will bind to PGD ₂ receptors and evoke cellular action in a similar way as PGD ₂ , to the extent that the binding leads to the lowering of IOP Various assays may be used for the determination of DP -agonists, including those described below

Binding assays may be used to elucidate DP-agonists of the present invention Sharif has described a receptor binding assay in. Sharif, N.A , Williams, G.W and DeSantis, L.M , Neurochemistrv Research, volume 20, pages 669-674 (1995), the entire contents of which are incorporated herein by reference, and may be modified as described below, for the elucidation of DP-agonists of the present invention Briefly, the binding

assays are conducted in 25 mM Tris HCl (pH 7 4) containing 138 mM NaCl, 5 mM MgCl2,

and 1 mM EDTA Frozen-thawed expired human blood platelets (40-60 mg/ml stock) are

incubated in a total volume of 500 μl with 2-10 nM [*--H]PGD2 in the absence and presence

of 100 μM unlabeled PGD2 to define total and non-specific binding, respectively. The

incubations (20 minutes at 23 °C) are terminated by rapid vacuum filtration, using a Whatman GF/B glass fiber filter previously soaked in 1% polyethyleneimine and 0.1% BSA, and the receptor-bound radioactivity is then determined by scintillation spectrometry. The binding data are analyzed using a non-linear, iterative curve-fitting computer program to define the receptor binding affinity (Ki) ofthe compounds. Compounds which exhibit K, values in this assay of less than or equal to about 20 μM are within the definition of DP- agonists ofthe present invention. The DP-agonists ofthe present invention may also be defined functionally, by their ability to stimulate adenylate cyclase activity. Sharif has described this type of functional assay in: Sharif, N.A., Xu, S. and Yanni, J.M., Journal of Ocular Pharmacology, volume 10, pages 653-664 (1994), the entire contents of which are incorporated herein by reference, and which may be modified as described below, for the elucidation of DP- agonists of the present invention. Briefly, functional adenylate cyclase activity is determined using embryonic bovine tracheal cells (EbTr) cells. Cultured cells are

stimulated with the test compound for 15 minutes at 23 °C. The reaction is then stopped

and the cAMP generated is determined by a radioimmunoassay kit. Data are analyzed using a non-linear, iterative curve-fitting computer program to define the potency ("EC ₅₀ ", concentration which produces 50% ofthe maximum response of PGD ₂ ) and efficacy ofthe

compounds. Compounds which exhibit EC ₅₀ values of less than or equal to about 10 μM

are within the DP-agonist definition ofthe present invention.

The 3-O-DPs of the present invention are within the preceding DP-agonist definition, and are ofthe following formula (II):

wherein:

Ri is H, alkyl or alkylcycloalkyl;

R ₂ is alkyl, cycloalkyl or alkylcycloalkyl; and

G is

wherein:

R ₃ is H, OH or alkyl;

— represents a single bond or double bond; provided that double bonds between the 13 and 14 positions are in the trans configuration; and pharmaceutically acceptable salts thereof.

Preferred DP-agonists of the present invention are those containing esters (i.e., R- is alkyl or alkylcycloalkyl), and wherein R ₂ is cyclohexyl. Most preferred compounds of the present invention are those wherein R- is isopropyl. Some of the 3-O-DPs of the present invention are believed to be novel.

The 3-O-DPs, wherein G is formula (i), are described in Barraclough, Synthesis and Platelet Aggregation Inhibiting Activity of Acid Side-chain Modified Hydantoin Prostaglandin Analogues, Archives in Pharmacology, volume 326, No. 2, pages 85-95 (1993), the entire contents of which are incorporated herein by reference.

The 3-O-DPs, wherein G is formula (ii), may be prepared from [lS-[lα, 2α(Z), 3α

(IE, 3S), 4α]]-7-[3-(3-Cyclohexyl-3-hydroxy-l-propenyl)-7-oxabicyclo[ 2.2.1]hept-2-yl]-5-

heptenoic acid following the procedure described in Das, 9,ll-Epoxy-9-homoprosta-5- enoic Acid Analogues as Thromboxane A Receptor Antagonists, Journal of Medicinal

Chemistry, volume 33, No. 6, pages 1741-1748 (1990), for the conversion of [lS-[lα,

2α(Z), 3α (IE, 3S, 4R)), 4α]]-7-[3-[4-phenyl-3-(tetrahydropyran-2-yloxy)-l-pentyl]-7 -

oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid to [\S-[\a, 2α(Z), 3α (IE, 35, 4R)), 4α]]-

[[4-[3-(3-hydroxy-4-phenyl- 1 -pentyl)-7-oxabicyclo[2.2.1 ]hept-2-yl]-5-heptenoic acid.

The 3-O-DPs, wherein G is formula (iii), may be prepared from (5Z, \3E)-9S, 1 IR, 15.S)-15 cyclohexyl-9-hydroxy-3-oxa-l l,15-bis (tetrahydropyran-2-yloxy)-16, 17, 18, 19, 20-pentanor -5,13-prostanoic acid tert butyl ester (ΕP 299 914) by the method described in Bundy, Synthesis and Platelet Aggregation Inhibiting Activity of Prostaglandin D Analogues, Journal of Medicinal Chemistry, volume 26, pages 790-799 (1983), the entire contents of which are incoφorated herein by reference.

The 3-O-DPs of the present invention may be formulated in various pharmaceutical compositions for administering to humans and other mammals as a treatment of glaucoma or ocular hypertension.

The compounds of formula (II) are useful in lowering intraocular pressure and thus are useful in the treatment of glaucoma. As used herein, the term "pharmaceutically

effective amount" refers to that amount of a compound of the present invention which lowers IOP when administered to a mammal. The preferred route of administration is

topical. The compounds of the present invention can be administered as solutions, suspensions, or emulsions (dispersions) in a suitable ophthalmic vehicle. In forming compositions for topical administration, the compounds of the present invention are generally formulated as between about 0.00003 to about 0.5 percent by weight (wt%) solutions in water at a pH between 4.5 to 7.4. The compounds are preferably formulated as between about 0.0005 to about 0.03 wt% and, most preferably, between about 0.001 and about 0.01 wt%. While the precise regimen is left to the

discretion ofthe clinician, it is recommended that the resulting solution be topically applied by placing one drop in each eye one or two times a day.

Other ingredients which may be desirable to use in the ophthalmic preparations of the present invention include preservatives, co-solvents and viscosity building agents.

Preferred formulations of 3-O-DPs of the present invention include the following Examples 1-3:

Example 1

Ingredient Amount (wt%)

3-O-DP 0.001

Phosphate Buffered Saline 1.0 Polysorbate 80 0.5 Purified water q.s. to 100%

Example 2

Ingredient Amount (wt%)

3-O-DP 0.001

Monobasic sodium phosphate 0.05

Dibasic sodium phosphate 0.15 (anhydrous)

Sodium chloride 0.75

Disodium EDTA (Edetate disodium) 0.05

Cremophor EL 0.1

Benzalkonium chloride 0.01

HCl and/or NaOH pH 7.3 - 7.4

Purified water q.s. to 100%

Example 3

Ingredient Amount ( t%)

3-O-DP 0.0005

Phosphate Buffered Saline 1.0 Hydroxypropyl-β -cyclodextrin 4.0 Purified water q.s. to 100%