WO2001034550A2 - 15-hydroxyeicosatetraenoic acid analogs with enhanced metabolic stability and methods of their use in treating dry eye disorders - Google Patents

Abstract

15-HETE derivatives with enhanced metabolic stability and methods of their use for treating dry eye are disclosed.

Description

15-Hydroxyeicosatetraenoic Acid Analogs with Enhanced Metabolic Stability and Methods of Their Use in Treating Dry Eye Disorders

The present invention is directed to novel hydroxyeicosatetraenoic acid related

compounds, compositions and methods of use. The compounds are particularly useful

in treating dry eye.

Background of the Invention

Dry eye, also known generically as keratoconjunctivitis sicca, is a common

ophthalmological disorder affecting millions of Americans each year. The condition

is particularly widespread among post-menopausal women due to hormonal changes

following the cessation of fertility. Dry eye may afflict an individual with varying

severity. In mild cases, a patient may experience burning, a feeling of dryness, and

persistent irritation such as is often caused by small bodies lodging between the eye

lid and the eye surface. In severe cases, vision may be substantially impaired. Other

diseases, such as Sjogren's disease and cicatricial pemphigoid manifest dry eye

complications.

Although it appears that dry eye may result from a number of unrelated

pathogenic causes, all presentations of the complication share a common effect, that is

the breakdown of the pre-ocular tear film, which results in dehydration of the exposed

outer surface and many of the symptoms outlined above (Lemp, Report of the

National Eye Institute/Industry Workshop on Clinical Trials in Dry Eyes, The CLAO

Journal, volume 21, number 4, pages 221-231 (1995)). Practitioners have taken several approaches to the treatment of dry eye. One

common approach has been to supplement and stabilize the ocular tear film using

so-called artificial tears instilled throughout the day. Other approaches include the use

of ocular inserts that provide a tear substitute or stimulation of endogenous tear

production.

Examples of the tear substitution approach include the use of buffered,

isotonic saline solutions, aqueous solutions containing water soluble polymers that

render the solutions more viscous and thus less easily shed by the eye. Tear reconstitution is also attempted by providing one or more components of the tear film

such as phospholipids and oils. Phospholipid compositions have been shown to be useful in treating dry eye; see, e.g., McCulley and Shine, Tear film structure and dry

eye, Contactologia, volume 20(4), pages 145-49 (1998); and Shine and McCulley,

Keratoconjunctivitis sicca associated with meibomian secretion polar lipid

abnormality, Archives of Ophthalmology, volume 116(7), pages 849-52 (1998). Examples of phospholipid compositions for the treatment of dry eye are disclosed in

United States Patent Nos. 4,131,651 (Shah et al.), 4,370,325 (Packman), 4,409,205

(Shively), 4,744,980 and 4,883,658 (Holly), 4,914,088 (Glonek), 5,075,104 (Gressel

et al.), 5,278,151 (Korb et al.), 5,294,607 (Glonek et al.), 5,371,108 (Korb et al.) and

5,578,586 (Glonek et al.). U.S. Patent No. 5,174,988 (Mautone et al.) discloses

phospholipid drug delivery systems involving phospholipids, propellants and an active

substance.

United States Patent No. 3,991,759 (Urquhart) discloses the use of ocular

inserts in the treatment of dry eye. Other semi-solid therapy has included the administration of carrageenans (United States Patent No. 5,403,841, Lang) which gel

upon contact with naturally occurring tear film.

Another approach involves the provision of lubricating substances in lieu of

artificial tears. For example, United States Patent No. 4,818,537 (Guo) discloses the

use of a lubricating, liposome-based composition, and United States Patent No.

5,800,807 (Hu et al.) discloses compositions containing glycerin and propylene glycol

for treating dry eye.

Aside from the above efforts, which are directed primarily to the alleviation of

symptoms associated with dry eye, methods and compositions directed to treatment of

the dry eye condition have also been pursued. For example, United States Patent No.

5,041,434 (Lubkin) discloses the use of sex steroids, such as conjugated estrogens, to

treat dry eye condition in post-menopausal women; United States Patent No.

5,290,572 (MacKeen) discloses the use of finely divided calcium ion compositions to stimulate pre-ocular tear film production; and United States Patent No. 4,966,773

(Gressel et al.) discloses the use of microfme particles of one or more retinoids for

ocular tissue normalization.

Although these approaches have met with some success, problems in the

treatment of dry eye nevertheless remain. The use of tear substitutes, while

temporarily effective, generally requires repeated application over the course of a

patient's waking hours. It is not uncommon for a patient to have to apply artificial

tear solution ten to twenty times over the course of the day. Such an undertaking is

not only cumbersome and time consuming, but is also potentially very expensive.

Transient symptoms of dry eye associated with refractive surgery have been reported to last in some cases from six weeks to six months or more following

surgery.

The use of ocular inserts is also problematic. Aside from cost, they are often

unwieldy and uncomfortable. Further, as foreign bodies introduced in the eye, they

can be a source of contamination leading to infections. In situations where the insert

does not itself produce and deliver a tear film, artificial tears must still be delivered on

a regular and frequent basis.

Mucins are proteins which are heavily glycosylated with glucosamine-based

moieties. Mucins provide protective and lubricating effects to epithelial cells,

especially those of mucosal membranes. Mucins have been shown to be secreted by

vesicles and discharged on the surface of the conjunctival epithelium of human eyes (Greiner et al., Mucous Secretory Vesicles in Conjunctival Epithelial Cells of Wearers

of Contact Lenses, Archives of Ophthalmology, volume 98, pages 1843-1846 (1980); and Dilly et al., Surface Changes in the Anaesthetic Conjunctiva in Man, with Special

Reference to the Production of Mucous from a Non-Goblet-Cell Source, British

Journal of Ophthalmology, volume 65, pages 833-842 (1981)). A number of human-

derived mucins which reside in the apical and subapical corneal epithelium have been

discovered and cloned (Watanabe et al., Human Corneal and Conjunctival Epithelia

Produce a Mucin-Like Glycoprotein for the Apical Surface, Investigative

Ophthalmology and Visual Science, volume 36, number 2, pages 337-344 (1995)).

Recently, Watanabe discovered a new mucin which is secreted via the cornea apical

and subapical cells as well as the conjunctival epithelium of the human eye (Watanabe

et al., IOVS, volume 36, number 2, pages 337-344 (1995)). These mucins provide lubrication, and additionally attract and hold moisture and sebaceous material for

lubrication and the corneal refraction of light.

Mucins are also produced and secreted in other parts of the body including

lung airway passages, and more specifically from goblet cells interspersed among

tracheal/bronchial epithelial cells. Certain arachidonic acid metabolites have been

shown to stimulate mucin production in these cells. Yanni reported the increased

secretion of mucosal glycoproteins in rat lung by hydroxyeicosatetraenoic acid

("HETE") derivatives (Yanni et al, Effect of Intravenously Administered Lipoxygenase

Metabolites on Rat Trachael Mucous Gel Layer Thickness, International Archives of

Allergy And Applied Immunology, volume 90, pages 307-309 (1989)). Similarly,

Marom has reported the production of mucosal glycoproteins in human lung by HETE

derivatives (Marom et al., Human Airway Monohydroxy- eicosatetraenoic Acid Generation and Mucous Release, Journal of Clinical Investigation, volume 72, pages

122-127 (1983)).

Agents claimed for increasing ocular mucin and/or tear production include

vasoactive intestinal polypeptide (Dartt et. al., Vasoactive intestinal peptide-

stimulated glycocongjugate secretion from conjunctival goblet cells, Experimental

Eye Research, volume 63, pages 27-34, (1996)), gefarnate (Nakmura et. al., Gefarnate

stimulates secretion of mucin-like glycoproteins by corneal epithelium in vitro and

protects corneal epithelium from dessication in vivo, Experimental Eye Research,

volume 65, pages 569-574 (1997)), liposomes (U.S. Patent No. 4,818,537), androgens

(U.S. Patent No. 5,620,921), melanocycte stimulating hormones (U.S. Patent No.

4,868,154), phosphodiesterase inhibitors (U.S. Patent No. 4,753,945), and retinoids

(U.S. Patent No. 5,455,265). However, many of these compounds or treatments suffer from a lack of specificity, efficacy and potency and none of these agents have been

marketed so far as therapeutically useful products to treat dry eye and related ocular

surface diseases.

U.S. Patent No. 5,696,166 (Yanni et al.) discloses compositions containing

naturally occurring HETEs, or derivatives thereof, and methods of use for treating dry

eye. Yanni et al. discovered that compositions comprising HETEs increase ocular

mucin secretion when administered to a patient and are thus useful in treating dry eye.

In view of the foregoing, there is a need for an effective, convenient treatment

for dry eye that is capable of alleviating symptoms, as well as treating the underlying

physical and physiological deficiencies of dry eye.

Summary of the Invention

The present invention is directed to compounds, compositions and methods of use. The present invention is particularly directed to compositions and methods for

the treatment of dry eye and other disorders requiring the wetting of the eye, including

symptoms of dry eye associated with refractive surgery such as LASIK surgery. More

specifically, the present invention discloses derivatives of (5Z,8Z,11Z,13E)-15-

hydroxyeicosa-5,8,ll,13-tetraenoic acid (15-HΕTΕ) in which the ω-chain is modified

as to inhibit metabolic oxidation at C-15. Preferably, the compositions are

administered topically to the eye.

The compounds of the present invention are believed to be more stable than

the naturally occurring HETE-related compounds. Detailed Description of the Invention

The present invention is directed to novel 15-HETE-related derivatives,

compositions and methods of use. It is believed that, among other utilities, the

compounds stimulate ocular mucin production and/or secretion following topical

ocular application and are therefore believed to be useful in treating dry eye. These

compounds are of formula I: wherein:

R¹ is (CH₂)_nCO₂R, (CH₂)_nCONR²R³, (CH₂)_nCH₂OR⁴, (CH₂)_nCH₂NR⁵R⁶, (CH₂)_nCH₂N₃, (CH₂)„CH₂Hal, (CH₂)_nCH₂NO₂, (CH₂)_nCH₂SR²⁰, (CH₂)_nCOSR²¹ or (CH₂)_n-2,3,4,5-tetrazol-l -yl, wherein:

R is H or CO₂R forms a pharmaceutically acceptable salt or a pharmaceutically acceptable ester;

NR²R³ and NR⁵R⁶ are the same or different and comprise a free or functionally modified amino group, e.g., R², R³, R⁵ and R⁶ are the same or different and are H, alkyl, cycloalkyl, aralkyl, aryl, OH, or alkoxy, with the proviso that at most only one of R² and R³ are OH or alkoxy and at most only one of R⁵ and R⁶ are

OH or alkoxy;

OR⁴ comprises a free or functionally modified hydroxy group, e.g., R⁴ is H, acyl; alkyl, cycloalkyl, aralkyl, or aryl;

Hal is F, Cl, Br or I;

SR comprises a free or functionally modified thiol group;

R²¹ is H or COSR²¹ forms a pharmaceutically acceptable salt or a pharmaceutically acceptable thioester;

n is 0 or 2;

A, B, C and D is Cι-C alkyl, alkenyl, or alkynyl or a C -C₅ allenyl group; Y is

wherein R is H or CH₃, and

X is CH₂, CH(CH₃) or C(CH₃)₂; or

Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

or wherein R is H or CH₃, with the proviso that Y cannot be CH₂ when X is

; and R⁷O comprises a free or functionally modified hydroxy group.

The compounds of formula (I) may also be incorporated into phospholipids as glyceryl esters or sphingomyelin amides. Phospholipid sphingomyelin amides of the

compounds of formula (I) will typically comprise a formula (I) compound amidated

via its carbon 1 carboxylate to the amino group of the sphingomyelin backbone. The

phospholipid formula (I) esters will comprise various phospholipids. Phospholipid

esters of the compounds of formula (I) will typically comprise a formula (I) compound

esterified via its carbon 1 carboxylate to the sn-l or sn-2 position alcohol, or both, of

the glycerol backbone of the phospholipid. If the sn-l or sn-2 position of the glyceryl

ester class does not contain an ester of a compound of formula (I), then such carbon positions of the glycerol backbone will comprise a methylene, ether or ester moiety

linked to a substituted or unsubstituted Cι_{2- 0} alkyl or alkenyl (the alkenyl group

containing one or more double bonds); alkyl(cycloalkyl)alkyl; alkyl(cycloalkyl);

alkyl(heteroaryl); alkyl(heteroaryl)alkyl; or alkyl-M-Q; wherein the substitution is

alkyl, halo, hydroxy, or functionally modified hydroxy; M is O or S; and Q is H, alkyl,

alkyl(cycloalkyl)alkyl, alkyl(cycloalkyl), alkyl(heteroaryl) or alkyl(heteroaryl)alkyl.

However, at least one of the sn-l or sn-2 position alcohols of the glycerol backbone

must form an ester with a compound of formula (I) via the carbon 1 carboxylate of the

latter. Preferred phospholipid-formula (I) esters will be of the

phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, and phospatidylinositol type. The most preferred phospholipid-formula (I) esters will

comprise a formula (I) compound esterified via its carbon 1 carboxylate to the alcohol

at the sn-2 position of phosphatidylcholine, phosphatidylethanolamine or phosphatidylinositol. The phospholipid-formula (I) esters and sphingomyelin amides

may be synthesized using various phospholipid synthetic methods known in the art;

see for example, Tsai et al., Biochemistry, volume 27, page 4619 (1988); and Dennis

et al., Biochemistry, volume 32, page 10185 (1993).

Included within the scope of the present invention are the individual

enantiomers of the compounds of the present invention, as well as their racemic and

non-racemic mixtures. The individual enantiomers can be enantioselectively

synthesized from the appropriate enantiomerically pure or enriched starting material

by means such as those described below. Alternatively, they may be

enantioselectively synthesized from racemic/non-racemic or achiral starting materials.

(Asymmetric Synthesis; J. D. Morrison and J. W. Scott, Eds.; Academic Press Publishers: New York, 1983-1985, volumes 1-5; Principles of Asymmetric Synthesis;

R.E. Gawley and J. Aube, Eds.; Elsevier Publishers: Amsterdam, 1996). They may

also be isolated from racemic and non-racemic mixtures by a number of known

methods, e.g. by purification of a sample by chiral HPLC (A Practical Guide to Chiral

Separations by HPLC; G. Subramanian, Ed.; VCH Publishers: New York, 1994;

Chiral Separations by HPLC; A.M. Krstulovic, Ed.; Ellis Horwood Ltd. Publishers,

1989), or by enantioselective hydrolysis of a carboxylic acid ester sample by an

enzyme (Ohno, M.; Otsuka, M. Organic Reactions, volume 37, page 1 (1989)). Those

skilled in the art will appreciate that racemic and non-racemic mixtures may be

obtained by several means, including without limitation, nonenantioselective

synthesis, partial resolution, or even mixing samples having different enantiomeric ratios. Departures may be made from such details within the scope of the

accompanying claims without departing from the principles of the invention and

without sacrificing its advantages. Also included within the scope of the present

invention are the individual isomers substantially free of their respective enantiomers.

As used herein, the terms "pharmaceutically acceptable salt", "pharmaceutically acceptable ester" and pharmaceutically acceptable thioester" means

any salt, ester or thioester, respectively, that would be suitable for therapeutic

administration to a patient by any conventional means without significant deleterious

health consequences; and "ophthalmically acceptable salt", "ophthalmically

acceptable ester" and "ophthalmically acceptable thioester" means any

pharmaceutically acceptable salt, ester or thioester, respectively, that would be

suitable for ophthalmic application, i.e. non-toxic and non-irritating. The term "free hydroxy group" means an OH. The term "functionally

modified hydroxy group" means an OH which has been functionalized to form: an

ether, in which an alkyl, aryl, cycloalkyl, heterocycloalkyl, alkenyl, cycloalkenyl,

heterocycloalkenyl, alkynyl, or heteroaryl group is substituted for the hydrogen; an

ester, in which an acyl group is substituted for the hydrogen; a carbamate, in which an

aminocarbonyl group is substituted for the hydrogen; or a carbonate, in which an

aryloxy-, heteroaryloxy-, alkoxy-, cycloalkoxy-, heterocycloalkoxy-, alkenyloxy-,

cycloalkenyloxy-, heterocycloalkenyloxy-, or alkynyloxy-carbonyl group is substituted

for the hydrogen. Preferred moieties include OH, OCH₂C(O)CH₃,OCH₂C(O)C₂H₅,

OCH₃, OCH₂CH₃, OC(O)CH₃, and OC(O)C₂H₅.

The term "free amino group" means an NH₂. The term "functionally modified amino group" means an NH₂ which has been functionalized to form: an aryloxy-,

heteroaryloxy-, alkoxy-, cycloalkoxy-, heterocycloalkoxy-, alkenyl-, cycloalkenyl-,

heterocycloalkenyl-, alkynyl-, or hydroxy-amino group, wherein the appropriate group is substituted for one of the hydrogens; an aryl-, heteroaryl-, alkyl-, cycloalkyl-,

heterocycloalkyl-, alkenyl-, cycloalkenyl-, heterocycloalkenyl-, or alkynyl-amino

group, wherein the appropriate group is substituted for one or both of the hydrogens;

an amide, in which an acyl group is substituted for one of the hydrogens; a carbamate,

in which an aryloxy-, heteroaryloxy-, alkoxy-, cycloalkoxy-, heterocycloalkoxy-,

alkenyl-, cycloalkenyl-, heterocycloalkenyl-, or alkynyl-carbonyl group is substituted

for one of the hydrogens; or a urea, in which an aminocarbonyl group is substituted

for one of the hydrogens. Combinations of these substitution patterns, for example an

NH₂ in which one of the hydrogens is replaced by an alkyl group and the other

hydrogen is replaced by an alkoxycarbonyl group, also fall under the definition of a functionally modified amino group and are included within the scope of the present

invention. Preferred moieties include NH₂, NHCH₃, NHC₂H₅, N(CH₃)₂,

NHC(O)CH₃, NHOH, and NH(OCH₃).

The term "free thiol group" means an SH. The term "functionally modified

thiol group" means an SH which has been functionalized to form: a thioether, where

an alkyl, aryl, cycloalkyl, heterocycloalkyl, alkenyl, cycloalkenyl, heterocycloalkenyl,

alkynyl, or heteroaryl group is substituted for the hydrogen; or a thioester, in which an

acyl group is substituted for the hydrogen. Preferred moieties include SH, SC(O)CH₃,

SCH₃, SC₂H₅, SCH₂C(O)C₂H₅, and SCH₂C(O)CH₃.

The term "acyl" represents a group that is linked by a carbon atom that has a double bond to an oxygen atom and a single bond to another carbon atom.

The term "alkyl" includes straight or branched chain aliphatic hydrocarbon

groups that are saturated and have 1 to 15 carbon atoms. The alkyl groups may be interrupted by one or more heteroatoms, such as oxygen, nitrogen, or sulfur, and may

be substituted with other groups, such as halogen, hydroxyl, aryl, cycloalkyl, aryloxy,

or alkoxy. Preferred straight or branched alkyl groups include methyl, ethyl, propyl, isopropyl, butyl and t-butyl.

The term "cycloalkyl" includes straight or branched chain, saturated or

unsaturated aliphatic hydrocarbon groups which connect to form one or more rings,

which can be fused or isolated. The rings may be substituted with other groups, such

as halogen, hydroxyl, aryl, aryloxy, alkoxy, or lower alkyl. Preferred cycloalkyl

groups include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

The term "heterocycloalkyl" refers to cycloalkyl rings that contain at least one

heteroatom such as O, S, or N in the ring, and can be fused or isolated. The rings may be substituted with other groups, such as halogen, hydroxyl, aryl, aryloxy, alkoxy, or

lower alkyl. Preferred heterocycloalkyl groups include pyrrolidinyl, tetrahydrofuranyl,

piperazinyl, and tetrahydropyranyl.

The term "alkenyl" includes straight or branched chain hydrocarbon groups

having 1 to 15 carbon atoms with at least one carbon-carbon double bond, the chain

being optionally interrupted by one or more heteroatoms. The chain hydrogens may

be substituted with other groups, such as halogen. Preferred straight or branched

alkenyl groups include, allyl, 1-butenyl, l-methyl-2-propenyl and 4-pentenyl.

The term "cycloalkenyl" includes straight or branched chain, saturated or

unsaturated aliphatic hydrocarbon groups which connect to form one or more non-

aromatic rings containing a carbon-carbon double bond, which can be fused or isolated. The rings may be substituted with other groups, such as halogen, hydroxyl,

alkoxy, or lower alkyl. Preferred cycloalkenyl groups include cyclopentenyl and cyclohexenyl.

The term "heterocycloalkenyl" refers to cycloalkenyl rings which contain one

or more heteroatoms such as O, N, or S in the ring, and can be fused or isolated. The

rings may be substituted with other groups, such as halogen, hydroxyl, aryl, aryloxy,

alkoxy, or lower alkyl. Preferred heterocycloalkenyl groups include pyrrolidinyl,

dihydropyranyl, and dihydrofuranyl.

The term "carbonyl group" represents a carbon atom double bonded to an

oxygen atom, wherein the carbon atom has two free valencies.

The term "aminocarbonyl" represents a free or functionally modified amino

group bonded from its nitrogen atom to the carbon atom of a carbonyl group, the

carbonyl group itself being bonded to another atom through its carbon atom. The term "lower alkyl" represents alkyl groups containing one to six carbons

(C1-C6).

The term "halogen" represents fluoro, chloro, bromo, or iodo.

The term "aryl" refers to carbon-based rings which are aromatic. The rings

may be isolated, such as phenyl, or fused, such as naphthyl. The ring hydrogens may

be substituted with other groups, such as lower alkyl, halogen, free or functionalized

hydroxy, trihalomethyl, etc. Preferred aryl groups include phenyl, 3-

(trifluoromethyl)phenyl, 3-chlorophenyl, and 4-fluorophenyl.

The term "heteroaryl" refers to aromatic hydrocarbon rings which contain at

least one heteroatom such as O, S, or N in the ring. Heteroaryl rings may be isolated, with 5 to 6 ring atoms, or fused, with 8 to 10 atoms. The heteroaryl ring(s) hydrogens

or heteroatoms with open valency may be substituted with other groups, such as lower

alkyl or halogen. Examples of heteroaryl groups include imidazole, pyridine, indole, quinoline, furan, thiophene, pyrrole, tetrahydroquinoline, dihydrobenzofuran, and

dihydrobenzindole.

The terms "aryloxy", "heteroaryloxy", "alkoxy", "cycloalkoxy",

"heterocycloalkoxy", "alkenyloxy", "cycloalkenyloxy", "heterocycloalkenyloxy", and

"alkynyloxy" represent an aryl, heteroaryl, alkyl, cycloalkyl, heterocycloalkyl, alkenyl,

cycloalkenyl, heterocycloalkenyl, or alkynyl group, respectively, attached through an

oxygen linkage.

The terms "alkoxycarbonyl", "aryloxycarbonyl", "heteroaryloxycarbonyl",

"cycloalkoxycarbonyl", "heterocycloalkoxycarbonyl", "alkenyloxycarbonyl",

"cycloalkenyloxycarbonyl", "heterocycloalkenyloxycarbonyl", and

"alkynyloxycarbonyl" represent an alkoxy, aryloxy, heteroaryloxy, cycloalkoxy, heterocycloalkoxy, alkenyloxy, cycloalkenyloxy, heterocycloalkenyloxy, or

alkynyloxy group, respectively, bonded from its oxygen atom to the carbon of a

carbonyl group, the carbonyl group itself being bonded to another atom through its

carbon atom.

Preferred compounds of the present invention include those of formula I, wherein:

R¹ is CO₂R, wherein R is H or CO R forms an ophthalmically acceptable salt or an ophthalmically acceptable ester;

n is 0;

A, B, C and D are the same or different and are CH=CH or C≡C;

Y is

and

X is CH₂, CH(CH₃) or C(CH₃) ₂, or

Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

with the proviso that Y cannot be CH₂ when X is

or Among the particularly preferred compounds of formula (I) are compounds 2-

5, whose preparations are detailed in the following examples 1-4:

2 3

(5Z,8Z,11Z,13E)-(16/?S)-16-hydroxy-16-methyl (5Z,8Z,11Z,13£)-(15RS)-16,16-dimethyl-15-hydroxy- eicosa-5,8,11 ,13-tetraenoic acid eicosa-5,8,11 ,13-tetraenoic acid

(5Z,11Z,13£)-(16 ?S)-16-hydroxy-16-methyl- (5Z,11Z,13£)-(15RS)-16,16-dimethyl-15-hydroxy- eicosa-5,11 ,13-trienoic acid eicosa-5,11 ,13-trienoic acid

Example 1

Synthesis of 2

(5Z.8Z.1 lZ,13E)-(16RS)-16-Hvdroxy-16-methyleicosa-5.8.11,13-tetraenoic acid (2)

Treatment of propargyl alcohol 6 (prepared according to the method of

Takahashi, O. et. al. Tetrahedron Lett. 1989, 30, 1583-1584) with «-Bu₃SnH and

AIBN, followed by treatment with I₂ affords the vinyl iodide 7. Palladium-catalyzed

cross-coupling of vinyl iodide 7 and alkyne 8 (prepared according to the method of

Nicolaou, K. C. et. al. J. Chem. Soc, Chem. Commun. 1985, 1580-1581) followed by

reduction with H₂ and Pd/C /BaSO₄ gives the tetraene 9. Treatment of tetraene 9 with

LiOH in THF/H₂0 gives the title compound 2. Example 2

Synthesis of 3

(5Z,8Z,1 lZ,13E)-(15RS)-16,16-Dimethyl-15-hvdroxyeicosa-5,8,l 1.13-tetraenoic acid ω

Alkylation of methyl isobutyrate 10 followed by reduction with DIBAL gives

the aldehyde 11. Treatment of the aldehyde 11 with lithium acetylide affords the

propargyl alcohol 12. The vinyl iodide 13 is prepared in two steps from n-

Bu₃SnH/AIBN and I₂. Palladium-catalyzed cross-coupling of vinyl iodide 13 and

ester 8, followed by reduction gives the tetraene 14. Saponification of tetraene 14

with LiOH gives the title compound 3. Example 3

Synthesis of 4

3. I₂, morphoiine

15 16

17

n-Bu₃S

17

Wittig

(5Z.1 lZ,13E)-(16RS)-16-Hvdroxy-16-methyl-eicosa-5,l 1,13-trienoic acid (4)

Sequential treatment of 1-hexyne 15 with n-BuLi and paraformaldehyde

affords the propargyl alcohol (not shown). Alkyne isomerization with KH/1,3-

diaminopropane and subsequent conversion to the corresponding iodoalkyne 16 is

accomplished with I₂/morpholine. Selective reduction with gives the vinyl iodide 17.

Treatment of propargyl alcohol 6 (prepared according to the method of Takahashi, O.

et. al. Tetrahedron Lett. 1989, 30, 1583-1584) with «-Bu₃SnH and AIBN affords the

vinyl stannane 18. Stille coupling of vinyl iodide 17 and vinyl stannane 18, followed

by Jones oxidation gives aldehyde 19. Treatment of aldehyde 19 with the appropriate

Wittig reagent gives the title compound 4.

Example 4 Synthesis of 5

17

(5Z.1 lZ,13E)-(15i.S)-16.16-Dimethyl-15-hydroxyeicosa-5,l 1,13-trienoic acid

(5)

Alkylation of methyl isobutyrate 10 with 1-iodobutane, followed by

DIBAL reduction affords the aldehyde 11. Treatment of aldehyde 11 with lithium

acetylide gives the propargyl alcohol 12. Sequential treatment of 1-hexyne 15 with n-

BuLi and paraformaldehyde affords the propargyl alcohol (not shown). Alkyne

isomerization with KH/l,3-diaminopropane and subsequent conversion to the

corresponding iodoalkyne 16 is accomplished with I₂/morpholine. Selective reduction

with gives the cis- vinyl iodide 17. Sonagashira coupling of cts-vinyl iodide 17 with

propargyl alcohol 12, reduction with LiAlH , followed by selective oxidation gives

aldehyde 20. Wittig olefination of aldehyde 20 affords the HΕTΕ analog 5.

Salt forms of the formula (I) compounds are preferred as it is believed that the

neat salts are more stable than the corresponding neat acids. Preferred salts of the

present invention are those wherein a terminal carboxylate of formula (I) (i.e., wherein R¹ is CO₂R) forms a salt with cations selected from: Na⁺, K⁺, NH ⁺,

benzyltrimethylammonium ion, tetrabutylammonium ion, and phenyltrimethyl

ammonium ion.

As used hereinafter, the term "compounds of formula (I)," refers to

compounds of formula (I), and/or the phospholipid-formula (I) esters or amides

described above. The compositions of the present invention comprise one or more

compounds of formula (I) and a pharmaceutically acceptable carrier. The

compositions are formulated in accordance with methods known in the art for the

particular route of administration desired for the prevention, treatment or amelioration

of the particular disease or disorder targeted. The level of peroxy compounds in the HETE derivative raw materials that are used to prepare the pharmaceutical

formulations of the present invention may have an impact on the HETE derivative's

biological activity. Although the precise relationship has not been defined, it is

preferable to use HETE derivative raw material supplies containing peroxy

compounds at levels no greater than about 0.3 ppm. Methods for determining peroxy

levels are known in the art (e.g., European Pharmacopoeia 1997 3^rd Ed., Method 2.5.5 - Peroxide Value).

As used herein, the term "pharmaceutically acceptable carrier" refers to any

formulation which is safe, and provides the appropriate delivery of an effective amount

of one or more compounds of formula (I) for the prevention, treatment or amelioration of the disease or disorder targeted.

As used herein, the term "pharmaceutically effective amount" refers to an

amount of one or more compounds of formula (I) that, when administered to a patient, prevents, treats or ameliorates a disease or disorder, or conditions associated thereof. As used herein, "an ophthalmically effective amount" refers to an amount of one or

more compounds of formula (I) that, when administered to a patient, prevents, treats

or ameliorates an ophthalmic disease or disorder, or conditions associated thereof.

For the treatment of dry eye, such an effective amount will stimulate secretion of

mucin in the eye and thus eliminate or improve dry eye conditions when administered

to the eye. As used herein, "an effective amount to treat dry eye" refers to an amount

of one or more compounds of formula (I) that, when administered to a patient,

prevents, treats or ameliorates a dry eye disease or disorder, or conditions associated

thereof. Generally, the compounds of formula (I) will be contained in a composition

of the present invention in a concentration range of about 0.00001 to 10 per cent weight/volume ("% w/v"). Preferred ophthalmic, including dry eye-treatment,

compositions will contain one or more compounds of formula (I) in a concentration of

from about 0.00001-0.01% w/v.

The present invention is particularly directed to compositions useful in treating

dry eye. Preferably, such compositions will be formulated as solutions, suspensions

and other dosage forms for topical administration. Aqueous solutions are generally

preferred, based on ease of formulation, biological compatibility (especially in view of

the malady to be treated, e.g., dry eye-type diseases and disorders), as well as a

patient's ability to easily administer such compositions by means of instilling one to

two drops of the solutions in the affected eyes. However, the compositions may also

be 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

less soluble in water.

Preferably, the ophthalmic compositions of the present invention will also contain ethanol. As used herein, "an effective concentration of ethanol" refers to a

concentration that enhances the biological efficacy of the formula (I) compositions in

vivo. In general, the concentration of ethanol necessary for the enhancement of the

compounds of formula (I) is believed to be somewhat proportional to the

concentration of the formula (I) compound(s) administered. If a relatively high

concentration of formula (I) compound(s), e.g., above 0.01% w/v, is administered, the

concentration of ethanol in such compositions may be proportionally less than

analogous compositions containing lower concentrations of formula (I) compounds.

In general, however, the ethanol concentration contained in the ophthalmic

compositions of the present invention will range from about 0.001-2% w/v. Compositions containing formula (I) concentrations of about 0.00001-0.02% w/v

preferably will contain ethanol in a concentration of about 0.005-0.2% w/v, and most

preferably, about 0.02-0.10% w/v.

Preferably, the compositions of the present invention will also contain a

surfactant. Various surfactants useful in topical ophthalmic formulations may be

employed. The surfactant(s) may provide additional chemical stabilization of the

formula (I) compounds and may further provide for the physical stability of the

compounds. In other words, the surfactants may aid in preventing chemical

degradation of the compounds of formula (I) and also prevent the compounds from

binding to the containers in which their compositions are packaged. As used herein,

"an effective concentration of surfactant(s)" refers to a concentration that enhances the chemical and physical stability of formula (I) compound(s). Examples of surfactants

include, but are not limited to: Cremophor^® EL, polyoxyl 20 ceto stearyl ether,

polyoxyl 40 hydrogenated castor oil, polyoxyl 23 lauryl ether and poloxamer 407 may be used in the compositions. A preferred surfactant is polyoxyl 40 stearate. The

concentration of surfactant will vary, depending on the concentration of formula (I)

compound(s) and optional ethanol present in the formulation. In general, however, the surfactant(s) concentration will be about 0.001 to 2.0% w/v. Preferred

compositions of the present invention will contain about 0.1% w/v of polyoxyl 40

stearate.

The compositions of the present invention may also include various other

ingredients, such as tonicity agents, buffers, preservatives, co-solvents and viscosity

building agents. Various tonicity agents may be employed to adjust the tonicity of the

composition, preferably to that of natural tears for ophthalmic compositions. For

example, sodium chloride, potassium chloride, magnesium chloride, calcium chloride,

dextrose and or mannitol may be added to the composition to approximate

physiological tonicity. Such an amount of tonicity agent will vary, depending on the

particular agent to be added. In general, however, the compositions will have a

tonicity agent concentration of about 0.1-1.5% w/v. Sodium chloride in the amount of

0.75% w/v is preferred.

An appropriate buffer system (e.g., sodium phosphate, sodium acetate, sodium

citrate, sodium borate or boric acid) may be added to the compositions to prevent pH drift under storage conditions. The particular concentration will vary, depending on

the agent employed. In general, however, such a concentration will range from about

0.02 to 2.0% w/v. Preferred compositions will contain about 0.25% w/v of boric acid.

Antioxidants may be added to compositions of the present invention to protect

the formula (I) compounds from oxidation during storage. Examples of such

antioxidants include, but are not limited to, vitamin E and analogs thereof, ascorbic

acid and derivatives, and butylated hydroxyanisole (BHA).

Compositions formulated for the treatment of dry eye-type diseases and

disorders may also comprise aqueous carriers designed to provide immediate, short-

term relief of dry eye-type conditions. Such carriers can be formulated as a

phospholipid carrier or an artificial tears carrier, or mixtures of both. As used in this

paragraph and the immediately succeeding paragraph, the term "phospholipid" refers

only to the phospholipids of the phospholipid carrier, does not refer to a compound of

formula (I) and, as such, does not contain a formula (I) compound. As used herein, "phospholipid carrier" and "artificial tears carrier" refer to aqueous compositions

which: (i) comprise one or more phospholipids (in the case of phospholipid carriers)

or other compounds, which lubricate, "wet," approximate the consistency of

endogenous tears, aid in natural tear build-up, or otherwise provide temporary relief of

dry eye symptoms and conditions upon ocular administration; (ii) are safe; and (iii)

provide the appropriate delivery vehicle for the topical administration of an effective

amount of one or more compounds of formula (I). Examples or artificial tears

compositions useful as artificial tears carriers include, but are not limited to, commercial

products, such as Tears Naturale®, Tears Naturale II®, Tears Naturale Free®, and Bion

Tears® (Alcon Laboratories, Inc., Fort Worth, Texas). Examples of phospholipid carrier formulations include those disclosed in U.S. Patent Nos. 4,804,539 (Guo et al.),

4,883,658 (Holly), 4,914,088 (Glonek), 5,075,104 (Gressel et al.), 5,278,151 (Korb et

al.), 5,294,607 (Glonek et al.), 5,371,108 (Korb et al), 5,578,586 (Glonek et al.); the foregoing patents are incorporated herein by reference to the extent they disclose

phospholipid compositions useful as phospholipid carriers of the present invention.

The phospholipids useful in the phospholipid carriers are any natural or

synthetic phospholipid compound comprising a glycerol-phosphoric acid ester or

sphingomyelin backbone. Examples of phospholipids useful in the present invention

include those of formula (II):

(II) wherein, X²¹ and X²² are the same or different and are O, NH(C=O), O(C=O), or a direct bond;

R²² is H or CH=CH(CH₂),₂CH₃;

X²¹-R^! is OH, or R¹ is Cι_2-26 substituted or unsubstituted alkyl or alkenyl;

R² is Cι_2-26 substituted or unsubstituted alkyl or alkenyl; and

R³ is H, OH, OCH₂CH(NH₃ ⁺)COO\ OCH₂CH₂NH₃ ⁺, OCH₂CH₂N⁺(CH₃)₃,

OCH₂CH(OH)CH₂OH and O-inositol.

The phospholipids may be present as racemic or non-racemic compounds. Preferred phospholipids are those wherein X -R and or X -R comprise fatty acid esters or

amides. Natural fatty acids are saturated, monounsaturated or polyunsaturated.

Examples of fatty acid residues include, but are not limited to, laurate, myristate,

palmitate, palmitoleate, stearate, oleate, linoleate, linolenate, eicosanoate, docosanoate

and lignocerate. Preferred phospholipid types are the phosphatidylethanolamines,

phosphatidylcholines, phosphatidylserines, phospatidylinositols and sphingomyelins.

Examples of specific phospholipids include: 1,2-dipalmitoyl phosphatidyl choline

("DPPC") 1,2-dipalmityl phosphatidyl glycerol ("DPPG"), N-stearyl sphingomyelin,

N-palmityl sphingomyelin, N-oleyl sphingomyelin, 1,2-distearoyl phosphatidyl

ethanolamine ("DSPE"), 1,2-distearoyl phosphatidyl inositol ("DSPI"), l-stearoyl-2-

palmitoyl phosphatidyl ethanolamine ("SPPE"), l-stearoyl-2 -palmitoyl phosphatidyl

choline ("SPPC"), 1,2-dipalmitoyl phosphatidyl ethanolamine ("DPPE"), 1,2-dioleoyl phophatidyl ethanolamine ("DOPE"), 1,2-dioleoyl phophatidyl serine ("DOPS"), and

1,2-dipalmitoyl phosphatidyl serine ("DPPS"). The most preferred phospholipid

carriers are the phosphatidylethanolamines and sphingomyelins. Phospholipids are

available from a variety of natural sources and may be synthesized by methods known

in the art; see, for example, Tsai et al., Biochemistry, volume 27, page 4619 (1988);

and Dennis et. al., Biochemistry, volume 32, page 10185 (1993).

Other compounds designed to lubricate, "wet," approximate the consistency of

endogenous tears, aid in natural tear build-up, or otherwise provide temporary relief of

dry eye symptoms and conditions upon ocular administration the eye are known in the

art. Such compounds may enhance the viscosity of the composition, and include, but

are not limited to: monomeric polyols, such as, glycerol, propylene glycol, ethylene glycol; polymeric polyols, such as, polyethylene glycol, hydroxypropylmethyl

cellulose ("HPMC"), carboxy methylcellulose sodium, hydroxy propylcellulose

("HPC"), dextrans, such as, dextran 70; water soluble proteins, such as gelatin; and vinyl polymers, such as, polyvinyl alcohol, polyvinylpyrrolidone, povidone and

carbomers, such as, carbomer 934P, carbomer 941, carbomer 940, carbomer 974P.

Other compounds may also be added to the ophthalmic compositions of the

present invention to increase the viscosity of the carrier. Examples of viscosity

enhancing agents include, but are not limited to: polysaccharides, such as hyaluronic

acid and its salts, chondroitin sulfate and its salts, dextrans, various polymers of the

cellulose family; vinyl polymers; and acrylic acid polymers. In general, the

phospholipid carrier or artificial tears carrier compositions will exhibit a viscosity of 1

to 400 centipoises ("cps"). Preferred compositions containing artificial tears or

phospholipid carriers will exhibit a viscosity of about 25 cps. Topical ophthalmic products are typically packaged in multidose form.

Preservatives are thus required to prevent microbial contamination during use.

Suitable preservatives include: benzalkonium chloride, chlorobutanol,

benzododecinium bromide, methyl paraben, propyl paraben, phenylethyl alcohol,

edetate disodium, sorbic acid, polyquaternium-1, 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% w/v. Unit dose compositions of the present invention will be sterile, but

typically unpreserved. Such compositions, therefore, generally will not contain

preservatives.

The preferred compositions of the present invention are intended for

administration to a human patient suffering from dry eye or symptoms of dry eye. Preferably, such compositions will be administered topically. In general, the doses

used for the above described purposes will vary, but will be in an effective amount to

increase mucin production in the eye and thus eliminate or improve dry eye

conditions. Generally, 1-2 drops of such compositions will be administered 1-10

times per day for the treatment of dry eye or other ocular disease or disorder.

Preferably, 1-2 drops of the compositions will be administered 1-4 times per day.

The present invention is also directed to stable, stock compositions comprising

one or more compounds of formula (I) and ethanol. The inventors believe that storing

the compounds of formula (I) in an ethanolic solution provides greater stability of the

compounds of formula (I) over analogous aqueous compositions, or neat compounds

of formula (I) compositions. Such compositions comprise one or more compounds of

formula (I) and an amount of ethanol to solubilize the compounds of formula (I) in

solution. Preferably, the ethanolic stock solutions will contain anhydrous ethanol, but aqueous ethanolic solutions are also contemplated by the present invention.

Generally, the stock solutions will contain ethanol in a concentration of about 25 to

100 % volume/volume ("v/v"). Typically, such stock solutions will contain

compounds of formula (I) in high concentration relative to the pharmaceutical

compositions of the present invention.

The following Examples 1-5 describe preferred compositions of the present

invention. The actual pH of the compositions may vary (e.g., between 6-8), and the

concentrations of the various ingredients included in the exemplified compositions

may vary, but are included in the compositions in the approximate amounts shown.

Example 1

The above composition is prepared by the following method. The batch quantities of polyoxyl 40 stearate, boric acid, sodium chloride, disodium edetate, and

polyquaternium-1 are weighed and dissolved by stirring in 90% of the batch quantity

of purified water. The pH is adjusted to 7.5 ± 0.1 with NaOH and/or HCl. Under

yellow light or reduced lighting, the batch quantity of Compound 1 as a stock solution

in ethanol and the additional quantity of ethanol necessary for the batch are measured

and added. Purified water is added to q.s. to 100%. The mixture is stirred for five

minutes to homogenize and then filtered through a sterilizing filter membrane into a

sterile recipient.

Preferably, the above process is performed using glass, plastic or other non-

metallic containers or containers lined with such materials. Example 2

The above formulation may be made by a method similar to the method described in

Example 1.

Example 3

The above formulation may be made by a method similar to the method described in

Example 1. Example 4

The following is an example of an artificial tears carrier-composition of the present

invention:

The above formulation may be made by a method similar to the method described in

Example 1.

Example 5

The following is an example of a phospholipid carrier-composition of the present invention:

The above formulation may be made by a method similar to the method described in

Example 1.

The invention in its broader aspects is not limited to the specific details shown

and described above. Departures may be made from such details within the scope of the

accompanying claims without departing from the principles of the invention and without

sacrificing its advantages.

Claims

WHAT IS CLAIMED IS:

1. A composition for the treatment of dry eye and other disorders requiring the

wetting of the eye comprising a pharmaceutically acceptable carrier and a

pharmaceutically effective amount of one or more compounds of the following

formula I:

wherein:

R¹ is (CH₂)_nCO₂R, (CH₂)_nCONR²R³, (CH₂)_nCH₂OR⁴, (CH₂)_nCH₂NR⁵R⁶, (CH₂)_nCH₂N₃, (CH₂)_nCH₂Hal, (CH₂)_nCH₂NO₂, (CH₂)_nCH₂SR²⁰, (CH₂)_nCOSR²¹ or (CH₂)_n-2,3,4,5-tetrazol-l-yl, wherein:

R is H or CO R forms a pharmaceutically acceptable salt or a pharmaceutically acceptable ester;

NR R³ and NR⁵R⁶ are the same or different and comprise a free or functionally modified amino group;

OR⁴ comprises a free or functionally modified hydroxy group;

Hal is F, CL Br or l;

SR²⁰ comprises a free or functionally modified thiol group;

R²¹ is H or COSR²¹ forms a pharmaceutically acceptable salt or a pharmaceutically acceptable thioester;

n is 0 or 2;

A, B, C and D is Cι-C alkyl, alkenyl, or alkynyl or a C -C₅ allenyl group;

Y is

wherein R is H or CH₃, and

X is CH₂, CH(CH₃) or C(CH₃)₂; or Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

wherein R is H or CH₃, with the proviso that Y cannot be CH₂ when X is

or

; and

R O comprises a free or functionally modified hydroxy group.

2. The composition of Claim 1, wherein for the compound of formula I:

R¹ is CO₂R, wherein R is H or CO₂R forms an ophthalmically acceptable salt or an ophthalmically acceptable ester; n is O;

A, B, C and D are the same or different and are CH=CH or C≡C;

Y is

or and

X is CH₂, CH(CH₃) or C(CH₃) ₂, or

Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

with the proviso that Y cannot be CH₂ when X is

3. The composition of Claim 2, wherein the compound of formula (I) is selected

from the group consisting of:

; and

4. The composition of Claim 1, wherein the composition is a topical ophthalmic

formulation.

5. A method for the treatment of dry eye and other disorders requiring the wetting of the eye which comprises administering to a mammal a composition comprising a

pharmaceutically acceptable carrier and a pharmaceutically effective amount of one or

more compounds of the following formula I:

wherein:

R¹ is (CH₂)_nCO₂R, (CH₂)_nCONR²R³, (CH₂)_nCH₂OR⁴, (CH₂)_nCH₂NR⁵R° ( (CCHH₂₂))_nnCCHH₂₂NN₃₃,, ((CCHH₂₂))_nnCCHH₂₂HHaall,, ((CCHH₂₂)_nCH₂NO₂, (CH₂)_nCH₂SR²⁰, (CH₂)_nCOSR²¹ or (CH₂)_n-2,3,4,5-tetrazol-l-yl, wherein:

R is H or CO₂R forms a pharmaceutically acceptable salt or a pharmaceutically acceptable ester;

NR²R³ and NR⁵R⁶ are the same or different and comprise a free or functionally modified amino group;

OR⁴ comprises a free or functionally modified hydroxy group;

Hal is F, Cl, Br or I; f)

SR comprises a free or functionally modified thiol group;

R²¹ is H or COSR²¹ forms a pharmaceutically acceptable salt or a pharmaceutically acceptable thioester;

n is 0 or 2;

A, B, C and D is Cι-C₅ alkyl, alkenyl, or alkynyl or a C -C₅ allenyl group;

Y is

or wherein R is H or CH₃, and

X is CH₂, CH(CH₃) or C(CH₃)₂; or

Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

or wherein R⁸ is H or CH , with the proviso that Y cannot be CH when X is

and

R⁷O comprises a free or functionally modified hydroxy group.

6. The method of Claim 5, wherein for the compound of formula I:

R¹ is CO₂R, wherein R is H or CO R forms an ophthalmically acceptable salt or an ophthalmically acceptable ester;

n is 0;

A, B, C and D are the same or different and are CH=CH or C≡C; Y is

and

X is CH₂, CH(CH₃) or C(CH₃)₂, or

Y is CH , CH(CH₃) or C(CH₃)₂, and X is

or with the proviso that Y cannot be CH₂ when X is

or

7. The method of Claim 5, wherein the compound of formula (I) is selected from

the group consisting of:

and

8. The method of Claim 5, wherein the composition is a topical ophthalmic

formulation.

9. The method of Claim 5 wherein the dry eye and other disorders requiring the

wetting of the eye is symptoms of dry eye associated with refractive surgery.

10. A compound according to formula (I):

I wherein:

R¹ is (CH₂)_nCO₂R, (CH₂)_nCONR²R³, (CH₂)_nCH₂OR\ (CH₂)_nCH₂NR^JR° ( (CCHH₂₂))_nnCCHH₂₂NN₃₃,, ((CCHH₂₂))_nnCCHH₂₂HHaall,, ((CCHH₂₂)_nCH₂NO₂, (CH₂)_nCH₂SR²⁰, (CH₂)_nCOSR²¹ or (CH₂)_n-2,3,4,5-tetrazol-l-yl, wherein:

R is H or CO₂R forms a pharmaceutically acceptable salt or a pharmaceutically acceptable ester;

NR²R³ and NR⁵R⁶ are the same or different and comprise a free or functionally modified amino group;

OR⁴ comprises a free or functionally modified hydroxy group;

Hal is F, Cl, Br or I;

SR comprises a free or functionally modified thiol group;

R²¹ is H or COSR²¹ forms a pharmaceutically acceptable salt or a pharmaceutically acceptable thioester;

n is 0 or 2;

A, B, C and D is C₁-C₅ alkyl, alkenyl, or alkynyl or a C₃-C₅ allenyl group;

Y is

tfc ^'Rβ or wherein R is H or CH₃, and

X is CH₂, CH(CH₃) or C(CH₃)₂; or Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

wherein R is H or CH , with the proviso that Y cannot be CH₂ when X is

and

R⁷O comprises a free or functionally modified hydroxy group.

11. The compound of Claim 10, wherein for the compound of formula I:

R¹ is CO₂R, wherein R is H or CO₂R forms an ophthalmically acceptable salt or an ophthalmically acceptable ester;

n is 0;

A, B, C and D are the same or different and are CH=CH or C≡C;

Y is

or and

X is CH₂, CH(CH₃) or C(CH₃)₂, or

Y is CH₂, CH(CH₃) or C(CH₃)₂, and X is

with the proviso that Y cannot be CH when X is

12. The compound of Claim 10, wherein the compound is selected from the group

consisting of:

and