3-substituted thieno[2,3-b][1,4]thiazine-6-sulfonamides. A novel class of topically active carbonic anhydrase inhibitors.

3-Aminoalkyl derivatives of thieno[2,3-b][1,4]thiazine-6-sulfonamide were prepared for evaluation as topically active ocular hypotensive agents. The compounds described were found to be excellent in vitro inhibitors of carbonic anhydrase II and in vivo to lower intraocular pressure in three rabbit models of ocular hypertension. Compounds 20A, 20B, and 20C met the requirement of formulation as a 1% solution at pH 5.2, but none of the compounds described exhibited greater activity in the normotensive albino rabbit, the alpha-chymotrypsin-treated albino rabbit, or the normotensive pigmented rabbit than MK-927 or MK-507, the present clinical candidates.

Sulfonylmethanesulfonamide inhibitors of carbonic anhydrase.

A series of sulfonylmethanesulfonamide derivatives is described, which are inhibitors of carbonic anhydrase (CA). The most potent of these is the racemic fluoro sulfone 9, which inhibits carbon dioxide hydration catalyzed by human CA II (CA-II) with an IC50 of 3 nM. Binding competition studies versus dansylamide indicate that the enantiomers of 9 have different affinities for CA-II, with equilibrium dissociation constants of 3.6 and 0.6 nM. QSAR analysis suggests that the key factors involved in achieving high affinity in this series are sulfonamide acidity, hydrophobicity, and minimization of steric demands at the carbon atom adjacent to the sulfonamide group.

4-substituted thiophene- and furan-2-sulfonamides as topical carbonic anhydrase inhibitors.

A series of 4-substituted thiophene- and furan-2-sulfonamides was prepared and was found to possess nanomolar-level potency for inhibition of human carbonic anhydrase II in vitro. Selected examples from this group were further evaluated for their potential to act as topically effective ocular hypotensive agents in the ocular normotensive albino rabbit and the ocular alpha-chymotrypsinized rabbit. Solubility studies in water and pH 7.4 buffer were carried out to estimate the ability of compounds to be formulated in solution. The sensitization potential of key representative structures was determined by in vitro glutathione reactivity studies and guinea pig maximization testing.

Thieno[2,3-b]furan-2-sulfonamides as topical carbonic anhydrase inhibitors.

Novel 5-[(alkylamino)methyl]thieno[2,3-b]furan-2-sulfonamides were prepared and evaluated in vitro for inhibition of human carbonic anhydrase II (CA II) and ex vivo for their ability to inhibit Ca II in the albino rabbit eye after topical administration. Compound 11a was found to lower intraocular pressure (IOP) in both the alpha-CT ocular hypertensive albino rabbit and the normal albino rabbit, but was ineffective at lowering IOP in a hypertensive, pigmented monkey model. Since 11a was highly bound to ocular pigment, a series of less basic analogs was prepared. Examples in this series were both less extensively bound to ocular pigment and more active at reducing IOP in pigmented rabbits after topical dosing. Key examples displayed moderate reactivity toward glutathione.

Topically active carbonic anhydrase inhibitors. 4. [(Hydroxyalkyl)sulfonyl]benzene and [(hydroxyalkyl)sulfonyl]thiophenesulfonamides.

For several decades a tantalizing goal for the treatment of primary open-angle glaucoma has been the development of a topically active carbonic anhydrase inhibitor. Recent results from several research groups indicate that considerable progress has been made toward this objective. In this report, we present the design and synthesis of (hydroxyalkyl)sulfonyl-substituted benzene- and thiophenesulfonamides. These compounds exhibit inhibition of carbonic anhydrase II in the nanomolar range and lower intraocular pressure in the alpha-chymotrypsinized rabbit model of ocular hypertension after topical instillation.

New isomeric classes of topically active ocular hypotensive carbonic anhydrase inhibitors: 5-substituted thieno[2,3-b]thiophene-2-sulfonamides and 5-substituted thieno[3,2-b]thiophene-2-sulfonamides.

A series of 5-substituted thieno[2,3-b]- and thieno[3,2-b)- and thieno[3,2-b)thiophene-2-sulfonamides was prepared and evaluated for topical ocular hypotensive activity in glaucoma models. The 5-substituents were varied to maximize both inhibitory potency against carbonic anhydrase and water solubility. At the same time, these substituents were varied in order to obtain compounds with the appropriate pKa to minimize pigment binding in the iris. All of these variables were optimized in the best compound, 5-[[(methoxyethyl)[(methoxyethyl)ethyl] amino]methyl]thieno[2,3-b]thiophene-2-sulfonamide hydrochloride (55).

A comparison of L-671,152 and MK-927, two topically effective ocular hypotensive carbonic anhydrase inhibitors, in experimental animals.

L-671,152 is a water-soluble, carbonic anhydrase inhibitor structurally similar to MK-927, a carbonic anhydrase inhibitor that, on topical administration, lowers the intraocular pressure (IOP) of experimental animals and humans. L-671,152 was more potent than MK-927 at inhibiting purified, human erythrocyte carbonic anhydrase II in vitro, as reflected in their respective IC50 values of 0.16 nM and 1.19 nM. Both compounds were compared for topical, ocular hypotensive activity in pigmented rabbits and cynomolgus monkeys. Ocular hypertension was induced in the latter by argon laser photocoagulation of the trabecular meshwork. A 2% solution of L-671,152 was more potent than 2% MK-927 in lowering the IOP of ocular hypertensive monkeys, the maximum reductions being 13.8 mm Hg (37%) and 9.6 mm Hg (27%) at 5 hr and 4 hr, respectively. Moreover, the duration of action of L-671,152 was superior to that of MK-927. The ocular hypotensive effect of L-671,152 was greater than that of MK-927 over a range of concentrations (0.5%-2%) in pigmented rabbits whose IOP was inherently elevated. The peak declines in the IOP of these rabbits after the instillation of 2% solutions of L-671,152 and MK-927 were 6.1 mm Hg and 4.8 mm Hg, respectively. L-671,152 was very effective in lowering the elevated IOP of alpha-chymotrypsinized rabbits and the unilateral instillation of 0.5% L-671,152 into the contralateral eye failed to decrease the elevated IOP of the alpha-chymotrypsinized eye. This finding indicates that the site of action of topically applied L-671,152 is local. The enhancement in the potency of L-671,152 over MK-927 is attributed to a greater inhibition of carbonic anhydrase activity.

Topically active carbonic anhydrase inhibitors. 3. Benzofuran- and indole-2-sulfonamides.

Derivatives of benzofuran- and indole-2-sulfonamide were prepared for evaluation as topically active ocular hypotensive agents. These compounds were found to be excellent inhibitors of carbonic anhydrase and to lower intraocular pressure in a rabbit model of ocular hypertension. However, the development of these compounds for clinical use was precluded by the observation that they cause dermal sensitization in guinea pigs. A correlation between electrophilicity, as assessed by in vitro reactivity with reduced glutathione, and dermal sensitization potential was further documented.

L-662,583 is a topically effective ocular hypotensive carbonic anhydrase inhibitor in experimental animals.

1. L-662,583 was a potent inhibitor in vitro of purified, human erythrocyte carbonic anhydrase II, possessing an IC50 of 0.7 nM. The IC50 values for MK-927, acetazolamide and methazolamide were 13.0 nM, 10.8 nM and 21.2 nM, respectively. 2. A 1 h pretreatment with one 50 microliters drop of a 0.1% solution of L-662,583 blocked carbonic anhydrase activity in a homogenate of the iris + ciliary body of albino rabbits by 63%. Similar treatment with 0.1% suspensions of acetazolamide and methazolamide elicited inhibitions of 30% and 20%, respectively. This ex vivo model indirectly assesses the ability of an agent to enter the rabbit eye. 3. Concentrations of L-662,583 in the cornea, aqueous humour and iris + ciliary body of albino rabbits were determined by h.p.l.c. at predetermined times after the instillation (one drop of 50 microliters) of a 2% solution of L-662,583. Peak levels for cornea (47.4 micrograms g-1), aqueous humour (4.51 micrograms ml-1) and iris + ciliary body (9.61 micrograms g-1) occurred at 0.5, 2 and 1 h after instillation, respectively. 4. The experimentally elevated intraocular pressure of the right eye of rabbits, induced by prior intraocular injection of alpha-chymotrypsin, was maximally decreased by 4.5 mmHg, 6.2 mmHg and 9.8 mmHg after the instillation (one drop of 50 microliters) of 0.01%, 0.1% and 0.5% solutions of L-662,583, respectively. All three concentrations lowered intraocular pressure at all time points from 1 h up to and including 5 h, the last recorded time point. The unilateral instillation of L-662,583 (0.5%) into the contralateral, left eye failed to lower the elevated intraocular pressure of the untreated, right eye. This finding indicates that the site of action of topically applied L-662,583 in this paradigm is local. The ocular normotensive, albino rabbit was much less susceptible than the ocular hypertensive rabbit to the intraocular pressure lowering effect of topically applied L-662,583, with a 2% solution maximally decreasing intraocular pressure by 2.3 mmHg. 5. Unilateral ocular hypertension was elicited in the right eye of sedated, cynomolgus monkeys by argon laser-induced photocoagulation of the trabecular meshwork. The instillation (one drop of 50 microL) of L-662, 583 (2%) significantly lowered the elevated intraocular pressure of the right eye at all time points from 1 h up to and including 5 h. The maximum decline was 8.3 mmHg at 3 h and this represented a reduction of 23% from the corresponding baseline value of 36.8 mmHg. The intraocular pressure of the hypertensive, right eye was maximally decreased by 4.1 mmHg and 4.8 mmHg after the instillation of 0.5% and 1% solutions of L-662,583, respectively. Like the rabbit, the normotensive eye of cynomolgus monkeys was more resistant than the hypertensive eye to the ocular hypotensive action of L-662, 583, as indicated by the inability of 0.5% and 1% solutions of the agent to lower intraocular pressure. L-662,583 (2%) maximally reduced the intraocular pressure of normotensive monkey eyes by 2.4 mmHg at 2 h. 6. L-662,583 is structurally different from MK-927, a carbonic anhydrase inhibitor that lowers the intraocular pressure of glaucoma patients following the instillation of a 2% solution. These preclinical observations indicate that L-662,583, like MK-927, is a water-soluble carbonic anhydrase inhibitor which, on topical administration, lowers intraocular pressure by virtue of an action confined to within the eye.

MK-927: a topically active ocular hypotensive carbonic anhydrase inhibitor.

MK-927 (dl-5,6-dihydro-4-(2-methylpropylamino)-4H-thieno(2,3b)thiopyra n-2-sulfonamide-7,7-dioxide hydrochloride) is a water soluble, carbonic anhydrase inhibitor (CAI) possessing a Ki of 12.0 nM against purified human carbonic anhydrase II in vitro. The acute instillation of one drop (50 microliters) of 0.5%, 1% and 2% solutions of MK-927 maximally decreased the intraocular pressure (IOP) of ocular hypertensive, cynomolgus monkeys by 4.7, 5.9 and 9.6 mm Hg, respectively. The decline of 9.6 mm Hg represented a reduction of 27% from the corresponding vehicle-treated value of 35.3 mm Hg. Peak reductions in IOP were present at 2 to 4 hr after the instillation of the three doses and the ocular hypotensive effect was waning at 6 hr. The IOP of normotensive, monkey eyes was significantly lowered by 1% and 2% solutions of MK-927 with the effect being more transient in these eyes than in hypertensive eyes. The elevated IOP of alpha-chymotrypsinized rabbits was dose-dependently decreased by 0.01%, 0.1% and 0.5% solutions of MK-927. MK-927 modestly bound to rabbit ocular pigment in vitro and the concentrations of MK-927 in the iris + ciliary body of pigmented rabbits were higher than those in the same tissue of albino rabbits after dosing with 0.5% MK-927. The ocular hypotensive effect of 2% MK-927 was greater in magnitude and longer in duration in normal pigmented than in albino rabbits. The IOP lowering action of MK-927 was local as evidenced by results of ocular distribution studies and the observation that the unilateral instillation of 0.5% MK-927 into the contralateral eye was devoid of effect on the untreated, hypertensive eye of alpha-chymotrypsinized rabbits. MK-927 has been selected for topical evaluation in glaucoma patients.

Topically active carbonic anhydrase inhibitors. 1. O-acyl derivatives of 6-hydroxybenzothiazole-2-sulfonamide.

A series of O-acyl derivatives of 6-hydroxybenzothiazole-2-sulfonamide (4, L-643,799) was prepared and the potential utility of each series member as a topically active inhibitor of ocular carbonic anhydrase was determined. In vitro studies showed these esters to be substrates for ocular esterases which liberate 4 during corneal translocation. The most interesting series member, 2-sulfamoyl-6-benzothiazolyl 2,2-dimethylpropionate (22, L-645,151), acting as a prodrug form of 4, was found to enhance delivery through the isolated albino rabbit cornea by 40-fold when compared to the parent phenol 4. Studies in rabbits revealed that 22 is a potent topically active ocular hypotensive carbonic anhydrase inhibitor.

(Acyloxy)alkyl carbamates as novel bioreversible prodrugs for amines: increased permeation through biological membranes.

(Acyloxy)alkyl carbamates of the type R1R2N-CO-O-CHR3-OCO-R4 are described as novel bioreversible prodrugs for primary and secondary amines. These were prepared either by a one-step reaction involving nucleophilic attack on p-nitrophenyl alpha-(acyloxy)alkyl carbonates with displacement of p-nitrophenol or by reaction of alpha-haloalkyl carbamates with silver or mercury salts of carboxylic acids. Enzymatic hydrolysis of the ester bond in these ester carbamates leads to a cascade reaction resulting in rapid regeneration of the parent amine. Permeability measurements of such nonionic derivatives of atenolol, betaxolol, pindolol, propranolol, and timolol through fuzzy rat skin and rabbit cornea mounted on diffusion cells show that derivatization of the hydrophilic beta-blockers results in several-fold increase in permeation through these biological membranes. However, prodrug modification of the lipophilic beta-blockers leads to little advantage in permeability characteristics.

Thienothiopyran-2-sulfonamides: a novel class of water-soluble carbonic anhydrase inhibitors.

An attempt to develop a water-soluble carbonic anhydrase inhibitor focused on exploring structure-activity relationships in the thienothiopyransulfonamide class. The strategy to influence water solubility while retaining carbonic anhydrase activity involved the introduction of a hydroxyl moiety and adjusting the oxidation state of the sulfur on the thiopyran portion of the molecule. Compounds 4 and 17 best fit the criteria of aqueous solubility and inhibitory potency vs. human carbonic anhydrase II and are candidates for evaluation as topically effective antiglaucoma agents.

The nonenzymatic displacement of the sulfamoyl group from different classes of aromatic compounds by glutathione and cysteine.

The rates of reaction for the nonenzymatic conjugation of reduced glutathione and L-cysteine to a series of 5-substituted 1,3,4-thiadiazole- and 1,3,4-thiadiazoline-2-sulfonamides, ring-fused 1,3,4-thiadiazole-2-sulfonamides, and substituted benzenesulfonamides have been measured under simulated physiological conditions. The reactivities toward conjugation at pH 7.5 within two series of 5-substituted 1,3,4-thiadiazole- and 1,3,4-thiadiazoline-2-sulfonamides (methazolamide derivatives) conformed to the Brønsted relationship, the rate of conjugation increasing as sulfonamide pK, decreased. Reaction rate was found to vary from k = 0.07 X 10(-3) min-1 for X (pKa = 7.7) to k = 275 X 10(-3) min-1 for IX (pKa = 7.05). All substituted benzenesulfonamides and several 1,3,4-thiadiazole-2-sulfonamides with pKa values above 9 were unreactive toward conjugation. The data presumably explain the fate of many of these compounds in vivo, for example the fact that acetazolamide (I) is excreted unchanged while methazolamide (XI) and ethoxolamide (XVII) are partially metabolized.

Inhibitors of glycolic acid oxidase. 4-substituted 2,4-dioxobutanoic acid derivatives.

Fourteen new 4-substituted 2,4-dioxobutanoic acids have been synthesized. These compounds, all of which contain lipophilic 4-substituents, are potent inhibitors in vitro of porcine liver glycolic acid oxidase. The I50 value of the two most potent representatives, 4-(4'-bromo[1,1'-biphenyl]-4-yl)-2, 4-dioxobutanoic acid (8) and 4-[4'-[[(3,4-dihydro-3-hydroxy-2H-1, 5-benzodioxepin-3-yl)methyl]thio][1,1'-biphenyl]-4-yl]-2, 4-dioxobutanoic acid (13) is 6 X 10(-8)M.

Inhibitors of glycolic acid oxidase. 4-Substituted 3-hydroxy-1H-pyrrole-2,5-dione derivatives.

An extensive series of novel 4-substituted 3-hydroxy-1H-pyrrole-2,5-dione derivatives has been prepared and studied as inhibitors of glycolic acid oxidase (GAO). Compounds possessing large lipophilic 4-substituents are, in general, potent, competitive inhibitors of porcine liver GAO in vitro. Methylation of the nitrogen or the 3-hydroxy substituent reduced potency dramatically, indicating the requirement for the two acidic functions on the 1H-pyrrole-2,5-dione nucleus. In rat liver perfusion studies, with three representative compounds, concentration-dependent inhibition of the conversion of [1-14C]glycolate to [14C]oxalate was observed. Chronic oral administration to ethylene glycol fed rats of the 4-(4'-bromo[1,1'-biphenyl]-4-yl) derivative (83) was shown to effect a significant reduction in urinary oxalate levels over a 58-day period.

Quantitative structure-activity relationships involving the inhibition of glycolic acid oxidase by derivatives of glycolic and glyoxylic acids.

The enzyme glycolic acid oxidase oxidizes glycolate to glyoxylate and glyoxylate to oxalate. Three series of compounds related to the natural substrates, substituted glycolic, oxyacetic, and glyoxylic acids, have been investigated as inhibitors of this enzyme using the techniques of regression analysis and quantitative structure-activity relationships. The best overall correlation with inhibitory potencies was found with the Hansch hydrophobic parameter pi. The classical electronic parameters sigmap, sigmam, F, and R performed poorly. For the substituted glyoxylic acids, a dummy parameter relating to the presence of a nucleophilic group in close proximity to the alpha-carbonyl of the glyoxylate group was found to be highly significant. The syntheses of six novel glycolic and glyoxylic acids are described.