Cabergoline: Pharmacology, ocular hypotensive studies in multiple species, and aqueous humor dynamic modulation in the Cynomolgus monkey eyes.

The aims of the current studies were to determine the in vitro and in vivo ocular and non-ocular pharmacological properties of cabergoline using well documented receptor binding, cell-based functional assays, and in vivo models. Cabergoline bound to native and/or human cloned serotonin-2A/B/C (5HT(2A/B/C)), 5HT(1A), 5HT(7), alpha(2B), and dopamine-2/3 (D(2/3)) receptor subtypes with nanomolar affinity. Cabergoline was an agonist at human recombinant 5HT(2), 5HT(1A) and D(2/3) receptors but an antagonist at 5HT(7) and alpha(2) receptors. In primary human ciliary muscle (h-CM) and trabecular meshwork (h-TM) cells, cabergoline stimulated phosphoinositide (PI) hydrolysis (EC(50)=19+/-7 nM in TM; 76 nM in h-CM) and intracellular Ca(2+) ([Ca(2+)](i)) mobilization (EC(50)=570+/-83 nM in h-TM; EC(50)=900+/-320 nM in h-CM). Cabergoline-induced [Ca(2+)](i) mobilization in h-TM and h-CM cells was potently antagonized by a 5HT(2A)-selective antagonist (M-100907, K(i)=0.29-0.53 nM). Cabergoline also stimulated [Ca(2+)](i) mobilization more potently via human cloned 5HT(2A) (EC(50)=63.4+/-10.3 nM) than via 5HT(2B) and 5HT(2C) receptors. In h-CM cells, cabergoline (1 microM) stimulated production of pro-matrix metalloproteinases-1 and -3 and synergized with forskolin to enhance cAMP production. Cabergoline (1 microM) perfused through anterior segments of porcine eyes caused a significant (27%) increase in outflow facility. Topically administered cabergoline (300-500 microg) in Dutch-belted rabbit eyes yielded 4.5 microMM and 1.97 microM levels in the aqueous humor 30 min and 90 min post-dose but failed to modulate intraocular pressure (IOP). However, cabergoline was an efficacious IOP-lowering agent in normotensive Brown Norway rats (25% IOP decrease with 6 microg at 4h post-dose) and in conscious ocular hypertensive cynomolgus monkeys (peak reduction of 30.6+/-3.6% with 50 microg at 3h post-dose; 30.4+/-4.5% with 500 microg at 7h post-dose). In ketamine-sedated monkeys, IOP was significantly lowered at 2.5h after the second topical ocular dose (300 microg) of cabergoline by 23% (p<0.02) and 35% (p<0.004) in normotensive and ocular hypertensive eyes, respectively. In normotensive eyes, cabergoline increased uveoscleral outflow (0.69+/-0.7 microL/min-1.61+/-0.97 microL/min, n=13; p<0.01). However, only seven of the eleven ocular hypertensive monkeys showed significantly increased uveoscleral outflow. These data indicate that cabergoline's most prominent agonist activity involves activation of 5HT(2), 5HT(1A), and D(2/3) receptors. Since 5HT(1A) agonists, 5HT(7) antagonists, and alpha(2) antagonists do not lower IOP in conscious ocular hypertensive monkeys, the 5HT(2) and dopaminergic agonist activities of cabergoline probably mediated the IOP reduction observed with this compound in this species.

AL-34662: a potent, selective, and efficacious ocular hypotensive serotonin-2 receptor agonist.

PURPOSE AND METHODS: The aim of this study was to determine the ocular pharmacological characteristics of AL-34662 (1-((S)-2-aminopropyl)-1H-indazole-6-ol), a new synthetic serotonin-2 (5-HT2) receptor-agonist ocular hypotensive agent. A variety of well-documented in vitro and in vivo procedures were utilized to study the pharmacological attributes of AL-34662. RESULTS: AL-34662 exhibited a high affinity for the rat and human 5-HT2 receptor (IC50=0.8-1.5 nM) and for cloned human 5-HT2A-C receptors (IC50=3-14.5 nM). AL-34662 stimulated phosphoinositide turnover in human ciliary muscle (h-CM; EC50=289+/-80 nM) and in human trabecular meshwork (h-TM; EC50=254+/-50 nM) cells. AL-34662 also mobilized intracellular Ca2+ ([Ca2+]i) in h-CM (EC50=140+/-23 nM) and h-TM (EC50=38+/-8 nM) cells, being a full agonist like 5-HT itself. AL-34662's effects in the h-CM (and h-TM) cells were potently antagonized by 5-HT2A-antagonist M-100907 (IC50=1.8+/-0.7 nM), but weakly by 5-HT2B-antagonist (RS-127445 IC50>10 microM), 5-HT2B/C- antagonist (SB-242084 IC50=2.08 microM) and 5-HT2C antagonist (RS-102221 IC50>1 microM). AL-34662 caused relatively minimal ocular discomfort and hyperemia in rabbit and guinea pig eyes. It efficaciously lowered intraocular pressure (IOP) in the conscious ocular hypertensive monkey eyes (33% at 300 microg). The (R)-enantiomer (AL-34707) and the racemate (AL-34497) were less potent and/or efficacious than AL-34662 in all of these assays. CONCLUSIONS: AL-34662 is a high-affinity 5-HT2 receptor agonist that potently mobilizes [Ca2+]i in h-CM and h-TM cells, and which efficaciously lowers IOP in conscious ocular hypertensive cynomolgus monkey eyes through a local effect with minimal side-effects.

Preclinical pharmacology of AL-12182, a new ocular hypotensive 11-oxa prostaglandin analog.

PURPOSE: The aim of this study was to determine selected in vivo ocular properties of AL-12182 (5,6-dihydro-4,5-didehydro-11-deoxy-11-oxa-16-(3-chlorophenoxy)-omega-tetranor-PGF(2alpha) isopropyl ester) and the in vitro profile of its free acid, AL-12180. METHODS: Previously documented radioligand binding and functional assays involving human ciliary muscle cells (h-CM), human trabecular meshwork (h-TM) and other cells, and porcine ocular arteries were utilized. For in vivo procedures, we utilized rabbits, cats, and nonhuman primates to measure hyperemia, pupil diameter, and intraocular pressure (IOP), respectively. RESULTS: AL-12180 exhibited the highest affinity for the FP-receptor (K(i) = 143 +/- 36 nM) and much lower affinity for DP-, EP(3)-, IP-, and TP-receptors, and for several nonprostanoid receptors, enzymes, neurotransmitter uptake sites, ion channels, and other regulatory sites. AL-12180 activated phospholipase C-mediated phosphoinositide hydrolysis (potency, EC(50) = 13.7-42.7 nM) through the FP-receptor in a variety of cells, such as h-CM, h-TM cells, human embryonic kidney cells expressing the cloned human ciliary body FP-receptor (HEK-FP), mouse 3T3 cells, and rat vascular smooth muscle cells. AL-8810, an FP-antagonist, blocked the effects of AL-12180 in h-CM cells (IC(50) = 8.7 microM). AL-12180 also stimulated the mobilization of intracellular Ca(2+) ([Ca(2+)](i)) in h-TM cells (EC(50) = 111 +/- 36 nM), h-CM cells (EC(50) = 11 nM), and in host cells expressing the cloned human ciliary body FP-receptor (EC(50) = 5.9 +/- 3.1 nM). AL-12180 lacked significant agonist activity at DP-, EP(2)-, EP(4)-, IP-, and TP-receptors in cell-based assays. However, AL-12180 contracted porcine central retinal and short posterior ciliary arteries in vitro with micromolar potencies that appeared to involve TP-receptor activation. in vivo, AL-12182 elicited dose-related hyperemia in the rabbit eye, miosis in the cat eye, and ocular hypotension in the nonhuman primate eye. CONCLUSIONS: AL-12180 is a relatively potent and selective FP-receptor agonist whose isopropyl ester prodrug (AL-12182) lowers IOP by as much as 40% following topical ocular dosing in a laser-induced nonhuman primate model of ocular hypertension.