Beta-oxygenated analogues of the 5-HT2A serotonin receptor agonist 1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane.
Activation of 5-HT(2A) serotonin receptors represents a novel approach to lowering intraocular pressure. Because 5-HT(2A) serotonin receptor agonists might also produce undesirable central effects should sufficient quantities enter the brain, attempts were made to identify 5-HT(2) serotonin receptor agonists with reduced propensity to penetrate the blood-brain barrier. 1-(4-Bromo-2,5-dimethoxyphenyl)-2-aminopropan-1-ol (6), an analogue of the 5-HT(2) serotonin receptor agonist 1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane (DOB; 1a) bearing a benzylic hydroxyl group, was identified as a candidate structure. Of the four optical isomers of 6, the 1R,2R-isomer (6d; K(i) = 0.5 nM) was found to bind at 5-HT(2A) receptors with an affinity similar to that of R(-)DOB (K(i) = 0.2 nM). Like R(-)DOB, 6d behaved as a partial agonist (efficacy ca. 50%) in a 5-HT(2)-mediated calcium mobilization assay. However, in an in vivo test of central action (i.e., stimulus generalization with rats as subjects), 6d was >15 times less potent than R(-)DOB. O-Methylation of 6d (i.e., 7d; 5-HT(2A) K(i) = 0.3 nM) resulted in an agent that behaved as a full (93% efficacy) agonist. Intraocular administration of 300 microg of 6d and 7d to ocular hypertensive monkeys was shown to reduce intraocular pressure by 20-27%. Given the route of administration (i.e., topical), and concentrations necessary to reduce intraocular pressure, compounds such as 6d should demonstrate minimal central effects at potentially useful therapeutic doses and offer useful leads for further development.
Glennon
Richard A
RA
Department of Medicinal Chemistry, Box 980540, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, USA. glennon@hsc.vcu.edu
Bondarev
Mikhail L
ML
Khorana
Nantaka
N
Young
Richard
R
May
Jesse A
JA
Hellberg
Mark R
MR
McLaughlin
Marsha A
MA
Sharif
Najam A
NA
D004290:DOM 2,5-Dimethoxy-4-Methylamphetamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001667:Binding, Competitive; D001812:Blood-Brain Barrier; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004193:Discrimination Learning / Q000187:drug effects; D007429:Intraocular Pressure / Q000187:drug effects; D008252:Macaca fascicularis; D008297:Male; D009798:Ocular Hypertension / Q000188:drug therapy / Q000503:physiopathology; D010100:Oxygen / Q000737:chemistry*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D058826:Serotonin 5-HT2 Receptor Agonists; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D000959:Antihypertensive Agents; D058826:Serotonin 5-HT2 Receptor Agonists; D004290:DOM 2,5-Dimethoxy-4-Methylamphetamine; C003943:2,5-dimethoxy-4-bromoamphetamine; D010100:Oxygen