5-HT3 receptor antagonists. 2. 4-Hydroxy-3-quinolinecarboxylic acid derivatives.
A series of 4-hydroxy-3-quinolinecarboxylic acid derivatives (6) and 4-hydroxy-2-oxo-1,2-dihydro-3-quinolinecarboxylic acid derivatives (7) were designed and synthesized as 5-HT3 receptor antagonists. Molecular modeling studies suggested that the 3-carbonyl moiety in 6 was almost coplanar to the plane of an aromatic ring, but in 7 there was a 30 degrees deviation. 4-Hydroxy substitution in quinoline derivatives enhanced affinity for the 5-HT3 receptors, and endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-4-hydroxy-3- quinolinecarboxamide (6f) exhibited the most potent activity in the Bezold-Jarisch (B-J) reflex test (ED50 = 0.1 micrograms/kg, iv) among quinoline derivatives 6. Although 4-hydroxy-2-oxo-1,2-dihydro-3-quinolinecarboxamide derivatives (7a) exhibited higher affinity (e.g., 7d: Ki = 0.48 nM) for the 5-HT3 receptors than ondansetron (Ki = 7.6 nM) or granisetron (Ki = 2.1 nM), these amides showed less potent activity in the B-J reflex test than the reference compounds. Interestingly, the ester derivatives 7c, 7f, and 7h eliminated affinity for the 5-HT3 receptors. These unusual structure-activity relationships and the deviation of the 3-carbonyl moiety from the plane of an aromatic ring suggest that the active conformation of 7a might be different from the proposed one for the preceding 5-HT3 antagonists. Thus, 6f was chosen for further studies. No receptor binding for a variety of ligands was significantly antagonized by 6f. Comparing the ratios of the ED50 value in the B-J reflex test (rat, iv) with the LD50 value in acute lethal toxicity (mouse, iv), 6f was proved to have a 600-fold wider margin of safety than ondansetron. Compound 6f dose-dependently attenuated both the incidence and frequency of emetic episodes induced by cisplatin in the dog (ED50 = 14 micrograms/kg, iv) more potently than ondansetron (ED50 = 210 micrograms/kg, iv). Compound 6f (KF-20170) is now under further investigation as a drug for treating gastrointestinal disorder.
Pharmaceutical Research Laboratories, Kyowa Hakko Kogyo Company, Ltd., Shizuoka-ken, Japan.
H
H
Hayashi
Y
Y
Miwa
S
S
Ichikawa
N
N
Yoda
I
I
Miki
A
A
Ishii
M
M
Kono
T
T
Yasuzawa
F
F
Suzuki
D000818:Animals; D000932:Antiemetics / Q000138:chemical synthesis / Q000627:therapeutic use; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis* / Q000494:pharmacology / Q000627:therapeutic use; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002945:Cisplatin; D004285:Dogs; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D008958:Models, Molecular; D015394:Molecular Structure; D017294:Ondansetron / Q000494:pharmacology; D011804:Quinolines / Q000138:chemical synthesis* / Q000494:pharmacology / Q000627:therapeutic use; D011814:Quipazine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists; D013329:Structure-Activity Relationship; D014839:Vomiting / Q000139:chemically induced / Q000517:prevention & control
D000932:Antiemetics; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D011804:Quinolines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C081342:N-(8-methyl-8-azabicyclo(3.2.1)oct-3-yl)-4-hydroxy-3-quinolinecarboxamide; D012701:Serotonin; D017294:Ondansetron; D011814:Quipazine; D002945:Cisplatin