Adenosine kinase inhibitors. 6. Synthesis, water solubility, and antinociceptive activity of 5-phenyl-7-(5-deoxy-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidines substituted at C4 with glycinamides and related compounds.
4-(Phenylamino)-5-phenyl-7-(5-deoxy-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine 1 and related compounds known as "diaryltubercidin" analogues are potent inhibitors of adenosine kinase (AK) and are orally active in animal models of pain such as the rat formalin paw model (GP3269 ED50= 6.4 mg/kg). However, the utility of this compound class is limited by poor water solubility that can be attributed to the high energy of crystallization caused by stacking of the parallel C4 and C5 aryl rings in the solid state (compound 1 and GP3269 each with pH 7.4 solubility <0.05 microg/mL). To increase water solubility, the hydrophobic C4-phenylamino substituent was replaced with a more hydrophilic group, glycinamide. This modification resulted in improved water solubility while retaining AK inhibition potency. Analogues were studied where changes in the glycinamide moiety were combined with changes to the base and sugar. A lead compound, 4-N-(N-cyclopropylcarbamoylmethyl)amino-5-phenyl-7-(5-deoxy-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (16c) (IC50= 3 nM and water solubility = 32 +/- 9 microg/mL at pH 7.4), was further characterized in biological assays. Compound 16c exhibited strong oral efficacy in the rat formalin paw model (ED50 of 2.5 mg/kg). In the most advanced assay, 16c was found to inhibit bradykinin-induced licking in marmoset monkeys with an ED50 estimated at 0.9 mg/kg without producing evidence of side effects such as ataxia, sedation, and emesis at this dose. However, lethal toxicity in the rat formalin paw model occurred with high doses of 16c, and further work on this series was discontinued.
Bookser
Brett C
BC
Metabasis Therapeutics, Inc., 9390 Towne Centre Drive, San Diego, California 92121, USA. bookser@mbasis.com
Ugarkar
Bheemarao G
BG
Matelich
Michael C
MC
Lemus
Robert H
RH
Allan
Matthew
M
Tsuchiya
Megumi
M
Nakane
Masami
M
Nagahisa
Atsushi
A
Wiesner
James B
JB
Erion
Mark D
MD
D000248:Adenosine Kinase / Q000037:antagonists & inhibitors*; D000700:Analgesics / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D001682:Biological Availability; D002144:Callithrix; D004285:Dogs; D004355:Drug Stability; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D009705:Nucleosides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010147:Pain Measurement; D011741:Pyrimidine Nucleosides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D012995:Solubility; D013329:Structure-Activity Relationship; D014867:Water
C507722:4-N-(N-cyclopropylcarbamoylmethyl)amino-5-phenyl-7-(5-deoxyribofuranosyl)pyrrolo(2,3-d)pyrimidine; D000700:Analgesics; D009705:Nucleosides; D011741:Pyrimidine Nucleosides; D014867:Water; C018556:glycine amide; D000248:Adenosine Kinase; D005998:Glycine