In vitro antiviral activity and single-dose pharmacokinetics in humans of a novel, orally bioavailable inhibitor of human rhinovirus 3C protease.
(E)-(S)-4-((S)-2-{3-[(5-methyl-isoxazole-3-carbonyl)-amino]-2-oxo-2H-pyridin-1-yl}-pent-4-ynoylamino)-5-((S)-2-oxo-pyrrolidin-3-yl)-pent-2-enoic acid ethyl ester (Compound 1) is a novel, irreversible inhibitor of human rhinovirus (HRV) 3C protease {inactivation rate constant (Kobs/[I]) of 223,000 M-1s-1}. In cell-based assays, Compound 1 was active against all HRV serotypes (35 of 35), HRV clinical isolates (5 of 5), and related picornaviruses (8 of 8) tested with mean 50% effective concentration (EC50) values of 50 nM (range, 14 to 122 nM), 77 nM (range, 72 to 89 nM), and 75 nM (range, 7 to 249 nM), respectively. Compound 1 inhibited HRV 3C-mediated polyprotein processing in infected cells in a concentration-dependent manner, providing direct confirmation that the cell-based antiviral activity is due to inhibition of 3C protease. In vitro and in vivo nonclinical safety studies showed Compound 1 to be without adverse effects at maximum achievable doses. Single oral doses of Compound 1 up to 2,000 mg in healthy volunteers were found to be safe and well tolerated in a phase I-ascending, single-dose study. Compound 1 estimated free observed maximum concentration in plasma (Cmax) for 500-, 1,000-, and 2,000-mg doses were higher than the protein binding-corrected EC50 required to inhibit 80% of the HRV serotypes tested. Treatment of HRV 52-infected cells with one to five 2-h pulses of 150 nM Compound 1 (corresponding to the Cmax at the 500-mg dose) was sufficient to effect a significant reduction in viral replication. These experiments highlight Compound 1 as a potent, orally bioavailable, irreversible inhibitor of HRV 3C protease and provide data that suggest that Cmax rather than the Cmin might be the key variable predicting clinical efficacy.
Patick
Amy K
AK
Department of Virology, Pfizer Global Research and Development, 10777 Science Center Drive, San Diego, CA 92121, USA. amy.patick@pfizer.com
Brothers
Mary A
MA
Maldonado
Fausto
F
Binford
Susan
S
Maldonado
Oscar
O
Fuhrman
Shella
S
Petersen
Annkatrin
A
Smith
George J
GJ
Zalman
Leora S
LS
Burns-Naas
Leigh Ann
LA
Tran
Jonathan Q
JQ
D000086042:3C Viral Proteases; D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000818:Animals; D000998:Antiviral Agents / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D001682:Biological Availability; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D004285:Dogs; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D012229:Rhinovirus / Q000145:classification / Q000187:drug effects* / Q000201:enzymology; D012703:Serotyping; D016896:Treatment Outcome; D014764:Viral Proteins / Q000037:antagonists & inhibitors*
D000998:Antiviral Agents; D015853:Cysteine Proteinase Inhibitors; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D000086042:3C Viral Proteases