Structure-Based Design, Synthesis, and Biological Evaluation of Irreversible Human Rhinovirus 3C Protease Inhibitors. 8. Pharmacological Optimization of Orally Bioavailable 2-Pyridone-Containing Peptidomimetics

Abstract

The optimization of the pharmacokinetic performance of various 2-pyridone-containing human rhinovirus (HRV) 3C protease (3CP) inhibitors following oral administration to either beagle dogs or CM-monkeys is described. The molecules described in this work are composed of a 2-pyridone-containing peptidomimetic binding determinant and an alpha,beta-unsaturated ester Michael acceptor moiety which forms an irreversible covalent adduct with the active site cysteine residue of the 3C enzyme. Modification of the ester contained within these compounds is detailed along with alteration of the P(2) substituent present in the peptidomimetic portion of the inhibitors. The pharmacokinetics of several inhibitors in both dogs and monkeys are described (7 h plasma concentrations after oral administration) along with their human plasma stabilities, stabilities in incubations with human, dog, and monkey microsomes and hepatocytes, Caco-2 permeabilities, and aqueous solubilities. Compounds containing an alpha,beta-unsaturated ethyl ester fragment and either an ethyl or propargyl P(2) moiety displayed the most promising combination of 3C enzyme inhibition (k(obs)/[I] 170 000-223 000 M(-1) s(-1)), antiviral activity (EC(50) = 0.047-0.058 microM, mean vs seven HRV serotypes), and pharmacokinetics following oral administration (7 h dog plasma levels = 0.248-0.682 microM; 7 h CM-monkey plasma levels = 0.057-0.896 microM).

Selective inhibitors of picornavirus replication

“…Replacement of the P 2 benzylic substituent in compound XVIII with a propynyl fragment furnished the irreversible inhibitor ''compound XXI,'' also referred to as ''compound 1'' (Table II). 334,352 This compound demonstrated oral bioavailability in dogs and CM-monkeys with 7-hr plasma concentrations similar to or exceeding the in vitro antiviral activity against the seven HRV serotypes evaluated. 352 In addition, in cell-based assays, the compound was active against 35 different HRV genotypes, against 5 clinical isolates and 8 related picornaviruses with EC 50 values ranging between 7 and 249 nM (Table II).…”

“…334,352 This compound demonstrated oral bioavailability in dogs and CM-monkeys with 7-hr plasma concentrations similar to or exceeding the in vitro antiviral activity against the seven HRV serotypes evaluated. 352 In addition, in cell-based assays, the compound was active against 35 different HRV genotypes, against 5 clinical isolates and 8 related picornaviruses with EC 50 values ranging between 7 and 249 nM (Table II). 334 In vitro and in vivo non-clinical safety studies showed compound XXI to be without adverse effects at maximum achievable doses.…”

“…353 Replacement of the P 2 benzylic substituent in compound XVIII with an ethyl fragment led to compound XX (Table II) which exhibited plasma concentrations in the dog 7 hr after oral administration more than 14-fold greater than the EC 50 value (i.e., C 7h ¼ 0.682 mM vs. mean EC 50 ¼ 0.047 mM). 352 Similarly, oral administration of this compound to CM-monkeys afforded 7 hr plasma concentrations (i.e., C 7h ¼ 0.896 mM) that far exceeded in vitro the EC 50 value. Replacement of the P 2 benzylic substituent in compound XVIII with a propynyl fragment furnished the irreversible inhibitor ''compound XXI,'' also referred to as ''compound 1'' (Table II).…”

“…Unfortunately, the inhibitor was poorly bioavailable when orally delivered in solution to CMmonkeys. 352 The incorporation of a bicyclic 2-pyridone moiety in the inhibitor design did not improve overall antiviral activity (compound XIX, Table II). 353 Replacement of the P 2 benzylic substituent in compound XVIII with an ethyl fragment led to compound XX (Table II) which exhibited plasma concentrations in the dog 7 hr after oral administration more than 14-fold greater than the EC 50 value (i.e., C 7h ¼ 0.682 mM vs. mean EC 50 ¼ 0.047 mM).…”

Poliovirus Studies during the Endgame of the Polio Eradication Program

“…The effectiveness V-073 in treating neonatal enteroviral sepsis was recently reported (70), and V-073 is currently in a clinical trial as an anti-PV antiviral (EudraCT Number: 2011-004804-38). Viral 2A protease, 2C helicase, 3C protease, and 3D polymerase have also been identified as potential targets of direct-acting antiviral agents, including elastase inhibitors (2A inhibitor) (71), guanidine hydrochloride and related compounds (2C inhibitor) (72)(73)(74)(75), rupintrivir (AG-7088) or AG-7404 (3C inhibitor) (76)(77)(78), and ribavirin (79,80), respectively. However, the efficacy of these candidates against PV infection in vivo remains to be clarified.…”