Discovery of ß-d-2'-deoxy-2'-dichlorouridine nucleotide prodrugs as potent inhibitors of hepatitis C virus replication.

Discovery of sofosbuvir has radically changed hepatitis C treatment and nucleoside/tide NS5B inhibitors are now viewed as one of the key components in combination therapies with other direct-acting antiviral agents. As part of our program to identify new nucleoside inhibitors of HCV replication, we now wish to report on the discovery of ß-d-2'-deoxy-2'-dichlorouridine nucleotide prodrugs as potent inhibitors of HCV replication. Although, cytidine analogues have long been recognized to be metabolized to both cytidine and uridine triphosphates through the action of cytidine deaminase, uridine analogues are generally believed to produce exclusively uridine triphosphate. Detailed investigation of the intracellular metabolism of our newly discovered uridine prodrugs, as well as of sofosbuvir, has now revealed the formation of both uridine and cytidine triphosphates. This occurs, not only in vitro in cell lines, but also in vivo upon oral dosing to dogs.

Synthesis and SAR of potent inhibitors of the Hepatitis C virus NS3/4A protease: exploration of P2 quinazoline substituents.

Novel NS3/4A protease inhibitors comprising quinazoline derivatives as P2 substituent were synthesized. High potency inhibitors displaying advantageous PK properties have been obtained through the optimization of quinazoline P2 substituents in three series exhibiting macrocyclic P2 cyclopentane dicarboxylic acid and P2 proline urea motifs. For the quinazoline moiety it was found that 8-methyl substitution in the P2 cyclopentane dicarboxylic acid series improved on the metabolic stability in human liver microsomes. By comparison, the proline urea series displayed advantageous Caco-2 permeability over the cyclopentane series. Pharmacokinetic properties in vivo were assessed in rat on selected compounds, where excellent exposure and liver-to-plasma ratios were demonstrated for a member of the 14-membered quinazoline substituted P2 proline urea series.

Solid-phase parallel synthesis and SAR of 4-amidofuran-3-one inhibitors of cathepsin S: effect of sulfonamides P3 substituents on potency and selectivity.

Highly potent and selective 4-amidofuran-3-one inhibitors of cathepsin S are described. The synthesis and structure-activity relationship of a series of inhibitors with a sulfonamide moiety in the P3 position is presented. Several members of the series show sub-nanomolar inhibition of the target enzyme as well as an excellent selectivity profile and good cellular potency. Molecular modeling of the most interesting inhibitors describes interactions in the extended S3 pocket and explains the observed selectivity towards cathepsin K.

Discovery of novel, potent and bioavailable proline-urea based macrocyclic HCV NS3/4A protease inhibitors.

A novel series of P3-truncated macrocyclic HCV NS3/4A protease inhibitors containing a P2 proline-urea or carbamate scaffold was synthesized. Very potent inhibitors were obtained through the optimization of the macrocycle size, urea and proline substitution, and bioisosteric replacement of the P1 carboxylic acid moiety. Variation of the lipophilicity by introduction of small lipophilic substituents resulted in improved PK profiles, ultimately leading to compound 13Bh, an extremely potent (K(i)=0.1 nM, EC(50)=4.5 nM) and selective (CC(50) (Huh-7 cells)>50 microM) inhibitor, displaying an excellent PK profile in rats characterized by an oral bioavailability of 54% and a high liver exposure after oral administration.

Novel potent macrocyclic inhibitors of the hepatitis C virus NS3 protease: use of cyclopentane and cyclopentene P2-motifs.

Several highly potent novel HCV NS3 protease inhibitors have been developed from two inhibitor series containing either a P2 trisubstituted macrocyclic cyclopentane- or a P2 cyclopentene dicarboxylic acid moiety as surrogates for the widely used N-acyl-(4R)-hydroxyproline in the P2 position. These inhibitors were optimized for anti HCV activities through examination of different ring sizes in the macrocyclic systems and further by exploring the effect of P4 substituent removal on potency. The target molecules were synthesized from readily available starting materials, furnishing the inhibitor compounds in good overall yields. It was found that the 14-membered ring system was the most potent in these two series and that the corresponding 13-, 15-, and 16-membered macrocyclic rings delivered less potent inhibitors. Moreover, the corresponding P1 acylsulfonamides had superior potencies over the corresponding P1 carboxylic acids. It is noteworthy that it has been possible to develop highly potent HCV protease inhibitors that altogether lack the P4 substituent. Thus the most potent inhibitor described in this work, inhibitor 20, displays a K(i) value of 0.41 nM and an EC(50) value of 9 nM in the subgenomic HCV replicon cell model on genotype 1b. To the best of our knowledge this is the first example described in the literature of a HCV protease inhibitor displaying high potency in the replicon assay and lacking the P4 substituent, a finding which should facilitate the development of orally active small molecule inhibitors against the HCV protease.