Christian Sund

2′-Deoxy-4′-azido Nucleoside Analogs Are Highly Potent Inhibitors of Hepatitis C Virus Replication Despite the Lack of 2′-α-Hydroxyl Groups

RNA polymerases effectively discriminate against deoxyribonucleotides and specifically recognize ribonucleotide substrates most likely through direct hydrogen bonding interaction with the 2′-α-hydroxy moieties of ribonucleosides. Therefore, ribonucleoside analogs as inhibitors of viral RNA polymerases have mostly been designed to retain hydrogen bonding potential at this site for optimal inhibitory potency. Here, two novel nucleoside triphosphate analogs are described, which are efficiently incorporated into nascent RNA by the RNA-dependent RNA polymerase NS5B of hepatitis C virus (HCV), causing chain termination, despite the lack of α-hydroxy moieties. 2′-Deoxy-2′-β-fluoro-4′-azidocytidine (RO-0622) and 2′-deoxy-2′-β-hydroxy-4′-azidocytidine (RO-9187) were excellent substrates for deoxycytidine kinase and were phosphorylated with efficiencies up to 3-fold higher than deoxycytidine. As compared with previous reports on ribonucleosides, higher levels of triphosphate were formed from RO-9187 in primary human hepatocytes, and both compounds were potent inhibitors of HCV virus replication in the replicon system (IC50 = 171 ± 12 nm and 24 ± 3 nm for RO-9187 and RO-0622, respectively; CC50 >1 mm for both). Both compounds inhibited RNA synthesis by HCV polymerases from either HCV genotypes 1a and 1b or containing S96T or S282T point mutations with similar potencies, suggesting no cross-resistance with either R1479 (4′-azidocytidine) or 2′-C-methyl nucleosides. Pharmacokinetic studies with RO-9187 in rats and dogs showed that plasma concentrations exceeding HCV replicon IC50 values 8-150-fold could be achieved by low dose (10 mg/kg) oral administration. Therefore, 2′-α-deoxy-4′-azido nucleosides are a new class of antiviral nucleosides with promising preclinical properties as potential medicines for the treatment of HCV infection.

2'-deoxy-4'-azido nucleoside analogs are highly potent inhibitors of HCV replication despite the lack of 2'-alpha hydroxyl groups

RNA polymerases effectively discriminate against deoxyribonucleotides and specifically recognize ribonucleotide substrates most likely through direct hydrogen bonding interaction with the 2′-α-hydroxy moieties of ribonucleosides. Therefore, ribonucleoside analogs as inhibitors of viral RNA polymerases have mostly been designed to retain hydrogen bonding potential at this site for optimal inhibitory potency. Here, two novel nucleoside triphosphate analogs are described, which are efficiently incorporated into nascent RNA by the RNA-dependent RNA polymerase NS5B of hepatitis C virus (HCV), causing chain termination, despite the lack of α-hydroxy moieties. 2′-Deoxy-2′-β-fluoro-4′-azidocytidine (RO-0622) and 2′-deoxy-2′-β-hydroxy-4′-azidocytidine (RO-9187) were excellent substrates for deoxycytidine kinase and were phosphorylated with efficiencies up to 3-fold higher than deoxycytidine. As compared with previous reports on ribonucleosides, higher levels of triphosphate were formed from RO-9187 in primary human hepatocytes, and both compounds were potent inhibitors of HCV virus replication in the replicon system (IC50 = 171 ± 12 nm and 24 ± 3 nm for RO-9187 and RO-0622, respectively; CC50 >1 mm for both). Both compounds inhibited RNA synthesis by HCV polymerases from either HCV genotypes 1a and 1b or containing S96T or S282T point mutations with similar potencies, suggesting no cross-resistance with either R1479 (4′-azidocytidine) or 2′-C-methyl nucleosides. Pharmacokinetic studies with RO-9187 in rats and dogs showed that plasma concentrations exceeding HCV replicon IC50 values 8-150-fold could be achieved by low dose (10 mg/kg) oral administration. Therefore, 2′-α-deoxy-4′-azido nucleosides are a new class of antiviral nucleosides with promising preclinical properties as potential medicines for the treatment of HCV infection.

Design and synthesis of potent macrocyclic renin inhibitors.

Two types of P1-P3-linked macrocyclic renin inhibitors containing the hydroxyethylene isostere (HE) scaffold just outside the macrocyclic ring have been synthesized. An aromatic or aliphatic substituent (P3sp) was introduced in the macrocyclic ring aiming at the S3 subpocket (S3sp) in order to optimize the potency. A 5-6-fold improvement in both the K(i) and the human plasma renin activity (HPRA)IC(50) was observed when moving from the starting linear peptidomimetic compound 1 to the most potent macrocycle 42 (K(i) = 3.3 nM and HPRA IC(50) = 7 nM). Truncation of the prime side of 42 led to 8-10-fold loss of inhibitory activity in macrocycle 43 (K(i) = 34 nM and HPRA IC(50) = 56 nM). All macrocycles were epimeric mixtures in regard to the P3sp substituent and X-ray crystallographic data of the representative renin macrocycle 43 complex showed that only the S-isomer buried the substituent into the S3sp. Inhibitory selectivity over cathepsin D (Cat-D) and BACE-1 was also investigated for all the macrocycles and showed that truncation of the prime side increased selectivity of inhibition in favor of renin.

Modified 5'-trityl nucleosides as inhibitors of Plasmodium falciparum dUTPase.

2′‐Deoxyuridine triphosphate nucleotidohydrolase (dUTPase) is a potential drug target for the treatment of malaria. We previously reported the discovery of 5′‐tritylated analogues of deoxyuridine as selective inhibitors of this Plasmodium falciparum enzyme. Herein we report further structure–activity studies; in particular, variations of the 5′‐trityl group, the introduction of various substituents at the 3′‐position of deoxyuridine, and modifications of the base. Compounds were tested against both the enzyme and the parasite. Variations of the 5′‐trityl group and of the 3′‐substituent were well tolerated and yielded active compounds. However, there is a clear requirement for the uracil base for activity, because modifications of the uracil ring result in loss of enzyme inhibition and significant decreases in antiplasmodial action.

Design and synthesis of potent hydroxyethylamine (HEA) BACE-1 inhibitors carrying prime side 4,5,6,7-tetrahydrobenzazole and 4,5,6,7-tetrahydropyridinoazole templates.

A set of low molecular weight compounds containing a hydroxyethylamine (HEA) core structure with different prime side alkyl substituted 4,5,6,7-tetrahydrobenzazoles and one 4,5,6,7-tetrahydropyridinoazole was synthesized. Striking differences were observed on potencies in the BACE-1 enzymatic and cellular assays depending on the nature of the heteroatoms in the bicyclic ring, from the low active compound 4 to inhibitor 6, displaying BACE-1 IC(50) values of 44 nM (enzyme assay) and 65 nM (cell-based assay).