Synthesis and biological evaluation of deuterated sofosbuvir analogs as HCV NS5B inhibitors with enhanced pharmacokinetic properties.

A series of deuterated sofosbuvir analogs were designed and prepared with the aim of improving their pharmacokinetic properties. The devised synthetic routes allow for site-selective deuterium incorporation with high levels of isotopic purity. As expected, the deuterated analogs (37-44) are as efficacious as sofosbuvir when tested in vitro inhibition of viral replication (replicon) assays. Compared with sofosbuvir, deuterated analog 40 displays improved in vivo pharmacokinetics profiles in rats and dogs in terms of the metabolite and the prodrug. The Cmax and area under the curve (AUC) of 40 in dogs were increased by 3.4- and 2.7-fold, respectively. Due to the enhanced pharmacokinetic properties and the great synthetic advantage of an inexpensive deuterium source (D2 O) for 40, it was chosen for further investigation.

Discovery of pyrimidine nucleoside dual prodrugs and pyrazine nucleosides as novel anti-HCV agents.

To explore the application potential of dual prodrug strategies in the development of anti-HCV agents, a variety of sofosbuvir derivatives with modifications at the C4 or N3 position of the uracil moiety were designed and synthesized. Some compounds exhibited potent anti-HCV activities, such as 4e and 8a-8c with similar EC50 values (0.20-0.22 µM) comparative to that of sofosbuvir (EC50 = 0.18 µM) in a genotype 1b based replicon Huh-7 cell line. Moreover, 8b displayed a good human plasma stability profile, and was easily metabolized in human liver microsomes expectantly. On the other hand, aiming to discover novel anti-HCV nucleosides, pyrazin-2(1H)-one nucleosides and their phosphoramidate prodrugs were investigated. Several active compounds were discovered, such as 25e (EC50 = 7.3 µM) and S-29b (EC50 = 19.5 µM). This kind of nucleosides were interesting and would open a new avenue for the development of antiviral agents.

Changing the face of hepatitis C management - the design and development of sofosbuvir.

The availability of direct-acting antiviral (DAA) therapy has launched a new era in the management of chronic hepatitis C. Sofosbuvir, a uridine nucleotide analog that inhibits the hepatitis C RNA-dependent RNA polymerase, is the backbone of chronic hepatitis C therapy. Acting at the catalytic site of the polymerase, sofosbuvir is highly potent in suppressing viral replication and has a high genetic barrier to resistance. Sofosbuvir is effective across all hepatitis C genotypes, and is a mainstay of interferon-free combination therapy. In Phase II and III studies, genotype 1 patients who took sofosbuvir in combination with another DAA such as the NS3-4A protease inhibitor, simeprevir, or the NS5A replication complex inhibitors, ledipasvir or daclatasvir, achieved a sustained virologic response rate of over 90%. Harvoni(®), a combination tablet of sofosbuvir and ledipasvir, dosed once daily is recommended for 24 weeks for treatment-experienced genotype 1 patients with cirrhosis, but 12 weeks of therapy is sufficient for all other populations. While genotype 2 (12 weeks or 16 weeks) and treatment-naïve genotype 3 patients (24 weeks) have excellent response rates with sofosbuvir and ribavirin, treatment-experienced cirrhotic genotype 3 patients may need the addition of another DAA such as daclatasvir. Sofosbuvir is efficacious in special populations such as HIV-hepatitis C virus-coinfected patients and liver transplant recipients and has already made a profound impact in these groups. Since it is renally eliminated, patients with advanced kidney disease or on dialysis must await dosing recommendations. Sofosbuvir-based regimens appear to be well tolerated with headache and fatigue being the most common side effects. The opportunity to cure patients with hepatitis C with sofosbuvir combination therapy is likely to change the future for our patients, particularly if the emphasis shifts to identifying those patients unaware that they are infected and providing affordable access to treatment.