Compound containing dimethylglutarimide P cap
Compound containing, dimethylglutarimide P-cap, P propyl group, α-methylbenzyl urea resulted in inhibitor with much improved binding (=0.064μM) and EC=0.3μM. This was an aza-peptide analog with an EC comparable to our first generation clinical candidate . Analog was evaluated for its selectivity against human neutrophil elastase a structural homologous enzyme to HCV NS3 protease. The selectivity was determined to be (HNE)/(HCV)=960. Incorporation of bicyclic imide derived P cap with P propyl group and α-methylbenzyl urea resulted in sevelamer hcl receptor with a binding of =0.032μM and EC=0.25μM. This compound was more potent in binding and replicon cellular activity than the dimethylcyclohexylimide analog . It was also slightly more active than our first generation compound
In conclusion we have identified a series of novel aza-peptide derived series of HCV NS3 protease inhibitors that demonstrated excellent binding and cellular activity. This provides a possible avenue for depetidization of peptidic analogs of our first generation compound . By truncation of derived inhibitors we have identified a series of novel imide P-capped aza-peptide analogs that demonstrated excellent inhibition of HCV NS3 protease. SAR investigation of identified a phenethyl amide analog and phenylurea derivative which demonstrated submicro-molar enzyme binding activity and moderate cellular activities. Further modification of P and P-capping residue resulted in identification of potent analogs such as (=0.064μM; EC=0.30μM) and (=0.032μM; EC=0.25μM) that contained imide P capping and α-methylbenzyl urea and a propyl P groups. These inhibitors are similar in potency to our first generation clinical candidate , but desirably lack the electrophilic trap and epimerizable ketoamide center. In addition the urea carbonyl moiety is non-electrophilic and serine does not make a covalent bond with the inhibitor.
Infection with Hepatitis C Virus (HCV) is a major cause of human liver disease throughout the world, affecting over 200 million individuals. In the US alone, an estimated 4.5 million Americans are chronically infected. HCV infection is responsible for 40–60% of all chronic liver disease cases and 30% of all liver transplants. The current standard of care for HCV infection is a combination of injectable pegylated interferon-α (PEG IFN-α) plus oral ribavirin, which is effective in only about 50% of genotype-1 patients achieving sustained viral response. This protocol has been associated with side effects including neuropsychiatric events, flu-like symptoms and hematological toxicities. Therefore, there has been tremendous interest in the development of more effective therapeutics in treating HCV infection. One of the validated targets is HCV NS3/4A serine protease. Extensive efforts in the discovery of HCV NS3 protease inhibitors have resulted in a number of drug candidates at various stages of clinical development. The two most advanced compounds, VX-950 (telaprevir) and SCH-503034 (boceprevir), provided an early proof of concept in suppressing the virus and are currently undergoing Phase III clinical trials. Newer protease inhibitors with improved potency, different mode of binding interaction with the protease enzyme and pharmacokinetic properties have emerged. These inhibitors, such as danoprevir (ITMN-191), TMC-435, BMS-791325 (), and vaniprevir (MK-7009) are in clinical development representing structural diversity set of promising HCV protease inhibitors. This initial excitement about the potential novel HCV treatments has been somewhat dampened by a quick emergence of enzyme resistance to these agents. The opportunity for other chemical classes of HCV protease inhibitors with better resistance profile still exists. In our search for novel HCV protease inhibitors, we considered benzoxaborole as the P4 moiety, the fourth aminoacid residue from carboxyl terminus. Benzoxaboroles (core structure shown in compound in ) are a chemical class of organoboron compounds that have excellent physicochemical and biological properties. They are metabolically stable, and exhibit good water solubility. Docking studies of compound to the enzyme active site suggest that benzoxaborole moiety with suitable orientation and linkage can potentially interact with active site polar aminoacid residues: Ser122, Arg123, Arg155 and Asp168 of HCV NS3/4A serine protease. These additional interactions may provide better resistance profile than the known inhibitors that do not have. Syntheses of the target compound and its analogs as well as their biological evaluations are reported herein.