Design and synthesis of tetrahydropyridopyrimidine based Toll-Like Receptor (TLR) 7/8 dual agonists.

In a continuing effort to discover novel TLR agonists, herein we report on the discovery and structure-activity relationship of novel tetrahydropyridopyrimidine TLR 7/8 agonists. Optimization of this series towards dual agonist activity and a high clearance profile resulted in the identification of compound 52a1. Evaluation in vivo revealed an interferon stimulated response (ISG) in mice with limited systemic exposure and demonstrated the potential in antiviral treatment or as a vaccine adjuvant.

Discovery of selective 2,4-diaminoquinazoline toll-like receptor 7 (TLR 7) agonists.

The discovery of a novel series of highly potent quinazoline TLR 7/8 agonists is described. The synthesis and structure-activity relationship is presented. Structural requirements and optimization of this series toward TLR 7 selectivity afforded the potent agonist 48. Pharmacokinetic and pharmacodynamic studies highlighted 48 as an orally available endogenous interferon (IFN-α) inducer in mice.

Quantitation of pretreatment serum interferon-γ-inducible protein-10 improves the predictive value of an IL28B gene polymorphism for hepatitis C treatment response.

UNLABELLED: Polymorphisms of the IL28B gene are highly associated with sustained virological response (SVR) in patients with chronic hepatitis C treated with peginterferon and ribavirin. Quantitation of interferon-γ-inducible protein-10 (IP-10) may also differentiate antiviral response. We evaluated IP-10 levels in pretreatment serum from 115 nonresponders and 157 sustained responders in the Study of Viral Resistance to Antiviral Therapy of Chronic Hepatitis C cohort, including African American (AA) and Caucasian American (CA) patients. Mean IP-10 was lower in sustained responders compared with nonresponders (437 ± 31 vs 704 ± 44 pg/mL, P < 0.001), both in AA and CA patients. The positive predictive value of low IP-10 levels (<600 pg/mL) for SVR was 69%, whereas the negative predictive value of high IP-10 levels (>600 pg/mL) was 67%. We assessed the combination of pretreatment IP-10 levels with IL28B genotype as predictors of treatment response. The IL28B polymorphism rs12979860 was tested in 210 participants. The CC, CT, and TT genotypes were found in 30%, 49%, and 21% of patients, respectively, with corresponding SVR rates of 87%, 50%, and 39% (P < 0.0001). Serum IP-10 levels within the IL28B genotype groups provided additional information regarding the likelihood of SVR (P < 0.0001). CT carriers with low IP-10 had 64% SVR versus 24% with high IP-10. Similarly, a higher SVR rate was identified for TT and CC carriers with low versus high IP-10 (TT, 48% versus 20%; CC, 89% versus 79%). IL28B genotype and baseline IP-10 levels were additive but independent when predicting SVR in both AA and CA patients. CONCLUSION: When IL28B genotype is combined with pretreatment serum IP-10 measurement, the predictive value for discrimination between SVR and nonresponse is significantly improved, especially in non-CC genotypes. This relationship warrants further investigation to elucidate the mechanisms of antiviral response and prospective validation.

In vitro resistance profile of the hepatitis C virus NS3/4A protease inhibitor TMC435.

TMC435 is a small-molecule inhibitor of the NS3/4A serine protease of hepatitis C virus (HCV) currently in phase 2 development. The in vitro resistance profile of TMC435 was characterized by selection experiments with HCV genotype 1 replicon cells and the genotype 2a JFH-1 system. In 80% (86/109) of the sequences from genotype 1 replicon cells analyzed, a mutation at NS3 residue D168 was observed, with changes to V or A being the most frequent. Mutations at NS3 positions 43, 80, 155, and 156, alone or in combination, were also identified. A transient replicon assay confirmed the relevance of these positions for TMC435 inhibitory activity. The change in the 50% effective concentrations (EC(50)s) observed for replicons with mutations at position 168 ranged from <10-fold for those with the D168G or D168N mutation to approximately 2,000-fold for those with the D168V or D168I mutation, compared to the EC(50) for the wild type. Of the positions identified, mutations at residue Q80 had the least impact on the activity of TMC435 (<10-fold change in EC(50)s), while greater effects were observed for some replicons with mutations at positions 43, 155, and 156. TMC435 remained active against replicons with the specific mutations observed after in vitro or in vivo exposure to telaprevir or boceprevir, including most replicons with changes at positions 36, 54, and 170 (<3-fold change in EC(50)s). Replicons carrying mutations affecting the activity of TMC435 remained fully susceptible to alpha interferon and NS5A and NS5B inhibitors. Finally, combinations of TMC435 with alpha interferon and NS5B polymerase inhibitors prevented the formation of drug-resistant replicon colonies.

In vitro activity and preclinical profile of TMC435350, a potent hepatitis C virus protease inhibitor.

The hepatitis C virus (HCV) NS3/4A serine protease has been explored as a target for the inhibition of viral replication in preclinical models and in HCV-infected patients. TMC435350 is a highly specific and potent inhibitor of NS3/4A protease selected from a series of novel macrocyclic inhibitors. In biochemical assays using NS3/4A proteases of genotypes 1a and 1b, inhibition constants of 0.5 and 0.4 nM, respectively, were determined. TMC435350 inhibited HCV replication in a cellular assay (subgenomic 1b replicon) with a half-maximal effective concentration (EC(50)) of 8 nM and a selectivity index of 5,875. The compound was synergistic with alpha interferon and an NS5B inhibitor in the replicon model and additive with ribavirin. In rats, TMC435350 was extensively distributed to the liver and intestinal tract (tissue/plasma area under the concentration-time curve ratios of >35), and the absolute bioavailability was 44% after a single oral administration. Compound concentrations detected in both plasma and liver at 8 h postdosing were above the EC(99) value measured in the replicon. In conclusion, given the selective and potent in vitro anti-HCV activity, the potential for combination with other anti-HCV agents, and the favorable pharmacokinetic profile, TMC435350 has been selected for clinical development.

2,4-Diaminoquinazolines as Dual Toll-like Receptor (TLR) 7/8 Modulators for the Treatment of Hepatitis B Virus.

A novel series of 2,4-diaminoquinazolines was identified as potent dual Toll-like receptor (TLR) 7 and 8 agonists with reduced off-target activity. The stereochemistry of the amino alcohol was found to influence the TLR7/8 selectivity with the ( R) isomer resulting in selective TLR8 agonism. Lead optimization toward a dual agonist afforded ( S)-3-((2-amino-8-fluoroquinazolin-4-yl)amino)hexanol 31 as a potent analog, being structurally different from previously described dual agonists ( McGowan J. Med. Chem. 2016 , 59 , 7936 ). Pharmacokinetic and pharmacodynamic (PK/PD) studies revealed the desired high first pass profile aimed at limiting systemic cytokine activation. In vivo pharmacodynamic studies with lead compound 31 demonstrated production of cytokines consistent with TLR7/8 activation in mice and cynomolgus monkeys and ex vivo inhibition of hepatitis B virus (HBV).

Identification and Optimization of Pyrrolo[3,2-d]pyrimidine Toll-like Receptor 7 (TLR7) Selective Agonists for the Treatment of Hepatitis B.

Pyrrolo[3,2-d]pyrimidines were identified as a new series of potent and selective TLR7 agonists. Compounds were optimized for their activity and selectivity over TLR8. This presents an advantage over recently described scaffolds that have residual TLR8 activity, which may be detrimental to the tolerability of the candidate drug. Oral administration of the lead compound 54 effectively induced a transient interferon stimulated gene (ISG) response in mice and cynomolgus monkeys. We aimed for a high first pass effect, limiting cytokine induction systemically, and demonstrated the potential for the immunotherapy of viral hepatitis.

Novel Pyrimidine Toll-like Receptor 7 and 8 Dual Agonists to Treat Hepatitis B Virus.

Toll-like receptor (TLR) 7 and 8 agonists can potentially be used in the treatment of viral infections and are particularly promising for chronic hepatitis B virus (HBV) infection. An internal screening effort identified a pyrimidine Toll-like receptor 7 and 8 dual agonist. This provided a novel alternative over the previously reported adenine and pteridone type of agonists. Structure-activity relationship, lead optimization, in silico docking, pharmacokinetics, and demonstration of ex vivo and in vivo cytokine production of the lead compound are presented.

Evaluation of the anti-hepatitis C virus effect of novel potent, selective, and orally bioavailable JNK and VEGFR kinase inhibitors.

Screening of a focused library of TGF beta kinase inhibitors in the cellular HCV replicon model with luciferase read out yielded a number of low micromolar HCV inhibitors. Medicinal chemistry driven optimization resulted in the discovery of 4-[2-(5-bromo-2-fluoro-phenyl)pteridin-4-ylamino]-N-[3-(2- oxopyrrolidin-1-yl)propyl]nicotinamide 36 with a replicon EC(50) of 64nM, associated with a selective kinase inhibitory profile for human JNK kinases 2 and 3 as well as VEGFR-1, 2, and 3 kinases. Moreover, 36 showed an advantageous PK profile in mice. Experiments performed using different replicon constructs suggest that this series of kinase inhibitors might mediate their effect through the HCV non-structural protein 5A (NS5A).