Latest Advances in Small Molecule TLR 7/8 Agonist Drug Research.

Toll-like receptors (TLRs) 7 and 8 play an important role in the activation of innate immune cells in mammals. These evolutionarily conserved receptors serve as important sentinels in response to infection. Activation of TLRs 7 and 8 triggers induction of a Th1 type innate immune response. The emergence of new structural and small molecule information generated in the last decade has contributed enormously to our understanding of this highly sophisticated process of innate immunity signaling. This review will focus on recent developments in the small molecule activation of TLR 7 and 8.

Design, Synthesis, and Biological Evaluation of Novel Indoles Targeting the Influenza PB2 Cap Binding Region.

In the search for novel influenza inhibitors we evaluated 7-fluoro-substituted indoles as bioisosteric replacements for the 7-azaindole scaffold of Pimodivir, a PB2 (polymerase basic protein 2) inhibitor currently in clinical development. Specifically, a 5,7-difluoroindole derivative 11a was identified as a potent and metabolically stable influenza inhibitor. 11a demonstrated a favorable oral pharmacokinetic profile and in vivo efficacy in mice. In addition, it was found that 11a was not at risk of metabolism via aldehyde oxidase, an advantage over previously described inhibitors of this class. The crystal structure of 11a bound to influenza A PB2 cap region is disclosed here and deposited to the PDB.

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.

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.

Synthesis and evaluation of novel HCV replication inhibitors.

Direct acting antiviral agents to cure hepatitis C virus (HCV) infection has emerged as the gold standard therapy. Along with protease inhibitors, nucleoside polymerase inhibitors and non-nucleoside polymerase inhibitors, the inhibition of NS5a has proved to be an effective way to treat HCV patients. Here we report on novel HCV NS5a inhibitors which were synthesized and evaluated in the HCV replicon assay. A series of inhibitors were formed by a cycloaddition reaction in parallel to establish new leads and explore the effects of unsymmetrical cap substitution. This led to the identification of several triazoles with picomolar potency in vitro against hepatitis C virus.

Versatile Multicomponent Reaction Macrocycle Synthesis Using α-Isocyano-ω-carboxylic Acids.

The direct macrocycle synthesis of α-isocyano-ω-carboxylic acids via an Ugi multicomponent reaction is introduced. This multicomponent reaction (MCR) protocol differs by being especially short, convergent, and versatile, giving access to 12-22 membered rings.

Structure-guided design of aminopyrimidine amides as potent, selective inhibitors of lymphocyte specific kinase: synthesis, structure-activity relationships, and inhibition of in vivo T cell activation.

The lymphocyte-specific kinase (Lck), a member of the Src family of cytoplasmic tyrosine kinases, is expressed in T cells and natural killer (NK) cells. Genetic evidence, including knockout mice and human mutations, demonstrates that Lck kinase activity is critical for normal T cell development, activation, and signaling. Selective inhibition of Lck is expected to offer a new therapy for the treatment of T-cell-mediated autoimmune and inflammatory disease. With the aid of X-ray structure-based analysis, aminopyrimidine amides 2 and 3 were designed from aminoquinazolines 1, which had previously been demonstrated to exhibit potent inhibition of Lck and T cell proliferation. In this report, we describe the synthesis and structure-activity relationships of a series of novel aminopyrimidine amides 3 possessing improved cellular potency and selectivity profiles relative to their aminoquinazoline predecessors 1. Orally bioavailable compound 13b inhibited the anti-CD3-induced production of interleukin-2 (IL-2) in mice in a dose-dependent manner (ED 50 = 9.4 mg/kg).

Discovery of 4-amino-5,6-biaryl-furo[2,3-d]pyrimidines as inhibitors of Lck: development of an expedient and divergent synthetic route and preliminary SAR.

4-Amino-5,6-biaryl-furo[2,3-d]pyrimidines were identified as potent non-selective inhibitors of Lck. A novel, divergent, and practical synthetic route was developed to access derivatives from bifunctional intermediates. Lead optimization was guided by X-ray crystallographic data, and preliminary SAR led to the identification of compounds with improved cellular potency and selectivity.

Discovery of novel 2,3-diarylfuro[2,3-b]pyridin-4-amines as potent and selective inhibitors of Lck: synthesis, SAR, and pharmacokinetic properties.

2,3-Diarylfuro[2,3-b]pyridine-4-amines are a novel class of potent and selective inhibitors of Lck. The discovery, synthesis, and structure activity relationships of this series of inhibitors are reported. The most promising compounds were also profiled to deduce their pharmacokinetic properties.

Discovery of aminoquinazolines as potent, orally bioavailable inhibitors of Lck: synthesis, SAR, and in vivo anti-inflammatory activity.

The lymphocyte-specific kinase (Lck) is a cytoplasmic tyrosine kinase of the Src family expressed in T cells and natural killer (NK) cells. Genetic evidence in both mice and humans demonstrates that Lck kinase activity is critical for signaling mediated by the T cell receptor (TCR), which leads to normal T cell development and activation. Selective inhibition of Lck is expected to offer a new therapy for the treatment of T-cell-mediated autoimmune and inflammatory disease. Screening of our kinase-preferred collection identified aminoquinazoline 1 as a potent, nonselective inhibitor of Lck and T cell proliferation. In this report, we describe the synthesis and structure-activity relationships of a series of novel aminoquinazolines possessing in vitro mechanism-based potency. Optimized, orally bioavailable compounds 32 and 47 exhibit anti-inflammatory activity (ED(50) of 22 and 11 mg/kg, respectively) in the anti-CD3-induced production of interleukin-2 (IL-2) in mice.

Novel 2-aminopyrimidine carbamates as potent and orally active inhibitors of Lck: synthesis, SAR, and in vivo antiinflammatory activity.

The lymphocyte-specific kinase (Lck) is a cytoplasmic tyrosine kinase of the Src family expressed in T cells and NK cells. Genetic evidence in both mice and humans demonstrates that Lck kinase activity is critical for signaling mediated by the T cell receptor (TCR), which leads to normal T cell development and activation. A small molecule inhibitor of Lck is expected to be useful in the treatment of T cell-mediated autoimmune and inflammatory disorders and/or organ transplant rejection. In this paper, we describe the synthesis, structure-activity relationships, and pharmacological characterization of 2-aminopyrimidine carbamates, a new class of compounds with potent and selective inhibition of Lck. The most promising compound of this series, 2,6-dimethylphenyl 2-((3,5-bis(methyloxy)-4-((3-(4-methyl-1-piperazinyl)propyl)oxy)phenyl)amino)-4-pyrimidinyl(2,4-bis(methyloxy)phenyl)carbamate (43) exhibits good activity when evaluated in in vitro assays and in an in vivo model of T cell activation.