Robust Strategy for Hit-to-Lead Discovery: NMR for SAR.

Establishing robust structure-activity relationships (SARs) is key to successful drug discovery campaigns, yet it often remains elusive due to screening and hit validation artifacts (false positives and false negatives), which frequently result in unproductive downstream expenditures of time and resources. To address this issue, we developed an integrative biophysics-driven strategy that expedites hit-to-lead discovery, mitigates false positives/negatives and common hit validation errors, and provides a robust approach to obtaining accurate binding and affinity measurements. The advantage of this method is that it vastly improves the clarity and reproducibility for affinity-driven SAR by monitoring and eliminating confounding factors. We demonstrate the ease at which high-quality micromolar binders can be generated from the initial millimolar fragment screening hits against an "undruggable" protein target, HRas.

Discovery of Novel, Orally Bioavailable ß-Amino Acid Azaindole Inhibitors of Influenza PB2.

In our efforts to develop novel small-molecule inhibitors for the treatment of influenza, we utilized molecular modeling and the X-ray crystal structure of the PB2 subunit of the influenza polymerase to optimize a series of acyclic ß-amino acid inhibitors, highlighted by compound 4. Compound 4 showed good oral exposure in both rat and mouse. More importantly, it showed strong potency versus multiple influenza-A strains, including pandemic 2009 H1N1 and avian H5N1 strains and showed a strong efficacy profile in a mouse influenza model even when treatment was initiated 48 h after infection. Compound 4 offers good oral bioavailability with great potential for the treatment of both pandemic and seasonal influenza.

Discovery of VX-509 (Decernotinib): A Potent and Selective Janus Kinase 3 Inhibitor for the Treatment of Autoimmune Diseases.

While several therapeutic options exist, the need for more effective, safe, and convenient treatment for a variety of autoimmune diseases persists. Targeting the Janus tyrosine kinases (JAKs), which play essential roles in cell signaling responses and can contribute to aberrant immune function associated with disease, has emerged as a novel and attractive approach for the development of new autoimmune disease therapies. We screened our compound library against JAK3, a key signaling kinase in immune cells, and identified multiple scaffolds showing good inhibitory activity for this kinase. A particular scaffold of interest, the 1H-pyrrolo[2,3-b]pyridine series (7-azaindoles), was selected for further optimization in part on the basis of binding affinity (Ki) as well as on the basis of cellular potency. Optimization of this chemical series led to the identification of VX-509 (decernotinib), a novel, potent, and selective JAK3 inhibitor, which demonstrates good efficacy in vivo in the rat host versus graft model (HvG). On the basis of these findings, it appears that VX-509 offers potential for the treatment of a variety of autoimmune diseases.

Discovery of a novel, first-in-class, orally bioavailable azaindole inhibitor (VX-787) of influenza PB2.

In our effort to develop agents for the treatment of influenza, a phenotypic screening approach utilizing a cell protection assay identified a series of azaindole based inhibitors of the cap-snatching function of the PB2 subunit of the influenza A viral polymerase complex. Using a bDNA viral replication assay (Wagaman, P. C., Leong, M. A., and Simmen, K. A. Development of a novel influenza A antiviral assay. J. Virol. Methods 2002, 105, 105-114) in cells as a direct measure of antiviral activity, we discovered a set of cyclohexyl carboxylic acid analogues, highlighted by VX-787 (2). Compound 2 shows strong potency versus multiple influenza A strains, including pandemic 2009 H1N1 and avian H5N1 flu strains, and shows an efficacy profile in a mouse influenza model even when treatment was administered 48 h after infection. Compound 2 represents a first-in-class, orally bioavailable, novel compound that offers potential for the treatment of both pandemic and seasonal influenza and has a distinct advantage over the current standard of care treatments including potency, efficacy, and extended treatment window.

Discovery and SAR of novel 4-thiazolyl-2-phenylaminopyrimidines as potent inhibitors of spleen tyrosine kinase (SYK).

A series of SYK inhibitors based on the phenylamino pyrimidine thiazole lead 4 were prepared and evaluated for biological activity. Lead optimization provided compounds with nanomolar K(i)'s against SYK and potent inhibition in mast cell degranulation assays.

Aza-retinoids as novel retinoid X receptor-specific agonists.

A new structurally simple series of potent lipophilic aza-retinoids RXR agonists has been developed. SAR studies for the N-alkyl-azadienoic acids described here demonstrate that the RXR activity profile is sensitive to the N-alkyl chain length. Further, we have expanded the work to include azadienoic acids, which exhibited many accessible conformations leading to a better understanding of the SAR around the series.

Inhibitors of hepatitis C virus NS3.4A protease. Part 3: P2 proline variants.

We recently described the identification of an optimized alpha-ketoamide warhead for our series of HCV NS3.4A inhibitors. We report herein a series of HCV protease inhibitors incorporating 3-alkyl-substituted prolines in P(2). These compounds show exceptional enzymatic and cellular potency given their relatively small size. The marked enhancement of activity of these 3-substituted proline derivatives relative to previously reported 4-hydroxyproline derivatives constitutes additional evidence for the importance of the S(2) binding pocket as the defining pharmacophore for inhibition of the NS3.4A enzyme.

Inhibitors of hepatitis C virus NS3.4A protease 2. Warhead SAR and optimization.

The alpha-ketoamide warhead (e.g., 15) was found to be a practical replacement for aliphatic aldehydes in a series of HCV NS3.4A protease inhibitors. Structure-activity relationships and prime side optimization are discussed.

Inhibitors of hepatitis C virus NS3.4A protease 1. Non-charged tetrapeptide variants.

Tetrapeptide-based peptidomimetic compounds have been shown to effectively inhibit the hepatitis C virus NS3.4A protease without the need of a charged functionality. An aldehyde is used as a prototype reversible electrophilic warhead. The SAR of the P1 and P2 inhibitor positions is discussed.

Retinoic acid receptor ligands based on the 6-cyclopropyl-2,4-hexadienoic acid.

A series of novel cyclopropanyl methyl hexadienoic acid retinoids was designed and prepared. These compounds exhibited either selective activity as RXR agonists or pan-agonists on one or more of each of the RAR and RXR isoforms. The most potent pan-agonist 5a (RAR's EC(50)=17-59 nM; RXR's EC(50)=6-14 nM) showed good antiproliferative properties in the in vitro cancer cell lines, ME 180 and RPMI 8226.