Tuning the Reactivity of Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) Activators for Optimal in Vivo Efficacy.

Dimethyl fumarate 1 is approved for the treatment of multiple sclerosis but is also associated with off-target activation of the niacin receptor. By using a tetrazolone or triazolone bioisostere approach to the fumarate and vinyl sulfone series of Nrf2 activators, we have optimized the electrophilicity of the double bond to tune the on-target Nrf2 activation with PK properties to achieve efficacy in animal models of multiple sclerosis. The study linked highly potent, highly electrophilic molecules to low plasma stability and, subsequently, limited efficacy. By contrast, a sulfonylvinyltriazolone 17 retains on-target potency but shows much weaker electrophilic potential. As a consequence, in vivo high exposures of 17 are obtained, resulting in efficacy in the EAE model similar to that observed for DMF. 17 (R079) is Ames negative, is not cytotoxic to cells, and shows little inhibition of either the niacin receptor or a panel of off-target receptors.

Regulation of bone homeostasis by MERTK and TYRO3.

The fine equilibrium of bone homeostasis is maintained by bone-forming osteoblasts and bone-resorbing osteoclasts. Here, we show that TAM receptors MERTK and TYRO3 exert reciprocal effects in osteoblast biology: Osteoblast-targeted deletion of MERTK promotes increased bone mass in healthy mice and mice with cancer-induced bone loss, whereas knockout of TYRO3 in osteoblasts shows the opposite phenotype. Functionally, the interaction of MERTK with its ligand PROS1 negatively regulates osteoblast differentiation via inducing the VAV2-RHOA-ROCK axis leading to increased cell contractility and motility while TYRO3 antagonizes this effect. Consequently, pharmacologic MERTK blockade by the small molecule inhibitor R992 increases osteoblast numbers and bone formation in mice. Furthermore, R992 counteracts cancer-induced bone loss, reduces bone metastasis and prolongs survival in preclinical models of multiple myeloma, breast- and lung cancer. In summary, MERTK and TYRO3 represent potent regulators of bone homeostasis with cell-type specific functions and MERTK blockade represents an osteoanabolic therapy with implications in cancer and beyond.

Discovery and characterization of substituted diphenyl heterocyclic compounds as potent and selective inhibitors of hepatitis C virus replication.

A novel small-molecule inhibitor, referred to here as R706, was discovered in a high-throughput screen of chemical libraries against Huh-7-derived replicon cells carrying autonomously replicating subgenomic RNA of hepatitis C virus (HCV). R706 was highly potent in blocking HCV RNA replication as measured by real-time reverse transcription-PCR and Western blotting of R706-treated replicon cells. Structure-activity iterations of the R706 series yielded a lead compound, R803, that was more potent and highly specific for HCV replication, with no significant inhibitory activity against a panel of HCV-related positive-stranded RNA viruses. Furthermore, HCV genotype 1 replicons displayed markedly higher sensitivity to R803 treatment than a genotype 2a-derived replicon. In addition, R803 was tested by a panel of biochemical and cell-based assays for on-target and off-target activities, and the data suggested that the compound had a therapeutic window close to 100-fold, while its exact mechanism of action remained elusive. We found that R803 was more effective than alpha interferon (IFN-alpha) at blocking HCV RNA replication in the replicon model. In combination studies, R803 showed a weak synergistic effect with IFN-alpha/ribavirin but only additive effects with a protease inhibitor and an allosteric inhibitor of RNA-dependent RNA polymerase (20). We conclude that R803 and related heterocyclic compounds constitute a new class of HCV-specific inhibitors that could potentially be developed as a treatment for HCV infection.

Benzobicyclooctanes as novel inhibitors of TNF-alpha signaling.

A novel series of TNF-alpha inhibitors based on a benzobicyclooctane scaffold is reported. The compounds display good potency in inhibiting TNF-alpha induced apoptosis and NF kappa B activation. Additionally, they are selective for TNF-alpha as they do not inhibit apoptosis induced by soluble Fas ligand. The compounds described here can act as leads for future medicinal chemistry efforts and may also be useful tools for elucidating the TNF-alpha signaling pathway.