Discovery, Optimization, and Biological Evaluation of Arylpyridones as Cbl-b Inhibitors

Casitas B-lymphoma proto-oncogene-b (Cbl-b), a member of the Cbl family of RING finger E3 ubiquitin ligases, has been demonstrated to play a central role in regulating effector T-cell function. Multiple studies using gene-targeting approaches have provided direct evidence that Cbl-b negatively regulates T, B, and NK cell activation via a ubiquitin-mediated protein modulation. Thus, inhibition of Cbl-b ligase activity can lead to immune activation and has therapeutic potential in immuno-oncology. Herein, we describe the discovery and optimization of an arylpyridone series as Cbl-b inhibitors by structure-based drug discovery to afford compound 31. This compound binds to Cbl-b with an IC50 value of 30 nM and induces IL-2 production in T-cells with an EC50 value of 230 nM. Compound 31 also shows robust intracellular target engagement demonstrated through inhibition of Cbl-b autoubiquitination, inhibition of ubiquitin transfer to ZAP70, and the cellular modulation of phosphorylation of a downstream signal within the TCR axis.

Four-Selective Pyridine Alkylation via Wittig Olefination of Dearomatized Pyridylphosphonium Ylides

Methods to synthesize alkylated pyridines are valuable because these structures are prevalent in pharmaceuticals and agrochemicals. We have developed a distinct approach to construct 4-alkylpyridines using dearomatized pyridylphosphonium ylide intermediates in a Wittig olefination-rearomatization sequence. Pyridine N-activation is key to this strategy, and N-triazinylpyridinium salts enable coupling between a wide variety of substituted pyridines and aldehydes. The alkylation protocol is viable for late-stage functionalization, including methylation of pyridine-containing drugs. This approach represents an alternative to metal-catalyzed sp² -sp³ cross-coupling reactions and Minisci-type processes.

Site-Selective Switching Strategies to Functionalize Polyazines

Many drug fragments and therapeutic compounds contain multiple pyridines and diazines. Developing site-selective reactions where specific C-H bonds can be transformed in polyazine structures would enable rapid access to valuable derivatives. We present a study that addresses this challenge by selectively installing a phosphonium ion as a versatile functional handle. Inherent factors that control site-selectivity are described along with mechanistically driven approaches for site-selective switching, where the C-+PPh3 group can be predictably installed at other positions in the polyazine system. Simple protocols, readily available reagents, and application to complex drug-like molecules make this approach appealing to medicinal chemists.