The pan-RAF-MEK non degrading molecular glue NST-628 is a potent and brain penetrant inhibitor of the RAS-MAPK pathway with activity across diverse RAS- and RAF-driven cancers

Alterations in the RAS-MAPK signaling cascade are common across multiple solid tumor types and is a driver for many cancers. NST-628 is a potent pan-RAF-MEK molecular glue that prevents phosphorylation and activation of MEK by RAF, overcoming the limitations of traditional RAS-MAPK inhibitors and leading to deep durable inhibition of the pathway. Cellular, biochemical, and structural analysis of RAF-MEK complexes show that NST-628 engages all isoforms of RAFand prevents the formation of BRAF-CRAF heterodimers, a differentiated mechanism from all current RAF inhibitors. With a potent and durable inhibition of the RAF-MEK signaling complex as well as high intrinsic permeability into the brain, NST-628 demonstrates broad efficacy in cellular and patient-derived tumor models harboring diverse MAPK pathway alterations, including orthotopic intracranial models. Given its functional and pharmacokinetic mechanisms that are differentiated from previous therapies , NST-628 is positioned to make an impact clinically in an areas of unmet patient need.

Monitoring GAPDH activity and inhibition with cysteine-reactive chemical probes

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a central enzyme in glycolysis that regulates the Warburg effect in cancer cells. In addition to its role in metabolism, GAPDH is also implicated in diverse cellular processes, including transcription and apoptosis. Dysregulated GAPDH activity is associated with a variety of pathologies, and GAPDH inhibitors have demonstrated therapeutic potential as anticancer and immunomodulatory agents. Given the critical role of GAPDH in pathophysiology, it is important to have access to tools that enable rapid monitoring of GAPDH activity and inhibition within a complex biological system. Here, we report an electrophilic peptide-based probe, SEC1, which covalently modifies the active-site cysteine, C152, of GAPDH to directly report on GAPDH activity within a proteome. We demonstrate the utility of SEC1 to assess changes in GAPDH activity in response to oncogenic transformation, reactive oxygen species (ROS) and small-molecule GAPDH inhibitors, including Koningic acid (KA). We then further evaluated KA, to determine the detailed mechanism of inhibition. Our mechanistic studies confirm that KA is a highly effective irreversible inhibitor of GAPDH, which acts through a NAD⁺-uncompetitive and G3P-competitive mechanism. Proteome-wide evaluation of the cysteine targets of KA demonstrated high selectivity for the active-site cysteine of GAPDH over other reactive cysteines within the proteome. Lastly, the therapeutic potential of KA was investigated in an autoimmune model, where treatment with KA resulted in decreased cytokine production by Th1 effector cells. Together, these studies describe methods to evaluate GAPDH activity and inhibition within a proteome, and report on the high potency and selectivity of KA as an irreversible inhibitor of GAPDH.

Cysteine-reactive chemical probes can covalently modify the active-site cysteine of GAPDH.

The Discovery of Two Novel Classes of 5,5-Bicyclic Nucleoside-Derived PRMT5 Inhibitors for the Treatment of Cancer

Protein arginine methyltransferase 5 (PRMT5) is a type II arginine methyltransferase that catalyzes the post-translational symmetric dimethylation of protein substrates. PRMT5 plays a critical role in regulating biological processes including transcription, cell cycle progression, RNA splicing, and DNA repair. As such, dysregulation of PRMT5 activity is implicated in the development and progression of multiple cancers and is a target of growing clinical interest. Described herein are the structure-based drug designs, robust synthetic efforts, and lead optimization strategies toward the identification of two novel 5,5-fused bicyclic nucleoside-derived classes of potent and efficacious PRMT5 inhibitors. Utilization of compound docking and strain energy calculations inspired novel designs, and the development of flexible synthetic approaches enabled access to complex chemotypes with five contiguous stereocenters. Additional efforts in balancing bioavailability, solubility, potency, and CYP3A4 inhibition led to the identification of diverse lead compounds with favorable profiles, promising in vivo activity, and low human dose projections.

Reaction coupling between wild-type and disease-associated mutant EZH2

EZH2 and EZH1 are protein methyltransferases (PMTs) responsible for histone H3, lysine 27 (H3K27) methylation. Trimethylation of H3K27 (H3K27me3) is a hallmark of many cancers, including non-Hodgkin lymphoma (NHL). Heterozygous EZH2 point mutations at Tyr641, Ala677, and Ala687 have been observed in NHL. The Tyr641 mutations enhance activity on H3K27me2 but have weak or no activity on unmethylated H3K27, whereas the Ala677 and Ala687 mutations use substrates of all methylation states effectively. It has been proposed that enzymatic coupling of the wild-type and mutant enzymes leads to the oncogenic H3K27me3 mark in mutant-bearing NHL. We show that coupling with the wild-type enzyme is needed to achieve H3K27me3 for several mutants, but that others are capable of achieving H3K27me3 on their own. All forms of PRC2 (wild-type and mutants) display kinetic signatures that are consistent with a distributive mechanism of catalysis.