The vasodilator, hydralazine (HYZ), has been used clinically for 70 years, but its mechanism of action is still unknown. We show that HYZ covalently and irreversibly inhibits 2-aminoethanethiol dioxygenase (ADO) and explains the drugs MOA for preeclampsia. The drug binds in a bidentate fashion to the enzyme’s metal cofactor, resulting in alkylation of the histidine ligand. Mechanism-based inactivation of ADO by HYZ senesces glioblastoma cells. The results connect an old drug to its target, reveal the mechanism of its therapeutic effect, and imply that it might be repurposed and further optimized for the treatment of a deadly brain cancer.

WRN helicase is a promising target for treating cancers with microsatellite instability (MSI) due to its essential role in resolving deleterious non-canonical DNA structures that accumulate in cells with faulty mismatch repair mechanisms. Here we describe the medicinal chemistry optimization of potency, ADME, and PK properties of chemoproteomic screening hits, which resulted in identification of VVD-214/RO7589831 (Vividion/Roche), a clinical-stage, covalent allosteric inhibitor of WRN.

We designed a series of natural product-inspired molecules that bind and remodel the surface of cyclophilin A to create a binary complex with high affinity for the active, GTP bound (ON) state of RAS. The resulting tri-complex sterically blocks RAS-effector interactions to disrupt downstream signaling. Structure-guided optimization enabled the development of orally bioavailable covalent inhibitors including the investigational agents, RMC-6291 (RAS(ON) G12C-selective) and RMC-9805 (RAS(ON) G12D-selective), both of which display profound antitumor activity in preclinical models.

The presentation will discuss the design of CODON, our proprietary pan-amino-acid covalent fragment library and its ability to identify novel and induced pockets on relevant protein targets. The rich SAR generated during the screening phase enables rapid hit-to-lead progression and early confirmation of cellular target engagement.

Covalent modulation of therapeutic targets is an increasingly important modality for drug discovery, particularly after recent success with historically challenging targets like KRAS G12C. In this talk, I’ll present the work we have done to discover covalent inhibitors for two different targets, and also describe our chemical biology efforts to understand the selectivity and mechanism of actions for these inhibitors.