Novel Carboxamide-Based Allosteric MEK Inhibitors: Discovery and Optimization Efforts toward XL518 (GDC-0973)Kenneth D. Rice, Naing Aay, Neel K. Anand et al.|ACS Medicinal Chemistry Letters|2012 The ERK/MAP kinase cascade is a key mechanism subject to dysregulation in cancer and is constitutively activated or highly upregulated in many tumor types. Mutations associated with upstream pathway components RAS and Raf occur frequently and contribute to the oncogenic phenotype through activation of MEK and then ERK. Inhibitors of MEK have been shown to effectively block upregulated ERK/MAPK signaling in a range of cancer cell lines and have further demonstrated early evidence of efficacy in the clinic for the treatment of cancer. Guided by structural insight, a strategy aimed at the identification of an optimal diphenylamine-based MEK inhibitor with an improved metabolism and safety profile versus PD-0325901 led to the discovery of development candidate 1-({3,4-difluoro-2-[(2-fluoro-4-iodophenyl)amino]phenyl}carbonyl)-3-[(2S)-piperidin-2-yl]azetidin-3-ol (XL518, GDC-0973) (1). XL518 exhibits robust in vitro and in vivo potency and efficacy in preclinical models with sustained duration of action and is currently in early stage clinical trials.
Discovery of XL413, a potent and selective CDC7 inhibitorElena S. Koltun, Amy Lew Tsuhako, David S. Brown et al.|Bioorganic & Medicinal Chemistry Letters|2012 Discovery of XL888: A novel tropane-derived small molecule inhibitor of HSP90Joerg Bussenius, Charles M. Blazey, Naing Aay et al.|Bioorganic & Medicinal Chemistry Letters|2012 Discovery of a Novel Class of Highly Potent, Selective, ATP-Competitive, and Orally Bioavailable Inhibitors of the Mammalian Target of Rapamycin (mTOR)Craig S. Takeuchi, Byung Gyu Kim, Charles M. Blazey et al.|Journal of Medicinal Chemistry|2013 A series of novel, highly potent, selective, and ATP-competitive mammalian target of rapamycin (mTOR) inhibitors based on a benzoxazepine scaffold have been identified. Lead optimization resulted in the discovery of inhibitors with low nanomolar activity and greater than 1000-fold selectivity over the closely related PI3K kinases. Compound 28 (XL388) inhibited cellular phosphorylation of mTOR complex 1 (p-p70S6K, pS6, and p-4E-BP1) and mTOR complex 2 (pAKT (S473)) substrates. Furthermore, this compound displayed good pharmacokinetics and oral exposure in multiple species with moderate bioavailability. Oral administration of compound 28 to athymic nude mice implanted with human tumor xenografts afforded significant and dose-dependent antitumor activity.
Discovery of Daraxonrasib (RMC-6236), a Potent and Orally Bioavailable RAS(ON) Multi-selective, Noncovalent Tri-complex Inhibitor for the Treatment of Patients with Multiple RAS-Addicted CancersJames Cregg, Anne Edwards, Stephanie Chang et al.|Journal of Medicinal Chemistry|2025 Oncogenic RAS mutations are among the most common in human cancers. To target the active, GTP-bound state of RAS(ON) directly, we employed an innovative tri-complex inhibitor (TCI) modality. Formation of a complex with an intracellular chaperone protein CypA, an inhibitor, and a target protein RAS blocks effector binding, inhibiting downstream RAS signaling and tumor cell proliferation. Herein, we describe the structure-guided SAR journey that led to the discovery of daraxonrasib (RMC-6236), a noncovalent, potent tri-complex inhibitor of multiple RAS mutant and wild-type (WT) variants. This orally bioavailable bRo5 macrocyclic molecule occupies a unique composite binding pocket comprising CypA and SWI/SWII regions of RAS(ON). To achieve broad-spectrum RAS isoform activity, we deployed an SAR campaign that focused on interactions with residues conserved between mutants and WT RAS isoforms. Concurrent optimization of potency and drug-like properties led to the discovery of daraxonrasib (RMC-6236), currently in clinical evaluation in RAS mutant advanced solid tumors (NCT05379985; NCT06040541; NCT06162221; NCT06445062; NCT06128551).