Synthetic tailoring of approved drugs for new indications is often difficult, as the most appropriate targets may not be readily apparent and therefore few roadmaps exist to guide chemistry. Here, we report a multidisciplinary approach for accessing novel target and chemical space starting from an FDA-approved kinase inhibitor. Combining chemical and genetic modifier screening with computational modeling, we identify distinct kinases that strongly enhance (‘pro-targets’) or limit (‘anti-targets’) whole animal activity of the clinical kinase inhibitor sorafenib in a Drosophila medullary thyroid carcinoma (MTC) model. We demonstrate that RAF—the original intended sorafenib target—and MKNK kinases function as pharmacological liabilities due to inhibitor-induced transactivation and negative feedback, respectively. Through progressive synthetic refinement, we report a novel class of ‘Tumor Calibrated Inhibitors’ with unique polypharmacology and strongly improved therapeutic index in fly and human MTC xenograft models. This platform provides a rational approach for creating new high efficacy/low toxicity drugs.

The M APK/ E RK K inase MEK is a shared effector of the frequent cancer drivers KRAS and BRAF that has long been pursued as a drug target in oncology 1 , and more recently in immunotherapy 2 , 3 and aging 4 . However, many MEK inhibitors (MEKi) are limited due to on-target toxicities 5 – 7 and drug resistance 8 – 10 . Accordingly, a molecular understanding of the structure and function of MEK within physiological complexes could provide a template for the design of safer and more effective therapies. Here we report X-ray crystal structures of MEK bound to the scaffold KSR ( K inase S uppressor of R as) with various MEKi, including the clinical drug trametinib. The structures reveal an unexpected mode of binding in which trametinib directly engages KSR at the MEK interface. Through complexation, KSR remodels the prototypical MEKi allosteric pocket thereby impacting binding and kinetics, including drug residence time. Moreover, trametinib binds KSR-MEK but disrupts the related RAF-MEK complex through a mechanism that exploits evolutionarily conserved interface residues that distinguish these subcomplexes. Based on these insights we created trametiglue, which limits adaptive resistance to MEKi through enhanced interfacial binding. Together, our results reveal the plasticity of an interface pocket within MEK subcomplexes that has implications for the design of next generation drugs targeting the RAS pathway.

LBP is significantly related to DM status, but this relationship is complex and may interact with BMI. These results support the concept that LBP may be improved in normal weight diabetic subjects with improved glycemic control and weight loss, and that all obese LBP subjects may benefit from improved weight loss alone.

Pseudokinases play important roles in signal transduction and cellular processes similar to those of catalytically competent kinases. However, pseudokinase pharmacological tractability and conformational space accessibility are poorly understood. Pseudokinases have only recently been suggested to adopt “inactive” conformations or interact with conformation-specific kinase inhibitors (e.g., type II compounds). In this work, the heavily substituted pseudokinase STRADα, which possesses a DFG → GLR substitution in the catalytic site that permits nucleotide binding while impairing divalent cation coordination, is used as a test case to demonstrate the potential applicability of conformation-specific, type II compounds to pseudokinase pharmacology. Integrated structural modeling is employed to generate a “GLR-out” conformational ensemble. Likely interacting type II compounds are identified through virtual screening against this ensemble model. Biophysical validation of compound binding is demonstrated through protein thermal stabilization and ATP competition. Localization of a top-performing compound through surface methylation strongly suggests that STRADα can adopt the “GLR-out” conformation and interact with compounds that comply with the standard type II pharmacophore. These results suggest that, despite a loss of catalytic function, some pseudokinases, including STRADα, may retain the conformational switching properties of conventional protein kinases.