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.

Background: RAGE is implicated in diabetes complications, inflammation, and neurodegeneration. Results: Cytosolic domain of RAGE, ctRAGE, contains an unusual ␣-turn that mediates the mDia1-ctRAGE interaction and is required for RAGE-dependent signaling. Conclusion: A novel mechanism through which extracellular RAGE ligands regulate RAGE-mDia1 signaling is established. Significance: A novel binding interface as a target for suppression of RAGE ligand-stimulated signal transduction is identified.

Hepatitis C virus (HCV) replication is dependent on a liver-specific microRNA (miRNA), miR-122. A recent clinical trial reported that transient inhibition of miR-122 reduced viral titers in HCV infected patients. Here we set out to better understand how miR-122 inhibition influences HCV replication over time. Unexpectedly, we observed the emergence of a HCV variant that is resistant to miR-122 knockdown. Next-generation sequencing revealed that this was due to a single nucleotide change at position 28 (G28A) of the HCV genome, which falls between the two miR-122 seed-binding sites. Naturally occurring HCV isolates encoding G28A are similarly resistant to miR-122 inhibition, indicating that subtle differences in viral sequence, even outside the seed-binding site, greatly influence HCV’s miR-122 concentration requirement. Additionally, we found that HCV itself reduces miR-122’s activity in the cell, possibly through binding and sequestering miR-122. Our study provides insight into the interaction between miR-122 and HCV, including viral adaptation to reduced miR-122 bioavailability, and has implications for the development of anti-miR-122-based HCV drugs.

Authors are urged to introduce these corrections into any reprints they distribute. Secondary (abstract) services are urged to carry notice of these corrections as prominently as they carried the original abstracts.