Researchers published a new chemigenetic biosensor, HaloRasAR, that tracks endogenous Ras activity in living cells during drug research. The study in Nature Chemical Biology reports a live-cell imaging approach designed to reveal where and when Ras switches are active, including under pharmacological perturbation. By focusing on Ras activity rather than static proxy readouts, the platform is positioned to improve mechanism-of-action mapping for Ras-pathway drugs and combination strategies. Ras is a central signaling node in many cancers; translating activity measurement into high-content screening can help de-risk target engagement. The biosensor’s chemigenetic design is intended to work in native cellular contexts, potentially enabling researchers to interrogate drug effects with better spatiotemporal resolution than conventional endpoints.