Beyond the standard 80 mg: Exposure-guided and equity-oriented precision dosing of Osimertinib in EGFR-mutant NSCLC

BackgroundOsimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), has become foundational therapy across the EGFR-mutant non-small cell lung cancer (NSCLC) continuum, including first-line metastatic disease, unresectable stage III consolidation, and adjuvant therapy after resection. Yet routine clinical use still assumes a uniform fixed dose of 80 mg once daily, despite broad pharmacokinetic (PK) variability, substantial toxicity-mediated dose interruptions, and persistent uncertainty about an exposure-defined therapeutic window-particularly in India, where competing risks, polypharmacy, and affordability pressures shape adherence and persistence.ObjectiveThis narrative review advances the thesis that Osimertinib should be reframed not only as a fixed-dose targeted drug but as a compelling candidate for exposure-guided precision dosing-leveraging therapeutic drug monitoring (TDM), exposure-response evidence, and pharmacometric modeling to improve tolerability, continuity, and equity of access.Evidence synthesisClinical development and regulatory labeling provide convergent signals of an efficacy plateau across a wide dose range and stronger concentration dependance for select toxicities (rash, diarrhea, QTc prolongation), consistent with the broader "flat efficacy-steep toxicity" pattern observed with many targeted agents. Population PK (PopPK) analyses and real-world cohorts further highlight interpatient exposure spread, proposed toxicity thresholds (notably a candidate toxic limit of 259 ng/mL, derived from a single real-world cohort and requiring external validation), and operational feasibility of plasma- or microsampling-based assays. However, existing datasets remain heterogeneous, and no globally accepted therapeutic range exists.ConclusionsOsimertinib precision dosing is an emerging, plausible, and equity-relevant paradigm-especially in India and other resource-constrained settings-but requires prospective, locally anchored therapeutic window studies, pragmatic TDM workflows, and model-informed dose adaptation trials before routine implementation. Pending such evidence, exposure-guided dosing should be regarded as investigational rather than standard care.