A Fully Automated LC–MS/MS Method for Therapeutic Drug Monitoring of Oral Tyrosine Kinase Inhibitors: Enabling Clinical Reporting to Support Decision-Making in Outpatient Practice

Introduction: Oral tyrosine kinase inhibitors show substantial interpatient pharmacokinetic variability, and dosing carries the risk of under- or overexposure. Although therapeutic drug monitoring (TDM) can optimize dosing, its implementation in oncology requires accurate, rapid, and adaptable quantification. Methods: We developed a fully automated liquid chromatography–tandem mass spectrometry method using the CLAM-2030 system to simultaneously quantify abemaciclib, axitinib, brigatinib, cabozantinib, imatinib, lenvatinib, lorlatinib, olaparib, osimertinib, palbociclib, pazopanib, regorafenib (and metabolites), and sunitinib (and metabolite) in human plasma. Validation followed Food and Drug Administration bioanalytical guidance and assessed selectivity, linearity, accuracy, precision, matrix effects, stability, and carryover. To assess assay adaptability, an alternative panel excluding palbociclib and olaparib but including capivasertib and fruquintinib, was also validated under the same conditions. To assess the feasibility for routine TDM implementation, we prospectively collected clinical samples from 65 patients and evaluated the turnaround time (TAT) from blood sampling to result reporting. Results: All analytes met the criteria for accuracy and precision with acceptable selectivity and matrix effects. Carryover was within the limits for most analytes and controlled by blank injections for others. Validation outcomes for the alternative panel were comparable. Most analytes remained stable for 28 days, within ±15% accuracy. The median TAT was 50 minutes (range: 14–156 minutes), and 97% of results were reported within 90 minutes. Conclusions: This fully automated, high-throughput liquid chromatography–tandem mass spectrometry platform enables rapid and reliable quantification of multiple tyrosine kinase inhibitors with a clinically relevant TAT. Its flexibility in incorporating new agents overcomes an important barrier to implementing TDM in oncology, warranting broader integration into routine practice.