A new method to measure serum drug levels to improve the safety of cancer therapies.

It is crucial that cancer patients receive the proper medication dosage. Too high of a dose can be toxic; too low of a dose will not effectively kill cancer cells. Accurate dosing requires a method to monitor drug levels and thereby guide dose adjustments. However, currently most cancer drugs do not have such a method available. To address this problem, I developed a new generalized method for drug measurement, a "modified thermal shift assay," based on observing the degree of thermal stabilization caused by drug present in the specimen binding to protein probe derived from that drug's intended target. We provided proof of concept that this method can measure the levels of the cancer drug trametinib, an inhibitor of MEK1 used to treat melanoma. However, due to the high affinity of MEK1 binding to trametinib, this initial formulation of this assay was highly sensitive but also saturated at low drug concentrations. To address this, I have modified this assay by expressing and purifying a series of mutant MEK1 proteins with reduced trametinib binding affinities. Utilization of these mutant MEK1 probes in parallel with wildtype MEK1 greatly increased the dynamic range and precision of the assay. Validation studies of this modified assay demonstrated that it displays a <12% coefficient of variation across over 5 logs, characteristics superior to current clinical drug monitoring assays. This assay only requires widely available equipment, is simple and rapid to conduct, and can be easily generalized to measure other drugs, demonstrating that this approach could provide the first generalizable method for clinical measurement of drug concentrations to guide dosing and improve the safety of a wide variety of drugs.