Development of a LC-MS/MS method for the quantification of toxic payload DM1 cleaved from BT1718 in a Phase I study.

Background: BT1718 is a novel bicyclic peptide anticancer drug targeting membrane type I matrix metalloproteinase to release its toxic payload DM1. A LC-MS/MS method was validated to quantify DM1 generated from BT1718 in a Phase I/IIa clinical trial. Materials & methods: Plasma samples underwent a reduction reaction to artificially cleave BT1718 into DM1 and its bicycle components. An alkylation step was carried out to stabilize the reaction products, and plasma proteins extracted using acetonitrile. LC-MS/MS analysis utilized a C18 column and Agilent 6460 triple quadrupole mass spectrometer (Agilent, Cheshire, UK). Results: The method was fully validated over a linear range of 200-50,000 ng/ml BT1718, with overall precision ≤10% and accuracy 89-102%. Conclusion: A novel method for quantifying DM1 yielded from BT1718 has been validated and is now being utilized clinically.