LBA and LC-MS/MS based comprehensive bioanalytical methods for FDA018, a Trop-2 targeted antibody-drug conjugate

Recently, the approval of Trop-2 targeted antibody drug conjugate (ADC) has changed the dilemma of patients with advanced triple-negative breast cancer who rely on chemotherapeutics to improve their survival. FDA018, an ADC consisting of an anti-Trop-2 antibody conjugated with a topoisomerase inhibitor SN-38 via an acid-cleavable linker, is currently being investigated in clinical trials. Based on the urgent demand to evaluate the clinical pharmacokinetics of FDA018, ligand binding assays (LBAs) for the determination of SN-38-conjugated antibody and total antibody and LC-MS/MS methods for the determination of the free SN-38, its metabolite SN-38G and total SN-38 were developed. The comparability and DAR sensitivity evaluation of the ELISA strategies for SN-38-conjugated antibody and total antibody were emphasized. The sensitivity of the LC-MS/MS method for the simultaneous determination of SN-38 and SN-38G reached 0.500 ng/mL and 0.250 ng/mL, respectively. An effective solution has been proposed for the optical instability of the cleavable linker of FDA018 during the pretreatment process of biological samples. The established bioanalytical methods were comprehensively validated and the results satisfied the acceptable criteria of ICH M10. The validated bioanalytical methods have been applied to the single-dose pharmacokinetic study of FDA018 in patients with Trop-2-positive malignant tumors successfully, and the pharmacokinetic profiles of FDA018 and its constituent components were investigated.