Metabolism, Pharmacokinetics, and Tissue Distribution of a Selective FK506-Binding Protein 12 F36V Mutant Degrader in Mice

dTAG-13 is a heterobifunctional molecule that induces proteasomal degradation of FKBP12^F36V-tagged proteins and is widely used in the dTAG system. To better understand its in vivo behavior, we investigated its metabolism in vitro and its metabolism, pharmacokinetics, and tissue distribution time-course in mice. dTAG-13 was rapidly absorbed within 40 min and distributed to most tissues (although not brain) with a half-life of 3.1 h. We identified 20 metabolites that resulted from demethylation, amide hydrolysis, O-dealkylation, ester cleavage, and hydroxylation products. No phase II metabolites were detected. Demethylation was predominant in the liver, while hydrolysis metabolites were abundant in plasma and widely distributed. Both NADPH-dependent and hydrolysis pathways contributed to its metabolism, with CYP3A playing a moderate role in dTAG-13 degradation. These findings support the suitability of dTAG-13 for short-term protein degradation studies, while its limited brain penetration and rapid clearance highlight the need for improved analogs. This study provides foundational insights into dTAG-13 disposition for rational in vivo use.

LC-MS; dTAG-13; metabolism; metabolomics; pharmacokinetics; tissue distribution.