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BOC Sciences offers customized services for the study of PROTAC metabolites. With a comprehensive PROTAC in vitro analysis platform, our expert team supports in vitro metabolism assessment of PROTAC to provide solutions for designing PROTAC molecules with favorable pharmacokinetic properties and to accelerate our clients' PROTAC development.
PROTAC molecules have a unique structure. They consist of three key parts: one side contains a ligand targeting the protein of interest (POI); the other side contains a ligand for an E3 ligase; and in the middle is a linker connecting these two ligands. This special structure gives it distinctive physicochemical properties and metabolism characteristics different from traditional small-molecule drugs. The type of E3 ligase, stability of the POI ligand, length of the linker, connection site, and flexibility changes all affect PROTAC metabolism.
The understanding of PROTAC metabolism is a crucial aspect of drug development to ensure their safety and efficacy. BOC Sciences investigate these pathways during the early stages of drug development to assess how PROTACs are handled in vitro and to optimize their therapeutic potential.
PROTAC metabolic reactions include hydroxylation, amide hydrolysis, O-dealkylation on its ligand portion, and hydroxylation, N-dealkylation, amide hydrolysis on its linker portion, respectively. If the linker is PEG, there will also be a significant O-dealkylation reaction. The enzymes involved in PROTAC metabolism mainly include Phase I metabolism enzymes (CYP enzymes) and Phase II metabolism enzymes (e.g., uridine diphosphate-glucuronosyltransferases, UGTs and sulfotransferases, SULTs). For PROTACs containing VHL ligands, aldehyde oxidase (hAOX) participates in metabolism, catalyzing hydroxylation in its thiazole ring.
In PROTAC molecules, the linker is the most susceptible to metabolic reactions, with the main metabolic site being the connection between the linker and the ligand. The length, connection site, and rigidity/flexibility changes of the linker can influence the overall molecule's metabolic stability.
For most PROTACs, as the linker length increases, the metabolic stability of the molecule decreases. Shorter linkers may have greater steric hindrance, preventing PROTAC from entering the catalytic site of metabolic enzymes.
Studies show that when the POI ligand and E3 ligase ligand remain constant, PROTACs linked with different linkers, such as piperazine or triazole linkers, have longer half-lives compared to straight-chain linkers. Introducing rigid structures into the linker is a favorable strategy to increase metabolic stability, such as optimizing flexible linear linkers into rigid cyclic linkers like piperidine and piperazine.
PROTAC, as a new chemical entity, cannot have its metabolic characteristics predicted based on the metabolic features of its individual components. Therefore, a comprehensive study of its overall metabolism is required. With our extensive PROTAC development and analysis platform, BOC Sciences provides in vitro PROTAC metabolism studies and submits experimental data on metabolite identification to accelerate the development of PROTACs towards clinical stages.
* PROTAC® is a registered trademark of Arvinas Operations, Inc., and is used under license.
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