Propargyl-PEG4-acid is a PEG-based PROTAC linker can be used in the synthesis of BTK-IAP PROTACs Ibrutinib (HY-10997)-based PROTAC 2 and an analogue PROTAC 3. PROTAC 3 causes BTK degradation with a DC50 of 200 nM in THP-1 cells.In Vitro: BTK-IAP PROTACs act as stoichiometric degraders, resulting in degradation of BTK protein. Degradation of BTK is a result of IAP E3 ligases family recruitment.