PEG3-O-CH2COOH (PROTAC Linker 8) is a PEG-based PROTAC linker can be used in the synthesis of SNIPERs.In Vitro: PEG3-O-CH2COOH (Compound 15b) is a PROTAC linker can be used in the synthesis of a series of SNIPER(ER)s. SNIPERs that recruit inhibitor of the apoptosis protein (IAP) ubiquitin ligases to specifically degrade targeted proteins.