Leukotriene B4-d5 (LTB4-d5) is deuterium labeled Leukotriene B4. Leukotriene B4 (LTB4) is known as one of the most potent chemoattractants and activators of leukocytes and is involved in inflammatory diseases. Leukotriene B4 is also an alkyl chain-based PROTAC linker that can be used in the synthesis of PROTACs[1][2][3][4].