L18I is a PROTAC (Proteolysis Targeting Chimera) that targets Btk to mitigate inflammation in autoimmune diseases. The components of L18I include the PROTAC target protein ligand IBT6A, the PROTAC linker Propargyl-PEG3-alcohol, and the E3 ubiquitin ligase ligand Lenalidomide-Br. Notably, the active control for the target protein ligand is IBT6A-CO-ethyne, while the conjugate of the E3 ubiquitin ligase ligand with the linker is Lenalidomide-C3-PEG3-N3.