ERBB2 and breast cancer: At around the same time as the first small molecule PROTACs, in 2008, nanoparticles emerged as tools for extracellular protein degradation with the development of gold nanoparticles decorated with anti‐Her2 antibodies that induced the degradation of the HER2 receptor.[36] This nanoparticle system facilitated the internalization and subsequent degradation of HER2 receptor in a human breast cancer cell line (SK‐BR‐3).[36] HER2 degradation was found to be dependent on the nanoparticle size, with 40–60 nm particles demonstrating the highest efficiency.