Last week marked a major milestone in small-molecule drug discovery with the first FDA approval of a proteolysis targeting chimera (PROTAC). After a modest but successful phase 3 clinical trial demonstrated a 2.9 month improvement in median progression free survival¹ for a type of advanced breast cancer¹, the FDA has approved Veppanu (vepdegestrant), co-developed by Arvinas and Pfizer, as the first PROTAC protein degrader therapy². So what is a PROTAC?