ED-04

**ED-04** is a highly potent small molecule topoisomerase 1 inhibitor developed as the cytotoxic payload for next-generation antibody-drug conjugates (ADCs), particularly in oncology. It is used as the payload in investigational ADCs (e.g., BL-B01D1, BL-M07D1) that target specific tumor antigens such as EGFR, HER2, and HER3. ED-04 is conjugated to antibodies via a serum-stable linker that is cleavable by cathepsin-B, facilitating release within tumor cell lysosomes and inducing genotoxic stress leading to tumor cell death. This ADC platform, which incorporates ED-04, is engineering to deliver the payload specifically to cancer cells, reducing off-target toxicity. Preclinical and early clinical studies have shown promising efficacy signals in several solid tumor types, including non-small cell lung cancer and urothelial cancer[2][3][4][6].