HDP-104

**HDP-104** is an antibody-drug conjugate (ADC) developed using Heidelberg Pharma's proprietary ATAC (Amanitin-based Antibody Targeted Cancer) technology, featuring amanitin as the payload toxin that inhibits RNA polymerase II to block mRNA synthesis and induce cancer cell death. It targets the guanylate cyclase C (GC-C) receptor, a tumor antigen overexpressed in gastrointestinal cancers, enabling selective delivery of the cytotoxic payload to tumor cells while minimizing off-target effects.[1][9] Initially developed by Heidelberg Pharma AG, it has advanced through preclinical development for gastrointestinal neoplasms, including colorectal cancer, with no clinical trials reported as of the latest updates.[1][9]