SPRX-003

SPRX-003 is a bispecific monoclonal antibody targeting **Human Epidermal Growth Factor Receptor 2 (HER2)** and **Human Epidermal Growth Factor Receptor 3 (HER3)**. It is developed by **SparX Biopharmaceutical** (also known as SparX Therapeutics) using **Ligand Pharmaceuticals'** proprietary **Pelican Expression Technology** (formerly the Pfenex Expression Technology platform). The drug is designed to treat solid tumors by simultaneously blocking HER2 and HER3 signaling, which inhibits the formation of HER2/HER3 heterodimers and suppresses downstream oncogenic pathways such as PI3K/AKT/mTOR. This dual-targeting approach is intended to overcome resistance mechanisms often associated with HER2-monospecific therapies, such as trastuzumab, which can be bypassed by HER3-mediated signaling. SPRX-003 is part of a suite of programs (including SPRX-001 and SPRX-002) for which Ligand holds royalty interests under a licensing agreement with SparX.