Tachyon Therapeutics, Inc. and AbCellera announced a collaboration to facilitate the discovery and development of a therapeutic antibody targeting LEFTY1, a member of the transforming growth factor ß (TGF-ß) superfamily and validated extracellular drug target expressed in advanced cancers. Under the terms of the agreement, AbCellera is eligible to receive milestone payments and royalties on products that are derived from its antibody discovery platform. In addition, AbCellera has the option to invest in preclinical and clinical development in exchange for an increased share of product sales. Members of the TGF-ß superfamily control numerous cellular functions, including proliferation, apoptosis, differentiation, epithelial-mesenchymal transition, adhesion, and migration. Because of their ubiquitous and regulatory roles in both normal and cancer cell biology, TGF-ß superfamily members, such as LEFTY1 are highly sought after, yet challenging drug targets. Research led by Tachyon’s scientific founder, Michael F. Clarke, Ph.D., who was the first to identify and characterize cancer stem cells in solid tumors, revealed that LEFTY1 suppresses NODAL/SMAD2 and BMP7/SMAD5 pathways to promote long-term proliferation of normal and malignant mammary epithelial cells. As a secreted extracellular protein, LEFTY1 represents an important target to control SMAD-dependent signals that promote the long-term growth and self-renewal of cancer stem cells.