XL220

XL220 is a preclinical-stage diagnostic imaging agent developed by XL-protein, targeting the B-lymphocyte antigen CD20. The molecule is a Fab fragment of a monoclonal antibody that has been modified using XL-protein's proprietary PASylation technology (Fab-PAS). PASylation involves the genetic fusion of a conformationally disordered polypeptide sequence consisting of Proline, Alanine, and Serine (PAS) to the protein, which increases its hydrodynamic volume and extends its plasma half-life. This technology serves as a biodegradable alternative to chemical PEGylation. XL220 is intended for the detection and imaging of CD20-positive B-cell malignancies in oncology.