XL250

XL250 is a preclinical-stage therapeutic candidate developed by XL-protein for the treatment of HER2-positive cancers. The molecule utilizes XL-protein's proprietary PASylation technology, which involves the genetic fusion of a conformationally disordered polypeptide sequence consisting of Proline, Alanine, and Serine (PAS) to a HER2-targeting moiety. This modification increases the hydrodynamic volume of the drug, effectively reducing renal filtration and extending its plasma half-life. XL250 is characterized as either a PASylated Fab fragment or an antibody-drug conjugate (ADC), designed to provide potent anti-tumor activity with improved pharmacokinetic properties compared to standard HER2-targeted therapies.