Provided are conjugates between p97 (melanotransferrin) and polynucleotides such as small interfering RNA (siRNA) molecules, and related compositions and methods of use thereof, for instance, to facilitate delivery of polynucleotides such as siRNA molecules across the blood-brain barrier (BBB) and/or improve their tissue penetration in CNS and/or peripheral tissues, and thereby treat and/or diagnose various diseases, including those having a central nervous system (CNS) component.
