A liposome for use in delivering a therapeutically active agent to a subject in need thereof is disclosed herein. The liposome comprises: a) at least one bilayer-forming lipid; b) a polymeric compound having the general formula I: (I) wherein m, n, L, X, Y, and Z are as defined herein; and c) a therapeutically active agent, incorporated in the liposome and/or on a surface of the liposome.