Disclosed is a hybrid molecule comprising a first part, a second part, and a third part connected by covalent bonds,(a) wherein said first part comprises a portion of the binding domain of a cell-binding polypeptide ligand effective to cause said hybrid protein to bind to a cell of an animal;(b) wherein said second part comprises a portion of a translocation domain of naturally occurring protein which translocates said third part across the cytoplasmic membrane into the cytosol of the cell; and(c) wherein said third part comprises a chemical entity to be introduced into the cell, wherein each of said first part and said third part is non-native with respect to said naturally occurring protein, and further wherein said covalent bond connecting said second part and said third part is a cleavable bond, provided that when said second part comprises a portion of a translocation domain of Pseudomonas exotoxin, said third part is not a polypeptide.