A conjugate of formula A-L-P, in which: A represents a glycosylated/galactosylated peptide that binds to a cell-surface receptor, L represents a bifunctional linker, which does not comprise a naturally occurring amino acid and is covalently bonded to A and P in a regiospecific manner, and P represents a monomer, homopolymer or heteropolymer comprising at least one nucleotide or an analogue thereof, which inhibits the intracellular biosynthesis of nucleotides or nucleic acids in a sequence-independent manner, wherein either or both of the covalent bond between A and L and the covalent bond between L and P can be cleaved intracellularly; a composition comprising such a conjugate; and a method of inhibiting abnormal cellular proliferation in a mammal; and a method of inhibiting replication of a virus in a mammal.