The invention describes a vitamin receptor binding drug delivery conjugate, and preparations therefor. The drug delivery conjugate consists of a vitamin receptor binding moiety, a bivalent linker (L), and a drug. The vitamin receptor binding moiety is a vitamin, or a vitamin receptor binding analog or a derivative thereof, and the drug includes analogs or derivatives thereof. The vitamin receptor binding moiety is covalently linked to the bivalent linker, and the drug, or the analog or the derivative thereof, is covalently linked to the bivalent linker, wherein the bivalent linker, where the bivalent linker (L) comprises one or more spacer linkers, releasable linkers, and heteroatom linkers. Methods and pharmaceutical compositions for eliminating pathogenic cell populations using the drug delivery conjugate are also described.
