Described herein protein drug conjugates and compositions thereof that are useful, for example, for the target-specific delivery of drugs to cells. By administering these compounds, compositions, and conjugates as described herein to specific target cells, side-effects due to non-specific binding phenomena, for example, to non-target cells are reduced. In certain embodiments, compounds, compositions, and conjugates are provided, which include hydrophilic residues in linker-payloads and protein conjugates thereof.
