Abstract: A homogeneous conjugate for targeting and treating diseased cells wherein the conjugate has a predetermined ratio of drug molecules to protein molecules that preferentially bind to such cells and a method for making such a conjugate. The method of making the conjugate comprises adding drug molecules to linker molecules in a manner that effectively results in one molecule of drug for each molecule of linker followed by the addition of the drug-linker combination to protein molecules in order to achieve the predetermined ratio of drug molecules to protein molecules.