CONJUGATION METHODS
This invention describes a method of conjugating a cell binding agent such as an antibody with an effector group (e.g., a cytotoxic agent) or a reporter group (e.g., a radionuclide), whereby the reporter or effector group is first reacted with a bifunctional linker and the mixture is then used without purification for the conjugation reaction with the cell binding agent. The method described in this invention is advantageous for preparation of stably-linked conjugates of cell binding agents, such as antibodies with effector or reporter groups. This conjugation method provides in high yields conjugates of high purity and homogeneity that are without inter-chain cross-linking and inactivated linker residues.
1 . A process for preparing a purified conjugate in a solution, wherein the conjugate comprises an effector or a reporter molecule linked to a cell binding agent, the process comprising the steps of:
(a) contacting the effector or the reporter molecule with a bifunctional linker reagent to covalently attach the linker to the effector or the reporter molecule and thereby prepare an unpurified first mixture comprising the effector or the reporter molecule having linkers bound thereto,
(b) conjugating a cell binding agent to the effector or the reporter molecule having linkers bound thereto by reacting the unpurified first mixture with the cell binding agent to prepare a second mixture, and,
(c) subjecting the second mixture to tangential flow filtration, dialysis, gel filtration, adsorptive chromatography, selective precipitation or a combination thereof to thereby prepare the purified conjugate.
2 - 25 . (canceled)