Provided is a method for producing an antibody-drug conjugate intermediate byaddition of acid. An acid additive is used to convert the monomethylauristatinderivative into a salt thereof to participate in the reaction. The addition ofthe acidadditive can significantly improve the yield of the final product. Inaddition, the lowprice of the acid additive greatly reduces the production cost of the finalADC product.Moreover, the method of the present invention adopts a one-step preparationprocess,in addition to a higher yield of the final product, not only reducing the costof theconsumables, labor, equipment, site, raw materials and the like in theproduction, butalso greatly reducing the production of the waste liquid, and thus reducingproductioncosts and improving production efficiency, and making the method suitable forindustrial large-scale production.
