The present invention relates to method for connecting a protein and a drug to a protein drug conjugate, wherein the drug is linked to the protein through a specific branched linker, said branched linker comprises a peptide chain and is derived from o-hydroxy p-amino benzylic alcohol, wherein the peptide chain is connected to the phenyl ring via the p-amino group, the drug is connected to the phenyl ring via the benzylic alcohol moiety, and the protein is connected to the phenyl ring via the o-hydroxy group； further to a process for the preparation of said protein-drug-conjugates via various intermediates, to the pharmaceutical use of such protein drug conjugates, such as methods of controlling the growth of undesirable cells, to pharmaceutical compositions comprising such protein drug conjugates, and to intermediates of the preparation of the protein drug conjugates.
