Method of producing an immunoligand/payload conjugate

An immunoligand/payload conjugate comprising

• a) an immunoligand selected from the group consisting of:
• (i) an antibody,
• (ii) an antibody-based binding protein being a protein containing at least one antibody-derived VH, VL, or CH immunoglobulin domain,
• (iii) an antibody fragment binding to a receptor, antigen, growth factor, cytokine and/or hormone, and/or
• (iv) an antibody mimetic selected from the group consisting of DARPins, C-type lectins, A-domain proteins of S. aureus, transferrins, lipocalins, 10th type III domains of fibronectin, Kunitz domain protease inhibitors, affilins, gamma crystallin derived binders, cysteine knots or knottins, thioredoxin A scaffold based binders, nucleic acid aptamers, artificial antibodies produced by molecular imprinting of polymers, and stradobodies, and,
• b) at least one payload having a molecular weight not exceeding 2,500 Dalton, wherein the conjugate further comprises at least one linker between the payload and the immunoligand, said linker comprising a peptide motif that is a sortase recognition motif, and said linker being conjugated to the C-terminus of at least one peptide chain of the immunoligand,
• wherein either
• the immunoligand comprises a sortase recognition motif and the payload is modified with a Glyn-modification, wherein n>1, or
• the payload comprises a sortase recognition motif and the immunoligand is modified with a Glyn-modification, wherein n>1.