Endolysosomal targeting conjugates for improved delivery of cargo molecules to the endolysosomal compartment of target cells

An endolysosomal targeting conjugate, comprising:

• a targeting component comprising an antibody or antibody fragment fused directly or indirectly to a cargo component;
• wherein said antibody or antibody fragment binds to HER2, and
• wherein said antibody or antibody fragment comprises a heavy chain comprising the CDRs of the heavy chain of pertuzumab and a light chain comprising the CDRs of the light chain chain of pertuzumab, wherein either (a) CDR2 of the heavy chain is modified by replacement of (i) serine at position 55 with histidine and (ii) glycine at position 57 with glutamic acid or (b) CDR3 of the heavy chain is modified by replacement of serine at position 103 with histidine and CDR2 of the light chain is modified by replacement of tyrosine at position 55 with histidine, wherein said positions are defined with respect to the positions in pertuzumab.