Transferrin Receptor (TfR)-targeting PDCs present another avenue for selective drug delivery by targeting the overexpressed TfR in cancer cells.111 For instance, a recently reported PDC was designed and synthesized by using N-succinimidyl-3-maleimidopropionate (SMP) as a crosslinker to connect the TfR targeting peptide analogue BP9a (CAHLHNRS) and DOX. The gene discussed is PDC; the disease is cancer.