Enrofloxacin/BSA is one of protein/peptide and small molecule drug conjugates (PDCs), consisting of Enrofloxacin (HY-B0502) and BSA. PCDs are promising targeted therapeutics with better cell permeability and drug selectivity than antibody-drug conjugates (ADCs). PDCs have been widely used in research on cancer, COVID-19, and metabolic diseases^[1].