Streptomycin/KLH is one of protein/peptide and small molecule drug conjugates (PDCs), consisting of Streptomycin (HY-B1906) and KLH. 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].