A clinically used anti-human papilloma virus agent (3-hydroxyphthalic anhydride-modified bovine β-lactoglobulin) has a potential for topical application to prevent sexual transmission of monkeypox virus.

A global outbreak of monkeypox (mpox) caused by the mpox virus (MPXV) has posed a serious threat to public health worldwide, thus calling for the urgent development of antivirals and vaccines to curb its further spread. In this study, we screened 41 anhydride-modified proteins and found that 3-hydroxyphthalic anhydride-modified β-lactoglobulin (3HP-β-LG), a clinically used anti-HPV agent, was highly effective in inhibiting infection of vaccinia virus Tiantan strain (VACV-VTT) and MPXV. Mechanistic studies demonstrated that 3HP-β-LG bound to the virus, not the host cell, by targeting the early stage of virus entry, possibly through the interaction between the amino acids with negatively charges in 3HP-β-LG and the key amino acids with positive charges in the target region of A29L, a key surface protein of MPXV. A synergistic effect was observed when 3HP-β-LG was combined with tecovirimat, a small-molecule antiviral drug approved by the United States Food and Drug Administration and the European Medicine Agency for the treatment of smallpox and mpox. Because of its clinically proven safety and stability, 3HP-β-LG shows promise for further development as a prophylactic agent to prevent the sexual transmission of MPXV.