β-LG (β-whey protein) is the main component of bovine whey protein, which is rich in source and high in thermal stability. 3HP-β-LG has been used clinically as a transvaginal anti-HPV drug for more than 7 years.

State Key Laboratory of Respiratory Disease of the First Affiliate Hospital of Guangzhou Medical University collaborated with units like Professor Yang Zifeng’s team from Guangzhou Lab, Fudan University, Institute of Biophysics, Chinese Academy of Sciences and Southern Medical University, to clarify the antiviral effect and mechanism of β-whey protein modified by 3-hydroxyphthalic anhydride against SARS-CoV-2 in vitro, which proves it to be a potential effective drug for the treatment of patients with COVID-19. Relevant essay Repurposing of a clinically used anti-HPV agent to prevent and treat SARS-CoV-2 infection as an intranasal formulation was published on the sub-journal of Nature: Signal Transduction and Targeted Therapy, IF: 18.187.

This research found that the 3HP-β-LG modified by 3-hydroxyphthalic anhydride presents an inhibitory effect on SARS-CoV-2 and SARS-CoV-2 PsV in vitro. Also, 3HP-β-LG presents an inhibitory effect on virus mutants with strong transmission and low sensitivity to neutralizing antibodies like SARS-CoV-2 B.1.1.7, B.1.351, P1, and B1.617.1. SARS-CoV-2 PsV pre-treated by 3HP-β-LG loses sensitivity to 293T/ACE2 cells. Intervention of 40 μM 3HP-β-LG 0.5 hour before infection and 1 hour after infection of 293T/ACE2 can completely inhibit SARS-CoV-2 infection. This research further clarified that 3HP-β-LG mainly affects the early stage of virus entry into cells, while unmodified β-LG has no antiviral activity against SARS-CoV-2 PsV.

After β-LG was modified by 3-hydroxyphthalic anhydride, the negative net charge on the surface is greatly increased, and the antiviral activity increases as the modification rate increases. Through AutoDock analysis, it was found that the hACE2 binding sites in the receptor binding domain (RBD) of 3HP-β-LG and SARS-CoV-2 spike protein were similar and docked with RBD. Tests have confirmed that 3HP-β-LG can bind to SARS-CoV-2 S1 protein and SARS-CoV-2 S protein RBD in a dose-dependent manner, which can inhibit the binding of SARS-CoV-2 S1 protein to 293T/ACE2 cells. It further proves that 3HP-β-LG can block the binding of SARS-CoV-2 and ACE2 through competitive inhibition. 3HP-β-LG may become a cheap and safe anti-COVID-19 drug that can be delivered through nose.