Mitoxantrone modulates a glycosaminoglycan-spike complex to inhibit SARS-CoV-2 infection (preprint)

Spike-mediated entry of SARS-CoV-2 into human airway epithelial cells is an attractive therapeutic target for COVID-19. In addition to protein receptors, the SARS-CoV-2 spike (S) protein also interacts with heparan sulfate, a negatively charged glycosaminoglycan (GAG) attached to certain membrane proteins on the cell surface. This interaction facilitates the engagement of spike with a downstream receptor to promote viral entry. Here, we show that Mitoxantrone, an FDA-approved topoisomerase inhibitor, targets a spike-GAG complex to compromise the fusogenic function of spike in viral entry. As a single agent, Mitoxantrone inhibits the infection of an authentic SARS-CoV-2 strain in a cell-based model and in human lung EpiAirway 3D tissues. Gene expression profiling supports the plasma membrane as a major target of Mitoxantrone but also underscores an undesired activity targeting nucleosome dynamics. We propose that Mitoxantrone analogs bearing similar GAG-binding activities but with reduced affinity for DNA topoisomerase may offer an alternative therapy to overcome breakthrough infections in the post-vaccine era.

Targeting heparan sulfate proteoglycan-assisted endocytosis as a COVID-19 therapeutic option (preprint)

Drugs capable of blocking the infectious cycle of the coronavirus SARS-CoV-2 are urgently needed to tackle the ongoing COVID-19 pandemic. To this end, the cell entry of SARS-CoV-2, initiated by the binding of the viral Spike (S) protein to human ACE2, has emerged as an attractive drug repurposing target. Here we use murine leukemia viruses pseudotyped with Spike from SARS-CoV or SARS-CoV-2 to demonstrate that ACE2-mediated coronavirus entry can be mitigated by heparin, a heparan sulfate-related glycan, or by genetic ablation of biosynthetic enzymes for the cell surface heparan sulfate proteoglycans (HSPGs). A drug repurposing screen targeting HSPG-dependent endocytosis identifies pharmacologically active endocytosis inhibitors that also abrogate coronavirus cell entry. Among them, Mitoxantrone (EC50=~10 nM) targets HSPGs directly, whereas Sunitinib and BNTX disrupt the actin network to impair HSPG-assisted viral entry. Gene expression profiling suggests potential combination regimens that optimally target HSPG-dependent viral entry. Altogether, our study establishes HSPGs as an assisting factor for ACE2 in endocytosis-mediated coronavirus entry and identifies drugs that can be repurposed to target this important stage in the viral life cycle.