Post-infection treatment with the E protein inhibitor BIT225 reduces disease severity and increases survival of K18-hACE2 transgenic mice infected with a lethal dose of SARS-CoV-2

The Coronavirus envelope (E) protein is a small structural protein with ion channel activity that plays an important role in virus assembly, budding, immunopathogenesis and disease severity. The viroporin E is also located in Golgi and ER membranes of infected cells and is associated with inflammasome activation and immune dysregulation. Here we evaluated in vitro antiviral activity, mechanism of action and in vivo efficacy of BIT225 for the treatment of SARS-CoV-2 infection. BIT225 showed broad-spectrum direct-acting antiviral activity against SARS-CoV-2 in Calu3 and Vero cells with similar potency across 6 different virus strains. BIT225 inhibited ion channel activity of E protein but did not inhibit endogenous currents or calcium-induced ion channel activity of TMEM16A in Xenopus oocytes. BIT225 administered by oral gavage for 12 days starting 12 hours before infection completely prevented body weight loss and mortality in SARS-CoV-2 infected K18 mice (100% survival, n = 12), while all vehicle-dosed animals reached a mortality endpoint by Day 9 across two studies (n = 12). When treatment started at 24 hours after infection, body weight loss, and mortality were also prevented (100% survival, n = 5), while 4 of 5 mice maintained and increased body weight and survived when treatment started 48 hours after infection. Treatment efficacy was dependent on BIT225 dose and was associated with significant reductions in lung viral load (3.5 log(10)), virus titer (4000 pfu/ml) and lung and serum cytokine levels. These results validate viroporin E as a viable antiviral target and support the clinical study of BIT225 for treatment and prophylaxis of SARS-CoV-2 infection. Author summaryAntiviral agents are highly important for the management of COVID-19. New antivirals are needed, because available drugs have drawbacks that limit their use and are threatened by drug resistance. This study demonstrates that the small molecule drug BIT225 is an inhibitor of an important viral ion channel (E protein). E protein is required for virus replication and is involved in eliciting inflammatory response to infection. Exacerbated inflammation is a hallmark of severe COVID-19 in mice and in humans. In a mouse model of severe SARS-CoV-2 infection, BIT225 treatment starting before or 24 hours after infection could protect all treated mice from developing disease, from experiencing weight loss and from death (100%, n = 17), while all untreated mice developed severe disease, started to lose body weight from Day 3 onwards and died within 9 days after infection. BIT225 treatment was associated with potent suppression of virus load, and reduced inflammation markers, consistent with effective clearance of the virus. These results are remarkable for the high efficacy achieved with a new mechanism of action. BIT225 is a clinical stage drug candidate with an established human safety profile. These results support clinical evaluation of BIT225 for the treatment of human SARS-CoV-2 infection.

Automated summary

The small molecule drug BIT225 inhibits the ion channel activity of the Coronavirus envelope (E) protein, preventing weight loss and death in SARS-CoV-2 infected mice. The drug shows broad-spectrum antiviral activity and significantly reduces viral load and inflammation markers. These findings support the clinical evaluation of BIT225 for the treatment of human SARS-CoV-2 infection.