APABETALONE (RVX-208) REDUCES ACE2 PROTEIN ABUNDANCE AND PREVENTS SARS-COV-2 SPIKE PROTEIN BINDING TO HUMAN LUNG CELLS, A MOA THAT COULD ATTENUATE VIRAL ENTRY

Background

Human angiotensin converting enzyme 2 (ACE2) is essential for SARS-CoV-2 (CoV-2) virus entry by acting as a receptor for CoV-2 spike protein. BET proteins, epigenetic readers that regulate gene transcription in host cell nuclei, have recently been demonstrated to engage in CoV-2 viral replication. Apabetalone is a well-tolerated BET protein inhibitor in late stage clinical development for cardiovascular disease without affecting blood pressure. This study examines potential repurposing of apabetalone to reduce CoV-2 infection in the lung and other tissues by downregulating ACE2 expression.

Methods

ACE2 protein levels and gene expression were assessed by flow cytometry and real-time PCR in human lung epithelial cells (Calu-3) and monkey kidney epithelial cells (Vero E6) treated with apabetalone for up to 72hrs. In parallel, apabetalone impact on specific binding of CoV-2 spike protein to cell surface ACE2 was assessed by flow cytometry. Changes in ACE2 mRNA levels were also determined in apabetalone treated primary human kidney tubular epithelial cells (RPTEC) and primary human hepatocytes (PHH).

Results

Apabetalone dose dependently reduced cell surface ACE2 protein on Calu-3 by up to 80% (72h treatment) and on Vero E6 by 45% (48h treatment), in line with downregulation of ACE2 gene expression (>90% reduction in mRNA). Further, following apabetalone treatment, binding of CoV-2 spike protein to the surface of Calu-3 or Vero E6 cells was diminished by 75% or 54%, respectively. In addition, a reduction in ACE2 mRNA levels was observed in apabetalone treated extrapulmonary cells including RPTEC (by 50%) and PHH (up to 90%, 3 different donors).

Conclusion

Apabetalone reduces ACE2 protein abundance and attenuates binding of CoV-2 spike protein in human lung cells and monkey kidney cells, both of which can propagate CoV-2. Mechanistically, apabetalone suppresses ACE2 transcription in lung and extrapulmonary cells. Our results suggest apabetalone may mitigate CoV-2 replication/transmission in multiple organs. The ability of apabetalone to impede in vitro replication of live CoV-2 is under investigation, which may support clinical evaluation of apabetalone to treat COVID-19.