ABSTRACT
The continued evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has compromised the efficacy of currently available vaccines and monoclonal antibody (mAb)-based treatment options for COVID-19. The limited number of authorized small-molecule direct-acting antivirals present challenges with pill burden, the necessity for intravenous administration or potential drug interactions. There remains an unmet medical need for effective and convenient treatment options for SARS-CoV-2 infection. SARS-CoV-2 is an RNA virus that depends on host intracellular ribonucleotide pools for its replication. Dihydroorotate dehydrogenase (DHODH) is a ubiquitous host enzyme that is required for de novo pyrimidine synthesis. The inhibition of DHODH leads to a depletion of intracellular pyrimidines, thereby impacting viral replication in vitro. Brequinar (BRQ) is an orally available, selective, and potent low nanomolar inhibitor of human DHODH that has been shown to exhibit broad spectrum inhibition of RNA virus replication. However, host cell nucleotide salvage pathways can maintain intracellular pyrimidine levels and compensate for BRQ-mediated DHODH inhibition. In this report, we show that the combination of BRQ and the salvage pathway inhibitor dipyridamole (DPY) exhibits strong synergistic antiviral activity in vitro against SARS-CoV-2 by enhanced depletion of the cellular pyrimidine nucleotide pool. The combination of BRQ and DPY showed antiviral activity against the prototype SARS-CoV-2 as well as the Beta (B.1.351) and Delta (B.1.617.2) variants. These data support the continued evaluation of the combination of BRQ and DPY as a broad-spectrum, host-acting antiviral strategy to treat SARS-CoV-2 and potentially other RNA virus infections.
Competing Interest Statement
Drs Kienle and Kumar are employees of Clear Creek Bio. Drs Demarest, Kienle, Pottage, Shohdy, Sykes, and Kumar hold equity in Clear Creek Bio. Dr Sykes and Kumar are co-founders of Clear Creek Bio. Dr Sykes holds equity in SAFI Biosolutions. Drs Gandhi, Chung, Demarest, Pottage, Shohdy and Sykes are paid consultants of Clear Creek Bio. Clear Creek Bio funded all work described in this article, including Sponsored Research Agreements with Boston University, MD Anderson Cancer Center and the University of Louisville.
