By late 2020, the
coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), had caused
tens of millions of
infections and over 1 million deaths worldwide. A protective
vaccine and more effective
therapeutics are urgently needed. We evaluated a new
poly(ADP-ribose) polymerase (
PARP) inhibitor,
stenoparib, that recently advanced to phase II clinical trials for treatment of
ovarian cancer, for activity against human respiratory coronaviruses, including SARS-CoV-2, in vitro
Stenoparib exhibits dose-dependent suppression of SARS-CoV-2 multiplication and spread in Vero E6 monkey kidney and Calu-3 human
lung adenocarcinoma cells.
Stenoparib was also strongly inhibitory to the human seasonal respiratory coronavirus HCoV-NL63. Compared to
remdesivir, which inhibits viral replication downstream of cell entry,
stenoparib impedes entry and postentry processes, as determined by time-of-addition (TOA) experiments. Moreover, a 10 μM dosage of
stenoparib-below the approximated 25.5 μM half-maximally effective concentration (EC50)-combined with 0.5 μM
remdesivir suppressed coronavirus growth by more than 90%, indicating a potentially synergistic effect for this
drug combination.
Stenoparib as a stand-alone or as part of combinatorial
therapy with
remdesivir should be a valuable addition to the arsenal against COVID-19.IMPORTANCE New
therapeutics are urgently needed in the fight against
COVID-19. Repurposing drugs that are either already approved for human use or are in advanced stages of the approval process can facilitate more rapid advances toward this goal. The
PARP inhibitor stenoparib may be such a drug, as it is currently in phase II clinical trials for the treatment of
ovarian cancer and its safety and dosage in humans have already been established. Our results indicate that
stenoparib possesses strong
antiviral activity against SARS-CoV-2 and other coronaviruses in vitro. This activity appears to be based on multiple modes of action, where both pre-entry and postentry viral replication processes are impeded. This may provide a therapeutic advantage over many current options that have a narrower target range. Moreover, our results suggest that
stenoparib and
remdesivir in combination may be especially potent against
coronavirus infection.