Nucleoside reverse transcriptase inhibition enhances platelet production and megakaryocyte maturation in patients with <scp>COVID</scp>‐19

Coronavirus disease 2019 (COVID-19) is a systemic infection frequently involving the haematopoietic system. Thrombocytopenia is associated with increased risks of severe disease progression and mortality. Antiviral agents have shown much promise in decreasing viral load and shortening the time to the resolution of symptoms. However, their effect on platelet counts in patients with COVID-19 remains unexplored. Therefore, we first performed a retrospective study to evaluate the variation in platelet mass of hospitalized patients with high-risk COVID-19 who were given either SARS-CoV-2 main protease inhibitor, nucleoside reverse transcriptase inhibitor or no antiviral agents. A total of 177 patients were included, among which 64 received azvudine, 12 received nirmatrelvir-ritonavir and 101 patients received none. Compared to those without antiviral treatment, significantly higher platelet counts' increments were observed in patients receiving azvudine or nirmatrelvir-ritonavir (p = 0.001). Of note, this elevation was significantly more profound in the azvudine group than that in the control group (p < 0.001) or the nirmatrelvir-ritonavir group (p = 0.042). Subsequently, in vitro experiments were conducted to investigate the mechanism of platelet elevation underlying the activity of azvudine. Results showed that azvudine promoted the polyploidization and platelet production of the MEG-01 cell line. Although azvudine had minimal effect on megakaryopoiesis, it could significantly trigger platelet release of megakaryocytes in the presence of SARS-CoV-2 spike-membrane recombinant fusion protein or not. Finally, RNA-sequencing demonstrated that azvudine-treated MEG-01 exhibited a marked increase in VWF, TUBB1 and GP1BA, and upregulated genes associated with the PI3K/AKT and JAK/STAT signalling pathways. In conclusion, our findings indicated that nucleoside reverse transcriptase inhibition potentially enhances platelet production and megakaryocyte maturation in patients with COVID-19, suggesting a new therapeutic option for thrombocytopenia.