Development of specific antiviral agents is an urgent unmet need for SARS-coronavirus 2 (SARS-CoV-2) infection. This study focuses on host proteases that proteolytically activate the SARS-CoV-2 spike protein, critical for its fusion after binding to angiotensin-converting enzyme 2 (ACE2), as antiviral targets. We first validate cleavage at a putative furin substrate motif at SARS-CoV-2 spikes by expressing it in VeroE6 cells and find prominent syncytium formation. Cleavage and the syncytium are abolished by treatment with the furin inhibitors decanoyl-RVKR-chloromethylketone (CMK) and naphthofluorescein, but not by the transmembrane protease serine 2 (TMPRSS2) inhibitor camostat. CMK and naphthofluorescein show antiviral effects on SARS-CoV-2-infected cells by decreasing virus production and cytopathic effects. Further analysis reveals that, similar to camostat, CMK blocks virus entry, but it further suppresses cleavage of spikes and the syncytium. Naphthofluorescein acts primarily by suppressing viral RNA transcription. Therefore, furin inhibitors may be promising antiviral agents for prevention and treatment of SARS-CoV-2 infection.

对SARS冠状病毒2（SARS-CoV-2）感染的迫切未满足的需求是开发特定的抗病毒剂。这项研究的重点是蛋白水解激活SARS-CoV-2突突蛋白的宿主蛋白酶，该蛋白对于结合抗血管紧张素转化酶2（ACE2）作为抗病毒目标后的融合至关重要。我们首先通过在VeroE6细胞中表达它来验证SARS-CoV-2穗突在假定的弗林蛋白酶底物基序处的裂解，并发现明显的合胞体形成。通过使用弗林蛋白酶抑制剂癸酰基-RVKR-氯甲基酮（CMK）和萘荧光素治疗，可消除卵裂和合胞体，但可通过跨膜蛋白酶丝氨酸2（TMPRSS2）抑制剂康美他治疗来消除。CMK和萘荧光素通过减少病毒产生和细胞病变作用，对SARS-CoV-2感染的细胞显示抗病毒作用。进一步的分析表明，与拟态抑制器相似，CMK阻止病毒进入，但它进一步抑制了尖峰和合胞体的裂解。萘荧光素主要通过抑制病毒RNA转录起作用。因此，弗林蛋白酶抑制剂可能是预防和治疗SARS-CoV-2感染的有希望的抗病毒药物。