Coronavirus disease 2019 (COVID‐19) presents a major worldwide public health emergency. Many research efforts are ongoing to find effective antiviral treatments via novel drug design or drug repurposing.1 One drug, remdesivir, has been shown to have activity against the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) RNA dependent RNA polymerase (RdRp), and has been used clinically in severe COVID‐19 disease, but more accessible and readily available treatments are needed for all stages of infection.

Two recent reports discussed both anecdotal positive clinical benefits and the potential for off‐label use of the drug montelukast in certain patients with COVID‐19,2, 3 which led us to investigate its potential anti‐SARS‐CoV‐2 properties in silico. Montelukast had previously been shown to have antiviral activity against ZIKA and dengue viruses,4 as well as immune modulatory properties. We hypothesized that montelukast might have antiviral activity against SARS‐CoV‐2, and act as an anti‐inflammatory agent effective against exuberant immune activation in COVID‐19 disease. Montelukast had been shown to inhibit macrophage M2 related cytokines, acting as a cysteinyl leukotriene receptor antagonist.5 It can also protect against Influenza A virus induced pneumonia by reducing infection of type‐1 alveolar epithelial cells and modulating other proinflammatory mediators.6 In a rat model, montelukast lowered TNF‐alpha and interleukin‐6, increased glutathione and superoxide dismutase7 and lowered mortality related to sepsis. The cytokine storm in COVID‐19 is at least partially caused by mast cell activation, and leukotriene receptor antagonists like montelukast could also be used for their ability to attenuate mast cell activation.8

We undertook an in silico molecular docking analysis to simulate binding of montelukast to catalytically active sites within the SARS‐CoV‐2 Main protease (Mpro) and RNA dependent RNA polymerase (RdRp). If montelukast could bind to key residues typically required for the enzymatic activity of these proteins, and effectively inhibit the activity of the Mpro, it should be able to disrupt the substrate binding site. We performed docking simulations using the Mpro (Protein Data Bank [PDB] ID: 6Y2E), and the RdRp (PDB ID: 6M71) of SARS‐Cov‐2, using the Protein‐Ligand ANT System (PLANTS)9 program. The ligand docking sites were specified as the catalytically active sites by Zhang et al.10 and Gao et al.11 The resulting protein‐ligand scores (PLANTS scores) were calculated using the empirical scoring algorithm CHEMPLP,9 and reflect the energy change when ligands and proteins come together, with values more negative than (−91.00) suggesting likely protein‐ligand interactions.12, 13 All other docking parameters and forcefields are noted in our previous work.13 Protein‐ligand structures were visualized using PyMol 2.3.5. The PLANTS_chemplp scores reflects the energy change when montelukast binds to the catalytic site of either the Mpro or RdRp with more negative numbers suggesting a more probable drug‐protein interaction (see Figure 1). As the PLANTS_chemplp program employs an empirical scoring function and utilizes a semi‐flexible docking method, the scoring function employs some level of molecular dynamics.

The PLANTS_chemplp docking score of montelukast against the Mpro is −105.71, and the RdRp −104.75. These docking scores suggest that montelukast is likely to dock to both the Mpro and the RdRp of SARS‐CoV‐2 (Figure 2). For comparison, the docking score of remdesivir to the SARS‐CoV‐2 RdRp is −102.09. The mechanism of action likely conferred by binding would need to be determined in vitro, but is probably through competitive inhibition at the enzymatic sites. To disrupt the catalytic site of the polymerase it would need to have a lower free energy than the elongating RNA and ribonucleotides at this site. The accumulation of data on the drug montelukast, including the data presented here, it's known antiviral activity4 and immunomodulation,5-8 along with anecdotal evidence in patients with COVID‐19,2 suggests a repurposing potential for montelukast in the treatment of COVID‐19. We would like to caution readers that, despite the in silico evidence described here, there is no robust evidence yet that montelukast will be an effective treatment for COVID‐19. Montelukast is used for allergic rhinitis and now off‐label for COVID‐19, however physicians are ultimately responsible for prescribing drugs like montelukast. There is a Blackbox warning for the use of montelukast, noting serious mental health side‐effects. However, our studies suggest that further investigation into the role of montelukast in SARS‐CoV‐2 prevention or COVID‐19 amelioration is warranted.

2019 年冠状病毒病 (COVID‐19) 是全球重大的突发公共卫生事件。许多研究工作正在进行中，以通过新的药物设计或药物再利用来寻找有效的抗病毒治疗方法。1一种药物瑞德西韦已被证明对严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) RNA 依赖性 RNA 聚合酶 (RdRp) 具有活性，并已在临床上用于严重的 COVID-19 疾病，但更容易获得所有感染阶段都需要现成的治疗方法。

最近的两份报告讨论了轶事的积极临床益处和药物孟鲁司特在某些 COVID-19、2、3 患者中的标签外使用潜力，这使我们在计算机上研究了其潜在的抗 SARS-CoV-2 特性。孟鲁司特先前已被证明具有抗寨卡病毒和登革热病毒的抗病毒活性，4以及免疫调节特性。我们假设孟鲁司特可能对 SARS-CoV-2 具有抗病毒活性，并作为一种抗炎剂，可有效对抗 COVID-19 疾病中的旺盛免疫激活。孟鲁司特已被证明可抑制巨噬细胞 M2 相关细胞因子，充当半胱氨酰白三烯受体拮抗剂。5它还可以通过减少 1 型肺泡上皮细胞的感染和调节其他促炎介质来预防甲型流感病毒引起的肺炎。6在大鼠模型中，孟鲁司特降低了 TNF-α 和白细胞介素-6，增加了谷胱甘肽和超氧化物歧化酶7，并降低了与败血症相关的死亡率。COVID-19 中的细胞因子风暴至少部分是由肥大细胞活化引起的，而像孟鲁司特这样的白三烯受体拮抗剂也可用于减弱肥大细胞活化的能力。8

我们进行了计算机分子对接分析，以模拟孟鲁司特与 SARS-CoV-2 主要蛋白酶 (Mpro) 和 RNA 依赖性 RNA 聚合酶 (RdRp) 内的催化活性位点的结合。如果孟鲁司特可以结合这些蛋白质的酶活性通常需要的关键残基，并有效抑制 Mpro 的活性，它应该能够破坏底物结合位点。我们使用蛋白质配体 ANT 系统 (PLANTS) 9程序，使用 Mpro（蛋白质数据库 [PDB] ID：6Y2E）和 SARS-Cov-2 的 RdRp（PDB ID：6M71）进行了对接模拟。Zhang 等人将配体对接位点指定为催化活性位点。10和高等人。11使用经验评分算法 CHEMPLP 9计算得到的蛋白质-配体分数（PLANTS 分数），反映配体和蛋白质结合时的能量变化，比 (-91.00) 更负的值表明可能的蛋白质-配体相互作用。12, 13我们之前的工作中记录了所有其他对接参数和力场。使用 PyMol 2.3.5 可视化13种蛋白质配体结构。PLANTS _chemmplp分数反映了当孟鲁司特与 Mpro 或 RdRp 的催化位点结合时的能量变化，负数越多，表明药物-蛋白质相互作用的可能性越大（见图 1）。作为 PLANTS _chemmplp程序采用经验评分函数并采用半灵活对接方法，评分函数采用某种程度的分子动力学。

孟鲁司特与 Mpro的 PLANTS _chemmplp对接得分为 -105.71，RdRp 为 -104.75。这些对接分数表明，孟鲁司特可能同时与 SARS-CoV-2 的 Mpro 和 RdRp 对接（图 2）。作为比较，瑞德西韦与 SARS-CoV-2 RdRp 的对接得分为 -102.09。可能由结合赋予的作用机制需要在体外​​确定，但可能是通过酶促位点的竞争性抑制。为了破坏聚合酶的催化位点，它需要比该位点的延伸 RNA 和核糖核苷酸具有更低的自由能。关于药物孟鲁司特的数据积累，包括此处提供的数据，已知的抗病毒活性4和免疫调节，5-8连同在 COVID-19 患者中的轶事证据，2表明孟鲁司特在 COVID-19 治疗中的再利用潜力。我们想提醒读者，尽管此处描述了计算机证据，但尚无强有力的证据表明孟鲁司特将成为 COVID-19 的有效治疗方法。孟鲁司特用于治疗过敏性鼻炎，现在 COVID-19 的标签外用药，但医生最终负责开出孟鲁司特等药物。使用孟鲁司特有一个黑盒警告，指出严重的心理健康副作用。然而，我们的研究表明，有必要进一步研究孟鲁司特在预防 SARS-CoV-2 或改善 COVID-19 中的作用。