Papain-like protease (PLpro) is a promising therapeutic target for its pivotal role in the life cycle of SARS-CoV-2. A series of 1,2,4-oxadiazole derivatives was designed and synthesized via a ring formation strategy based on SARS-CoV-2 PLpro–GRL0617 complex structure. Systematic structure–activity relationship studies revealed that introducing oxadiazole and aryl carboxylic acid moieties to GRL0617 enhanced the enzymatic inhibition activity, affinity, and deubiquitination capacity toward PLpro. 1,2,4-Oxadiazole compounds 13f and 26r, which had PLpro inhibition activity (IC₅₀ = 1.8 and 1.0 μM) and antiviral activity against SARS-CoV-2 (EC₅₀ = 5.4 and 4.3 μM), exhibited good metabolic stability (t_1/2 > 93.2 min) and higher plasma exposure (AUC_0–t = 17,380.08 and 24,289.76 ng·h/mL) in mice. Especially, compound 26r with moderate oral bioavailability of 39.1% and potent antiviral activity is worthy of further studies in vivo. Our findings provide a new insight for the discovery of antiviral agents targeting PLpro.

中文翻译：

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含有芳基羧酸部分的 1,2,4-恶二唑衍生物作为有效 Sarbecovirus 木瓜蛋白酶样蛋白酶抑制剂的设计、合成和生物学评价


木瓜蛋白酶样蛋白酶 (PLpro) 因其在 SARS-CoV-2 生命周期中的关键作用而成为一个有前途的治疗靶点。基于SARS-CoV-2 PLpro-GRL0617复合物结构，通过成环策略设计并合成了一系列1,2,4-恶二唑衍生物。系统构效关系研究表明，GRL0617 中引入恶二唑和芳基羧酸部分增强了对 PLpro 的酶抑制活性、亲和力和去泛素化能力。 1,2,4-恶二唑化合物 13f 和 26r，具有 PLpro 抑制活性（IC ₅₀ = 1.8 和 1.0 μM）和针对 SARS-CoV-2 的抗病毒活性（EC ₅₀ = 5.4 和 4.3 μM），在小鼠中表现出良好的代谢稳定性（t _1/2 > 93.2 min）和较高的血浆暴露量（AUC _0–t = 17,380.08 和 24,289.76 ng·h/mL）。特别是，化合物26r具有39.1%的中等口服生物利用度和有效的抗病毒活性，值得在体内进一步研究。我们的研究结果为发现针对 PLpro 的抗病毒药物提供了新的见解。