We report the engineering and selection of two synthetic proteins—FSR16m and FSR22—for the possible treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. FSR16m and FSR22 are trimeric proteins composed of DARPin SR16m or SR22 fused with a T4 foldon. Despite selection by a spike protein from a now historical SARS-CoV-2 strain, FSR16m and FSR22 exhibit broad-spectrum neutralization of SARS-CoV-2 strains, inhibiting authentic B.1.351, B.1.617.2 and BA.1.1 viruses, with respective IC₅₀ values of 3.4, 2.2 and 7.4 ng ml⁻¹ for FSR16m. Cryo-EM structures revealed that these DARPins recognize a region of the receptor-binding domain (residues 456, 475, 486, 487 and 489) overlapping a critical portion of the angiotensin-converting enzyme 2 (ACE2)-binding surface. K18-hACE2 transgenic mice inoculated with B.1.617.2 and receiving intranasally administered FSR16m showed less weight loss and 10–100-fold lower viral burden in upper and lower respiratory tracts. The strong and broad neutralization potency makes FSR16m and FSR22 promising candidates for the prevention and treatment of infection by SARS-CoV-2.

我们报告了两种合成蛋白——FSR16m 和 FSR22——的工程和选择，用于可能治疗严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染。 FSR16m 和 FSR22 是由 DARPin SR16m 或 SR22 与 T4 折叠子融合组成的三聚体蛋白。尽管 FSR16m 和 FSR22 是通过来自现在历史上的 SARS-CoV-2 毒株的刺突蛋白进行选择的，但 FSR16m 和 FSR22 表现出对 SARS-CoV-2 毒株的广谱中和作用，抑制真正的 B.1.351、B.1.617.2 和 BA.1.1 病毒， FSR16m的IC ₅₀值分别为3.4、2.2和7.4 ng ml ^-1 。冷冻电镜结构显示，这些 DARPins 识别与血管紧张素转换酶 2 (ACE2) 结合表面的关键部分重叠的受体结合结构域区域（残基 456、475、486、487 和 489）。接种 B.1.617.2 并接受鼻内施用 FSR16m 的 K18-hACE2 转基因小鼠显示体重减轻较少，上呼吸道和下呼吸道病毒负荷降低 10-100 倍。强大而广泛的中和效力使 FSR16m 和 FSR22 有希望成为预防和治疗 SARS-CoV-2 感染的候选药物。