Relaxin/insulin-like family peptide receptor 4 (RXFP4) is a class A G protein-coupled receptor (GPCR), and insulin-like peptide 5 (INSL5) is its endogenous ligand. Although the precise physiological role of INSL5/RXFP4 remains elusive, a number of studies have suggested it to be a potential therapeutic target for obesity and other metabolic disorders. Since selective agonists of RXFP4 are scarcely available and peptidic analogs of INSL5 are hard to make, we conducted a high-throughput screening campaign against 52,000 synthetic and natural compounds targeting RXFP4. Of the 109 initial hits discovered, only 3 compounds were confirmed in secondary screening, with JK0621-D008 displaying the best agonism at human RXFP4. Its S-configuration stereoisomer (JK1) was subsequently isolated and validated by a series of bioassays, demonstrating a consistent agonistic effect in cells overexpressing RXFP4. This scaffold may provide a valuable tool to further explore the biological functions of RXFP4.

松弛素/胰岛素样家族肽受体4（RXFP4）是AG类蛋白偶联受体（GPCR），胰岛素样肽5（INSL5）是其内源配体。尽管INSL5 / RXFP4的确切生理作用仍然难以捉摸，但许多研究表明，它是肥胖症和其他代谢性疾病的潜在治疗靶标。由于几乎没有可用的RXFP4选择性激动剂，而且很难制成INSL5的肽类似物，因此我们针对52,000种靶向RXFP4的合成和天然化合物进行了高通量筛选。在发现的109个初始匹配中，只有3种化合物在二次筛选中得到确认，JK0621-D008对人RXFP4表现出最佳的激动作用。它的S构型立体异构体（JK1）随后被分离，并通过一系列的生物测定方法验证，证明了在过量表达RXFP4的细胞中具有一致的激动作用。该支架可能为进一步探索RXFP4的生物学功能提供有价值的工具。