BACKGROUND The c.3700A>G mutation, a rare cystic fibrosis (CF)-causing CFTR mutation found mainly in the Middle East, produces full-length transcript encoding a missense mutation (I1234V-CFTR), and a cryptic splice site that deletes 6 amino acids in nucleotide binding domain 2 (I1234del-CFTR). METHODS FRT cell models expressing I1234V-CFTR and I1234del-CFTR were generated. We also studied an I1234del-CFTR-expressing gene-edited human bronchial (16HBE14o-) cell model, and primary cultures of nasal epithelial cells from a c.3700A>G homozygous subject. To identify improved mutation-specific CFTR modulators, high-throughput screening was done using I1234del-CFTR-expressing FRT cells. Motivated by the in vitro findings, Trikafta was tested in two c.3700A>G homozygous CF subjects. RESULTS FRT cells expressing full-length I1234V-CFTR had similar function to that of wildtype CFTR. I1234del-CFTR showed reduced activity, with modest activation seen with potentiators VX-770 and GLPG1837, correctors VX-809, VX-661 and VX-445, and low-temperature incubation. Screening identified novel arylsulfonyl-piperazine and spiropiperidine-quinazolinone correctors, which when used in combination with VX-445 increased current ~2-fold compared with the VX-661/VX-445 combination. The combination of VX-770 with arylsulfonamide-pyrrolopyridine, piperidine-pyridoindole or pyrazolo-quinoline potentiators gave 2-4-fold greater current than VX-770 alone. Combination potentiator (co-potentiator) efficacy was also seen in gene-edited I1234del-CFTR-expressing human bronchial epithelial cells. In two CF subjects homozygous for the c.3700A>G mutation, one subject had a 27 mmol/L decrease in sweat chloride and symptomatic improvement on Trikafta, and a second subject showed a small improvement in lung function. CONCLUSIONS These results support the potential benefit of CFTR modulators, including co-potentiators, for CF caused by the c.3700A>G mutation.

中文翻译：

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CFTR 调节剂治疗罕见的 c.3700A>G 突变引起的囊性纤维化

背景 c.3700A>G 突变是一种罕见的导致囊性纤维化 (CF) 的 CFTR 突变，主要在中东发现，它产生编码错义突变 (I1234V-CFTR) 的全长转录本，以及一个删除 6核苷酸结合域 2 (I1234del-CFTR) 中的氨基酸。方法 生成表达 I1234V-CFTR 和 I1234del-CFTR 的 FRT 细胞模型。我们还研究了表达 I1234del-CFTR 的基因编辑的人支气管 (16HBE14o-) 细胞模型，以及来自 c.3700A>G 纯合受试者的鼻上皮细胞的原代培养物。为了鉴定改进的突变特异性 CFTR 调节剂，使用表达 I1234del-CFTR 的 FRT 细胞进行了高通量筛选。受体外研究结果的启发，Trikafta 在两个 c.3700A>G 纯合 CF 受试者中进行了测试。结果表达全长I1234V-CFTR的FRT细胞具有与野生型CFTR相似的功能。I1234del-CFTR 的活性降低，在增强剂 VX-770 和 GLPG1837、校正剂 VX-809、VX-661 和 VX-445 以及低温孵育中观察到适度的活化。筛选确定了新的芳基磺酰基-哌嗪和螺哌啶-喹唑啉酮校正剂，与 VX-445 组合使用时，与 VX-661/VX-445 组合相比，电流增加约 2 倍。VX-770 与芳基磺酰胺-吡咯并吡啶、哌啶-吡啶吲哚或吡唑并-喹啉增效剂的组合产生的电流比单独的 VX-770 大 2-4 倍。在基因编辑的表达 I1234del-CFTR 的人支气管上皮细胞中也观察到联合增效剂（共增效剂）的功效。在 c.3700A>G 突变纯合的两个 CF 受试者中，一名受试者的汗液氯化物减少了 27 mmol/L，Trikafta 的症状有所改善，另一名受试者的肺功能略有改善。结论 这些结果支持 CFTR 调节剂（包括共增效剂）对 c.3700A>G 突变引起的 CF 的潜在益处。