1 Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.
2 Department of Ophthalmology, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
Thyroid. 2019 Jan;29(1):111-123. doi: 10.1089/thy.2018.0349. Epub 2018 Dec 15.
The thyrotropin receptor (TSHR) is the target for autoimmune thyroid stimulating antibodies (TSAb) triggering hyperthyroidism. Whereas elevated thyroid hormone synthesis by the thyroid in Graves' disease can be treated by antithyroid agents, for the pathogenic activation of TSHR in retro-orbital fibroblasts of the eye, leading to Graves' orbitopathy (GO), no causal TSHR directed therapy is available.
Due to the therapeutic gap for severe GO, TSHR inhibitors were identified by high-throughput screening in Chinese hamster ovary cells expressing the TSHR. Stereo-selective synthesis of the screening hits led to the molecule S37, which contains seven chiral centers. Enantiomeric separation of the molecule S37 resulted in the enantiopure molecule S37a-a micro-molar antagonist of thyrotropin-induced cyclic adenosine monophosphate accumulation in HEK 293 cells expressing the TSHR.
The unique rigid bent shape of molecule S37a may mediate the observed high TSHR selectivity. Most importantly, the closely related follitropin and lutropin receptors were not affected by this compound. S37a not only inhibits the TSHR activation by thyrotropin itself but also activation by monoclonal TSAb M22 (human), KSAb1 (murine), and the allosteric small-molecule agonist C2. Disease-related ex vivo studies in HEK 293 cells expressing the TSHR showed that S37a also inhibits cyclic adenosine monophosphate formation by oligoclonal TSAb, which are highly enriched in GO patients' sera. Initial in vivo pharmacokinetic studies revealed no toxicity of S37a and a remarkable 53% oral bioavailability in mice.
In summary, a novel highly selective inhibitor for the TSHR is presented, which has promising potential for further development for the treatment of GO.
促甲状腺素受体（TSHR）是自身免疫性甲状腺刺激抗体（TSAb）触发甲状腺功能亢进的靶标。虽然抗甲状腺药物可以治疗 Graves 病中甲状腺激素合成的升高，但对于眼眶成纤维细胞中 TSHR 的致病性激活导致 Graves 眼病（GO），目前尚无针对 TSHR 的因果治疗方法。
由于严重 GO 的治疗空白，通过在中国仓鼠卵巢细胞中表达 TSHR 进行高通量筛选，鉴定出 TSHR 抑制剂。对筛选出的化合物进行立体选择性合成，得到含有七个手性中心的化合物 S37。对分子 S37 进行对映体分离，得到对映体纯的分子 S37a，它是一种微摩尔级的 TSHR 拮抗剂，可抑制 HEK 293 细胞中 TSH 诱导的环腺苷酸积累。
分子 S37a 的独特刚性弯曲形状可能介导了观察到的高 TSHR 选择性。最重要的是，该化合物对紧密相关的卵泡刺激素和黄体生成素受体没有影响。S37a 不仅抑制 TSH 自身对 TSHR 的激活，还抑制单克隆 TSAb M22（人）、KSAb1（鼠）和变构小分子激动剂 C2 的激活。在表达 TSHR 的 HEK 293 细胞中的疾病相关的体外研究表明，S37a 还抑制 GO 患者血清中高度富集的多克隆 TSAb 形成环腺苷酸。初步的体内药代动力学研究表明 S37a 没有毒性，在小鼠中的口服生物利用度为 53%。
总之，本文提出了一种新型高选择性的 TSHR 抑制剂，具有进一步开发治疗 GO 的潜力。
