AbstractHER2 is a transmembrane tyrosine kinase receptor that mediates cell growth, differentiation, and survival. HER2 is overexpressed in approximately 20% of breast cancers and in subsets of gastric, colorectal, and esophageal cancers. Both antibody and small-molecule drugs that target HER2 and block its tyrosine kinase activity are effective in treating HER2-driven cancers. In this article, we describe the preclinical properties of tucatinib, an orally available, reversible HER2-targeted small-molecule tyrosine kinase inhibitor. In both biochemical and cell signaling experiments, tucatinib inhibits HER2 kinase activity with single-digit nanomolar potency and provides exceptional selectivity for HER2 compared with the related receptor tyrosine kinase EGFR, with a >1,000-fold enhancement in potency for HER2 in cell signaling assays. Tucatinib potently inhibits signal transduction downstream of HER2 and HER3 through the MAPK and PI3K/AKT pathways and is selectively cytotoxic in HER2-amplified breast cancer cell lines in vitro. In vivo, tucatinib is active in multiple HER2+ tumor models as a single agent and shows enhanced antitumor activity in combination with trastuzumab or docetaxel, resulting in improved rates of partial and complete tumor regression. These preclinical data, taken together with the phase-I tucatinib clinical trial results demonstrating preliminary safety and activity, establish the unique pharmacologic properties of tucatinib and underscore the rationale for investigating its utility in HER2+ cancers.
摘要 HER2 是一种跨膜酪氨酸激酶受体,可介导细胞生长、分化和存活。大约 20% 的乳腺癌以及胃癌、结肠直肠癌和食管癌亚群中 HER2 过表达。靶向 HER2 并阻断其酪氨酸激酶活性的抗体药物和小分子药物都能有效治疗 HER2 驱动的癌症。在这篇文章中,我们描述了一种口服、可逆的 HER2 靶向小分子酪氨酸激酶抑制剂--图卡替尼的临床前特性。在生化和细胞信号实验中,图卡替尼以个位数纳摩尔的效力抑制HER2激酶的活性,与相关受体酪氨酸激酶表皮生长因子受体相比,图卡替尼对HER2具有优异的选择性,在细胞信号实验中对HER2的效力提高了1000倍。图卡替尼通过 MAPK 和 PI3K/AKT 通路有效抑制 HER2 和 HER3 下游的信号转导,在体外对 HER2 扩增的乳腺癌细胞株具有选择性细胞毒性。在体内,作为单药,图卡替尼在多种 HER2+ 肿瘤模型中均有活性,与曲妥珠单抗或多西他赛联合用药可增强抗肿瘤活性,提高肿瘤部分和完全消退率。这些临床前数据与显示初步安全性和活性的图卡替尼一期临床试验结果相结合,确立了图卡替尼的独特药理特性,并强调了研究其在 HER2+ 癌症中应用的合理性。