Capivasertib 是一种有效的 AKT 选择性抑制剂。最近 FDA 批准它与氟维司群联合治疗具有激活 PI3K 通路的某些基因改变的 HR 、HER2 阴性乳腺癌。在 I 期试验中，经过大量预先治疗的肿瘤患者选择激活 PI3K 通路突变，接受 capivasertib 单药治疗，表现出客观缓解率 <30%。我们研究了基因预选患者和癌细胞系中与 capivasertib 反应相关的蛋白质组谱。我们分析了 I 期试验中在 capivasertib 单药治疗之前收集的 16 例 PIK3CA 突变患者肿瘤的样本。使用免疫 MALDI-MS 精确定量 PI3K 通路蛋白。还获得了整体蛋白质组图谱。根据对 capivasertib 单药治疗的反应对患者进行分类：“临床获益 (CB)”（≥12 周无进展，n=7）或“无临床获益 (NCB)”（<12 周内进展，n=9）。随后在具有不同 capivasertib 敏感性的 AKT1 或 PIK3CA 改变的乳腺癌细胞系中对患者组之间存在差异的蛋白质进行定量。 PIK3CA 突变肿瘤中 AKT1 和 AKT2 的测量浓度有所不同，但 CB 组和 NCB 组之间没有差异。然而，对全球蛋白质组数据的分析表明，NCB 组肿瘤的翻译活性高于 CB 组。当通过经过验证的 LC-MRM-MS 测定进行可重复定量时，相同的目标蛋白在 capivasertib 敏感细胞系和耐药细胞系之间具有相似的区别。结果进一步证明 mTORC1 驱动的翻译功能增强是对 capivasertib 单一疗法产生耐药性的机制。蛋白质浓度可能为 capivasertib 的患者选择提供额外的见解，甚至在基因预先选择的患者中也是如此。

Capivasertib is a potent selective inhibitor of AKT. It was recently FDA-approved in combination with fulvestrant to treat HR+, HER2-negative breast cancers with certain genetic alteration(s) activating the PI3K pathway. In Phase I trials, heavily pre-treated patients with tumours selected for activating PI3K pathway mutations treated with capivasertib monotherapy demonstrated objective response rates of <30%. We investigated the proteomic profile associated with capivasertib response in genetically pre-selected patients and cancer cell lines. We analyzed samples from 16 PIK3CA-mutated patient tumours collected prior to capivasertib monotherapy in the Phase I trial. PI3K pathway proteins were precisely quantified with immuno-MALDI-MS. Global proteomic profiles were also obtained. Patients were classified according to response to capivasertib monotherapy: "clinical benefit (CB)" (≥12 weeks without progression, n=7) or "no clinical benefit (NCB)" (progression in <12 weeks, n=9). Proteins that differed between the patient groups were subsequently quantified in AKT1- or PIK3CA-altered breast cancer cell lines with varying capivasertib sensitivity. The measured concentrations of AKT1 and AKT2 varied among the PIK3CA-mutated tumours but did not differ between the CB and NCB groups. However, analysis of the global proteome data showed that translational activity was higher in tumours of the NCB vs. CB group. When reproducibly quantified by validated LC-MRM-MS assays, the same proteins of interest similarly distinguished between capivasertib-sensitive vs. -resistant cell lines. The results provide further evidence that increased mTORC1-driven translation functions as a mechanism of resistance to capivasertib monotherapy. Protein concentrations may offer additional insights for patient selection for capivasertib, even among genetically pre-selected patients.