Quest Diagnostics Nichols Institute San Juan Capistrano, San Juan Capistrano, California, United States of America.
PLoS One. 2013 Aug 21;8(8):e71703. doi: 10.1371/journal.pone.0071703. eCollection 2013.
Response to cetuximab (Erbitux®) and panitumumab (Vectibix®) varies among individuals, and even those who show response ultimately gain drug resistance. One possible etiologic factor is differential interaction between the drug and target. We describe the development of an assay based on Slow Off-rate Modified Aptamer (SOMAmer(™)) reagents that can distinguish drug-bound from unbound epidermal growth factor receptor (EGFR).
This quantitative assay uses a SOMAmer reagent specific for EGFR extracellular domain (ECD) as a capturing reagent. Captured SOMAmer is quantitated using PCR. Linearity and accuracy (recovery) of the assay were assessed using normal sera and purified EGFR ECD.
This EGFR ECD assay showed linearity between 2.5 and 600 ng/mL. Average recovery was 101%. The assay detected EGFR but showed little cross-reactivity to other ErbB proteins: 0.4% for ErbB2, 6.9% for ErbB3, and 1.3% for ErbB4. Preincubation of normal serum with either cetuximab or panitumumab resulted in a dose-dependent decrease in EGFR ECD levels measured using the SOMAmer assay; preincubation did not affect measurement with an ELISA.
This SOMAmer-based serum EGFR ECD assay accurately and specifically measures EGFR in serum. Detection of significant amounts of drug-unbound EGFR in patients undergoing cetuximab or panitumumab treatment could be an indicator of poor drug response. Further studies are needed to evaluate the utility of the assay as an indicator of drug efficacy or as a guide to dosing.
西妥昔单抗（Erbitux®）和帕尼单抗（Vectibix®）的应答在个体之间存在差异，甚至那些表现出应答的患者最终也会产生耐药性。一个可能的病因是药物与靶点之间的差异相互作用。我们描述了一种基于慢脱靶修饰适体（SOMAmer(™)）试剂的测定方法的开发，该方法可以区分药物结合和未结合的表皮生长因子受体（EGFR）。
该定量测定使用针对 EGFR 细胞外结构域（ECD）的特异性 SOMAmer 试剂作为捕获试剂。使用 PCR 定量捕获的 SOMAmer。使用正常血清和纯化的 EGFR ECD 评估测定的线性和准确性（回收率）。
该 EGFR ECD 测定在 2.5 至 600ng/mL 之间显示出线性。平均回收率为 101%。该测定检测到 EGFR，但对其他 ErbB 蛋白显示出很小的交叉反应性：ErbB2 为 0.4%，ErbB3 为 6.9%，ErbB4 为 1.3%。正常血清与西妥昔单抗或帕尼单抗预孵育会导致使用 SOMAmer 测定法测量的 EGFR ECD 水平呈剂量依赖性降低；预孵育不会影响 ELISA 的测量。
基于 SOMAmer 的血清 EGFR ECD 测定法准确且特异性地测量血清中的 EGFR。在接受西妥昔单抗或帕尼单抗治疗的患者中检测到大量药物未结合的 EGFR 可能是药物反应不佳的指标。需要进一步研究来评估该测定作为药物疗效指标或作为剂量指导的实用性。
