From the Department of Nuclear Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh.
Department of General Surgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
Clin Nucl Med. 2024 Jun 1;49(6):e258-e265. doi: 10.1097/RLU.0000000000005208. Epub 2024 Apr 5.
A monoclonal antibody, trastuzumab, is used for immunotherapy for HER2-expressing breast cancers. Large-sized antibodies demonstrate hepatobiliary clearance and slower pharmacokinetics. A trastuzumab fragment (Fab; 45 kDa) has been generated for theranostic use.
Fab was generated by papain digestion. Trastuzumab and Fab have been radiolabelled with 177 Lu after being conjugated with a bifunctional chelating. The affinity and target specificity were studied in vitro. The first-in-human study was performed.
The bifunctional chelating agent conjugation of 1-2 molecules with trastuzumab and Fab was detected at the molar ratio 1:10 in bicarbonate buffer (0.5 M, pH 8) at 37°-40°C. However, 2-3 molecules of bifunctional chelating agent were conjugated when DMSO in PBS (0.1 M, pH 7) was used as a conjugation buffer at a molar ratio of 1:10. The radiolabelling yield of DOTA-conjugated Fab and trastuzumab at pH 5, 45°C to 50°C, with incubation time 2.5-3 hours was 80% and 41.67%, respectively. However, with DOTAGA-conjugated trastuzumab and Fab, the maximum radiolabelling yield at pH 5.5, 37°C, and at 2.5-3 hours was 80.83% and 83%, respectively. The calculated K d of DOTAGA Fab and trastuzumab with HER2-positive SKBR3 cells was 6.85 ± 0.24 × 10 -8 M and 1.71 ± 0.10 × 10 -8 M, respectively. DOTAGA-Fab and trastuzumab showed better radiolabelling yield at mild reaction conditions.177 Lu-DOTAGA-Fab demonstrated higher lesion uptake and lower liver retention as compared with 177 Lu-DOTAGA-trastuzumab. However, 177 Lu-DOTAGA-Fab as compared with 177 Lu-DOTAGA-trastuzumab showed a relatively early washout (5 days) from the lesion.
177 Lu-DOTAGA-Fab and trastuzumab are suitable for targeting the HER2 receptors.
曲妥珠单抗是一种用于治疗 HER2 表达型乳腺癌的单克隆抗体免疫疗法。大分子量抗体表现出肝胆清除和较慢的药代动力学特性。已经生成了曲妥珠单抗片段（Fab；45 kDa）用于治疗诊断。
Fab 通过木瓜蛋白酶消化生成。曲妥珠单抗和 Fab 与双功能螯合剂缀合后用 177 Lu 放射性标记。在体外研究了亲和力和靶特异性。进行了首例人体研究。
在 37°-40°C 下，在碳酸氢盐缓冲液（0.5 M，pH 8）中，曲妥珠单抗和 Fab 的双功能螯合剂偶联摩尔比为 1:10 时，检测到 1-2 个分子的双功能螯合剂偶联。然而，当使用 PBS 中的 DMSO（0.1 M，pH 7）作为缀合缓冲液时，摩尔比为 1:10 时，偶联了 2-3 个双功能螯合剂分子。在 pH 5、45°C 至 50°C 下，孵育时间为 2.5-3 小时时，DOTA 偶联 Fab 和曲妥珠单抗的放射标记产率分别为 80%和 41.67%。然而，对于 DOTAGA 偶联的曲妥珠单抗和 Fab，在 pH 5.5、37°C 和 2.5-3 小时时，最大放射标记产率分别为 80.83%和 83%。用 HER2 阳性 SKBR3 细胞计算的 DOTAGA-Fab 和曲妥珠单抗的 K d 值分别为 6.85±0.24×10 -8 M 和 1.71±0.10×10 -8 M。在温和的反应条件下，DOTAGA-Fab 和曲妥珠单抗具有更好的放射标记产率。与 177 Lu-DOTAGA-trastuzumab 相比，177 Lu-DOTAGA-Fab 显示出更高的病变摄取和更低的肝脏保留。然而，与 177 Lu-DOTAGA-trastuzumab 相比，177 Lu-DOTAGA-Fab 从病变中显示出相对较早的洗脱（5 天）。
177 Lu-DOTAGA-Fab 和曲妥珠单抗适合靶向 HER2 受体。
