Evaluation of an Anti-HER2 Nanobody Labeled with 225Ac for Targeted α-Particle Therapy of Cancer,Molecular Pharmaceutics

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Evaluation of an Anti-HER2 Nanobody Labeled with 225Ac for Targeted α-Particle Therapy of Cancer
Molecular Pharmaceutics ( IF 4.5 ) Pub Date : 2018-03-05 00:00:00 , DOI: 10.1021/acs.molpharmaceut.7b00985
Marek Pruszynski ₁ , Matthias D’Huyvetter ₂ , Frank Bruchertseifer ₃ , Alfred Morgenstern ₃ , Tony Lahoutte _{2,

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Affiliation

Human epidermal growth factor receptor type 2 (HER2) is overexpressed in numerous carcinomas. Nanobodies (Nbs) are the smallest antibody-derived fragments with beneficial characteristics for molecular imaging and radionuclide therapy. Therefore, HER2-targeting nanobodies could offer a valuable platform for radioimmunotherapy, especially when labeled with α-particle emitters, which provide highly lethal and localized radiation to targeted cells with minimal exposure to surrounding healthy tissues. In this study, the anti-HER2 2Rs15d-nanobody was conjugated with 2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (p-SCN-Bn-DOTA) and radiolabeled with an α-emitter ²²⁵Ac with a high yield (>90%) and a radiochemical purity above 95%. The ²²⁵Ac-DOTA-Nb binding affinity was 4.12 ± 0.47 nM with an immunoreactive fraction above 80%. Binding to low HER2-expressing MDA-MB-231 cells was negligible, whereas HER2-overexpressing SKOV-3 cells could be blocked with an excess of unlabeled nanobody, confirming the specificity of binding. Noncompeting binding to HER2 was observed in the presence of an excess of trastuzumab. The cell-associated fraction of ²²⁵Ac-DOTA-Nb was 34.72 ± 16.66% over 24 h. In vitro, the radioconjugate was toxic in an HER2-mediated and dose-dependent manner, resulting in IC₅₀ values of 10.2 and 322.1 kBq/mL for ²²⁵Ac-DOTA-Nb and the ²²⁵Ac-DOTA control, respectively, on SKOV-3 cells, and 282.2 kBq/mL for ²²⁵Ac-DOTA-Nb on MDA-MB-231 cells. Ex vivo biodistribution studies, performed in mice bearing subcutaneous HER2-overexpressing and low HER2-expressing tumors, showed a fast uptake in SKOV-3 tumors compared to MDA-MB-231 (4.01 ± 1.58% ID/g vs 0.49 ± 0.20% ID/g after 2 h), resulting also in high tumor-to-normal tissue ratios. In addition, coinjection of ²²⁵Ac-DOTA-Nb with Gelofusine reduced kidney retention by 70%. This study shows that ²²⁵Ac-DOTA-Nb is a promising new radioconjugate for targeted α-particle therapy and supports its further development.

中文翻译：

²²⁵ Ac标记的抗HER2纳米抗体对癌症靶向α粒子治疗的评价

人类表皮生长因子受体2型（HER2）在许多癌中过表达。纳米抗体（Nbs）是最小的抗体衍生片段，具有用于分子成像和放射性核素治疗的有益特性。因此，靶向HER2的纳米抗体可以为放射免疫疗法提供有价值的平台，尤其是在被α粒子发射器标记时，它可以以最小程度地暴露于周围健康组织的方式向目标细胞提供高致死性和局部辐射。在这项研究中，抗HER2 2Rs15d纳米抗体与2-（4-异硫氰酸根合苄基）-1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸（p -SCN-Bn-DOTA ）共轭。）并用高发射率（> 90％）和放射化学纯度高于95％的α-发射体²²⁵ Ac进行放射性标记。在²²⁵Ac-DOTA-Nb的结合亲和力为4.12±0.47 nM，免疫反应分数高于80％。与表达低HER2的MDA-MB-231细胞的结合可以忽略不计，而表达HER2的SKOV-3细胞可以被过量的未标记纳米抗体阻断，从而证实了结合的特异性。在过量的曲妥珠单抗存在下观察到与HER2的非竞争性结合。²²⁵ Ac-DOTA-Nb的细胞相关分数在24小时内为34.72±16.66％。在体外，放射性结合物以HER2介导且剂量依赖性的方式具有毒性，在SKOV-上，²²⁵ Ac-DOTA-Nb和²²⁵ Ac-DOTA对照的IC ₅₀值分别为10.2和322.1 kBq / mL。3个细胞，对于²²⁵个细胞为282.2 kBq / mLMDA-MB-231细胞上的Ac-DOTA-Nb。在患有皮下表达HER2的过度表达和表达低的HER2的小鼠中进行的离体生物分布研究显示，与MDA-MB-231相比，SKOV-3肿瘤的摄取较快（4.01±1.58％ID / g vs 0.49±0.20％ID / g 2小时后），也导致高的肿瘤与正常组织比率。此外，将²²⁵ Ac-DOTA-Nb与格鲁夫碱共同注射可将肾脏滞留率降低70％。这项研究表明²²⁵ Ac-DOTA-Nb是用于靶向α粒子治疗的有希望的新型放射性偶联物，并支持其进一步的发展。

更新日期：2018-03-05

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