Braun Diana, Judmann Benedikt, Cheng Xia, Wängler Björn, Schirrmacher Ralf, Fricker Gert, Wängler Carmen
Biomedical Chemistry, Clinic of Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany.
Molecular Imaging and Radiochemistry, Clinic of Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany.
ACS Omega. 2023 Jan 4;8(2):2793-2807. doi: 10.1021/acsomega.2c07484. eCollection 2023 Jan 17.
Radiolabeled heterobivalent peptidic ligands (HBPLs) are a highly promising compound class for the sensitive and specific visualization of tumors as they often exhibit superior properties compared to their monospecific counterparts and are able to concomitantly or complementarily address different receptor types. The combination of two receptor-specific agents targeting the epidermal growth factor receptor (EGFR) and the integrin αβ in one HBPL would constitute a synergistic combination of binding motifs as these two receptor types are concurrently overexpressed on several human tumor types and are closely associated with disease progression and metastasis. Here, we designed and synthesized two heterobivalent radioligands consisting of the EGFR-specific peptide GE11 and αβ-specific cyclic RGD peptides, bearing a (1,4,7-triazacyclononane-4,7-diyl)diacetic acid-1-glutaric acid chelator for efficient radiolabeling and linkers of different lengths between both peptides. Both HBPLs were radiolabeled with Ga in high radiochemical yields, purities of 96-99%, and molar activities of 36-88 GBq/μmol. [Ga]Ga- and [Ga]Ga- were evaluated for their log and stability toward degradation by human serum peptidases, showing a high hydrophilicity for both agents of -3.07 ± 0.01 and -3.44 ± 0.08 as well as a high stability toward peptidase degradation in human serum with half-lives of 272 and 237 min, respectively. Further on, the receptor binding profiles of both HBPLs to the target EGF and integrin αβ receptors were assessed on EGFR-positive A431 and αβ-positive U87MG cells. Finally, we investigated the pharmacokinetics of HBPL [Ga]Ga- by positron emission tomography/computed tomography imaging in A431 tumor-bearing xenograft mice to assess its potential for the receptor-specific visualization of EGFR- and/or αβ-expressing tumors. In these experiments, [Ga]Ga- demonstrated a tumor uptake of 2.79 ± 1.66% ID/g, being higher than in all other organs and tissues apart from kidneys and blood at 2 h p.i. Receptor blocking studies revealed the observed tumor uptake to be solely mediated by integrin αβ, whereas no contribution of the GE11 peptide sequence to tumor uptake the EGFR could be determined. Thus, the approach to develop radiolabeled EGFR- and integrin αβ-bispecific HBPLs is in general feasible although another peptide lead structure than GE11 should be used as the basis for the EGFR-specific part of the agents.
放射性标记的异二价肽配体（HBPLs）是一类极具前景的化合物，可用于肿瘤的灵敏且特异性显像，因为与单特异性同类物相比，它们通常具有更优异的特性，并且能够同时或互补地作用于不同的受体类型。在一个HBPL中结合两种分别靶向表皮生长因子受体（EGFR）和整合素αβ的受体特异性试剂，将构成一种结合基序的协同组合，因为这两种受体类型在多种人类肿瘤类型中同时过度表达，并且与疾病进展和转移密切相关。在此，我们设计并合成了两种异二价放射性配体，它们由EGFR特异性肽GE11和αβ特异性环RGD肽组成，带有一个（1,4,7-三氮杂环壬烷-4,7-二基）二乙酸-1-戊二酸螯合剂用于高效放射性标记，以及两种肽之间不同长度的连接子。两种HBPL均以高放射化学产率用镓进行放射性标记，纯度为96 - 99%，摩尔活性为36 - 88 GBq/μmol。评估了[Ga]Ga-和[Ga]Ga-的log 以及对人血清肽酶降解的稳定性，结果显示两种试剂的亲水性都很高，分别为-3.07±0.01和-3.44±0.08，并且在人血清中对肽酶降解具有高稳定性，半衰期分别为272分钟和237分钟。此外，在EGFR阳性的A431细胞和αβ阳性的U87MG细胞上评估了两种HBPL与靶标EGF和整合素αβ受体的受体结合谱。最后，我们通过正电子发射断层扫描/计算机断层扫描成像研究了HBPL [Ga]Ga-在荷A431肿瘤的异种移植小鼠中的药代动力学，以评估其对表达EGFR和/或αβ的肿瘤进行受体特异性显像的潜力。在这些实验中，[Ga]Ga-在注射后2小时显示肿瘤摄取为2.79±1.66% ID/g，除肾脏和血液外，高于所有其他器官和组织。受体阻断研究表明，观察到的肿瘤摄取仅由整合素αβ介导，而无法确定GE11肽序列对EGFR介导的肿瘤摄取有贡献。因此，开发放射性标记的EGFR和整合素αβ双特异性HBPLs的方法总体上是可行的，尽管应该使用不同于GE11的另一种肽先导结构作为试剂中EGFR特异性部分 的基础。
