Functionally Versatile and Highly Stable Chelator for <sup>111</sup>In and <sup>177</sup>Lu: Proof-of-Principle Prostate-Specific Membrane Antigen Targeting
作者:Lily Li、María de Guadalupe Jaraquemada-Peláez、Hsiou-Ting Kuo、Helen Merkens、Neha Choudhary、Katrin Gitschtaler、Una Jermilova、Nadine Colpo、Carlos Uribe-Munoz、Valery Radchenko、Paul Schaffer、Kuo-Shyan Lin、François Bénard、Chris Orvig
DOI:10.1021/acs.bioconjchem.9b00225
日期:2019.5.15
Here, we present the synthesis and characterization of a new potentially nonadentate chelator H4pypa and its bifunctional analogue tBu4pypa-C7-NHS conjugated to prostate-specific membrane antigen (PSMA)-targeting peptidomimetic (Glu-urea-Lys). H4pypa is very functionally versatile and biologically stable. Compared to the conventional chelators (e.g., DOTA, DTPA), H4pypa has outstanding affinities for both 111In (EC, t1/2 ≈ 2.8 days) and 177Lu (β–,γ, t1/2 ≈ 6.64 days). Its radiolabeled complexes were achieved at >98% radiochemical yield, RT within 10 min, at a ligand concentration as low as 10–6 M, with excellent stability in human serum over at least 5–7 days (<1% transchelation). The thermodynamic stabilities of the [M(pypa)]− complexes (M3+ = In3+, Lu3+, La3+) were dependent on the ionic radii, where the smaller In3+ has the highest pM value (30.5), followed by Lu3+ (22.6) and La3+ (19.9). All pM values are remarkably higher than those with DOTA, DTPA, H4octapa, H4octox, and H4neunpa. Moreover, the facile and versatile bifunctionalization enabled by the p-OH group in the central pyridyl bridge of the pypa scaffold (compound 14) allows incorporation of a variety of linkers for bioconjugation through easy nucleophilic substitution. In this work, an alkyl linker was selected to couple H4pypa to a PSMA-targeting pharmacophore, proving that the bioconjugation sacrifices neither the tumor-targeting nor the chelation properties. The biodistribution profiles of 111In- and 177Lu-labeled tracers are different, but promising, with the 177Lu analogue particularly outstanding.
在这里,我们介绍了一种新的潜在非附着性螯合剂 H4pypa 及其与前列腺特异性膜抗原(PSMA)靶向拟肽(Glu-urea-Lys)共轭的双功能类似物 tBu4pypa-C7-NHS的合成和表征。H4pypa 功能多样,生物性质稳定。与传统的螯合剂(如 DOTA、DTPA)相比,H4pypa 对 111In(EC,t1/2 ≈ 2.8 天)和 177Lu(β-,γ,t1/2 ≈ 6.64 天)都具有出色的亲和力。在配体浓度低至 10-6 M 的情况下,其放射性标记复合物的放射化学收率大于 98%,RT 在 10 分钟内完成,在人血清中的稳定性极佳,至少可维持 5-7 天(转切率小于 1%)。M(pypa)]- 复合物(M3+ = In3+、Lu3+、La3+)的热力学稳定性取决于离子半径,其中较小的 In3+ 的 pM 值最高(30.5),其次是 Lu3+(22.6)和 La3+(19.9)。所有 pM 值都明显高于 DOTA、DTPA、H4octapa、H4octox 和 H4neunpa。此外,pypa 支架(化合物 14)中央吡啶桥上的 p-OH 基团可实现简便而多用途的双官能化,通过简单的亲核取代,可加入多种连接体进行生物连接。在这项工作中,我们选择了一种烷基连接物将 H4pypa 与 PSMA 靶向药源结合,证明生物结合既不会牺牲肿瘤靶向性,也不会牺牲螯合特性。111In和177Lu标记的示踪剂的生物分布特征各不相同,但前景看好,其中177Lu类似物尤为突出。