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Abstract：
BACKGROUND: Both in clinical routine and in preclinical research, the established standard procedure for the final purification of radiometal-labeled peptide radiopharmaceuticals is cartridge-based reversed-phase (RP) solid phase extraction (SPE). It allows the rapid and quantitative separation of the radiolabeled peptide from hydrophilic impurities and easy integration into automated synthesis procedures. However, product elution from RP cartridges necessitates the use of organic solvents and product recovery is sometimes limited. Thus, an alternative purification method based on commercially available size exclusion cartridges was investigated.
RESULTS: Since most peptide radiopharmaceuticals have a molecular weight > 1 kDa, Sephadex G10 cartridges with a molecular size cut-off of 700 Da were used for the final purification of a broad palette of 68Ga-, 64Cu- and 99mTc-labeled experimental peptide radiotracers as well as the clinically relevant ligand PSMA-617. Results (radiochemical purity (RCP, determined by ITLC), recovery from the solid support) were compared to the respective standard RP-SPE method. Generally, retention of unreacted 68Ga, 64Cu and 99mTc salts on the G10 cartridges was quantitative up to the specified elution volume (1.2 mL) for 68Ga and 99mTc and 99.6% for 64Cu. Even at increased elution volumes of 1.5-2 mL, RCPs of the eluted 68Ga- and 99mTc -radiopeptides were > 99%. For all peptides with a molecular weight ≥ 2 kDa, product recovery from the G10 cartridges was consistently > 85% upon respective adjustment of the elution volume. Product recovery was lowest for [68Ga]Ga-PSMA-617 (67%, 1.2 mL to 84%, 2 mL). The pH of the final product solution was found to be volume-dependent (1.2 mL: pH 6.3; 1.5 mL: pH 5.9; 2 mL: pH 5.5). Notably, the G10 cartridges were reused up to 20 times without compromising performance, and implementation of the method in an automated radiosynthesis procedure was successful.
CONCLUSIONS: Overall, size exclusion purification yielded all peptide radiopharmaceuticals in excellent radiochemical purities (> 99%) in saline within 10-12 min. Although product recovery is marginally inferior to classical SPE purifications, this method has the advantage of completely avoiding organic solvents and representing a cost-effective, easy-to-implement purification approach for automated radiotracer synthesis.
RESULTS: Since most peptide radiopharmaceuticals have a molecular weight > 1 kDa, Sephadex G10 cartridges with a molecular size cut-off of 700 Da were used for the final purification of a broad palette of 68Ga-, 64Cu- and 99mTc-labeled experimental peptide radiotracers as well as the clinically relevant ligand PSMA-617. Results (radiochemical purity (RCP, determined by ITLC), recovery from the solid support) were compared to the respective standard RP-SPE method. Generally, retention of unreacted 68Ga, 64Cu and 99mTc salts on the G10 cartridges was quantitative up to the specified elution volume (1.2 mL) for 68Ga and 99mTc and 99.6% for 64Cu. Even at increased elution volumes of 1.5-2 mL, RCPs of the eluted 68Ga- and 99mTc -radiopeptides were > 99%. For all peptides with a molecular weight ≥ 2 kDa, product recovery from the G10 cartridges was consistently > 85% upon respective adjustment of the elution volume. Product recovery was lowest for [68Ga]Ga-PSMA-617 (67%, 1.2 mL to 84%, 2 mL). The pH of the final product solution was found to be volume-dependent (1.2 mL: pH 6.3; 1.5 mL: pH 5.9; 2 mL: pH 5.5). Notably, the G10 cartridges were reused up to 20 times without compromising performance, and implementation of the method in an automated radiosynthesis procedure was successful.
CONCLUSIONS: Overall, size exclusion purification yielded all peptide radiopharmaceuticals in excellent radiochemical purities (> 99%) in saline within 10-12 min. Although product recovery is marginally inferior to classical SPE purifications, this method has the advantage of completely avoiding organic solvents and representing a cost-effective, easy-to-implement purification approach for automated radiotracer synthesis.
摘要：
背景：在临床常规和临床前研究中，放射性金属标记的肽放射性药物最终纯化的既定标准程序是基于柱体的反相(RP)固相萃取(SPE).它允许从亲水性杂质中快速和定量分离放射性标记的肽,并且易于整合到自动化合成程序中。然而,从RP柱的产品洗脱需要使用有机溶剂和产品回收有时是有限的。因此，研究了一种基于市售尺寸排阻盒的替代纯化方法.
结果：由于大多数肽放射性药物的分子量>1kDa，分子大小截止值为700Da的SephadexG10药筒用于68Ga-的宽调色板的最终纯化，64Cu-和99mTc-标记的实验肽放射性示踪剂以及临床相关配体PSMA-617。结果(放射化学纯度(RCP，由ITLC确定)，从固体支持物的回收率）与相应的标准RP-SPE方法进行比较。一般来说,未反应的68Ga的保留，对于68Ga和99mTc,G10柱上的64Cu和99mTc盐是定量的,直到指定的洗脱体积(1.2mL),对于64Cu是99.6%。即使在增加1.5-2毫升的洗脱体积，洗脱的68Ga-和99mTc-放射性肽的RCP>99%。对于分子量≥2kDa的所有肽，在相应调整洗脱体积后,来自G10柱的产物回收率始终>85%。[68Ga]Ga-PSMA-617的产品回收率最低(67%，1.2毫升至84%，2mL)。发现最终产物溶液的pH是体积依赖性的(1.2mL:pH6.3;1.5mL:pH5.9;2mL:pH5.5)。值得注意的是,在不影响性能的情况下，G10墨盒可重复使用多达20次，并且该方法在自动放射合成程序中的实施是成功的。
结论：总体而言，尺寸排阻纯化在10-12分钟内产生了在盐水中具有优异的放射化学纯度(>99%)的所有肽放射性药物。尽管产品回收率略低于经典的SPE纯化，该方法具有完全避免有机溶剂的优点，并且具有成本效益，易于实施的自动化放射性示踪剂合成纯化方法。
结果：由于大多数肽放射性药物的分子量>1kDa，分子大小截止值为700Da的SephadexG10药筒用于68Ga-的宽调色板的最终纯化，64Cu-和99mTc-标记的实验肽放射性示踪剂以及临床相关配体PSMA-617。结果(放射化学纯度(RCP，由ITLC确定)，从固体支持物的回收率）与相应的标准RP-SPE方法进行比较。一般来说,未反应的68Ga的保留，对于68Ga和99mTc,G10柱上的64Cu和99mTc盐是定量的,直到指定的洗脱体积(1.2mL),对于64Cu是99.6%。即使在增加1.5-2毫升的洗脱体积，洗脱的68Ga-和99mTc-放射性肽的RCP>99%。对于分子量≥2kDa的所有肽，在相应调整洗脱体积后,来自G10柱的产物回收率始终>85%。[68Ga]Ga-PSMA-617的产品回收率最低(67%，1.2毫升至84%，2mL)。发现最终产物溶液的pH是体积依赖性的(1.2mL:pH6.3;1.5mL:pH5.9;2mL:pH5.5)。值得注意的是,在不影响性能的情况下，G10墨盒可重复使用多达20次，并且该方法在自动放射合成程序中的实施是成功的。
结论：总体而言，尺寸排阻纯化在10-12分钟内产生了在盐水中具有优异的放射化学纯度(>99%)的所有肽放射性药物。尽管产品回收率略低于经典的SPE纯化，该方法具有完全避免有机溶剂的优点，并且具有成本效益，易于实施的自动化放射性示踪剂合成纯化方法。
