Pijarowska-Kruszyna Justyna, Karczmarczyk Urszula, Jaroń Antoni Włodzimierz, Laszuk Ewa, Radzik Marcin, Garnuszek Piotr, Mikołajczak Renata
National Centre for Nuclear Research, Radioisotope Centre POLATOM, ul. Andrzeja Sołtana 7, 05-400, Otwock -Świerk, Poland.
Nucl Med Rev Cent East Eur. 2017;20(2):88-94. doi: 10.5603/NMR.2017.0014.
Technetium Tc99m Exametazime (99mTc-HMPAO) is currently used as a radiopharmaceutical for determining regional cerebral blood flow and for the labelling of autologous leucocytes for infection and inflammation imaging. The HMPAO ligand exists in two diastereomeric forms: d,l and meso. Usually, the substance is obtained in low chemical yield in a time consuming procedure. Furthermore, the final product still contains some amounts of the meso-form. The aim of this study was to develop the efficient, reliable and fast method for isolation of the d,l-HMPAO, which would provide the ligand with high purity and free from the meso-diastereomer.
The mixture of the meso- and d,l-HMPAO was synthesized in two-steps by condensation of propanediamine with keto-oxime and the reduction of the obtained bisimine. The d- and l-enantiomers were separated individually directly from this mixture by repeated crystallizations from ethanol as their tartrate salts and pooled together in equal proportions. That substance was characterized for its identity and isomeric purity using IR, HPLC and GC methods. The meso-free d,l-HMPAO was used for the preparation of the radiopharmaceutical freeze-dried kit for technetium-99m radiolabelling. Quality assessment of obtained 99mTc-d,l-HMPAO complex was performed according to the current Ph.Eur. monograph 1925 and USP monograph - Technetium Tc99m Exametazime Injection. To verify its biological activity, the kit-prepared 99mTc-d,l-HMPAO has been used for the white blood cell (WBC) labelling.
According to the proposed synthesis route the d,l-HMPAO was obtained with around 18-20% yield in the total time of 10 days. The ligand identity was confirmed and the HPLC analysis revealed more than 99% chemical purity. The undesired meso-form was not detected. Freeze dried kit formulation for 99mTc-labelling of d,l-HMPAO has been established and four batches of kits were manufactured. The radiochemical purity of 99mTc-d,l-HMPAO complex was high (> 95% of lipophilic technetium-99m exametazime). Brain uptake in rats reached 2.1 ± 0.3%. The in vitro labelling of WBC resulted in 68.3 ± 6.6% yield.
A new synthesis method of d,l-HMPAO, drug substance for technetium-99m exametazime preparation has been developed.
锝 Tc99m 依沙美肟（99mTc-HMPAO）目前用作放射性药物，用于测定局部脑血流量以及标记自体白细胞以进行感染和炎症成像。HMPAO 配体存在两种非对映体形式：d,l 型和内消旋型。通常，该物质通过耗时的过程以较低的化学产率获得。此外，最终产物仍含有一定量的内消旋型。本研究的目的是开发一种高效、可靠且快速的方法来分离 d,l-HMPAO，该方法将提供高纯度且不含内消旋非对映体的配体。
通过丙二胺与酮肟缩合以及所得双亚胺的还原，分两步合成内消旋型和 d,l-HMPAO 的混合物。通过从乙醇中反复结晶其酒石酸盐，直接从该混合物中分别分离出 d-和 l-对映体，并按等比例混合在一起。使用红外光谱（IR）、高效液相色谱（HPLC）和气相色谱（GC）方法对该物质进行身份和异构体纯度表征。不含内消旋体的 d,l-HMPAO 用于制备用于锝-99m 放射性标记的放射性药物冻干试剂盒。根据现行欧洲药典专论 1925 和美国药典专论——锝 Tc99m 依沙美肟注射液，对所得 99mTc-d,l-HMPAO 复合物进行质量评估。为验证其生物活性，试剂盒制备的 99mTc-d,l-HMPAO 已用于白细胞（WBC）标记。
按照所提出的合成路线，在 10 天的总时间内以约 18 - 20%的产率获得了 d,l-HMPAO。确认了配体身份，HPLC 分析显示化学纯度超过 99%。未检测到不需要的内消旋型。已建立用于 d,l-HMPAO 的 99mTc 标记的冻干试剂盒配方，并生产了四批试剂盒。99mTc-d,l-HMPAO 复合物的放射化学纯度很高（>95%的亲脂性锝-99m 依沙美肟）。大鼠脑中的摄取率达到 2.1±0.3%。白细胞的体外标记产率为 68.3±6.6%。
已开发出一种新的 d,l-HMPAO 合成方法，d,l-HMPAO 是制备锝-99m 依沙美肟的原料药。
