^(99m)Tc直接法标记单抗3H11及其初步临床应用

One step method labeling monoclonal antibody 3H11 with ^(99m)Tc and its preliminary application

为了提高放免显像的准确性和图像的分辨率,采用改进的Schwartz法进行^(99m)Tc标记抗胃癌单克隆抗体3H11的研究。还原剂2-巯基乙醇相对抗体过量1000倍摩尔比,室温反应30分钟,每个抗体分子暴露的巯基数约为2.3个。标记抗体的标记率>95%,最大标记比活度为2.2GBq/mg 3H11,用ELISA法测得的免疫活性>80%。高压液相色谱及体外竞争结合分析证实^(99m)Tc结合在抗体分子的高亲和结合位上。荷瘤裸鼠实验表明:注射^(99m)Tc-3H11 24小时后,除肾外,肿瘤中放射性最高,瘤/血比值>1.5,瘤/肝比值>2.5;2小时后肿瘤γ显像清晰,本底干扰较小。初步临床应用显示,^(99m)Tc-3H11体内稳定性好,能较好地定位于肿瘤病灶。

PURPOSE In order to improve the accuracy of radioimmunoimaging and its image resolution, a modified Schwartz method was studied to prepare ^(99m)Tc labeled anti-gastric cancer monoclonal antibody 3H11. METHODS The antibody was incubated with a 1 000-fold molar excess of 2-meraptoethanol (2-ME) for 30min at room temperature. The pre-antibody was mixed up with 1.1GBq of ^(99m)Tc, glucoheptonate and SnCl_2 at pH 7.2 buffer solution for 20～30min. RESULTS The mean labeling efficiency of the labeled antibody was over 95%. The immunoreactivity of ^(99m)Tc-3H11 was 80 % by ELISA method. The competition test in vitro showed that ^(99m)Tc bind with the high affinity sites of antibody. The biodistribution showed that the radioactivity of tumor uptake at 24h postinjection was the highest. The tumor uptake was 8.98±2.42% ID/g. The ratio of tumor to blood was over 1.5 and that of tumor to liver was more than 2.5 at 24h postinjection. The tumor was clearly visualized at 22h postinjection. Initial clinical results showed that ^(99m)Tc-3H11 was stable in vivo and can well concentrated in the lesion sites. CONCLUSIONS The direct labeling method applied to the preparation of 99mTc labeled antibody 3H11 was successful. ^(99m)Tc-3H11 is worthy of further clinical investigation.