ENHANCEMENT OF RENAL CLEARANCE OF TC 99M DSFV BY CHEMICAL MODIFICATIONS

工作总结：二硫键稳定的可变区片段(DsFv) 抗Tac单抗以前用~(99m)Tc标记 检测表达IL-2的血液系统恶性肿瘤 2α：受体。TC-99M标记的dsFv已被证明可以快速靶向IL-2 受体阳性的人肿瘤(ATAC4和SP2/Tac)裸鼠移植瘤 虽然它能迅速从血液和大多数器官中清除，因此 导致肿瘤与非肿瘤组织的比率很高。不过，这个 放射性药物主要通过肾脏和肾脏排泄。 肾脏高摄取率(15分钟注射剂量的70%)是一个限制。至 改善这种放射性药物的性能 对于肾脏的高摄取率，已经研究了两种方法：插入 DsFv和放射性标记之间易代谢的酯键和 降低dsFv等电点(等电点10)。第二种方法是 更成功的是：通过结合乙醇酸分子来降低PI DsFv的赖氨酸残基。在1997财年，第二种方法得到了扩展 要测试不同酰化剂的效果，如 乳酸四氟苯酯和丁二酸酐对降脂效果的影响 PI，以及酰化的~(99m)Tc-dsFv的生物分布。 乳酸偶联对等电点的影响与等电点相似 乙醇酸的偶联反应，而与丁二酸的酰化反应 酸酐在降低等电点方面更有效，可能是因为 反应中和了dsFv氨基上的一个正电荷， 同时给dsFv增加一个负电荷。比较 在裸鼠体内的生物分布研究--这些酰化的~(99m)Tc- 具有类似等电点范围(等电点5-7)的标记dsFv制剂，表明 酰化的~(99m)Tc标记的dsFv制剂容易排泄 通过肾脏，肾脏摄取量是 低于~(99m)Tc标记dsFv对照。这项研究表明 肾脏对dsFv的摄取涉及正相互作用 带电荷的dsFv和带负电荷的肾脏磷脂双层 实质细胞膜。这项研究还表明，降低 PI的降低可降低肾摄取。总而言之，这项研究 表明肾脏的高摄取可以通过化学物质来优化。 DsFv的修饰和分子上的微小差异 酰化剂的结构不会引起明显的 肾脏清除量的差异。

Summary of Work: Disulfide stabilized variable-region fragment (dsFv) of anti-Tac monoclonal antibody was previously radiolabeled with Tc-99m to detect scintigraphically hematologic malignancies that express IL- 2alpha: receptors. Tc-99m labeled dsFv has proven to rapidly target IL-2 receptor-positive human tumors (ATAC4 and SP2/Tac) xenografted in nude mice, whereas it cleared rapidly from blood and most organs, thereby resulting in high tumor-to-nontumor tissue ratios. However, this radiopharmaceutical is excreted primarily through the kidneys and its high kidney uptake (70% injected dose at 15 min) was a limitation. To improve the property of this radiopharmaceutical with respect to the high renal uptake, two approaches have been investigated: insertion of readily metabolizable ester bond between dsFv and the radiolabel and lowering isoelectric point (pI 10) of dsFv. The second approach has been more successful: lowering pI by conjugating glycolate molecules to lysine residues of dsFv. During FY 97, the second approach was extended to test the effects of different acylating agents such as tetrafluorophenyl lactate and succinic anhydride on the lowering of the pI and also on the biodistribution of the acylated Tc-99m-labeled dsFv. The effect of the lactate conjugation on the pI was similar to that of the glycolate conjugation, whereas the acylation reaction with succinic anhydride was more efficient in lowering the pI, perhaps because this reaction neutralizes one positive charge on an amino group of dsFv and at the same time adds one negative charge to dsFv. Comparative biodistribution studies in nude mice, between these acylated Tc-99m- labeled dsFv preparations with a similar pI range (pI 5-7), indicate that the acylated Tc-99m-labeled dsFv preparations were excreted readily through the kidneys and that the renal uptake was three to four times lower than that of the control Tc-99m labeled dsFv. This study suggests that the renal uptake of dsFv involves interactions between positively charged dsFv and negatively charged phospholipid bilayers of renal parenchymal cell membranes. The study also indicates that the lowering of the pI decreases the renal uptake. In conclusion, this study indicates that the high renal uptake can be optimized by chemical modifications of dsFv and that a small difference in the molecular structure of the acylating agents does not cause an appreciable difference in renal clearance.