Improved Tumor Targeting of Tc-99m Fab by Chemical Modifications

这个项目是由C.H.开发并指导的。 白博士。我们一直在开发化学方法来 放射性标记单抗及其片段用作 核素显像剂用于检测血液系统恶性肿瘤 表达IL-2a受体的细胞。对于98财年，我们延长了我们的 努力标记基因合成的单链、二硫化物 抗Tac单抗的稳定可变区片段(ScdsFv) 用~(99m)Tc标记的抗体。ScdsFv的生物分布类似于 DsFv，肿瘤摄取快，清除快 来自血液和除肾脏以外的所有器官。以改善其 与其高肾摄取有关的药代动力学特性，我们 通过其酰化反应降低scdsFv的等电点(等电点) 氨基与琥珀酸酐。这个反应中和了一个 ScdsFv的氨基上带正电荷，同时 向dsFv添加一个负电荷。琥珀酸共轭， 等电点为4.4-6.4的TC-99m标记ScdsFv显示肾脏 积累量比对照低三到四倍 TC-99M标记的scdsFv在荷瘤裸鼠体内的研究 肿瘤摄取未受影响。同样，全身滞留 琥珀酸偶联物的产率要低得多。白介素2 受体阳性的ATAC4肿瘤与非肿瘤的比率增加 随着时间的推移，比率为14.0、13.6、7.0、22.8、1.5和0.13 在180分钟的血液中，受体阴性的A431肿瘤，肝脏， 脾、肠、肾。这项研究表明，肾脏 ScdsFv的摄取涉及正极之间的电荷相互作用 带电荷的scdsFv和带负电荷的磷脂双层膜 肾实质细胞膜与PI的降低 会降低肾脏的摄取。总而言之，这项研究表明 肾脏对ScdsFv的高摄取可以通过化学方法来优化 在不影响肿瘤摄取的情况下进行修改。

This project was developed and is directed by C.H. Paik, Ph.D. We have been developing chemical methods to radiolabel monoclonal antibodies and their fragments to use them as scintigraphic imaging agents to detect hematologic malignancies that express IL-2a receptors. For FY '98 we have extended our efforts to label genetically synthesized single chain, disulfide stabilized variable-region fragment (scdsFv) of antiTac monoclonal antibody with Tc-99m. The biodistribution of scdsFv was similar to that of dsFv, with its rapid tumor uptake whereas clearing rapidly from blood and all organs except kidneys. To improve its pharmacokinetic property with respect to its high renal uptake, we lowered the isoelectric point (pI 10) of scdsFv by acylation of its amino groups with succinic anhydride. This reaction neutralizes one positive charge on an amino group of scdsFv and at the same time adds one negative charge to dsFv. The succinic acid conjugated, Tc-99m-labeled scdsFv with a pI range of 4.4-6.4 showed the renal accumulation three to four times lower than that of the control Tc-99m-labeled scdsFv in tumor-bearing nude mice whereas its tumor uptake was not affected. Similarly, the whole-body retention of the succinic acid conjugate was much lower. The IL-2 receptor-positive ATAC4 tumor to non-tumor ratios increased steadily over time with ratios of 14.0, 13.6, 7.0, 22.8, 1.5, and 0.13 at 180 minutes for blood, the receptor-negative A431 tumor, liver, spleen, intestine, and kidney. This study suggests that the renal uptake of scdsFv involves charge interactions between positively charged scdsFv and negatively charged phopholipid bilayers of renal parenchymal cell membranes and that the lowering of the pI decreases the renal uptake. In conclusion, this study indicates that the high renal uptake of scdsFv can be optimized by chemical modifications without compromising tumor uptake.