¹³¹ I Mark DR5 Antibody Zaptuzumab

Background:Death receptor5(DR5) monoclonal antibody can activate DR5resulting in specific apoptosis of tumor cells. The imaging of a newly developed DR5chimeric human-mouse monoclonal antibody zaptuzumab with binding activity to tumor cells in vivo is helpful to characterize the targeting property of the antibody.Methods:zaptuzumab antibody was labeled with131I by chloramine T method. The labeling yield was determined by instant thin-layer chromatography.131I-zaptuzumab was purified by size exclusion chromatography. The stability of131I-zaptuzumab was tested in saline at37℃. The binding activity of131I-zaptuzumab to DR5was tested with several kinds of carcinoma cells. The planar imaging was carried out at6,30,58h time-points after131I-zaptuzumab administration via tail vein in lung cancer A549xenografted nude mice to characterize the targeting property of the antibody. The mice imaged at6h after131I-zaptuzumab administration were sacrificed to remove tumor, organs and tissues for weight weighing and radioactivity counting to confirm the biodistribution of131I-zaptuzumab in A549xenografted mice, zaptuzumab was labeled with99mTc by Hynic (succinimidyl6-hydrazinonicotinate) method. The labeling yield was determined by instant thin-layer chromatography.99mTc-zaptuzumab was purified by size exclusion chromatography. The binding activity of99mTc-zaptuzumab to DR5was tested by enzyme-linked immunosorbent assay (ELISA). The planar imaging in subcutaneously implanted H460lung cancer models was carried out to characterize the lung cancer-targeting property of99mTc-zaptuzumab. zaptuzumab was labeled with68Ga by NOTA method. The labeling yield was determined by instant thin-layer chromatography.68Ga-zaptuzumab was purified by size exclusion chromatography. The planar imaging in subcutaneously implanted A549lung cancer models was carried out to characterize the lung cancer-targeting property of68Ga-zaptuzumab.Results:The labeling yield of131I-zaptuzumab was above98%. The radiochemical purity of131I-zaptuzumab in saline within3d was above93%。The percentage of competitive binding inhibition of nonradiolabeled zaptuzumab to131I-zaptuzumab was above40%. Planar imaging indicated that131I-zaptuzumab accumulated in A549xenograft at6,30,58h time-points after131I-zaptuzumab administration. Biodistribution studies found that the percentage injected dose per gram tumor was2.95%ID/g in A549xenograft at6h time-points after131I-zaptuzumab administration which is higher than background tissues such as lung, bone, muscle and heart.The labeling yield of99mTc-zaptuzumab was above50%. The radiochemical purity of99mTc-zaptuzumab after purification was above95%。ELISA data indicated that the binding activity of99mTc-zaptuzumab was largely retained. Planar imaging indicated that the accumulation of99mTc-zaptuzumab in H460xenograft at1.5,4.5h time-points after administration was relatively low. The labeling yield of68Ga-zaptuzumab was above50%. The radiochemical purity of68Ga-zaptuzumab after purification was above95%. Planar imaging indicated that68Ga-zaptuzumab accumulated in A549xenograft at1.5h time-point after administration.Conclusion:The labeling yield of131I-zaptuzumab by chloramine T method was high. The stability and biological activity of131I-zaptuzumab were well kept in vitro. A549xenografted in nude mice was visualized with131I-zaptuzumab.The labeling of99mTc-zaptuzumab by Hynic method was successful and the antigen-binding activity of99mTc-zaptuzumab was retained. However, the targeting property of99mTc-zaptuzumab to H460lung cancer was poor. The labeling of68Ga-zaptuzumab by NOTA method was successful.68Ga-zaptuzumab can target A549lung cancer in vivo.