Guleria Mohini, Das Tapas, Kumar Chandan, Sharma Rohit, Amirdhanayagam Jeyachitra, Sarma Haladhar D, Dash Ashutosh
Radiopharmaceuticals Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India.
Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094, India.
Anticancer Agents Med Chem. 2018;18(1):146-153. doi: 10.2174/1871520617666170725164530.
Monoclonal antibodies (mAbs) have been radiolabeled with a variety of radioisotopes utilizing various kinds of bi-functional chelating agents (BFCAs) with an aim to develop suitable agents for radioimmunotherapy. The number of BFCA moieties present per antibody molecule plays a significant role in determining the pharmacokinetics and immunoreactivity exhibited by the radiolabeled antibodies. The objective of the present study is to evaluate the effect of the number of BFCA moieties present per antibody molecule on the pharmacokinetics and immunoreactivity of the 177Lu-labeled Rituximab.
Three different mAb-BFCA conjugates were prepared using different molar ratios of Rituximab (mAb) to p-NCS-benzyl-DOTA (BFCA) viz. 1:5, 1:10 and 1:50 employing different reaction conditions. Studies were carried out to determine the average number of BFCAs attached per mAb molecule. All the three mAb-BFCA conjugates were labeled with 177Lu(III) and were subsequently evaluated in normal Swiss mice to ascertain their respective pharmacokinetic behavior. In-vitro studies were also performed in Raji cell lines (human burkitt's lymphoma) for determining the effect of increasing number of BFCAs attached per mAb molecule on the immunoreactivity of the resultant 177Lu-labeled mAb-BFCA complexes.
177Lu-labeled mAb-BFCA complex prepared corresponding to 1:50 mAb to BFCA ratio exhibited the least non-specific uptake and rapid clearance from majority of the organs, but also exhibited least immunoreactive fraction (IRF = 19.37%). On the other hand, 177Lu-labeled mAb-BFCA complex prepared corresponding to 1:5 mAb to BFCA ratio exhibited the highest non-specific uptake and slower clearance pattern, but highest IRF (71.17%). 177Lu-labeled mAb-BFCA complex prepared corresponding to 1:10 mAb:BFCA ratio exhibited intermediate pharmacokinetic behaviour with moderate IRF (53.05%).
The present study indicates that antibody to BFCA ratio plays a crucial role in determining the immunoreactivity and pharmacokinetic behavior of the radiolabeled antibodies and must be prudently chosen for their successful therapeutic application.
利用各种双功能螯合剂（BFCA）将单克隆抗体（mAb）用多种放射性同位素进行放射性标记，旨在开发适用于放射免疫治疗的药物。每个抗体分子上存在的BFCA部分的数量在决定放射性标记抗体所表现出的药代动力学和免疫反应性方面起着重要作用。本研究的目的是评估每个抗体分子上存在的BFCA部分的数量对177Lu标记的利妥昔单抗的药代动力学和免疫反应性的影响。
使用不同摩尔比的利妥昔单抗（mAb）与对-NCS-苄基-DOTA（BFCA），即1:5、1:10和1:50，采用不同反应条件制备三种不同的mAb-BFCA缀合物。进行研究以确定每个mAb分子上连接的BFCA的平均数量。所有三种mAb-BFCA缀合物都用177Lu(III)进行标记，随后在正常瑞士小鼠中进行评估，以确定它们各自的药代动力学行为。还在Raji细胞系（人伯基特淋巴瘤）中进行了体外研究，以确定每个mAb分子上连接的BFCA数量增加对所得177Lu标记的mAb-BFCA复合物免疫反应性的影响。
对应于1:50 mAb与BFCA比例制备的177Lu标记的mAb-BFCA复合物表现出最少的非特异性摄取和从大多数器官的快速清除，但免疫反应分数也最低（IRF = 19.37%）。另一方面，对应于1:5 mAb与BFCA比例制备的177Lu标记的mAb-BFCA复合物表现出最高的非特异性摄取和较慢的清除模式，但免疫反应分数最高（71.17%）。对应于1:10 mAb:BFCA比例制备的177Lu标记的mAb-BFCA复合物表现出中等的药代动力学行为，免疫反应分数适中（53.05%）。
本研究表明，抗体与BFCA的比例在决定放射性标记抗体的免疫反应性和药代动力学行为方面起着关键作用，为其成功的治疗应用必须谨慎选择。
