Fragmentation of Nimotuzumab for Preparation of 125I-F(ab’)2-Nimotuzumab as a Precursor for Preparing 125I-F(ab’)2-Nimotuzumab-NLS Radiopharmaceutical for Cancer Therapy

Abstract

Nimotuzumab is an anticancer agent which belongs to the inhibitor group of Epidermal Growth Factor Receptor (EGFR). Thismonoclonal antibody has a relatively high molecular weight which slowspenetration on tumor cells, making it less attractive in imaging kinetics and potentially elicits antibodies responses. Therefore, in this study nimotuzumab was fragmented to form a bivalent antibody [F(ab’)₂] and then labeled with ¹²⁵I to form ¹²⁵I-F(ab’)₂-nimotuzumab which can be used further as a precursor for preparing ¹²⁵I-F(ab’)₂-nimotuzumab-NLS(NLS = nuclear localization sequence) radiopharmaceuticalfor radioimmunotherapy. The aims of this study was to obtain  characteristics of ¹²⁵I-F(ab’)₂-nimotuzumab by comparing with the ¹²⁵I labeled-intact nimotuzumab (¹²⁵I-nimotuzumab). This study was initiated by purifying nimotuzumab by mean of dialysis. The purified nimotuzumab was then fragmented by using pepsin. The F(ab')₂-nimotuzumab formed was then purified from its by-products which formed in fragmentation process by using a PD-10 column (consisted Sephadex G25). The intact nimotuzumab and its F(ab’)₂ fragment were then labeled with the ¹²⁵I to form ¹²⁵I-nimotuzumab and ¹²⁵I-F(ab’)₂-nimotuzumab. The radiochemical purity are 98.27 % and 93.24 %, respectively. Stability test results show that, both ¹²⁵I-nimotuzumab and ¹²⁵I-F(ab’)₂-nimotuzumab are more stable at 4 °C than at room temperature storage and 37 °C.

Received: 24 May 2013; Revised: 21 February 2014; Accepted: 28 February 2014