*3.2. Pre-Clinical Studies*

In the early studies on RIT, the <sup>67</sup>Cu labeled radioimmunoconjugate, <sup>67</sup>Cu-2IT-BAT-Lym-1, was prepared by conjugating the bifunctional TETA derivative BAT to antibody Lym-1, monoclonal antibody against human B cell lymphoma, via 2-iminothiolane (2IT). This modification did not significantly alter immunoreactivity of the antibody [90]. Nude mice bearing human Burkitt's lymphoma (Raji) xenografts treated with <sup>67</sup>Cu-2IT-BAT-Lym-1 achieved high rates of response and cure with modest toxicity [91]. In the pre-clinical radioimmunotherapy comparison with another antibody conjugate, BAT-2IT-IA3, the therapeutic effect of <sup>67</sup>Cu was similar to that of <sup>64</sup>Cu [92].

Searching for optimal radiocopper labeling of anti-L1-CAM antibody chCE7, five bifunctional copper chelators were synthesized and characterized (CPTA-*N*-hydroxysuccinimide, DO3A-L-p-isothiocyanato-phenylalanine, DOTA-PA-L-p-isocyanato-phenylalanine, DOTAglycyl-L-p-isocyanato-phenylalanine and DOTA-triglycyl-L-p-isocyanato-phenylalanine). CPTA-labeled antibody achieved the best tumor to normal tissue ratios when biodistributions of the different <sup>67</sup>Cu-chCE7 conjugates were assessed in tumor-bearing mice. High resolution PET imaging with <sup>64</sup>Cu-CPTA-labeled MAb chCE7 showed uptake in lymph nodes and heterogeneous distribution in tumor xenografts [93]. The therapeutic value of <sup>67</sup>Cu was also demonstrated pre-clinically in the treatment of bladder cancer [94]. It has been demonstrated that the chelator makes the difference in the behavior of conjugates [95]; therefore, new chelator/biological vector compositions are under investigation.

In recent years, new inputs came from the use of the cage ligand, sarcophagine-like (Sar), as a chelator for <sup>67</sup>Cu. The studies on <sup>67</sup>Cu-CuSarTATE, a somatostatin receptor targeting ligand and sarcophagine-containing PSMA ligand, labeled either with <sup>64</sup>Cu- or <sup>67</sup>Cu, supported translation of these radiopharmaceuticals to the clinics [96–99].
