Biodistribution and PET Imaging of Labeled Bispecific T Cell-Engaging Antibody Targeting EpCAM.

UNLABELLED: AMG 110, a bispecific T cell engager (BiTE) antibody construct, induces T cell-mediated cancer cell death by cross-linking epithelial cell adhesion molecule (EpCAM) on tumor cells with a cluster of differentiation 3 ε (CD3ε) on T cells. We labeled AMG 110 with (89)Zr or near-infrared fluorescent dye (IRDye) 800CW to study its tumor targeting and tissue distribution. METHODS: Biodistribution and tumor uptake of (89)Zr-AMG 110 was studied up to 6 d after intravenous administration to nude BALB/c mice bearing high EpCAM-expressing HT-29 colorectal cancer xenografts. Tumor uptake of (89)Zr-AMG 110 was compared with uptake in head and neck squamous cell cancer FaDu (intermediate EpCAM) and promyelocytic leukemia HL60 (EpCAM-negative) xenografts. Intratumoral distribution in HT-29 tumors was studied using 800CW-AMG 110. RESULTS: Tumor uptake of (89)Zr-AMG 110 can be clearly visualized using small-animal PET imaging up to 72 h after injection. The highest tumor uptake of (89)Zr-AMG 110 at the 40-µg dose level was observed at 6 and 24 h (respectively, 5.35 ± 0.22 and 5.30 ± 0.20 percentage injected dose per gram; n = 3 and 4). Tumor uptake of (89)Zr-AMG 110 was EpCAM-specific and correlated with EpCAM expression. 800CW-AMG 110 accumulated at the tumor cell surface in viable EpCAM-expressing tumor tissue. CONCLUSION: PET and fluorescent imaging provided real-time information about AMG 110 distribution and tumor uptake in vivo. Our data support using (89)Zr and IRDye 800CW to evaluate tumor and tissue uptake kinetics of bispecific T cell engager antibody constructs in preclinical and clinical settings.

Barriers to achieving commercial success for diagnostic and therapeutic radiopharmaceuticals.

The concluding session of this workshop focused on barriers that might be impeding the successful transition of radiopharmaceuticals from research tools to diagnostics and therapeutics that reach commercial success. Some lessons can be learned by reviewing the technology adoption life cycle as described by Geoffrey A. Moore (Moore, GA. Crossing the chasm. New York: HarperCollins, 2002). Additionally, a review of highly successful radiopharmaceuticals suggests that achieving commercial success may require advocacy by other interested groups.

Antilymphoma treatments given subsequent to Yttrium 90 ibritumomab tiuxetan are feasible in patients with progressive non-Hodgkin's lymphoma: a review of the literature.

Yttrium 90-labeled ibritumomab tiuxetan is approved for the treatment of patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma (NHL). To date, the efficacy of repeated courses of radioimmunoconjugate treatment in patients whose disease has progressed has not been studied as a formal endpoint in a clinical trial setting. However, several clinical studies have been conducted in patients with progressive NHL who had previously received 90Y ibritumomab tiuxetan. A retrospective review of these studies has shown that clinical responses have been achieved with all types of subsequent treatment with no apparent impact on their efficacy. In addition, no significant differences in toxicities with subsequent therapies have been observed between patients who had previously received 90Y ibritumomab tiuxetan therapy and those who had not. These findings suggest that patients previously treated with 90Y ibritumomab tiuxetan can feasibly undergo other forms of treatment for progressive NHL, and that a clinical response to further treatment options is not precluded by administration of 90Y ibritumomab tiuxetan.