Molecular Imaging of Radiolabeled Bispecific T-Cell Engager 89Zr-AMG211 Targeting CEA-Positive Tumors.

Purpose: AMG 211, a bispecific T-cell engager (BiTE) antibody construct, targets carcinoembryonic antigen (CEA) and the CD3 epsilon subunit of the human T-cell receptor. AMG 211 was labeled with zirconium-89 (89Zr) or fluorescent dye to evaluate the tumor-targeting properties.Experimental Design: 89Zr-AMG211 was administered to mice bearing CEA-positive xenograft tumors of LS174T colorectal adenocarcinoma or BT474 breast cancer cells, as well as CEA-negative HL-60 promyelocytic leukemia xenografts. Biodistribution studies with 2- to 10-µg 89Zr-AMG211 supplemented with unlabeled AMG 211 up to 500-µg protein dose were performed. A BiTE that does not bind CEA, 89Zr-Mec14, served as a negative control. 89Zr-AMG211 integrity was determined in tumor lysates ex vivo Intratumoral distribution was studied with IRDye800CW-AMG211. Moreover, 89Zr-AMG211 was manufactured according to Good Manufacturing Practice (GMP) guidelines for clinical trial NCT02760199Results: 89Zr-AMG211 demonstrated dose-dependent tumor uptake at 6 hours. The highest tumor uptake was observed with a 2-µg dose, and the lowest tumor uptake was observed with a 500-µg dose. After 24 hours, higher uptake of 10-µg 89Zr-AMG211 occurred in CEA-positive xenografts, compared with CEA-negative xenografts. Although the blood half-life of 89Zr-AMG211 was approximately 1 hour, tumor retention persisted for at least 24 hours. 89Zr-Mec14 showed no tumor accumulation beyond background level. Ex vivo autoradiography revealed time-dependent disintegration of 89Zr-AMG211. 800CW-AMG211 was specifically localized in CEA-expressing viable tumor tissue. GMP-manufactured 89Zr-AMG211 fulfilled release specifications.Conclusions: 89Zr-AMG211 showed dose-dependent CEA-specific tumor targeting and localization in viable tumor tissue. Our data enabled its use to clinically evaluate AMG 211 in vivo behavior. Clin Cancer Res; 24(20); 4988-96. ©2018 AACR.

Human Epidermal Growth Factor Receptor 3-Specific Tumor Uptake and Biodistribution of 89Zr-MSB0010853 Visualized by Real-Time and Noninvasive PET Imaging.

The human epidermal growth factor receptor 3 (HER3) is an interesting target for antitumor therapy. For optimal HER3 signaling inhibition, a biparatopic Nanobody construct (MSB0010853) was developed that binds 2 different HER3 epitopes. In addition, MSB0010853 contains a third HER3 epitope that binds albumin to extend its circulation time. MSB0010853 is cross-reactive with HER3 and albumin of mouse origin. We aimed to gain insight into MSB0010853 biodistribution and tumor uptake by radiolabeling the Nanobody construct with 89Zr. Methods: MSB0010853 was radiolabeled with 89Zr. Dose- and time-dependent tumor uptake was studied in nude BALB/c mice bearing a subcutaneous HER3 overexpressing H441 non-small cell lung cancer xenograft. Dose-dependent biodistribution of 89Zr-MSB0010853 was assessed ex vivo at 24 h after intravenous injection. Protein doses of 5, 10, 25, 100, and 1,000 µg were used. Time-dependent biodistribution of MSB0010853 was analyzed ex vivo at 3, 6, 24, and 96 h after intravenous administration of 25 µg of 89Zr-MSB0010853. PET imaging and biodistribution were performed 24 h after administration of 25 µg of 89Zr-MSB0010853 to mice bearing human H441, FaDu (high HER3 expression), or Calu-1 (no HER3 expression) tumor xenografts. Results: Radiolabeling of MSB0010853 with 89Zr was performed with a radiochemical purity of greater than 95%. Ex vivo biodistribution showed protein dose- and time-dependent distribution of 89Zr-MSB0010853 in all organs. Uptake of 89Zr-MSB0010853 in H441 tumors was only time-dependent. Tumor could be visualized up to at least 96 h after injection. The highest mean SUV of 0.6 ± 0.2 was observed at 24 h after injection of 25 µg of 89Zr-MSB0010853. 89Zr-MSB0010853 tumor uptake correlated with HER3 expression and was highest in H441 (6.2 ± 1.1 percentage injected dose per gram [%ID/g]) and lowest in Calu-1 (2.3 ± 0.3 %ID/g) xenografts. Conclusion:89Zr-MSB0010853 organ distribution and tumor uptake in mice are time-dependent, and tumor uptake correlates with HER3 expression. In contrast to tumor uptake except for kidney uptake, organ distribution of 89Zr-MSB0010853 is protein dose-dependent for the tested doses. 89Zr-MSB0010853 PET imaging gives insight into the in vivo behavior of MSB0010853.

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.