RESUMO
OBJECTIVE: Adult T-cell leukemia/lymphoma (ATL), caused by human T-cell lymphotropic virus type I (HTLV-1) infection, is among the most aggressive categories and has the worst prognosis among T-cell lymphomas. Mogamulizumab, an anti-CC chemokine receptor 4 (CCR 4), has been shown to be effective in the treatment of ATL; however, some ATL cases are often resistant, particularly the lymphoma-type ATL. To evaluate drug delivery in vivo and identify the distribution of CCR4-positive cells in the body, we developed a novel mogamulizumab tracer labeled with Indium-111 (111In) via diethylenetriaminepentaacetic acid (DTPA) for single-photon emission computerized tomography (SPECT), named [111In]In-DTPA-mogamulizumab, and evaluated its potential for visualizing CCR4 expression in vivo. METHODS: [111In]In-DTPA-mogamulizumab was added to HCT116/CCR4 or HCT116/empty vector (EV) cells, and their radioactivity was measured 1 h after administration. A blocking study was additionally performed by treating HCT116/CCR4 cells with excess mogamulizumab in addition to [111In]In-DTPA-mogamulizumab. The biodistribution and SPECT imaging of [111In]In-DTPA-mogamulizumab in HCT116/CCR4 and HCT116/EV dual-xenografted BALB/c-nu mice were evaluated for 72 h after intravenous injection. RESULTS: [111In]In-DTPA-mogamulizumab was acquired with a radiochemical purity > 95%. The cellular uptake level of [111In]In-DTPA-mogamulizumab by HCT116/CCR4 cells was significantly higher than that by HCT116/EV cells (HCT116/CCR4: 0.951 ± 0.069, HCT116/EV: 0.006 ± 0.001%dose/mg protein, p < 0.01), and the uptake was significantly suppressed by co-incubation with excess mogamulizumab (0.013 ± 0.003%dose/mg protein, p < 0.01). In the in vivo study, the radioactivity of the HCT116/CCR4 tumor tissue was significantly higher than that of the HCT116/EV tumor tissue at 72 h after the administration of [111In]In-DTPA-mogamulizumab (HCT116/CCR4: 20.5 ± 5.4, HCT116/EV: 5.7 ± 1.0%ID/g), and HCT116/CCR4 tumors were clearly and specifically visualized on SPECT imaging. CONCLUSIONS: We have successfully developed a novel SPECT imaging tracer targeting CCR4, [111In]In-DTPA-mogamulizumab, which showed good specificity and pharmacokinetics, indicating potential in visualizing CCR4 expression in vivo.
