PT  - JOURNAL ARTICLE
AU  - Sho Koyasu
AU  - Yoichi Shimizu
AU  - Mari Suzukida
AU  - Takero Shindo
AU  - Masahiro Ono
AU  - Yuji Nakamoto
TI  - Development of a novel radiotracer for imaging T cell lymphoma: <sup>111</sup>In-DTPA-Mogamulizumab
DP  - 2021 May 01
TA  - Journal of Nuclear Medicine
PG  - 63--63
VI  - 62
IP  - supplement 1
4099  - http://jnm.snmjournals.org/content/62/supplement_1/63.short
4100  - http://jnm.snmjournals.org/content/62/supplement_1/63.full
SO  - J Nucl Med2021 May 01; 62
AB  - 63Objectives: T-cell lymphomas are one of the most aggressive categories even among hematologic malignancies and can involve blood/bone marrow, lymph nodes, skin, or multiple organs. Recently, the anti-CCR4 antibody mogamulizumab has been showing striking results especially for adult T-cell leukemia/lymphoma (ATLL), which is common in Japan, the Caribbean, South and Central America, and Africa [1]. However, some cases are resistant to mogamulizumab. In addition, it sometimes causes serious adverse events such as fatal graft-versus-host disease. Thus, it is definitely needed that the treatment response of mogamulizumab can be predicted more precisely [2]. Given that its efficacy is not closely correlated with CCR4 expression levels on tumor cells, the mechanism for the discrepancy between CCR4 expression levels and the outcome has been largely unknown. Therefore, we aimed to develop the 111In-labeled SPECT tracer 111In-DTPA-Mogamulizumab with a high affinity for CCR4 for estimating the CCR4 expression in the tumor cells. Methods: Mogamulizumab was first reacted with p-SCN-Bn-DTPA at room temperature (r.t.) for 90 min, and then DTPA-Mogamulizumab was acquired by purifying the reactant using a size-exclusion column. [111In]InCl3 was pre-incubated in acetate buffer (0.1 M, pH 5.4) at r.t. for 15 min, and then DTPA-Mogamulizumab was added and incubated at r.t. for 60 min. The reactant was purified by size-exclusion column to acquire 111In-DTPA-Mogamulizumab. The radiochemical purity of 111In-DTPA-Mogamulizumab was measured by size-exclusion HPLC analysis. In the in vitro study, 111In-DTPA-Mogamulizumab was added to ATL43T cell, ED (-) cell, HCT116 cell stably transfected with human CCR4 expression vector (HCT116/CCR4), and negative control cells (HCT116/EV), and incubated at 37 °C in a humidified atmosphere containing 5% CO2. As for the blocking group, 111In-DTPA-Mogamulizumab containing excess non-labeled mogamulizumab was added. After 1 h of incubation, the cells were lysed with 1 N NaOH, and then the radioactivity and protein concentration of the lysates were measured. In the in vivo biodistribution study, 111In-DTPA-Mogamulizumab was injected intravenously to Balb/c-nu mice inoculated with HCT116/CCR4 cell and HCT116/EV cell at the right and left hind legs respectively (Fig. 1). The tumors and other organs were excised at 24, 48, and 72 h after injection, and their radioactivities and weights were measured. In the SPECT study, 111In-DTPA-Mogamulizumab was injected intravenously to the same mice model as above and SPECT images were acquired by a Triumph LabPET12/SPECT4/CT at 24, 48, and 72 h after injection. Results: 111In-DTPA-Mogamulizumab was acquired with the radiochemical yield of 72 ± 4% and the radiochemical purity of over 95%. In the in vitro study, CCR4 high expression cells (ATL43T cell and HCT116/CCR4 cell) show significantly higher 111In-DTPA-Mogamulizumab accumulation compared to CCR4 low expression cells (ED(-) cell and HCT116/EV cell) (p<0.01). In addition, the 111In-DTPA-Mogamulizumab accumulation in ATL43T and HCT116/CCR4 cells was significantly suppressed by co-incubation of excess non-labeled mogamulizumab (p<0.01). In the biodistribution study, the radioactivity of HCT116/CCR4 tumor was significantly higher than that of HCT116/EV tumor at 24-72 h after injection (p<0.01, Fig. 2). In the SPECT study, HCT116/CCR4 tumor was clearly visualized from 24 h after injection (Fig. 3). Conclusions: We have successfully synthesized a novel SPECT imaging tracer targeting for CCR4, 111In-DTPA-Mogamulizumab. It showed enough binding affinity to CCR4 for the imaging study. The microSPECT and ex vivo biodistribution studies revealed that 111In-DTPA-Mogamulizumab showed good specificity and pharmacokinetics, showing that it is a potential tracer for visualizing CCR4 expression in human tumor cells. References: [1] Ishida, et al., J Clin Oncol. 2012.30:837 [2] Ogura, et al., J Clin Oncol. 2014.32:1157