Mean estimated human absorbed doses for ⁶⁴Cu-ATSM, extrapolated from mouse biodistribution data.

<p>Mean estimated human absorbed doses for ⁶⁴Cu-ATSM, extrapolated from mouse biodistribution data.</p

Chronological changes in biodistribution and excretion after ⁶⁴Cu-ATSM injection with fractionated penicillamine injections.

<p>Biodistribution in organs and urinary and fecal excretions at 2, 4, 6, 16, and 24⁶⁴Cu-ATSM injection in HT-29 tumor-bearing mice that were treated p.o. with fractionated doses of penicillamine (100 mg/kg×3) at 1, 2, and 3 h or 1, 3, and 5 h after ⁶⁴Cu-ATSM injection, compared with those in animals treated with saline (control). Additional laxative treatments at 5.5 h after ⁶⁴Cu-ATSM injection along with penicillamine administration (100 mg/kg×3; 1, 3, and 5 h after ⁶⁴Cu-ATSM injection) are also shown. Data are shown as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, remainder of the body, and tumor) and blood and the %ID for the urine and feces at 2, 4, 6, 16, and 24 h after ⁶⁴Cu-ATSM injection. Asterisks indicate statistical significance (*<i>P</i><0.05) in comparison to the control at each time point. There were no significant differences in the %ID/g of the tumors between any of the treatment groups and the control. Values are shown as means ± SD; <i>n</i> = 4 for 2, 4, and 6 h and <i>n</i> = 3 for 16 and 24 h.</p

Biodistribution of ⁶⁴Cu-ATSM in BALB/c nude mice.

<p>Data were obtained at 5⁶⁴Cu-ATSM injection. Values are expressed as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, and remainder of the body) and blood and as the %ID for the urine and feces. Values are shown as means ± SD; <i>n</i> = 4 for 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, and 6 h and <i>n</i> = 3 for 16 h and 24 h.</p

Representative PET images.

<p>PET images of HT-29 tumor-bearing mice that were administered ⁶⁴Cu-ATSM and a single dose of penicillamine (300 mg/kg p.o.) or saline (control) at 1 h after the ⁶⁴Cu-ATSM injection are shown. (A) Coronal PET images show the liver (white arrows). (B) Transverse PET images show the tumor. HT29 tumors are indicated by yellow arrows and circles. Images were obtained at 0.5, 2, and 3 h after the ⁶⁴Cu-ATSM injection. (C) Time activity curves from the PET analysis. Time activity curves for the liver (upper) and tumor (lower) are shown for animals treated with penicillamine or saline (control; <i>n = </i>3/group). Values are shown as means ± SD.</p

Controlled Administration of Penicillamine Reduces Radiation Exposure in Critical Organs during ⁶⁴Cu-ATSM Internal Radiotherapy: A Novel Strategy for Liver Protection

<div><p>Purpose</p><p>⁶⁴Cu-diacetyl-bis (<i>N</i>⁴-methylthiosemicarbazone) (⁶⁴Cu-ATSM) is a promising theranostic agent that targets hypoxic regions in tumors related to malignant characteristics. Its diagnostic usefulness has been recognized in clinical studies. Internal radiotherapy (IRT) with ⁶⁴Cu-ATSM is reportedly effective in preclinical studies; however, for clinical applications, improvements to reduce radiation exposure in non-target organs, particularly the liver, are required. We developed a strategy to reduce radiation doses to critical organs while preserving tumor radiation doses by controlled administration of copper chelator penicillamine during ⁶⁴Cu-ATSM IRT.</p><p>Methods</p><p>Biodistribution was evaluated in HT-29 tumor-bearing mice injected with ⁶⁴Cu-ATSM (185 kBq) with or without oral penicillamine administration. The appropriate injection interval between ⁶⁴Cu-ATSM and penicillamine was determined. Then, the optimal penicillamine administration schedule was selected from single (100, 300, and 500 mg/kg) and fractionated doses (100 mg/kg×3 at 1- or 2-h intervals from 1 h after ⁶⁴Cu-ATSM injection). PET imaging was performed to confirm the effect of penicillamine with a therapeutic ⁶⁴Cu-ATSM dose (37 MBq). Dosimetry analysis was performed to estimate human absorbed doses.</p><p>Results</p><p>Penicillamine reduced ⁶⁴Cu accumulation in the liver and small intestine. Tumor uptake was not affected by penicillamine administration at 1 h after ⁶⁴Cu-ATSM injection, when radioactivity was almost cleared from the blood and tumor uptake had plateaued. Of the single doses, 300 mg/kg was most effective. Fractionated administration at 2-h intervals further decreased liver accumulation at later time points. PET indicated that penicillamine acts similarly with the therapeutic ⁶⁴Cu-ATSM dose. Dosimetry demonstrated that appropriately scheduled penicillamine administration reduced radiation doses to critical organs (liver, ovaries, and red marrow) below tolerance levels. Laxatives reduced radiation doses to the large intestine.</p><p>Conclusions</p><p>We developed a novel strategy to reduce radiation exposure in critical organs during ⁶⁴Cu-ATSM IRT, thus promoting its clinical applications. This method could be beneficial for other ⁶⁴Cu-labeled compounds.</p></div

Additional file 6: of Uniform intratumoral distribution of radioactivity produced using two different radioagents, 64Cu-cyclam-RAFT-c(-RGDfK-)4 and 64Cu-ATSM, improves therapeutic efficacy in a small animal tumor model

(a) Tumor growth ratios of the same set of treated groups as described in Fig. 3. *, †, ‡P < 0.05 for combination, 64Cu-RaftRGD, and 64Cu-ATSM vs. vehicle control, respectively. Tumor growth ratios (b) and body weight changes (c) of U87MG tumor-bearing mice after co-administration of 64Cu-RaftRGD and 64Cu-ATSM at 111 MBq (55.5 MBq for each agent) and 148 MBq (74 MBq for each agent). Values are the means ± standard deviations (n = 4/group). *, **P < 0.05 and 0.01, respectively for 111 MBq-group vs. 148 MBq group, respectively. It should be noted that although vehicle controls (b, c) were not performed simultaneously along with the 111 MBq and 148 MBq groups, all the three independent experiments (#1 and #2 extracted from Additional file 4 and Additional file 6a, respectively) showed a reproducibly steady increase of the tumor volume in the vehicle-treated mice. (PDF 337 kb

Chronological changes in biodistribution and excretion after ⁶⁴Cu-ATSM injection with single-dose penicillamine injections.

<p>Biodistribution in the organs and urinary and fecal excretions at 2, 4, 6, 16, and 24⁶⁴Cu-ATSM injection in HT-29 tumor-bearing mice that were treated p.o. with a single-dose of 100, 300, or 500 mg/kg penicillamine at 1 h after ⁶⁴Cu-ATSM injection, compared with those in animals treated with saline (control). Data are shown as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, remainder of the body, and tumor) and blood and the %ID for the urine and feces. Asterisks indicate statistical significance (*<i>P</i><0.05) in comparison to the control at each time point. There were no significant differences in the %ID/g of the tumors between any of the treatment groups and the control. Values are shown as means ± SD; <i>n</i> = 4 for 2, 4, and 6 h and <i>n</i> = 3 for 16 and 24 h.</p

Additional file 3: of Uniform intratumoral distribution of radioactivity produced using two different radioagents, 64Cu-cyclam-RAFT-c(-RGDfK-)4 and 64Cu-ATSM, improves therapeutic efficacy in a small animal tumor model

Intratumoral distribution of 64Cu-ATSM and microvasculature. An adjacent slice to that presented in Fig. 2b was examined by autoradiography, CD31 immunofluorescence staining, and HE staining. Merged image showing 64Cu-ATSM distribution in green, CD31-stained microvessels in red, and HE stains. High-resolution pictures shown by dotted rectangles clearly depicting the stained microvessels in smaller size in 64Cu-ATSM high- vs. low-accumulated areas. Nuclei were stained with DAPI (blue). Scale bars, 2 mm, 200 μm. (PDF 285 kb

The effect of penicillamine administration timing on the biodistribution of ⁶⁴Cu-ATSM.

<p>(A) Biodistribution in the liver (upper) and tumor (lower) in HT-29 tumor-bearing mice that were treated p.o. with a single-dose of 500 mg/kg penicillamine at 10 min before or after ⁶⁴Cu-ATSM injection or at 1 h after ⁶⁴Cu-ATSM injection. Data were obtained at 1, 2, and 4 h after ⁶⁴Cu-ATSM injection. (B) Time activity curves for the tumors and blood, based on the biodistribution data from HT-29 tumor-bearing mice (control animal). Values are shown as means ± SD; <i>n</i> = 4 for each time point.</p

Additional file 5: of Uniform intratumoral distribution of radioactivity produced using two different radioagents, 64Cu-cyclam-RAFT-c(-RGDfK-)4 and 64Cu-ATSM, improves therapeutic efficacy in a small animal tumor model

Tumor growth curves (a) and body weight changes (b) of the same set of experimental groups as described in Fig. 3. Values are the means ± standard deviations (n = 6/group). The final data points shown for each group of mice (b) represent the results obtained at survival endpoint days (represented by a mean value). *, †, ‡P < 0.05 for combination, 64Cu-RaftRGD, and 64Cu-ATSM vs. vehicle control, respectively. (PDF 140 kb