The search for treatments to counter potentially lethal radiation-induced injury over the past several decades has led to the development of multiple classes of radiation countermeasures. However, to date only granulocyte colony-stimulating factor (G-CSF; filgrastim, Neupogen)and pegylated G-CSF (pegfilgrastim, Neulasta) have been approved by the United States Food and Drug Administration (FDA) for the treatment of hematopoietic acute radiation syndrome (ARS). Gamma-tocotrienol (GT3) has demonstrated strong radioprotective efficacy in the mouse model, indicating the need for further evaluation in a large animal model. In this study, we evaluated the pharmacokinetics (PK) and efficacy of different doses of cobalt-60 gamma radiation (0.6 Gy/min) using the nonhuman primate (NHP) model. The PK results demonstrated increased area under the curve with increasing drug dose and half-life of GT3. GT3 treatment resulted in reduced group mean neutropenia by 3–5 days and thrombocytopenia by 1–5 days. At 5.8 and 6.5 G...

To date, there are no safe and effective drugs available for protection against ionizing radiation damage. Therefore, a great need exists to identify and develop non-toxic agents that will be useful as radioprotectors or postirradiation therapies under a variety of operational scenarios. We have developed a new pharmacological agent, CBLB613 (a naturally occurring Mycoplasma-derived lipopeptide ligand for Toll-like receptor 2/6), as a novel radiation countermeasure. Using CD2F1 mice, we investigated CBLB613 for toxicity, immunogenicity, radioprotection, radiomitigation and pharmacokinetics. We also evaluated CBLB613 for its effects on cytokine induction and radiation-induced cytopenia in unirradiated and irradiated mice. The no-observable-adverse-effect level of CBLB613 was 1.79 mg/kg and 1 mg/kg for single and repeated doses, respectively. CBLB613 significantly protected mice against a lethal dose of 60Co γ radiation. The dose reduction factor of CBLB613 as a radioprotector was 1.25. CBLB613 also mitigated the effects of 60Co γ radiation on survival in mice. In both irradiated and unirradiated mice, the drug stimulated induction of interleukin-1β (IL-1β), IL-6, IL-10, IL-12, keratinocyte-derived chemokine, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-1α. CBLB613 also reduced radiation-induced cytopenia and increased bone marrow cellularity in irradiated mice. Our immunogenicity study demonstrated that CBLB613 is not immunogenic in mice, indicating that it could be developed as a radioprotector and radiomitigator for humans against the potentially lethal effects of radiation exposure.

The aim of this study was to elucidate the potential of mouse myeloid progenitor cells (mMPC) to mitigate lethal doses of 60Co γ radiation and X rays in various strains of mice. Different cell doses of pooled allogeneic mMPC generated ex vivo from AKR, C57Bl/6, and FVB mice were transfused intravenously into haplotype-mismatched recipient Balb/c or CD2F1 mice at various times after irradiation to assess their effect on 30-day survival. Our results show that cryopreserved allogeneic mMPC significantly improve survival in both strains of mice irradiated with lethal doses of 60Co γ radiation (CD2F1, 9.2 Gy) and X-ray exposures (Balb/c, 9 Gy) that are known to cause acute radiation syndrome in hematopoietic tissues. Survival benefit was mMPC-dose dependent and significant even when mMPC administration was delayed up to 7 days after irradiation. We further show that mMPC administration mitigates death from acute radiation syndrome at radiation doses of up to 15 Gy (60Co γ radiation, CD2F1), which are radiation exposure levels that cause mice to succumb to multi-organ failure, and determined that the dose-reduction factor of 5 million mMPC administered 24 h after irradiation of CD2F1 mice is 1.73. Even at high doses of up to 14 Gy 60Co γ radiation, mMPC administration could be delayed up to 5 days in CD2F1 mice and still provide significant benefit to 30-day survival. These results demonstrate that mMPC are a promising radiation countermeasure with the potential to mitigate radiation injury in unmatched recipients across a broad range of lethal radiation doses, even when administration is delayed days after radiation exposure. With respect to efficacy, timing, and practicality of administration, mMPC appear to be a very promising radiation countermeasure for acute radiation syndrome among all candidate therapeutics currently under development.

The purpose of this study was to elucidate the role of α-tocopherol succinate (α-TS) in protecting mice from gastrointestinal syndrome induced by total-body irradiation. CD2F1 mice were injected subcutaneously with 400 mg/kg of α-TS and exposed to different doses of (60)Co γ radiation, and 30-day survival was monitored. Jejunum sections were analyzed for crypts and villi, PUMA (p53 upregulated modulator of apoptosis), and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling - TUNEL). The crypt regeneration in irradiated mice was evaluated by 5-bromo-2-deoxyuridine (BrdU). Bacterial translocation from gut to heart, spleen and liver in α-TS-treated and irradiated mice was evaluated by bacterial culture on sheep blood agar, colistin-nalidixic acid, and xylose-lysine-desoxycholate medium. Our results demonstrate that α-TS enhanced survival in a significant number of mice irradiated with 9.5, 10, 11 and 11.5 Gy (60)Co γ radiation when administered 24 h before radiation exposure. α-TS also protected the intestinal tissue of irradiated mice in terms of crypt and villus number, villus length and mitotic figures. TS treatment decreased the number of TUNEL- and PUMA-positive cells and increased the number of BrdU-positive cells in jejunum compared to vehicle-treated mice. Further, α-TS inhibited gut bacterial translocation to the heart, spleen and liver in irradiated mice. Our data suggest that α-TS protects mice from radiation-induced gastrointestinal damage by inhibiting apoptosis, promoting regeneration of crypt cells, and inhibiting translocation of gut bacteria.

The field of biodosimetry has seen a paradigm shift towards an increased use of molecular phenotyping technologies including omics and miRNA, in addition to conventional cytogenetic techniques. Here, we have used a nonhuman primate (NHP) model to study the impact of gamma-irradiation on alterations in blood-based gene expression. With a goal to delineate radiation induced changes in gene expression, we followed eight NHPs for 60 days after exposure to 6.5 Gy gamma-radiation for survival outcomes. Analysis of differential gene expression in response to radiation exposure yielded 26,944 dysregulated genes that were not significantly impacted by sex. Further analysis showed an increased association of several pathways including IL-3 signaling, ephrin receptor signaling, ErbB signaling, nitric oxide signaling in the cardiovascular system, Wnt/β-catenin signaling, and inflammasome pathway, which were associated with positive survival outcomes in NHPs after acute exposure to radiation. This study provides novel insights into major pathways and networks involved in radiation-induced injuries that may identify biomarkers for radiation injury.

The development of radiation countermeasures for acute radiation syndrome (ARS) has been underway for the past six decades, leading to the identification of multiple classes of radiation countermeasures. However, to date, only two growth factors (Neupogen and Neulasta) have been approved by the United States Food and Drug Administration (US FDA) for the mitigation of hematopoietic acute radiation syndrome (H-ARS). No radioprotector for ARS has been approved by the FDA yet. Gamma-tocotrienol (GT3) has been demonstrated to have radioprotective efficacy in murine as well as nonhuman primate (NHP) models. Currently, GT3 is under advanced development as a radioprotector that can be administered prior to radiation exposure. We are studying this agent for its safety profile and efficacy using the NHP model. In this study, we analyzed global metabolomic and lipidomic changes using ultra-performance liquid chromatography (UPLC) quadrupole time-of-flight mass spectrometry (QTOF-MS) in serum samples of NHPs administered GT3. Our study, using 12 NHPs, demonstrates that alterations in metabolites manifest only 24 h after GT3 administration. Furthermore, metabolic changes are associated with transient increase in the bioavailability of antioxidants, including lactic acid and cholic acid and anti-inflammatory metabolites 3 deoxyvitamin D3, and docosahexaenoic acid. Taken together, our results show that the administration of GT3 to NHPs causes metabolic shifts that would provide an overall advantage to combat radiation injury. This initial assessment also highlights the utility of metabolomics and lipidomics to determine the underlying physiological mechanisms involved in the radioprotective efficacy of GT3.