The ability of filgrastim to mitigate mortality following LD50/60 total-body irradiation is administration time-dependent

Product Development within the National Institutes of Health Radiation and Nuclear Countermeasures Program

The Radiation and Nuclear Countermeasures Program (RNCP) at the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH) was established to facilitate the development of medical countermeasures (MCMs) and diagnostic approaches for use in a radiation public health emergency. Approvals for MCMs can be very challenging but are made possible under the United States Food and Drug Administration (FDA) Animal Rule, which is designed to enable licensure of drugs or biologics when clinical efficacy studies are unethical or unfeasible. The NIAID portfolio includes grants, contracts, and inter-agency agreements designed to span all aspects of drug development and encompasses basic research through FDA approval. In addition, NIAID manages an active portfolio of biodosimetry approaches to assess injuries and absorbed radiation levels to guide triage and treatment decisions. NIAID, together with grantees, contractors, and other stakeholders with promising products, works to advance candidate MCMs and biodosimetry tools through an established product development pipeline. In addition to managing grants and contracts, NIAID tests promising candidates in our established preclinical animal models, and the NIAID Program Officers work closely with sponsors as product managers to guide them through the process. In addition, a valuable benefit for stakeholders is working with the NIAID Office of Regulatory Affairs, where NIAID coordinates with the FDA to facilitate interactions between sponsors and the agency. Activities funded by NIAID include basic research (e.g., library screens to discover new products, determine early efficacy, and delineate mechanism of action) and the development of small and large animal models of radiation-induced hematopoietic, gastrointestinal, lung, kidney, and skin injury, radiation combined injury, and radionuclide decorporation. NIAID also sponsors Good Laboratory Practice product safety, pharmacokinetic, pharmacodynamic, and toxicology studies, as well as efficacy and dose-ranging studies to optimize product regimens. For later-stage candidates, NIAID funds large-scale manufacturing and formulation development of products. The program also supports Phase 1 human clinical studies to ensure human safety and to bridge pharmacokinetic, pharmacodynamic, and efficacy data from animals to humans. To date, NIAID has supported >900 animal studies and one clinical study, evaluating >500 new/repurposed radiation MCMs and biodosimetric approaches. NIAID sponsorship led to the approval of three of the six drugs for acute radiation syndrome under the FDA Animal Rule, five Investigational New Drug applications, and 18 additional submissions for Investigational Device Exemptions, while advancing 38 projects to the Biomedical Advanced Research and Development Authority for follow-on research and development.

Four Genes Predictive for the Severity of Hematological Damage Reveal a Similar Response after X Irradiation and Chemotherapy

Radiological and especially nuclear accidents and incidents pose a threat to populations. In such events, gene expression (GE) analysis of a set of 4 genes (FDXR, DDB2, POU2AF1, WNT3) is an emerging approach for early and high-throughput prediction of the later manifesting severity degrees of the hematological acute radiation syndrome (H-ARS). Validation of this gene set on radiation victims is difficult since these events are rare. However, chemotherapy (CTX) is widely used e.g., breast cancer patient treatment and pathomechanisms, as well as blood cell count changes are comparable among both exposure types. We wondered whether GE changes are similarly deregulated after CTX, which would be interpreted as a confirmation of our already identified gene set for H-ARS prediction after irradiation. We examined radiation-induced differential GE (DGE) of our gene set as a positive control using in vitro whole blood samples from ten healthy donors (6 females, 4 males, aged: 24-40 years). Blood was incubated in vitro for 8 h after X irradiation with 0 and 4 Gy (1 Gy/min). These data were compared with DGE measured in vivo in blood samples of 10 breast tumor CTX patients (10 females, aged: 39-71 years) before and 4 days after administration of cyclophosphamide and epirubicin. RNA was isolated, reverse transcribed and quantitative real-time polymerase-chain-reaction (qRT-PCR) was performed to assess DGE of FDXR, DDB2, POU2AF1 and WNT3 relative to the unexposed samples using TaqMan assays. After X irradiation, we found a significant upregulation (irrespective of sex) with mean fold changes of 21 (P < 0.001) and 7 (P < 0.001) for FDXR and DDB2 and a significant down-regulation with mean fold changes of 2.5 (P < 0.001) and 2 (P = 0.005) for POU2AF1 and WNT3, respectively. After CTX, a similar pattern was observed, although mean fold changes of up-regulated FDXR (6-fold, P < 0.001) and DDB2 (3-fold, P < 0.001) as well as down-regulated POU2AF1 (1.2-fold, P = 0.270) and WNT3 (1.3-fold, P = 0.069) appeared lower corresponding to less altered blood cell count changes observed after CTX compared to historic radiation exposure data. However, a subpopulation of CTX patients (n = 6) showed on average a significant downregulation of POU2AF1 (1.8-fold, P = 0.04) and WNT3 (2.1-fold, P = 0.008). In summary, the pattern of up-regulated GE changes observed in all CTX patients and down-regulated GE changes observed in a subgroup of CTX patients appeared comparable with an already identified gene set predictive for the radiation-induced H-ARS. This underlines the significance of in vivo GE measurements in CTX patients, employed as a surrogate model to further validate already identified radiation-induced GE changes predictive for the H-ARS.

Pharmacokinetic Study of rhIL-18BP and Its Effect on Radiation-Induced Cytokine Changes in Mouse Serum and Intestine

Administration of recombinant human IL-18 binding protein (rhIL-18BP), a natural antagonist of IL-18, significantly increased mouse survival after lethal doses of irradiation. To further understand the roles of IL-18BP in radiation mitigation, we studied the pharmacokinetic (PK) parameters of rhIL-18BP, and the serum and intestinal cytokine changes in CD2F1 mice treated with vehicle or rhIL-18BP after 9.0 Gy total body irradiation (TBI). For the PK study, non-compartmental pharmacokinetic analysis was performed using PKsolver. Serum and intestine specimens were collected to measure 44-cytokine levels. Principal component analysis showed a clear separation of the non-irradiated samples from the irradiated samples; and partial separation with or without rhIL-18BP treatment. Cytokine clusters that were significantly correlated in the serum or intestine, respectively were identified. On the individual cytokine levels, serum and intestinal cytokines that were significantly changed by irradiation and rhIL-18BP treatment were identified. Finally, cytokines that were significantly correlated between their serum and intestinal levels were identified. The current study established the PK parameters of rhIL-18BP in mice, identified significantly changed cytokines in mouse serum and intestine after radiation exposure and rhIL-18BP treatment. Current data provide critical insights into IL-18BP's mechanism of action as a radiation mitigator.

Medical countermeasures for the hematopoietic-subsyndrome of acute radiation syndrome in space

More than 50 years after the Apollo missions ended, the National Aeronautical and Space Administration (NASA) and other international space agencies are preparing a return to the moon as a step towards deep space exploration. At doses ranging from a fraction of a Gray (Gy) to a few Gy, crew will be at risk for developing bone marrow failure associated with the hematopoietic subsyndrome of acute radiation syndrome (H-ARS) requiring pharmacological intervention to reduce risk to life and mission completion. Four medical countermeasures (MCM) in the colony stimulating factor class of drugs are now approved for treatment of myelosuppression associated with ARS. When taken in conjunction with antibiotics, fluids, antidiarrheals, antiemetics, antipyretics, and other treatments for symptomatic illness, the likelihood for recovery and mission completion can be greatly improved. The current review describes the performance and health risks of deep space flight, ionizing radiation exposure during crewed missions to the moon and Mars, and U.S. Food and Drug Administration (FDA)-approved medical interventions to treat ARS. With an expansion of human exploration missions beyond low Earth orbit (LEO), including near-term Lunar and future Mars missions, inclusion of MCMs to counteract ARS in the spaceflight kit will be critical for preserving crew health and performance.

SEED: An Operational Numerical Tool for Dosimetric Reconstruction in Case of External Radiological Overexposure

ABSTRACT

In the event of a radiological accident involving external exposure of one or more victims and potential high doses, it is essential to know the dose distribution within the body in order to sort the victims according to the severity of the irradiation and then to take them to the most suitable medical facilities. However, there are currently few techniques that can be rapidly deployed on field and capable of characterizing an irradiation. Therefore, a numerical simulation tool has been designed. It can be implemented by a doctor/physicist pairing, projected within a limited time as close as possible to the irradiation accident and emergency response teams. Called SEED (Simulation of External Exposures & Dosimetry), this tool (dedicated to dose reconstruction in case of external exposure) allows a rapid modeling of the irradiation scene and a visual exchange with the victims and witnesses of the event. The user can navigate in three dimensions in the accident scene thanks to a graphical user interface including a "first person" camera. To validate the performance of the SEED tool, two dosimetric benchmarking exercises were performed. The first consisted in comparing the dose value provided by SEED to that given by a reference calculation code: MCNPX. The purpose of the second validation was to perform an experiment irradiating a physical dummy equipped with dosimeters and to reconstruct this irradiation using SEED. These two validation protocols have shown satisfactory results with mean difference less than 2% and 12% for the first and second exercises, respectively. They confirm that this new tool is able to provide useful information to medical teams in charge of dosimetric triage in case of a major external exposure event.

Training of clinical triage of acute radiation casualties: a performance comparison ofon-siteversusonlinetraining due to the covid-19 pandemic

A collection of powerful diagnostic tools have been developed under the umbrellas of NATO for ionising radiation dose assessment (BAT, WinFRAT) and estimate of acute health effects in humans (WinFRAT, H-Module). We assembled a database of 191 ARS cases using the medical treatment protocols for radiation accident victims (n= 167) and the system for evaluation and archiving of radiation accidents based on case histories (n= 24) for training purposes of medical personnel. From 2016 to 2019, we trained 39 participants comprising MSc level radiobiology students in an on-site teaching class. Enforced by the covid-19 pandemic in 2020 for the first time, an online teaching of nine MSc radiobiology students replaced the on-site teaching. We found that: (a) limitations of correct diagnostic decision-making based on clinical signs and symptoms were experienced unrelated to the teaching format. (b) A significant performance decrease concerning online (first number in parenthesis) versus on-site teaching (reference and second number in parenthesis) was seen regarding the estimate time (31 vs 61 cases per hour, two-fold decrease,p= 0.005). Also, the accurate assessment of response categories (89.9% vs 96.9%,p= 0.001), ARS (92.4% vs 96.7%,p= 0.002) and hospitalisation (93.5% vs 97.0%,p= 0.002) decreased by around 3%-7%. The performances of the online attendees were mainly distributed within the lower quartile performance of on-site participants and the 25%-75% interquartile range increased 3-7-fold. (c) Comparison of dose estimates performed by training participants with hematologic acute radiation syndrome (HARS) severity mirrored the known limitations of dose alone as a surrogate parameter for HARS severity at doses less than 1.5 Gy, but demonstrated correct determination of HARS 2-4 and support for clinical decision making at dose estimates >1.5 Gy, regardless of teaching format. (d) Overall, one-third of the online participants showed substantial misapprehension and insecurities of elementary course content that did not occur after the on-site teaching.

The Natural History of Acute Radiation-induced H-ARS and Concomitant Multi-organ Injury in the Non-human Primate: The MCART Experience

ABSTRACT

The dose response relationship and corresponding values for mid-lethal dose and slope are used to define the dose- and time-dependent parameters of the hematopoietic acute radiation syndrome. The characteristic time course of mortality, morbidity, and secondary endpoints are well defined. The concomitant comorbidities, potential mortality, and other multi-organ injuries that are similarly dose- and time-dependent are less defined. Determination of the natural history or pathophysiology associated with the lethal hematopoietic acute radiation syndrome is a significant gap in knowledge, especially when considered in the context of a nuclear weapon scenario. In this regard, the exposure is likely ill-defined, heterogenous, and nonuniform. These conditions forecast sparing of bone marrow and increased survival from the acute radiation syndrome consequent to threshold doses for the delayed effects of acute radiation exposure due to marrow sparing, medical management, and use of approved medical countermeasures. The intent herein is to provide a composite natural history of the pathophysiology concomitant with the evolution of the potentially lethal hematopoietic acute radiation syndrome derived from studies that focused on total body irradiation and partial body irradiation with bone marrow sparing. The marked differential in estimated LD50/60 from 7.5 Gy to 10.88 Gy for the total body irradiation and partial body irradiation with 5% bone marrow sparing models, respectively, provided a clear distinction between the attendant multiple organ injury and natural history of the two models that included medical management. Total body irradiation was focused on equivalent LD50/60 exposures. The 10 Gy and 11 Gy partial body with 5% bone marrow sparing exposures bracketed the LD50/60 (10.88 Gy). The incidence, progression, and duration of multiple organ injury was described for each exposure protocol within the hematopoietic acute radiation syndrome. The higher threshold doses for the partial body irradiation with bone marrow sparing protocol induced a marked degree of multiple organ injury to include lethal gastrointestinal acute radiation syndrome, prolonged crypt loss and mucosal damage, immune suppression, acute kidney injury, body weight loss, and added clinical comorbidities that defined a complex timeline of organ injury through the acute hematopoietic acute radiation syndrome. The natural history of the acute radiation syndrome presents a 60-d time segment of multi-organ sequelae that is concomitant with the latent period or time to onset of the evolving multi-organ injury of the delayed effects of acute radiation exposure.

AEOL 10150 Alleviates Radiation-induced Innate Immune Responses in Non-human Primate Lung Tissue

ABSTRACT

To study the molecular and cellular mechanisms of radiation-induced lung injury (RILI) in a non-human primate model, Rhesus macaques were irradiated with lethal doses of radiation to the whole thorax. A subset of the irradiated animals was treated with AEOL 10150, a potent catalytic scavenger of reactive oxygen and nitrogen species. Lung tissues were collected at necropsy for molecular and immunohistochemical (IHC) studies. Microarray expression profiling in the irradiated lung tissues identified differentially expressed genes (DEGs) and pathways important in innate immunity. The elevated expression of cytokines (CCL2, CCL11, IL-8), complement factors (CFB, C3), apoptosis-related molecules (p53, PTEN, Bax, p21, MDM2, c-Caspase 3), and adhesion molecules (fibronectin, integrin β6, ICAM-1) were further studied using real-time PCR, Western blot, or IHC. Oxidative stress and pulmonary inflammatory cell infiltration were increased in the irradiated lungs. Treatment with AEOL 10150 significantly decreased oxidative stress and monocyte/macrophage infiltration. Cytokine/chemokine-induced excessive innate immune response after thoracic irradiation plays an important role in RILI. To our knowledge, this is the first study to highlight the role of cytokine/chemokine-induced innate immune responses in radiation-induced pulmonary toxicity in a NHP model.

Scientific research and product development in the United States to address injuries from a radiation public health emergency

The USA has experienced one large-scale nuclear incident in its history. Lessons learned during the Three-Mile Island nuclear accident provided government planners with insight into property damage resulting from a low-level release of radiation, and an awareness concerning how to prepare for future occurrences. However, if there is an incident resulting from detonation of an improvised nuclear device or state-sponsored device/weapon, resulting casualties and the need for medical treatment could overwhelm the nation's public health system. After the Cold War ended, government investments in radiation preparedness declined; however, the attacks on 9/11 led to re-establishment of research programs to plan for the possibility of a nuclear incident. Funding began in earnest in 2004, to address unmet research needs for radiation biomarkers, devices and products to triage and treat potentially large numbers of injured civilians. There are many biodosimetry approaches and medical countermeasures (MCMs) under study and in advanced development, including those to address radiation-induced injuries to organ systems including bone marrow, the gastrointestinal (GI) tract, lungs, skin, vasculature and kidneys. Biomarkers of interest in determining level of radiation exposure and susceptibility of injury include cytogenetic changes, 'omics' technologies and other approaches. Four drugs have been approved by the US Food and Drug Administration (FDA) for the treatment of acute radiation syndrome (ARS), with other licensures being sought; however, there are still no cleared devices to identify radiation-exposed individuals in need of treatment. Although many breakthroughs have been made in the efforts to expand availability of medical products, there is still work to be done.

Inter-laboratory comparison of gene expression biodosimetry for protracted radiation exposures as part of the RENEB and EURADOS WG10 2019 exercise

Large-scale radiation emergency scenarios involving protracted low dose rate radiation exposure (e.g. a hidden radioactive source in a train) necessitate the development of high throughput methods for providing rapid individual dose estimates. During the RENEB (Running the European Network of Biodosimetry) 2019 exercise, four EDTA-blood samples were exposed to an Iridium-192 source (1.36 TBq, Tech-Ops 880 Sentinal) at varying distances and geometries. This resulted in protracted doses ranging between 0.2 and 2.4 Gy using dose rates of 1.5-40 mGy/min and exposure times of 1 or 2.5 h. Blood samples were exposed in thermo bottles that maintained temperatures between 39 and 27.7 °C. After exposure, EDTA-blood samples were transferred into PAXGene tubes to preserve RNA. RNA was isolated in one laboratory and aliquots of four blinded RNA were sent to another five teams for dose estimation based on gene expression changes. Using an X-ray machine, samples for two calibration curves (first: constant dose rate of 8.3 mGy/min and 0.5-8 h varying exposure times; second: varying dose rates of 0.5-8.3 mGy/min and 4 h exposure time) were generated for distribution. Assays were run in each laboratory according to locally established protocols using either a microarray platform (one team) or quantitative real-time PCR (qRT-PCR, five teams). The qRT-PCR measurements were highly reproducible with coefficient of variation below 15% in ≥ 75% of measurements resulting in reported dose estimates ranging between 0 and 0.5 Gy in all samples and in all laboratories. Up to twofold reductions in RNA copy numbers per degree Celsius relative to 37 °C were observed. However, when irradiating independent samples equivalent to the blinded samples but increasing the combined exposure and incubation time to 4 h at 37 °C, expected gene expression changes corresponding to the absorbed doses were observed. Clearly, time and an optimal temperature of 37 °C must be allowed for the biological response to manifest as gene expression changes prior to running the gene expression assay. In conclusion, dose reconstructions based on gene expression measurements are highly reproducible across different techniques, protocols and laboratories. Even a radiation dose of 0.25 Gy protracted over 4 h (1 mGy/min) can be identified. These results demonstrate the importance of the incubation conditions and time span between radiation exposure and measurements of gene expression changes when using this method in a field exercise or real emergency situation.

RRx-001 Radioprotection: Enhancement of Survival and Hematopoietic Recovery in Gamma-Irradiated Mice

The present studies evaluate the in vivo prophylactic radioprotective effects of 1-bromoacetyl-3, 3-dinitroazetidine (RRx-001), a phase III anticancer agent that inhibits c-myc and downregulates CD-47, after total body irradiation (TBI), in lethally and sublethally irradiated CD2F1 male mice. A single dose of RRx-001 was administered by intraperitoneal (IP) injection 24 h prior to a lethal or sublethal radiation dose. When irradiated with 9.35 Gy, the dose lethal to 70% of untreated mice at 30 days (LD_70/30), only 33% of mice receiving RRx-001 (10 mg/kg) 24 h prior to total body irradiation (TBI) died by day 30, compared to 67% in vehicle-treated mice. The same pretreatment dose of RRx-001 resulted in a significant dose reduction factor of 1.07. In sublethally TBI mice, bone marrow cellularity was increased at day 14 in the RRx-001-treated mice compared to irradiated vehicle-treated animals. In addition, significantly higher numbers of lymphocytes, platelets, percent hematocrit and percent reticulocytes were observed on days 7 and/or 14 in RRx-001-treated mice. These experiments provide proof of principle that systemic administration of RRx-001 prior to TBI significantly improves overall survival and bone marrow regeneration.

Sargramostim (rhu GM-CSF) Improves Survival of Non-Human Primates with Severe Bone Marrow Suppression after Acute, High-Dose, Whole-Body Irradiation

Exposure to acute, high-dose, whole-body ionizing radiation results in bone marrow failure (hematopoietic acute radiation syndrome with resultant infection, bleeding, anemia, and increased risk of death). Sargramostim (yeast-derived rhu GM-CSF), a yeast-derived, molecularly cloned, hematopoietic growth factor and pleiotropic cytokine supports proliferation, differentiation, maturation and survival of cells of several myeloid lineages. We evaluated the efficacy of sargramostim in non-human primates (rhesus macaques) exposed to whole-body ionizing radiation at a 50-60% lethal dose. The primary end point was day 60 survival. Non-human primates received daily subcutaneous sargramostim (7 mcg/kg/day) or control. To reflect the anticipated setting of a nuclear or radiologic event, treatment began 48 h postirradiation, and non-human primates received only moderate supportive care (no whole blood transfusions or individualized antibiotics). Sargramostim significantly increased day 60 survival to 78% (95% confidence interval, 61-90%) vs. 42% (26-59%; P = 0.0018) in controls. Neutrophil, platelet and lymphocyte recovery rates were accelerated and infection rates decreased. Improved survival when sargramostim was started 48 h postirradiation, without use of intensive supportive care, suggests sargramostim may be effective in treating humans exposed to acute, high-dose whole-body, ionizing radiation in a scenario such as a mass casualty event.

Software Tools for the Evaluation of Clinical Signs and Symptoms in the Medical Management of Acute Radiation Syndrome-A Five-year Experience

A suite of software tools has been developed for dose estimation (BAT, WinFRAT) and prediction of acute health effects (WinFRAT, H-Module) using clinical symptoms and/or changes in blood cell counts. We constructed a database of 191 ARS cases using the METREPOL (n = 167) and the SEARCH-database (n = 24). The cases ranged from unexposed (RC0), to mild (RC1), moderate (RC2), severe (RC3), and lethal ARS (RC4). From 2015-2019, radiobiology students and participants of two NATO meetings predicted clinical outcomes (RC, H-ARS, and hospitalization) based on clinical symptoms. We evaluated the prediction outcomes using the same input datasets with a total of 32 teams and 94 participants. We found that: (1) unexposed (RC0) and mildly exposed individuals (RC1) could not be discriminated; (2) the severity of RC2 and RC3 were systematically overestimated, but almost all lethal cases (RC4) were correctly predicted; (3) introducing a prior education component for non-physicians significantly increased the correct predictions of RC, ARS, and hospitalization by around 10% (p<0.005) with a threefold reduction in variance and a halving of the evaluation time per case; (4) correct outcome prediction was independent of the software tools used; and (5) comparing the dose estimates generated by the teams with H-ARS severity reflected known limitations of dose alone as a surrogate for H-ARS severity. We found inexperienced personnel can use software tools to make accurate diagnostic and treatment recommendations with up to 98% accuracy. Educational training improved the quality of decision making and enabled participants lacking a medical background to perform comparably to experts.

IL-18 binding protein (IL-18BP) as a novel radiation countermeasure after radiation exposure in mice

Recent studies suggested that radiation exposure causes local and systemic inflammatory responses and induces cell and tissue damage. We have reported that IL-18 plays an important role in radiation-induced injury. Here, we demonstrate that IL-18 binding protein (IL-18BP), a natural antagonist of IL-18, was significantly increased (1.7-63 fold) in mouse serum on day 1 after 0.5-10 Gy TBI. However, this high level of IL-18BP was not sufficient to neutralize the active IL-18 in irradiated mice, resulting in a radiation dose-dependent free IL-18 increase in these mice's serum which led to pathological alterations to the irradiated cells and tissues and finally caused animal death. Administration of recombinant human (rh) IL-18BP (1.5 mg/kg) with single (24, 48 or 72 h post-TBI) or double doses (48 h and 5 days post-TBI) subcutaneous (SC) injection increased 30-day survival of CD2F1 mice after 9 Gy TBI 12.5-25% compared with the vehicle control treated group, respectively. Furthermore, the mitigative effects of rhIL-18BP included balancing the ratio of IL-18/IL-18BP and decreasing the free IL-18 levels in irradiated mouse serum and significantly increasing blood cell counts, BM hematopoietic cellularity and stem and progenitor cell clonogenicity in mouse BM. Furthermore, IL-18BP treatment inhibited the IL-18 downstream target interferon (IFN)-γ expression in mouse BM, decreased reactive oxygen species (ROS) level in the irradiated mouse heart tissues, attenuated the stress responsive factor GDF-15 (growth differentiation factor-15) and increased the intestine protector citrulline level in total body irradiated mouse serum, implicating that IL-18BP may protect multiple organs from radiation-induced inflammation and oxidative stress. Our data suggest that IL-18 plays a key role in radiation-induced cell and tissue damage and dysfunction; and for the first time demonstrated that IL-18BP counters IL-18 activation and therefore may mitigate/treat radiation-induced multiple organ injuries and increase animal survival with a wider therapeutic window from 24 h and beyond after lethal doses of radiation exposure.

Developing and comparing models of hematopoietic-acute radiation syndrome in Göttingen and Sinclair minipigs

PURPOSE

Current animal models of hematopoietic-acute radiation syndrome (H-ARS) are resource intensive and have limited translation to humans, thereby inhibiting the development of effective medical countermeasures (MCM)s for radiation exposure.

MATERIALS AND METHODS

To improve the MCM pipeline, we developed models of H-ARS in male Göttingen and Sinclair minipigs. Weight matched Göttingens and Sinclairs received total body irradiation (TBI; 1.50-2.10 Gy and 1.94-2.90 Gy, respectively), were observed for up to 45 days with blood collections for clinical pathology analysis, and were examined during gross necropsy.

RESULTS

The lethal dose for 50% of the population over the course of 45 days (LD_50/45) with 'field' supportive care (primarily antibiotics and hydration support) and implanted vascular access ports was 1.89 and 2.53 Gy for Göttingens and Sinclairs, respectively. Both minipig strains exhibited prototypical H-ARS characteristics, experiencing thrombocytopenia and neutropenia, and nadirs approximately 14 days following irradiation, slightly varying with dose. Both strains experienced increased bruising, petechia, and signs of internal hemorrhage in the lungs, GI, heart, and skin. All observations were noted to correlate with dose more closely in Sinclairs than in Göttingens.

CONCLUSION

The results of this study provide a template for future MCM development in an alternate species, and support further development of the Göttingen and Sinclair minipig H-ARS models.

Efficacy of delayed administration of sargramostim up to 120 hours post exposure in a nonhuman primate total body radiation model

BACKGROUND

High dose ionizing radiation exposure is associated with myelo-depression leading to pancytopenia and the expected clinical manifestations of acute radiation syndrome (ARS). Herein, we evaluated the efficacy of sargramostim (Leukine®, yeast-derived rhu GM-CSF), with regimens delivered at 48, 72, 96, or 120 h after radiation exposure.

METHODS

A randomized and blinded nonhuman primate (NHP) study was conducted to assess the effects of sargramostim treatment on ARS. NHPs were exposed to total body radiation (LD83/60 or lethal dose 83% by Day 60) and were randomized to groups receiving daily subcutaneous dosing of sargramostim starting from either 48, 72, 96, or 120 h post-irradiation. Additionally, separate groups receiving sargramostim treatment at 48 h post-irradiation also received prophylactic treatment with azithromycin. Sargramostim treatment of each animal continued until the preliminary absolute neutrophil count (ANC) returned to ≥1000/μL post-nadir for three consecutive days or the preliminary ANC exceeded 10,000/μL, which amounted to be an average of 15.95 days for all treatment groups. Prophylactic administration of enrofloxacin was included in the supportive care given to all animals in all groups. All animals were monitored for 60 days post-irradiation for mortality, hematological parameters, and sepsis.

RESULTS

Delayed sargramostim treatment at 48 h post-irradiation significantly reduced mortality (p = .0032) and improved hematological parameters including neutrophil but also lymphocyte and platelet counts. Additional delays in sargramostim administration at 72, 96, and 120 h post-irradiation were also similarly effective at enhancing the recovery of lymphocyte, neutrophil, and platelet counts compared to control. Sargramostim treatment also improved the survival of the animals when administered at up to 96 h post-irradiation. While sargramostim treatment at 48 h significantly reduced mortality associated with sepsis (p ≤ .01), the additional prophylactic treatment with azithromycin did not have clinically significant effects.

CONCLUSION

In a NHP ARS model, sargramostim administered starting at 48 h post-radiation was effective to improve survival, while beneficial hematological effects were observed with sargramostim initiated up to 120 h post exposure.

Use of molecularly-cloned haematopoietic growth factors in persons exposed to acute high-dose, high-dose rate whole-body ionizing radiations

Exposure to acute, high-dose, high dose-rate whole-body ionizing radiations damages the bone marrow resulting in rapid decreases in concentrations of blood cells, especially lymphocytes, granulocytes and platelets with associated risks of infection and bleeding. In several experimental models including non-human primate radiation exposure models giving molecularly cloned haematopoietic growth factor including granulocyte/macrophage colony-stimulating factor (G/M-CSF; sargramostim) and granulocyte colony-stimulating factor (G-CSF; filgrastim and pegylated G-CSF [peg-filgrastim]) accelerates bone marrow recovery and increases survival. Based on these data these molecules are US FDA approved for treating victims of radiation and nuclear incidents, accident and events such as nuclear terrorism and are included in the US National Strategic Stockpile. We discuss the immediate medical response to these events including how to estimate radiation dose and uniformity and which interventions are appropriate in different radiation exposures settings. We also discuss similarities and differences between molecularly cloned haematopoietic growth factors.

Characterizing the Natural History of Acute Radiation Syndrome of the Gastrointestinal Tract: Combining High Mass and Spatial Resolution Using MALDI-FTICR-MSI

The acute radiation syndrome of the gastrointestinal tract has been histologically characterized, but the molecular and functional mechanisms that lead to these cellular alterations remain enigmatic. Mass spectrometry imaging is the only technique that enables the simultaneous detection and cellular or regional localization of hundreds of biomolecules in a single experiment. This current study utilized matrix-assisted laser desorption/ionization mass spectrometry imaging for the molecular characterization of the first natural history study of gastrointestinal acute radiation syndrome in the nonhuman primate. Jejunum samples were collected at days 4, 8, 11, 15, and 21 following 12-Gy partial-body irradiation with 2.5% bone marrow sparing. Mass spectrometry imaging investigations identified alterations in lipid species that further understanding of the functional alterations that occur over time in the different cellular regions of the jejunum following exposure to high doses of irradiation. Alterations in phosphatidylinositol species informed on dysfunctional epithelial cell differentiation and maturation. Differences in glycosphingolipids of the villi epithelium that would influence the absorptive capacity and functional structure of the brush border membrane were detected. Dichotomous alterations in cardiolipins indicated altered structural and functional integrity of mitochondria. Phosphatidylglycerol species, known regulators of toll-like receptors, were detected and localized to regions in the lamina propria that contained distinct immune cell populations. These results provide molecular insight that can inform on injury mechanism in a nonhuman primate model of the acute radiation syndrome of the gastrointestinal tract. Findings may contribute to the identification of therapeutic targets and the development of new medical countermeasures.

Efficacy of Neulasta or Neupogen on H-ARS and GI-ARS Mortality and Hematopoietic Recovery in Nonhuman Primates After 10-Gy Irradiation With 2.5% Bone Marrow Sparing

A nonhuman primate model of acute, partial-body, high-dose irradiation with minimal (2.5%) bone marrow sparing was used to assess endogenous gastrointestinal and hematopoietic recovery and the ability of Neulasta (pegylated granulocyte colony-stimulating factor) or Neupogen (granulocyte colony-stimulating factor) to enhance recovery from myelosuppression when administered at an increased interval between exposure and initiation of treatment. A secondary objective was to assess the effect of Neulasta or Neupogen on mortality and morbidity due to the hematopoietic acute radiation syndrome and concomitant gastrointestinal acute radiation syndrome. Nonhuman primates were exposed to 10.0 Gy, 6 MV, linear accelerator-derived photons delivered at 0.80 Gy min. All nonhuman primates received subject-based medical management. Nonhuman primates were dosed daily with control article (5% dextrose in water), initiated on day 1 postexposure; Neulasta (300 μg kg), administered on days 1, 8, and 15 or days 3, 10, and 17 postexposure; or Neupogen (10 μg kg), administered daily postexposure following its initiation on day 1 or day 3 until neutrophil recovery (absolute neutrophil count ≥1,000 cells μL for 3 consecutive days). Mortality in the irradiated cohorts suggested that administration of Neulasta or Neupogen on either schedule did not affect mortality due to gastrointestinal acute radiation syndrome or mitigate mortality due to hematopoietic acute radiation syndrome (plus gastrointestinal damage). Following 10.0 Gy partial-body irradiation with 2.5% bone marrow sparing, the mean duration of neutropenia (absolute neutrophil count <500 cells μL) was 22.4 d in the control cohort vs. 13.0 and 15.3 d in the Neulasta day 1, 8, 15 and day 3, 10, 17 cohorts, relative to 16.2 and 17.4 d in the Neupogen cohorts initiated on day 1 and day 3, respectively. The absolute neutrophil count nadirs were 48 cells μL in the controls; 117 cells μL and 40 cells μL in the Neulasta days 1, 8, and 15 or days 3, 10, and 17 cohorts, respectively; and 75 cells μL and 37 cells μL in the Neupogen day 1 and day 3 cohorts, respectively. Therefore, the earlier administration of Neulasta or Neupogen was more effective in this model of marginal 2.5% bone marrow sparing. The approximate 2.5% bone marrow sparing may approach the threshold for efficacy of the lineage-specific medical countermeasure. The partial-body irradiation with 2.5% bone marrow sparing model can be used to assess medical countermeasure efficacy in the context of the concomitant gastrointestinal and hematopoietic acute radiation syndrome sequelae.

Radiation Nephropathy in a Nonhuman Primate Model of Partial-body Irradiation with Minimal Bone Marrow Sparing-Part 1: Acute and Chronic Kidney Injury and the Influence of Neupogen

Acute and chronic kidney injury may occur after accidental prompt radiation exposures. We have modeled their occurrence in a nonhuman primate model. Subjects who are exposed to more than 5-Gy prompt irradiation are apt to show blood cell cytopenias and be treated with granulocyte colony-stimulating factors such as Neupogen® or Neulasta® to mitigate the hematologic injury of the acute radiation syndrome. Neupogen or Neulasta are now approved by the US Food and Drug Administration for this indication. This will significantly increase the number of survivors of acute radiation exposures who will be at risk for delayed effects of radiation exposure, which includes acute and chronic kidney injury. The primary objectives of the present two companion manuscripts were to assess natural history of delayed radiation-induced renal injury in a nonhuman primate model of acute, high-dose, partial-body irradiation with 5% bone marrow sparing to include the clinical and histopathological evidence and the effect of Neupogen administration on morbidity and mortality. In this study, 88 nonhuman primates underwent 10- or 11-Gy partial-body irradiation with 5% bone marrow sparing, of which 36 were treated with Neupogen within 1, 3, or 5 d postirradiation. All animals were followed up to 180 d after irradiation. Renal function and histology end points showed early acute and later chronic kidney injury. These end points were not affected by use of Neupogen. We conclude that use of Neupogen to mitigate against the hematopoietic acute radiation syndrome has no impact on acute or chronic kidney injury.

Informing CONOPS and medical countermeasure deployment strategies after an improvised nuclear device detonation: the importance of delayed treatment efficacy data

Purpose: In the wake of a nuclear detonation, individuals with acute radiation syndrome will be a significant source of morbidity and mortality. Mathematical modeling can compare response strategies developed for real-world chaotic conditions after a nuclear blast in order to identify optimal strategies for administering effective treatment to these individuals. To maximize responders' abilities to save lives it is critical to understand how treatment efficacy is impacted by real-world conditions and levels of supportive care. To illustrate the importance of these factors, we developed a mathematical model of cytokine administration 24 h after the blast with varying levels of supportive care described in the primary literature.Conclusion: The results highlight the proportionally higher life-saving benefit of administering cytokines to individuals with a moderate to high dose of radiation exposure, compared to those with a lower dose. However, the fidelity of mathematical models is dependent on the primary data informing them. We describe the data needed to fully explore the impact of timing, dosage, and fractional benefit of cytokines and supportive care treatment in non-optimal situations that could be seen after a nuclear detonation. Studies addressing these types of knowledge gaps are essential to evaluating the relative efficacy of countermeasures to refine existing plans and help develop new strategies and priorities.

Development of a point-of-care radiation biodosimeter: studies using novel protein biomarker panels in non-human primates

Purpose: There is a need to rapidly triage individuals for absorbed radiation dose following a significant nuclear event. Since most exposed individuals will not have physical dosimeters, we are developing a method to assess exposure dose based on the analysis of a specific panel of blood proteins that can be easily obtained from a fingerstick blood sample.Materials and methods: In three large non-human primate (NHP) studies, animals were exposed to single acute total body doses of x-ray or gamma radiation. A total of 895 blood samples were obtained at baseline and for 7 days after exposure, to evaluate the temporal progression of markers in each of 10 animals (5M/5F) in six dose groups receiving 0-10 Gy. We used tandem mass spectrometry and immunoassay techniques to identify radiation-responsive proteins in blood plasma samples.Results: A blood protein biomarker panel was developed based on analysis of blood plasma samples obtained from several irradiation studies in NHPs that aimed to simulate acute radiation injury in humans from a nuclear exposure event. Panels of several subsets of proteins were shown to accurately classify plasma samples into two exposure groups either above or below a critical dose threshold with sensitivities and specificities exceeding 90%.Conclusion: This study lays the groundwork for developing a radiation biodosimetry triage tool. Our results in NHPs must be compared with those in human patients undergoing radiotherapy to determine if the biomarker panel proteins exhibit a similar radiation response and allow adequate classification power in humans.

Challenges and Benefits of Repurposing Products for Use during a Radiation Public Health Emergency: Lessons Learned from Biological Threats and other Disease Treatments

The risk of a radiological or nuclear public health emergency is a major growing concern of the U.S. government. To address a potential incident and ensure that the government is prepared to respond to any subsequent civilian or military casualties, the U.S. Department of Health and Human Services and the Department of Defense have been charged with the development of medical countermeasures (MCMs) to treat the acute and delayed injuries that can result from radiation exposure. Because of the limited budgets in research and development and the high costs associated with bring promising approaches from the bench through advanced product development activities, and ultimately, to regulatory approval, the U.S. government places a priority on repurposing products for which there already exists relevant safety and other important information concerning their use in humans. Generating human data can be a costly and time-consuming process; therefore, the U.S. government has interest in drugs for which such relevant information has been established (e.g., products for another indication), and in determining if they could be repurposed for use as MCMs to treat radiation injuries as well as chemical and biological insults. To explore these possibilities, the National Institute of Allergy and Infectious Diseases (NIAID) convened a workshop including U.S. government, industry and academic subject matter experts, to discuss the challenges and benefits of repurposing products for a radiation indication. Topics covered included a discussion of U.S. government efforts (e.g. funding, stockpiling and making products available for study), as well unique regulatory and other challenges faced when repurposing patent protected or generic drugs. Other discussions involved lessons learned from industry on repurposing pre-license, pipeline products within drug development portfolios. This report reviews the information presented, as well as an overview of discussions from the meeting.

Differential Mobility Spectrometry-Mass Spectrometry (DMS-MS) in Radiation Biodosimetry: Rapid and High-Throughput Quantitation of Multiple Radiation Biomarkers in Nonhuman Primate Urine

High-throughput methods to assess radiation exposure are a priority due to concerns that include nuclear power accidents, the spread of nuclear weapon capability, and the risk of terrorist attacks. Metabolomics, the assessment of small molecules in an easily accessible sample, is the most recent method to be applied for the identification of biomarkers of the biological radiation response with a useful dose-response profile. Profiling for biomarker identification is frequently done using an LC-MS platform which has limited throughput due to the time-consuming nature of chromatography. We present here a chromatography-free simplified method for quantitative analysis of seven metabolites in urine with radiation dose-response using urine samples provided from the Pannkuk et al. (2015) study of long-term (7-day) radiation response in nonhuman primates (NHP). The stable isotope dilution (SID) analytical method consists of sample preparation by strong cation exchange-solid phase extraction (SCX-SPE) to remove interferences and concentrate the metabolites of interest, followed by differential mobility spectrometry (DMS) ion filtration to select the ion of interest and reduce chemical background, followed by mass spectrometry (overall SID-SPE-DMS-MS). Since no chromatography is used, calibration curves were prepared rapidly, in under 2 h (including SPE) for six simultaneously analyzed radiation biomarkers. The seventh, creatinine, was measured separately after 2500× dilution. Creatinine plays a dual role, measuring kidney glomerular filtration rate (GFR), and indicating kidney damage at high doses. The current quantitative method using SID-SPE-DMS-MS provides throughput which is 7.5 to 30 times higher than that of LC-MS and provides a path to pre-clinical radiation dose estimation. Graphical Abstract.

Successful Teaching of Radiobiology Students in the Medical Management of Acute Radiation Effects From Real Case Histories Using Clinical Signs and Symptoms and Taking Advantage of Recently Developed Software Tools

In 2015, the Bundeswehr Institute of Radiobiology organized a North Atlantic Treaty Organization exercise to examine the significance of clinical signs and symptoms for the prediction of late-occurring acute radiation syndrome. Cases were generated using either the Medical Treatment Protocols for Radiation Accident Victims (METREPOL, n = 167) system or using real-case descriptions extracted from a database system for evaluation and archiving of radiation accidents based on case histories (SEARCH, n = 24). The cases ranged from unexposed [response category 0 (RC 0, n = 89)] to mild (RC 1, n = 45), moderate (RC 2, n = 19), severe (RC 3, n = 20), and lethal (RC 4, n = 18) acute radiation syndrome. During the previous exercise, expert teams successfully predicted hematological acute radiation syndrome severity, determined whether hospitalization was required, and gave treatment recommendations, taking advantage of different software tools developed by the North Atlantic Treaty Organization teams. The authors provided the same data set to radiobiology students who were introduced to the medical management of acute effects after radiation exposure and the software tools during a class lasting 15 h. Corresponding to the previous results, difficulties in the discrimination between RC 0/RC 1 and RC 3/RC 4, as well as a systematic underestimation of RC 1 and RC 2, were observed. Nevertheless, after merging reported response categories into clinically relevant groups (RC 0-1, RC 2-3, and RC 3-4), it was found that the majority of cases (95.2% ± 2.2 standard deviations) were correctly identified and that 94.7% (±2.6 standard deviations) developing acute radiation syndrome and z96.4% (±1.6 standard deviations) requiring hospitalization were identified correctly. Two out of three student teams also provided a dose estimate. These results are comparable to the best-performing team of the 2015 North Atlantic Treaty Organization exercise (response category: 92.5%; acute radiation syndrome: 95.8%; hospitalization: 96.3%).

Comparison of target volume and clinical effects of four radiotherapy plans for acute lymphoblastic leukemia prior to hematopoietic stem cell transplantation

The present study aimed to investigate the variations in target volume, clinical reaction and transplantation effects of helical tomotherapy (HT)-total body irradiation (TBI), HT-total marrow and lymphatic irradiation (TMLI), intensity modulated radiotherapy (IMRT)-TBI and IMRT-TMLI within patients with acute lymphoblastic leukemia (ALL). A total of 18 patients with ALL were treated with the four aforementioned radiotherapy plans prior to hematopoietic stem cell transplantation. A planned prescribed dose of 12 Gy/6 Frequency was administered to determine planning target volume (PTV). Dosimetry evaluation indexes in PTV and organs at risk were analyzed. Comparison of clinical untoward effects and the results of transplantation among the four plans were performed. The conformity index of HT plans was significantly increased compared with those in IMRT plans. The mean dose (D) to the lung and volume ratio of target volume occupied by 5 Gy (V₅) in TMLI plans were lower compared with TBI plans. Doses to organs were controlled within the normal range. D_max, D_mean and V₅ of bilateral lungs and D_max and D_mean of bilateral crystalline lens in IMRT plans were significantly higher compared with HT plans. There were no significant differences in untoward effects among the four plans. Subsequent to symptomatic treatments with antiemetic, antidiarrheal and fluid infusion, untoward effects improved, and all patients demonstrated tolerance to these therapies. A total of six patients treated with HT-TBI revealed complete and successful transplantation; however, one patient following transplantation suffered from severe rejection and had succumbed to mortality due to severe infection. Patients treated with HT-TMLI, IMRT-TBI and IMRT-TMLI completed successful transplantation and no rejection responses were observed. Conformity of HT plans are higher than that of IMRT plans. The four radiotherapy plans exhibit similar clinical untoward effects and the same transplantation success rate. HT-TMLI is more feasible in dosimetry compared with HT-TBI, IMRT-TBI and IMRT-TMLI, which require further long-term observation.

Proposed "Exposure And Symptom Triage" (EAST) Tool to Assess Radiation Exposure After a Nuclear Detonation

ABSTRACTOne of the biggest medical challenges after the detonation of a nuclear device will be implementing a strategy to assess the severity of radiation exposure among survivors and to triage them appropriately. Those found to be at significant risk for radiation injury can be prioritized to receive potentially lifesaving myeloid cytokines and to be evacuated to other communities with intact health care infrastructure prior to the onset of severe complications of bone marrow suppression. Currently, the most efficient and accessible triage method is the use of sequential complete blood counts to assess lymphocyte depletion kinetics that correlate with estimated whole-body dose radiation exposure. However, even this simple test will likely not be available initially on the scale required to assess the at-risk population. Additional variables such as geographic location of exposure, sheltering, and signs and symptoms may be useful for initial sorting. An interdisciplinary working group composed of federal, state, and local public health experts proposes an Exposure And Symptom Triage (EAST) tool combining estimates of exposure from maps with clinical assessments and single lymphocyte counts if available. The proposed tool may help sort survivors efficiently at assembly centers near the damage and fallout zones and enable rapid prioritization for appropriate treatment and transport. (Disaster Med Public Health Preparedness. 2018; 12: 386-395).

Impact of Abbreviated Filgrastim Schedule on Survival and Hematopoietic Recovery after Irradiation in Four Mouse Strains with Different Radiosensitivity

Filgrastim (Neupogen^®, granulocyte-colony stimulating factor) is among the few countermeasures recommended for management of patients in the event of lethal total-body irradiation. Despite the plethora of studies using filgrastim as a radiation countermeasure, relatively little is known about the optimal dose schedule of filgrastim to mitigate radiation lethality. We evaluated the efficacy of filgrastim in improving 30-day survival of CD2F1 mice irradiated with a lethal dose (LD_70/30) in the AFRRI cobalt-60 facility. We tested different schedules of 1, 3, 5, 10 or 16 once-daily injections of filgrastim initiated one day after irradiation. Time optimization studies with filgrastim treatment were also performed, beginning 6-48 h postirradiation. Maximum survival was observed with 3 daily doses of 0.17 mg/kg filgrastim. Survival efficacy of the 3-day treatment was compared against the conventional 16-day filgrastim treatment after irradiation in four mouse strains with varying radiation sensitivities: C3H/HeN, C57BL/6, B6C3F1 and CD2F1. Blood indices, bone marrow histopathology and colony forming unit assays were also evaluated. Filgrastim significantly increased 30-day survival (P < 0.001) with a 3-day treatment compared to 16-day treatment. Filgrastim did not prevent cytopenia nadirs, but facilitated faster recovery of white blood cells, neutrophils, red blood cells, platelets, lymphocytes and hematocrits in all four strains. Accelerated hematopoietic recovery was also reflected in faster bone marrow reconstitution and significant increase in hematopoietic progenitors (P < 0.001) in all four mouse strains. These data indicate that prompt and abbreviated filgrastim treatment has potential benefit for triage in the event of a radiological incident for treating acute hematopoietic syndrome.

UNITED STATES DEPARTMENT OF HEALTH AND HUMAN SERVICES BIODOSIMETRY AND RADIOLOGICAL/NUCLEAR MEDICAL COUNTERMEASURE PROGRAMS

The United States Department of Health and Human Services (HHS) is fully committed to the development of medical countermeasures to address national security threats from chemical, biological, radiological, and nuclear agents. Through the Public Health Emergency Medical Countermeasures Enterprise, HHS has launched and managed a multi-agency, comprehensive effort to develop and operationalize medical countermeasures. Within HHS, development of medical countermeasures includes the National Institutes of Health (NIH), (led by the National Institute of Allergy and Infectious Diseases), the Office of the Assistant Secretary of Preparedness and Response/Biomedical Advanced Research and Development Authority (BARDA); with the Division of Medical Countermeasure Strategy and Requirements, the Centers for Disease Control and Prevention, and the Food and Drug Administration as primary partners in this endeavor. This paper describes various programs and coordinating efforts of BARDA and NIH for the development of medical countermeasures for radiological and nuclear threats.

A non-human primate model of radiation-induced cachexia

Cachexia, or muscle wasting, is a serious health threat to victims of radiological accidents or patients receiving radiotherapy. Here, we propose a non-human primate (NHP) radiation-induced cachexia model based on clinical and molecular pathology findings. NHP exposed to potentially lethal partial-body irradiation developed symptoms of cachexia such as body weight loss in a time- and dose-dependent manner. Severe body weight loss as high as 20–25% was observed which was refractory to nutritional intervention. Radiographic imaging indicated that cachectic NHP lost as much as 50% of skeletal muscle. Histological analysis of muscle tissues showed abnormalities such as presence of central nuclei, inflammation, fatty replacement of skeletal muscle, and muscle fiber degeneration. Biochemical parameters such as hemoglobin and albumin levels decreased after radiation exposure. Levels of FBXO32 (Atrogin-1), ActRIIB and myostatin were significantly changed in the irradiated cachectic NHP compared to the non-irradiated NHP. Our data suggest NHP that have been exposed to high dose radiation manifest cachexia-like symptoms in a time- and dose-dependent manner. This model provides a unique opportunity to study the mechanism of radiation-induced cachexia and will aid in efficacy studies of mitigators of this disease.

The Effect of Radiation Dose and Variation in Neupogen® Initiation Schedule on the Mitigation of Myelosuppression during the Concomitant GI-ARS and H-ARS in a Nonhuman Primate Model of High-dose Exposure with Marrow Sparing

A nonhuman primate (NHP) model of acute high-dose, partial-body irradiation with 5% bone marrow (PBI/BM5) sparing was used to assess the effect of Neupogen® [granulocyte colony stimulating factor (G-CSF)] to mitigate the associated myelosuppression when administered at an increasing interval between exposure and initiation of treatment. A secondary objective was to assess the effect of Neupogen® on the mortality or morbidity of the hematopoietic (H)- acute radiation syndrome (ARS) and concurrent acute gastrointestinal radiation syndrome (GI-ARS). NHP were exposed to 10.0 or 11.0 Gy with 6 MV LINAC-derived photons at approximately 0.80 Gy min. All NHP received medical management. NHP were dosed daily with control article (5% dextrose in water) initiated on day 1 post-exposure or Neupogen® (10 μg kg) initiated on day 1, day 3, or day 5 until recovery [absolute neutrophil count (ANC) ≥ 1,000 cells μL for three consecutive days]. Mortality in both the 10.0 Gy and 11.0 Gy cohorts suggested that early administration of Neupogen® at day 1 post exposure may affect acute GI-ARS mortality, while Neupogen® appeared to mitigate mortality due to the H-ARS. However, the study was not powered to detect statistically significant differences in survival. The ability of Neupogen® to stimulate granulopoiesis was assessed by evaluating key parameters for ANC recovery: the depth of nadir, duration of neutropenia (ANC < 500 cells μL) and recovery time to ANC ≥ 1,000 cells μL. Following 10.0 Gy PBI/BM5, the mean duration of neutropenia was 11.6 d in the control cohort vs. 3.5 d and 4.6 d in the day 1 and day 3 Neupogen® cohorts, respectively. The respective ANC nadirs were 94 cells μL, 220 cells μL, and 243 cells μL for the control and day 1 and day 3 Neupogen® cohorts. Following 11.0 Gy PBI/BM5, the duration of neutropenia was 10.9 d in the control cohort vs. 2.8 d, 3.8 d, and 4.5 d in the day 1, day 3, and day 5 Neupogen® cohorts, respectively. The respective ANC nadirs for the control and day 1, day 3, and day 5 Neupogen® cohorts were 131 cells μL, 292 cells μL, 236 cells μL, and 217 cells μL, respectively. Therefore, the acceleration of granulopoiesis by Neupogen® in this model is independent of the time interval between radiation exposure and treatment initiation up to 5 d post-exposure. The PBI/BM5 model can be used to assess medical countermeasure efficacy in the context of the concurrent GI- and H-ARS.

Increased Expression of Connective Tissue Growth Factor (CTGF) in Multiple Organs After Exposure of Non-Human Primates (NHP) to Lethal Doses of Radiation

Exposure to sufficiently high doses of ionizing radiation is known to cause fibrosis in many different organs and tissues. Connective tissue growth factor (CTGF/CCN2), a member of the CCN family of matricellular proteins, plays an important role in the development of fibrosis in multiple organs. The aim of the present study was to quantify the gene and protein expression of CTGF in a variety of organs from non-human primates (NHP) that were previously exposed to potentially lethal doses of radiation. Tissues from non-irradiated NHP and NHP exposed to whole thoracic lung irradiation (WTLI) or partial-body irradiation with 5% bone marrow sparing (PBI/BM5) were examined by real-time quantitative reverse transcription PCR, western blot, and immunohistochemistry. Expression of CTGF was elevated in the lung tissues of NHP exposed to WTLI relative to the lung tissues of the non-irradiated NHP. Increased expression of CTGF was also observed in multiple organs from NHP exposed to PBI/BM5 compared to non-irradiated NHP; these included the lung, kidney, spleen, thymus, and liver. These irradiated organs also exhibited histological evidence of increased collagen deposition compared to the control tissues. There was significant correlation of CTGF expression with collagen deposition in the lung and spleen of NHP exposed to PBI/BM5. Significant correlations were observed between spleen and multiple organs on CTGF expression and collagen deposition, respectively, suggesting possible crosstalk between spleen and other organs. These data suggest that CTGF levels are increased in multiple organs after radiation exposure and that inflammatory cell infiltration may contribute to the elevated levels of CTGF in multiple organs.

Comparing the Hematopoetic Syndrome Time Course in the NHP Animal Model to Radiation Accident Cases From the Database Search

Since controlled clinical studies on drug administration for the acute radiation syndrome are lacking, clinical data of human radiation accident victims as well as experimental animal models are the main sources of information. This leads to the question of how to compare and link clinical observations collected after human radiation accidents with experimental observations in non-human primate (NHP) models. Using the example of granulocyte counts in the peripheral blood following radiation exposure, approaches for adaptation between NHP and patient databases on data comparison and transformation are introduced. As a substitute for studying the effects of administration of granulocyte-colony stimulating factor (G-CSF) in human clinical trials, the method of mathematical modeling is suggested using the example of G-CSF administration to NHP after total body irradiation.

The Toll-Like Receptor 5 Agonist Entolimod Mitigates Lethal Acute Radiation Syndrome in Non-Human Primates

There are currently no approved medical radiation countermeasures (MRC) to reduce the lethality of high-dose total body ionizing irradiation expected in nuclear emergencies. An ideal MRC would be effective even when administered well after radiation exposure and would counteract the effects of irradiation on the hematopoietic system and gastrointestinal tract that contribute to its lethality. Entolimod is a Toll-like receptor 5 agonist with demonstrated radioprotective/mitigative activity in rodents and radioprotective activity in non-human primates. Here, we report data from several exploratory studies conducted in lethally irradiated non-human primates (rhesus macaques) treated with a single intramuscular injection of entolimod (in the absence of intensive individualized supportive care) administered in a mitigative regimen, 1-48 hours after irradiation. Following exposure to LD50-70/40 of radiation, injection of efficacious doses of entolimod administered as late as 25 hours thereafter reduced the risk of mortality 2-3-fold, providing a statistically significant (P<0.01) absolute survival advantage of 40-60% compared to vehicle treatment. Similar magnitude of survival improvement was also achieved with drug delivered 48 hours after irradiation. Improved survival was accompanied by predominantly significant (P<0.05) effects of entolimod administration on accelerated morphological recovery of hematopoietic and immune system organs, decreased severity and duration of thrombocytopenia, anemia and neutropenia, and increased clonogenic potential of the bone marrow compared to control irradiated animals. Entolimod treatment also led to reduced apoptosis and accelerated crypt regeneration in the gastrointestinal tract. Together, these data indicate that entolimod is a highly promising potential life-saving treatment for victims of radiation disasters.

Effects of a granulocyte colony stimulating factor, Neulasta, in mini pigs exposed to total body proton irradiation

Astronauts could be exposed to solar particle event (SPE) radiation, which is comprised mostly of proton radiation. Proton radiation is also a treatment option for certain cancers. Both astronauts and clinical patients exposed to ionizing radiation are at risk for loss of white blood cells (WBCs), which are the body's main defense against infection. In this report, the effect of Neulasta treatment, a granulocyte colony stimulating factor, after proton radiation exposure is discussed. Mini pigs exposed to total body proton irradiation at a dose of 2 Gy received 4 treatments of either Neulasta or saline injections. Peripheral blood cell counts and thromboelastography parameters were recorded up to 30 days post-irradiation. Neulasta significantly improved WBC loss, specifically neutrophils, in irradiated animals by approximately 60% three days after the first injection, compared to the saline treated, irradiated animals. Blood cell counts quickly decreased after the last Neulasta injection, suggesting a transient effect on WBC stimulation. Statistically significant changes in hemostasis parameters were observed after proton radiation exposure in both the saline and Neulasta treated irradiated groups, as well as internal organ complications such as pulmonary changes. In conclusion, Neulasta treatment temporarily alleviates proton radiation-induced WBC loss, but has no effect on altered hemostatic responses.

Pleiotrophin mediates hematopoietic regeneration via activation of RAS

Hematopoietic stem cells (HSCs) are highly susceptible to ionizing radiation-mediated death via induction of ROS, DNA double-strand breaks, and apoptotic pathways. The development of therapeutics capable of mitigating ionizing radiation-induced hematopoietic toxicity could benefit both victims of acute radiation sickness and patients undergoing hematopoietic cell transplantation. Unfortunately, therapies capable of accelerating hematopoietic reconstitution following lethal radiation exposure have remained elusive. Here, we found that systemic administration of pleiotrophin (PTN), a protein that is secreted by BM-derived endothelial cells, substantially increased the survival of mice following radiation exposure and after myeloablative BM transplantation. In both models, PTN increased survival by accelerating the recovery of BM hematopoietic stem and progenitor cells in vivo. PTN treatment promoted HSC regeneration via activation of the RAS pathway in mice that expressed protein tyrosine phosphatase receptor-zeta (PTPRZ), whereas PTN treatment did not induce RAS signaling in PTPRZ-deficient mice, suggesting that PTN-mediated activation of RAS was dependent upon signaling through PTPRZ. PTN strongly inhibited HSC cycling following irradiation, whereas RAS inhibition abrogated PTN-mediated induction of HSC quiescence, blocked PTN-mediated recovery of hematopoietic stem and progenitor cells, and abolished PTN-mediated survival of irradiated mice. These studies demonstrate the therapeutic potential of PTN to improve survival after myeloablation and suggest that PTN-mediated hematopoietic regeneration occurs in a RAS-dependent manner.

Randomized comparison of single dose of recombinant human IL-12 versus placebo for restoration of hematopoiesis and improved survival in rhesus monkeys exposed to lethal radiation

Background

The hematopoietic syndrome of the acute radiation syndrome (HSARS) is a life-threatening condition in humans exposed to total body irradiation (TBI); no drugs are approved for treating this condition. Recombinant human interleukin-12 (rHuIL-12) is being developed for HSARS mitigation under the FDA Animal Rule, where efficacy is proven in an appropriate animal model and safety is demonstrated in humans.

Methods

In this blinded study, rhesus monkeys (9 animals/sex/dose group) were randomized to receive a single subcutaneous injection of placebo (group 1) or rHuIL-12 at doses of 50, 100, 250, or 500 ng/kg (groups 2–5, respectively), without antibiotics, fluids or blood transfusions, 24–25 hours after TBI (700 cGy).

Results

Survival rates at Day 60 were 11%, 33%, 39%, 39%, and 50% for groups 1–5, respectively (log rank p < 0.05 for each dose vs. control). rHuIL-12 also significantly reduced the incidences of severe neutropenia, severe thrombocytopenia, and sepsis (positive hemoculture). Additionally, bone marrow regeneration following TBI was significantly greater in monkeys treated with rHuIL-12 than in controls.

Conclusions

Data from this study demonstrate that a single injection of rHuIL-12 delivered one day after TBI can significantly increase survival and reduce radiation-induced hematopoietic toxicity and infections. These data significantly advance development of rHuIL-12 toward approval under the Animal Rule as an effective stand-alone medical countermeasure against the lethal effects of radiation exposure.