Treatment Of Acute Radiation Syndrome Research Articles

Orphan designation: melatonin, Treatment of acute radiation syndrome

Orphan designation: melatonin, Treatment of acute radiation syndrome

Orphan designation: melatonin, Treatment of acute radiation syndrome

Orphan designation: melatonin, Treatment of acute radiation syndrome

Prospective, Multi-Center, Phase I Clinical Trial of PLX-R18 Placental Expanded Adherent Stromal Cells in Subjects with Incomplete Hematopoietic Recovery after Hematopoietic Cell Transplantation

Background: Successful engraftment remains a challenge in hematopoietic cell transplantation (HCT) for some patients. Salvage approaches, including use of recombinant hematopoietic growth factors, cytokine therapy, CD34+-selected progenitor cell boosts, or second or subsequent HCT, are successful only in a minority of patients, and patients are exposed to prolonged blood products transfusions. With our successful pre-clinical rodent and Rhesus Macaques total body irradiation injury-induced marrow failure models (Metheny, Front Med 2018; Sher, Cell Transplantation 2018; Sher, Blood 2017), this prospective, multi-center, phase I clinical trial is evaluating the safety of PLX-R18 cells used to improve peripheral blood counts in patients who have experienced incomplete hematopoietic recovery after HCT. PLX-R18 cells are human placental-derived adherent stromal cells that are predominantly of fetal origin, expressing CD105, CD73 and CD29, and lacking surface expression of CD45, CD34, CD14, CD19, HLA-DR, CD31 (endothelial marker) and GlyA (erythrocyte cell marker). PLX-R18 also do not express HLA class II molecules (HLA-DP, DQ, and DR) and co-stimulatory markers (CD80, CD86, and CD40). PLX-R18 cells secrete MCP-1, IL-6, and IL-8 and had been shown to stimulate migration of bone marrow cells in vitro. Cells are grown ex vivo, under GMP conditions, using a 3-dimensional system, and are administered as several intramuscular (IM) injections. PLX-R18 cells already are approved for treatment of acute radiation syndrome (ARS) under an IND.Methods: This is a multi-center, open label, dose-escalation, phase 1 trial (ClinicalTrials.gov: NCT03002519). Eligibility criteria include patients age ≥18 years who underwent either an autologous (auto) or an allogeneic (allo) HCT but had incomplete hematopoietic recovery at 4 months post-transplant, defined as failure to maintain either hemoglobin (Hb) >8 g/dL and/ or neutrophil count (ANC) >1,000/µL and/or platelet count (Plt) (unsupported) >50,000/µL. Other eligibility criteria include ECOG performance status of 0-2, no evidence of underlying malignancy at time of enrollment, no active infection, and no evidence of grade 3-4 acute or severe chronic GvHD. The PLX-R18 cells, cryopreserved in DMSO and human serum albumin in Plasma-Lyte, are thawed and injected IM in multiple locations - half into the gluteus medius muscle on one side and half to the thigh muscles on the contralateral side. A total of 24 subjects are planned to be enrolled into 3 dose escalating cohorts: low (n=3) given 1 million cells/kg; intermediate (n=6) at 2 million cells/kg and high (n=15) dosed at 4 million cells/kg each. The assigned dose is given twice, 1 week apart; cohorts are recruited sequentially and progression to the next cohort is based on the safety assessment of its predecessor. Adverse event is graded using the CTCAE criteria of the NCI. As of July 2018, all 3 patients of cohort 1 were treated (with sufficient follow-up), as well as 3 out of the 6 subjects planned for the 2nd cohort, and data of the first cohort are presented herein.Results: Cohort 1 (low-dose) - 3 subjects (ages 43, 48 and 55 years old) who had an allo (n=2) or auto (n=1) HCT received two IM administrations of PLX-R18, 1 million cells/kg each within a 1-week interval. 67 Adverse Events (AEs) were recorded. 64.3% of the AEs were grade 1, 30.9% were grade 2, 3.6% were grade 3 and 1.2% were grade 4. One patient suffered from 3 Serious AEs (immune thrombocytopenic purpura, bacteremia and migraine), all assessed as not related to treatment. Most frequent related AE was transient injection site pain, experienced by all 3 patients. See patients' details and blood counts in the table and graphs.Conclusions: Treatment with PLX-R18 generally was well-tolerated and most frequent adverse events were injection site reactions, which were all reversible without sequelae. The trial continues to accrue patients and the next dosing cohort (intermediate dose) is at 2 million cells/kg.Upon completion, a larger phase II trial will be considered in the same indication using the optimal dose. Other potential uses include PLX-R18 therapy in Acute Radiation Syndrome, Bone marrow failure, and in HCT as a “pan” cytokine for rapid count recovery. [Display omitted] DisclosuresLazarus:Pluristem Ltd.: Consultancy. Zuckerman:Cellect Biotherapeutics Ltd: Consultancy. McGuirk:Novartis Pharmaceuticals Corporation: Honoraria, Other: speaker, Research Funding; Fresenius Biotech: Research Funding; Kite Pharma: Honoraria, Other: travel accommodations, expenses, speaker ; Gamida Cell: Research Funding; Astellas Pharma: Research Funding; Pluristem Ltd: Research Funding; Bellicum Pharmaceuticals: Research Funding. Rosen:Pluristem: Employment.

Neulasta Regimen for the Hematopoietic Acute Radiation Syndrome: Effects Beyond Neutrophil Recovery

Understanding the physiopathology underlying the acute radiation syndrome (ARS) and the mechanism of action of drugs known to ameliorate ARS is expected to help identify novel countermeasure candidates and improve the outcome for victims exposed to radiation. Granulocyte colony-stimulating factor (G-CSF) has been approved by the US Food and Drug Administration for treatment of hematopoietic ARS (H-ARS) because of its ability to alleviate myelosuppression. Besides its role in hematopoiesis, G-CSF is known to protect the cardiovascular and neurologic systems, to attenuate vascular injury and cardiac toxicity, to preserve gap junction function, and to modulate inflammation and oxidative stress. Here, we characterized the protective effects of G-CSF beyond neutrophil recovery in minipigs exposed to H-ARS doses. Twenty male Göttingen minipigs were exposed to total body, acute ionizing radiation. Animals received either pegylated G-CSF (Neulasta) or dextrose at days 1 and 8 after irradiation. Survival was monitored over a 45-day period. Neulasta decreased mortality compared with the control, reduced nadir and duration of neutropenia, and lowered prevalence of organ hemorrhage and frank bleeding episodes. Neulasta also increased plasma concentration of IGF-1 hormone, activated the cardiovascular protective IGF-1R/PI3K/Akt/eNOS/NO pathway, and enhanced membrane expression of VE-cadherin in the heart, improving vascular tone and barrier function. Expression of the acute phase protein CRP, a mediator of cardiovascular diseases and a negative regulator of the IGF-1 pathway, was also induced but at much lower extent compared with IGF-1. Activity of catalase and superoxide dismutase (SOD-1) was only marginally affected, whereas activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase was downregulated. In addition to a neutrophilic effect, amelioration of endothelial homeostasis and barrier function and reduction in NADPH oxidase contribute to the beneficial effects of Neulasta for the treatment of H-ARS.

An update on sargramostim for treatment of acute radiation syndrome.

The potential use by terrorists of an improvised nuclear device, a radiological dispersal device, or an unintended nuclear/radiological accident in heavily populated areas is a national security threat of major consequences. Although this type of security threat is considered to be low-risk, it would have a devastating impact. Health issues would be a major concern; medical care would be necessary for all those who received considerable radiation exposure (> 1 Gy) leading to hematopoietic acute radiation syndrome (ARS). In the past few years, the U.S. Food and Drug Administration (FDA) has approved for such radiation exposure contingencies recombinant human granulocyte colony-stimulating factor (rhG-CSF, filgrastim, Neupogen), PEGylated rhG-CSF (PEGylated filgrastim, Neulasta) and granulocyte-macrophage colony-stimulating factor (rhGM-CSF, sargramostim, Leukine) following the FDA's Animal Rule guidance. In this article, we have briefly reviewed the consequences of exposure to acute, potentially lethal doses of radiation and its pathologic sequelae, as well as ARS and the latest of the FDA-approved recombinant growth factors, namely sargramostim (Leukine), as a new treatment option for the subclinical, hematopoietic syndrome component of ARS. The nature of the recombinant and the preclinical and clinical research that preceded approval by the FDA are presented, as well as its use in the treatment of victims of radiation accidents.

A sharp, robust, and quantitative method by liquid chromatography tandem mass spectrometry for the measurement of EAD for acute radiation syndrome and its application.

17-Ethinyl-3,17-dihydroxyandrost-5-ene (EAD) is an agent designed for the treatment of acute radiation syndrome (ARS). Given its vital role played in the prevention and mitigation of ARS, the development of a sharp, sensitive and robust liquid chromatography tandem mass spectrometry (LC-MS/MS) method to monitor the metabolism of EAD in vivo was crucial. A new method was constructed and validated for the determination of EAD with the internal standard of androst-5-ene-3β,17β-diol (5-AED). The blood samples were precipitated with methanol, centrifuged, from which the supernatant was separated on UPLC with C18 column and eluted in gradient with acetonitrile and Milli-Q water both containing 0.1% formic acid (FA). Quantification was performed by a triple quadrupole mass spectrometer with electro spray ionization (ESI) in multiple reactive monitoring (MRM) positive mode. A good linearity was obtained with R>0.99 for EAD within its calibration range from 5 to 1000ngmL-1 with a lowest limit of quantification (LLOQ) of 5ngmL-1. Inter- and intra-day accuracy and precision of three levels of quality control (QC) samples were within the range of 15%, while the LLOQ was within 20%. Samples were stable under the circumstances of the experiments. The method was simple, accurate and robust applied to determine the concentrations of EAD in Wistar rat after a single administration of EAD orally at the dose of 100mgkg-1.

Mesenchymal stem cell therapy for acute radiation syndrome.

Acute radiation syndrome affects military personnel and civilians following the uncontrolled dispersal of radiation, such as that caused by detonation of nuclear devices and inappropriate medical treatments. Therefore, there is a growing need for medical interventions that facilitate the improved recovery of victims and patients. One promising approach may be cell therapy, which, when appropriately implemented, may facilitate recovery from whole body injuries. This editorial highlights the current knowledge regarding the use of mesenchymal stem cells for the treatment of acute radiation syndrome, the benefits and limitations of which are under investigation. Establishing successful therapies for acute radiation syndrome may require using such a therapeutic approach in addition to conventional approaches.

Calculation of dose conversion factors for doses in the fingernails to organ doses at external gamma irradiation in air

Absorbed doses to fingernails and organs were calculated for a set of homogenous external gamma-ray irradiation geometries in air. The doses were obtained by stochastic modeling of the ionizing particle transport (Monte Carlo method) for a mathematical human phantom with arms and hands placed loosely along the sides of the body. The resulting dose conversion factors for absorbed doses in fingernails can be used to assess the dose distribution and magnitude in practical dose reconstruction problems.For purposes of estimating dose in a large population exposed to radiation in order to triage people for treatment of acute radiation syndrome, the calculated data for a range of energies having a width of from 0.05 to 3.5 MeV were used to convert absorbed doses in fingernails to corresponding doses in organs and the whole body as well as the effective dose. Doses were assessed based on assumed rates of radioactive fallout at different time periods following a nuclear explosion.

Granulocyte colony-stimulating factor in the treatment of acute radiation syndrome: a concise review.

This article concisely summarizes data on the action of one of the principal and best known growth factors, the granulocyte colony-stimulating factor (G-CSF), in a mammalian organism exposed to radiation doses inducing acute radiation syndrome. Highlighted are the topics of its real or anticipated use in radiation accident victims, the timing of its administration, the possibilities of combining G-CSF with other drugs, the ability of other agents to stimulate endogenous G-CSF production, as well as of the capability of this growth factor to ameliorate not only the bone marrow radiation syndrome but also the gastrointestinal radiation syndrome. G-CSF is one of the pivotal drugs in the treatment of radiation accident victims and its employment in this indication can be expected to remain or even grow in the future.

The Gottingen Minipig Is a Model of the Hematopoietic Acute Radiation Syndrome: G-Colony Stimulating Factor Stimulates Hematopoiesis and Enhances Survival From Lethal Total-Body γ-Irradiation

We are characterizing the Gottingen minipig as an additional large animal model for advanced drug testing for the acute radiation syndrome (ARS) to enhance the discovery and development of novel radiation countermeasures. Among the advantages provided by this model, the similarities to human hematologic parameters and dynamics of cell loss/recovery after irradiation provide a convenient means to compare the efficacy of drugs known to affect bone marrow cellularity and hematopoiesis. Male Gottingen minipigs, 4 to 5 months old and weighing 9 to 11 kg, were used for this study. We tested the standard off-label treatment for ARS, rhG-CSF (Neupogen, 10 μg/kg/day for 17 days), at the estimated LD70/30 total-body γ-irradiation (TBI) radiation dose for the hematopoietic syndrome, starting 24 hours after irradiation. The results indicated that granulocyte colony stimulating factor (G-CSF) enhanced survival, stimulated recovery from neutropenia, and induced mobilization of hematopoietic progenitor cells. In addition, the administration of G-CSF resulted in maturation of monocytes/macrophages. These results support continuing efforts toward validation of the minipig as a large animal model for advanced testing of radiation countermeasures and characterization of the pathophysiology of ARS, and they suggest that the efficacy of G-CSF in improving survival after total body irradiation may involve mechanisms other than increasing the numbers of circulating granulocytes.

Effects of recombinant human granulocyte colony-stimulating factor on central and peripheral T lymphocyte reconstitution after sublethal irradiation in mice

Granulocyte colony-stimulating factor (G-CSF) is one of the most critical cytokines used for the treatment of acute radiation syndrome (ARS). In addition to the hematopoietic effects of G-CSF on the differentiation and proliferation of myeloid progenitor cells, G-CSF is also known to have immunomodulatory effects. The aim of the present study was to investigate whether G-CSF could accelerate central and peripheral T lymphocyte recovery after a sublethal dose of irradiation. Female BALB/c mice were subjected to 6 Gy of total body irradiation and then were treated with either 100 μg/kg G-CSF or an equal volume of PBS once daily for 14 days. Percentages of thymocyte subpopulations including CD4 − CD8 − , CD4 + CD8 + , CD4 + CD8− and CD4 − CD8+ T cells, peripheral CD3 + , CD4+ and CD8+ cells were analyzed by flow cytometry. Recent thymic emigrants (RTEs) were assessed by real-time polymerase chain reaction (PCR) using primers specific to the 257-bp T cell receptor rearrangement excision circles (sjTRECs). The proliferative capacity of splenic mononuclear cells upon exposure to ConA was measured by using the Cell Count Kit-8 (CCK-8). G-CSF treatment promoted thymocyte regeneration, accelerated the recovery of CD4 + CD8+ cells and increased the frequency of thymocyte sjTRECs. These effects were more prominent at early time points (Day 28) after irradiation. G-CSF also increased the rate of recovery of peripheral CD3 + , CD4+ and CD8+ cells and shortened the period of severe lymphopenia following irradiation. G-CSF also increased the splenic mononuclear cell mitotic responsiveness to ConA more than control-treated cells. Our results show that G-CSF accelerates T cell recovery through both thymic-dependent and thymic-independent pathways, which could be used to increase the rate of immune reconstitution after sublethal irradiation.

Acute radiation syndrome (ARS) – treatment of the reduced host defense

BackgroundThe current radiation threat from the Fukushima power plant accident has prompted rethinking of the contingency plan for prophylaxis and treatment of the acute radiation syndrome (ARS). The well-documented effect of the growth factors (granulocyte colony-stimulating factor [G-CSF] and granulocyte-macrophage colony-stimulating factor [GM-CSF]) in acute radiation injury has become standard treatment for ARS in the United States, based on the fact that growth factors increase number and functions of both macrophages and granulocytes.MethodsReview of the current literature.ResultsThe lungs have their own host defense system, based on alveolar macrophages. After radiation exposure to the lungs, resting macrophages can no longer be transformed, not even during systemic administration of growth factors because G-CSF/GM-CSF does not penetrate the alveoli. Under normal circumstances, locally-produced GM-CSF receptors transform resting macrophages into fully immunocompetent dendritic cells in the sealed-off pulmonary compartment. However, GM-CSF is not expressed in radiation injured tissue due to defervescence of the macrophages. In order to maintain the macrophage’s important role in host defense after radiation exposure, it is hypothesized that it is necessary to administer the drug exogenously in order to uphold the barrier against exogenous and endogenous infections and possibly prevent the potentially lethal systemic infection, which is the main cause of death in ARS.RecommendationPreemptive treatment should be initiated after suspected exposure of a radiation dose of at least <2 Gy by prompt dosing of 250–400 μg GM-CSF/m2 or 5 μg/kg G-CSF administered systemically and concomitant inhalation of GM-CSF < 300 mcg per day for at least 14–21 days.ConclusionThe present United States standard for prevention and treatment of ARS standard intervention should consequently be modified into the combined systemic administration of growth factors and inhaled GM-CSF to ensure the sustained systemic and pulmonary host defense and thus prevent pulmonary dysfunction.

Biological dosimetry by the triage dicentric chromosome assay – Further validation of international networking

Biological dosimetry is an essential tool for estimating radiation doses received to personnel when physical dosimetry is not available or inadequate. The current preferred biodosimetry method is based on the measurement of radiation-specific dicentric chromosomes in exposed individuals' peripheral blood lymphocytes. However, this method is labour-, time- and expertise-demanding. Consequently, for mass casualty applications, strategies have been developed to increase its throughput. One such strategy is to develop validated cytogenetic biodosimetry laboratory networks, both national and international. In a previous study, the dicentric chromosome assay (DCA) was validated in our cytogenetic biodosimetry network involving five geographically dispersed laboratories. A complementary strategy to further enhance the throughput of the DCA among inter-laboratory networks is to use a triage DCA where dose assessments are made by truncating the labour-demanding and time-consuming metaphase-spread analysis to 20 to 50 metaphase spreads instead of routine 500 to 1000 metaphase spread analysis. Our laboratory network also validated this triage DCA, however, these dose estimates were made using calibration curves generated in each laboratory from the blood samples irradiated in a single laboratory. In an emergency situation, dose estimates made using pre-existing calibration curves which may vary according to radiation type and dose rate and therefore influence the assessed dose. Here, we analyze the effect of using a pre-existing calibration curve on assessed dose among our network laboratories. The dose estimates were made by analyzing 1000 metaphase spreads as well as triage quality scoring and compared to actual physical doses applied to the samples for validation. The dose estimates in the laboratory partners were in good agreement with the applied physical doses and determined to be adequate for guidance in the treatment of acute radiation syndrome.

Biological Dosimetry by the Triage Dicentric Chromosome Assay: Potential Implications for Treatment of Acute Radiation Syndrome in Radiological Mass Casualties

Biological dosimetry is an essential tool for estimating radiation dose. The dicentric chromosome assay (DCA) is currently the tool of choice. Because the assay is labor-intensive and time-consuming, strategies are needed to increase throughput for use in radiation mass casualty incidents. One such strategy is to truncate metaphase spread analysis for triage dose estimates by scoring 50 or fewer metaphases, compared to a routine analysis of 500 to 1000 metaphases, and to increase throughput using a large group of scorers in a biodosimetry network. Previously, the National Institutes for Allergies and Infectious Diseases (NIAID) and the Armed Forces Radiobiology Research Institute (AFRRI) sponsored a double-blinded interlaboratory comparison among five established international cytogenetic biodosimetry laboratories to determine the variability in calibration curves and in dose measurements in unknown, irradiated samples. In the present study, we further analyzed the published data from this previous study to investigate how the number of metaphase spreads influences dose prediction accuracy and how this information could be of value in the triage and management of people at risk for the acute radiation syndrome (ARS). Although, as expected, accuracy decreased with lower numbers of metaphase spreads analyzed, predicted doses by the laboratories were in good agreement and were judged to be adequate to guide diagnosis and treatment of ARS. These results demonstrate that for rapid triage, a network of cytogenetic biodosimetry laboratories can accurately assess doses even with a lower number of scored metaphases.

Hydrogen therapy may be an effective and specific novel treatment for acute radiation syndrome

Hydrogen is the most abundant chemical element in the universe, however, it is seldom regarded as a therapeutic gas. Recent studies show that inhaled hydrogen gas (H(2)) has antioxidant and antiapoptotic activities that protect the brain against ischemia-reperfusion injury and stroke by selectively reducing hydroxyl and peroxynitrite radicals. It is also well known that more than a half of the ionizing radiation-induced cellular damage is caused by hydroxyl radicals. Studies have show that reducing hydroxyl radicals can significantly improve the protection of cells from radiation damage. In like manner, we hypothesize that hydrogen therapy may be an effective, specific and unique treatment for acute radiation syndrome.

Pharmacological Countermeasures for the Acute Radiation Syndrome

The acute radiation syndrome (ARS) is defined as the signs and symptoms that occur within several months after exposure to ionizing radiation (IR). This syndrome develops after total- or partial-body irradiation at a relatively high dose (above about 1 Gy in humans) and dose rate. Normal tissue injuries induced by IR differ depending on the target organ and cell type. Organs and cells with high sensitivity to radiation include the skin, the hematopoietic system, the gut, the spermatogenic cells and the vascular system. Exposure to IR causes damage to DNA, protein, and lipids in mammalian cells, as well as increased mitochondria-dependent generation of reactive oxygen species (ROS), with subsequent cell cycle checkpoint arrest, apoptosis, and stress-related responses. DNA double strand breaks (DSBs) are a primary lethal lesion induced by IR. The cellular response to damage is complex and relies on simultaneous activation of a number of signaling networks. Among these, the activation of DNA non-homologous end-joining (NHEJ) and homologous recombination (HR), and signaling pathways containing ataxia telangiectasia mutated (ATM), play important roles. The transcription factor NFkappaB has emerged as a pro-survival actor in response to IR in ATM and p53-induced protein with a death domain (PIDD) cascades. Although radiation-induced ARS has been well documented at the clinical level, and mechanistic information is accumulating, successful prophylaxis and treatment for ARS is problematic, even with the use of supportive care and growth factors. There is a pressing need to develop radiation countermeasures that can be used both in the clinic, for small-scale incidents, and outside the clinic, in mass casualty scenarios. In this review we summarize recent information on intracellular and extracellular signaling pathways relevant to radiation countermeasure research.

New therapy for the prevention and prophylactic treatment of acute radiation syndrome

The risk of military personnel, first responders and civilians being exposed to lethal doses of ionising radiation is greater now than it was during the Cold War. Due to the increasing likelihood of exposure to ionising radiation, the need for medical radiation countermeasures has been recognised as a high priority in the US. At present, no approved drugs are available for the prevention or treatment of acute radiation syndrome, even though this is a top national priority. One promising investigational drug candidate for the indication of radioprotection is BIO 300. This agent is a medical radiation countermeasure that is intended for use as a prophylactic treatment for acute radiation syndrome. Novel products (such as BIO 300) that provide prophylactic protection are designed to be shelf stable for several years, more rapidly distributed and easily administered orally with a minimum of medical supervision.

Revisiting therapeutic strategies in radiation casualties

Nuclear/radiological threats have evolved and scenarios for terrorist attacks involving radioactive material have been identified as complex situations. Mass casualty scenarios may happen, and individuals may be exposed to intentionally hidden sources of high activity, resulting in delayed diagnosis and treatment of acute radiation syndrome (ARS). Moreover, ARS must be considered as an emergency in order to better anticipate delayed radiation toxicity. In this context, therapeutic strategies in radiation casualties have to be revisited and new pharmacological approaches developed. B6D2F1 mice were total-body irradiated (TBI) with a 9 Gy gamma dose and then received intraperitoneal doses of either early (stem cell factor + FLT-3 ligand + thrombopoietin + interleukin-3 [SFT3] +/- keratinocyte growth factor (KGF); stem cell factor + erythropoietin + Peg-filgrastim [SEG]) or delayed treatments (SFT3 +/- KGF, erythropoietin, or hyaluronic acid). Survival was monitored and bone marrow hematopoiesis evaluated at 300 days following early treatments. SFT3 anti-apoptotic cytokine combination administered early (2 hours and 24 hours) after lethal TBI induced 60% survival versus 5% in controls. Early SEG treatment may be an alternative to SFT3 in terms of survival (55%), but SEG benefit might be obtained at the expense of long-term hematopoiesis. SFT3 + KGF induced 75% survival. No effectiveness was observed, over antimicrobial supportive care, when administration of SFT3 or its tested combinations was delayed at 48 hours. As a potentially multi-organ failure, ARS requires global therapy, beyond the hematopoietic syndrome, which may include pleiotropic cytokines such as KGF.

HE2100 (androst-5-ene-3β, 17β-diol), an Adrenal Hormone, Protects Rhesus Macaques from Lethal Total Body Irradiation (TBI)- Induced Severe Neutropenia and Thrombocytopenia.

HE2100 (androst-5-ene-3,17β-diol) is a naturally occurring adrenal steroid hormone being developed for the treatment of acute radiation syndrome (ARS). Previous studies of lethally irradiated rodents demonstrated a significant survival advantage for HE2100 treated groups (Whitnall et. al., Int. J. Immunopharm. 2000). In HE2100 treated rhesus macaques we have previously reported a tri-lineage recovery (neutrophils, platelets and red blood cells) of bone marrow following sublethal irradiation and a reduction in lethality following 6.00 Gy 60Co TBI. Studies were conducted to further investigate the effects of this compound to prevent very severe radiation induced cytopenias and to enhance survival following TBI. Results refer to absolute neutrophil count <500 cells/μL and platelet count <20,000 platelets/μL. We report a meta-analysis of five studies involving 100 animals receiving TBI in the range of 6.00 – 6.34 Gy 60Co. Animals were either untreated, or given vehicle, or 5–15 mg/kg of HE2100 IM for 5 consecutive days starting 2–3 hours after TBI. No clinical support such as transfusions or antibiotics was given in any of the studies. Animals were continuously monitored for core body temperature with an implanted telemetric thermometer. Blood counts were measured daily during expected cytopenic days. Studies were performed after Institutional Animal Care and Use Committee review and approval, observing strict euthanasia criteria. HE2100 afforded protection of the unsupported animals from lethal irradiation, decreasing the lethality overall, from 42% in the control group to 22% in the HE2100 treated group (mid-p=0.044). All deaths occurred between Study Days 14 and 26. The majority of animals (28/32, 87.5%) died by Study Day 20 reflective of ARS. Based on an analysis of days at risk, the cumulative incidence of days of severe neutropenia was reduced by 1.10 days (p=0.002), whereas the cumulative incidence of days of thrombocytopenia was reduced by 2.31 days (p=0.02). No cytopenias were recorded after Study Day 26 on surviving animals. Death in these animals correlated with severe thrombocytopenia and opportunistic infections from the gut and skin flora leading to hemorrhagic sepsis as the primary cause. HE2100-related increases in cellularity were noted in the bone marrow, spleen, and lymph nodes on Study Day 40. HE2100 appears to stimulate multi-lineage recovery, via early bone marrow hematopoietic stem cell progenitors following TBI injury in rhesus macaques.

Comparison of autologous cell therapy and granulocyte-colony stimulating factor (G-CSF) injection vs. G-CSF injection alone for the treatment of acute radiation syndrome in a non-human primate model

To compare the efficacy of autologous cell therapy after irradiation combined with granulocyte-colony stimulating factor (G-CSF) injections with G-CSF treatment alone in a heterogeneous model of irradiation representative of an accidental situation. Non-human primates were irradiated at 8.7 Gy whole-body dose with the right arm shielded to receive 4.8 Gy. The first group of animals received G-CSF (lenograstim) injections starting 6 h after irradiation, and a second group received a combination of G-CSF (lenograstim) injections and autologous expanded hematopoietic cells. Animals were followed up for blood cell counts, circulating progenitors, and bone marrow cellularity. No significant differences were seen between the two treatment groups, whatever the parameter observed: time to leukocyte or platelet recovery and duration and severity of aplasia. Our results indicated that identical recovery kinetic was observed when irradiated animals are treated with G-CSF independently of the reinjection of ex vivo expanded autologous hematopoietic cells. Thus G-CSF injections might be chosen as a first-line therapeutic strategy in the treatment of accidental acute radiation victims.