Acute Radiation Syndrome (ARS)

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Acute Radiation Syndrome (ARS) involves severe, potentially lethal damage to the bone marrow’s ability to produce blood cells, as well as to other systems and organs. Severe damage to bone marrow makes victims vulnerable to life-threatening hemorrhage, infection and anemia.

Development of PLX-R18 in Acute Radiation Syndrome

As efficacy studies are not permitted in humans for this indication, studies are conducted via the FDA animal rule pathway in order to evaluate Pluristem’s PLX-R18 as a medical countermeasure for the treatment of the hematopoietic sub-syndrome of Acute Radiation Syndrome (ARS). Studies conducted and funded by the U.S. government (NIH, DOD).

  • A study is planned to support submission of a Biologics License Application (BLA) for PLX-R18 for this indication. Program funded by the U.S. government
  • The FDA has cleared Pluristem’s Investigational New Drug (IND) application for PLX-R18 in the treatment of ARS in case of nuclear events
  • FDA Orphan Drug Designation

PLX-R18 as a Potential Treatment for ARS

Several studies of PLX-R18 as a potential treatment of the hematopoietic sub-syndrome of Acute Radiation Syndrome (ARS) were completed under the support of the National Institute of Allergy and Infectious Diseases (NIAID), a part of the U.S. National Institutes of Health (NIH). NIAID studies showed that PLX-R18 administration resulted in a statistically significant improvement in the survival rate and recovery of blood cell production in animals exposed to high levels of radiation. Safety data showed that PLX-R18 cells did not affect non-irradiated animals, indicating an ability to treat individuals without determining their degree of exposure to radiation.

Additional studies of PLX-R18, in both ARS and other hematological indications, were conducted in collaboration with Charité Universitätsmedizin Berlin Institute of Medical Immunology, the Berlin-Brandenburg Center for Regenerative Therapies, Case Western Reserve University, Hadassah Hebrew University Medical Center, and Indiana University.

PLX-R18 as a Potential Prophylactic Countermeasure against ARS

Following the positive study results, conducted by NIH, Pluristem was approached by the U.S. Department of Defense (DOD) to evaluate PLX-R18 as a potential prophylactic countermeasure against ARS, administered prior to radiation exposure.  A series of studies was conducted in parallel to the ongoing project with the NIH. These animal studies demonstrated that PLX-R18, administered 24 hours before radiation exposure, and again 72 hours after exposure, resulted in a significant increase in survival rates, from 4% survival rate in the placebo group to 74% in the treated group. In addition, the data showed an increase in recovery of blood counts including platelets, neutrophils, white blood cells, and lymphocytes. Furthermore, histopathological analysis and hematopoietic progenitor clonogenic assay of tissues collected from irradiated animals show a significant increase in bone marrow cell numbers and improved regenerative capability in animals treated with PLX-R18.

In addition, Pluristem entered into collaboration agreement with Fukushima Medical University in Japan, to examine PLX-R18 cells for the treatment of hematological ARS and gastrointestinal (GI).

In parallel to animal studies, topline results from a first in-human Phase I study, also have demonstrated PLX-R18’s ability to increase blood cell recovery in all three cell lineages. This supports PLX-R18’s therapeutic potential to treat a variety of hematologic indications. Please click here to learn more.


PLX cell therapy was granted an orphan drug designation by the FDA for the treatment of ARS. The Orphan Drug Act provides for granting special status to a drug or biological product, to treat a rare disease or condition. The benefits of achieving Orphan Drug Designation include close guidance by the FDA, which may accelerate the path to potential marketing approval, orphan drug grants, tax credits, and 7-year market exclusivity upon marketing approval.

The FDA has also cleared Pluristem’s Investigational New Drug (IND) application for PLX-R18 in the treatment of ARS. The IND allows Pluristem to treat victims who may have been acutely exposed to high dose radiation due to nuclear attack or accident.