Medical Scientist researching blood samples

GI Acute Radiation Syndrome

What is Acute Radiation Syndrome?

A nuclear disaster, whether deliberate or accidental, has the potential to cause mass casualties. Acute Radiation Syndrome (ARS) occurs when there is substantial exposure to a high dose of radiation over a short period of time. Increasing doses of radiation are associated with both increasing organ damage and earlier and higher mortality levels.  

ARS is usually divided into 4 subcategories:

  • Hematopoietic ARS (H ARS) occurs from damage to the blood cells resulting in loss of immune fighting cells, red blood cells (causing anemia) and consequently severe infections can take hold. Symptoms are seen with exposure as low as 0.3 Gy. Exposure to 2.5 Gy radiation is expected to result in approximately 50% mortality within months without additional hematopoietic directed treatment.
  • Gastrointestinal ARS (GI ARS) occurs at higher dose levels. In addition to the hematopoietic damage, there is also damage to the cells lining the mouth, stomach and intestines, which results in dehydration and additional infection. Symptoms are seen with exposure as low as 6 Gy. Exposure to 10 Gy radiation is expected to result in 100% mortality within 2 weeks.
  • Cardiovascular / Central nervous system ARS occurs at even higher radiation exposure. Damage to the cells of the central nervous and cardiovascular systems  happens in parallel with the hematopoietic and gastrointestinal damage at these very high radiation levels. Symptoms are seen with exposure as low as 20 Gy. Exposure to >50 Gy radiation is expected to result in 100% mortality within 3 days.
  • Delayed effects of acute radiation exposure (DEARE) occurs with exposure across the radiation dose range and is caused by incorrect body repair processes yielding long term injury.

Exposure to high radiation dose levels are expected to decrease rapidly as distance from the epicenter of the nuclear incident is achieved. This means that more people will be exposed to H ARS than GI ARS and more people exposed to GI ARS than CNS ARS.

While in all cases of radiation damage, the initial damage is caused by cell death, often subsequent damage is caused by the repair processes of the body which are driven by inflammation and may be “over driven” by these inflammatory processes. As the hematopoietic system recovers, this “overdrive” scenario may become worse.

Some Quick Facts

More information on what to do in a radiation emergency can be found at the Centers for Disease Control and Prevention (CDC).

Symptoms of Acute Radiation Syndrome

ARS usually progresses in 4 distinct phases irrespective of the level of radiation exposure. The higher the radiation dose, the more rapidly each stage progresses:

  1. Prodromal stage (N-V-D stage): characterized by nausea and vomiting as well as anorexia and at higher dose levels diarrhea. This may occur from within minutes to days for exposure and may last from minutes to days.
  2. Latent stage: the patients looks and feels generally well. This stage can last from hours to weeks, again depending on exposure
  3. Manifest illness stage: Symptoms specific to the syndrome generally occur in this stage, including:
    1. H ARS – generally feeling ill, suppressed appetite, nausea, vomiting, drop in blood cell counts, infection and hemorrhage (depending on dose level)
    2. GI ARS – generally feeling ill, suppressed appetite, severe diarrhea, fever, dehydration, electrolyte imbalance and infection
    3. CNS ARS – return of watery diarrhea, convulsions, coma
  4. Recovery: last from several weeks up to 2 years

Treatment Options

Currently there is an approved therapeutic for H ARS:

  • Filgrastim is approved for use in a mass casualty event to support the re-induction of hematopoietic immune cells which are damaged in the initial radiation exposure. This also reduces the infection rate, which then reduces the mortality rate. However, there is no impact on damage to the gastrointestinal or CNS systems.

There are NO approved treatments for GI ARS or for damage to the CNS.

Treatments for GI ARS may substantially improve both survival and long term damage from nuclear mass casualty events. GI ARS is expected to occur in a large proportion of the population in a nuclear mass casualty event, making treatments for GI ARS a clear unmet medical need.

Where Soligenix Comes in

While in all cases of radiation damage, the initial damage is caused by cell death, often subsequent damage is caused by the repair processes of the body which are driven by inflammation and may be “over driven” by these inflammatory processes. As the hematopoietic system recovers, this “overdrive” scenario may become worse.

OrbeShield® is a topical anti-inflammatory treatment for the stomach and intestines which may help address deleterious inflammation in the gastrointestinal system. The active ingredient is beclomethasone dipropionate (BDP).

BDP is a steroid which can reduce local inflammation but has limited ability to penetrate the body.

By providing a formulation of BDP which coats the inside of the gut with steroid, but isn’t absorbed into the bloodstream, the systemic side effects of steroid treatment (including increased risk of infection) are reduced.

OrbeShield® may mitigate the “inflammatory overdrive” occurring in GI ARS, allowing the recovering intestinal cells to structure themselves correctly while reducing long term side effects.

Helpful Resources

Information on radiation emergencies and acute radiation syndrome is also available at the following sites: