- Cell danger response theory may explain development of ASD, to assess safety of suramin
Boys who received a single dose of the drug showed measurable, though not permanent, improvements in autism spectrum disorder (ASD) symptoms.
ASD is considered a complex, wide-spectrum disorder because the many symptoms can vary in combination and intensity. For this reason, no two people with ASD will have exactly the same symptoms.
Some of the behavioural symptoms of ASD include:
Difficulty making eye contact
Delayed language development
Difficulty holding a conversation
Intense or obsessive interests
Problems with planning and reasoning
Poor motor skills
Difficulty processing sensory signals
Robert K Naviaux, a professor of medicine, paediatrics, and pathology at UCSD School of Medicine and first author of the new study, believes that the idea of an abnormal “cell danger response” may offer a unifying theory for the development of ASD.
The cell danger response is a normal signal sent out by all cells when they suffer injury or stress. Its purpose, says Prof Naviaux, “is to help protect the cell and jump-start the healing process.” The signal causes the cell to stiffen its cell walls, stop talking to other cells, and withdraw until the threat subsides.
However, Prof Naviaux explains that the cell danger response “can get stuck” and stop the completion of the cell’s healing cycle. The cell persists in the threat response state, which can “permanently alter the way the cell responds to the world.”
The effect at the molecular level is to disrupt the chemistry of cell equilibrium and cause chronic disease. Prof Naviaux says that “when this happens during early child development, it causes autism and many other chronic childhood disorders.”
Cells activate the cell danger response by releasing a small molecule from their energy-making compartments, or mitochondria. The release of this molecule is what acts as the danger signal, and it keeps being released as long as the cell danger response is active.
Suramin blocks the ability of the small molecule to release the danger signal. The effect, says Prof Naviaux, is to signal that “the cellular war is over, the danger has passed and cells can return to ‘peacetime’ jobs like normal neurodevelopment, growth, and healing.”
The aim of the trial was to find out whether the cell danger response theory might explain the development of ASD and to assess the safety of suramin, which is not approved for the treatment of ASD. An earlier trial that tested the drug on mice had found that a single dose “temporarily reversed” symptoms of ASD.
The boys were randomly assigned to receive either a single intravenous transfusion of suramin, or a placebo.
The results showed that all five boys who received the active drug showed measurable improvements in ASD symptoms not seen in the placebo group. The improvements were specifically in speech and language, social communication and play, coping skills, calm and focus, and repetitive behaviour.
The researchers used a battery of standardised tests and interviews to measure the improvements. When these involved parent observations, the team only counted a change as an improvement if it persisted for at least a week. This was to rule out any fluctuations in day-to-day behaviour that may have occurred anyway.
Prof Naviaux says that there were four non-verbal children in the trial: two aged 6 and two aged 14, with one of each age having been assigned to the drug group and the placebo group.
“The 6-year-old and the 14-year-old who received suramin said the first sentences of their lives about one week after the single suramin infusion,” he notes. “This did not happen in any of the children given the placebo.”
