It's the first time we've been so close to having a drug that can potentially treat ASD symptoms. And while parents can't yet turn to their doctors to ask for this treatment (more on that later), the results of the trial could be a huge turning point in how we think about autism.
Around 1 in 160 children are estimated to have ASD worldwide, although the severity of symptoms ranges widely. Scientists are still working to develop a precise picture of the genetic and environmental confluence of factors that can cause autism.
Robert Naviaux from the University of California San Diego School of Medicine thinks that autism symptoms could be driven by a metabolic dysfunction, causing a breakdown in the communication between the brain, gut, and the immune system at the cellular level.
He attributes this dysfunction to the 'cell danger response' hypothesis, stating that the normal cellular response to injury or stress can sometimes "get stuck", and cause abnormal behaviour that leads to chronic disease.
"When this happens during early child development, it causes autism and many other chronic childhood disorders," says Naviaux.
This abnormal cell danger response could be maintained through purinergic signalling - the cell communication process that involves molecules like adenosine and ATP.
To test this hypothesis, Naviaux and his team turned to the drug suramin, which is a known 'antipurinergic' - a molecule that can inhibit purinergic signalling.
Suramin has been around since 1916, and is used in the treatment of the parasitic disease African trypanosomiasis (sleeping sickness).
The first promising results came in pre-clinical mouse studies, when the researchers successfully reversed autism-like symptoms with a single dose of the drug. These studies paved the way to the first human trial, and the results are now in.
This pilot study was double-blinded and placebo-controlled, and involved 10 boys with diagnosed ASD aged 5-14 years, each of whom received a single dose of either suramin or a placebo.
All five boys who received the drug showed a steady improvement of symptoms within just seven days, while the placebo group showed no change at all.
The boys were matched into pairs by age, IQ, and autism severity, which means that each participant receiving the drug could be compared to a very similar participant who got a placebo.
Even though there's huge variation between individuals, people on the autism spectrum share a core set of features - difficulties with social interactions and communication, and repetitive, restricted behaviours and interests.
The researchers used standardised assessments to measure these core features before, during, and after the treatment. Additionally, the parents (who did not know whether their child received the drug or not) also reported improvements in behaviour, language, developmental goals, and social interactions.
This included some truly astonishing changes in two of the four non-verbal participants.
"The 6- and 14-year-old who received suramin said their first sentence of their lives about one week after the single suramin infusion," says Naviaux.
"This did not happen in any of the children given placebo."
Unfortunately, these improvements were only temporary - as the drug gradually left their systems over the course of six weeks, the severity of the symptoms returned, which the participating families had been warned about.
But apart from the dramatic improvement of symptoms, what's most important to the researchers is that the positive results further bolster the hypothesis that metabolic dysfunction contributes to autism, and that this dysfunction is treatable.
"After summarising the design and results of the study, we are left with the conclusion that either the results are wrong because of the small size of the study, or they are an important advance," says Naviaux.
"We won't know which until the results can be replicated in larger studies."
To be clear, at this stage, suramin is not a commercially available drug, and in the US, it's not even approved for any therapeutic use.
The researchers can't emphasise enough that people must not experiment with it at home, no matter how promising these first results may seem:
"Suramin is not approved for the treatment of autism. Like many intravenous drugs, when administered improperly by untrained personnel, at the wrong dose and schedule, without careful measurement of drug levels and monitoring for toxicity, suramin can cause harm.
Careful clinical trials will be needed over several years at several sites to learn how to use low-dose suramin safely in autism, and to identify drug-drug interactions and rare side effects that cannot currently be predicted. We strongly caution against the unauthorised use of suramin."
It's also important to stress how small the sample size was, so what's now needed is large-scale trials to potentially confirm these initial findings, and investigate potential risks and side-effects, and whether suramin could even be used in the long term.
"We have plans for five additional studies over the next five years to collect all the data the FDA will need to decide about the approval of suramin for autism," says Naviaux.
He also notes that even if suramin itself doesn't turn out to be the right treatment for ASD symptoms, these preliminary results might spark interest in the development of new antipurinergic drugs.
We can't wait to see where the larger trials take us - hopefully this is just the first of many promising results.
The trial was published in Annals of Clinical and Translational Neurology.