Positive Topline Results for Novel Autism Drug

Megan Brooks

February 09, 2021

An intravenous formulation of suramin (PAX-101, PaxMedica) reduced several core symptoms of autism spectrum disorder (ASD) in a phase 2 study, according to the company, which released topline results.

"There is an enormous unmet need in treating the symptoms of moderate to severe ASD, which include both social and communication challenges as well as restrictive, repetitive behaviors," Alice Mao, MD, medical director of Memorial Park Psychiatry Adult, Adolescent and Child Psychiatry, in Houston, Texas, said in a company news release.

"PAX-101 has the potential to demonstrate meaningful clinical improvements in this debilitating condition, which could positively impact the lives of many families," said Mao.

Suramin has long been used to treat African sleeping sickness and river blindness. It has been investigated as a treatment for other diseases, including cancer, but it has not been approved for any therapeutic indication in the United States.

The mechanism of IV suramin (PAX-101) in ASD is not fully understood. It has been postulated to act through purinergic receptor blockade to reverse the effects of mitochondrial dysfunction and to reduce neuroinflammation in these patients, the company said.

The phase 2 study enrolled 52 children (mean age, 8.3 years) with moderate to severe ASD in six sites in South Africa. Participants were randomly allocated to receive either PAX-101 (10 or 20 mg/kg) or placebo via IV infusion at baseline, week 4, and week 8. There was a 6-week follow-up period after the last dose of study medication.

Forty-three of the 52 children completed the study; five were withdrawn because of COVID-19, one because of an adverse event, and two for other reasons.

Compared to placebo, treatment with PAX-101 led to "marked and sustained" improvement in several efficacy assessment measures, including the Aberrant Behavior Checklist composite score of core symptoms (ABC Core), the Clinical Global Impression of Improvement scale, adapted for autism (CGI-I), and the Autism Treatment Evaluation Checklist, the company said.

At week 14, there was a mean 48% improvement from baseline in the ABC Core score for patients who received active treatment, vs 31% for those who received placebo. Twice as many actively treated patients demonstrated a 70% or greater improvement in comparison with patients who received placebo, the company said.

At week 14, patients treated with PAX-101 also demonstrated a mean improvement from baseline in the CGI-I overall symptom severity score of 0.9 points, vs 0.4 with placebo, which represents a clinically meaningful change from baseline.

Both doses of PAX-101 were well tolerated. The most common treatment-emergent adverse events were rash, upper respiratory infection, and vomiting. Most events were mild to moderate in severity and resolved with no intervention.

There was one serious adverse event in one patient who had multiple concomitant conditions and who received PAX-101. That event resolved without sequelae following acute treatment.

"This is an exciting step forward for the autism community. The results from this clinical trial clearly show promise for advancing this novel treatment into the next phase of development," Mao said in the news release.

PaxMedica plans to report full results of the trial at an upcoming medical conference and to submit the results for publication in a peer-reviewed scientific journal.

In addition to PAX-101, which is given by IV infusion, PaxMedica is developing PAX-102, a proprietary intranasal formulation of suramin for less severe forms of ASD and for other neurodevelopmental disorders.

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