New Potential Therapy for Autism Spectrum Disorder

A pilot study was done on a new medication in a group of adolescents. How does it work, what were the results, and were there any side effects?

Autism spectrum disorder (ASD) affects roughly 1 in 44 eight-year-olds in the United States as of 2018.¹  Its manifestations can vary significantly between individuals; however, it is often characterized by differences in communication, social interactions, and other behaviors.^2,3  Some individuals with ASD may also experience other symptoms, including anxiety, altered sensory processing, and more.²  Another symptom of ASD that some individuals may experience is gastrointestinal (GI) issues.²  Additionally, some recent studies suggest that children with ASD may be more likely to have certain alterations to their gut microbiome or the bacteria in their GI tract.^4,5,7

Management of ASD is multifaceted and varies significantly between individuals as the condition is very complex.  Although behavioral therapy is generally the first-line treatment for ASD, some individuals may find medications to be a helpful addition to managing symptoms. For example, risperidone and aripiprazole are both FDA-approved to treat irritability in children with ASD.⁶ However, these medications may not be helpful for everyone, and some individuals may experience side effects that outweigh the benefits.  

For this reason, some researchers are investigating different pharmaceutical therapies that could hopefully help improve the quality of life in certain people with ASD.  One of these therapies is AB-2004, an oral GI adsorbent, which is thought to bind and sequester certain GI metabolites, including 3-(3-hydroxyphenyl)-3-hydroxypropionate (HPHPA), 3-(4-hydroxyphenyl)propionate (HPPA), 3-hydroxyphenylacetate (HPPA), 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF) and imidazolepropionate (IPA).²  Although more research is needed, some recent evidence suggests that increased levels of these molecules in the GI tract may be associated with ASD symptoms in mice.^2,8,9  

Study outcomes

Based on this, in addition to a stage 1 study demonstrating its safety in mice, the researchers of the following study hypothesized that AB-2004 may help reduce the levels of these metabolites, and this may hypothetically lead to decreased ASD symptoms.²  

Tested for the first time in humans

AB-2004 was tested for the first time in humans, and the findings were published in Nature Medicine.²  The study group consisted of 30 adolescents, one female with 29 males, with both ASD and GI-related symptoms. Participants took gradually increasing doses of AB-2004 for 8 weeks based on body mass, from a maximum of 2.25 grams daily at the start of the study to a maximum of 6 grams daily at the end.²  

Behavioral symptoms assessed

Behavioral symptoms of the participants were assessed at baseline and at the end of the study using five behavioral assessments: the Pediatric Anxiety Rating Scale, the Aberrant Behavior Checklist, the Social Responsiveness Scale, the Rebetitive Behavior Scale-Revised, and the Vineland Adaptive Behavior Score.^2,10-14   Gastrointestinal symptoms and metabolite levels were also assessed at both time periods using a variety of well-known assessments.²  

The health of all participants was monitored throughout the study to ensure that no serious adverse effects arose. 24 out of the 30 participants completed the study up until the final check-up, and 15 participants were assessed for any potential behavioral changes.² 

What the study found

The study found, on average, reductions in the number of participants with GI symptoms, as well as reductions in urinary levels of six relevant GI metabolites. 

Additionally, many participants exhibited clinically relevant reductions in anxiety and irritability. 

Finally, no serious adverse effects occurred during the study period; however, possibly related side effects occurred in 46 percent of participants, with the most common ones being mild abdominal pain and nausea.²  

The results of the study warrant further research of AB-2004, as it displayed promising potential in this pilot study. However, there was no external control group in this study, so comparing these results to a placebo or current drug is important. More research is needed to confirm the desired effects of the drug and evaluate its safety in a larger population.  

References

1. Maenner, M.J., Shaw, K.A., Bakian, A.V., et al (2021, December 3). Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years – Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018. Surveillance Summaries 70(11): 1-16. Doi: 10.15585/mmwr.ss7011a1
2. Campbell, A.S., Needham, B.D., Meyer, C.R., et al (2022, February 14). Safety and target engagement of an oral small-molecule sequestrant in adolescents with autism spectrum disorder: an open-label phase 1b/2a trial. Nature Medicine. Doi: 10.1038/s41591-022-01683-9. 
3. National Institute of Neurological Disorders and Stroke (2022, January 19). Autism Spectrum Disorder Fact Sheet. National Institutes of Health. Accessed 2022, March 14, from https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Autism-Spectrum-Disorder-Fact-Sheet
4. Xu, M., Xu, X., Li, J., et al (2019). Association between gut microbiota and Autism Spectrum Disorder: A systematic review and meta-analysis. Front Psychiatry 10(473): doi: 10.3389/fpsyt.2019.00473.
5. Pulikkan, J., Mazumder, A., Grace, T. (2019). Role of the gut microbiome in autism spectrum disorders. Adv Exp Med Biol 1118: 253-269. Doi: 10.1007/978-3-030-05542-4_13.
6. LeClearc, S., Easley, D. (2015, June). Pharmacological therapies for autism spectrum disorder: a review. P.T 40(6): 389-397. Accessed 2022, March 15, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4450669/
7. Ho, L., Tong, V., Syn, N., et al (2020, February). Gut microbiota changes in children with autism spectrum disorder: a systematic review. Gut Pathog 12(6): doi: 10.1186/s13099-020-0346-1. 
8. Bermudez-Martin, P., Becker, J., Caramello, N., et al (2021, July). The microbial metabolite p-Cresol induces autistic-like behaviors in mice by remodelling the gut microbiota. Microbiome 9(1): 157. Doi: 10.1186/s40168-021-01103-z
9. Karbowska, M., Hermanowicz, J.M., Tankiewicz-Kweldo, A., et al (2020, June 11). Neurobehavioral effects of uremic toxin-indoxyl sulfate in the rat model. Sci Rep 10(1): 9483. Doi: 10.1038/s41598-020-66421-y.
10.  (2002). The Pediatric Anxiety Rating Scale (PARS): development and psychometric properties. J. Am. Acad. Child Adolesc. Psychiatry 41: 1061-1069. 
11. Aman, M.G., Singh, N.N., Stewart, A., et al (1985). The aberrant behavior checklist: a behavior rating scale for the assessment of treatment effects. Am. J. Ment. Defic 89: 485-491.
12. Constantino, J.N., Gruber, C.P. (2012). Social Responsiveness Scale, Second Edition. Western Psychological Services. 
13. Lam, K.S.L., Aman, M.G. (2007). The repetitive behavior scale-revised: independent validation in individuals with autism spectrum disorders. J Autism Dev. Disord 37: 855-866.
14. Burger-Caplan, R., Saulnier, C.A., Sparrow, S.S. (2018). Vineland adaptive behavior scales. In: Encyclopedia of Clinical Neuropsychology. 

Photo by Tara Winstead from Pexels

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