Letter to the Editor: “Clinical Trial of the Safety and Efficacy of Intravenous Umbilical Cord Blood Infusion for Treatment of Children with Autism Spectrum Disorder”

Dawson et al have drawn attention to the outcomes of umbilical cord blood (UCB) administration for the treatment of 180 children with autism spectrum disorder (ASD).¹ Because there is a substantial interest in stem cell therapy as a potential candidate or therapeutic approach for ASD, these outcomes are noteworthy. The authors provide findings from a large sample size, randomized process with a control group, and processing paradigms, although the results did not support the efficacy of UCB administration. However, several points may influence interpretation of the findings.

First, we note that the authors administrated a relatively low dose of UCB-derived mononuclear cells and CD34+ cells compared with previous studies.^2,3 Other investigators have suggested that the minimum cell dose at which the CD34+ could show influence in nonmalignant diseases is 1.7 × 10⁵ CD34+ cells per kilogram of patient’s body weight (PBW).⁴ The CD34+ cells in the current studyare 0.3 × 10⁵ cells/kg PBW and 0.7 × 10⁵ cells/kg PBW for autologous UCB and allogeneic UCB, respectively. In addition, intravenous infusion of cells limits delivery, as cells might be trapped in organs such as the lung, heart, liver, or kidney, which in turn reduces therapeutic effects on the brain.⁵ Hence, the dosage of UCB may be a reason for the lack of evidence of efficacy. Second, the authors reported the results of a 6-month follow-up; this is a relatively short period to observe the progressive improvement of children with ASD. Previous studies demonstrated improvements observed after 12-month and 18-month follow-up, especially on the Childhood Autism Rating Scale score³ and the Clinical Global Impression Scale.^6,7

In summary, the authors’ conclusion may be limited within the trial’s scope and suggest no significant difference between 2 groups when CD34+ cells were administrated intravenously at the lower dose with a 6-month follow-up. Future research using UCB (high CD34+ cells and multiple doses) via other administration routes should be considered.