Benfotiamine is a dietary supplement that is a derivative of thiamine (AKA vitamin B1). From my CFS research, it may have benefits for autism.
- Thiamine and benfotiamine protect neuroblastoma cells against paraquat and β-amyloid toxicity by a coenzyme-independent mechanism. 
- High levels of Alzheimer beta-amyloid precursor protein (APP) in children with severely autistic behavior and aggression. 
- Benfotiamine prevents increased β-amyloid production in HEK cells induced by high glucose. 
- Powerful beneficial effects of benfotiamine on cognitive impairment and beta-amyloid deposition in amyloid precursor protein/presenilin-1 transgenic mice. 
- Benfotiamine attenuates inflammatory response in LPS stimulated BV-2 microglia. 
- Anti-inflammatory effects of benfotiamine are mediated through the regulation of the arachidonic acid pathway in macrophages. 
- Quantitation of plasma thiamine, related metabolites and plasma protein oxidative damage markers in children with autism spectrum disorder and healthy controls.  “Thiamine pyrophosphate (TPP) was decreased 24% in autistic children compared to healthy controls:”
- “we find differences in thiamine homeostasis in ASD patients, which can be corrected by supplementation” 
- “Thiamine tetrahydrofurfuryl disulfide [a different form] appears to have a beneficial clinical effect on some autistic children, since 8 of the 10 children improved clinically.” 
After reviewing with your physician, you may wish to consider supplementing, especially if there is aggression or more severe behaviors. See my ME/CFS post for dosages used.
The Beta-Amyloid aspect is interesting. I am a high function ASD who have had several rounds of ME/CFS (all triggered by stress, typically interpersonal). In one of these rounds, I had a SPECT scan. The radiologist read it as early Alzheimer’s. It is probable that he saw the build up of a pattern associated with beta-Amyloids. With recovery, the pattern disappeared.