Here is a medical study that can be found in the US National Library of Medicine. (search for ‘PMC4188566′)
Summary: Oral DMSA was used for treating thousands of severely lead poisoned children 5 years of age and younger.
Conclusion: DMSA was effective for treating lead poisoning in of thousands of children in this study.
Oral DMSA was a pharmacodynamically effective chelating agent for the treatment of severe childhood lead poisoning …US National Institutes of Health
You can read this conclusion yourself in the scientific paper below. This conclusion is at the top of the paper.
Look in the blue area for the word ‘Conclusions’