One of the problems was that DMSA is not a very good chelator of arsenic. That is best chelated with ALA or ALA in conjunction with DMPS.
Beyond that, DMSA is possibly the best broad-spectrum chelator. It is effective on lead and cadmium, although chelation of the latter can be hazardous, as DMSA is processed through the kidneys and can drop cadmium in the kidney tissue during chelation. This can lead to stones and renal damage. Cutler suggests keeping the urine alkaline to avoid this, but urine that is alkaline can cause calcium phosphate stones as well as kidney infections.