ALA, lipoic acid is natural. We get some from various foods such as broccoli.
DMSA is an FDA approved medication for lead even in kids. It has been around for roughly 50 yrs.
Cutler's protocol has only been around for 15 yrs. He provided a tweak to older use of DMSA by requiring more strict dose timing. He is probably the first to advocate the use of DMSA or DMPS along with ALA.
You can get a feel for his concepts from the following links. (he has a PhD in chemistry so they will be somewhat technical )