I would like to know what the difference is between the following 2
chemicals, what the regular use is (other than the new trials in
animals with cancer), and what safety data is available on them
(toxicity studies, animals or humans)

3-bromopyruvic acid
3-bromopyruvate

I believe 3-bromopyruvate is the "buffered" or "stabilized" form of
3-bromopyruvic acid.

Nomenclature rules would indicate that 3-bromopyruvate is a salt;
probably the sodium or potassium salt. (Thus making it buffered.)

Here's the MSDS for the acid: https://fscimage.fishersci.com/msds/89939.htm

:-) As2O3