 As cancer cells are generally growing and multiplying much more rapidly than normal healthy cells, this creates an environment that is less oxygen rich due to the raised metabolic rate.When this is paired with the tendency of cancerous cells to contain higher levels of glutathione and a lower pH, a chemically reducing environment is created.This allows for ruthenium complexes to be administered as much less active, non-toxic Ru(III) compounds (as a prodrug), which can be activated solely at the site of the cancerous cells.