They'll probably only have marginal success with trying to stop chemicals used to mask doping substances. There are numerous products out that can provide negative test results for marijuana users. About the time labs figure out what is masking the drug use a new method is aleady being used and the drug users can stay one step ahead.

But on the other hand, there's probably a much bigger market for masking marijuana use than there is for athletic doping substances so there might not be enough r&d money to be successful.