Not sure exactly where they got that from, but here's the registry for the US phase 1 trial (https://www.clinicaltrials.gov/ct2/show/study/NCT04756531)

The last condition of the exclusion criteria is "Use of tobacco or nicotine containing products in excess of the equivalents of 5 cigarettes per day or 2 chews of tobacco per day", which seems somewhat related.

I wonder what the metabolic argument is (if any). Maybe it's something else. Really interesting regardless -- anyone know why there's this restriction?

COVID has a serious effect on one's lungs. Smoking does as well. I'm sure they would prefer to see how the medicine works on healthy subjects as a baseline. If it doesn't have the same effect on smokers as the baseline, then you can infer from that. If you just get tainted samples from "diseased" lungs of smokers in the original testing, then that could skew the results. That would be my SWAG.

True, true. Maybe the chewing tobacco is meant to be a proxy for smoking earlier in life.

> "clean-living adults"

This is not an ordinary term-of-art in pharmaceutical research.

Might be reporter's paraphrase of "healthy adults" i.e. not obese, hypertensive, no regular/heavy alcohol or drug use, no chronic conditions, etc.

Maybe something to do with household cleanliness? I know when I go into dirty buildings my allergies mess me up.