In science one is maximally conservative with positive results. Negative results can be accepted rather quickly but positive results need to be maximally investigated. False positives are unacceptable, false negatives are often less damaging.
I'd question how scenario #1 made it through animal trials preceding experiments in humans.
(1) would absolutely not be continued, obviously.
(2) would be continued to completion.
In science one is maximally conservative with positive results. Negative results can be accepted rather quickly but positive results need to be maximally investigated. False positives are unacceptable, false negatives are often less damaging.
I'd question how scenario #1 made it through animal trials preceding experiments in humans.