[derefr]

Run one trial to find correlations with specific groups, then run another trial under the hypothesis that it works for that group.

[nradov]

Well sure but that costs a fortune. Drug development is already extremely expensive.

[ncmncm]

That is a good idea, but it generates accusations of special pleading. Medical science is plagued with many kinds of fetish, and medical doctors are not generally obliged to actually understand science.