Yes - if you prove that it is safer than other options for the indicated population, the FDA will approve it with a label indicating it only for that population.

Indications can be as specific as "indicated for tumors with specific mutations"[1] or indicated "prostate cancer when all other options have failed"[2]

[1]https://en.wikipedia.org/wiki/Pembrolizumab [2]https://www.fda.gov/drugs/informationondrugs/approveddrugs/u...