Are you saying there are genetic differences between races?
To GP’s point, lack of diversity in clinical trials can result in medicines that vary in efficacy and safety in the broader population. The ability to customize a therapy to an individual would help reduce the impact of this issue.
1000 years ago you probably could have said that indigenous subsaharan Africans and Americans are different subspecies of homo sapiens simply because one group has darker brown skin and lives in Africa, and one has lighter brown skin and lives in the Americas (phenotype difference + range difference is all it takes). But today the "native range" of every ethnic group is essentially global due to airplanes and immigration, so you'd probably say we're all one subspecies. But either way, the label "subspecies" conveys far less information than people sometimes assign it.
There exist even special medicine to account for genetic differences in Black people: https://en.wikipedia.org/wiki/Isosorbide_dinitrate/hydralazi...