The thing is multiple sources* show that animal testing isn’t even reliable to begin with. Much of it is totally unnecessary, especially since the results you’d get from testing on animals does not serve as a good representation of how a medicine would affect humans.

*Examples:

1. “We have moved away from studying human disease in humans … We all drank the Kool-Aid on that one, me included … The problem is that it hasn’t worked, and it’s time we stopped dancing around the problem … We need to refocus and adapt new methodologies for use in humans to understand disease biology in humans,”
2. Across the board, human genes and their corresponding mouse genes only responded in the same way 50% of the time— a statistic that could easily be explained by random chance.
3. In 2004, the FDA estimated that 92 percent of drugs that pass preclinical tests, including “pivotal” animal tests, fail to proceed to the market. More recent analysis suggests that, despite efforts to improve the predictability of animal testing, the failure rate has actually increased and is now closer to 96 percent. The main causes of failure are lack of effectiveness and safety problems that were not predicted by animal tests.

Some alternatives have been thought about, and these would include things like extracting cells from consenting humans for lab-grown tissue models and running trials on consenting humans in cases we can ensure no risk of lethality or harm.