Gotta break a few eggs to make an omelette. Sucks for the animals but if it can advance human medical science and saves millions of lives, I’m fine with it.
So called ethical treatment impacts the speed and scope of research that can be done, and in doing so delays or prevents the benefits of conducting that research. That means that people who could be saved by animal tested medicines instead die in the time taken to find an alternative.
If a technology could be used to save people who would have died had the technology not been used, then not using or not developing that technology effectively condemns those people to die.