This is absolutely in the moral gray. The greater good, lesser of two evils, however you want to describe it whether it's right or wrong will get down to your personal beliefs.

I had a family member involved in a cancer research that used mice and although he admitted it was sad, he did call them heroes. Understandably, I don't think that satisfies anyone strongly aligned with animal rights. In many other sciences we've been able to use simulation as a first step, but that is still out of our reach for biological systems.