This is because each species of animal reacts in a different way to drugs and chemicals. Each species of animal differs in terms of metabolic rate, physiology, immunology, anatomy, genetics, etc. This is known as species difference. All you have to do is select the appropriate species. Among many others with financial vested interests in vivisection there are animal breeders and suppliers, manufacturers of accessories such as restraining devices and surgical instruments, and grant-hungry universities and researchers.
Many researchers actually base their entire careers on vivisection.