Animal toxicology testing is an important stage of the drug development process, allowing adverse reactions and overdose mechanisms to be identified before commencing human trials. This allows for predictions to be made with the safety of the drug during human trials, and allows plans to be made for if overdoses do occur. It can be challenging to identify animals that have receptors for the drug. Advances in gene editing can be used to modify existing receptors, through modifying transgenic mice or other organisms.
However, some people have objections to the use of animals in drug testing. Receptor occupancy studies can be used to identify the ligand binding affinity, ensuring that the drug does not bind too tightly.
To study the effect of a drug on a complete living system however, it is necessary to study the drug in an animal model. This is a regulatory requirement and is unlikely to change in the future.