Monoclonal antibodies (mAbs) can be potent and specific therapeutics with long plasma half-lives and therefore long exposure times, which are now being clinically used to treat chronic disorders. Their recombinant design means some of their behaviours in the clinic can be determined at the design stage. However, their specific nature means a flexible approach often is required for preclinical studies and the use of novel approaches including parallel reagents and specific transgenic mice are being used. The key aspects at this level to consider are the effects on safety pharmacology and long-term immune status in the preclinical species used in order to predict to people the likely result of chronic clinical usage.