Drug design frequently but not necessarily depends on computer modelling techniques ,this type of modelling is sometimes referred to as computer-aided drug design and in most of the case, drug design includes the design of molecules that are complementary in shape and charge to the bio molecular target with which they interact and therefore will bind to it. Although design techniques for prediction of binding affinity are reasonably successful, there are several other properties, such as bioavailability, metabolic halflife, side effects, etc., that first must be optimized before a ligand can become a safe and efficacious drug In addition to small molecules, biopharmaceuticals including peptides and especially therapeutic antibodies are an increasingly important class of drugs and computational methods for improving the affinity, selectivity, and stability of these protein-based therapeutics have also been developed.