Manufacturers of medicinal products are legally obliged to obtain regulatory approval for their product before marketing of that product may begin. However, where different salts, esters, ethers, isomers, complexes or derivatives of a brand (on-patent) drug are made by a generic company, and these differ significantly in properties with regard to safety and/or efficacy when compared to the patented drug, additional clinical data demonstrating the safety and/or efficacy of that generic drug must be submitted by the generic company to the marketing authority.