Only 5% of therapies tested on animals are approved for human use

Few studentsPLOS go into medical research dreaming of one day giving a mouse a tumour or heart disease to a rabbit. But animal experimentation of this kind has become fundamental to modern medicine. For regulatory bodies around the world, treatments that might save human lives must be proven safe and effective in animals with similar conditions before they can be put on the market.So how is this ethical bargain holding up? Not well enough, suggests a paper in by Benjamin Ineichen of the University of Zurich and his colleagues. Out of 367 biomedical therapies tested on animals over thousands of studies, a surprisingly low proportion—only 5%—eventually obtained the approval of the Food and Drug Administration, America’s regulatory agency for drugs, to be used in humans.