ABSTRACT
For a large part of human history, drugs derived from plants, animals, and minerals were discovered through experimentation and observation in both humans and animals. Scientists such as Edward Jenner were even able to test some of their ideas in humans. Animal models have been pivotal in determining the function of the many compounds discovered or synthesized de novo by chemists for over eight decades. In many cases, such studies led to the discovery and development of compounds that are now used clinically. The drug discovery process is long and challenging. Only 1 out of every 10,000 candidate compounds make it through to marketing approval by regulatory bodies. The pharmaceutical industry estimates that it can cost between 800 million and 1 billion dollars to develop an approved drug. Animal models have been used since the 1950s to study tumors in situ, whether examining basic biological concepts of cancer development or therapeutic response.
