evidence: In the 1990s, NIA researcher Dr. Josephine Egan and colleagues teamed with Amylin Pharmaceuticals to begin preclinical testing of exendin-4. By 1999, they reported that a single daily injection of exendin-4 given to diabetic mice was sufficient to normalize blood glucose concentration, with benefits evident by the end of the first week of treatment. Dr. Egan and her collaborators later found that exendin-4 increased insulin production and protected the insulin-producing cells against damage in humans, and that its effects lasted for hours. After further clinical testing, it was deemed to be safe and effective, and it received FDA approval in 2005.