Taking prescription drugs during pregnancy can be harmful to the unborn child. Therefore, identifying the embryotoxic potential of a new drug candidate is an essential part of any preclinical study. These studies are currently conducted in animals according to OECD guidelines. In Europe, 11 Million animals are tested annually. About 50 percent of these tests are performed to explore the bone harming and thus the embryotoxic potential of such drug candidates. Dr. Nicole zur Nieden, leader of the stem cell group at the Fraunhofer Institute, is developing a method to identify the bone harming potential in vitro. This shall be enabled by simulating and monitoring the multi-phase differentiation process of pluripotent stem cells in a controlled bioreactor system. By adding compounds with known in vivo osteotoxic potential, adverse effects on the differentiation will be identified. Non human embryonic primate stem cells will be compared to human progenitor cells to study varying molecular reactions compared to the established test organisms (mice). DASGIP, leading manufacturer of parallel bioreactor systems, will contribute its bioreactor system to the project. Through further improvements Dr. Matthias Arnold, CSO DASGIP, and the scientists at the Fraunhofer IZI plan to establish and automate a multi-step cultivation process covering the different phases of differentiating stem cells in drug testing. The German government subsidizes the research project, acting on behalf of international organizations such as OECD and the EU. Since 1986 the EU commission has stressed its interest in new methods to minimize, replace or optimize animal testing. Recently, the demand to accelerate these processes has been increasing due to the EU Cosmetics and Chemicals Legislation and the desire to avoid complications associated with drug development. To date, only the embryonic stem cell test (EST) could prove as reliable ex vivo alternative to animal testing, which builds the basis for the planned improvements. The EU commission will publish its new ideas on how to reduce the need for animal testing and how to promote alternative methods sometime in April. Not only politicians, but also industry representatives strongly appreciate the development of alternative methods as it can make drug development and approval faster and more cost-effective: In contrast to existing processes the stem cell approach promoted by Fraunhofer IZI is characterized by a high predictability for human effects, by cost-efficiency and by short testing periods. Therefore, Thomas Drescher, President of DASGIP, looks forward to providing the industry with a bioreactor system, which could help replacing up to 50 percent of the animal tests required in bone toxicity test for drugs, chemicals, plant protecting agents and cosmetics. Further project partners are the ZEBET - Centre for Documentation and Evaluation of Alternatives to Animal Experiments - at the Federal Institute for Risk Assessment (http://www.bfr.bund.de/cd/1591) and the contract research organization RCC Ltd. (http://www.rccltd.ch).