The development of novel therapies, such as the somatic cell therapy or the transplantation of tissues generated from stem cells, requires new preclinical strategies as to the safety of these products. Conventional efficacy and safety studies, e.g. for biopharmaceuticals, are not suitable for these cell-based products (cell-based advanced therapy medicinal products; ATMPs). The application of cell-based ATMPs thus requires clearly defined safety studies under GLP (Good Laboratory Practice) conditions that are in line with regulatory requirements of the national and european authorities. Here, the interest mainly focusses on biodistribution, i.e. distribution of the applied cell-based ATMPs within the tissue, as well as tumorigenicity, i.e. the propensity of the applied cells to undergo transformation, and thus have to be appropriately addressed in preclinical studies. The aim of this project is the realization of preclinical efficacy and safety studies for a cartilage therapy on the basis of mesenchymal stem cells (MSC). For this ATMP, MSC are isolated in an out-patient bone marrow aspiration and further treated for the production of a patient-specific cartilage therapy (MSC-based Matrix-associated Autologous Chondrocyte Transplantation; MSC-MACT). In the preclinical GLP studies, both the biodistribution and tumorigenic potential of the human MSC-MACT are tested in immunodeficient mice. Due to the immunodeficiency of the animals, the implanted human cells are tolerated without graft rejection, and the migration and/or transformation of the human cells can be analyzed. For an optimal function of the ATMPs, the MSC should remain at the site of implantation and not migrate into the surrounding tissue. Thus, the experimental "biodistribution" part clarifies whether cells migrate from the site of implantation and where they settle in the case of migration. This simultaneously identifies potential sites of tumorigenesis that can arise from implanted cells. In the subsequent experimental part, tumorigenicity of the MSC from the implanted ATMP is tested. The non-clinical safety studies for MSC-MACT are an important regulatory building block on the way to a clinical application, which may significantly reduce the risks of a therapy with MSC-MACT for patients with cartilage defects.