This CRC initiative aims to develop peptide-based therapeutics. Z02 provides a multi-step approach for preclinical assessment of toxicity, bioavailability and biodistribution of peptides as well as novel transporter and labeling systems. As successfully established in the first funding period, it will perform initial in vivo toxicity assessment in zebrafish embryos, allowing for high throughput and identification of sublethal organ-specific toxicity. Biodistribution and stability of selected peptides will be analyzed by non-invasive positron emission tomography (PET) and magnetic resonance imaging (MRI) first in ovo and in basic mouse models. Finally, the most promising compounds will be analyzed for specificity and efficacy in disease-specific mouse models.