Introduction: Trials to overcome the lack of pharmacokinetic (PK) and pharmacodynamic (PD) data for establishing safe and efficient pharmacotherapy in pediatric patients are missing. Poor recruitment and problems with the conduct of the trials were among the most commonly reported reasons for trial discontinuation. A novel training concept was developed to address both reasons in the LENA project (Labeling Enalapril from Neonates up to Adolescents) that aims to investigate PK/PD data of enalapril administered in a novel drug formulation to children suffering from heart failure.Methods: A multi-step training concept covering simulation training, on-site training, video-based self-learning modules, and dry runs was conducted prior to first-in-child trials. It based on pre-study visits that accentuated the specific clinical environment and needs of all clinical sites. Communication of study-related information to colleagues, parents, and children was trained in role-plays. Video-based debriefing enriched the learning experience. The complex blood sampling and preparation of sensitive parameters of the RAA-system was taught in a stepwise approach starting at the hands-on simulation training using manikins to dry runs in healthy volunteers. The successful conduct of the latter was mandatory to start with pediatric trials. The teams’ preparedness for the study as well as the usefulness of the training were assessed using five-point Likert scales surveys.Results: 23 participants from five European countries were trained. Participant’s abilities to communicate core elements of the studies and to successfully perform PK/PD sampling increased significantly (p=0.0001; p=0.00003). Sampling preparation time of critical PD parameters was reduced by up to 32%. Further optimization potential was observed at 20% of enclosed clinical sites due to noticeable PK/PD values during dry run. The final setting resulted in acceptable concentration levels of all parameters and facilitated maximum reliable data extraction by reducing invalid samples.Conclusions: Training modules substantially improved the participants’ performance. The tailored training was assessed as helpful in trial preparation and lead to good recruitment rates within the project.