Drug development for children presents unique challenges and is highly regulated. Novel approaches, such as the use of extrapolation to address for example the need to avoid unethical studies, whilst supporting robust evidence generation have been developed in support of benefit/risk considerations by regulatory authorities. This is only one step in the decision-making process towards access, which in Europe also includes health technology assessment (HTA) bodies. Discussions related to evidentiary requirements in small populations through the use of evidence transfer has been identified as a priority action by EMA/ EUnetHTA 21. We describe the outcome of this work; reflect on the discussions taken place how to leverage prior knowledge through identifying and addressing uncertainties during life cycle management to support regulatory and HTA decision making. Through examples, we discussed the spectrum of use to support evidence generation, and developed regulatory and HTA reflections on general design considerations important for robust evidence generation; reflective of the joint ambition. Early interactions with all respective stakeholders, particularly between regulators and HTA bodies are key to optimise data generation and utility in children. In Europe, the HTA regulation will offer opportunities for collaborations, which are important for all development efforts. We collaboratively explored the unique specific challenges relating to paediatric drug development, ethically and in its ability to leverage prior knowledge, as exemplified using extrapolation. Learnings from these offers opportunities to further develop methodology how to leverage uncertainties across a product’s life cycle for small populations generally.