Placebo- and active-controlled trials are considered the "gold standard" of well-controlled trials. However, for rare pediatric diseases, this imposes a large burden on families who are desperate for new treatments that could impact the unmet needs of the disease and do not want to enroll their children in a trial in which they may not gain access to the treatment with the potential to provide greater benefit (see for example the recent Voice of the Patient report in MPS II, https://projectalive.org/wp-content/uploads/2021/07/VOP_Hunter_Syndrome.pdf). In some cases, CDER has access to already-available data from multiple placebo- and active-controlled trials in different rare diseases. To better inform statistical assumptions and potentially reduce the number of control patients or replace the control arm entirely in rare pediatric disease pivotal trials for novel treatments, the pediatric database available to CDER could be used to create a comprehensive dataset of aggregate control arm key safety and efficacy results from trials within the same rare disease, alleviating the burden on pediatric patients and their families and enabling more efficiently designed trials. To identify the most relevant outcomes to include in such a control arm dataset, FDA could develop a collaborative process with key stakeholders, including drug developers, patient advocates, and key opinion leaders, to obtain input on which outcome measures to include for a given disease.