Abstract: More than 200 years after Parkinson’s disease was first described by the English surgeon whose name would eventually be given to the condition, available treatments remain purely symptomatic, leaving a critical unmet clinical need for a diseasemodifying therapy. One such approach is cellderived brain repair – the transplantation of healthy dopaminergic neurons into the brain to replace those lost from the nigrostriatal pathway throughout the disease. Proof-of-concept for the efficacy of brain repair has amassed from a multitude of both preclinical and clinical trials over several decades. However, this wealth of data is based on the use of human fetuses (after elective termination of pregnancy) as the source of healthy dopaminergic neurons, and this has proven too fraught with ethical and logistical issues to translate into a therapy for patients. While these studies were ongoing, researchers also isolated human embryonic stem cells (ESCs), generated human induced pluripotent stem cells (iPSCs), and developed and refined protocols to convert these to dopaminergic neurons that could be used in place of the human fetal cells. The stem cell era of brain repair is now firmly underway (reviewed in Barker and Bjorklund, 2023) with several clinical trials currently ongoing (including the Kyoto iPSC Trial: UMIN000033564; the BlueRock ECS Trial: NCT04802733; the STEM-PD ESC Trial: NCT05635409; and the S.Biomedics Co. ESC Trial: NCT05887466).