A new investigational treatment for Parkinson’s disease is showing early promise in its first human clinical trial, thanks in part to foundational work at the University of Wisconsin–Madison and the Wisconsin National Primate Research Center (WNPRC).
Parkinson’s disease gradually kills dopaminergic neurons that produce the chemical messenger dopamine, disrupting communication between brain regions that control movement. Standard treatments such as L‑DOPA can boost dopamine levels and reduce symptoms, but their effectiveness often wanes over time, and they do not replace the lost cells.
In the Phase 1/2a ASPIRO trial, run by biotechnology company Aspen Neuroscience, patients receive transplants of dopamine-producing neurons grown from their own cells, which are then delivered to affected areas of the brain.
Aspen Neuroscience recently announced that it will enroll a third patient cohort after reporting that participants are safely tolerating the treatment and showing encouraging improvements in Parkinson’s symptoms. According to the company, early data from the first four patients indicate that intracranial delivery of these cells is safe and well tolerated, with both patient-reported and clinician-reported measures showing positive results. Unlike typical organ transplants, because the neurons are derived from each patient’s own induced pluripotent stem cells—a fully autologous approach—no long-term immunosuppressive drugs are required.
Although UW–Madison is not a clinical site for ASPIRO, scientists at the university and WNPRC played a key role in getting the therapy ready for first-in-human testing. In 2024, a team led by UW–Madison medical physics professor and WNPRC investigator Marina Emborg, M.D., Ph.D., successfully transplanted human progenitor cells into the brains of macaque monkeys. These progenitors were programmed to become dopamine-producing neurons, the same type of cells lost in Parkinson’s disease. Aspen supplied the human cell lines and specialized delivery equipment, while the Emborg lab optimized the surgical approach in nonhuman primates.
Aspen scientists and WNPRC researchers refined a delivery method that uses MRI-guided neurosurgical techniques to place very small volumes of cells—just a few microliters at a time—into the areas of the brain where they are needed. The 2024 study in macaques focused on demonstrating that Aspen’s human cells could be delivered safely and effectively with fewer surgical passes, reducing risk while still reaching the target area of the brain. Results from this work, published in the Journal of Neurosurgery, supported Aspen’s successful application to begin the ASPIRO trial.
The ASPIO trial research builds on earlier successes at UW–Madison, where Dr. Emborg and Wisconsin School of Medicine and Public Health scientist Su‑Chun Zhang, M.D., Ph.D., previously reversed Parkinson’s-like symptoms in nonhuman primates using an autologous cell graft approach. Together, these studies helped validate the concept that individualized cell replacement can restore function in a Parkinson’s model and informed critical details such as cell preparation, quality control and surgical logistics.
For Dr. Emborg and her colleagues at the Wisconsin National Primate Research Center, seeing the first human patients receive the therapy has been a powerful milestone. Years of iterative work in nonhuman primates—testing cell lines, refining delivery tools and optimizing postoperative care—directly shaped how the ASPIRO trial is conducted today. The early human results offer hope that this carefully developed approach could one day provide people with Parkinson’s disease a new option that goes beyond symptom management to address the underlying cell loss.
As the ASPIRO trial progresses, the partnership between Aspen Neuroscience, UW–Madison and WNPRC underscores how translational nonhuman primate research can help bridge the gap between laboratory discoveries and first-in-human therapies, particularly for complex neurological diseases.
