More than half of new Parkinson's drug trials now aim to slow or stop the condition

A major ten-year review of Parkinson’s clinical trials has revealed a significant shift in how researchers are tackling the condition. The analysis, which looked at drug trials launched between 2015 and 2024, shows that scientists are increasingly moving away from just managing symptoms and are instead focusing on therapies that could slow, stop, or even reverse the condition. The report was produced by the Cure Parkinson’s research team alongside the Michael J. Fox Foundation and international research advocates. By examining the global database of clinical trials, the team tracked exactly where funding and research efforts have been directed over the last decade, mapping out the journey of 444 distinct drug trials. The decade in numbers The scale of global research over the last ten years highlights a massive international effort. More than 39,000 people with Parkinson's volunteered to take part in these trials worldwide. Together, these studies tested 281 different drug treatments. The reason there are more trials than actual drugs is that several promising treatments were tested in multiple, separate studies to verify their safety and effectiveness. The types of drugs being tested fell into three distinct categories: Novel drugs: Just over half of the trials (52 per cent) looked at completely new chemical treatments built from scratch. Repurposed drugs: A third of the trials (33 per cent) investigated drugs that are already approved and safely used for other medical conditions, exploring whether they could also benefit people with Parkinson's. Reformulations: The remaining trials looked at changing existing Parkinson's medications, usually by creating new delivery methods like skin patches or pumps to make the current treatments work more consistently. Shifting focus from symptoms to a cure When looking at the overall decade, nearly two-thirds of all trials (63 per cent) focused on symptomatic relief, while 37 per cent aimed for what scientists call disease modification. Disease-modifying therapies are designed to alter the course of the condition by protecting brain cells from damage. However, the yearly trends paint a much more encouraging picture for the future. The number of disease-modifying trials grew steadily over the ten-year period. Between 2022 and 2024, these protective treatments actually made up more than half of all newly registered clinical trials. What parts of biology are researchers targeting? To ease symptoms, most trials focused on motor issues, using updated versions of levodopa and dopamine agonists to top up the brain's dwindling chemical messengers. Conversely, the analysis identified a major gap in research for non-motor symptoms. Very few trials were designed to address the highly challenging everyday aspects of the condition, such as sleep disruption, constipation, depression, and anxiety, marking an urgent area for future funding. For the trials aiming to stop Parkinson's from progressing, researchers targeted several different biological pathways: Alpha-synuclein: Nearly 14 per cent of these trials targeted this specific protein, which is known to misfold and clump together in the brains of people with the condition. Cellular health: Other trials focused on reducing inflammation in the brain, improving how cells generate energy through mitochondrial function, or tackling oxidative stress. Genetics and gut health: Researchers also launched trials tailored to specific genetic variants, such as the GBA1 and LRK2 genes, while others explored the role of the gut microbiome. Repurposed standouts: Diabetes drugs known as GLP-1 receptor agonists, cell therapies, and growth factors also featured heavily in the pipeline. The roadblock at the final stage Clinical trials move through three strict phases. Phase 1 checks if a drug is safe in a small group of people. Phase 2 tests if it shows signs of working. Phase 3 is the final, large-scale test required before a drug can be approved for widespread medical use. The data revealed that getting drugs through to this final stage remains a major bottleneck. Out of all 444 trials, 42 per cent were in phase 1, and 46 per cent were in phase 2. Only 12 per cent had made it to phase 3. When looking specifically at the highly anticipated disease-modifying therapies, only nine individual trials managed to reach this final testing stage over the entire decade. While 14 new treatments to manage symptoms successfully won regulatory approval during this ten-year window, there are still no approved drugs available that can alter the underlying progression of the condition. Speeding up the search One major initiative successfully driving these protective drugs forward is the International Linked Clinical Trials programme. Set up in 2012 by Cure Parkinson’s and the Van Andel Institute, this global project brings together a panel of more than 20 leading scientific experts each year to vet existing drugs used in other areas of medicine and fast-track the most promising ones into Parkinson's trials. The impact of this program is highly visible in the current pipeline. Of the 133 clinical trials that were still active and running at the start of 2025, nearly a third (31 per cent) of all the disease-modifying trials were testing drugs originally identified and prioritized by this expert committee. This includes two high-profile drugs currently moving through definitive phase 3 trials: ambroxol, a cough medication being tested for its cellular clearing abilities, and exenatide, a diabetes drug being investigated for its potential to protect brain cells.