Researchers work hard every hour of every day, somewhere to design and test new treatments for Parkinson’s disease. Their success rate numbers vary, and more of these clinical trials are unsuccessful than they are a success. According to an article on the NIH website, a large review of Parkinson’s drug development from 1999–2019 found that only about 42.4% of Phase 2 Parkinson’s drugs successfully advanced to Phase 3 trials, with only about 15%, or 1 in 7 of Parkinson’s drug candidates getting FDA approval. A separate 2024 review published in Nature Communications found that drug development across medicine generally has clinical success rates of less than 10%.
For patients with Parkinson’s disease, clinical trials represent hope, but hope is never a guarantee. Unfortunately, many patients in multiple kinds of studies have died as a result of a trial that wasn’t able to perform to what the researchers were hoping to see from the results of many of these trials. One notable and well-known case is TogetherForSharon’s Dr. George Ackerman and the story of his mother, Sharon, who participated in a clinical trial in Florida in hopes of finding a treatment to help ease the symptoms of her Parkinson’s. The trial wasn’t successful, and Sharon passed away some time later, not as a result of the trial, but as a result of the disease that brought her there in the first place.
What goes unnoticed by most people who have a casual eye for this kind of story is the costs of what it takes to run these clinical trials. The costs alone run in the millions of dollars and are represented by years of research and work by everyone involved. For a clinical trial to fail, it sees the investment involved lost, not just in dollars, but in time, effort, and the hopes of every patient who signed up. For both those clinical trials that are successful and those that fail, recouping that investment is just as hard as developing the drug to begin with; even when a trial succeeds, the financial burden doesn’t disappear. This makes funding by the government, by private organizations, and by individuals even more important. Millions are raised every year to help offset these costs, but funding by the U.S. government has dropped, with organizations like the Parkinson’s Foundation, the Michael J. Fox Foundation, and the American Parkinson’s Disease Association having to pick up where the government leaves off. All of this makes funding critical to get these trials paid for. The NIH invests roughly $330 million annually into Parkinson’s research, while spending for direct medical expenses and disability-related costs for patients exceeds $25 billion per year in federal Medicare and Medicaid spending alone, according to the Michael J Fox Foundation.
According to the website Grand View Research, the global clinical trials industry was valued at about $89 billion in 2025 and is projected to grow to nearly $94 billion in 2026. By 2033, the industry spending will reach more than $158 billion. Research in North America accounted for just over half of the world’s clinical trial activity in 2025. Experts say growth is being driven by the rising rates of chronic and rare diseases, advances in personalized medicine, the expansion of virtual clinical trials, and increased research investment from pharmaceutical and biotechnology companies.
One of these recent clinical trials was the failure of the Phase 2 trial of BIIB122, a drug targeting the LRRK2 gene being developed by Biogen and Denali Therapeutics. The LRRK2 (Leucine-Rich Repeat Kinase 2) gene produces a protein that acts like a cellular control center, helping your brain cells recycle cellular waste, control how the brain’s immune system reacts to damaged cells, protein clumps such as alpha-synuclein, infections, toxins, and other forms of cellular stress, and manage the transport of critical materials needed for normal function. Researchers believe that when LRRK2 becomes overactive, these processes can become disrupted, leading to increased inflammation, impaired cellular cleanup, and damage to the neurons affected by Parkinson’s disease. BIIB122 is a 225mg once-a-day tablet designed to block LRRK2, a gene researchers believe plays a role in the disease itself.
The LUMA Phase 2b double-blind, placebo-controlled study enrolled 648 people with early-stage Parkinson’s disease, both carriers of the LRRK2 gene and some without, who took either the medication or a placebo for 48 weeks, and up to 144 weeks for those who remained in the study. It failed to meet its goals of slowing down the disease. According to Biogen and Denali Therapeutics, the medication is designed to slow the progression of Parkinson’s, not just treat the symptoms. The result was disappointing because many researchers viewed LRRK2 as one of the most promising disease-modifying targets in Parkinson’s research. While the drug hit its target, it failed to slow the progression of Parkinson’s symptoms in the Phase 2b LUMA trial.
According to the press release put out by Biogen and Denali Therapeutics, “While these are not the results we hoped for, these data provide important information to the Parkinson’s community and will be presented at an upcoming scientific conference,” said Diana Gallagher, MD, Senior Vice President and Head of Neurodegeneration Clinical Development at Biogen: “We are profoundly grateful to the patients, families, and investigators who participated in this study and contributed to our understanding of Parkinson’s disease.” Peter Chin, M.D., Chief Medical Officer and Head of Development of Denali Therapeutics: “While we are disappointed with these results, we believe the LUMA study was a robust test of LRRK2 inhibition using BIIB122 in idiopathic Parkinson’s disease, and there is more to be learned about LRRK2 as a potential therapeutic target.” While the Phase 2 trial didn’t meet its intended goals, Biogen researchers are now analyzing the data to see if specific patient subgroups could still benefit from BIIB122.
While there are more failures than successes, one of the most recent successful trials has been with the drug Tavapadon from AbbVie, which is a once-a-day oral dopamine agonist that is in the final stages of clinical trials before moving on to the FDA for approval. The drug targets D1 and D5 dopamine receptors by boosting dopamine signals in the brain, helping make up for the loss of dopamine-producing cells as the disease progresses. According to the TEMPO-4 study listed on ClinicalTrials.gov, researchers examined the long-term safety and effectiveness of Tavapadon in people living with Parkinson’s disease.
The nearly 1,000 participants who had completed earlier studies in earlier phases of the trial continued taking the drug so researchers could watch for any long-term side effects and see if the benefits lasted. While the study was mainly focused on safety rather than comparing the drug to a placebo, the overall TEMPO clinical trial program found that Tavapadon helped improve movement symptoms and reduced the amount of time patients experienced worsening Parkinson’s symptoms throughout the day. The information collected in TEMPO-4 helped researchers better understand how the drug performs over time and supported its continued development as a potential new treatment for Parkinson’s disease.
There is no word from AbbVie at this time on when Tavapadon will go to the FDA for approval. Even after successful Phase 3 trials, the drug will undergo a detailed FDA review process that typically takes six to ten months before a final approval decision is made.
The hopes for what this could mean for Parkinson’s patients are hard to overstate. Waking up in the morning and taking a once-a-day pill that actually helps manage your symptoms of Parkinson’s disease could change daily life in ways that current treatments simply can’t.
Sharon Ackerman’s story is not unique. There are thousands of patients like her, people who stepped forward when a trial needed volunteers, who gave their time and their health to a process that didn’t save them. Their contribution to what researchers know today keeps researchers going. Every success, no matter how small, drives the train further and makes every step taken more worth while.
Image by Chris Denny/ChatGPT
