A potential new treatment for Parkinson's shows early promise

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A potential new treatment for Parkinson's shows early promise | The Excerpt
On a special episode (first released on May 29, 2025) of The Excerpt podcast: Parkinson's is a disease that afflicts an estimated 90,000 Americans every year. Dr. Lorenz Studer and Dr. Viviane Tabar of Memorial Sloan Kettering Cancer Center, joined USA TODAY The Excerpt to share more about a new stem cell-based therapy that creates nerve cells. The treatment is showing early promise.
Hit play on the player below to hear the podcast and follow along with the transcript beneath it. This transcript was automatically generated, and then edited for clarity in its current form. There may be some differences between the audio and the text.
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Karen Weintraub:
Hello, and welcome to The Excerpt. I'm USA TODAY Health Reporter Karen Weintraub. Today is Thursday, May 29th, and this is a special episode of The Excerpt.
You've no doubt heard of the chemical dopamine. It's often referenced as part of the brain's reward system when we do something pleasurable. Dopamine, or a lack thereof, also plays a critical role in the onset of Parkinson's, a disease that afflicts an estimated 90,000 Americans every year.
Treatment for Parkinson's focuses on managing its many symptoms, as there is no cure. But a new stem cell therapy developed at Memorial Sloan Kettering Cancer Center for advanced Parkinson's is showing early promise.
What's behind this incredible discovery and just how hopeful should patients be? Here to talk about this exciting new treatment and its impact on patients are the two physicians who helped make it a reality. Dr. Viviane Tabar and Dr. Lorenz Studer. Drs. Tabar and Studer, thanks so much for joining The Excerpt.
Dr. Tabar, when someone is diagnosed with Parkinson's disease, what exactly is happening to their brain and their body?
Dr. Viviane Tabar:
Well, we think that at the time an individual is diagnosed with Parkinson's disease, they have already experienced degeneration or loss of a large number of their dopamine neurons. We are all born with a limited number of large, beautiful dopamine neurons that live in our brainstem and that project to multiple areas in the brain.
They're involved in a lot of intricate activities, but an important element of their function is to modulate movement. So the individual very commonly will come to clinical attention because of movement difficulties, albeit there are other symptoms, loss of smell, gastrointestinal symptoms, difficulties with sleep, and it's a complex picture.
But it's important to remember that at the time they receive this diagnosis, which today is still vastly made on a clinical basis, on an examination of the individual and listening to their symptoms, they have already lost probably 50% or more of their dopamine neurons and their projections.
A potential new treatment for Parkinson's shows early promise
A new stem cell-based therapy creates cells that make dopamine, a chemical that's critical to the disease.
Karen Weintraub:
And what are some of the everyday challenges your patients face? You mentioned motor control, cognitive issues also I think?
Dr. Viviane Tabar:
For the majority of patients, and keep in mind that Parkinson's is a disease that spans a variety of symptoms and spectrum of progression and intensity, for most patients it starts with manageable symptoms that they control well, could be a tremor, could be some stiffness in their gait. And for the majority, I would say cognitive change comes late, assuming a proper diagnosis of Parkinson's.
So it becomes paradoxically even more problematic because it starts interfering with activities of daily living, your ability to get to and from your job. You're still high-performing, but you are impaired gradually. And you're fully cognitively there often, and so you're very aware of the slow degeneration that's essentially relentless.
Karen Weintraub:
And you mentioned jobs. Are people affected by Parkinson's primarily older, retiree age, or are there other groups at risk as well?
Dr. Viviane Tabar:
We didn't say necessarily retirees. Parkinson's, the sporadic form of it, which is the most common form, I mean by that the form that's not inherited, that happens commonly in the sixties or later. But nowadays, people in their fifties and sixties are considered at their prime still at work.
Karen Weintraub:
And others who are affected, we think of Michael J. Fox who is certainly younger when he started developing symptoms.
Dr. Viviane Tabar:
There are forms of Parkinson's that occur in a younger individual at a younger average age, and that is commonly related to specific mutations. And so the majority of Parkinson's disease occurs what we call sporadically, so without a hereditary or identified specific mutation that we are aware of. But some is related to a mutation, and those tend to occur at a younger age, but that's not the majority.
Karen Weintraub:
And is it clear what causes Parkinson's? You mentioned the neurons, but is there still some mystery there, and can the causes vary from person to person?
Dr. Viviane Tabar:
There is a lot of mystery. So in simple terms, we do not know the etiology of Parkinson's disease very specifically. Many things have been invoked, the environment, environmental toxins, a genetic predisposition outside of the genetic forms of the disease.
And we can talk a lot about some exciting science trying to dissect what's going on, the role of inflammation, et cetera. But the short answer to your question is we're not able today to tell a patient what caused their Parkinson's, again, outside the relatively uncommon hereditary forms.
Karen Weintraub:
And can you walk us a little bit through how Parkinson's progresses over time? Is there a sort of a path, many paths, what does that look like?
Dr. Viviane Tabar:
So yes, there are many paths, but let's take an average situation. The patient would reach out to a physician, eventually come to the attention of a neurologist, they're examined, their brain scan is obtained. In the case of Parkinson's, often that scan is fine and normal to age and the symptoms are identified often, as we said earlier, motor symptoms.
The common situation is that they get started on a form of dopamine that can reach the brain, and that makes them feel better and that is often referred to as the honeymoon period. And that goes on for a few years where the patient is almost back to normal but dependent on the medicine.
And as time goes by, the disease process is such that they are losing more and more of their dopamine neurons. And at some point we start or the treating neurologist starts escalating the dose of the medication. And there are other medications that can support that. But essentially within a few years or several years depending, they reach a point where they're starting to experience side effects from the medication and a shortening of the periods where they are feeling okay and functioning.
And that is where we start getting stuck in that there are no new medications that, I shouldn't say no new medications, there's always new medications, no formulations that try to extend the ability to help the individual. But you clearly plateau in terms of the effectiveness of pharmacological therapy for a lot of patients, not all.
There are options that are surgical like inserting electrodes that is called deep brain stimulation, which will work for some patients. But we reach a point where the patient has lost most of their dopaminergic neurons and there is not much more that can be offered today to help the individual. Hence, the idea of what if we could replace those degenerated dopamine neurons?
Karen Weintraub:
Which brings us to Dr. Studer. Dr. Studer, when did you first think about using stem cells as a possible way to treat Parkinson's?
Dr. Lorenz Studer:
Well, it's really a very long story. In fact, it's I think nearly three decades when we first had the idea of doing so, which was the question, "Now, can we really replace cells in the brain and what will be the right source?" In fact, that was the goal of my laboratory starting 25 years ago, finding exactly what's the source of dopamine neurons.
The challenge is how do you make this very, very specific nerve cell in the brain? And so that was a long journey, took us at least 10 years of basic research to understand, now what is the code of development? It's a little bit like trying to go through the steps that the cells go in normal development, but give them those signals one by one in a culture dish. And so it's a little bit like a code that we need to decipher and then to apply to the cells.
And by 2011, we could do that finally in a study that showed that we did a good job because when we implant those cells back into a mouse, in a rat or in a monkey model of Parkinson's disease, we see benefit in that model. And that really then opened up the whole next new step, now can we do that not just in a animal model, but maybe eventually in humans? That was what they call the proof of concept. But then obviously it was not a long journey to get to the ultimate clinical patient.
Karen Weintraub:
And how might the stem cell therapies transform the treatment landscape? What opportunities does this offer? And are there specific symptoms that you expect to get better or everything or certain symptoms?
Dr. Lorenz Studer:
The dopamine acts primarily on the movement-related symptoms. That's the area where we think we can make the biggest impact. Whether it's also going to affect all the symptoms, it's more questionable. Now, for example, again, we said the patients can have loss of smell, they can have problems with severe constipation, and at later stage of the disease, cognitive issues.
And at this point we don't have a good reason to believe that this therapy will also help with those symptoms. This has to be tested. It could be indirect effects, but the main effect we expect is that the movement disorder should improve.
Again, we don't want to overstate it, but in a dream scenario, it would be you have still Parkinson's disease, so you cannot cure Parkinson's disease, but maybe if it worked, ideally you could cure the movement disorder component of Parkinson's disease.
And so I think that's really what we are trying to develop with this type of cell therapy. And maybe in the future this will open up the same approach for all the cell types that might affect all the symptoms as well. So it's also kind of opening up the door to many other cell therapies in Parkinson's itself and maybe in other diseases as well, because it's one of the first cases now where really you actually replacing nerve cells in the brain, which sounds like a little bit of a science fiction approach. But I think this is one of the first examples where we really tried to attempt that and hopefully opening the door now for applications in the future.
Karen Weintraub:
And you said we can't call this a cure, obviously it's early days, but what would it take to get to a cure? More cell types?
Dr. Lorenz Studer:
Yeah. I think, because again, Parkinson's has more than just a movement disorder. So all that's not just movement-related, there is late stages cognitive problems, gastrointestinal problems, sleep problems, and those are unlikely to be treated with this cell type.
So what you can envisage is yes, well, maybe you would have additional cell types that can attack that, or ideally, you brought that up now, what causes Parkinson's disease, it'll be a complementary approach where you would give the cells back, because many dopamine cells are already lost by the time you're diagnosed.
So you get that movement-related symptoms hopefully restored, but at the same time, you'll find, like the whole field, many thousands researchers try to do that, find a therapy that can slow down or stop the progression. So you would gain back the function that you've already lost, but you would maybe not get some of those later symptoms. That would be even bigger dream in the future.
Karen Weintraub:
I was going to ask, Dr. Studer, where the research goes from here?
Dr. Lorenz Studer:
We always talk about bench to bedside, but there's also a bedside to bench. So where you kind of try to figure out, so what could you do even better now with regard to the cells that they function maybe more quickly or they are more potent or they have some additional features like we discussed? How could it treat some of the other symptoms in the future? So I think that's a big area for Parkinson's disease itself. How can we get the most benefit out of this kind of an approach?
But then the other part is really there's so many other very severe diseases now. We talk about Alzheimer's disease, we talk about ELS and other disorders. Each of them might need a different approach, quite different. So in some case we don't think we can just replace nerve cells, but we still learn that maybe other approaches could be used in those specific disorders.
And it then gives us a lot of encouragement when we see some progress in one area that this might be not just kind of a one-time go, but we might have opportunities to now give some help to those very difficult to treat neurodegenerative disorders where even today, this has been kind of some of the value of this for many of the drugs.
Now, very, very few new drugs came up in the context of neurodegenerative disorders, and I don't think cell therapy is alone going to solve all of that, but it's yet the new tool that is becoming actually clinically a realistic option to replace cells, and I think that's quite exciting.
There's some examples, for example, for treating eye disorders, so-called people who get blindness, macular degeneration, where data look quite promising. There's some examples maybe in very severe seizures where [inaudible 00:12:35] could be useful. So I think this is one of the very, very first example now where we now go all the way to this phase three study, but in the lab now we are thinking, "What did we learn? Why did it take us 25 years, for example? How can you make it quicker and what would be some of the next targets?"
Because from the stem cell side, we learned a lot. So by now we can pretty much make any cell type of the brain. So that's a language to make this as no longer limiting. What's limiting is now to know what's really needed in each individual patient, which is going to be quite distinct and will take, again, a couple of years, but pretty confident not another 25-year step.
Karen Weintraub:
Well, we will stay tuned for that very exciting work. Thank you both so much for being on The Excerpt.
Dr. Lorenz Studer:
Thanks so much.
Dr. Viviane Tabar:
Thank you for having us.
Karen Weintraub:
Thanks to our senior producers, Shannon Rae Green and Kaely Monahan, for their production assistance. Our executive producer is Laura Beatty.
Let us know what you think of this episode by sending a note to [e-mail]. Thanks for listening. I'm USA TODAY Health Reporter Karen Weintraub. Taylor Wilson will be back tomorrow morning with another episode of The Excerpt.