A scientist’s fifteen-year journey to develop a stem cell-based therapy that could one day help ALS patients.
“Can stem cells help me Clive?”
The sentence appeared slowly on a computer screen, each character separated by a pause while its author searched for the next character using a device controlled by his eye muscle.
The person asking the question was Jeff Kaufman, a Wisconsin man in his 40s completely paralyzed by amyotrophic lateral sclerosis (ALS). On the receiving end was Clive Svendsen, PhD, then a scientist at the University of Wisconsin-Madison, determined to understand how stem cells could help patients like Jeff.
Also known as Lou Gehrig’s disease, ALS is a rapid, aggressive neurodegenerative disease with a two to four-year life expectancy. ALS destroys the nerve cells that send signals from the brain and spinal cord to the muscles that control movement. Denervation, or loss of nerves, causes muscle weakness and atrophy, leaving patients unable to control their own bodies. Currently there are two FDA-approved ALS drugs in the US – riluzole and a new drug called edaravone (Radicava). However, they only slow disease progression in some ALS patients by a few months and there are no effective treatments that stop or cure the disease.
Given this poor prognosis, making ALS the focus of his research career was an easy decision. However, developing a therapeutic strategy was challenging to Svendsen. “The problem with ALS is we don’t know the cause,” he said. “Around 10% of ALS cases are genetic, and we know some of the genes involved, but 90% of cases are sporadic.” He explained that this black box makes it difficult for scientists to know where to start when trying to develop treatments for sporadic ALS cases that have no drug targets.
From Parkinson’s disease to ALS
Svendsen, who moved to Cedars-Sinai in Los Angeles to head the Cedars-Sinai Board of Governors Regenerative Medicine Institute in 2010, has worked on ALS for the past 15 years. Before that, he studied Parkinson’s disease, a long-term neurodegenerative disorder that affects movement, balance and speech. Unlike ALS, Parkinson’s patients have a longer life expectancy and more treatment options that alleviate symptoms of the disease, making their quality of life far better than ALS patients.
“I chose to work on ALS mainly because of the effects it has on ALS families,” explained Svendsen. “Being normal one day, and then becoming rapidly paralyzed was hard to see.”
The transition from Parkinson’s to ALS was not without a scientific reason however. Svendsen was studying how an important growth factor in the brain called Glial Cell Line-Derived Neurotrophic Factor or GDNF could be used to protect dopamine neurons in order to treat Parkinson’s patients. However other research suggested that GDNF was even more effective at protecting motor neurons, the nerve cells destroyed by ALS.
Armed with the knowledge of GDNF’s ability to protect motor neurons, Svendsen and his team developed an experimental stem cell-based therapy that they hoped would treat patients with the sporadic form of ALS. Instead of using stem cells to replace the motor neurons lost to ALS, Svendsen placed his bets on making another cell type in the brain, the astrocyte.
Rooting for the underdog
Astrocytes are the underdog cells of the brain, often overshadowed by neurons that send and receive information from the central nervous system to our bodies. Astrocytes have many important roles, one of the most critical being to support the functions of neurons. In ALS, astrocytes are also affected but in a different way than motor neurons. Instead of dying, ALS astrocytes become dysfunctional and thereby create a toxic environment inhospitable to the motors neurons they are supposed to assist.
“While the motor neurons clearly die in ALS, the astrocytes surrounding the motor neurons are also sick,” said Svendsen. “It’s a huge challenge to replace a motor neuron and make it grow a cable all the way to the muscle in an adult human. We couldn’t even get this to work in mice. So, I knew a more realistic strategy would be to replace the sick astrocytes in an ALS patients with fresh, healthy astrocytes. This potentially would have a regenerative effect on the environment around the existing motor neurons.”
The big idea was to combine both GDNF and astrocyte replacement. Svendsen set out to make healthy astrocytes from human brain stem cells that also produce therapeutic doses of GDNF and transplant these cells into the ALS patient spinal cord. Simply giving patients GDNF via pill wouldn’t work because the growth factor is unable to enter the brain or spinal cord tissue where it is needed. The hope, instead, was that the astrocytes would secrete the protective factor that would keep the patients’ motor neurons healthy and alive.
With critical funding from a CIRM Disease Team grant, Svendsen and his colleagues at Cedars-Sinai tested the feasibility of transplanting human brain stem cells (also referred to as neural progenitor cells) that secreted GDNF into a rat model of ALS. Their results were encouraging – the neural progenitor cells successfully developed into astrocytes and secreted GDNF, which collectively protected the rat motor neurons.
Svendsen describes the strategy as “a double whammy”: adding both healthy astrocytes and GDNF secretion to protect the motor neurons. “Replacing astrocytes has the potential to rejuvenate the niche where the motor neurons are. I think that’s a very powerful experimental approach to ALS.”
A fifteen year journey from bench to bedside
With promising preclinical data under his belt, Svendsen and his colleagues, including Robert Baloh, MD, PhD, director of neuromuscular medicine at the Cedars-Sinai Department of Neurology, and neurosurgeon J. Patrick Johnson, MD, designed a clinical trial that would test this experimental therapy in ALS patients. In October 2016, CIRM approved funding for a Phase I/IIa clinical trial assessing the safety of this novel human neural progenitor cell and gene therapy.
This is a first-in-human study, and as such, the U.S. Food and Drug Administration (FDA) required the team to transplant the cells into only one side of the lumbar spinal cord, which effectively means that only one of the patient’s legs will get the treatment. This will allow for a comparison of the function and progression of ALS in the leg on the treated side of the spinal cord compared with the leg on the untreated side.
The trial was approved to treat a total of 18 patients and started in May 2017.
Svendsen, who first started working on ALS back in 2002, describes his path to the clinic as a “very long and windy road.” He emphasized that this journey wouldn’t be possible without the hard work of his team, Cedars-Sinai and financial support from CIRM.
“It took ten years of preclinical studies and an enormous amount of work from many different people. Just producing the cells that we’re going to use took three years and a lot of trials and tribulations to make it a clinically viable product. It was really thanks to CIRM’s funding and the support of Cedars-Sinai that we got through it all. Without that kind of infrastructure, I can safely say we wouldn’t be here today.”
This “behind-the-scenes” view of how much time and effort it takes to translate a stem cell therapy from basic research into the clinic isn’t something that the public is often exposed to or aware of. Just as “Rome wasn’t built in a day,” Svendsen stressed that good quality stem cell trials take time, and that it’s important for people know how complicated these trials are.
It’s all about the patients
So, what motivates Svendsen to continue this long and harrowing journey to develop a treatment for ALS? He said the answer is easy. “I’m doing it for the patients,” he explained. “I’m not doing this for the money or glory. I just want to develop something that works for ALS, so we can help these patients.”
Svendsen revisited his story about Jeff Kaufman, a man he befriended at the Wisconsin ALS Chapter in 2003. Jeff had three daughters and a son, a wonderful wife, and was a successful lawyer when he was diagnosed with ALS.
“Jeff had basically everything, and then he was stricken with ALS. I still remember going to his house and he could only move his eyes at that point. He tapped out the words ‘Can stem cells help me Clive?’ on his computer screen. And my heart sank because I knew how much and how long it was going to take. I was very realistic so I said, ‘Yes Jeff, but it’s going to take time and money. And even then, it’s a long shot.’ And he told me to go for it, and that stuck in my brain.”
It’s people like Jeff that make Svendsen get out of bed every morning and doggedly pursue a treatment for ALS. Sadly, Jeff passed away due to complications from ALS in 2010. Svendsen says what Jeff and other patients go through is tragic and unfair.
“There’s a gene that goes along with ALS and it’s called the ‘nice person gene,’” he said. “People with ALS are nice. I can’t explain it, but neurologists would say the same thing. You feel like it’s just not fair that it happens to those people.”
The future of stem cell therapies for ALS
It’s clear from speaking with Svendsen, that he is optimistic about the future of stem cell-based therapies for ALS. Scientists still need to unravel the actual causes of ALS. But the experimental stem cell treatments currently in development, including Svendsen’s, will hopefully prove effective at delaying disease progression and give ALS patients more quality years to live.
In the meantime, what concerns Svendsen is how vulnerable ALS patients are to being misled by unapproved stem cell clinics that claim to have cures. “Unfortunately, there are a lot of charlatans out there, and there are a lot of false claims being made. People feed off the desperation that you have in ALS. It’s not fair, and it’s completely wrong. They’ll mislead patients by saying ‘For $40,000 you can get a cure!’”
Compelling stories of patients cured of knee pain or diseases like ALS with injections of their own adult stem cells pop up in the news daily. Many of these stories refer to unapproved treatments from clinics that don’t provide scientific evidence that these treatments are safe and effective. Svendsen said there are reasonable, research-backed trials that are attempting to use adult stem cells to treat ALS. He commented, “I think it’s hard for the public to wade through all of these options and understand what’s real and what’s not real.”
Svendsen’s advice for ALS patients interested in enrolling in a stem cell trial or trying a new stem cell treatment is to be cautious. If a therapy sounds too good to be true, it probably is, and if it costs a lot of money, it probably isn’t legitimate, he explained.
He also wants patients to understand the reality of the current state of ALS stem cell trials. The approved stem cell trials he is aware of are not at the treatment stage yet.
“If you’re enrolled in a stem cell trial that is funded and reputable, then they will tell you honestly that it’s not a treatment. There is currently no approved treatment using stem cells for ALS,” Svendsen said.
This might seem like discouraging news to patients who don’t have time to wait for these trials to develop into treatments, but Svendsen pointed out that the when he started his research 15 years ago, the field of stem cell research was still in its infancy. A lot has been accomplished in the past decade-and-a-half and with talented scientists dedicated to ALS research like Svendsen, the next 15 years will likely offer new insights into ALS and hopefully stem cell-based treatments for a devastating disease that has no cure.
Svendsen hopes that one day, when someone like Jeff Kaufman asks him “Can stem cells help me Clive?” He’ll be able to say, yes they can, yes they can.