Recent advancements in engineering mean that the first preclinical trials for an artificial kidney could happen as soon as 18 months from now
Like all those whose kidneys have failed, Scott Burton’s life revolves around dialysis. For nearly two decades, Burton has been hooked up (or, since 2020, has hooked himself up at home) to a dialysis machine that performs the job his kidneys normally would. The process is arduous, time-consuming, and expensive. Except for a brief window before his body rejected a kidney transplant, Burton has depended on machines to take the place of his kidneys since he was 12-years-old. His whole life, the 39-year-old says, revolves around dialysis.
“Whenever I try to plan anything, I also have to plan my dialysis,” says Burton says, who works as a freelance videographer and editor. “It’s a full-time job in itself.”
Many of those on dialysis are in line for a kidney transplant that would allow them to trade thrice-weekly dialysis and strict dietary limits for a lifetime of immunosuppressants. Burton’s previous transplant means that his body will likely reject another donated kidney unless it matches perfectly—something he’s not counting on. It’s why he’s enthusiastic about the development of artificial kidneys, small wearable or implantable devices that would do the job of a healthy kidney while giving users like Burton more flexibility for traveling, working, and more.
Still, the devices aren’t ready for testing in humans—yet. But recent advancements in engineering mean that the first preclinical trials for an artificial kidney could happen as soon as 18 months from now, according to Jonathan Himmelfarb, a nephrologist at the University of Washington.
“It would liberate people with kidney failure,” Himmelfarb says.
An engineering marvel
Compared to the heart or the brain, the kidney doesn’t get as much respect from the medical profession, but its job is far more complex. “It does hundreds of different things,” says UCLA’s Ira Kurtz.
Kurtz would know. He’s worked as a nephrologist for 37 years, devoting his career to helping those with kidney disease. While his colleagues in cardiology and endocrinology have seen major advances in the development of artificial hearts and insulin pumps, little has changed for patients on hemodialysis. The machines remain bulky and require large volumes of a liquid called dialysate to remove toxins from a patient’s blood, along with gallons of purified water. A kidney transplant is the next best thing to someone’s own, functioning organ, but with over 600,000 Americans on dialysis and only about 100,000 kidney transplants each year, most of those in kidney failure are stuck on dialysis.
Part of the lack of progress in artificial kidney design is the sheer complexity of the kidney’s job. Each of the 45 different cell types in the kidney do something different.
Part of the lack of progress in artificial kidney design is the sheer complexity of the kidney’s job. To build an artificial heart, Kurtz says, you basically need to engineer a pump. An artificial pancreas needs to balance blood sugar levels with insulin secretion. While neither of these tasks is simple, they are fairly straightforward. The kidney, on the other hand, does more than get rid of waste products like urea and other toxins. Each of the 45 different cell types in the kidney do something different, helping to regulate electrolytes like sodium, potassium, and phosphorous; maintaining blood pressure and water balance; guiding the body’s hormonal and inflammatory responses; and aiding in the formation of red blood cells.
There's been little progress for patients during Ira Kurtz's 37 years as a nephrologist. Artificial kidneys would change that.
UCLA
Dialysis primarily filters waste, and does so well enough to keep someone alive, but it isn’t a true artificial kidney because it doesn’t perform the kidney’s other jobs, according to Kurtz, such as sensing levels of toxins, wastes, and electrolytes in the blood. Due to the size and water requirements of existing dialysis machines, the equipment isn’t portable. Physicians write a prescription for a certain duration of dialysis and assess how well it’s working with semi-regular blood tests. The process of dialysis itself, however, is conducted blind. Doctors can’t tell how much dialysis a patient needs based on kidney values at the time of treatment, says Meera Harhay, a nephrologist at Drexel University in Philadelphia.
But it’s the impact of dialysis on their day-to-day lives that creates the most problems for patients. Only one-quarter of those on dialysis are able to remain employed (compared to 85% of similar-aged adults), and many report a low quality of life. Having more flexibility in life would make a major different to her patients, Harhay says.
“Almost half their week is taken up by the burden of their treatment. It really eats away at their freedom and their ability to do things that add value to their life,” she says.
Art imitates life
The challenge for artificial kidney designers was how to compress the kidney’s natural functions into a portable, wearable, or implantable device that wouldn’t need constant access to gallons of purified and sterilized water. The other universal challenge they faced was ensuring that any part of the artificial kidney that would come in contact with blood was kept germ-free to prevent infection.
As part of last year’s KidneyX Prize, a partnership between the U.S. Department of Health and Human Services and the American Society of Nephrology, inventors were challenged to create prototypes for artificial kidneys. Himmelfarb’s team at the University of Washington’s Center for Dialysis Innovation won the prize by focusing on miniaturizing existing technologies to create a portable dialysis machine. The backpack sized AKTIV device (Ambulatory Kidney to Increase Vitality) will recycle dialysate in a closed loop system that removes urea from blood and uses light-based chemical reactions to convert the urea to nitrogen and carbon dioxide, which allows the dialysate to be recirculated.
Himmelfarb says that the AKTIV can be used when at home, work, or traveling, which will give users more flexibility and freedom. “If you had a 30-pound device that you could put in the overhead bins when traveling, you could go visit your grandkids,” he says.
Kurtz’s team at UCLA partnered with the U.S. Kidney Research Corporation and Arkansas University to develop a dialysate-free desktop device (about the size of a small printer) as the first phase of a progression that will he hopes will lead to something small and implantable. Part of the reason for the artificial kidney’s size, Kurtz says, is the number of functions his team are cramming into it. Not only will it filter urea from blood, but it will also use electricity to help regulate electrolyte levels in a process called electrodeionization. Kurtz emphasizes that these additional functions are what makes his design a true artificial kidney instead of just a small dialysis machine.
One version of an artificial kidney.
UCLA
“It doesn't have just a static function. It has a bank of sensors that measure chemicals in the blood and feeds that information back to the device,” Kurtz says.
Other startups are getting in on the game. Nephria Bio, a spinout from the South Korean-based EOFlow, is working to develop a wearable dialysis device, akin to an insulin pump, that uses miniature cartridges with nanomaterial filters to clean blood (Harhay is a scientific advisor to Nephria). Ian Welsford, Nephria’s co-founder and CTO, says that the device’s design means that it can also be used to treat acute kidney injuries in resource-limited settings. These potentials have garnered interest and investment in artificial kidneys from the U.S. Department of Defense.
For his part, Burton is most interested in an implantable device, as that would give him the most freedom. Even having a regular outpatient procedure to change batteries or filters would be a minor inconvenience to him.
“Being plugged into a machine, that’s not mimicking life,” he says.
Amber Freed and Maxwell near their home in Denver, Colorado.
Getting the diagnosis took months of painful, invasive procedures, as well as fighting with the health insurance to get the genetic testing approved. Finally, in June 2018, doctors at the Children's Hospital Colorado gave the Freeds their son's diagnosis—a genetic mutation so rare it didn't even have a name, just a bunch of letters jammed together into a word SLC6A1—same as the name of the mutated gene. The mutation, with only 40 cases known worldwide at the time, caused developmental disabilities, movement and speech disorders, and a debilitating form of epilepsy.
The doctors didn't know much about the disorder, but they said that Maxwell would also regress in his development when he turned three or four. They couldn't tell how long he would live. "Hopefully you would become an expert and educate us about it," they said, as they gave Freed a five-page paper on the SLC6A1 and told her to start calling scientists if she wanted to help her son in any way. When she Googled the name, nothing came up. She felt horrified. "Our disease was too rare to care."
Freed's husband, a 6'2'' college football player broke down in sobs and she realized that if anything could be done to help Maxwell, she'd have be the one to do it. "I understood that I had to fight like a mother," she says. "And a determined mother can do a lot of things."
The Freed family.
Courtesy Amber Freed
She quit her job as an equity analyst the day of the diagnosis and became a full-time SLC6A1 citizen scientist looking for researchers studying mutations of this gene. In the wee hours of the morning, she called scientists in Europe. As the day progressed, she called researchers on the East Coast, followed by the West in the afternoon. In the evening, she switched to Asia and Australia. She asked them the same question. "Can you help explain my gene and how do we fix it?"
Scientists need money to do research, so Freed launched Milestones for Maxwell fundraising campaign, and a SLC6A1 Connect patient advocacy nonprofit, dedicated to improving the lives of children and families battling this rare condition. And then it became clear that the mutation wasn't as rare as it seemed. As other parents began to discover her nonprofit, the number of known cases rose from 40 to 100, and later to 400, Freed says. "The disease is only rare until it messes with the wrong mother."
It took one mother to find another to start looking into what's happening inside Maxwell's brain. Freed came across Jeanne Paz, a Gladstone Institutes researcher who studies epilepsy with particular interest in absence or silent seizures—those that don't manifest by convulsions, but rather make patients absently stare into space—and that's one type of seizures Maxwell has. "It's like a brief period of silence in the brain during which the person doesn't pay attention to what's happening, and as soon as they come out of the seizure they are back to life," Paz explains. "It's like a pause button on consciousness." She was working to understand the underlying biology.
To understand how seizures begin, spread and stop, Paz uses optogenetics in mice. From words "genetic" and "optikós," which means visible in Greek, the optogenetics technique involves two steps. First, scientists introduce a light-sensitive gene into a specific brain cell type—for example into excitatory neurons that release glutamate, a neurotransmitter, which activates other cells in the brain. Then they implant a very thin optical fiber into the brain area where they forged these light-sensitive neurons. As they shine the light through the optical fiber, researchers can make excitatory neurons to release glutamate—or instead tell them to stop being active and "shut up". The ability to control what these neurons of interest do, quite literally sheds light onto where seizures start, how they propagate and what cells are involved in stopping them.
"Let's say a seizure started and we shine the light that reduces the activity of specific neurons," Paz explains. "If that stops the seizure, we know that activating those cells was necessary to maintain the seizure." Likewise, shutting down their activity will make the seizure stop.
Freed reached out to Paz in 2019 and the two women had an instant connection. They were both passionate about brain and seizures research, even if for different reasons. Freed asked Paz if she would study her son's seizures and Paz agreed.
To do that, Paz needed mice that carried the SLC6A1 mutation, so Freed found a company in China that created them to specs. The company replaced a mouse SLC6A1 gene with a human mutated one and shipped them over to Paz's lab. "We call them Maxwell mice," Paz says, "and we are now implanting electrodes into them to see which brain regions generate seizures." That would help them understand what goes wrong and what brain cells are malfunctioning in the SLC6A1 mice—and help scientists better understand what might cause seizures in children.
Bred to carry SLC6A1 mutation, these "Maxwell mice" will help better understand this debilitating genetic disease. (These mice are from Vanderbilt University, where researchers are also studying SLC6A1.)
Courtesy Amber Freed
This information—along with other research Amber is funding in other institutions—will inform the development of a novel genetic treatment, in which scientists would deploy a harmless virus to deliver a healthy, working copy of the SLC6A1 gene into the mice brains. They would likely deliver the therapeutic via a spinal tap infusion, and if it works and doesn't produce side effects in mice, the human trials will follow.
In the meantime, Freed is raising money to fund other research of various stop-gap measures. On April 22, 2021, she updated her Milestone for Maxwell page with a post that her nonprofit is funding yet another effort. It is a trial at Weill Cornell Medicine in New York City, in which doctors will use an already FDA-approved drug, which was recently repurposed for the SLC6A1 condition to treat epilepsy in these children. "It will buy us time," Freed says—while the gene therapy effort progresses.
Freed is determined to beat SLC6A1 before it beats down her family. She hopes to put an end to this disease—and similar genetic diseases—once and for all. Her goal is not only to have scientists create a remedy, but also to add the mutation to a newborn screening panel. That way, children born with this condition in the future would receive gene therapy before they even leave the hospital.
"I don't want there to be another Maxwell Freed," she says, "and that's why I am fighting like a mother." The gene therapy trial still might be a few years away, but the Weill Cornell one aims to launch very soon—possibly around Mother's Day. This is yet another milestone for Maxwell, another baby step forward—and the best gift a mother can get.