An Investigational Drug Offers Hope to Patients with a Disabling Neuromuscular Disease
Robert Thomas was a devoted runner, gym goer, and crew member on a sailing team in San Diego when, in his 40s, he noticed that his range of movement was becoming more limited.
He thought he was just getting older, but when he was hiking an uphill trail in Lake Tahoe, he kept tripping over rocks. "I'd never had this happen before," Robert says. "I knew something was wrong but didn't know what it was."
It wasn't until age 50 when he was diagnosed with Charcot-Marie-Tooth disease. The genetic disorder damages the peripheral nerves, which connect the brain and spinal cord to the rest of the body. This network of nerves is responsible for relaying information and signals about sensation, movement, and motor coordination. Over time, the disease causes debilitating muscle weakness and the loss of limb control.
Charcot-Marie-Tooth usually presents itself in childhood or in a person's teens, but in some patients, like Robert, onset can be later in life. Symptoms may include muscle cramping, tingling, or burning. Many patients also have high foot arches or hammer toes — toes that curl from the middle joint instead of pointing forward. Those affected often have difficulty walking and may lose sensation in their lower legs, feet, hands, or forearms. One of the most common rare diseases, it affects around 130,000 people in the United States and 2.8 million worldwide.
Like many people with Charcot-Marie-Tooth, or CMT, Robert wears corrective braces on his legs to help with walking. Now 61, he can't run or sail anymore because of the disease, but he still works out regularly and can hike occasionally. CMT also affects his grip, so he has to use special straps while doing some exercises.
For the past few years, Robert has been participating in a clinical trial for an investigational CMT drug. He takes the liquid formulation every morning and evening using an oral syringe. Scientists are following patients like Robert to learn if their symptoms stabilize or improve while on the drug. Dubbed PXT300, the drug was designed by French biopharmaceutical company Pharnext and is the farthest along in development for CMT. If approved, it would be the first drug for the disease.
Currently, there's no cure for CMT, only supportive treatments like pain medication. Some individuals receive physical and occupational therapy. A drug for CMT could be a game-changer for patients whose quality of life is severely affected by the disease.
Genetic Underpinnings
CMT arises from mutations in genes that are responsible for creating and maintaining the myelin sheath — the insulating layer around nerves. Pharnext's drug is meant to treat patients with CMT1A, the most common form of the disease, which represents about half of CMT cases. Around 5% of those with CMT1A become severely disabled and end up in wheelchairs. People with CMT1A have an extra copy of the gene PMP22, which makes a protein that's needed to maintain the myelin sheath around peripheral nerves.
Typically, an individual inherits one copy of PMP22 from each parent. But a person with CMT1A receives a copy of PMP22 from one parent and two copies from a parent with the disease. This extra copy of the gene results in excess protein production, which damages the cells responsible for preserving and regenerating the myelin sheath, called Schwann cells.
The myelin sheath helps ensure that a signal from the brain gets carried to nerves in the muscles so that a part of the body can carry out a particular action or movement. This sheath is like the insulation on an electrical cord and the action is like a light bulb. If the insulation is fine, the light bulb turns on. But if the insulation is frayed, the light will flicker.
"The same happens to these patients," says David Horn Solomon, CEO of Pharnext. "The signal to their muscle is weak and flickers." Over time, their muscles become weaker and thinner.
The PMP22 gene has proven difficult to target with a drug because it's located in a protected space — the Schwann cells that make up the insulation around nerves. "There's not an easy way to tamp it down," Solomon says.
Another company, Acceleron Pharma of Cambridge, Massachusetts, was developing an injectable CMT drug meant to increase the strength of leg muscles. But the company halted development last year after the experimental drug failed in a mid-stage trial. While the drug led to a statistically significant increase in muscle volume, it didn't translate to improvements in muscle function or quality of life for trial participants.
Made by Design
Pharnext's drug, PXT3003, is a combination of three existing drugs — baclofen, a muscle relaxant; naltrexone, a drug that decreases the desire for alcohol and opioids; and sorbitol, a type of sugar alcohol.
The company designed the drug using its artificial intelligence platform, which screened 20,000 existing drugs to predict combinations that could inhibit the PMP22 gene and thereby lower protein production. The AI system narrowed the search to several hundreds of combinations and Pharnext tested around 75 of them in the lab before landing on baclofen, naltrexone, and sorbitol. Individually, the drugs don't have much effect on the PMP22 gene. But combined, they work to lower how much protein the gene makes.
"How the drug inside the cell reduces expression isn't quite clear yet," says Florian Thomas, director of the Hereditary Neuropathy Center, and founding chair and professor in the department of neurology at Hackensack University Medical Center and Hackensack Meridian School of Medicine in New Jersey (no relation to Robert Thomas, the CMT patient). "By reducing the amount of protein being produced, we hopefully can stabilize the nerves."
In rodents genetically engineered to have the PMP22 gene, the drug reduced protein levels and delayed onset of muscle weakness when given to rats. In another animal study, the drug increased the size of the myelin sheath around nerves in rats.
"Like humans with CMT, one of the problems the animals have is they can't grip things, their grip strength is poor," Solomon says. But when treated with Pharnext's drug, "the grip strength of these animals improves dramatically even over 12 weeks."
Human trials look encouraging, too. But the company ran into a manufacturing issue during a late-stage trial. The drug requires refrigeration, and as a result of temperature changes, crystals formed inside vials containing the high dose of the drug. The study was a double-blind trial, meaning neither the trial participants nor investigators were supposed to know who received the high dose of the drug, who received the low dose, and who received a placebo. In these types of studies, the placebo and experimental drug should look the same so that investigators can't tell them apart. But because only the high dose contained crystals, not the low dose or placebo, regulators said the trial data could be biased.
Pharnext is now conducting a new randomized, double-blind trial to prove that its drug works. The study is recruiting individuals aged 16 through 65 years old with mild to moderate CMT. The company hopes to show that the drug can stop patients' symptoms from worsening, or in the best case scenario, possibly even improve them. The company doesn't think the drug will be able to help people with severe forms of the disease.
"In neurologic disease, you're looking for plasticity, where there's still the possibility of stabilization or reversal," Solomon says. Plasticity refers to the ability of the nervous system to change and adapt in response to stimuli.
Preventing Disability
Allison Moore, a CMT patient and founder and CEO of the Hereditary Neuropathy Foundation, has been following drug development for CMT since she founded the organization in 2001. She says many investigational drugs haven't moved forward because they've shown little success in animals. The fact that Pharnext's drug has made it to a late-stage human trial is promising, she says.
"It's really exciting," Moore says. "There's a chance that if you take the drug early before you're very severe, you'll end up not developing the disease to a level that's super disabling."
CMT has damaged Moore's peroneal nerve, a main nerve in the foot. As a result, she has foot drop, the inability to lift the front part of her foot, and needs to wear leg braces to help her walk. "The idea that you could take this early on and that it could stop progression, that's the hope that we have."
Thomas, the neurologist, says a drug doesn't have to be a cure to have a significant impact on patients. "If I have a CMT patient who's 50 years old, that patient will be more disabled by age 60," he says. "If I can treat that person with a drug, and that person is just as disabled at age 60 as they were at age 50, that's transformative in my mind."
While Robert Thomas says he hasn't noticed a dramatic improvement since he's been on the drug, he does think it's helping. Robert is now in an open-label study, which means he and his health provider are aware that he's receiving the drug.
When the COVID-19 pandemic hit, manufacturing and supply chain disruptions meant that Robert was without the trial drug for two months. When his medication ran out, his legs felt unstable again and walking was harder. "There was a clear distinction between being on and off that medication," he says.
Pharnext's current trial will take about a year and a half to complete. After that, the FDA will decide on whether to approve the drug for CMT patients.
As scientists learn more about the PMP22 gene and the more than 100 other genes that when mutated cause CMT, more precise treatments could be possible. For instance, scientists have used the gene-editing tool CRISPR to correct a CMT-causing mutation in human cells in the lab. The results were published August 16 in the journal Frontiers in Cell and Developmental Biology.
Pharnext is also interested in pursuing genetic treatments for CMT, but in the meantime, repurposed drugs may be the best shot at helping patients until more advanced treatments are available.
Meet Dr. Renee Wegrzyn, the first Director of President Biden's new health agency, ARPA-H
In today’s podcast episode, I talk with Renee Wegrzyn, appointed by President Biden as the first director of a health agency created last year, the Advanced Research Projects Agency for Health, or ARPA-H. It’s inspired by DARPA, the agency that develops innovations for the Defense department and has been credited with hatching world-changing technologies such as ARPANET, which became the internet.
Time will tell if ARPA-H will lead to similar achievements in the realm of health. That’s what President Biden and Congress expect in return for funding ARPA-H at 2.5 billion dollars over three years.
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How will the agency figure out which projects to take on, especially with so many patient advocates for different diseases demanding moonshot funding for rapid progress?
I talked with Dr. Wegrzyn about the opportunities and challenges, what lessons ARPA-H is borrowing from Operation Warp Speed, how she decided on the first ARPA-H project that was announced recently, why a separate agency was needed instead of reforming HHS and the National Institutes of Health to be better at innovation, and how ARPA-H will make progress on disease prevention in addition to treatments for cancer, Alzheimer’s and diabetes, among many other health priorities.
Dr. Wegrzyn’s resume leaves no doubt of her suitability for this role. She was a program manager at DARPA where she focused on applying gene editing and synthetic biology to the goal of improving biosecurity. For her work there, she received the Superior Public Service Medal and, in case that wasn’t enough ARPA experience, she also worked at another ARPA that leads advanced projects in intelligence, called I-ARPA. Before that, she ran technical teams in the private sector working on gene therapies and disease diagnostics, among other areas. She has been a vice president of business development at Gingko Bioworks and headed innovation at Concentric by Gingko. Her training and education includes a PhD and undergraduate degree in applied biology from the Georgia Institute of Technology and she did her postdoc as an Alexander von Humboldt Fellow in Heidelberg, Germany.
Dr. Wegrzyn told me that she’s “in the hot seat.” The pressure is on for ARPA-H especially after the need and potential for health innovation was spot lit by the pandemic and the unprecedented speed of vaccine development. We'll soon find out if ARPA-H can produce gamechangers in health that are equivalent to DARPA’s creation of the internet.
Show links:
ARPA-H - https://arpa-h.gov/
Dr. Wegrzyn profile - https://arpa-h.gov/people/renee-wegrzyn/
Dr. Wegrzyn Twitter - https://twitter.com/rwegrzyn?lang=en
President Biden Announces Dr. Wegrzyn's appointment - https://www.whitehouse.gov/briefing-room/statement...
Leaps.org coverage of ARPA-H - https://leaps.org/arpa/
ARPA-H program for joints to heal themselves - https://arpa-h.gov/news/nitro/ -
ARPA-H virtual talent search - https://arpa-h.gov/news/aco-talent-search/
Dr. Renee Wegrzyn was appointed director of ARPA-H last October.
Tiny, tough “water bears” may help bring new vaccines and medicines to sub-Saharan Africa
Microscopic tardigrades, widely considered to be some of the toughest animals on earth, can survive for decades without oxygen or water and are thought to have lived through a crash-landing on the moon. Also known as water bears, they survive by fully dehydrating and later rehydrating themselves – a feat only a few animals can accomplish. Now scientists are harnessing tardigrades’ talents to make medicines that can be dried and stored at ambient temperatures and later rehydrated for use—instead of being kept refrigerated or frozen.
Many biologics—pharmaceutical products made by using living cells or synthesized from biological sources—require refrigeration, which isn’t always available in many remote locales or places with unreliable electricity. These products include mRNA and other vaccines, monoclonal antibodies and immuno-therapies for cancer, rheumatoid arthritis and other conditions. Cooling is also needed for medicines for blood clotting disorders like hemophilia and for trauma patients.
Formulating biologics to withstand drying and hot temperatures has been the holy grail for pharmaceutical researchers for decades. It’s a hard feat to manage. “Biologic pharmaceuticals are highly efficacious, but many are inherently unstable,” says Thomas Boothby, assistant professor of molecular biology at University of Wyoming. Therefore, during storage and shipping, they must be refrigerated at 2 to 8 degrees Celsius (35 to 46 degrees Fahrenheit). Some must be frozen, typically at -20 degrees Celsius, but sometimes as low -90 degrees Celsius as was the case with the Pfizer Covid vaccine.
For Covid, fewer than 73 percent of the global population received even one dose. The need for refrigerated or frozen handling was partially to blame.
The costly cold chain
The logistics network that ensures those temperature requirements are met from production to administration is called the cold chain. This cold chain network is often unreliable or entirely lacking in remote, rural areas in developing nations that have malfunctioning electrical grids. “Almost all routine vaccines require a cold chain,” says Christopher Fox, senior vice president of formulations at the Access to Advanced Health Institute. But when the power goes out, so does refrigeration, putting refrigerated or frozen medical products at risk. Consequently, the mRNA vaccines developed for Covid-19 and other conditions, as well as more traditional vaccines for cholera, tetanus and other diseases, often can’t be delivered to the most remote parts of the world.
To understand the scope of the challenge, consider this: In the U.S., more than 984 million doses of Covid-19 vaccine have been distributed so far. Each one needed refrigeration that, even in the U.S., proved challenging. Now extrapolate to all vaccines and the entire world. For Covid, fewer than 73 percent of the global population received even one dose. The need for refrigerated or frozen handling was partially to blame.
Globally, the cold chain packaging market is valued at over $15 billion and is expected to exceed $60 billion by 2033.
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Freeze-drying, also called lyophilization, which is common for many vaccines, isn’t always an option. Many freeze-dried vaccines still need refrigeration, and even medicines approved for storage at ambient temperatures break down in the heat of sub-Saharan Africa. “Even in a freeze-dried state, biologics often will undergo partial rehydration and dehydration, which can be extremely damaging,” Boothby explains.
The cold chain is also very expensive to maintain. The global pharmaceutical cold chain packaging market is valued at more than $15 billion, and is expected to exceed $60 billion by 2033, according to a report by Future Market Insights. This cost is only expected to grow. According to the consulting company Accenture, the number of medicines that require the cold chain are expected to grow by 48 percent, compared to only 21 percent for non-cold-chain therapies.
Tardigrades to the rescue
Tardigrades are only about a millimeter long – with four legs and claws, and they lumber around like bears, thus their nickname – but could provide a big solution. “Tardigrades are unique in the animal kingdom, in that they’re able to survive a vast array of environmental insults,” says Boothby, the Wyoming professor. “They can be dried out, frozen, heated past the boiling point of water and irradiated at levels that are thousands of times more than you or I could survive.” So, his team is gradually unlocking tardigrades’ survival secrets and applying them to biologic pharmaceuticals to make them withstand both extreme heat and desiccation without losing efficacy.
Boothby’s team is focusing on blood clotting factor VIII, which, as the name implies, causes blood to clot. Currently, Boothby is concentrating on the so-called cytoplasmic abundant heat soluble (CAHS) protein family, which is found only in tardigrades, protecting them when they dry out. “We showed we can desiccate a biologic (blood clotting factor VIII, a key clotting component) in the presence of tardigrade proteins,” he says—without losing any of its effectiveness.
The researchers mixed the tardigrade protein with the blood clotting factor and then dried and rehydrated that substance six times without damaging the latter. This suggests that biologics protected with tardigrade proteins can withstand real-world fluctuations in humidity.
Furthermore, Boothby’s team found that when the blood clotting factor was dried and stabilized with tardigrade proteins, it retained its efficacy at temperatures as high as 95 degrees Celsius. That’s over 200 degrees Fahrenheit, much hotter than the 58 degrees Celsius that the World Meteorological Organization lists as the hottest recorded air temperature on earth. In contrast, without the protein, the blood clotting factor degraded significantly. The team published their findings in the journal Nature in March.
Although tardigrades rarely live more than 2.5 years, they have survived in a desiccated state for up to two decades, according to Animal Diversity Web. This suggests that tardigrades’ CAHS protein can protect biologic pharmaceuticals nearly indefinitely without refrigeration or freezing, which makes it significantly easier to deliver them in locations where refrigeration is unreliable or doesn’t exist.
The tricks of the tardigrades
Besides the CAHS proteins, tardigrades rely on a type of sugar called trehalose and some other protectants. So, rather than drying up, their cells solidify into rigid, glass-like structures. As that happens, viscosity between cells increases, thereby slowing their biological functions so much that they all but stop.
Now Boothby is combining CAHS D, one of the proteins in the CAHS family, with trehalose. He found that CAHS D and trehalose each protected proteins through repeated drying and rehydrating cycles. They also work synergistically, which means that together they might stabilize biologics under a variety of dry storage conditions.
“We’re finding the protective effect is not just additive but actually is synergistic,” he says. “We’re keen to see if something like that also holds true with different protein combinations.” If so, combinations could possibly protect against a variety of conditions.
Commercialization outlook
Before any stabilization technology for biologics can be commercialized, it first must be approved by the appropriate regulators. In the U.S., that’s the U.S. Food and Drug Administration. Developing a new formulation would require clinical testing and vast numbers of participants. So existing vaccines and biologics likely won’t be re-formulated for dry storage. “Many were developed decades ago,” says Fox. “They‘re not going to be reformulated into thermo-stable vaccines overnight,” if ever, he predicts.
Extending stability outside the cold chain, even for a few days, can have profound health, environmental and economic benefits.
Instead, this technology is most likely to be used for the new products and formulations that are just being created. New and improved vaccines will be the first to benefit. Good candidates include the plethora of mRNA vaccines, as well as biologic pharmaceuticals for neglected diseases that affect parts of the world where reliable cold chain is difficult to maintain, Boothby says. Some examples include new, more effective vaccines for malaria and for pathogenic Escherichia coli, which causes diarrhea.
Tallying up the benefits
Extending stability outside the cold chain, even for a few days, can have profound health, environmental and economic benefits. For instance, MenAfriVac, a meningitis vaccine (without tardigrade proteins) developed for sub-Saharan Africa, can be stored at up to 40 degrees Celsius for four days before administration. “If you have a few days where you don’t need to maintain the cold chain, it’s easier to transport vaccines to remote areas,” Fox says, where refrigeration does not exist or is not reliable.
Better health is an obvious benefit. MenAfriVac reduced suspected meningitis cases by 57 percent in the overall population and more than 99 percent among vaccinated individuals.
Lower healthcare costs are another benefit. One study done in Togo found that the cold chain-related costs increased the per dose vaccine price up to 11-fold. The ability to ship the vaccines using the usual cold chain, but transporting them at ambient temperatures for the final few days cut the cost in half.
There are environmental benefits, too, such as reducing fuel consumption and greenhouse gas emissions. Cold chain transports consume 20 percent more fuel than non-cold chain shipping, due to refrigeration equipment, according to the International Trade Administration.
A study by researchers at Johns Hopkins University compared the greenhouse gas emissions of the new, oral Vaxart COVID-19 vaccine (which doesn’t require refrigeration) with four intramuscular vaccines (which require refrigeration or freezing). While the Vaxart vaccine is still in clinical trials, the study found that “up to 82.25 million kilograms of CO2 could be averted by using oral vaccines in the U.S. alone.” That is akin to taking 17,700 vehicles out of service for one year.
Although tardigrades’ protective proteins won’t be a component of biologic pharmaceutics for several years, scientists are proving that this approach is viable. They are hopeful that a day will come when vaccines and biologics can be delivered anywhere in the world without needing refrigerators or freezers en route.