Tardigrades can completely dehydrate and later rehydrate themselves, a survival trick that scientists are harnessing to preserve medicines in hot temperatures.
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.
Dr. Robert Montgomery, almost one year post-transplant, at a vineyard in Casablanca, Chile, August 2019.
Having spent my working life as a transplant surgeon, it is the ultimate irony that I have now become a heart transplant patient. I knew this was a possibility since 1987, when I was 27 years old and I received a phone call from my sister-in-law telling me that my 35-year-old brother, Rich, had just died suddenly while water skiing.
Living from one heartbeat to the next I knew I had to get it right and nail my life—and in that regard my disease was a blessing.
After his autopsy, dots were connected and it was clear that the mysterious heart disease my father had died from when I was 15 years old was genetic. I was evaluated and it was clear that I too had inherited cardiomyopathy, a progressive weakening condition of the heart muscle that often leads to dangerous rhythm disturbances and sudden death. My doctors urged me to have a newly developed device called an implantable cardioverter-defibrillator (ICD) surgically placed in my abdomen and chest to monitor and shock my heart back into normal rhythm should I have a sudden cardiac arrest.
They also told me I was the first surgeon in the world to undergo an ICD implant and that having one of these devices would not be compatible with the life of a surgeon and I should change careers to something less rigorous. With the support of a mentor and armed with what the British refer to as my "bloody-mindedness," I refused to give up this dream of becoming a transplant surgeon. I completed my surgical training and embarked on my career.
What followed were periods of stability punctuated by near-death experiences. I had a family, was productive in my work, and got on with life, knowing that this was a fragile situation that could turn on its head in a moment. In a way, it made my decisions about how to spend my time and focus my efforts more deliberate and purposeful. Living from one heartbeat to the next I knew I had to get it right and nail my life—and in that regard my disease was a blessing.
In 2017 while pursuing my passion for the outdoors in a remote part of Patagonia, I collapsed from bacterial pneumonia and sepsis. Unknowingly, I had brought in my lungs one of those super-bugs that you read about from the hospital where I worked. Several days into the trip, the bacteria entered my blood stream and brought me as close to death as a human can get.
I lay for nearly 3 weeks in a coma on a stretcher in a tiny hospital in Argentina, septic and in cardiogenic shock before stabilizing enough to be evaced to NYU Langone Hospital, where I was on staff. I awoke helpless, unable to walk, talk, or swallow food or drink. It was a long shot but I managed to recover completely from this episode; after 3 months, I returned to work and the operating room. My heart rebounded, but never back to where it had been.
Then, on the eve of my mother's funeral, I arrested while watching a Broadway show, and this time my ICD failed to revive me. There was prolonged CPR that broke my ribs and spine and a final shock that recaptured my heart. It was literally a show stopper and I awoke to a standing ovation from the New York theatre audience who were stunned by my modern recreation of the biblical story of Lazarus, or for the more hip among them, my real-life rendition of the resurrection of Jon Snow at the end of season 5 of Game of Thrones.
Against the advice of my doctors, I attended my mom's funeral and again tried to regain some sense of normalcy. We discussed a transplant at this point but, believe it or not, there is such a scarcity of organs I was not yet "sick enough" to get enough priority to receive a heart. I had more surgery to supercharge my ICD so it would be more likely to save my life the next time -- and there would be a next time, I knew.
As a transplant surgeon, I have been involved in some important innovations to expand the number of organs available for transplantation.
Months later in Matera, Italy, where I was attending a medical meeting, I developed what is referred to as ventricular tachycardia storm. I had 4 cardiac arrests over a 3-hour period. With the first one, I fell on to a stone floor and split my forehead open. When I arrived at the small hospital it seemed like Patagonia all over again. One of the first people I met was a Catholic priest who gave me the Last Rights.
I knew now was the moment and so with the help of one of my colleagues who was at the meeting with me and the compassion of the Italian doctors who supplied my friend with resuscitation medications and left my IV in place, I signed out of the hospital against medical advice and boarded a commercial flight back to New York. I was admitted to the NYU intensive care unit and received a heart transplant 3 weeks later.
Now, what I haven't said is that as a transplant surgeon, I have been involved in some important innovations to expand the number of organs available for transplantation. I came to NYU in 2016 to start a new Transplant Institute which included inaugurating a heart transplant program. We hired heart transplant surgeons, cardiologists, and put together a team that unbeknownst to me at the time, would save my life a year later.
It gets even more interesting. One of the innovations that I had been involved in from its inception in the 1990s was using organs from donors at risk for transmitting viruses like HIV and Hepatitis C (Hep C). We popularized new ways to detect these viruses in donors and ensure that the risk was minimized as much as possible so patients in need of a life-saving transplant could utilize these organs.
When the opioid crisis hit hard about four years ago, there were suddenly a lot of potential donors who were IV drug users and 25 percent of them were known to be infected with Hep C (which is spread by needles). In 2018, 49,000 people died in the U.S. from drug overdoses. There were many more donors with Hep C than potential recipients who had previously been exposed to Hep C, and so more than half of these otherwise perfectly good organs were being discarded. At the same time, a new class of drugs was being tested that could cure Hep C.
I was at Johns Hopkins at the time and our team developed a protocol for using these Hep C positive organs for Hep C negative recipients who were willing to take them, even knowing that they were likely to become infected with the virus. We would then treat them after the transplant with this new class of drugs and in all likelihood, cure them. I brought this protocol with me to NYU.
When my own time came, I accepted a Hep C heart from a donor who overdosed on heroin. I became infected with Hep C and it was then eliminated from my body with 2 months of anti-viral therapy. All along this unlikely journey, I was seemingly making decisions that would converge upon that moment in time when I would arise to catch the heart that was meant for me.
Dr. Montgomery with his wife Denyce Graves, September 2019.
(Courtesy Montgomery)
Today, I am almost exactly one year post-transplant, back to work, operating, traveling, enjoying the outdoors, and giving lectures. My heart disease is gone; gone when my heart was removed. Gone also is my ICD. I am no longer at risk for a sudden cardiac death. I traded all that for the life of a transplant patient, which has its own set of challenges, but I clearly traded up. It is cliché, I know, but I enjoy every moment of every day. It is a miracle I am still here.