Scientists May Soon Be Able to Turn Off Pain with Gene Editing: Should They?
Scientists have long been aware that some people live with what's known as "congenital insensitivity to pain"—the inability to register the tingles, jolts, and aches that alert most people to injury or illness.
"If you break the chain of transmission somewhere along there, it doesn't matter what the message is—the recipient will not get it."
On the ospposite end of the spectrum, others suffer from hyperalgesia, or extreme pain; for those with erythromelalgia, also known as "Man on Fire Syndrome," warm temperatures can feel like searing heat—even wearing socks and shoes can make walking unbearable.
Strangely enough, the two conditions can be traced to mutations in the same gene, SCN9A. It produces a protein that exists in spinal cells—specifically, in the dorsal root ganglion—which transmits the sensation of pain from the nerves at the peripheral site of an injury into the central nervous system and to the brain. This fact may become the key to pain relief for the roughly 20 percent of Americans who suffer from chronic pain, and countless other patients around the world.
"If you break the chain of transmission somewhere along there, it doesn't matter what the message is—the recipient will not get it," said Dr. Fyodor Urnov, director of the Innovative Genomics Institute and a professor of molecular and cell biology at the University of California, Berkeley. "For scientists and clinicians who study this, [there's] this consistent tracking of: You break this gene, you stop feeling pain; make this gene hyperactive, you feel lots of pain—that really cuts through the correlation versus causation question."
Researchers tried for years, without much success, to find a chemical that would block that protein from working and therefore mute the pain sensation. The CRISPR-Cas9 gene editing tool could completely sidestep that approach and "turn off" pain directly.
Yet as CRISPR makes such targeted therapies increasingly possible, the ethical questions surrounding gene editing have taken on a new and more urgent cast—particularly in light of the work of the disgraced Chinese scientist He Jiankui, who announced in late 2018 that he had created the world's first genetically edited babies. He used CRISPR to edit two embryos, with the goal of disabling a gene that makes people susceptible to HIV infection; but then took the unprecedented step of implanting the edited embryos for pregnancy and birth.
Edits to germline cells, like the ones He undertook, involve alterations to gametes or embryos and carry much higher risk than somatic cell edits, since changes will be passed on to any future generations. There are also concerns that imprecise edits could result in mutations and end up causing more disorders. Recent developments, particularly the "search-and replace" prime-editing technique published last fall, will help minimize those accidental edits, but the fact remains that we have little understanding of the long-term effects of these germline edits—for the future of the patients themselves, or for the broader gene pool.
"We need to have appropriate venues where we deliberate and consider the ethical, legal and social implications of gene editing as a society."
It is much harder to predict the effects, harmful or otherwise, on the larger human population as a result of interactions with the environment or other genetic variations; with somatic cell edits, on the other hand— like the ones that would be made in an individual to turn off pain—only the person receiving the treatment is affected.
Beyond the somatic/germline distinction, there is also a larger ethical question over how much genetic interference society is willing to tolerate, which may be couched as the difference between therapeutic editing—interventions in response to a demonstrated medical need—and "enhancement" editing. The Chinese scientist He was roundly criticized in the scientific community for the fact that there are already much safer and more proven methods of preventing the parent-to-child transmission of HIV through the IVF process, making his genetic edits medically unnecessary. (The edits may also have increased the girls' risk of susceptibility to other viruses, like influenza and the West Nile virus.)
Yet there are even more extreme goals that CRISPR could be used to reach, ones further removed from any sort of medical treatment. The 1997 science fiction movie Gattaca imagined a dystopian future where genetic selection for strength and intelligence is common, creating a society that explicitly and unapologetically endorses eugenics. In the real world, Russian President Vladimir Putin has commented that genetic editing could be used to create "a genius mathematician, a brilliant musician or a soldier, a man who can fight without fear, compassion, regret or pain."
"[Such uses] would be considered using gene editing for 'enhancement,'" said Dr. Zubin Master, an associate professor of biomedical ethics at the Mayo Clinic, who noted that a series of studies have strongly suggested that members of the public, in the U.S. and around the world, are much less amenable to the prospect of gene editing for these purposes than for the treatment of illness and disease.
Putin's comments were made in 2017, before news of He's experiment broke; since then no country has moved to continue experiments on germline editing (although one Russian IVF specialist, Denis Rebrikov, appears ready to do so, if given approval). Master noted that the World Health Organization has an 18-person committee currently dedicated to considering these questions. The Expert Advisory Committee on Developing Global Standards for Governance and Oversight of Human Genome Editing first convened in March 2019; that July, it issued a recommendation to regulatory and ethics authorities in all countries to refrain from approving clinical application requests for work on human germline genome editing—the kind of alterations to genetic cells used by He. The committee's report and a fleshed-out set of guidelines is expected after its final meeting, in Geneva this September (unless the COVID-19 pandemic disrupts the timeline).
Regardless of the WHO's report, in the U.S., all regulations of new medical procedures are overseen at the federal level, subjected to extensive regulatory review by the FDA; the chance of any doctor or company going rogue is minimal to none. Likewise, the challenges we face are more on the regulatory end of the spectrum than the Gattaca end. Dr. Stephanie Malia Fullerton, a bioethics professor at the University of Washington, pointed out that eugenics not only typically involves state-sponsored control of reproduction, but requires a much more clearly delineated genetic basis of common complex traits—indeed, SCN9A is one way to get to pain, but is not the only source—and suggested that current concerns about over-prescribing opioids are a more pressing question for society to address.
In fact, Navega Therapeutics, based in San Diego, hopes to find out whether the intersection of this research into SCN9A and CRISPR would be an effective way to address the U.S. opioid crisis. Currently in a preclinical funding stage, Navega's approach focuses on editing epigenetic molecules attached to the basic DNA strand—the idea is that the gene's expression can be activated or suppressed rather than removed entirely, reducing the risk of unwanted side effects from permanently altering the genetic code.
As these studies focused on the sensation of pain go forward, what we are likely to see simultaneously is the use of CRISPR to target diseases that are the root causes of that pain. Last summer, Victoria Gray, a Mississippi woman with sickle cell disease was the second-ever person to be treated with CRISPR therapy in the U.S. The disease is caused by a genetic mutation that creates malformed blood cells, which can't carry oxygen as normal and get stuck inside blood vessels, causing debilitating pain. For the study, conducted in concert with CRISPR Therapeutics, of Cambridge, Mass., cells were removed from Gray's bone marrow, modified using CRISPR, and infused back into her body, a technique called ex vivo editing.
In early February this year, researchers at the University of Pennsylvania published a study on a first-in-human phase 1 clinical trial, in which three patients with advanced cancer received an infusion of ex vivo engineered T cells in an effort to improve antitumor immunity. The modified cells persisted for up to nine months, and the patients experienced no serious adverse side effects, suggesting that this sort of therapeutic gene editing can be performed safely and could potentially allow patients to avoid the excruciating process of chemotherapy.
Then, just this spring, researchers made another advance: The first attempt at in vivo CRISPR editing—where the edits happen inside the patient's body—is currently underway, as doctors attempt to treat a patient blinded by Leber congenital amaurosis, a rare genetic disorder. In an Oregon study sponsored by Editas Medicine and Allergan, the patient, a volunteer, was injected with a harmless virus carrying CRISPR gene-editing machinery; the hope is that the tool will be able to edit out the genetic defect and restore production of a crucial protein. Based on preliminary safety reports, the study has been cleared to continue, and data on higher doses may be available by the end of 2020. Editas Medicine and CRISPR Therapeutics are joined in this sphere by Intellia Therapeutics, which is seeking approval for a trial later this year on amyloidosis, a rare liver condition.
For any such treatment targeting SCN9A to make its way to human subjects, it would first need to undergo years' worth of testing—on mice, on primates, and then on volunteer patients after an extended informed-consent process. If everything went perfectly, Urnov estimates it could take at least three to four years end to end and cost between $5 and 10 million—but that "if" is huge.
"The idea of a regular human being, genetically pure of pain?"
And as that happens, "we need to have appropriate venues where we deliberate and consider the ethical, legal and social implications of gene editing as a society," Master said. CRISPR itself is open-source, but its application is subject to the approval of governments, institutions, and societies, which will need to figure out where to draw the line between miracle treatments and playing God. Something as unpleasant and ubiquitous as pain may in fact be the most appropriate place to start.
"The pain circuit is very old," Urnov said. "We have evolved with the senses that we have, and have become the species that we are, as a result of who we are, physiologically. Yes, I take Advil—but when I get a headache! The idea of a regular human being, genetically pure of pain?... The permanent disabling or turning down of the pain sensation, for anything other than a medical reason? … That seems to be challenging Mother Nature in the wrong ways."
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
Here are the promising studies covered in this week's Friday Five, featuring interviews with Dr. David Spiegel, associate chair of psychiatry and behavioral sciences at Stanford, and Dr. Filip Swirski, professor of medicine and cardiology at the Icahn School of Medicine at Mount Sinai.
Listen on Apple | Listen on Spotify | Listen on Stitcher | Listen on Amazon | Listen on Google
Here are the promising studies covered in this week's Friday Five, featuring interviews with Dr. David Spiegel, associate chair of psychiatry and behavioral sciences at Stanford, and Dr. Filip Swirski, professor of medicine and cardiology at the Icahn School of Medicine at Mount Sinai.
- Breathing this way cuts down on anxiety*
- Could your fasting regimen make you sick?
- This type of job makes men more virile
- 3D printed hearts could save your life
- Yet another potential benefit of metformin
* This video with Dr. Andrew Huberman of Stanford shows exactly how to do the breathing practice.
This podcast originally aired on March 3, 2023.
Breakthrough drones deliver breast milk in rural Uruguay
Until three months ago, nurse Leopoldina Castelli used to send bottles of breast milk to nourish babies in the remote areas of Tacuarembó, in northern Uruguay, by way of ambulances or military trucks. That is, if the vehicles were available and the roads were passable, which wasn’t always the case. Now, five days per week, she stands by a runway at the hospital, located in Tacuarembó’s capital, watching a drone take off and disappear from view, carrying the milk to clinics that serve the babies’ families.
The drones can fly as far as 62 miles. Long distances and rough roads are no obstacles. The babies, whose mothers struggle to produce sufficient milk and cannot afford formula, now receive ample supplies for healthy growth. “Today we provided nourishment to a significantly larger number of children, and this is something that deeply moves me,” Castelli says.
About two decades ago, the Tacuarembó hospital established its own milk bank, supported by donations from mothers across Tacuarembó. Over the years, the bank has provided milk to infants immediately after birth. It's helped drive a “significant and sustained” decrease in infant mortality, says the hospital director, Ciro Ferreira.
But these children need breast milk throughout their first six months, if not longer, to prevent malnutrition and other illnesses that are prevalent in rural Tacuarembó. Ground transport isn't quick or reliable enough to meet this goal. It can take several hours, during which the milk may spoil due to a lack of refrigeration.
The battery-powered drones have been the difference-maker. The project to develop them, financed by the UNICEF Innovation Fund, is the first of its kind in Latin America. To Castelli, it's nothing short of a revolution. Tacuarembó Hospital, along with three rural clinics in the most impoverished part of Uruguay, are its leaders.
"This marks the first occasion when the public health system has been directly impacted [by our technology]," says Sebastián Macías, the CEO and co-founder of Cielum, an engineer at the University Republic, which collaborated on the technology with a Uruguayan company called Cielum and a Swiss company, Rigitech.
The drone can achieve a top speed of up to 68 miles per hour, is capable of flying in light rain, and can withstand winds of up to 30 miles per hour at a maximum altitude of 120 meters.
"We have succeeded in embracing the mothers from rural areas who were previously slipping through the cracks of the system," says Ferreira, the hospital director. He envisions an expansion of the service so it can improve health for children in other rural areas.
Nurses load the drone for breast milk delivery.
Sebastián Macías - Cielum
The star aircraft
The drone, which costs approximately $70,000, was specifically designed for the transportation of biological materials. Constructed from carbon fiber, it's three meters wide, two meters long and weighs 42 pounds when fully loaded. Additionally, it is equipped with a ballistic parachute to ensure a safe descent in case the technology fails in midair. Furthermore, it can achieve a top speed of 68 miles per hour, fly in light rain, and withstand winds of 30 miles per hour at a height of 120 meters.
Inside, the drones feature three refrigerated compartments that maintain a stable temperature and adhere to the United Nations’ standards for transporting perishable products. These compartments accommodate four gallons or 6.5 pounds of cargo. According to Macías, that's more than sufficient to carry a week’s worth of milk for one infant on just two flights, or 3.3 pounds of blood samples collected in a rural clinic.
“From an energy perspective, it serves as an efficient mode of transportation and helps reduce the carbon emissions associated with using an ambulance,” said Macías. Plus, the ambulance can remain available in the town.
Macías, who has led software development for the drone, and three other technicians have been trained to operate it. They ensure that the drone stays on course, monitor weather conditions and implement emergency changes when needed. The software displays the in-flight positions of the drones in relation to other aircraft. All agricultural planes in the region receive notification about the drone's flight path, departure and arrival times, and current location.
The future: doubling the drone's reach
Forty-five days after its inaugural flight, the drone is now making five flights per week. It serves two routes: 34 miles to Curtina and 31 miles to Tambores. The drone reaches Curtina in 50 minutes while ambulances take double that time, partly due to the subpar road conditions. Pueblo Ansina, located 40 miles from the state capital, will soon be introduced as the third destination.
Overall, the drone’s schedule is expected to become much busier, with plans to accomplish 20 weekly flights by the end of October and over 30 in 2024. Given the drone’s speed, Macías is contemplating using it to transport cancer medications as well.
“When it comes to using drones to save lives, for us, the sky is not the limit," says Ciro Ferreira, Tacuarembó hospital director.
In future trips to clinics in San Gregorio de Polanco and Caraguatá, the drone will be pushed to the limit. At these locations, a battery change will be necessary, but it's worth it. The route will cover up to 10 rural Tacuarembó clinics plus one hospital outside Tacuarembó, in Rivera, close to the border with Brazil. Currently, because of a shortage of ambulances, the delivery of pasteurized breast milk to Rivera only occurs every 15 days.
“The expansion to Rivera will include 100,000 more inhabitants, doubling the healthcare reach,” said Ferreira, the director of the Tacuarembó Hospital. In itself, Ferreira's hospital serves the medical needs of 500,000 people as one of the largest in Uruguay's interior.
Alejandro Del Estal, an aeronautical engineer at Rigitech, traveled from Europe to Tacuarembó to oversee the construction of the vertiports – the defined areas that can support drones’ take-off and landing – and the first flights. He pointed out that once the flight network between hospitals and rural polyclinics is complete in Uruguay, it will rank among the five most extensive drone routes in the world for any activity, including healthcare and commercial uses.
Cielum is already working on the long-term sustainability of the project. The aim is to have more drones operating in other rural regions in the western and northern parts of the country. The company has received inquiries from Argentina and Colombia, but, as Macías pointed out, they are exercising caution when making commitments. Expansion will depend on the development of each country’s regulations for airspace use.
For Ferreira, the advantages in Uruguay are evident: "This approach enables us to bridge the geographical gap, enhance healthcare accessibility, and reduce the time required for diagnosing and treating rural inhabitants, all without the necessity of them traveling to the hospital,” he says. "When it comes to using drones to save lives, for us, the sky is not the limit."