It's been more than a decade since Jeannette Rotondi has been pain-free. A licensed social worker, she lives with five chronic pain diagnoses, including migraines. After years of exploring treatment options, doctors found one that lessened the pain enough to allow her to "at least get up."
"With all that we know now about genetics and the immune system, I think the future of pain medicine is more precision-based."
Before she says, "It was completely debilitating. I was spending time in dark rooms. I got laid off from my job." Doctors advised against pregnancy; she and her husband put off starting a family for almost a decade.
"Chronic pain is very unpredictable," she says. "You cannot schedule when you'll be in debilitative pain or cannot function. You don't know when you'll be hit with a flare. It's constantly in your mind. You have to plan for every possibly scenario. You need to carry water, medications. But you can't plan for everything." Even odors can serve as a trigger.
According to the CDC, one fifth of American adults live with chronic pain, and women are affected more than men. Do men and women simply vary in how much pain they can handle? Or is there some deeper biological explanation? The short answer is it's a little of both. But understanding the biological differences can enable researchers to develop more effective treatments.
While studies in animals are straightforward (they either respond to pain or they don't), humans are more complex. Social and psychological factors can affect the outcome. For example, one Florida study found that gender role expectations influenced pain sensitivity.
"If you are a young male and you believe very strongly that men are tougher than women, you will have a much higher threshold and will be less sensitive to pain," says Robert Sorge, an associate professor at the University of Alabama at Birmingham whose lab researches the immune system's involvement in pain and addiction.
He also notes, "We looked at transgender women and their pain sensitivity in comparison to cis men and women. They show very similar pain sensitivity to cis women, so that may reduce the impact of genetic sex in terms of what underlies that sensitivity."
But the difference goes deeper than gender expectations. There are biological differences as well. In 2015, Sorge and his team discovered that pain stimuli activated different immune cells in male and female rodents and that the presence of testosterone seemed to be a factor in the response.
More recently, Ted Price, professor of neuroscience at University of Texas, Dallas, examined pain at a genetic level, specifically looking at the patterns of RNA, which are single-stranded molecules that act as a messenger for DNA. Price noted that there were differences in these patterns that coincided with whether an individual experienced pain.
Price explains, "Every cell in your body has DNA, but the RNA that is in the cells is different for every cell type. The RNA in any particular cell type, like a neuron, can change as a result of some environmental influence like an injury. We found a number of genes that are potentially causative factors for neuropathic pain. Those, interestingly, seemed to be different between men and women."
Differences in treatment also affect pain response. Sorge says, "Women are experiencing more pain dismissal and more hostility when they report chronic pain. Women are more likely to have their pain associated with psychological issues." He adds that this dismissal may require women to exaggerate symptoms in order to be believed.
This can impact pain management. "Women are more likely to be prescribed and to use opioids," says Dr. Roger B. Fillingim, Director of Pain Research and Intervention Center of Excellence at the University of Florida. Yet, when self-administering pain meds, "women used significantly less opioids after surgery than did men." He also points out that "men are at greater risk for dose escalation and for opioid-related death than are women. So even though more women are using opioids, men are more likely to die from opioid-related causes."
Price acknowledges that other drugs treat pain, but "unfortunately, for chronic pain, none of these drugs work very well. We haven't yet made classes of drugs that really target the underlying mechanism that causes people to have chronic pain."
New drugs are now being developed that "might be particularly efficacious in women's chronic pain."
Sorge points out that there are many variables in pain conditions, so drugs that work for one may be ineffective for another. "With all that we know now about genetics and the immune system, I think the future of pain medicine is more precision-based, where based on your genetics, your immune status, your history, we may eventually get to the point where we can say [certain] drugs have a much bigger chance of working for you."
It will take some time for these new discoveries to translate into effective treatments, but Price says, "I'm excited about the opportunities. DNA and RNA sequencing totally changes our ability to make these therapeutics. I'm very hopeful." New drugs are now being developed that "might be particularly efficacious in women's chronic pain," he says, because they target specific receptors that seem to be involved when only women experience pain.
Earlier this year, three such drugs were approved to treat migraines; Rotondi recently began taking one. For Rotondi, improved treatments would allow her to "show up for life. For me," she says, "it would mean freedom."
In November 2020, messenger RNA catapulted into the public consciousness when the first COVID-19 vaccines were authorized for emergency use. Around the same time, an equally groundbreaking yet relatively unheralded application of mRNA technology was taking place at a London hospital.
Over the past two decades, there's been increasing interest in harnessing mRNA — molecules present in all of our cells that act like digital tape recorders, copying instructions from DNA in the cell nucleus and carrying them to the protein-making structures — to create a whole new class of therapeutics.
Scientists realized that artificial mRNA, designed in the lab, could be used to instruct our cells to produce certain antibodies, turning our bodies into vaccine-making factories, or to recognize and attack tumors. More recently, researchers recognized that mRNA could also be used to make another groundbreaking technology far more accessible to more patients: gene editing. The gene-editing tool CRISPR has generated plenty of hype for its potential to cure inherited diseases. But delivering CRISPR to the body is complicated and costly.
"Most gene editing involves taking cells out of the patient, treating them and then giving them back, which is an extremely expensive process," explains Drew Weissman, professor of medicine at the University of Pennsylvania, who was involved in developing the mRNA technology behind the COVID-19 vaccines.
But last November, a Massachusetts-based biotech company called Intellia Therapeutics showed it was possible to use mRNA to make the CRISPR system inside the body, eliminating the need to extract cells out of the body and edit them in a lab. Just as mRNA can instruct our cells to produce antibodies against a viral infection, it can also teach them to produce the two molecular components that make up CRISPR — a guide molecule and a cutting protein — to snip out a problem gene.
"The pandemic has really shown that not only are mRNA approaches viable, they could in certain circumstances be vastly superior to more traditional technologies."
In Intellia's London-based clinical trial, the company applied this for the first time in a patient with a rare inherited liver disease known as hereditary transthyretin amyloidosis with polyneuropathy. The disease causes a toxic protein to build up in a person's organs and is typically fatal. In a company press release, Intellia's president and CEO John Leonard swiftly declared that its mRNA-based CRISPR therapy could usher in a "new era of potential genome editing cures."
Weissman predicts that turning CRISPR into an affordable therapy will become the next major frontier for mRNA over the coming decade. His lab is currently working on an mRNA-based CRISPR treatment for sickle cell disease. More than 300,000 babies are born with sickle cell every year, mainly in lower income nations.
"There is a FDA-approved cure, but it involves taking the bone marrow out of the person, and then giving it back which is prohibitively expensive," he says. It also requires a patient to have a matched bone marrow done. "We give an intravenous injection of mRNA lipid nanoparticles that target CRISPR to the bone marrow stem cells in the patient, which is easy, and much less expensive."
Meanwhile, the overwhelming success of the COVID-19 vaccines has focused attention on other ways of using mRNA to bolster the immune system against threats ranging from other infectious diseases to cancer.
The practicality of mRNA vaccines – relatively small quantities are required to induce an antibody response – coupled with their adaptable design, mean companies like Moderna are now targeting pathogens like Zika, chikungunya and cytomegalovirus, or CMV, which previously considered commercially unviable for vaccine developers. This is because outbreaks have been relatively sporadic, and these viruses mainly affect people in low-income nations who can't afford to pay premium prices for a vaccine. But mRNA technology means that jabs could be produced on a flexible basis, when required, at relatively low cost.
Other scientists suggest that mRNA could even provide a means of developing a universal influenza vaccine, a goal that's long been the Holy Grail for vaccinologists around the world.
"The mRNA technology allows you to pick out bits of the virus that you want to induce immunity to," says Michael Mulqueen, vice president of business development at eTheRNA, a Belgium-based biotech that's developing mRNA-based vaccines for malaria and HIV, as well as various forms of cancer. "This means you can get the immune system primed to the bits of the virus that don't vary so much between strains. So you could actually have a single vaccine that protects against a whole raft of different variants of the same virus, offering more universal coverage."
Before mRNA became synonymous with vaccines, its biggest potential was for cancer treatments. BioNTech, the German biotech company that collaborated with Pfizer to develop the first authorized COVID-19 vaccine, was initially founded to utilize mRNA for personalized cancer treatments, and the company remains interested in cancers ranging from melanoma to breast cancer.
One of the major hurdles in treating cancer has been the fact that tumors can look very different from one person to the next. It's why conventional approaches, such as chemotherapy or radiation, don't work for every patient. But weaponizing mRNA against cancer primes the immune cells with the tumor's specific genetic sequence, training the patient's body to attack their own unique type of cancer.
"It means you're able to think about personalizing cancer treatments down to specific subgroups of patients," says Mulqueen. "For example, eTheRNA are developing a renal cell carcinoma treatment which will be targeted at around 20% of these patients, who have specific tumor types. We're hoping to take that to human trials next year, but the challenge is trying to identify the right patients for the treatment at an early stage."
Repairing Damaged mRNA
While hopes are high that mRNA could usher in new cancer treatments and make CRISPR more accessible, a growing number of companies are also exploring an alternative to gene editing, known as RNA editing.
In genetic disorders, the mRNA in certain cells is impaired due to a rogue gene defect, and so the body ceases to produce a particular vital protein. Instead of permanently deleting the problem gene with CRISPR, the idea behind RNA editing is to inject small pieces of synthetic mRNA to repair the existing mRNA. Scientists think this approach will allow normal protein production to resume.
Over the past few years, this approach has gathered momentum, as some researchers have recognized that it holds certain key advantages over CRISPR. Companies from Belgium to Japan are now looking at RNA editing to treat all kinds of disorders, from Huntingdon's disease, to amyotrophic lateral sclerosis, or ALS, and certain types of cancer.
"With RNA editing, you don't need to make any changes to the DNA," explains Daniel de Boer, CEO of Dutch biotech ProQR, which is looking to treat rare genetic disorders that cause blindness. "Changes to the DNA are permanent, so if something goes wrong, that may not be desirable. With RNA editing, it's a temporary change, so we dose patients with our drugs once or twice a year."
Last month, ProQR reported a landmark case study, in which a patient with a rare form of blindness called Leber congenital amaurosis, which affects the retina at the back of the eye, recovered vision after three months of treatment.
"We have seen that this RNA therapy restores vision in people that were completely blind for a year or so," says de Boer. "They were able to see again, to read again. We think there are a large number of other genetic diseases we could go after with this technology. There are thousands of different mutations that can lead to blindness, and we think this technology can target approximately 25% of them."
Ultimately, there's likely to be a role for both RNA editing and CRISPR, depending on the disease. "I think CRISPR is ideally suited for illnesses where you would like to permanently correct a genetic defect," says Joshua Rosenthal of the Marine Biology Laboratory in Chicago. "Whereas RNA editing could be used to treat things like pain, where you might want to reset a neural circuit temporarily over a shorter period of time."
Much of this research has been accelerated by the COVID-19 pandemic, which has played a major role in bringing mRNA to the forefront of people's minds as a therapeutic.
"The pandemic has really shown that not only are mRNA approaches viable, they could in certain circumstances be vastly superior to more traditional technologies," says Mulqueen. "In the future, I would not be surprised if many of the top pharma products are mRNA derived."
"Making Sense of Science" is a monthly podcast that features interviews with leading medical and scientific experts about the latest developments and the big ethical and societal questions they raise. This episode is hosted by science and biotech journalist Emily Mullin, summer editor of the award-winning science outlet Leaps.org.