Researchers advance drugs that treat pain without addiction
Opioids are one of the most common ways to treat pain. They can be effective but are also highly addictive, an issue that has fueled the ongoing opioid crisis. In 2020, an estimated 2.3 million Americans were dependent on prescription opioids.
Opioids bind to receptors at the end of nerve cells in the brain and body to prevent pain signals. In the process, they trigger endorphins, so the brain constantly craves more. There is a huge risk of addiction in patients using opioids for chronic long-term pain. Even patients using the drugs for acute short-term pain can become dependent on them.
Scientists have been looking for non-addictive drugs to target pain for over 30 years, but their attempts have been largely ineffective. “We desperately need alternatives for pain management,” says Stephen E. Nadeau, a professor of neurology at the University of Florida.
A “dimmer switch” for pain
Paul Blum is a professor of biological sciences at the University of Nebraska. He and his team at Neurocarrus have created a drug called N-001 for acute short-term pain. N-001 is made up of specially engineered bacterial proteins that target the body’s sensory neurons, which send pain signals to the brain. The proteins in N-001 turn down pain signals, but they’re too large to cross the blood-brain barrier, so they don’t trigger the release of endorphins. There is no chance of addiction.
When sensory neurons detect pain, they become overactive and send pain signals to the brain. “We wanted a way to tone down sensory neurons but not turn them off completely,” Blum reveals. The proteins in N-001 act “like a dimmer switch, and that's key because pain is sensation overstimulated.”
Blum spent six years developing the drug. He finally managed to identify two proteins that form what’s called a C2C complex that changes the structure of a subunit of axons, the parts of neurons that transmit electrical signals of pain. Changing the structure reduces pain signaling.
“It will be a long path to get to a successful clinical trial in humans," says Stephen E. Nadeau, professor of neurology at the University of Florida. "But it presents a very novel approach to pain reduction.”
Blum is currently focusing on pain after knee and ankle surgery. Typically, patients are treated with anesthetics for a short time after surgery. But anesthetics usually only last for 4 to 6 hours, and long-term use is toxic. For some, the pain subsides. Others continue to suffer after the anesthetics have worn off and start taking opioids.
N-001 numbs sensation. It lasts for up to 7 days, much longer than any anesthetic. “Our goal is to prolong the time before patients have to start opioids,” Blum says. “The hope is that they can switch from an anesthetic to our drug and thereby decrease the likelihood they're going to take the opioid in the first place.”
Their latest animal trial showed promising results. In mice, N-001 reduced pain-like behaviour by 90 percent compared to the control group. One dose became effective in two hours and lasted a week. A high dose had pain-relieving effects similar to an opioid.
Professor Stephen P. Cohen, director of pain operations at John Hopkins, believes the Neurocarrus approach has potential but highlights the need to go beyond animal testing. “While I think it's promising, it's an uphill battle,” he says. “They have shown some efficacy comparable to opioids, but animal studies don't translate well to people.”
Nadeau, the University of Florida neurologist, agrees. “It will be a long path to get to a successful clinical trial in humans. But it presents a very novel approach to pain reduction.”
Blum is now awaiting approval for phase I clinical trials for acute pain. He also hopes to start testing the drug's effect on chronic pain.
Learning from people who feel no pain
Like Blum, a pharmaceutical company called Vertex is focusing on treating acute pain after surgery. But they’re doing this in a different way, by targeting a sodium channel that plays a critical role in transmitting pain signals.
In 2004, Stephen Waxman, a neurology professor at Yale, led a search for genetic pain anomalies and found that biologically related people who felt no pain despite fractures, burns and even childbirth had mutations in the Nav1.7 sodium channel. Further studies in other families who experienced no pain showed similar mutations in the Nav1.8 sodium channel.
Scientists set out to modify these channels. Many unsuccessful efforts followed, but Vertex has now developed VX-548, a medicine to inhibit Nav1.8. Typically, sodium ions flow through sodium channels to generate rapid changes in voltage which create electrical pulses. When pain is detected, these pulses in the Nav1.8 channel transmit pain signals. VX-548 uses small molecules to inhibit the channel from opening. This blocks the flow of sodium ions and the pain signal. Because Nav1.8 operates only in peripheral nerves, located outside the brain, VX-548 can relieve pain without any risk of addiction.
"Frankly we need drugs for chronic pain more than acute pain," says Waxman.
The team just finished phase II clinical trials for patients following abdominoplasty surgery and bunionectomy surgery.
After abdominoplasty surgery, 76 patients were treated with a high dose of VX-548. Researchers then measured its effectiveness in reducing pain over 48 hours, using the SPID48 scale, in which higher scores are desirable. The score for Vertex’s drug was 110.5 compared to 72.7 in the placebo group, whereas the score for patients taking an opioid was 85.2. The study involving bunionectomy surgery showed positive results as well.
Waxman, who has been at the forefront of studies into Nav1.7 and Nav1.8, believes that Vertex's results are promising, though he highlights the need for further clinical trials.
“Blocking Nav1.8 is an attractive target,” he says. “[Vertex is] studying pain that is relatively simple and uniform, and that's key to having a drug trial that is informative. But the study needs to be replicated and frankly we need drugs for chronic pain more than acute pain. If this is borne out by additional studies, it's one important step in a journey.”
Vertex will be launching phase III trials later this year.
Finding just the right amount of Nerve Growth Factor
Whereas Neurocarrus and Vertex are targeting short-term pain, a company called Levicept is concentrating on relieving chronic osteoarthritis pain. Around 32.5 million Americans suffer from osteoarthritis. Patients commonly take NSAIDs, or non-steroidal anti-inflammatory drugs, but they cannot be taken long-term. Some take opioids but they aren't very effective.
Levicept’s drug, Levi-04, is designed to modify a signaling pathway associated with pain. Nerve Growth Factor (NGF) is a neurotrophin: it’s involved in nerve growth and function. NGF signals by attaching to receptors. In pain there are excess neurotrophins attaching to receptors and activating pain signals.
“What Levi-04 does is it returns the natural equilibrium of neurotrophins,” says Simon Westbrook, the CEO and founder of Levicept. It stabilizes excess neurotrophins so that the NGF pathway does not signal pain. Levi-04 isn't addictive since it works within joints and in nerves outside the brain.
Westbrook was initially involved in creating an anti-NGF molecule for Pfizer called Tanezumab. At first, Tanezumab seemed effective in clinical trials and other companies even started developing their own versions. However, a problem emerged. Tanezumab caused rapidly progressive osteoarthritis, or RPOA, in some patients because it completely removed NGF from the system. NGF is not just involved in pain signalling, it’s also involved in bone growth and maintenance.
Levicept has found a way to modify the NGF pathway without completely removing NGF. They have now finished a small-scale phase I trial mainly designed to test safety rather than efficacy. “We demonstrated that Levi-04 is safe and that it bound to its target, NGF,” says Westbrook. It has not caused RPOA.
Professor Philip Conaghan, director of the Leeds Institute of Rheumatic and Musculoskeletal Medicine, believes that Levi-04 has potential but urges the need for caution. “At this early stage of development, their molecule looks promising for osteoarthritis pain,” he says. “They will have to watch out for RPOA which is a potential problem.”
Westbrook starts phase II trials with 500 patients this summer to check for potential side effects and test the drug’s efficacy.
There is a real push to find an effective alternative to opioids. “We have a lot of work to do,” says Professor Waxman. “But I am confident that we will be able to develop new, much more effective pain therapies.”
Your surgery could harm yourself and the planet. Here's what some doctors are doing about it.
This is part 1 of a three part series on a new generation of doctors leading the charge to make the health care industry more sustainable - for the benefit of their patients and the planet. Read part 2 here and part 3 here.
Susanne Koch, an anesthesiologist and neurologist, reached a pivot point when she was up to her neck in water, almost literally. The basement of her house in Berlin had flooded in the summer of 2018, when Berlin was pummeled by unusually strong rains. After she drained the house, “I wanted to dig into facts, to understand how exactly these extreme weather events are related to climate change,” she says.
Studying the scientific literature, she realized how urgent the climate crisis is, but the biggest shock was to learn that her profession contributed substantially to the problem: Inhalation gases used during medical procedures are among the most damaging greenhouse gases. Some inhalation gases are 3,000 times more damaging for the climate than CO2, Koch discovered. “Spending seven hours in the surgery room is the equivalent of driving a car for four days nonstop,” she says. Her job of helping people at Europe’s largest university hospital, the Charité in Berlin, was inadvertently damaging both the people and the planet.
“Nobody had ever even mentioned a word about that during my training,” Koch says.
On the whole, the medical sector is responsible for a disproportionally large percentage of greenhouse gas emissions, with the U.S. as the biggest culprit. According to a key paper published in 2020 in Health Affairs, the health industry “is among the most carbon-intensive service sectors in the industrialized world,” accounting for between 4.4 percent and 4.6 percent of greenhouse gas emissions. “It’s not just anesthesia but health care that has a problem,” says Jodi Sherman, anesthesiology professor and Medical Director of the Program on Healthcare Environmental Sustainability at Yale University as well as co-director of the Lancet Planetary Health Commission on Sustainable Healthcare. In the U.S., health care greenhouse gas emissions make up about 8.5 percent of domestic greenhouse gas emissions. They rose 6 percent from 2010 to 2018, to nearly 1,700 kilograms per person, more than in any other nation.
Of course, patients worry primarily about safety, not sustainability. Yet, Koch emphasizes that “as doctors, we have the responsibility to do no harm, and this includes making sure that we use resources as sustainably as possible.” Studies show that 2018 greenhouse gas and toxic air pollutant emissions resulted in the loss of 388,000 disability-adjusted life years in the U.S. alone. “Disease burden from health care pollution is of the same order of magnitude as deaths from preventable medical errors, and should be taken just as seriously,” Sherman cautions.
When Koch, the anesthesiologist, started discussing sustainable options with colleagues, the topic was immediately met with plenty of interest. Her experience is consistent with the latest representative poll of the nonprofit Foundation Health in Germany. Nine out of ten doctors were interested in urgently finding sustainable solutions for medical services but lacked knowhow and resources. For teaching purposes, Sherman and her team have developed the Yale Gassing Greener app that allows anesthesiologists to compare how much pollution they can avoid through choosing different anesthesia methods. Sherman also published professional guidelines intended to help her colleagues better understand how various methods affect carbon emissions.
Significant traces of inhalation gases have been found in Antarctica and the Himalayas, far from the vast majority of surgery rooms.
A solution espoused by both Sherman and Koch is comparatively simple: They stopped using desflurane, which is by far the most damaging of all inhalation gases to the climate. Its greenhouse effect is 2,590 times stronger than carbon dioxide. The Yale New Haven Hospital already stopped using desflurane in 2013, becoming the first known healthcare organization to eliminate a drug based on environmental grounds. Sherman points out that this resulted in saving more than $1.2 million in costs and 1,600 tons of CO2 equivalents, about the same as the exhaust from 360 passenger vehicles per year.
At the Charité, Koch claims that switching to other anesthesiology choices, such as propofol, has eliminated 90 percent of the climate gas emissions in the anesthesiology department since 2016. Young anesthesiologists are still taught to use desflurane as the standard because desflurane is absorbed less into the patients’ bodies, and they wake up faster. However, Koch who has worked as an anesthesiologist since 2006, says that with a little bit of experience, you can learn when to stop giving the propofol so it's timed just as well with a person’s wake-up process. In addition, “patients are less likely to feel nauseous after being given propofol,” Koch says. Intravenous drugs might require more skill, she adds, "but there is nothing unique to the drug desflurane that cannot be accomplished with other medications.”
Desflurane isn’t the only gas to be concerned about. Nitrous oxide is the second most damaging because it’s extremely long-lived in the environment, and it depletes the ozone layer. Climate-conscious anesthesiologists are phasing out this gas, too, or have implemented measures to decrease leaks.
Internationally, 192 governments agreed in the Kyoto protocol of 2005 to reduce halogenated hydrocarbons – resulting from inhalation gases, including desflurane and nitrous oxide – because of their immense climate-warming potential, and in 2016, they pledged to eliminate them by 2035. However, the use of inhalation anesthetics continues to increase worldwide, not least because more people access healthcare in developing countries, and because people in industrialized countries live longer and therefore need more surgeries. Significant traces of inhalation gases have been found in Antarctica and the Himalayas, far from the vast majority of surgery rooms.
Certain companies are now pushing new technology to capture inhalation gases before they are released into the atmosphere, but both Sherman and Koch believe marketing claims of 99 percent efficiency amount to greenwashing. After investigating the technology first-hand and visiting the company that is producing such filters in Germany, Koch concluded that such technology only reduces emissions by 25 percent. And Sherman believes such initiatives are akin to the fallacy of recycling plastic. In addition to questioning their efficiency, Sherman fears such technology “gives the illusion there is a magical solution that means I don’t need to change my behavior, reduce my waste and choose less harmful options.”
Financial interests are at play, too. “Desflurane is the most expensive inhalation gas, and some think, the most expensive must be the best,” Koch says. Both Koch and Sherman lament that efforts to increase sustainability in the medical sector are entirely voluntary in their countries and led by a few dedicated individual professionals while industry-wide standards and transparency are needed, a notion expressed in the American Hospital Association’s Sustainability Roadmap.
Susanne Koch, an anesthesiologist in Berlin, wants her colleagues to stop using a gas called desflurane, which is by far the most damaging of all inhalation gases to the climate.
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Other countries have done more. The European Union recommends reducing inhalation gases and even contemplated a ban of desflurane, except in medical emergencies. In 2008, the National Health Service (NHS) created a Sustainable Development Unit, which measures CO2 emissions in the U.K. health sector. NHS is the first national health service that pledged to reach net zero carbon by 2040. The carbon footprint of the NHS fell by 26 percent from 1990 to 2019, mostly due to reduced use of certain inhalers and the switch to renewable energy for heat and power. “The evidence that the climate emergency is a health emergency is overwhelming,” said Nick Watts, the NHS Chief Sustainability Officer, in a press release, “with health professionals already needing to manage its symptoms.”
Sherman is a leading voice in demanding action in the U.S. To her, comprehensive solutions start with the mandatory, transparent measurement of emissions in the health sector to tackle the biggest sources of pollution. While the Biden administration highlighted its efforts to reduce these kinds of emissions during the United Nations Climate Conference (COP27) in November 2022 and U.S. delegates announced that more than 100 health care organizations signed the voluntary Health Sector Climate Pledge, with the aim to reduce emissions by 50 percent in the next eight years, Sherman is convinced that voluntary pledges are not enough. “Voluntary measures are insufficient,” she testified in congress. “The vast majority of U.S. health care organizations remain uncommitted to timely action. Those that are committed lack policies and knowledge to support necessary changes; even worse, existing policies drive inappropriate consumption of resources and pollution.”
Both Sherman and Koch look at the larger picture. “Health care organizations have an obligation to their communities to protect public health,” Sherman says. “We must lead by example. That includes setting ambitious, science-based carbon reduction targets to achieve net zero emissions before 2050. We must quantify current emissions and their sources, particularly throughout the health care supply chains.”
Have You Heard of the Best Sport for Brain Health?
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.
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Here are the promising studies covered in this week's Friday Five:
- Reprogram cells to a younger state
- Pick up this sport for brain health
- Do all mental illnesses have the same underlying cause?
- New test could diagnose autism in newborns
- Scientists 3D print an ear and attach it to woman