Researchers advance drugs that treat pain without addiction
New therapies are using creative approaches that target the body’s sensory neurons, which send pain signals to the brain.
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.”
Vaccines Without Vaccinations Won’t End the Pandemic
In this 2020 photograph, a bandage is placed on a patient who has just received a vaccine.
COVID-19 vaccine development has advanced at a record-setting pace, thanks to our nation's longstanding support for basic vaccine science coupled with massive public and private sector investments.
Yet, policymakers aren't according anywhere near the same level of priority to investments in the social, behavioral, and data science needed to better understand who and what influences vaccination decision-making. "If we want to be sure vaccines become vaccinations, this is exactly the kind of work that's urgently needed," says Dr. Bruce Gellin, President of Global Immunization at the Sabin Vaccine Institute.
Simply put: it's possible vaccines will remain in refrigerators and not be delivered to the arms of rolled-up sleeves if we don't quickly ramp up vaccine confidence research and broadly disseminate the findings.
According to the most recent Gallup poll, the share of U.S. adults who say they would get a COVID-19 vaccine rose to 58 percent this month from 50 percent in September, with non-white Americans and those ages 45-65 even less willing to be vaccinated. While there is still much we don't understand about COVID-19, we do know that without high levels of immunity in the population, a return to some semblance of normalcy is wishful thinking.
Research from prior vaccination campaigns such as H1N1, HPV, and the annual flu points us in the right direction. Key components of successful vaccination efforts require 1) Identifying the concerns of particular segments of the population; 2) Tailoring messages and incentives to address those concerns, and 3) Reaching out through trusted sources – health care providers, public health departments, and others in the community.
Research during the H1N1 flu found preparing people for some uncertainty actually improved trust, according to Dr. Sandra Crouse Quinn, professor and chair, Family Science, University of Maryland. Dr. Crouse Quinn's research during that period also underscored the need to address the specific vaccine concerns of racial and ethnic groups.
The stunning scientific achievement of COVID-19 vaccines anticipated to be ready in record time needs to be backed up by an equally ambitious and evidence-based effort to build the public's confidence in the vaccines.
Data science has provided crucial insight about the social media universe. Dr. Neil Johnson, a scientist at George Washington University, found that despite having fewer followers, anti-vaccination pages are more numerous and growing faster than pro-vaccination pages. They are more often linked to in discussions on other Facebook pages – such as school parent associations – where people are undecided about vaccination.
We've learned about building vaccine confidence from earlier campaigns. Now, however, we are faced with a unique and challenging set of obstacles to unpack quickly: How do we communicate the importance of eventual COVID-19 vaccines to Americans in light of the muddled-to-poor messaging from political leaders, the weaponizing of relatively simple public health recommendations, the enormous disproportionate toll on people of color, and the torrent of online misinformation? We urgently need data reflective of today's circumstances along with the policy to ensure it is quickly and effectively disseminated to the public health and clinical workforce.
Last year prompted in part by the measles outbreaks, Reps. Michael C. Burgess (R-TX) and Kim Shrier (D-WA), both physicians, introduced the bipartisan Vaccines Act to develop a national surveillance system to monitor vaccination rates and conduct a national campaign to increase awareness of the importance of vaccines. Unfortunately, that legislation wasn't passed. In response to COVID-19, Senate HELP Committee Ranking member Patty Murray (D-WA) has sought funds to strengthen vaccine confidence and combat misinformation with federally supported communication, research, and outreach efforts. Leading experts outside of Congress have called for this type of research, including the Sabin-Aspen Vaccine Science Policy Institute. Most recently, the National Academy of Sciences, in its report regarding the equitable distribution of the COVID-19 vaccine, included as one of its recommendations the need for "a rapid-response program to advance the science behind vaccine confidence."
Addressing trust in vaccination has never been as challenging nor as consequential. The stunning scientific achievement of COVID-19 vaccines anticipated to be ready in record time needs to be backed up by an equally ambitious and evidence-based effort to build the public's confidence in the vaccines. In its remaining days, the Trump Administration should invest in building vaccine confidence with current resources, targeting efforts to ensure COVID vaccines reduce rather than exacerbate racial and ethnic health disparities. Congress must also act to provide the additional research and outreach resources needed as well as pass the Vaccines Act so we are better prepared in the future.
If we don't succeed, COVID-19 will continue wreaking havoc on our health, our society, and our economy. We will also permanently jeopardize public trust in vaccines – one of the most successful medical interventions in human history.
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Kira Peikoff was the editor-in-chief of Leaps.org from 2017 to 2021. As a journalist, her work has appeared in The New York Times, Newsweek, Nautilus, Popular Mechanics, The New York Academy of Sciences, and other outlets. She is also the author of four suspense novels that explore controversial issues arising from scientific innovation: Living Proof, No Time to Die, Die Again Tomorrow, and Mother Knows Best. Peikoff holds a B.A. in Journalism from New York University and an M.S. in Bioethics from Columbia University. She lives in New Jersey with her husband and two young sons. Follow her on Twitter @KiraPeikoff.