New drug for schizophrenia could meet desperate need for better treatments
Schizophrenia is a debilitating mental health condition that affects around 24 million people worldwide. Patients experience hallucinations and delusions when they develop schizophrenia, with experts referring to these new thoughts and behaviors as positive symptoms. They also suffer from negative symptoms in which they lose important functions, suffering from dulled emotions, lack of purpose and social withdrawal.
Currently available drugs can control only a portion of these symptoms but, on August 8th, Karuna Therapeutics announced its completion of a phase 3 clinical trial that found a new drug called KarXT could treat both positive and negative symptoms of schizophrenia. It could mean substantial progress against a problem that has stymied scientists for decades.
A long-standing problem
Since the 1950s, antipsychotics have been used to treat schizophrenia. People who suffer from it are thought to have too much of a brain chemical called dopamine, and antipsychotics work by blocking dopamine receptors in the brain. They can be effective in treating positive symptoms but have little impact on the negative ones, which can be devastating for a patient’s quality of life, making it difficult to maintain employment and have successful relationships. About 30 percent of schizophrenia patients don't actually respond to antipsychotics at all. Current drugs can also have adverse side effects including elevated cholesterol, high blood pressure, diabetes and movements that patients cannot control.
The recent clinical trial heralds a new treatment approach. “We believe it marks an important advancement for patients given its new and completely different mechanism of action from current therapies,” says Andrew Miller, COO of Karuna.
Scientists have been looking to develop alternatives. However, “the field of drug treatment of schizophrenia is currently in the doldrums,” says Peter McKenna, a senior researcher at FIDMAG Research Foundation in Spain which specialises in mental health.
In the 2000s there was a major push to target a brain receptor for a chemical called glutamate. Evidence suggested that this receptor is abnormal in the brains of schizophrenia patients, but attempts to try glutamate failed in clinical trials.
After that, many pharmaceutical companies dropped out of the race for a more useful treatment. But some companies continued to search, such as Karuna Therapeutics, led by founder and Chief Operating Officer Andrew Miller and CEO Steve Paul. The recent clinical trial suggests their persistence has led to an important breakthrough with their drug, KarXT. “We believe it marks an important advancement for patients given its new and completely different mechanism of action from current therapies,” Miller says.
How it works
Neurotransmitters are chemical messengers that pass signals between neurons. To work effectively, neurotransmitters need a receptor to bind to. A neurotransmitter called acetylcholine seems to be especially important in schizophrenia. It interacts with sites called muscarinic receptors, which are involved in the network of nerves that calm your body after a stressful event. Post mortem studies in people with schizophrenia have shown that two muscarinic receptors in the brain, the M1 and M4 receptors, are activated at unusually low levels because they don’t receive enough signals from acetylcholine.
The M4 receptor appears to play a role in psychosis. The M1 receptor is also associated with psychosis but is primarily thought to be involved in cognition. KarXT, taken orally, works by activating both of these receptors to signal properly. It is this twofold action that seems to explain its effectiveness. “[The drug’s] design enables the preferential stimulation of these muscarinic receptors in the brain,” Miller says.
How it developed
It all started in the early 1990s when Paul was at pharmaceutical company Eli Lilly. He discovered that Xanomeline, the drug they were testing on Alzheimer's patients, had antipsychotic effects. It worked by stimulating M1 and M4 receptors, so he and his colleagues decided to test Xanomeline on schizophrenia patients, supported by research on the connection between muscarinic receptors and psychosis. They found that Xanomeline reduced both positive and negative symptoms.
Unfortunately, it also caused significant side effects. The problem was that stimulating the M1 and M4 receptors in the brain also stimulated muscarinic receptors in the body that led to severe vomiting, diarrhea and even the temporary loss of consciousness.
In the end, Eli Lilly discontinued the clinical trials for the drug, but Miller set up Karuna Therapeutics to develop a solution. “I was determined to find a way to harness the therapeutic benefit demonstrated in studies of Xanomeline, while eliminating side effects that limited its development,” Miller says.
He analysed over 7,000 possible ways of mixing Xanomeline with other agents before settling on KarXT. It combines Xanomeline with a drug called Trospium Chloride, which blocks muscarinic receptors in the body – taking care of the side effects such as vomiting – but leaves them unblocked in the brain. Paul was so excited by Miller’s progress that he joined Karuna after leaving Eli Lilly and founding two previous startups.
“It's a very important approach,” says Rick Adams, Future Leaders Fellow in the Institute of Cognitive Neuroscience and Centre for Medical Image Computing at University College London. “We are in desperate need of alternative drug targets and this target is one of the best. There are other alternative targets, but not many are as close to being successful as the muscarinic receptor drug.”
Clinical Trial
Following a successful phase 2 clinical trial in 2019, the most recent trial involved 126 patients who were given KarXT, and 126 who were given a placebo. Compared to the placebo, patients taking KarXT had a significant 9.6 point reduction in the positive and negative syndrome scale (PANSS), the standard for rating schizophrenic symptoms.
KarXT also led to statistically significant declines in positive and negative symptoms compared to the placebo. “The results suggest that KarXT could be a potentially game-changing option in the management of both positive and negative symptoms of schizophrenia,” Miller says.
Robert McCutcheon, a psychiatrist and neuroscientist at Oxford University, is optimistic about the side effects but highlights the need for more safety trials.
McKenna, the researcher at FIDMAG Foundation, agrees about the drug’s potential. “The new [phase 3] study is positive,” he says. “It is reassuring that one is not dealing with a drug that works in one trial and then inexplicably fails in the next one.”
Robert McCutcheon, a psychiatrist and neuroscientist at Oxford University, said the drug is an unprecedented step forward. “KarXT is one of the first drugs with a novel mechanism of action to show promise in clinical trials.”
Even though the drug blocks muscarine receptors in the body, some patients still suffered from adverse side effects like vomiting, dizziness and diarrhea. But in general, these effects were mild to moderate, especially compared to dopamine-blocking antipsychotics or Xanomeline on its own.
McCutcheon is optimistic about the side effects but highlights the need for more safety trials. “The trial results suggest that gastrointestinal side effects appear to be manageable,” he says. “We know, however, from previous antipsychotic drugs that the full picture regarding the extent of side effects can sometimes take longer to become apparent to clinicians and patients. Careful ongoing assessment during a longer period of treatment will therefore be important.”
The Future
The team is currently conducting three other trials to evaluate the efficacy and long-term safety of KarXT. Their goal is to receive FDA approval next year.
Karuna is also conducting trials to evaluate the effectiveness of KarXT in treating psychosis in patients suffering from Alzheimer’s.
The big hope is that they will soon be able to provide a radically different drug to help many patients with schizophrenia. “We are another step closer to potentially providing the first new class of medicine in more than 50 years to the millions of people worldwide living with schizophrenia,” says Miller.
Black Participants Are Sorely Absent from Medical Research
After years of suffering from mysterious symptoms, my mother Janice Thomas finally found a doctor who correctly diagnosed her with two autoimmune diseases, Lupus and Sjogren's. Both diseases are more prevalent in the black population than in other races and are often misdiagnosed.
The National Institutes of Health has found that minorities make up less than 10 percent of trial participants.
Like many chronic health conditions, a lack of understanding persists about their causes, individual manifestations, and best treatment strategies.
On the search for relief from chronic pain, my mother started researching options and decided to participate in clinical trials as a way to gain much-needed insights. In return, she received discounted medical testing and has played an active role in finding answers for all.
"When my doctor told me I could get financial or medical benefits from participating in clinical trials for the same test I was already doing, I figured it would be an easy way to get some answers at little to no cost," she says.
As a person of color, her presence in clinical studies is rare. The National Institutes of Health has found that minorities make up less than 10 percent of trial participants.
Without trial participation that is reflective of the general population, pharmaceutical companies and medical professionals are left guessing how various drugs work across racial lines. For example, albuterol, a widely used asthma treatment, was found to have decreased effectiveness for black American and Puerto Rican children. Many high mortality conditions, like cancer, also show different outcomes based on race.
Over the last decade, the pervasive lack of representation has left communities of color demanding higher levels of involvement in the research process. However, no consensus yet exists on how best to achieve this.
But experts suggest that before we can improve black participation in medical studies, key misconceptions must be addressed, such as the false assumption that such patients are unwilling to participate because they distrust scientists.
Jill A. Fisher, a professor in the Center for Bioethics at the University of North Carolina at Chapel Hill, learned in one study that mistrust wasn't the main barrier for black Americans. "There is a lot of evidence that researchers' recruitment of black Americans is generally poorly done, with many black patients simply not asked," Fisher says. "Moreover, the underrepresentation of black Americans is primarily true for efficacy trials - those testing whether an investigational drug might therapeutically benefit patients with specific illnesses."
Without increased minority participation, research will not accurately reflect the diversity of the general population.
Dr. Joyce Balls-Berry, a psychiatric epidemiologist and health educator, agrees that black Americans are often overlooked in the process. One study she conducted found that "enrollment of minorities in clinical trials meant using a variety of culturally appropriate strategies to engage participants," she explained.
To overcome this hurdle, The National Black Church Initiative (NBCI), a faith-based organization made up of 34,000 churches and over 15.7 million African Americans, last year urged the Food and Drug Administration to mandate diversity in all clinical trials before approving a drug or device. However, the FDA declined to implement the mandate, declaring that they don't have the authority to regulate diversity in clinical trials.
"African Americans have not been successfully incorporated into the advancement of medicine and research technologies as legitimate and natural born citizens of this country," admonishes NBCI's president Rev. Anthony Evans.
His words conjure a reminder of the medical system's insidious history for people of color. The most infamous incident is the Tuskegee syphilis scandal, in which white government doctors perpetrated harmful experiments on hundreds of unsuspecting black men for forty years, until the research was shut down in the early 1970s.
Today, in the second decade of twenty-first century, the pernicious narrative that blacks are outsiders in science and medicine must be challenged, says Dr. Danielle N. Lee, assistant professor of biological sciences at Southern Illinois University. And having majority white participants in clinical trials only furthers the notion that "whiteness" is the default.
According to Lee, black individuals often see themselves disconnected from scientific and medical processes. "One of the critiques with science and medical research is that communities of color, and black communities in particular, regard ourselves as outsiders of science," Lee says. "We are othered."
Without increased minority participation, research will not accurately reflect the diversity of the general population.
"We are all human, but we are different, and yes, even different populations of people require modified medical responses," she points out.
Another obstacle is that many trials have health requirements that exclude black Americans, like not wanting individuals who have high blood pressure or a history of stroke. Considering that this group faces health disparities at a higher rate than whites, this eliminates eligibility for millions of potential participants.
One way to increase the diversity in sample participation without an FDA mandate is to include more black Americans in both volunteer and clinical roles during the research process to increase accountability in treatment, education, and advocacy.
"When more of us participate in clinical trials, we help build out the basic data sets that account for health disparities from the start, not after the fact," Lee says. She also suggests that researchers involve black patient representatives throughout the clinical trial process, from the study design to the interpretation of results.
"This allows for the black community to give insight on how to increase trial enrollment and help reduce stigma," she explains.
Thankfully, partnerships are popping up like the one between The Howard University's Cancer Center and Driver, a platform that connects cancer patients to treatment and trials. These sorts of targeted and culturally tailored efforts allow black patients to receive assistance from well-respected organizations.
Some observers suggest that the federal government and pharmaceutical industries must step up to address the gap.
However, some experts say that the black community should not be held solely responsible for solving a problem it did not cause. Instead, some observers suggest that the federal government and pharmaceutical industries must step up to address the gap.
According to Balls-Berry, socioeconomic barriers like transportation, time off work, and childcare related to trial participation must be removed. "These are real-world issues and yet many times researchers have not included these things in their budgets."
When asked to comment, a spokesperson for BIO, the world's largest biotech trade association, emailed the following statement:
"BIO believes that that our members' products and services should address the needs of a diverse population, and enhancing participation in clinical trials by a diverse patient population is a priority for BIO and our member companies. By investing in patient education to improve awareness of clinical trial opportunities, we can reduce disparities in clinical research to better reflect the country's changing demographics."
For my mother, the patient suffering from autoimmune disease, the need for broad participation in medical research is clear. "Without clinical trials, we would have less diagnosis and solutions to diseases," she says. "I think it's an underutilized resource."
Why You Can’t Blame Your Behavior On Your Gut Microbiome
See a hot pizza sitting on a table. Count the missing pieces: three. They tasted delicious and yes, you've eaten enough—but you're still eyeing a fourth piece. Do you reach out and take it, or not?
"The difficulty comes in translating the animal data into the human situation."
Your behavior in that next moment is anything but simple: as far as scientists can tell, it comes down to a complex confluence of circumstances, genes, and personality characteristics. And the latest proposed addition to this list is the gut microbiome—the community of microorganisms, including bacteria, archaea, fungi, and viruses—that are full-time residents of your digestive tract.
It is entirely plausible that your gut microbiome might influence your behavior, scientists say: a well-known communication channel, called the gut-brain axis, runs both ways between your brain and your digestive tract. Gut bugs, which are close to the action, could amplify or dampen the messages, thereby shaping how you act. Messages about food-related behaviors could be particularly susceptible to interception by these microorganisms.
Perhaps it's convenient to imagine your resident microbes sitting greedily in your gut, crying for more pizza and tricking your brain into getting them what they want. The problem is, there's a distinct lack of scientific support for this actually happening in humans.
John Bienenstock, professor of pathology and molecular medicine at McMaster University (Canada), has worked on the gut microbiome-behavior connection for several decades. "There's a lot of evidence now in animals—particularly in mice," he says.
Indeed, his group and others have shown that, by eliminating or altering gut bugs, they can make mice exhibit different social behaviors or respond more coolly to stress; they can even make a shy mouse turn brave. But Bienenstock cautions: "The difficulty comes in translating the animal data into the human situation."
Animal behaviors are worlds apart from what we do on a daily basis—from brushing our teeth to navigating complex social situations.
Not that it's an easy task to figure out which aspects of animal research are relevant to people in everyday life. Animal behaviors are worlds apart from what we do on a daily basis—from brushing our teeth to navigating complex social situations.
Elaine Hsiao, assistant professor of integrative biology and physiology at UCLA, has also looked closely at the microbiome-gut-brain axis in mice and pondered how to translate the results into humans. She says, "Both the microbiome and behavior vary substantially [from person to person] and can be strongly influenced by environmental factors—which makes it difficult to run a well-controlled study on effects of the microbiome on human behavior."
She adds, "Human behaviors are very complex and the metrics used to quantify behavior are often not precise enough to derive clear interpretations." So the challenge is not only to figure out what people actually do, but also to give those actions numerical codes that allow them to be compared against other actions.
Hsiao and colleagues are nevertheless attempting to make connections: building on some animal research, their recent study found a three-way association in humans between molecules produced by their gut bacteria (that is, indole metabolites), the connectedness of different brain regions as measured through functional magnetic resonance imaging, and measures of behavior: questionnaires assessing food addiction and anxiety.
Meanwhile, other studies have found it may be possible to change a person's behavior through either probiotics or gut-localized antibiotics. Several probiotics even show promise for altering behavior in clinical conditions like depression. Yet how these phenomena occur is still unknown and, overall, scientists lack solid evidence on how bugs control behavior.
Bienenstock, however, is one of many continuing to investigate. He says, "Some of these observations are very striking. They're so striking that clearly something's up."
He says that after identifying a behavior-changing bug, or set of bugs, in mice: "The obvious next thing is: How [is it] occurring? Why is it occurring? What are the molecules involved?" Bienenstock favors the approach of nailing down a mechanism in animal models before starting to investigate its relevance to humans.
He explains, "[This preclinical work] should allow us to identify either target molecules or target pathways, which then can be translated."
Bienenstock also acknowledges the 'hype' that appears to surround this particular field of study. Despite the decidedly slow emergence of data linking the microbiome to human behavior, scientific reviews have appeared in brain-related scientific journals—for instance, Trends in Cognitive Sciences; CNS Drugs—with remarkable frequency. Not only this, but popular books and media articles have given the idea wings.
It might be compelling to blame our microbiomes for behaviors we don't prefer or can't explain—like reaching for another slice of pizza. But until the scientific observations yield stronger results, we still lack proof that we're doing what we do—or eating what we eat—exclusively at the behest of our resident microorganisms.