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.
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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.
This Mom Donated Her Lost Baby’s Tissue to Research
The twin boys growing within her womb filled Sarah Gray with both awe and dread. The sonogram showed that one, Callum, seemed to be the healthy child she and husband Ross had long sought; the other, Thomas, had anencephaly, a fatal developmental disorder of the skull and brain that likely would limit his life to hours. The options were to carry the boys to term or terminate both.
The decision to donate Thomas' tissue to research comforted Sarah. It brought a sense of purpose and meaning to her son's anticipated few breaths.
Sarah learned that researchers prize tissue as essential to better understanding and eventually treating the rare disorder that afflicted her son. And that other tissue from the developing infant might prove useful for transplant or basic research.
Animal models have been useful in figuring out some of the basics of genetics and how the body responds to disease. But a mouse is not a man. The new tools of precision medicine that measure gene expression, proteins and metabolites – the various chemical products and signals that fluctuate in health and illness – are most relevant when studying human tissue directly rather than in animals.
The decision to donate Thomas' tissue to research comforted Sarah. It brought a sense of purpose and meaning to her son's anticipated few breaths.
Thomas Gray
(Photo credit: Mark Walpole)
Later Sarah would track down where some of the donated tissues had been sent and how they were being used. It was a rare initiative that just may spark a new kind of relationship between donor families and researchers who use human tissue.
Organ donation for transplant gets all the attention. That process is simple, direct, life saving, the stories are easy to understand and play out regularly in the media. Reimbursement fully covers costs.
Tissue donation for research is murkier. Seldom is there a direct one-to-one correlation between individual donation and discovery; often hundreds, sometimes thousands of samples are needed to tease out the basic mechanisms of a disease, even more to develop a treatment or cure. The research process can be agonizingly slow. And somebody has to pay for collecting, processing, and getting donations into the hands of appropriate researchers. That story rarely is told, so most people are not even aware it is possible, let alone vital to research.
Gray set out on a quest to follow where Thomas' tissue had gone and how it was being used to advance research and care.
The dichotomy between transplant and research became real for Sarah several months after the birth of her twins, and Thomas' brief life, at a meeting for families of transplant donors. Many of the participants had found closure to their grieving through contact with grateful recipients of a heart, liver, or kidney who had gained a new lease on life. But there was no similar process for those who donated for research. Sarah felt a bit, well, jealous. She wanted that type of connection too.
Gray set out on a quest to follow where Thomas' tissue had gone and how it was being used to advance research and care. Those encounters were as novel for the researchers as they were for Sarah. The experience turned her into an advocate for public education and financial and operational changes to put tissue donation for research on par with donations for transplant.
Thomas' retina had been collected and processed by the National Disease Research Interchange (NDRI), a nonprofit that performs such services for researchers on a cost recovery basis with support from the National Institutes of Health. The tissue was passed on to Arupa Ganguly, who is studying retinoblastoma, a cancer of the eye, at the University of Pennsylvania.
Ganguly was surprised and apprehensive months later when NDRI emailed her saying the mother of donated tissue wanted to learn more about how the retina was being used. That was unusual because research donations generally are anonymous.
The geneticist waited a day or two, then wrote an explanation of her work and forwarded it back through NDRI. Soon the researcher and mother were talking by phone and Sarah would visit the lab. Even then, Ganguly felt very uncomfortable. "Something very bad happened to your son Thomas but it was a benefit for me, so I'm feeling very bad," she told Sarah.
"And Sarah said, Arupa, you were the only ones who wanted his retinas. If you didn't request them, they would be buried in the ground. It gives me a sense of fulfillment to know that they were of some use," Ganguly recalls. And her apprehension melted away. The two became friends and have visited several times.
Sarah Gray visits Dr. Arupa Ganguly at the University of Pennsylvania's Genetic Diagnostic Laboratory.
(Photo credit: Daniel Burke)
Reading Sarah Gray's story led Gregory Grossman to reach out to the young mother and to create Hope and Healing, a program that brings donors and researchers together. Grossman is director of research programs at Eversight, a large network of eye banks that stretches from the Midwest to the East Coast. It supplies tissue for transplant and ocular research.
"Research seems a cold and distant thing," Grossman says, "we need to educate the general public on the importance and need for tissue donations for research, which can help us better understand disease and find treatments."
"Our own internal culture needs to be shifted too," he adds. "Researchers and surgeons can forget that these are precious gifts, they're not a commodity, they're not manufactured. Without people's generosity this doesn't exist."
The initial Hope and Healing meetings between researchers and donor families have gone well and Grossman hopes to increase them to three a year with support from the Lions Club. He sees it as a crucial element in trying to reverse the decline in ocular donations even while research needs continue to grow.
What people hear about is "Tuskegee, Henrietta Lacks, they hear about the scandals, they don't hear about the good news. I would like to change that."
Since writing about her experience in the 2016 book "A Life Everlasting," Gray has come to believe that potential donor families, and even people who administer donation programs, often are unaware of the possibility of donating for research.
And roadblocks are common for those who seek to do so. Just like her, many families have had to be persistent in their quest to donate, and even educate their medical providers. But Sarah believes the internet is facilitating creation of a grassroots movement of empowered donors who are pushing procurement systems to be more responsive to their desires to donate for research. A lot of it comes through anecdote, stories, and people asking, if they have done it in Virginia, or Ohio, why can't we do it here?
Callum Gray and Dr. Arupa Ganguly hug during his family's visit to the lab.
(Photo credit: Daniel Burke)
Gray has spoken at medical and research facilities and at conferences. Some researchers are curious to have contact with the families of donors, but she believes the research system fosters the belief that "you don't want to open that can of worms." And lurking in the background may be a fear of liability issues somehow arising.
"I believe that 99 percent of what happens in research is very positive, and those stories would come out if the connections could be made," says Sarah Gray. But what they hear about is "Tuskegee, Henrietta Lacks, they hear about the scandals, they don't hear about the good news. I would like to change that."