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.
Dadbot, Wifebot, Friendbot: The Future of Memorializing Avatars
In 2016, when my family found out that my father was dying from cancer, I did something that at the time felt completely obvious: I started building a chatbot replica of him.
I simply wanted to create an interactive way to share key parts of his life story.
I was not under any delusion that the Dadbot, as I soon began calling it, would be a true avatar of him. From my research about the voice computing revolution—Siri, Alexa, the Google Assistant—I knew that fully humanlike AIs, like you see in the movies, were a vast ways from technological reality. Replicating my dad in any real sense was never the goal, anyway; that notion gave me the creeps.
Instead, I simply wanted to create an interactive way to share key parts of his life story: facts about his ancestors in Greece. Memories from growing up. Stories about his hobbies, family life, and career. And I wanted the Dadbot, which sent text messages and audio clips over Facebook Messenger, to remind me of his personality—warm, erudite, and funny. So I programmed it to use his distinctive phrasings; to tell a few of his signature jokes and sing his favorite songs.
While creating the Dadbot, a laborious undertaking that sprawled into 2017, I fixated on two things. The first was getting the programming right, which I did using a conversational agent authoring platform called PullString. The second, far more wrenching concern was my father's health. Failing to improve after chemotherapy and immunotherapy, and steadily losing energy, weight, and the animating sparkle of life, he died on February 9.
John Vlahos at a family reunion in the summer of 2016, a few months after his cancer diagnosis.
(Courtesy James Vlahos)
After a magazine article that I wrote about the Dadbot came out in the summer of 2017, messages poured in from readers. While most people simply expressed sympathy, some conveyed a more urgent message: They wanted their own memorializing chatbots. One man implored me to make a bot for him; he had been diagnosed with cancer and wanted his six-month-old daughter to have a way to remember him. A technology entrepreneur needed advice on replicating what I did for her father, who had stage IV cancer. And a teacher in India asked me to engineer a conversational replica of her son, who had recently been struck and killed by a bus.
Journalists from around the world also got in touch for interviews, and they inevitably came around to the same question. Will virtual immortality, they asked, ever become a business?
The prospect of this happening had never crossed my mind. I was consumed by my father's struggle and my own grief. But the notion has since become head-slappingly obvious. I am not the only person to confront the loss of a loved one; the experience is universal. And I am not alone in craving a way to keep memories alive. Of course people like the ones who wrote me will get Dadbots, Mombots, and Childbots of their own. If a moonlighting writer like me can create a minimum viable product, then a company employing actual computer scientists could do much more.
But this prospect raises unanswered and unsettling questions. For businesses, profit, and not some deeply personal mission, will be the motivation. This shift will raise issues that I didn't have to confront. To make money, a virtual immortality company could follow the lucrative but controversial business model that has worked so well for Google and Facebook. To wit, a company could provide the memorializing chatbot for free and then find ways to monetize the attention and data of whoever communicated with it. Given the copious amount of personal information flowing back and forth in conversations with replica bots, this would be a data gold mine for the company—and a massive privacy risk for users.
Virtual immortality as commercial product will doubtless become more sophisticated.
Alternately, a company could charge for memorializing avatars, perhaps with an annual subscription fee. This would put the business in a powerful position. Imagine the fee getting hiked each year. A customer like me would find himself facing a terrible decision—grit my teeth and keep paying, or be forced to pull the plug on the best, closest reminder of a loved one that I have. The same person would effectively wind up dying twice.
Another way that a beloved digital avatar could die is if the company that creates it ceases to exist. This is no mere academic concern for me: Earlier this year, PullString was swallowed up by Apple. I'm still able to access the Dadbot on my own computer, fortunately, but the acquisition means that other friends and family members can no longer chat with him remotely.
Startups like PullString, of course, are characterized by impermanence; they tend to get snapped up by bigger companies or run out of venture capital and fold. But even if big players like, say, Facebook or Google get into the virtual immortality game, we can't count on them existing even a few decades from now, which means that the avatars enabled by their technology would die, too.
The permanence problem is the biggest hurdle faced by the fledgling enterprise of virtual immortality. So some entrepreneurs are attempting to enable avatars whose existence isn't reliant upon any one company or set of computer servers. "By leveraging the power of blockchain and decentralized software to replicate information, we help users create avatars that live on forever," says Alex Roy, the founder and CEO of the startup Everlife.ai. But until this type of solution exists, give props to conventional technology for preserving memories: printed photos and words on paper can last for centuries.
The fidelity of avatars—just how lifelike they are—also raises serious concerns. Before I started creating the Dadbot, I worried that the tech might be just good enough to remind my family of the man it emulated, but so far off from my real father that it gave us all the creeps. But because the Dadbot was a simple chatbot and not some all-knowing AI, and because the interface was a messaging app, there was no danger of him encroaching on the reality of my actual dad.
But virtual immortality as commercial product will doubtless become more sophisticated. Avatars will have brains built by teams of computer scientists employing the latest techniques in conversational AI. The replicas will not just text but also speak, using synthetic voices that emulate the ones of the people being memorialized. They may even come to life as animated clones on computer screens or in 3D with the help of virtual reality headsets.
What fascinates me is how technology can help to preserve the past—genuine facts and memories from peoples' lives.
These are all lines that I don't personally want to cross; replicating my dad was never the goal. I also never aspired to have some synthetic version of him that continued to exist in the present, capable of acquiring knowledge about the world or my life and of reacting to it in real time.
Instead, what fascinates me is how technology can help to preserve the past—genuine facts and memories from people's lives—and their actual voices so that their stories can be shared interactively after they have gone. I'm working on ideas for doing this via voice computing platforms like Alexa and Assistant, and while I don't have all of the answers yet, I'm excited to figure out what might be possible.
[Adapted from Talk to Me: How Voice Computing Will Transform the Way We Live, Work, and Think (Houghton Mifflin Harcourt, March 26, 2019).]
The Best Kept Secret on the International Space Station
[Editor's Note: This video is the second of a five-part series titled "The Future Is Now: The Revolutionary Power of Stem Cell Research." Produced in partnership with the Regenerative Medicine Foundation, and filmed at the annual 2019 World Stem Cell Summit, this series illustrates how stem cell research will profoundly impact life on earth.]
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.