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.
This past April, an alleged serial rapist and murderer, who had remained unidentified for over 40 years, was located by comparing a crime scene DNA profile to a public genetic genealogy database designed to identify biological relatives and reconstruct family trees. The so-called "Golden State Killer" had not placed his own profile in the database.
Forensic use of genetic genealogy data is possible thanks to widening public participation in direct-to-consumer recreational genetic testing.
Instead, a number of his distant genetic cousins had, resulting in partial matches between themselves and the forensic profile. Investigators then traced the shared heritage of the relatives to great-great-great-grandparents and using these connections, as well as other public records, narrowed their search to just a handful of individuals, one of whom was found to be an exact genetic match to the crime scene sample.
Forensic use of genetic genealogy data is possible thanks to widening public participation in direct-to-consumer recreational genetic testing. The Federal Bureau of Investigation maintains a national forensic genetic database (which currently contains over 16 million unique profiles, over-representing individuals of non-European ancestry); each profile holds genetic information from only 13 to 20 variable gene regions, just enough to identify a suspect. However, since this database and related forensic databases were established, the nature of genetic profiling has significantly changed: direct-to-consumer genetic tests routinely use whole genome scans involving simultaneous analysis of hundreds of thousands of variants.
With such comprehensive genetic information, it becomes possible to discern more distant genetic relatives. Thus, even though public DNA collections are smaller than most law enforcement databases, the potential to connect a crime scene sample to biological relatives is enhanced. The successful use of one genealogy database (GEDMatch) in the GSK case demonstrates the power of the approach, so much so that the genetic profiles of over 100 similar cold cases are now being run through the same resource. Indeed, in the two months since the GSK case was first reported, 5 other cold cases have been solved using similar methods.
Autonomy in the Genomic Age
While few would disagree with the importance of finally bringing to justice those who commit serious violent offenses, this new forensic genetic application has sparked broad discussion of privacy-related and ethical concerns. Before, the main genetic databases accessible to the police were those containing the profiles of accused or convicted criminals, but now the DNA of many more "innocent bystanders," across multiple generations, are in play.
The genetic services that provide a venue for data sharing typically warn participants that their information can be used for purposes beyond those they intend, but there is no legal prohibition on the use of crowd-sourced public collections for forensic investigation. Some services, such as GEDMatch, now explicitly welcome possible law enforcement use.
The decisions of individuals to contribute their own genetic information inadvertently exposes many others across their family tree.
The implication is that consumers must choose for themselves whether they are willing to bring their genetic information into the public sphere. Many have no problem doing so, seeing value in law enforcement access to such data. But the decisions of individuals to contribute their own genetic information inadvertently exposes many others across their family tree who may not be aware of or interested in their genetic relationships going public.
As one well-known statistical geneticist who predicted forensic uses of public genetic data noted: "You are a beacon who illuminates 300 people around you." By the same token, 300 people, most of whom you do not know and have probably never met, can illuminate your genetic information; indeed a recent analysis has suggested that most in the U.S. are identifiable in this way. There is nothing that you can do about it, no way to opt out. Thus, police interaction with such databases must be addressed as a public policy issue, not left to the informed consent of individual consumers.
When Consent Will Not Suffice
For those concerned by the broader implications of such practices, the simplest solution might be to discourage open access sharing of detailed genetic information. But let's say that we are willing to continue to allow those with an interest in genealogy to make their data readily searchable. What safeguards should we implement to ensure that the family members who don't want to opt in, or who don't have the ability to make that choice, remain unharmed? Their autonomy counts, too.
We might consider regulation similar to the kind that limit law enforcement use of forensic genetic databases of convicted and arrested individuals. For example, in California, familial searches can only be performed using the database of convicted individuals in cases of serious crimes with public safety implications where all other investigatory methods have been exhausted, and where single-source high-quality DNA is available for analysis. Further, California policy separates the genealogical investigative team from local detectives, so as to minimize the impact of incidental findings (such as unexpected non-paternity).
Importantly, the individual apprehended was not the first, or even second, but the third person subjected to enhanced police scrutiny.
No such regulations currently govern law enforcement searches of public genealogical databases, and we know relatively little about the specifics of the GSK investigation. We do not know the methods used to infer genetic relationships, or their likelihood of mistakenly suggesting a relationship where none exists. Nor do we know the level of genetic identity considered relevant for subsequent follow-up. It is also unclear how law enforcement investigators combined the genetic information they received with other public records data. Together, this leaves room for an unknown degree of investigation into an unknown number of individuals.
Why This Matters
What has been revealed is that the GSK search resulted in the identification of 10 to 20 potential distant genetic relatives, which led to the investigation of 25 different family trees, 24 of which did not contain the alleged serial rapist and murderer. While some sources described a pool of 100 possible male suspects identified from this exercise, others imply that the total number of relatives encompassed by the investigation was far larger. One account, for example, suggests that there were roughly 1000 family members in just the one branch of the genealogy that included the alleged perpetrator. Importantly, the individual apprehended was not the first, or even second, but the third person subjected to enhanced police scrutiny: reports describe at least two false leads, including one where a warrant was issued to obtain a DNA sample.
These details, many of which only came to light after intense press coverage, raise a host of concerns about the methods employed and the degree to which they exposed otherwise innocent individuals to harms associated with unjustified privacy intrusions. Only with greater transparency and oversight will we be able to ensure that the interests of people curious about their family tree do not unfairly impinge on those of their mostly law-abiding near and distant genetic relatives.
Eric Kandel, 88, is a living legend. A specialist in the neurobiology of learning and memory, he received a Nobel Prize in 2000 for his work on the physiological basis of memory storage. Kandel is the Director of the Kavli Institute for Brain Science and Co-Director of the Mortimer B. Zuckerman Mind Brain Behavior Institute at Columbia University, where he has taught and conducted research for 44 years.
"If you walk two or three miles a day, you will release sufficient osteocalcin from your bones to combat non-Alzheimer's age-related memory loss."
And he's still going strong. Leapsmag Editor-in-Chief Kira Peikoff recently caught up with Dr. Kandel about his latest research, his advice for fellow seniors, and his opinions on some of the biggest challenges in neuroscience today.
What are working on these days?
I'm working on three problems: one is age-related memory loss, the second is post-traumatic stress disorder, and the third is the beholder's share: how a viewer responds to works of art. The beholder's share is a term that Alois Riegl created. He said there are two shares to a painting: the painter creates it, but it's not meaningful until somebody responds to it: the viewer, the beholder.
That's fascinating. As far as age-related memory loss, what are you learning in that area?
I'm learning that there are two forms of age-related memory loss. One is Alzheimer's disease, which we've known about for a long time. But the second is a more benign form which I call just age-related memory loss, which begins actually somewhat earlier and has a very different anatomical locus in the brain. It is caused by a different anatomical defect and responds to different therapeutic measures. It critically involves an area in the hippocampus called the dentate gyrus and it responds to a hormone released by bone called osteocalcin.
It therefore seems likely that one very effective way of combatting age-related memory loss is walking. If you walk two or three miles a day, you are likely to release sufficient osteocalcin from your bones to combat non-Alzheimer's age-related memory loss. In collaboration with Gerard Karsenty at Columbia, my lab at Columbia has been exploring this over the last year and a half.
Have you published anything about this yet?
We are just getting ready to do so.
"I think at the moment we should stick with trying to just reverse abnormalities."
Another question I have is about brain-computer interfaces to help cure disease or even provide cognitive enhancements. What do you think of companies like Kernel and Neuralink that are trying to push this new technology?
I think if it works it would be very nice. We have to see some direct evidence first, but it's certainly an encouraging approach. I think there are a number of directions we could take. The one I think at the moment is most profitable is to try to use the brain as it is and try to enhance it, restore it, refurbish it, make it function better from its age-related condition.
You mean, without some kind of machine interface?
Without necessarily introducing anything from the outside world. Although I have no objection whatsoever to introducing ancillary aids if they're beneficial and not harmful.
Do you have any opinion on whether neuroscience and technology should aim to provide an enhancement to the brain or just return it to baseline and cure disease?
I would be perfectly satisfied if we just cured diseases. I think at the moment we should stick with trying to just reverse abnormalities, but certainly … having the capability of becoming more intelligent, more attentive, capable of remembering things better than normal, that would be nice.
What do you think is the most important challenge facing the field of neuroscience today?
It's hard to say. I think the biology of consciousness is one fantastic problem. Trying to understand and successfully reverse some of the abnormalities of the brain, like age-related memory loss, schizophrenia, depression, manic depressive illness would be wonderful.
To be able to reverse memory loss, to allow people in their 70s, 80s, and 90s to live free and independent lives, is a major challenge for brain science.
Absolutely. Is there anything else you'd like to share with our readers about your research or the field more broadly?
I'd emphasize that brain science is a relatively young discipline but it's moving ahead in a very responsible and a very effective fashion, making progress in a number of areas, and is clearly sensitive to, and responsive to, the demands of the social situation. Right now, number one, the population is aging dramatically. In 1900, the average life expectancy was 50, and now the average life expectancy is 78 for men, and 82 for women.
So people are living longer and therefore are having age-related diseases, including memory loss. To be able to reverse it, to allow people in their 70s, 80s, and 90s to live free and independent lives, is a major challenge for brain science in both its basic and its clinically applied fashion. I think this is very important and serious effort should be put into this.
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.