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.
A few days before Christmas 2015, Paige Alexandria, a 28-year-old counselor at the Austin Women's Health Center in Texas, found out she was pregnant.
Alexandria had missed the cutoff for a medication abortion by three days.
"It was an unplanned pregnancy, and instantaneously I knew I needed an abortion," Alexandria recalls. Already a mother of two children, one with special needs, a third child was not something Alexandria and her husband felt prepared to take on. "Mentally, I knew my limit. I wasn't prepared for a third and I didn't want one," she says.
At an ultrasound appointment one week later, scans showed she was a little over eight weeks pregnant. Alexandria opted to have an abortion as soon as possible, and preferably with medication. "I really wanted to avoid a surgical abortion," she says. "It sounded a lot more invasive, and I'm already uncomfortable with pap smears and pelvic exams, so I initially went in wanting to do the pill."
But at the time, medication guidelines stipulated that one of the pills, called Mifepristone, could only be prescribed to end a pregnancy at eight weeks gestation or earlier – Alexandria had missed the cutoff by three days. If she wanted to end the pregnancy, she would need to undergo a surgical abortion, otherwise known as a vacuum aspiration abortion.
With a vacuum aspiration abortion, doctors dilate the cervix and manually aspirate out the contents of the uterus. Medication abortion, on the other hand, consists of the patient taking two pills – Mifepristone, which blocks the hormones that help the pregnancy develop, and Misoprostol, which empties the uterus over a period of days, identical to a miscarriage.
Alexandria was upset about the change of plans but resolute in her decision to end the pregnancy. "The fact that I didn't really have a choice in how my procedure was performed has made the experience just a little more sensitive for me," she says. She scheduled the earliest available appointment for a surgical abortion.
Paige Alexandria would have chosen to terminate her pregnancy with medication if the regulations were less stringent.
(Photo courtesy of Alexandria)
Like Alexandria, many people looking to terminate a pregnancy opt to do so with medication. According to research from the Guttmacher Institute, medication abortions accounted for nearly 40 percent of all abortions in the year 2017 – a marked increase from 2001, when medication abortions only accounted for roughly five percent of terminations. Taken 24-48 hours apart, Mifepristone and Misoprostol have a 95-99 percent success rate in terminating pregnancies up to 63 days – or nine weeks – of gestation, according to the American College of Obstetrics and Gynecology (ACOG).
But even though the World Health Organization (WHO) considers medical abortion to be highly safe and effective, the medication is still carefully guarded in the United States: Mifepristone is only available for terminating pregnancies up to 10 weeks gestation, per the FDA, even though limited research suggests that both are safe and effective at terminating pregnancies between 12 and 20 weeks.
Additionally, a separate set of regulations known as a Risk Evaluation and Mitigation Strategy (REMS) means that patients can only take Mifepristone under specific circumstances. Mifepristone must be distributed in person by a healthcare provider – usually interpreted in most states as a doctor or nurse practitioner – who has registered with the drug's manufacturer. The medication cannot be distributed through a pharmacy, so doctors who wish to provide the drug must stock the medication in-office, and both the provider and the patient must sign a form that warns them of the "risk of serious complications associated with Mifepristone," according to the FDA.
"REMS is a set of restrictions that the FDA puts on the distribution of drugs it considers dangerous or risky in some way," says Dr. Elizabeth Raymond, an OB-GYN and senior medical associate at Gynuity Health Projects. Although not always called REMS, these restrictions have been imposed on Mifepristone since the medication was approved by the FDA in 2000, Raymond says.
Raymond is part of a growing number of physicians and researchers who want to eliminate the REMS requirements for Mifepristone, also known by its brand name Mifeprex. In 2017, Raymond and several other physicians authored a paper in the New England Journal of Medicine (NEJM) arguing that Mifepristone is extremely safe and needlessly over-regulated.
"When the FDA first approved [Mifepristone] and imposed these requirements, they might have made sense 19 years ago when there was limited information about the use of this treatment in the United States," says Dr. Daniel Grossman, director at Advancing New Standards in Reproductive Health at UCSF and co-author of the 2017 report in the NEJM. "Now, after 19 years, it's clear that this medication is very safe, and safer than a lot of others available in a pharmacy."
Since 2000, Mifepristone has been implicated in 19 deaths, making its mortality rate 0.00063 percent.
According to their research, over three million people have taken Mifepristone since it was approved in 2000. Since then, Mifepristone has been implicated in 19 deaths, making its mortality rate 0.00063 percent. Even then, the risk is inflated, Grossman says.
"The requirement is that practitioners need to report any deaths that occur after taking these medications, and so you'll see deaths included in that figure which are homicides or suicides or something unrelated to taking Mifepristone," says Grossman. In contrast, Acetaminophen – better known as Tylenol – was associated with 458 overdose deaths between 1990 and 1998, as well as 56,000 emergency room visits and 26,000 hospitalizations. Sildenafil, better known as Viagra, was linked to 762 deaths in the first twenty months after it was approved by the FDA. Yet neither Tylenol nor Viagra have been burdened with the same REMS restrictions as Mifepristone.
"It's clearly about more than just the safety of the medication at this point," says Grossman. "It's more about stigma related to abortion and politics."
For people who want a medication abortion, the REMS requirements mean they often need to take off work to schedule a doctor's appointment, arrange for transportation and childcare, and then arrange an additional doctor's appointment days afterward to take the second dose of medication. While surgical abortion procedures are quicker (usually a one-day outpatient procedure, depending on gestation), many people prefer having the abortion in the comfort of their home or surrounded by family instead.
Paige Alexandria, who counsels people seeking abortions at her job, says that survivors of sexual violence often prefer medical abortions to surgical ones. "A lot of time survivors have a trauma associated with medical instruments or having pelvic exams, and so they're more comfortable taking a pill," she says.
But REMS also creates a barrier for healthcare providers, Grossman says. Stocking the medication in-office is "a hassle" and "expensive," while others are reluctant to register their name with the drug manufacturer, fearing harassment or violence from anti-choice protestors. As a result, the number of practitioners willing to provide medical abortions nationwide is severely limited. According to Grossman's own research published in the journal Obstetrics and Gynecology, 28 percent of OBGYNs admitted they would administer medication abortions if it were possible to write a prescription for Mifepristone rather than stock it in-office.
Amazingly, the restrictions on Mifepristone have loosened since it first came on the market. In 2016, the FDA updated the guidelines on Mifepristone to allow its use until 10 weeks gestation, up from eight weeks. But doctors say the REMS restrictions should be eliminated completely so that people can obtain abortions as early as possible.
"REMS restrictions inhibit people from being able to get a timely abortion," says Raymond, who stresses that abortion is generally more comfortable, more affordable, and safer for women the earlier it's done. "Abortion is very safe no matter when you get it, but it's also easier because there's less risk for bleeding, infections, or other complications," Raymond says. Abortions that occur earlier than eight weeks of gestation have a complication rate of less than one percent, while an abortion done at 12 or 13 weeks has a three to six percent chance of complications.
And even for people who want a medication abortion early on in their pregnancy, REMS restrictions make it so that they may not have time to obtain it before the 10-week period lapses, Raymond says.
"If you're seven weeks pregnant but it takes you three weeks to figure out travel and childcare arrangements to go into the doctor and take this medication, now you're at the cutoff date," she says. "Even if you manage to get an abortion at nine weeks, that's still a later gestational age, and so the risks are increased."
In 2016, at a little over nine weeks gestation, Alexandria completed her abortion by having a D&E. But because she didn't have anyone to drive her home after the procedure, she wasn't able to have sedation throughout, something she describes as "traumatic."
"I had the abortion completely aware and coherent, and paired with the fact that I hadn't even wanted a surgical abortion in the first place made it harder to deal with," Alexandria says.
"When you're just a day or two past eight weeks and you want an abortion – why is medication not immediately available?"
Today, Alexandria shares her story publicly to advocate for abortion care. Although she doesn't regret her surgical abortion and acknowledges that not everyone experiences surgical abortion the same way she did, she does wish that she could have gone a different route.
"If I had to do it over, I would still try to do the pill, because [the surgical abortion] was such a terrifying experience," she says. "When you're just a day or two past eight weeks and you want an abortion – why is medication not immediately available? It just doesn't make sense."
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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.