New drug for schizophrenia could meet desperate need for better treatments
The field of treating schizophrenia with drugs has been stuck in a long drought but, this month, a late-stage clinical trial found a new drug called KarXT could treat a range of symptoms.
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.
Kids' immune systems come into contact with so many antigens every day that extra cleaning and disinfecting won't harm them, experts say.
Cleaning has taken on a whole new meaning in Frank Mosco's household during the COVID-19 pandemic. There's a protocol for everything he and his two teenage daughters do.
Experts agree that over-disinfecting is better than inadequate disinfecting, especially during a pandemic.
"We wipe down every package that comes into the house and the items inside," says Mosco, a technologist and social justice activist in Hastings-on-Hudson, N.Y. "If it's a fruit or vegetable, I use vinegar and water, or water and soap. Then we throw out the boxes, clean up the table, and wash our hands." Only then do they put items away.
As the novel coronavirus continues to pose an invisible threat, parents of infants to adolescents are pondering how vigorously and frequently to clean and disinfect surfaces at home and apply hand sanitizer in public. They also fret over whether there can be too much of a good thing: Will making everything as seemingly germ-free as possible reduce immunity down the road?
Experts agree that over-disinfecting is better than inadequate disinfecting, especially during a pandemic. Every family should assess their particular risks. Factors to consider include pre-existing medical conditions, the number of people living in the same home, and whether anyone works in a hospital or other virus-prone environment, says Kari Debbink, assistant professor of biology at Bowie State University in Bowie, Maryland.
Constantly cleaning everything in sight isn't necessary, she explains, because coronavirus tends to spread mainly via immediate contact with respiratory droplets—catching it from surfaces is a less-likely scenario. The longer the virus stays on a surface, the less contagious it becomes.
Some parents worry that their children's growing bodies may become accustomed to an environment that is "too clean." Debbink, a virologist, offers a salient reminder: "The immune system comes into contact with many, many different antigens every day, and it is 'trained' from birth onwards to respond to pathogens. Doing a little more cleansing and disinfecting during the pandemic will not weaken the immune system."
Other experts agree. "There should be no negative outcome to properly washing your hands more frequently," says Stacey Schultz-Cherry, an infectious diseases specialist at St. Jude Children's Research Hospital in Memphis, Tennessee. "Even with enhanced disinfection, kids are still getting exposed to immune-boosting microbes from playing outside, having pets, etc."
"There's no reason why hand sanitizer would weaken anyone's immune system of any age."
Applying hand sanitizer consisting of at least 60 percent alcohol helps clean hands while outdoors, says Angela Rasmussen, associate research scientist and a virologist at Columbia University's Mailman School of Public Health in New York. "There's no reason why hand sanitizer would weaken anyone's immune system of any age," she adds, and recommends moisturizer so hands don't dry out from frequent use. Meanwhile, "cleaning and disinfecting at home also don't have an impact on antiviral immunity, in kids or adults."
With the coronavirus foremost in parents' minds, Patricia Garcia, a pediatric hospitalist, has fielded many questions about how thoroughly they should wipe, rub, scrub, or mop. As medical director of Connecticut Children's Healthy Homes Program in Hartford, which takes aim at toxins and other housing hazards, she reassures them with this mantra: "You're never going to get it perfectly sterilized, and that's okay."
To quell some of these concerns, in March the U.S. Environmental Protection Agency (EPA) released a list of products for household use. None of these products have been specifically tested against SARS-CoV-2, the novel coronavirus that causes COVID-19. But the agency expects these products to be effective because they have demonstrated efficacy against a different human coronavirus similar to SARS-CoV-2 or an even harder-to-kill virus.
Many products on the list contain isopropyl alcohol or hydrogen peroxide. "When using an EPA-registered disinfectant," the agency's website instructs, "follow the label directions for safe, effective use. Make sure to follow the contact time, which is the amount of time the surface should be visibly wet."
Bear in mind that not all cleaners actually disinfect, cautions Alan Woolf, a pediatrician at Boston Children's Hospital who directs its environmental health center and is a professor at Harvard Medical School. Some cleaners remove visible dirt, grease, and grime, but they don't kill viruses. Disinfectants by their nature inactivate both bacteria and viruses. "That's an important distinction," Woolf says.
Frequently touched surfaces—for instance, doorknobs, light switches, toilet-flushing levers, and countertops—should not only be cleaned, but also disinfected at least daily during a pandemic if someone in the household is sick. The objects one touches upon coming home are the ones most likely to become contaminated with viruses, experts say.
Before bringing items inside, "it might be good to clear off a counter space where they will be placed," says Debbink, the biology professor and virologist. "This way, they come into contact with as few items and surfaces as possible."
If space permits, another option would be to set aside nonperishable items. "I've heard of some families putting things in a 'mud room' and closing the door for 48 hours, some leaving things in their garage or car trunk," says Stephanie Holm, co-director of the Western States Pediatric Environmental Health Specialty Unit at the University of California, San Francisco. "Letting new purchases sit for 48 hours undisturbed would greatly reduce the number of viable viruses present."
Cleaning surfaces is recommended before disinfecting them. Holm suggests using unscented soap and microfiber cloths instead of paper towels, which can transmit bacteria and viruses from one area to another.
Soap has the power to eradicate viruses with at least 20 seconds of contact time. It attacks the coronavirus's protective coat, explains infectious diseases specialist Schultz-Cherry. "If you destroy the coat, the virus is no longer infectious. Influenza virus is also very sensitive to soap."
"The most important thing that parents should do for children's immune systems is make sure they are up to date on all their vaccines."
For cribs, toys, and other mouth-contact surfaces, sanitizing with soap and water, not disinfectants, is advisable, says pediatrician Woolf. Fresh fruits and vegetables also can be cleaned with soap, removing dirt and pesticide residue, he adds.
"Some parents are nervous about using disinfectant on toys, which is understandable, considering many toys end up in children's mouths, so soap and water can be an alternative," says pediatrician Garcia, who recommends using hot water.
While some toys can go in the washing machine and dryer or dishwasher, others need to be cleaned by hand, with dish soap or a delicate detergent, as indicated on their labels. But toys with electrical components cannot be submerged in water, in which case consulting the EPA's list of disinfectants may be a parent's best option, she says.
Labels on the back of cleaning and disinfecting products also contain specific instructions. Not allowing a liquid to sit on a surface for the recommended time results in exposure to chemicals without even accomplishing the intended purpose of disinfection. For most household bleach-containing agents, the advisable "dwell time" is 10 minutes. "Many people don't realize this," says Holm, the environmental health specialist who also trained as a physician.
Beware of combining any type of cleaners or disinfectants that aren't already premixed. Doing so can release harmful gases into the air, she cautions.
During the pandemic, Mosco and his daughters have been very conscientious about decontaminating whatever comes through their doors. Mosco says he doesn't believe the family is overusing cleaning and disinfecting products. Although he's fastidious, he says, "a completely sterile environment is not the goal."
His mother, who was a nurse, instilled in him that exposure to some bacteria is a good thing. In turn, he "always encouraged his kids to play with animals, and to have fun in sand and dirt, with plenty of sunlight to keep their immune systems strong."
Even though a vaccine for coronavirus currently doesn't exist, parents can take some comfort in the best weapon available today to protect kids from deadly pathogens: "The most important thing that parents should do for children's immune systems," says virologist Rasmussen, "is make sure they are up to date on all their vaccines."
A researcher works in the lab at Alnylam Pharmaceuticals, which has pioneered the development of RNAi therapies.
In October 2006, Craig Mello received a strange phone call from Sweden at 4:30 a.m. The voice at the other end of the line told him to get dressed and that his life was about to change.
"We think this could be effective in [the early] phase, helping the body clear the virus and preventing progression to that severe hyperimmune response which occurs in some patients."
Shortly afterwards, he was informed that along with his colleague Andrew Fire, he had won the Nobel Prize in Physiology or Medicine.
Eight years earlier, biologists Fire and Mello had made a landmark discovery in the history of genetics. In a series of experiments conducted in worms, they had revealed an ancient evolutionary mechanism present in all animals that allows RNA – the structures within our cells that take genetic information from DNA and use it to make proteins – to selectively switch off genes.
At the time, scientists heralded the dawn of a new field of medical research utilizing this mechanism, known as RNA interference or RNAi, to tackle rare genetic diseases and deactivate viruses. Now, 14 years later, the pharmaceutical company Alnylam — which has pioneered the development of RNAi-based treatments over the past decade — is looking to use it to develop a groundbreaking drug for the virus that causes COVID-19.
"We can design small interfering RNAs to target regions of the viral genome and bind to them," said Akin Akinc, who manages several of Alnylam's drug development programs. "What we're learning about COVID-19 is that there's an early phase where there's lots of viral replication and a high viral load. We think this could be effective in that phase, helping the body clear the virus and preventing progression to that severe hyperimmune response which occurs in some patients."
Called ALN-COV, Alnylam's treatment hypothetically works by switching off a key gene in the virus, inhibiting its ability to replicate itself. In order to deliver it to the epithelial cells deep in the lung tissue, where the virus resides, patients will inhale a fine mist containing the RNAi molecules mixed in a saline solution, using a nebulizer.
But before human trials of the drug can begin, the company needs to convince regulators that it is both safe and effective in a series of preclinical trials. While early results appear promising - when mixed with the virus in a test tube, the drug displayed a 95 percent inhibition rate – experts are reserving judgment until it performs in clinical trials.
"If successful this could be a very important milestone in the development of RNAi therapies, but virus infections are very complicated and it can be hard to predict whether a given level of inhibition in cell culture will be sufficient to have a significant impact on the course of the infection," said Si-Ping Han, who researches RNAi therapeutics at California Institute of Technology and is not involved in the development of this drug.
So far, Alnylam has had success in using RNAi to treat rare genetic diseases. It currently has treatments licensed for Hereditary ATTR Amyloidosis and Acute Hepatic Porphyria. Another treatment, for Primary Hyperoxaluria Type 1, is currently under regulatory review. But its only previous attempt to use RNAi to tackle a respiratory infection was a failed effort to develop a drug for respiratory syncytial virus (RSV) almost a decade ago.
However, the technology has advanced considerably since then. "Back then, RNAi drugs had no chemical modifications whatsoever, so they were readily degraded by the body, and they could also result in unintended immune stimulation," said Akinc. "Since then, we've learned how to chemically modify our RNAi's to make them immunosilent and give them improved potency, stability, and duration of action."
"It would be a very important milestone in the development of RNAi therapies."
But one key challenge the company will face is the sheer speed at which viruses evolve, meaning they can become drug-resistant very quickly. Scientists predict that Alnylam will ultimately have to develop a series of RNAi drugs for the coronavirus that work together.
"There's been considerable interest in using RNAi to treat viral infections, as RNA therapies can be developed more rapidly than protein therapies like monoclonal antibodies, since one only needs to know the viral genome sequence to begin to design them," said David Schaffer, professor of bioengineering at University of California, Berkeley. "But viruses can evolve their sequences rapidly around single drugs so it is likely that a combinatorial RNAi therapy may be needed."
In the meantime, Alnylam is conducting further preclinical trials over the summer and fall, with the aim of launching testing in human volunteers by the end of this year -- an ambitious aim that would represent a breakneck pace for a drug development program.
If the approach does ultimately succeed, it would represent a major breakthrough for the field as a whole, potentially opening the door to a whole new wave of RNAi treatments for different lung infections and diseases.
"It would be a very important milestone in the development of RNAi therapies," said Han, the Caltech researcher. "It would be both the first time that an RNAi drug has been successfully used to treat a respiratory infection and as far as I know, the first time that one has been successful in treating any disease in the lungs. RNAi is a platform that can be reconfigured to hit different targets, and so once the first drug has been developed, we can expect a rapid flow of variants targeting other respiratory infections or other lung diseases."