Why a Topical Cannabidiol Gel May Help Treat the Behavioral Symptoms of Fragile X
February 3, 2023
Fragile X syndrome is a rare, genetic, developmental disorder that is the leading known cause of both intellectual disability and autism spectrum disorder. People with the condition can have a range of behavioral symptoms, such as social avoidance and irritability. Zynerba is developing its experimental therapy Zygel, a topical cannabidiol gel that is delivered into the bloodstream through the skin to treat the behavioral symptoms of Fragile X. We spoke to co-director of the molecular diagnostics section of the Genetic Laboratory at Rush Medical College Elizabeth Berry-Kravis and Zynerba Chairman and CEO Armando Anido, about Fragile X, the company’s experimental therapy Zygel, and why the topical cannibidiol gel may hold promise for treating the behavioral symptoms of the condition.
Daniel Levine: Elizabeth, Armando, thanks for joining us.
Armando Anido: Thank you very much for having me.
Elizabeth Berry-Kravis: Yes, thank you.
Daniel Levine: We’re going to talk about Fragile X, the role the messenger molecule, known as cyclic AMP, plays in the condition and Zynerba’s effort to develop a cannabidiol gel to treat the neurodevelopmental condition. Let’s start with Fragile X itself. Elizabeth, for listeners not familiar with the condition, what is it?
Elizabeth Berry-Kravis: Fragile X syndrome is a developmental disorder kind of like Down syndrome where patients are born normally, but then they develop more slowly than usual. They learn more slowly than usual, and many have significant behavioral challenges like attention problems, hyperactivity problems with aggression and anxiety. And these behavioral problems vary quite a bit from one patient to another. About half the boys with Fragile X will have autism as well as Fragile X because that’s a clinical diagnosis. Fragile X is caused by a mutation in a single gene on the X chromosome that basically inactivates the gene and prevents it from making its normal messenger RNA, and then from making the normal protein that would usually be in the neurons. And the lack or reduction of that protein in neurons leads to problems with the neurons connecting and wiring appropriately to support normal learning and normal behavior.
Daniel Levine: Does the condition progress over time?
Elizabeth Berry-Kravis: It’s not really progressive. As the patient gets older, it becomes more clear that they have the significant learning problems. There’s not much difference between a young baby with Fragile X and a typical young baby, but by the time a person is five or six, you can clearly see that there are differences in their ability level from a typical five or six year old. And by the time the person is an adult, it’s very clear they can’t do things that a normal adult would do. And the differences are more pronounced for males with Fragile X because they only have one X chromosome where the girls have two X chromosomes. And so, there the mutations on one of the chromosomes and the other X chromosome can kind of balance it. So, girls usually can be anywhere from normal to having a lot of symptoms, whereas males with Fragile X usually have pretty significant symptoms and learning problems as well as more behavioral issues than girls have. But across the board, [for] people with Fragile X probably the number one behavioral symptom is anxiety. There’s a lot of anxiety associated with the condition, and both the girls and the guys have issues with anxiety.
Daniel Levine: Beyond that, is there a relationship between Fragile X and autism?
Elizabeth Berry-Kravis: Yeah, so about half of males with Fragile X will be diagnosed with autism, meaning that they’ll meet the clinical criteria for autism, not that they have a different disorder. They have clinical symptoms of autism, but the cause of that autism is their Fragile X syndrome and their Fragile X mutation. For girls it’s more like about 20 percent of girls will meet the clinical criteria for autism. So there’s a very significant overlap, but again, the autism is a clinical diagnosis and the Fragile X syndrome is a DNA-based or molecular diagnosis.
Daniel Levine: What treatment options exist today and what’s the prognosis for someone with the condition?
Elizabeth Berry-Kravis: Well, right now we have supportive treatment. When patients are diagnosed, we make sure that they’re getting into appropriate kinds of therapy, like speech and occupational therapy, physical therapy, and that they’re in a special education program where their program and their curriculum is well designed for the kind of learning patterns that we see in people with Fragile X. That’s all supportive management. And then also some of the patients have enough problems with behavior that their behavior really interrupts their functioning. And so, we may treat them with medications that one might use for attention deficit disorder or for anxiety or for aggression or irritability. Those are supportive medications that help with certain behaviors, but that don’t change really the underlying disorder. So, we don’t currently have any treatment option that’s targeted to the actual disorder. We more have supportive medications that help the patient manage the symptoms that they may have of the Fragile X. So, in other words, we can’t treat the learning and cognition because we don’t have any medications that work on that.
Daniel Levine: You’ve been studying Fragile X for 30 years. Now, my understanding is you didn’t set out to study Fragile X. How did you come to investigate the condition?
Elizabeth Berry-Kravis: Yeah, so I was studying cyclic AMP as a signaling molecule in the brain. And that’s what I did for my PhD, only I studied it in cells for my PhD. But I was still over at University of Chicago where I had done my PhD studies when I was doing my fellowship. And Dr. Peter Huttenlocher, who is my mentor and the director of my pediatric neurology program there, wanted to study cyclic AMP because he was very close to Eric Kandel, who was studying cyclic AMP and Aplysia and Drosophila mutants as something that was important in the brain for regulating connections of neurons. So, essentially there was a condition called pseudo hypoparathyroidism that has a known defect in the gene that’s associated with problems with cyclic AMP signaling. And so, we set out to study that disease, but we could only find a few patients with that disease. And we actually wanted controls that also had an intellectual disability and the only thing we could find at the time where we could get enough controls that all had the same condition was Fragile X syndrome. So, we started studying the Fragile X patients as controls for this other condition. But what we found was that the Fragile X patients had a bigger deficit in production of cyclic AMP in their cells, and we were studying platelets at the time, than the pseudo hyperparathyroid patients did. And so, then Fragile X became very interesting with respect to this potential mechanism. As a result of doing these studies, I had to call patients and families to come in and donate blood to my study. And sometimes we went to their houses to get the blood if the patient was difficult to get into clinic. So, I got to know these families and they asked me at some point, I think about two years into the study, if I would have a Fragile X clinic. And so, I did open a Fragile X clinic, which started at University of Chicago, and then moved six months later to Rush where I’ve been ever since. We completed that study as well as, of course. Ever since then, it’s now over 30 years later, and I’m still studying Fragile X and seeing huge numbers of patients in clinic. So, that’s how I got into the field. It was a little bit by accident.
Daniel Levine: Help us understand what cyclic AMP is, what its role is in the body, and what happens in the case of people with Fragile X. What is the cyclic AMP doing or not doing?
Elizabeth Berry-Kravis: Well, cyclic AMP is a signaling molecule that’s made in cells, not just the brain, but also in other cells, that is used for if you get the cell activated by something, you may have an increase or a decrease in cyclic AMP, and then that causes other things to happen in the cell or in the neurons. So, it might be facilitating connections to be made with other neurons or connections to be broken with other neurons. And so, it’s basically regulating the activity of the cell. In Fragile X, what we discovered was that not enough cyclic AMP would get made when the cells were stimulated by things that typically result in production of cyclic AMP, not enough cyclic AMP would be made. So, that would lead to dysregulated processes throughout the cell, like potentially, connectivity of the neurons. And cyclic AMP has been studied independently of Fragile X syndrome and multiple other systems, like in Drosophila. And so, if you have problems with regulating cyclic AMP in flies, you get these learning deficits. Likewise, in Aplysia, which is a sea snail, you get difficulty with neurological function when the cyclic AMP is not regulated correctly. So, the cyclic AMP could just be thought of as a master regulator that regulates a lot of things in neurons, and that has to be itself regulated correctly by things that are activating the neurons. People with Fragile X syndrome have difficulty doing that correctly.
Daniel Levine: Let’s bring Armando in here. Armando Zynerba is developing Xygel for Fragile X in autism spectrum disorder in 22 Q. What is Xygel?
Armando Anido: Yeah, Xygel is actually the first and only transdermal cannabidiol gel or CBD gel. It is a small amount of gel applied to the upper arm and the drug then penetrates through the skin to get into the bloodstream and ultimately from the bloodstream, makes it into the brain in order to have some effects.
Daniel Levine: And how does it work?
Armando Anido: Well, as Dr. Berry-Kravis was saying, the mutation of the FMR1 gene does cause some dysregulation in the endocannabinoid system that results in some behavioral as well as cognitive symptoms. And though we don’t know for sure how Xygel truly works, it is believed that it does have an effect on the endocannabinoid system, which you know, may be the reason that it does have its effect.
Daniel Levine: Why use a transdermal delivery system for this?
Armando Anido: Yeah, so I think, as Dr. Berry-Kravis was mentioning, many of these children are diagnosed early in life. They’ve got a number of different things that they’re being treated with that are oral, and a transdermal gel is easy to be applied by the caregiver or the parent in order to help minimize the behavioral issues. It also avoids the gastrointestinal tract and side effects there. And at this point in time, what we know is that it does have a lower risk of liver toxicity based on its ability to bypass first-pass metabolism, and we also are seeing a lower number of drug interactions because of that. And we do know that other CBDs, oral CBDs, do convert to THC when exposed to high acidic environments such as the stomach.
Daniel Levine: Does that create any challenge in keeping dosing consistent among users?
Armando Anido: Yeah, we actually have developed it and put the amount of gel at 125 milligrams in a sachet. And today we are testing it in a clinical trial at doses that range from 250 up to 750 milligrams on a daily basis. So, it’s just the number of sachets they have to open to put onto the skin.
Daniel Levine: And what’s known about the safety and efficacy of Xygel from studies that have been done to date?
Armando Anido: Yeah, and you know, Dr. Berry-Kravis can actually talk a little bit more in terms of she’s been involved in our clinical trials, but to date, we have over 900 patients and volunteers that have been in trials. The majority of the treatment emergent adverse events have been mild to moderate and Xygel specific treatment emergent adverse events are primarily around application site events. It is a formulation that’s about 50 percent alcohol, and so it tends to have a drying effect on the skin, and we have not seen any clinically significant changes in vital signs or ECGs, and we have not seen any Zygel related clinically significant changes in lab values including liver function tests.
Daniel Levine: Well, Elizabeth, how meaningful would you say the results that you’ve seen are?
Elizabeth Berry-Kravis: I think we’ve seen some very nice results in the trial. As with every drug, the response varies from one patient to another. But the kinds of things that Xygel seems to work on are problems that patients with Fragile X have with social anxiety and difficulty with like getting overwhelmed when they have to go in the community or when they have to be around a lot of people. So, they can be very limited in terms of their life where they can’t go to things and they can’t do [things], they can’t participate in things or sometimes they become outright aggressive when they’re overwhelmed because the social situation is just too complex and too hard for them to take in. And so, we’ve seen patients who got substantially better and where were able to tolerate being in the community and doing different activities. Some patients, who really had difficulty struggling with having friends, were able to approach people and develop friendships better, and some kids who would have problems with, like, they get so anxious going to a restaurant, they would just vomit, and they had less trouble with that when they were on the treatment. So, I think there have been some quite clinically meaningful kinds of things that we’ve seen in the study and we still have to prove overall that. I mean, in the first study there was a nice signal in the fully methylated patients suggesting that they had improvement in both irritability and in social avoidance, which is a measure of that social anxiety. And now we’re in the second study and hopefully we will be able to show the same thing.
Daniel Levine: Armando, I know the company has had to revise its timelines because of the triple-demic and patients canceling their initial screening visits for the current phase 3 trial. What’s the development path forward and the expected timelines?
Armando Anido: Yeah, so the timelines were moved right around the end of December from the second half of this year to the first half of 2024, though we are still working and trying to figure out if we can get to the ultimate timeline, but being somewhat prudent. And the impact that the triple-demic had, just to give you an example, one week we had a significant number of initial screening visits that were being done at a number of different sites. And so, we were like, okay, things are moving in the right direction and continue. And then that same week, every single one of those initial screening visits were canceled because either the child, the caregiver, or a sibling was actually impacted by RSV or flu or Covid.
Daniel Levine: Xygel’s in development for a number of other indications. Is there reason to believe it could benefit other conditions besides the ones you’re currently pursuing?
Armando Anido: Yeah, I think that there has been some work that we did in adults with epilepsy where we didn’t find the right dose and probably didn’t hit it because the dosing was not appropriate. But we do believe that epilepsy, childhood epilepsy is an area where it may have some effect as well.
Daniel Levine: Elizabeth Berry-Kravis, co-director of the molecular diagnostic section of the Genetic Laboratory at Rush Medical College and Armando Anido, chairman of the Board and CEO of Zynerba Pharmaceuticals. Elizabeth and Armando, thank you both for your time today.
Armando Anido: Thank you very much, Danny.
Elizabeth Berry-Kravis: You’re welcome. Thank you.
This transcript has been edited for clarity and readability.
Sign up for updates straight to your inbox.