Developing Treatment for SCN2A

Webinar 1: ASO treatment for gain-of-function SCN2A

At the 2018 American Epilepsy Society meeting, Prof Petrou presented results from a mouse model of an antisense oligonucleotide (ASO) treatment for SCN2A epilepsies developed by RogCon and Ionis Pharmaceuticals. Praxis Precision Medicines have joined the collaboration to advance that treatment program (RC-222).

In this webinar, Prof Petrou discusses the ASO research in SCN2A as well as talks about what ASOs are and their safety. Dr Kiran Reddy discusses the process of taking an ASO from the laboratory to clinical trials, the steps involved in that process, and how the process can be sped up and facilitated by the SCN2A community.

Professor Steven Petrou, PhD FAHMA, is the Director of the Florey Institute of Neuroscience and Mental Health and Head of the Florey Department at The University of Melbourne. Prof Petrou is a PhD trained neuroscientist who focuses on the disease biology of neurogenetic disorders. His interdisciplinary research includes ion channel biophysics, neurophysiology, animal models of neurogenetic disorders, molecular and cellular biology, computational biology and instrumentation. Prof Petrou is the co-founder and Chief Scientific Officer of US based biotechs, RogCon Inc and Praxis Precision Medicines, companies pioneering breakthroughs in epileptic and neurological as well as psychiatric disorders. Prof Petrou has attracted over $50 million in research support, including $14 million as Chief Investigator on an NHMRC Program Grant.

Dr Kiran Reddy, MD, MBA is President & CEO of Praxis Precision Medicines, Inc a biotech compay focused on developing new therapies for neurologic and psychiatric disorders. Dr. Reddy serves on the business advisory board of the National Epilepsy Foundation, the board of the New England Epilepsy Foundation, and the Council for the National Center for Translational Sciences within NIH. Dr. Reddy holds MD and MBA degrees from Georgetown University. He completed his internship in medicine and his neurology residency at Harvard/Massachusetts General Hospital. He was previously a Howard Hughes science fellow, and has authored several peer-reviewed scientific papers in the field of epilepsy, neuroimmunology, and neurodegenerative diseases.

Transcript:

David Cunnington: Thank you for joining the webinar as we discuss developments in treatment for genetic epilepsies. While this webinar focuses on SCN2A, the techniques that we are going to discuss are applicable for other genetic epilepsies and other conditions. This is the first of a series of webinars that we are going to produce and host from SCN2A Australia. With this series we hope to enable the families, researchers, and clinicians to hear directly from those working in SCN2A and genetic epilepsies.

After the webinar, a recording and transcript will be available on our website at SCN2AAustralia.org. You can follow us on Facebook or Twitter @SCN2AAustralia. We also run a monthly podcast, SCN2A Insights. So check that out for more information on SCN2A and genetic epilepsies.

For today, I have two speakers, Professor Steven Petrou and Dr. Kiran Reddy. Welcome.

Steven Petrou: Thank you, David.

David Cunnington: I’m going to ask Steve to start off. We’ve been really looking forward to your talk about SCN2A. So can you take us through what you are going to do?

Steven Petrou: Sure. Thanks, David. I will do that. I will just bring the screen up now. So what I would like to talk about today is our work in Precision Medicine in SCN2A epilepsy. But as you can see, there are a lot of parties involved in this, collaborators at university, companies, Ionis, RogCon, Praxis, and of course, University of Melbourne and the Florey. We are thankful to SCN2A Australia for arranging this webinar today.

So in that spirit, a lot of things have to happen in order for a program to emerge and a lot of things need to arise, a lot of technologies need to be present. You can see from this slide that it really does take a village to find a medicine. We start with the idea that there’s an urgent clinical need and we know for SCN2A that exists. We need to understand the genetic and disease mechanism landscape.

Family groups and natural history studies are a very important aspect of this. Understanding how the disease evolves in patients is critical to our ability to design future trials to think about therapeutic strategies.

Having disease models and I will talk about what they are in a sec and having ideas of what types of therapies might be best suited to a particular genetic mutation is also important.

And then finally and really critically for being able to deliver these outcomes to the patients is that you need the appropriate commercial and regulatory environments so you can understand how to operate and to deliver these medicines and hopefully see new therapies but most importantly, improve patient outcomes. And we are really driven by that.

This has been a 20-year journey to my research program from when we first started to try to understand how genetic mutations occur in epilepsy populations and what the mechanisms were and then could we identify opportunities for intervention?

So we are focusing today on developmental and epileptic encephalopathies and these are a severe form of epilepsy in kids. It’s more than just epilepsy and that’s really important to mention. It’s important to understand for those listeners that aren’t that familiar with this area. We see seizures but we also see developmental issues, slowing or even moving backwards, movement disorders, and overall, these children do have a hard time with their development and they can carry a poor prognosis.

Clinically, there is a spectrum. Some patients do differently than other as with many disorders. But in general, there is an obvious urgent clinical need across all of these.

What I’m going to talk about today is SCN2A which is just one of the many genes that make up this constellation of developmental epileptic encephalopathies. On the left, you will see some of the really enabling studies driven by teams from Australia, in the US, and around the world really trying to understand, trying to first gather patients, setting up mechanisms to be able to do sequencing in a systematic way. Epi4K was one of the programs that really enabled that and then started to deliver on knowing genes that are associated with particular cohorts of patients.

And you can see here, we would not go into the details into the genes but you can see the clinical diagnosis shown in each drop box. And within each of those boxes, there are the genes that have been associated with those syndromes. This overlap in some genes appear in more than in one box and that clinical and genetic heterogeneity is really what’s emerging for these group of disorders.

But if we look at this on a genetic basis, we can start to drill down to a single gene mutation in a gene and then we can start to understand, how do those mutations impact that gene? And it’s interesting that a genetic mutation may make a gene’s product, which is the protein, work harder but it may also make the gene’s product, the protein, work less. So that’s in broad terms we think of those as gain-of-function or loss-of-function disorders.

Because we are pushing this precision medicine concept, it’s important to know that and the sort sorts of therapies we think about devising driven by that particular genetic mechanism and then the consequent physiological changes that occur as a result of that.

The gene for today’s discussion is called SNC2A. It’s a really important brain gene. It’s largely expressed only in the brain. And then even within the brain, it’s only in the subset of neurons that are called excitatory neurons. And there are two broad classes of neurons in the brain. There are those that are inhibitory. They act like the brakes. There are those that are excitatory and they act like the accelerator.  Mutations in either of those types of neurons can give rise to these developmental and epileptic encephalopathies. In the excitatory neurons, SCN2A is the gene that’s most predominantly implicated.

In the inhibitory neurons, the counterpart is called SCN1A. And many of you may know the disorder called Dravet syndrome, and that’s driven – Dravet is caused by mutations in SCN1A.

And today, SCN2A like SCN1A is important in generating the electrical signaling of the neuron. Those electrical signals are called action potentials and there are specific regions of the neurons where those action potentials arise. And SCN2A is found to be enriched in those regions. So the region in scientific lingo is called the axon initial segment. It’s a very small part of the nerve or the neuron, and that’s where the electrical signaling is generated.

Now, if a mutation occurs in the SCN2A that is residing in there, it can cause a disruption in how that signaling occurs. Too much signaling generally is what we see in epilepsy and that’s why often the mutations we see cause a gain-of-function or an increase in the function of the SCN2A gene. And if that works too hard, the neurons work too hard and epilepsy being a disorder of electrical balance arises.

Not only does epilepsy arise as I mentioned before, but you do alter other functions such as cognition, movement, and other disorders can arise out of dysfunction of this gene but are not only occurring when the patients having a seizure but are present even when the seizures aren’t occurring.

Now, this slide speaks to the clinical spectrum which is sort of asking the question, in the patients that have had bona fide SCN2A mutations, how do they – what buckets, clinical buckets do they fit? There are four broad categories. There’s the early onset group, that’s those patients that present very early in life with seizures. That could be day one. It can even be prenatal. And they present generally at around birth with seizures and then the diagnosis, genetic diagnosis can be made.

There’s also a disorder called benign familial neonatal infantile seizures. It’s a bit of a mouthful. But that’s actually a disorder that’s inherited. The other boxes that we see there are disorders that tend to arise from new or de novo as we say, and that means there’s no genetic change in the parents but a random mutation occurs in the child and that’s the basis of the disorder.

BFNIS or benign familial neonatal infantile seizure is inherited and it’s milder, and that sort of makes sense because if you’re well enough to transmit the gene to make it inheritable, by definition tends to be milder. These seizures were the first type of epilepsy where the SCN2A gene was implicated. The change in the gene function tends to be more mild than the change in the gene function that we see with the de novo cases.

Both of those boxes on the left in the red cause an increase in function there, and that’s what they share in common. And the milder form self-resolves. The more severe gain-of-function doesn’t self-resolve and that gives rise to the two clinical presentations.

On the right-hand side, you see autism and late onset epileptic encephalopathy. Both of these disorders arise due to mutations that cause a reduced function in the SCN2A. Now, we don’t yet know why a reduced function can lead into autism or into the late onset epileptic encephalopathy and lots of groups around the world are trying to understand why a mutation takes you down one clinical path or another. What we do know with autism is that it’s clearly just the loss of function is sufficient. With the late onset cases, it may be a loss of function and some other change that we are not fully aware of yet that’s changing the clinical presentation.

But for today’s talk, I’m really going to talk about the left-hand box, about the early onset cases, huge clinical need, massive gain-of-function and the function of the protein, and that’s giving rise to our program.

It really starts with a really simple idea about what are the implications for how you might go about treating these cases. If you look at it from a very simple or helicopter view, well, if you’ve got gain-of-function in the genes doing too much work, if you reduce the function by even removing the gene product, that might reduce – have a therapeutic effect. In the other case where you’ve got loss-of-function, well then, you might need therapies that enhance sodium channel function.

So if we focus on the orange box, which is today, what are the standard ways we think about reducing gene function? Well, we all know about normal anti-epileptic drugs that you take orally. A lot of those drugs act by interacting with sodium channels such as SCN2A and they simply block the functions. So when you ingest the drug, the drug finds its way into the brain and interacts with the sodium channel, stops at operating as well and that can be somewhat beneficial.

We know for these patients that a particular drug called phenytoin is the most effective out of all of them for the patients but it still doesn’t have a transformative effect on them. It may reduce the seizures but it doesn’t improve any of the other comorbidities. So we know that we need that we need to do more. We need to be more specific. We might need to have a stronger effect.

The way that we thought about is can we simply reduce the amount of SCN2A gene function by reducing the amount that’s produced of the protein? And I will show you what I mean in the next slide.

For those of you that aren’t aware, there’s thing called the central dogma of molecular biology and that is how genes can be thought of as the blueprints of life. Genes make an intermediary molecule called RNA. So from DNA of which our genes are comprised, we make an RNA and that RNA then makes the protein that does the function.

At each of these levels, there’s an opportunity to intervene therapeutically. Most small molecules we take orally that are available today tend to interact with the proteins. Gene therapy where you deliver entire genes, acts at the gigantic level, the DNA level. What I’m going to talk about today are molecules that act at that intermediary level of the messenger RNA. And so it gives you an ability to modulate the amount of the message and that could then determine – you can see here in a normal situation on the left, if you’ve got lots of messenger RNA, you produce 4 copies let’s say of the channel, if you can somehow modify on the right the amount of the messenger you make, you then reduce the amount channel you produced and that’s the desired therapeutic effect that we want. So the question now comes, how do you make a molecule, here shown in yellow, that can reduce the amount of messenger RNA?

So we do that with a class of molecules called antisense oligos. What are they? Well, they are modified forms of the natural DNA that occurs in all of us. And they modified so that they bind tighter to the messenger RNA and that they are resistant to degradation. So if you want to take a drug, it’s really important that the tighter it binds, the less drug you need. And because you want less drug, you limit the ability for toxic effects of having to take vast amounts. That’s really important. And you want the drug to last.

Antisense oligos in these sorts of applications tend to be delivered by spinal injection, called intrathecal injection. You don’t want to be doing that weekly or monthly. You want to be doing that as infrequently as possible. The chemical modifications you make to these molecules enable you to inject these drugs three or four times a year giving you a good therapeutic approach.

A famous antisense oligo that you may have thought of or heard of is called Spinraza. This therapy was used for a disorder called spinal muscular atrophy and it’s really transforming the lives of these kids that are taking this medication. This is just one graph showing these two groups here. You can look at the early analysis of this program.

Sham controls a patient’s that didn’t receive the drug and you can see there are milestones – the number of patients that reached a certain milestone was zero. And you can see that in a group that was treated, 41% of those treated reached these motor milestones. And that number only got better by the end of the study.

There have been numerous follow-up studies now on this program and some kids almost being able to get out of their wheelchairs and walk. So it has transformed the lives of these kids. This is antisense oligo molecule as I mentioned. It’s injected intrathecally three or four times a year in these patients.

Now, the idea that we had for SNC2A is, could we use a similar technology to reduce the amount of SCN2A and would that have benefit?

Now, we only want to do that of course in those cases that actually have true gain-of-function. This is one way we analyze a mutation from a patient to understand whether or not it has got the right type of mutation and then we can attach the right type of therapy to it. And these experiments show how we model this in a dish. So these are mutations that we express in cells. We can attach these cells to a computer in real-time and we can ask the question, well, if a neuron had this sodium channel in it, how would it function? And you can see here, the black at the top is how a normal SCN2A channel would operate in a neuron. At the bottom, the mutation is in the SCN2A and its designation is R1882Q. And you can see how much increased activity. Each of those upward spikes is that electrical event I mentioned before called an action potential. We can see how much more activity there is in that red mutation, than there is in the control black group. That’s something that we think is a major reason why the neurons fire the way they do in epilepsy and give rise to all comorbidities. If we can do something that dampens the activity of the neurons, we can then have a chance of reducing the severity of the disease.

That data I showed that was done in a dish, we have also recapitulated that by actually taking skin samples from patients. And you can take skin cells and you can turn them into a thing called a stem cell and that’s a very primodial type of cell that can then be instructed to turn into a neuron. And this way, we are asking the question, if we look at a stem cell from a patient in the pink and we compare it to the same cell with the genetic mutations being repaired, you can see that the difference in electrical activity shown here, the red versus the black is quite marked. And that shows our in dish essay really replicates what we have seen when we look at patient material that’s starting to give us confidence that we can start to predict which patients are going to be candidates for this disorder and we couple that of course with the clinical knowledge we have of these patients and then we start to categorize which patients are going to really match the therapy we are trying to develop.

So next it was really important that we show that the antisense oligo can work in a mouse model. This is sort of enabling activity that gives us the confidence. It gives the commercial partners that are involved in these programs, the data that they need to start to think about the large scale investments and risk that’s needed to take an idea from the bench into an actual commercial development. And that’s a big step. And so, part of our goal as researchers is to really provide the most compelling case for that so that we bridge that divide between the idea and the product. And I think a lot of researchers are acting in that space.

Now, the antisense oligos, how do you know they are working? And so the antisense oligos are small string of pearls essentially with about 18 to 20 of those nucleotides in a row. You inject them into the mouse brain and then you want to know whether or not you have affected the amount of the SCN2A gene protein that’s expressed. We do that with a method called immunohistochemistry. And essentially, we can make that protein turn green with a tag and then observe it under the microscope.

If you look on the left, you can see that protein being detected as these green squiggles in the brain. Those little squiggles are the axon initial segments in those neurons. And if we treat the animals with an antisense oligo, wait a week or two, and then observe with the same method those axon initial segments, you can see how much depletion we got on the right. And this shows us that not only is the antisense oligo acting on the messenger RNA that we can measure with another method but we’re actually affecting the amount of protein that’s in the brain. So we can test our hypothesis now, does that reduced amount of protein impact the behavior of the mouse in a useful way?

And this graph shows what the mouse so – so we developed the mouse that has got the mutation in it, the same mutation that we found in a child that presented with a severe form of epilepsy. And in the black, you can see these mice died of seizures after about 20 days. So if we put 10 or 20 mice and we observed them over this period, after about day 15 or 16, the seizure severity increased. They had worse and worse seizures and then by that day 22, 23, they had all died.

This gives us the ability to measure the effect of a drug. So if we treat the animals now, can we see whether or not their survival improves? And the first experiment showed here when we delivered the antisense oligo that we could extend their lives and this is just different doses. So here, we gave an antisense oligo that reduced the amounts of messenger RNA by 50% and you could see an extension in the survival of those animals. If we increase that dose to an 80% reduction, we got a further reduction in mortality of these animals.

Now, we would like to see of course a 100% survival. And because when you inject these animals, they are going through a very critical – and bear in mind it’s a single injection at day 1 of life that then has that enduring impact as I said about the ASOs. But also in that period, these animals are going through really important periods of development. Their brains are growing. There are many, many changes occurring. So we did an alternative protocol where we gave an initial injection and then we did a booster injection at a later age because that way, it’s hard to treat an animal that weighs one gram at day 1 and then it’s 18-20 grams at day 25. So the dosing  are all disjointed.

If we compensate for that and give a first injection and then a second follow-up injection at about day 15-20, what you can see here is that we can achieve 100% survival. So we can get those animals over those periods.  In gray, what’s shown here, these animals only received the first injection and didn’t get the follow-up injection. They eventually died but then these other animals that received the second injection later in life showed remarkable survival at two different doses that we tested.

So this shows that we really can sort of get that right balance between dosing to reduce the effect and then not overdosing and causing any toxicity. So we can achieve that beautiful sort of goldilocks situation where we can dose, reduce the seizures, but not overdo it. So this is a really important result to show that you can transform the phenotype in these mice. In this period, the animals not only weren’t dying but their overall health, the number of seizures, lots of things we vastly improved.

Now, because we thought – if you go back to the genetic mutation affecting the function of a neuron, we want to know whether the treatment is also fixing the properties of the neuron. That is a consistent finding with what our hypothesis is that by reducing the amount of SCN2A, we are correcting the genetic defect at its most fundamental level because if we want to stop seizures, we want to improve cognition and movement and all the other comorbidities, we need to correct the mutation and the functional consequence at its most fundamental level.

And you can see here on the left, this is from a mouse model where we measure the properties of the neurons and we simply excited the neurons with a bit of electrical current and we saw how much activity they gave. And you can see here as we increase the exciting current, the neurons fire many more times per – this is per one second period. And you can see here they fire up to 20 times, 30 times in that one second period.

And in the animal with mutation, for any given level of current step, many more action potentials were fired. So these neurons are hyper excitable in the way that I showed you before with the stem cells. So we are recapitulating that. We also now have the ability to ask the question in these mice that were treated that showed a reversal of the mortality phenotype, what happens to the neurons? And remarkably, what you can see is in the animals that were pink, that were treated, they moved to the blue line. So following treatment, they now are on the blue line which completely overlaps the black/white and where the control group was. So we think with this treatment, we pushed the animals neurons back into the wild-type or control group functioning mode and that’s probably the basis for the improvements that we are seeing in the mortality.

Finally, we asked the question about the seizures in these mice. And if you look at that, we saw a massive reduction. This is an animal that received a version of the ASO that we called a scramble or a control. It doesn’t actually engage the SCN2A. If we control for the effect of ASOs in general. You need to do that in these scientific experiments. And you can see here that following treatment, we got zero seizures in this group. This is just mid-dose and a very high dose, we can essentially reduce the seizure counts to nothing.

At the older groups of course, the animals weren’t alive so we couldn’t measure there. But that affect the system. We weren’t seeing seizures. When we looked at the EEG of these animals, one of the other things you often see on an EEG in these animals that have got genetic mutations, is lots and lots of activity on EEG, even between the seizures, that’s called interictal. And we can see here, for all intents and purposes, the EEGs from the treated mice looked like the control mice and we weren’t seeing any untoward activity on these EEGs which is again, another marker that we think we are really achieving fundamental changes in this disorder at lots of different levels.

So I’ll end there. And I’ll end with three summary points. One is that ASO oligonucleotides might be a therapeutic approach for a large subset of these SCN2A epileptic encephalopathies. I think things are looking really good for that. This project has been transferred to commercial partners who are looking at development of this as a product and it’s a whole new process now going forward. We know the mice worked well. And even more generally speaking, this class of medicine is really very well-positioned to impact a lot of different genetic mutations we are finding in these sorts of patients and in other patients afflicted with genetic changes.

What I didn’t mention today was that ASOs not only can be used in a mode that alters the amount of that messenger RNA but they can be used in other modes that can increase the level of function of a gene or they can alter the function of the gene by altering what we call splicing. So there are very sort of diverse set of actions we can expect out of ASOs that positions them well to target these brand new genetic disorders and I feel that moving ahead into the future we are going to see many, many more examples of these ASOs impacting our patients.

I’ll hand over to my colleague, Kiran Reddy from Praxis to mention where Praxis is moving in this space.

David Cunnington: Thank you, Steve.

Kiran Reddy: Thank you very much. And I thank you Steven and thank you David and SCN2A Australia for the opportunity to be able to tell you about Praxis Precision Medicines and what we are doing in collaboration with a number of groups, certainly, the Petrou Lab and the Florey Institute. We’ve been working with a biotech company called RogCon as well as Ionis Pharmaceuticals. And based on the really beautiful work that Steve just went through, Praxis Precision Medicines, a biotech company based in Boston, Massachusetts in the United States. It was focused on developing medicines for brain disorders and when we saw the work that had been done focused on SCN2A gain-of-function mutations causing developmental epileptic encephalopathies, we were extremely impressed by the promise of this approach, of an ASO-based treatment approach for SCN2A gain-of-function mutations. And our expertise as a company is in the development of medicines, novel medicines for brain disorders. We’ve got an excellent team to do that. And thankfully, the Florey, RogCon, and Ionis have trusted Praxis to take on the clinical development of this exciting new medicine, this antisense oligonucleotide medicine for SCN2A gain-of-function mutation.

So let me tell you a little bit more about Praxis and some of the team just so that you are familiar with it. As I mentioned, our mission as a company is to discover, develop, and deliver new medicines for patients with brain disorders. We are very committed to the area of genetically defined pediatric epilepsies and are working pretty intently on this area.

In addition to myself, I’ll just highlight a few people that hopefully you will start reading as we develop this medicine for SCN2A. Bernard Ravina is our Chief Medical Officer, neurologist by training. You will hopefully encounter Gabi Belfort who is the Lead Medical Director on this program and both of them as physicians and neurologists have extensive experience developing medicines for brain disorders. And then Jennifer Burg is our Head of Clinical Development Operations, has a pretty extensive experience in developing medicines and worked in pediatric medicines and setting up those clinical trials globally as well as setting up not just clinical trials with new medicines but also natural history studies. And in addition to our core team here at Praxis, we’ve got some wonderful advisors, David Goldstein in addition to Steve had been a wonderful founding advisors to us as a company. Al Sandrock who is the current Head of R&D at Biogen Therapeutics that had developed Spinraza in collaboration with Ionis who is on our Board of Directors and Ed Scolnick who was the President of Merck Research Labs. He is also an advisor to us working on developing the medicines that we are developing at Praxis.

I’ll go to the next slide. I will go through the information on this slide but the molecule RC-222, that program is the program that we, Praxis, have brought into the company from Florey, from RogCon, and Ionis. Those are our collaborators that we are working closely with them but taking the baton on to this molecule development.

Steve just went through the beautiful pre-clinical data. Right now, we, as a company are in the design planning stage for a clinical trial for this medicine, RC-222. For this year, at the end of this year, for much of 2020, we will be completing the requisite safety data requirements in animals for this molecule. We are doing that as a I mentioned in collaboration with the Florey, with RogCon, and with Ionis.

We expect to soon be able to provide some detailed timelines for when we will initiate clinical trials with this medicine. We are actively working with SCN2A Australia, with Families SCN2A group in United States as well as SCN2A groups in Europe around how to appropriately design and develop this medicine for patients with SCN2A gain-of-function mutations as well as understand how we can move natural history studies along that will allow us to appropriately compare how this antisense oligonucleotide medicine can help patients and how can compare to what maybe the natural progression of an SCN2A gain-of-function mutations.

As I mentioned, we will by the end of the year have a community statement that we will circulate to SCN2A Australia, Families SCN2A and other groups around the specific timelines for how we expect to advance this medicine into clinical trials. So please stay tuned. More information to share. We, at Praxis, and I know the Florey, RogCon, Ionis are very excited about the opportunity to help patients with SCN2A gain-of-function epilepsy and look forward to working with the entire community. We recognize that we cannot do this alone. We need your partnership, your engagements, please.

We will certainly make sure that our contact information at Praxis is available. We are eager to engage with families and with patients about what we are trying to accomplish with this program and look forward to an opportunity to shortly give you more information about how we are going to advance this molecule into clinical trials.

David Cunnington: Thank you very much, Steve and Kiran. Congratulations. Great job bringing all these partnerships together. It’s really exciting. There are going to be barriers and going to be things pop up. So what can we as communities, clinicians, researchers be doing to break down those barriers to help move your program forward?

Kiran Reddy: Thank you for asking. And we certainly – we welcome any help that we can in terms of developing medicines. I’ve been working in the field of drug development now for over a decade and recognize that it is not simple to develop a medicine and bring it to market and have be accessible to patients. We think we have an incredible opportunity here based on the science to develop this antisense oligonucleotide for SCN2A gain-of-function epilepsy but we need help.

Absolutely to your point that we – what I will say however is that I commend the community for what it has already done. I mean the SCN2A community has moved further along in ways to break down barriers and I have worked in other disease areas where frankly, nothing was available. Patients and families were not organized. There wasn’t a great network of clinicians working on SCN2A and there weren’t really thoughtful efforts to try to advance how to think about clinical development.

So what I will say is that thankfully, the field in SCN2A has done a remarkable job. And so yes, things can certainly further evolve but I think about what is there today, which are families that are organized, and that’s wonderful for us to be able to – be able to speak to families and organizations and ask, what are the important issues that your children are facing that as we design the clinical trials would be critical for us to understand how are we going to know whether this medicine is actually working and helping patients. And we need the input from families around how to appropriately find the right endpoints to build into our clinical trial. So that is certainly one area that we can – that we will ask the community for help.

Thankfully again, some of that work has already been on going, that’s also because of the community’s efforts to organize the clinicians, the pediatric neurologists and the other care-givers working in this particular area that are now talking to each other and discussing what are the right endpoints to design in building the clinical trials. How can we build centers of excellence? What will be pretty critical for us as we move forward and initiate clinical trials that we can identify groups across the world that are able to thoughtfully perform clinical studies with this medicine.

And this is antisense oligonucleotides so there are certainly centers that are able to deliver those medicines. But it’s beyond delivering those medicines, it’s also knowing enough about the patients, having enough experience taking care of SCN2A patients, that will be critical. And also experience with the measurements beyond seizures measurements, I mean that is more common and many groups are able to understand how to perform EEGs and do seizure assessments. But the training requirement to be able to perform the non-seizure endpoints will be critical and we are beginning those conversations with a number of these academic centers of excellence around how they are training their staff to be able to perform these particular things.

David Cunnington: That was one of the things that came through – one of the takeaways when you and I spoke for the podcast was about that importance of having a local nidus where families, researchers, and clinicians are working together that allows the team like Praxis who is running a clinical trial just come in to establish infrastructure and ready to go without having to spend another couple of years doing it from the ground up. Plus at the other end, hopefully, there’s a good clinical trial success when you come out the other end looking for a regulatory approval and reimbursement, it’s going to be that local and in-country expertise that’s going to be needed to get that up and going as well.

Kiran Reddy: Absolutely and I would say that thankfully, we are in a pretty good position in that there are a number of wonderful academic centers that are developing a growing experience set. I hope that with some of the efforts that are going on globally around initiating your registries and natural history studies, that experience will only further mature. And Praxis is very much wanting to participate in efforts to further natural history studies. So these – or the other way the community is describing this are clinical trial readiness studies. They will be able to help us understand how or what is the progress of the patient over 6 months, 12 months, 18 months and then have a good understanding of whether those patients would qualify for a clinical trial that we are initiating.

So those efforts will be – some of them have already started. I see 2020, next year, as increased activity for those natural history studies in SCN2A, clinical trial readiness studies, the community, I have already seen is they are quite actively engaged in the planning phase. And that is imperative. If we want to be able to start clinical trials, we need these sites well-prepared. We need to know where are the patients and they need to understand all of the issues involved with clinical trials so that we can move fairly quickly when this medicine is ready to initiate clinical trials. And one of the things that we would love to do next year is more education for families to understand what does it mean to be in a clinical trial and what – depending on the details of the clinical trial, it’s pretty important that that be well-understood and so that when we can get started, there’s not a long process of education for whether a family feels like it would be worthwhile for them to participate in a clinical trial.

David Cunnington: So Steve, you did a great job of outlining what an ASO is. Can you talk us through how it differs from gene therapy?

Steven Petrou: Right. I mean sort of it is a form of gene therapy but I think when people say gene therapy, they often think of a different thing and that’s often a gene replacement where a virus vector is carrying a fresh copy of the entire gene and that’s inserted into the genome of the patient and then that new function you get from doing that is the therapy. That’s a more difficult task for some of these large genes like SCN2A to do that. But there are other forms of gene therapy that might be fixing like you heard of CRISPR technology. I think everyone is talking about that. That’s a form of gene therapy that might go in and actually repair the initial genetic defect. And each of these – they are all classes of gene therapy.

ASOs have undergone 30 years of development. Hats off to the work of Ionis for pioneering this field and Dr. Stan Crooke for really believing in this technology. And it’s only recently that the benefits of that are beginning to emerge. But each of them is a form of gene therapy and probably for these sorts of disorders, ASOs are the best poised today and maybe for the next 5 to 10 years of the molecules. The other therapies may eventually start to replace these and supplement them but we don’t know yet. With respect to rolling things out as soon as possible, we have an imperative and we are trying to act quickly.

David Cunnington: Do you think – to hear about just how long it took you, you said it was 20-year culmination of your work on channelopathies.

Steven Petrou: Correct.

David Cunnington: So from the time you as a scientist might have an insight to then you get to the point you’re at now where you make commercial partnerships to think about the commercialization, how long is that?

Steven Petrou: I mean it is, it is a long process and you don’t know. I mean 20 years ago, I didn’t predict that I would be doing antisense oligos for rare neurogenetic disorders. And what sort of happens is it’s all like a perfect storm. I mean a lot of things collide at the same time. The technology of ASOs was exemplified beautifully by Ionis and Biogen for spinal muscular atrophy. That shone a light on that particular approach. And then epi4K and the other genetic studies had evidence that of what was driving these rare neurogenetic disorders. Our ability to make rodent models, mouse models worked better with the CRISPR technology helped in the production of those so we could more rapidly produce models. So everything converged and the opportunity arises from that convergence of all these different independent things that happened.

So – and without that 10 or 15 years’ work leading up to that, that moment wouldn’t have occurred at that time. And it may have occurred 5 or 10 years later. So it really was a very incredible opportunity when all these things came together then we saw with all these things happening, this is the way we need to move with this.

David Cunnington: And it does highlight that if people think, “Oh well, I want to hold out for the ideal treatment,” they might be holding that for quite a long time.

Steven Petrou: That’s sort of my feeling as well. I mean we act in the here and now and there are things that we can do here and now and I think antisense oligos, some gene therapies are irreversible. That’s an important point I didn’t make before. That you deliver that gene vector into the body, it stays there permanently. Antisense oligos, you deliver them – they last a long time but they eventually get degraded and metabolized and eliminated from your system.

So in many ways, you can think of antisense oligos as having many of the good qualities of a gene therapy but not having been locked into generation one of a therapy. And I think that’s the really good aspect of them. So I think that that’s important to understand.

David Cunnington: Yeah. Thank you. We talked about gain-of-function. And this is all about the gain-of-function the program. And you alluded to the fact that ASOs can be used to turn down production as well.

Steven Petrou: Correct. Some of the parents and other people may be aware of a company called Stoke Therapeutics. They are working hard on a related disorder I mentioned called Dravet syndrome. In that case, the disease results because of too little SCN1A. So the brakes don’t work well enough. And then the therapy idea there is can we make more?

Well, they have exploited a genetic method to increase the amount of messenger of RNA. And you can use an ASO to do that as well. So ASOs, depending on the chemical sequence in them and the modifications, can either cause a degradation or they can change the way a gene is assembled. And if you can change that assembly process, you can make more of it. And that’s what Stoke is doing in their particular program. And so, the ASOs, because of that diversity of mechanism are an amazing sort of class of molecules.

David Cunnington: And is there work going on in the SCN2A loss-of-function?

Steven Petrou: Yes. There’s actually lots of thought going in to SCN2A loss-of-function. SCN2A is the most common genetic mutation known as the cause of neurogenetic disorders. So because of the group of patients with autism that’s far and away a very large group, they have mutations in SCN2A that cause loss-of-function. So that makes it a very important class of disorder. So there are lots of thought around how we might increase the function of that gene either through an antisense oligo or a small molecule or a classic gene therapy approach.

David Cunnington: So I would like to thank you both very much for your time today and for outlining the work you’ve done, Steve, the 20 years of work which really culminated into this and best of luck for the work you are doing and what you’re going to bring Kiran with Praxis and hopefully developing a specific SCN2A treatment.

Steven Petrou: Thank you, David.

Kiran Reddy: Thank you very much.

Steven Petrou: Thanks.

David Cunnington: Thank you for your time today. The recording will be available on SCN2AAustralia.org. Follow us on social media @SCN2AAustralia. Thank you.

 

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