A Solution for Duchenne Muscular Dystrophy? — In Depth Doctor's Interview

Talk to us about where we are right now with personalized medicine.

Dr. Hoffman: Personalized medicine there's different embodiments or sort of definitions to it. There's some in current use particularly with regards to drugs. So if you take some certain drugs certain people respond very poorly to. Based on how we metabolize them or don't metabolize them, how long the drug stays in the body. So there are now genetic tests that you can make sure you're giving the right amount of drug to the right patients. So that's a from of personalized medicine and that's been around for a couple of years. It's pretty tough it's only a couple of drugs that we really understand enough but it's already underway, particularly in chemotherapy, it's one of the key areas. Personalized medicine more broadly and in terms of drug development you can get more specific that a drug is designed specifically for a patient and even developed specifically for a patient. And that's sort of more a forward thinking definition of drug development is what we're working on here and is now heading in to clinical trials, or in clinical trials. So it is actually advancing quite quickly but it creates a lot of challenges too as we develop these drugs.

So this is more for particular individuals not just for the group that metabolizes the drugs in a certain way?

Dr. Hoffman: Exactly, in this case which is called axon skipping or systemic antisense we're designing drugs that will go in and repair a patient's DNA problem in a way. So many of us are patients with Muscular Dystrophy, it's a Duchenne Muscular Dystrophy is what we're focusing on, which is the most common rare disorder in the world pretty much. Different patients have different problems with their dystrophin gene. Dystrophin is a protein I identified about twenty five years ago and so because of that we can't use one drug to fix everybody's gene. We really need to understand what's wrong with each individual patient's gene and then use a drug that's just targeted to that patient's problem. So in many respects it's like nanosurgery we're making a drug that will go in to the muscle throughout a patient and do a repair on the RNA so the patient can now has a more functional gene when they didn't before.

Can you describe that analogy about going in to the muscle?

Dr. Hoffman: What we're doing in the case of this new therapy for Duchenne Muscular Dystrophy which is the most common of the rare disorders internationally is to design drugs that will go throughout the body in to the muscle of a patient and really repair that patient's own problem with their gene. So we have to design the drug specific for the patient's genetic problem. In this case the dystrophin gene is the largest gene known, it's about two and a half million letters of code, so different patients have different problems in the code, all throughout the code. So we have to design the drug to go in and fix that patient's coding problem. So fix the text of the gene in that patient and that's the drugs we're developing.

How do you do that when there's so many variations?

Dr. Hoffman: The short answer is it's hard so it's going to take a lot of work and it also challenges the whole regulatory programs of the government. To just sort of take an extension of this approach if the Duchenne patient he's really the only one with that that specific change and there's many Duchenne patients like that, then how are we going to do drug development for one patient. How are we going to do a Phase III trial with hundreds of patients when there's only one of them. We can't clone three hundred of that patient to do a trial. So we really have to work with the regulatory agencies, certainly show that this approach is safe and effective. But once you have done that how can you keep a drug that you know will work away from a patient even if it's designed just to that one patient. So it's a challenge at many steps of the way. The first drugs in this approach that we're working on are towards the more common gene mutations within the Duchenne population. So there's a couple what's called hot spots so about ten percent of patients, one in ten, have a similar enough mutation that we can probably treat it with the same drug. So that's the first drug in trials now which is called the exon51 it's done by both Pursenza and GSK Alliance in England and now spreading throughout multi site clinical trials in many countries. And also we're working here on developing an exon45 drug which would be the next most common type of mutation.

So this drug goes in to repair the DNA in that mutation, what could the patient expect as an outcome?

Dr. Hoffman: First I should clarify that we're not changing the gene itself. That gets a little scary because that sounds like genetic engineering and once you have done something to the DNA it might be hard to reverse it. What we're doing is there's three steps in any gene helping your body work. So the DNA is just a cookbook then each gene in certain places in your body at certain times gets made into and intermediate called an RNA and that RNA is then made by the cell. And the protein and protein is what you're looking at. I'm looking at the protein of you and your eyes are using the eye genes to make the eye RNA and making the eye protein and you skin is using different genes and your toenails are using different genes. The dystrophin gene which we're working on is a gene pretty much specific to muscle, we all have this and it's not working in patients. So they have mutations and they can no longer read the recipe and decode it because they have part of the code messed up. The analogy I often use is with joy of cooking a cake. If you look up the recipe for a cake which could be in this case dystrophin a component of muscle you have the recipe but you don't eat the recipe. You then get all the ingredients, mix it up in a bowl, you have the batter and that's RNA. So you don't eat the RNA, you don't eat the batter you then cook the cake and that's the final cake that you eat and that's protein. So DNA is the cookbook, RNA is the mix and the cake is the protein. What we're doing with these drugs is we go in to the mix, we say okay the gene is making this RNA as an intermediate we're going to go in and repair the intermediate so the code is fixed or made better in the RNA. And that actually is better in many ways because we're not irreversibly changing somebody's genetic code we're really going in and helping the gene make due with what's left of the gene. So we're making the recipe good enough that it can still be baked and cooked in to dystrophin which is now a component of the muscle.

What could the patient expect from this, what would be the outcome for the patient?

Dr. Hoffman: Our best evidence of that to date is using dogs which owners have brought in which have the same disease. This disease Duchenne Muscular Dystrophy is the largest gene known in any organism anywhere and it's similar between mice and dogs and cats and us and all organisms. They all have this gene which is supposed to make dystrophin which is supposed to be a component of muscle. So because of the large size it has a high mutation rate which is knocked out much more frequently than other genes and that's why Duchenne Muscular Dystrophy is so common relative to other genetic diseases. Well it turns out to be equally common in animals as well. So cats get their gene knocked out, dogs get their genes knocked out, the dystrophin gene, so owners just bring in a dog that shows weakness. We can do tests and say this is Duchenne Muscular Dystrophy. So what we've done is take some of those dogs like Golden Retrievers or Beagles in this case that had Duchenne Muscular Dystrophy. Those dogs are much more severe than human patients. They often die at birth or often get weak and die within six months. So what we did was make a specific custom drug just for the dogs, we injected in to their bloodstream and dogs that would have died and not been able to walk now can run. We only had enough drug to test three dogs it was very complicated. But each of those three dogs stabilized or got better by any measure we looked at. Whether it was MRI imaging or how they could eat or run or how their muscle looked under a microscope and that's the only type of therapy that has worked on the dogs. Everybody has tried other types of therapy and couldn't get the dogs better because in part they were so severe but this approach did work. So I think that's the best evidence to date but the human trials are obviously the most important to continue that and prove it in human patients.

So the goal is to at least stabilize the muscle?

Dr. Hoffman: If we look at the three dogs everybody is very optimistic that we'll at least stabilize if not make patients considerably better. This depends in part on how much muscle the patient has left. I mean if a patient is already in a wheelchair with very little muscle left in their body it's going to be hard to bring that back. The current feeling is the younger we go and in that case the more mild the patient is clinically or less severely involved in the disease the more we will protect them and preserve that from later problems. So our goal is to go younger and younger even to neonate, even five years before a patient shows symptoms we should start this treatment.

How early can you diagnose this?

Dr. Hoffman: We can diagnose this almost at any age. We can diagnose fetally through genetic tests, we can diagnose this at birth through neonatal screening of a blood spot. Because we see lots of muscle guts in their blood their muscle is leaking. Even from birth even though often the patients don't often show symptoms for four or five years. In fact if this therapy is shown to work which we all expect it to be over the next year or two then most countries will probably start neonatal screening for Duchenne as part of the standard neonatal screening of all diseases. Your blood spots that babies have taken. In fact we just got a grant from the government together with the University of Utah to re-evaluate the whole neonatal screening programs to make sure the infrastructure is there that we can start those again once the therapy is available.

So once the therapy is available and the screening goes forward then at infancy they can take the drug and keep everything going the right way?

Dr. Hoffman: Exactly.

It's got to feel good it's not like you've been working on this for a long time.

Dr. Hoffman: There's a lot of people internationally and what's very nice is I was involved in the original identification of the gene and the protein back twenty five years ago. Back then it was a prototype of how internationally scientists and stake holder communities and patients could all work together to achieve that goal. Which was the first human disease gene identified by the sort of genetic engineering back in the late 1980's. Now as we turn to using those tools to do therapeutics we couldn't do this personalized medicine without having the gene in hand. Now that we've had twenty five years of slugging away we have this new therapy that looks most promising by most people's assessments and that again is an international effort. Really laboratories throughout the world really pulling together, family organizations we're working with family groups in Australia, throughout the world to bring this to as many patients as quickly as possible as we can.

Do you have any idea how many years this could add to a lifespan?

Dr. Hoffman: At this point it's going to be hard to predict, I mean you can play out different scenarios. One way we sort of can predict that is we can find patients walking around with a fixed dystrophin gene. In other words a mutation in the gene which still allows the gene to function and put together what's left. So these patients are still making some dystrophin but it's not normal. Those patients are exactly what we're doing with this personalized drug approach. So we can say those are our outcome that we expect. What's important here is that we see quite a bit of variability with the same genetic problem where they're still making dystrophin but it's not quite normal. Some patients are extremely mild and don't even show any symptoms, we have families in Italy that are full time farmers and even grandpa doesn't show any weakness at all. Yet he has this mutation in this dystrophin gene. But with that same mutation we find other families and other patients that are quite severe. So we need to understand why does this variation in response and in fact the US Government just gave a large grant to a collaborative group again from here and overseas to really try to study that and see what are reasonable expectations from this personalized approach. And if this variability between patients responding and not responding so well why, and can we fix those. Can we either predict who is going to respond or try to compensate for those that aren't responding as well to the same drug.

Is Dr. Winn's son in the trial?

Dr. Hoffman: I don't know of his son is enrolled at this point. He is in Australia and he and his wife contacted us. He is a physician, an endocrinologist and he contacted us and it's a good example where a stake holder group in the United States supported his salary here so that as a parent he could also be both a scientist, a physician and a parent working on these therapeutics. So he just arrived about a month ago but we're very excited to work with him on these therapeutics. There's two different drug programs we're working on here and I think he's mostly in the second one which is one we haven't talked about.

Tell us about that one.

Dr. Hoffman: The second drug development program which we're also very excited about, in part because it has very wide reaching applications beyond just Duchenne dystrophy. It has to do with the use of what's called glucocorticoids, or steroids. So steroids many people have head about their use, they're used for asthma, lupus, arthritis, there's so many disorders where you take these glucocorticoids as standard of care. And in fact in Duchenne Muscular Dystrophy glucocorticoids are currently the only drug that is used. So patients with Duchennes take glucocorticoids every day and it does it makes them stronger, it makes them walk a bit longer but it also comes with a lot of side affects. It comes with bone fragility, stunting of growth, mood changes, adrenal suppression, endocrine disruption, a lot of side affects. In fact a local family here their son with Duchenne ended up in a wheelchair not because of the disease but because of steroids. Because the steroids made the bones so brittle that they broke bones and couldn't heal. So one, we need to understand why steroids are working and can we make them work better and two, can we get rid of the side affects so we think we've accomplished that over the last few years. So we have this new drug development program spun out of Children's Hospital here in DC that has made a new series of drugs that seem to increase the efficacy and lose the side affects. We've manipulated the structure of this and the US Government, the NIH, just appointed this as one of just two or three drug programs in the country that they feel is the most promising for any rare disorder nationally. And so this is called BBP15 the company is Reveragin partly owned by Children's Hospital and that's what Tony is working on. Looking at both the endocrine disruption, because he's an endocrinologist, looking at what glucocorticoids do and what these new drugs do or don't do and he's also very excited about that program.

BBP15, that's the new drug?

Dr. Hoffman: That's the new drug that we're taking to human trials now.

So it has implications for all rare disorders?

Dr. Hoffman: Right because BBP15 we're learning a lot about steroids and why they're working. Just a bit of background which I find fascinating, the Nobel Prize in 1950 was given to a team of physicians because they found if they took cortisol, cortisol is your stress hormone and it's involved in your day-night cycles. So every morning at four a.m. your cortisol levels go through the roof and helps you wake up. And then they crash in the afternoon and you're looking forward to getting out of work and dinner. And this defines your whole day-night but it's the same hormone that defines stress. So if you're stressed out by something your cortisol levels go up. These scientists back in 1950 noticed that if you took cortisol and by chance gave them to an arthritis patient who was suffering from arthritis they magically got better. So they just starting trying cortisol with everything and lots of people with sort of inflammatory conditions were getting better. So it became standard of care back from the 1950's sixty years ago to this day where glucocorticoids are standard of care in many, many disorders. But they haven't found drugs that work better and they've never really understood why they worked to begin with. So what we have figured out by developing these new drugs is we've been able to peel away the layers of the onion and really figure out why glucocorticoids are working. And it turns out to be so obvious and so simple. People have called them forever, the last fifty years, anti-inflammatories, what we figured out is they're not anti-inflammatories. Really what they're doing is they are a pharmacological dose of day-night, your whole body needs those cortisol rhythmus to remodel itself. When you're resting at night your lung is replacing itself your tissues are regenerating and that's why they say you need your sleep. Your beauty sleep is real, your body is repairing itself that repair system is set up by cortisol. So it's all synchronized, your whole body is synchronized to rejuvinate by this day-night cycle. What we're doing with glucocorticoids and these drugs is giving a boldness of day-night, it's like boom, body it's day now it's night. You don't have any choice about that. And by doing that it's re-synchronizing the lung for asthma, it's re-synchronizing the muscle for Muscular Dystrophy, for all these parts of the body that are struggling with a problem it's saying, you're re-synchronized, you're rejuvinated now repair more effectively. The immune system just goes away because it's not longer needed so they're anti-inflammatory because the tissues themselves are repairing better. So because of that new understanding we've been able to design drugs that just target that sort of pharmacological day-night and get rid of all the side affects. And that's why BBP15 looks very promising in every system we've tested from asthma to arthritis to skin disorders. So while this BBP15 was done for Muscular Dystrophy and will be first in humans in Muscular Dystrophy it looks quite promising for many disorders.

What are some of the other disorders?

Dr. Hoffman: Arthritis, lupus. MS, skin disorders, I mean you've probably given it to yourself or your family members or kids. When a kid gets a rash you give them glucocorticoids so this is the same drug.

So that's in clinical trials now as well?

Dr. Hoffman: That was just awarded and NIHTRND, for therapeutics for rare and neglected diseases. One of the first awards from Francis Collins out of NIH for that program. We expect to have and IND in about nine months for the FDA and in clinical trials soon after that.

Where is the other one at?

Dr. Hoffman: The other one is currently in clinical trials, it's different because it's personalized, you have different drugs for different patients. So the first drug is called exon51, that's been in a series of clinical trials over the last four years already. GSK and Pursenza have started Phase III trials to look for approval. And AVI in the US using a different chemistry and is in Phase II trials. We're developing a second exon, a new drug but the same approach just to a different region of the gene called exon45 we're doing that together with AVI and we're just finishing the negotiations to do the FDAIND.

With the personalized medicine does that have any other implications for other types of diseases?

Dr. Hoffman: The personalized medicine that's being developed for Duchenne because of the promising data in the dogs and the human patients and the mice has already been looked at for other disorders. And it's turning out to be a front line experimental therapeutics for ALS, for Myotonic Dystrophy, for Spinal Muscular Atrophy, some of your more common of rare genetic disorders. Of the genetic disorders in general and you see a lot of excitement in a lot of other disorders.

So you want to target a gene to be used for any type disease?

Dr. Hoffman: Antisense as an approach so making a drug to modulate how a gene makes its mix, its RNA, has been around for twenty years. You think it would for like cancer, you can just put this in and shut down the cancer genes and it really has a lot of trouble. And there's not really hardly any if any drugs approved or in use currently with this antisense technology. We have some key advantages in Duchenne why it's working about one hundred or two hundred times better in Duchenne than it is anything that's been tried elsewhere. Just a couple key principles though, one what we're trying to do is rescue the gene, we're trying to bring it back. Everybody else in cancer and all of those other disorders has tried to turn off a gene. So there's a toxic gene like an oncogene a cancer gene and they want to shut it down. It turns out it's about ten times harder to shut down a gene than it is to bring it back. So really you have to get a little tricky with your indications, with which diseases you want to go after. Because you want a disease where bringing back a gene will fix the condition and there are less of those or they're less obvious than those we want to shut something down like an inflammatory process. So you're starting to restrict some of the indications there. The other second major hurdle that that has faced, most of those other systemic antisense programs is getting enough of this drug. The drug is a little piece of DNA that's coded for the RNA, that's an intermediate step, get it inside enough of the cells at high enough concentrations that does the fixing like you want it to. In Duchenne we're fortunate in that the main problem with the patients is when they're missing dystrophin their muscle starts leaking like crazy which is why you can pick up these kids at birth. You can see the muscle guts in their blood. Those same holes in the muscle we shoot the drug through. So the disease has created a delivery system for the drug for us. Many other disorders don't have that same delivery system. Well not to say it isn't promising but many other disorders have these hurdles that we have been able to clear easily in Duchenne making our indication probably a hundred times better than others to date.

Can you talk about some of the characteristics of Duchenne?

Dr. Hoffman: Duchenne Muscular Dystrophy primarily affects boys because it's on the X chromosome so women can act as carriers and if they pass on dystrophin, abnormal dystrophin gene to their son then the son don't have a second copy and they develop Duchenne Muscular Dystrophy. That said most of the mothers of patients are not carriers the mutation happens spontaneously just from a cosmic ray or eating too much bacon or just spontaneously in that egg. This gene has the highest new mutation rate known of any gene in any organism. It's just knocked out a hundred times or a thousand times more frequently just spontaneously. That's been known since the 1950's because the disease is equally common in human populations throughout the world and also in animals. So that says it has to be knocked out very frequently spontaneously. So in fact many mothers are not carriers it just happened to that single egg going to the child. Once a child, a boy, has Duchenne dystrophy they're often normal at birth, typically, and don't show much problems until three, four, five years of age. And what often happens is in first grade or kindergarten the teacher will notice the boy Johnny just can't keep up with the other kids, can't break into a run, always the last up the stairs. And they say you should probably take him in to a physician and when the physician sees this the disease is common enough that most physicians, many, recognize Duchenne Muscular Dystrophy and they just have to do a blood test. Is there a lot of muscle guts in the blood and that's called serum creatine kinase it was used for heart attacks also for years to see if there's heart guts in your blood, If those levels are through the roof it usually means that's probably Duchenne Muscular Dystrophy. At that point they generally tell the patients well there's no therapy what's going to happen is your son will get progressively weaker and lose muscle throughout their body. They're generally going to be in a wheelchair seven years of age, ten years of age and progressively lose any ability to carry out their activities of daily living. Most patients die in their teens unable to breath. Glucocorticoids using them every day has extended their lifespan a bit so they can stay ambulatory longer and also artificial ventilation. So when a patient reaches their teens many are put on ventilators and that can sustain lifespan a long time, for decades but very little mobility and no ability to carry out activities of daily living. And so it is a devastating diagnosis and to watch your son slowly just lose their muscles from when they are four or five to when they're a teenager able to do less every day.

Have you gotten back any preliminary results from the clinical trial?

Dr. Hoffman: Probably the best data to date is from a Pursenza GSK trial that was done in Sweden and Belgium on some sites that we work with clinically here. And what they showed is at a certain dose if they continued the dosing for two or three years that the patients seemed to be stabilizing. So they presented that at meetings and a recent publication and that's very promising. They were using a relatively low dose and it was only a handful of patients, like five or six but that looks quite promising there. Another recent trial data was just published from Francesco Muntoni in London together with AVI a company in the west coast of the US. And they found when they took biopsies from patients treated with a similar drug they were starting to see quite impressive dystrophin. Not in all patients, again it seemed to be variable but at least in one patient quite impressive dystrophin being produced. And that's the goal is to fix the gene enough where you see that protein coming back in to muscle. So now both studies are entering further stage clinical trials and larger numbers of patients and everybody is very excited about the anticipated data.

What do you think is the most exciting part of the research?

Dr. Hoffman: Well for me there's different perspectives of what you would call the most exciting. Certainly I've been involved in this since the late 1980's. This disease Duchenne was herald as what was known as one of the most important diseases because it is so common and so devastating and to use that disease to identify the first gene and protein through human genomics was very exciting. But to the patients and families to some extent it was false hope. You know here you know what's wrong but so what, how is that helping my son whose muscles are wasting away. So for me it's been twenty five years slugging away hand in hand with the patients, the families, the foundations, the governments and other scientists to say we have to bring this to therapeutics. It's not acceptable as a scientist to say we're done once we find the cause. We have to take that cause and turn it in to a therapy. And so to now to be here today talking to you with these very promising drugs and new trials and again setting the stage for not just for Duchenne but for many disorders is exciting not only for me but also I think a realistic hope for the families and patients.

What questions should the patient be asking you that maybe they don't?

Dr. Hoffman: As we have more and more drugs and trials to test it becomes increasingly important that patients engage themselves in the research and their families. In other words if patients aren't willing to enter clinical trials then we can't help. We can't show that these new approaches are working. So of course when there was nothing to test ten years ago it's not an issue but as now we're turning this corner to more and more trials and more and more promising drugs it becomes that much more important that everybody becomes part of the research team. The physicians, the physical therapists and the patients and the families. So I think what the parents should ask is how do I help the research, how do I join a clinical trial, what's available. And if their physician doesn' t know off hand they need to find out on their own and there's more and more resources to do that.

Anything else you want to add?

Dr. Hoffman: Just that I'm extremely grateful to all the families and patients that have helped me and all our scientists help them. Help understand what's causing this disease and translating to real hope and therapies for their children.

Is this personal for you?

Dr. Hoffman: It's very personal to me at a number of levels, I think it's personal to me where I obtained a Ph.D. in fruit fly genetics. I could turn a fruit fly their eyes, colors, their wing backwards, I could make a custom fruit fly for you. And there's a point at which why are we doing this, where does this head. So I was able to take those tools and help clone the Duchenne gene and use those fruit fly tools to a human problem that affects a lot of families worldwide. So that became personal, I felt like I was helping people and patients using tools that I was lucky enough to have at my hands. I think it's always then as I got more and more involved with the families and the patients and I volunteered at MDA summer camp many years to take care of children with Duchenne as have many people in the lab it became more and more personal. And part of that is also the relationship between the scientists or the physicians and the patients. They can be so constructive and it can be so dangerous too and to see some therapies that were really before their time and the hype versus the hope that became very personal for me. And then to see in personalized medicine as we're this drug development how complicated it is. You know at any point you could say the existing rules don't let us develop personalized medicine and you could just say, oh well I give up. That's not an answer, that can't be an answer so that becomes personal as well. Doing anything I can and the team here can and the institution can to international collaboration to bring this to fruition, to go from knowing what's wrong to helping fix these children.

END OF INTERVIEW

This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.

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A Solution for Duchenne Muscular Dystrophy? -- In Depth Doctor's Interview