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[00:00:00] Dr Dipak Ram: Hi and good afternoon everyone. My name is Dipak Ram and I'm a Pediatric Neurologist in Manchester Children's Hospital. And today I'll be talking to you about MLD and the disease trajectory, some clinical characteristics and also therapeutic options. Just a few housekeeping rules, please. So please don't take any screenshots because there are some scans and cases in here. And if you have a question, please pop it into the question box at any point through the presentation and we'll do some Q&A right at the end. So what I'm going to talk to you about is a little bit about the natural history of metachromatic leukodystrophy and then some disease trajectories about the different phenotypes of MLD. And then really, you know, the crux of what we're doing right now in terms of treatment, which is gene therapy and also how we move forward and what the future holds for these patients and families with MLD. So we're going to start off with just a couple of cases.
[00:01:13] Dr Dipak Ram: So this first patient is a boy who was seen just after his second birthday, where his parents felt that he was always a little bit clumsy since he started walking, but felt that more so from his second birthday that he started to become a bit more clumsy. So he was seen by his GP who referred him to a pediatrician. He was seen within eight weeks and the pediatrician examined him and felt that there was some stiffness in his lower limbs, particularly which were noted on examination and arranged to review him in a couple of months. In that first initial visit, a CK was done, which was normal, and a review was organized in eight weeks time and to get physio input. But unfortunately, in a couple of months time, this child had represented becoming very unsteady and had lost some speech and would only walk with support. So become less ambulant quite quickly within a couple of months. And on examination on the ward as an inpatient, the child was very hypotonic centrally with increased tone in the limbs. Had also developed some swallowing difficulties at this point and was choking with liquids and had an urgent scan at that point, which shows this diffuse white matter changes, which you can see here. And this is a very characteristic pattern that you see in leukodystrophies, particularly when it's past what we call the subcortical U fibers. And that's because these are the areas which are really rich in myelin and which are the areas which are first affected when there's a myelination disorder. And this patient was diagnosed with metachromatic leukodystrophy, a classic presentation of late infantile MLD, where they rapidly regress and lose skills. The second case, however, is a little bit different. So this is a girl who's a little bit older. She's seven and concerns were first raised at nursery when she was about four years of age. And she was really diagnosed with dyspraxia. She was thought to have a bit of a tremor, a bit clumsy. And her school felt that, you know, she was maybe a little bit slow, needed some assistance with fine motor tasks. No one really felt that she was regressing or really losing skills at that point. She had seen a pediatrician at that point and had a scan at the age of seven years old. And you can see that scan looks reasonably normal. So there's no significant leukodystrophy or white matter changes. But she was becoming more unsteady. So after three years of roughly being stable, she started to progress and started to develop stiffness with some clonus in her lower limbs. And then the speech problem started and the tremor started affecting her hands more. She couldn't write anymore. And as I mentioned, she had a normal MRI head at this point. And because of the increased tone and it was thought that this could be something peripheral, she had nerve conduction studies done, which showed significant demyelination. So investigations were done from a genetic perspective.
[00:04:20] Dr Dipak Ram: And this came back showing MLD. And this is a presentation which is relatively classic of juvenile MLD, which is much more subtle, much more difficult to diagnose. And they can be relatively stable for quite a few years before they then start losing skills. And in many of these cases, the early MR brain can be normal. So what is MLD? A lot of you will be familiar with MLD, but some of you may not be. So this is an autosomal recessive condition caused by a mutation in the ARSA gene. And it leads to a deficiency in an enzyme. And these enzymes are really needed to break down sulfatides. And when you can't break down sulfatides, they accumulate in the central nervous system and the peripheral nervous system. So these sulfatides build up. As you can see here, it's the brown stars that you can see build up all over the different cells of the body. And unfortunately, that causes progressive toxicity. And the child starts presenting with a neurological decline. The phenotypes are different. So the main two phenotypes to really recognize are the late infantile phenotypes which a lot of people will be scared by when you see a child with this because these are the children who really rapidly decline over months. So you see them in clinic and they are walking and the next time you see them they've lost mobility, lost speech and swallow and a leukodystrophy is thought of very quickly. A scan is done but unfortunately usually this is too late and these children rapidly decline and almost all children die in the first few years of life, universally in the first decade of life. So very scary. Many of you may have seen this or heard about this. Early juvenile MLD, however, much less diagnosed. These are children who have some ARSA activity. So there is an enzyme deficiency but there's still some enzyme present. So the regression is much slower over time and most of the time they present with developmental difficulties rather than regression. And then the cognitive and motor decline starts over time. And as you get into the late juvenile and adulthood presentations, they can sometimes present with cognitive and behavioral problems and almost neuropsychiatric problems. No one will think of MLD really until the motor problems start much later and this could be decades later. So we don't really know much about this because very underdiagnosed and a lot of people don't recognize these phenotypes as well. The top two phenotypes in green we recognize really well and it's important to recognize that as a pediatrician. But you can see that the difficulty with juvenile MLDs, it's a bit different. So late infantile MLD, the top three symptoms you can see is that initial developmental slowing before regression. So they stop acquiring new skills. Mobility is always affected and then they start with either clonus or tremor and you know tone difficulties. Whereas in juvenile, the top three symptoms may be some mobility issues, a change in behavioral personality, and this lack of awareness of surroundings. They may just have some issues which parents say may be struggling with their memory or not recognizing things as well as they could before. So very tricky and you can see why MLD can be misdiagnosed and sometimes been just labeled as someone with dyspraxia, particularly the juvenile MLDs or someone with intellectual disability or mental health problems. So it's really important to recognize that juvenile MLD can present really differently. The progression of MLD is important to also recognize because the late infantile presentations, as I mentioned earlier, really deteriorate rapidly. So many of you may be familiar with GMFC scales, which we use even for cerebral palsy and then modified versions which we use for MLD. But essentially a score of zero means the child is completely fine from a mortal perspective and independently mobile and a score of six means that it's completely bed bound. And you can see with the late infantile phenotypes, these children just rapidly decline by their third birthday. Most of them are completely immobile.
[00:08:41] Dr Dipak Ram: And the juvenile phenotypes are a little bit different because based on whether they're early and late juvenile, they can continue and the decline can occur over years. So much more subtle and much harder to pick up. So how do we make the diagnosis? So most of the time you have to suspect it. You have to suspect that this is something neurodegenerative and that the child is showing some evidence of developmental difficulties. And if there is any decline or loss of skills, then you really need to think about MLD. And in the past, we used to say that, you know, you would have to have a typical scan appearance before you test for MLD. But we are trying to move away from that and saying that if you as a pediatrician are worried about a child regressing, a biochemical test will give you a diagnosis much faster than organizing a scan in a child as an outpatient or an urgent outpatient, which may take weeks or sometimes even months if they need sedation or general anesthetic. These tests are very quick with a turnaround time of 48 to 72 hours if they're sent urgently and can give you a diagnosis very well. Genomic testing are sometimes done and that can help when there is a pseudo-deficiency. So I'm not going to speak too much about this, but that's really from our laboratory point of view. A pseudo-deficiency gene is a common thing which is carried in the population and you may have borderline ARSA levels. But we are very well versed looking at that from a laboratory point of view and we can tell the difference. Usually in late infantile MLD, the ARSA levels are really low, almost undetectable, really single digits. So it is very, very sensitive test. So if you have a child who is regressing and losing skills, please send white cell enzymes and specify that you're concerned about suspected MLD and you will get a result much quicker than organizing a scan. The scan will be confirmatory, but what you need is really a biochemical test to be sent at the point you're thinking of the diagnosis. And it could be, as I mentioned, when you are thinking about someone who is progressing and having a neurodegenerative phenotype. And I mentioned, you know, the other test that we can do is sulfatides in the urine and blood. This is much more complicated and takes longer. As you can imagine, collecting urine from children is always a nightmare. So we really, in the UK, prefer a white cell enzyme to be sent to your local metabolic unit. And the big centers doing this test are London, Birmingham and Manchester. And most of you based in the UK will have a designated center that you send this to. If you are based in Europe, you will have a laboratory assigned to processing white cells enzymes. And some places in Europe do sulfatides very quickly as well. So what are the treatment options that we have got for MLD? So over time, a lot of thought process has been gone into trying to think about how we can improve the quality of life in children with MLD. So initially, trials were being done to think about enzyme replacement.
[00:11:51] Dr Dipak Ram: And if we replace the enzyme, could this be sufficient? And unfortunately, the trials were not that promising and doesn't show that these children have had much benefit in the longer term. And they all continue to deteriorate. So then bone marrow transplantation came along, and this was really what was done before we had gene therapy. For a couple of decades, a lot of people with MLD were getting bone marrow transplant. And what they found was that although it was helping with some of the central nervous system problems, so they didn't develop significant cognitive regression, the peripheral neuropathy and the peripheral disease still continued to progress at the same rate. So unfortunately, these children all still died. And what was happening is that they were developing the significant spasticity and they all became bedbound, but their cognitive skills had not declined as much. And you could argue that that was even more difficult for the child to experience.
[00:12:52] Dr Dipak Ram: So very quickly, that became not an option for late- infantile MLD. It's still thought of for an option for sometimes the late juvenile or adult forms, because you may be able to preserve them for much longer because the phenotype is a bit different. But for the younger patients, certainly that's not an option because the peripheral condition progressed. And then the trials were being done because, as you can imagine, with other neurological conditions looking at gene therapy, it was thought about could we use a gene therapy viral vector and deliver it intracerebrally? But again, those trials ended up not being so promising. And all this time for the younger children, the only option was symptom management. So really managing their tone, using medications, physiotherapy, occupational therapy, speech and language, dietitian input, and palliative care, really, and these children all died. But the main reason for this talk is to say that things have really changed over time. And we are now in the era of gene therapy and using gene therapy to successfully completely modify the lives of these children. So LIBMELDY, which is gene therapy, which is licensed now in the UK and in four other centers in Europe and one center in the US, so six centers currently internationally with a few more centers probably coming up very soon, offering gene therapy, which is stem cell- based. So what is being done is very unique because the stem cells are collected from the patient themselves, then the blood is purified and then sent away to a laboratory where a working copy of the ARSA gene is inserted into the stem cells. And as you can imagine, the stem cells, if they are put back in the child, goes into every cell, which continues to be produced all the time. So these stem cells are put back in, but the gene is switched on much higher.
[00:14:57] Dr Dipak Ram: So to produce the enzyme, the gene is sort of turned on at 100 times the normal rate so that you are producing enzymes at the supra-therapeutic level. Why are we doing that? Because we've realized from bone marrow transplant, when you take someone else's bone marrow and put it into the child, you're delivering normal ARSA enzymes. And we know from experience that these children all develop peripheral neuropathy and they die. So that normal enzyme levels in a child with MLD is not sufficient to penetrate into the CNS and the peripheral nervous system. So the analogy and the theory behind this is why not switch the gene on? We know that high ARSA levels are not toxic, so switching it on 100 times and delivering supra-therapeutic levels of the enzyme in the hope that the child doesn't progress. And the main study which we had was from our collaborators in Milan, where this was being done as an open-label trial and really they were recruiting patients from 2013-14 onwards and published this data last year after having follow-up for quite some time- you know, just about eight years or so- and there were 29 patients who were enrolled in the trial. Most of them were pre-symptomatic, late infertile- and I'll tell you why later on- and some early juvenile children.
[00:16:21] Dr Dipak Ram: Versus the controls, the controls all passed away, as expected, but the patients who were followed up here almost up to eight years- 90% of them- survived. The two patients who didn't- one of them unfortunately had a stroke for a separate reason, nothing to do with MLD, but that had to be documented, so not an MLD related problem. And the second child who passed away was a child who developed symptoms between the time of preparing the gene therapy and infusing it again that the child developed symptoms and started regressing. But because they felt that the child was already consented and was going to go ahead, it was given and unfortunately that child deteriorated even more rapidly than they would otherwise with MLD. So it was then recognized that actually we had to choose the patients very carefully in terms of who gets gene therapy. The gene therapy was otherwise very well tolerated- no major side effects because, as you can imagine this, there's The child's own stem cells are taken out and put back in. They do need to get some chemotherapy, so normally side effects is from chemotherapy, from when you re-infuse your cells to yourself and, of course- no surprise- the pre-symptomatic patients did best. So all the pre-symptomatic patients means that they had an older sibling who died from MLD and they were diagnosed because they had an older sibling already affected who was too late and they were diagnosed basically by either genetic testing or by the enzyme testing when the sibling was tested and they were therefore offered gene therapy and these children really did well.
[00:18:04] Dr Dipak Ram: In fact, one of the children from UK which we sent in back in 2014- now eight years later, is a teenager and plays football completely fine and independently and if you looked at the child you would not be able to tell that the child clinically has MLD because the child's almost effectively modified and does not have the condition. Of course, longer-term follow-up is going to be needed for decades to really make sure that that supratherapeutic enzyme levels stay, but so far, for the follow-up studies, which have now been extended into 2023. They've even got 11 year follow-up which shows that the supratherapeutic enzyme levels are remaining even a decade later, so that the gene therapy is working. Now you can see on this slide that the slides on the left here, top and bottom, show the late infantile MLD children after two years and three years, and the light green here, where my arrow is pointing, are the ones who were untreated. So you can see that they all lost their GMFM scores and were bed-bound, and the scores go down even further because many of them have died, whereas the ones who were treated were all doing really well- and this is the same in early juvenile MLD. The ones who were treated two to three years down the line were staying and maintaining their scores and ambulant levels much better than the ones who were untreated, who went off legs. So this tells us that things are working.
[00:19:27] Dr Dipak Ram: But even when there are things working, you always have to think about what can we do to improve things further. So at the moment, the biggest challenge we have got is that it physically takes about six to eight weeks for the stem cells to be modified and it has to be tested in the laboratory to make sure that the enzyme levels are supratherapeutic. So that process, with quality control, does take about two months. So the worry is of course that in these two months a child who's pre- symptomatic or early symptomatic could develop symptoms and would mean that they would become ineligible for treatment. And we know already from the trial that if you give it to a patient with signs of deterioration already it can accelerate deterioration. So that's still not good enough. So it means that we have to be very strict with our criteria. And here in Manchester we are one of the sites, as I mentioned, one of the five sites in Europe, offering gene therapy for children with MLD. And it's important to know that it has to be a holistic MDT decision because you can imagine this, discussions with families and decision making is very tricky. We have got a European panel as well, so we have got meetings with all centers in Europe so that tricky cases and discussions can happen across the centers, and there's a whole team of us. So to the left on the top is Professor Simon Jones, who's one of our metabolic physicians, and then we have got myself one of the pediatric neurologists here. We've got Rebecca hutton, who's one of our metabolic nurse specialists. At the bottom: Stewart Rust, one of our neuropsychologists, who helps us with the cognitive assessments, Rob Wynne, who is our professor of hematology and transplant, and Kelly, who's one of the stem cell gene therapy nurses, who helps Rob a lot with our patients and families.
[00:21:19] Dr Dipak Ram: So, it's really an MDT decision for each patient that we see, and the criteria for therapy is really to make sure that if they've got late infantile form of MLD, they have to be pre-symptomatic, because as I told you right at the start, these children regress over a couple of months, so unfortunately, there's no way that any child who has got symptomatic late infantile will be eligible for gene therapy, because before you can even start the process, this child will have regressed, unfortunately. So they have to be pre-symptomatic, meaning really, ideally within the first year of their life, because most children start demonstrating features by 18 months to 2 years of age. With early juvenile, as I mentioned, it's much more slowly progressive, so if they are still ambulant and walking and taking 10 or more independent steps, and their IQ score is felt to be reasonable, then we would think about offering gene therapy to them at that stage, but if they are unfortunately no longer ambulant and already starting to lose skills, that means they're going down, because they've stayed stable for a while and they're losing skills, and that means it's a bit too late again, because months make a difference at that point. So the ataxic patients that you have who are struggling to walk independently are patients you need to be thinking about testing for MLD, because you want to pick up early juvenile MLD. So patients who are very ataxic and just struggling and progressively a bit more ataxic but still ambulant, you want to catch them at that point, even with normal imaging to send off the enzyme testing. So our Manchester experience is that we've screened 24 patients so far in the past year since we've been a gene therapy centre, and only 5 of those have been eligible, so that's not good enough, but it is good in the sense that we've managed to offer this treatment to 5 patients. So 4 have already had their treatment, the 5th is in the pipeline. So 2 of them who were late infantile MLDs, one was diagnosed at 1 year of age because of their older sibling having symptoms, the second one had a sibling who already passed away, so was diagnosed really at birth, you know, using antenatal testing and we knew at birth that the child had MLD, and offered a transplant at 5 months of age. The early juvenile ones, one of them had an older sibling who was symptomatic, so was diagnosed at the point where they were still ambulant. The second one had some ataxia and was diagnosed while they were still ambulant, so was offered gene therapy. And this is the slide which is more disheartening to see, is that in the remaining 19 patients we've had to say no, and a lot of them, as you can see, were late infantile diagnosis, so which means they were all rapid loss of skills, which means that there wasn't anything much that a pediatrician could do, because even if you diagnosed them, they would already have symptoms and they'll have regression. So in a lot of these cases, they couldn't have had gene therapy anyway, but in the early juvenile patients, you would hope that we could diagnose them before they lose skills. So you want to diagnose those early juvenile patients who are ataxic and ambulant before they lose their skills. And here again is another slide to show that, you know, this girl, who's the first child in the UK who received stem cell gene therapy, was on the BBC News, many of you may have seen this, then the older sibling, unfortunately, very symptomatic and affected, and this is actually showing that she's already have got significant spasticity, whereas the younger child actually has been treated with gene therapy and will do well, because she's pre-symptomatic. So really, to move things forward from a pre-symptomatic point of view, the only way forward is newborn screening, because as I've told you, that even if you diagnose them early, that we can't offer treatment, but the reason for diagnosing them early is because you do not want to miss the younger sibling, and that has happened before, that we've been referred a child who's three or four, and they've already lost skills, diagnosed quite late, and then they've got a younger sibling who's just turned two, who's then developed symptoms. So we don't want cases like that anymore. So therefore, if you have got a patient you're suspecting with even late infertile MLD, the enzyme test urgently is important, not for that child itself, who may need holistic management and palliative care, which is important, but also because potentially there might be a younger sibling whose life you could save. And we're working a lot with Archangel, which is a charity, to try and really push forward newborn screening, because this really may make a difference in the future.
[00:26:01] Dr Dipak Ram: So what is the summary messages that we are getting out about metachromatic leukodystrophy is that try and recognize this early, and I think it's really, really important to try and capture a diagnosis as early as you can. From a pre-symptomatic point of view, that is not possible, because you can't diagnose someone without symptoms unless they've got an older sibling. So diagnosing an older sibling early is important, so sending enzyme tests, and also in any early juvenile patients, which may be patients who are ataxic, a bit dysplexic, always think about MLD and think about sending off an easy enzyme test alongside your other investigations.
[00:26:42] Dr Dipak Ram: The fastest way to do this is to do an enzyme test, which is available on white cell enzymes and that's available across Europe. It is very rapid and it's really diagnostic. You know, we do gene testing to confirm it, but we've not had a case so far where we've had a clinical scenario of someone, you know, having MLD and a test which is low, which has made us doubt the diagnosis. So it's always fit very nicely. And all patients, I think, should be referred to the MLD service. So there are centers across Europe, so make sure you know your MLD center.
[00:27:19] Dr Dipak Ram: So the main centers that we've got are the centers in Manchester, of course, a center in Milan, a center in Tübingen in Germany, a center in Paris, and a center in Utrecht in Netherlands, which are currently the five commission centers. More centers may appear over time, but all patients should be referred because we want to give families and, you know, patients and families the same streamline advice. And really, this message is important, is that we need to screen all asymptomatic siblings. So if you have ever looked after a patient with MLD who has passed away, please make sure you contact the family if you are the pediatrician or community pediatrician and let them know that things have changed with MLD. There's now treatment so that if they are planning further children, that they need to see a genetic counselor because we want to make that diagnosis earlier and even prevent it from occurring so that the parents understand that things have changed over time. So I think that is another important message to get out there for pediatricians who have previously looked after children with MLD. And remember, the window to intervene is very short, which is why we want an ARSA. If you think someone is losing skills, or if you think that someone is someone you suspect with MLD or has had a previous sibling with MLD, do the ARSA enzyme very quickly rather than trying to get an outpatient scan which you're struggling with. A scan will help, of course, but the enzyme level is much more rapid and will give you a diagnosis very quickly. So try and think about that more quickly. And on that note, I am happy to take any questions from the audience. So the first question is about case one. Is 27 to 29 months rare or common speed of progression? So actually very common speed of progression between two months. So the child was 27 months of age the first time they were seen, and the second time they were seen, they were 29 months of age. So these children actually regress very quickly within weeks or months. So unfortunately, late- infantile MLD, if you've looked after a patient or you see a patient, then you will not forget it because they lose their skills between your appointments. And that is what is scary. And they either end up being admitted or the family call the secretaries to say that, can you see them again? Because they've now gone off legs and you then get very scared, organize a scan and find that significant leukodystrophy. So late- infantile MLD really progresses over weeks to months. Juvenile MLD, which is a bit different, progresses over months to years. So the other question is about the ARSA, which is really good. Is it on a white cell enzyme panels or do we have to specifically say we want it. The only thing I would suggest is to make sure that you specify that you're suspecting MLD because most laboratories will then do it expeditedly because all laboratories in Europe know about gene therapy. So if it's a metabolic laboratory, they will know the importance of testing for ARSA. So if you ask for just a white cell enzymes, that routinely, the turnaround time could be weeks, which is still faster than sometimes organizing a scan as an outpatient, which then you need to do the enzyme testing anyway.
[00:30:59] Dr Dipak Ram: But if you actually request white cell enzymes and you put query MLD, a laboratory will pick that up normally and an astute laboratory technician will run that over 48 to 72 hours. Certainly our lab in Manchester do that. And we know that other labs in UK, they're mentioned about MLD, they will do that. If there's no mention, it may take a few weeks. So I think if you request just a white cell enzyme and put a question mark of MLD, the ARSA will be done automatically.
[00:31:33] Dr Dipak Ram: So, the other question is about supratherapeutic enzyme levels which are sustained indefinitely throughout life. What follow-up treatment or care is needed in the long term? So at the moment, we are planning lifelong follow-up for these patients because we don't know. What we know is that certainly from animal models and from toxicity studies, having a high ARSA enzyme level doesn't do anything. It's toxic. It just means that you've got lots of enzymes floating around and that enzyme is what is needed to break down sulfatides which are toxic. But of course, we need to make sure that from a cognitive point of view, mobility and everything that longer term, there isn't going to be any problems with number one, the enzyme levels dropping and number two, of them causing problems. So, all these children are screened by our MLD center initially every three months, then every six months, then annually. Currently, in Milan, which is the center which originally started doing the trials, they're planning to follow them up for 15 years for the ones who are babies and then send them off to adult care.
[00:32:41] Dr Dipak Ram: So we would transition these children and continue to follow them up through adulthood to make sure that this gene therapy works. Because at the moment, we can't say actually, is this sustained for life? We can say it's sustained for a decade from the trials and from the work we're doing, but we would hope because we are using stem cells, that rationally, it would make sense that this would be sustained for life because it's in all your stem cells and the gene is already switched on. But follow up is going to be long term and it will be by a specialist center. So all children with MLD will be who have gene therapy will be seen by the specialist center very regularly by an MDT. Yeah, so the patient, someone asked the question about patient two and that the MRI scan was normal at seven years of age and sometimes with late juvenile, can there be no signs before this and will it not present on an MR before seven years? So it is very different. So MLD can present very differently in different children. I have seen children with late infantile MLD diagnosed on enzyme testing because they have got developmental impairment and not and a bit ataxic and having an enzyme test showing late infantile MLD and the MRI scan is normal because it predates them completely regressing, but they will regress over weeks to months and they all do. And the same for juvenile. So I think the message out there is that a normal MRI scan does not exclude MLD, but in a lot of patients, even the juvenile ones, they will present an MR scan much earlier than seven years of age. But there are some patients who don't. So we see both phenotypes and it's hard to give you exact statistics because they're so rare. But we've had a handful of patients who are late juvenile and early juvenile who come very ataxic and then start losing skills and then go off legs and then have a scan and the scan is normal. And then someone thinks that this is peripheral neuropathy because they've got stiffness and then they have a nerve conduction study, which is abnormal. And then someone thinks of doing genetic studies and then you get MLD back.
[00:34:54] Dr Dipak Ram: And that is relatively common that it goes through that pathway of not MLD not being talked about. So the main science is really think about it when someone is starting to become progressively ataxic and remember to think about MLD in someone who's developing ataxia of unknown cause, even with a normal MRI. With an abnormal MRI, you definitely test for MLD, but even with a normal MRI, think about the enzyme testing and include it as part of your thing, mainly because it's got treatment. And someone asked a very good question about what is the earliest age to start treatment for pre-symptomatic patients? So that patient, which I told you was diagnosed at birth, we gave the gene therapy at five months of age, roughly at five kilos, because our hematologist felt that that would be a reasonable age to get a good size line in to get enough stem cells out to send off to the laboratory. So you want to make sure you get a decent amount. So you need a relatively good line for the hematologist to get the stem cells out.
[00:35:59] Dr Dipak Ram: So they feel usually about five kilos is when they do it. Of course, things may change with time and we may do it even sooner because there are other things, you know, for children, for example, with SCID and other kinds of things, children get, you know, transplants and things at even younger ages, sometimes in infancy and younger. But we feel that, you know, doing it as soon as you can and safely. So roughly about five kilos is when our transplant center would feel like doing it. So if you diagnose someone antenatally at birth and we know at birth, we'll see the family and probably start the process of getting everything. And then at five months of age, try to get the ball rolling. So on that note, hopefully you found this helpful about thinking about the science of MLD and what to look out for and when to test. And we'll end the webinar on that note. Thank you, everyone, for joining and hopefully see you at one of the next webinars. Thank you.