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[00:00:03] Prof. Paul Gissen: Thank you very much, and good afternoon, ladies and gentlemen. It's a great pleasure for me to talk to you about emerging knowledge on the early indications of MLD in children. And first of all, I need to say thank you to the Excellence in Pediatric Institute for inviting me to give this talk. A few housekeeping announcements, so please don't use screenshots and don't reproduce any of the slides. You will know the format. The questions can be submitted via text and not verbally, and at the end of the talk, I will endeavor to answer most of the questions. So, my name is Paul Gessen, and I work in London. I work at Great Ormond Street Hospital for Children. This is my clinical work and UCL Institute of Child Health, and you'll know the topic of my talk. So, the learning objectives of today is to have a general understanding of the etiology incidence and molecular pathology of metachromatic leukodystrophy, or MLD, to know which laboratory tests to diagnose this condition, to appreciate which patient subgroups need to be tested for a possible diagnosis, and to understand the implications of the diagnosis on clinical management. MLD is a rare autosomal recessive disorder with an estimated birth prevalence in all groups of MLD of about 1 in 40, 000. The disease is caused by mutation in the ARSA gene, which encodes lysosomal enzyme arylsulfatase A, or ARSA. There are phenotypes, the same phenotypes can be mimicked by, first of all, the mutations in PSAP gene, which encodes activator protein saposin B, and also the ASA deficiency can also be caused by mutations in SUMF1 gene, which causes multiple sulfatase deficiency, and a similar phenotype. You see sulfatide accumulation in multiple organs, including central and peripheral nervous system, gallbladder, kidneys, and liver. ARSA is involved in sulfatide metabolism through the hydrolysis of the 3-O-sulfate ester bond of galactosyl and lactosyl sulfatides. The accumulating sulfatides in metachromatic granules in oligodendrocytes, Schwann cells, and also other cells, and that leads to damage to myelin sheaths that result in demyelination and peripheral and central nervous systems. There is a block in differentiation of precursor cells into oligodendrocytes, which prevents remyelination. There is a progressive loss of gross and fine motor functions, decline in cognitive function, which leads to premature death. The diagnosis is made using a combination of enzyme assay and a mutation analysis. In addition, the sulfatide measurements can be done in the urine. You need to keep in mind that enzyme pseudo-deficiency exists because of the polymorphisms in the ARSA gene, and that's why we need to do the mutation analysis to exclude polymorphism causing the pseudo-deficiency and therefore abnormal results. It's important to keep in mind the possibility of PSAP or SOMF1 mutations. They are much, much rarer than the classical MLD, but if you have the phenotype that is typical of MLD, but you can't explain it by mutations in ARSA gene, this could be the possibility. This is just illustrating what the sulfatides look like and the localization of the function of the enzyme. And then when sulfatides accumulate, this is a picture of the peripheral nerve. You see the damage to the nerve, which leads to peripheral neuropathy as well as CNS disease. Moving on to the clinical spectrum of MLD, what you see is that it can have presentation of particularly the neurological symptoms at different ages, which is split in various subgroups. So the earlier forms of the disease are late infantile, where the symptoms arise before the age of 2.5 years or 30 months, and the early juvenile, and this is patients present with symptoms between two and a half years and six years, and then the later onset forms of disease, which is a late juvenile, and the adult onset disease, which is after the age of 16. There are some subdivisions in the juvenile forms as well, but this is as far as we can go. And then, as the disease progresses, some patients get motor phenotype, where you could see loss of milestones, ataxia, muscle weakness, and polyneuropathy. Or you could have a mixed phenotype with motor and cognitive symptoms, and then in the later onset forms, some patients will have a purely cognitive phenotype with behavioural changes, learning difficulties, and psychiatric problems, and these patients with purely cognitive phenotype typically progress slower than the other ones with the motor features. Eventually, though, this leads to severely disabled patients with a loss of motor and cognitive functions. The life expectancy in the earlier forms of the disease, between one and 10 years after diagnosis, and in the later onset forms of disease, can be as long as 35 and longer. MLD is a leukodystrophy, and therefore they have some typical features on the brain MRI scans. It's a deep white matter disease. It typically spares subcortical white matter, and there is no leading edge of enhancement. It's important to point out that the MRI can be normal in the early phase of the disease in the late infantile form. And then in the progressive form of the disease, you get this typical tigroid or leopard skin appearance in advanced disease due to perivascular space distension. And the other sites of involvement, as well as the deep white matter, are corpus callosum, internal capsule, corticospinal tracts, and cerebellar white matter. There are some classifications of disease progression. Typically GMFC, or gross motor function classification, is used. It does take into account both gross motor disease and also expressive language. And it goes from zero, which is basically a completely normal motor function, and then as the disease progresses, it goes as far as six level, where there is loss of any locomotion as well as loss of any head or trunk control. It also takes into account expressive language, and that goes again from zero, where there is a completely normal expressive language, to four, where there's a complete loss of expressive language. This is a picture I used from the MLD Foundation, which explains a bit more on using the GMFC specifically for motor. And for example, if we pick up the GMFC level five on this picture, then these explain as children are transported in a manual wheelchair in all settings, children are limited in their ability to maintain antigravity, head and trunk postures, and control leg and arm movements. How do we manage patients with MLD? Of course, until very recently, mostly the management was symptomatic, and the kind of symptoms that we manage are the seizures with anticonvulsants, feeding when patients lose the ability of safe swallow, so they progress to the use of gastrostomy feeds, and the patients progress to just purely be fed with gastrostomy. Reflux may require medication or surgery. There is abnormal tone with progressive spasticity and movement disorders. There could be scoliosis and respiratory problems as a result of the scoliosis, and then bowel and urinary problems do occur as well and may need to be managed too. Hematopoietic stem cell transplantation has been used in a number of patients. More than 100 patients have been treated like this, and it has been shown that it can be effective, particularly in the later onset forms, especially if patients are treated early on in the disease progress. Ex vivo gene therapy, we talk a bit about that, and the drug called Libmeldy, it's now approved in the EU for pre- symptomatic, late infantile, and early symptomatic, early juvenile forms. There are various drugs that are in development at different stages, but specifically the intrathecal enzyme replacement therapy is being trialed currently. Some early safety publication is already available, but further results of the clinical trial are awaited. I'm going to go on to my own experience and tell you about three patients with MLD and how they progressed. First of all, this is a boy who was in good general health and performing at high level academically until the age of 12 years. From 12, he started struggling with academic performance, started getting clumsier, handwriting became more difficult to understand. He started to struggle playing musical instruments, and he was particularly keen on football, and he struggled with that as well. After a lot of investigations, eventually he had an MRI scan, which showed typical appearance for MLD, then using enzyme assay and mutation analysis, he was diagnosed at the age of 13 and a half. He was assessed, and his physiotherapy assessment was normal, quite detailed analysis of muscle tone and power. His EMG nerve conduction at the time was normal, and he was referred for bone marrow transplant. Pre-transplant, he had the psychological tests, which showed his verbal comprehension, perceptual reasoning, working memory was at the average level, which was low for him because about a year before, he was one of the top in the class at school. His processing speed deteriorated particularly rapidly, and he was already quite a bit below average, so he was quite slow in terms of his processing. He had allogeneic bone marrow transplant at the age of 13 years and eight months, and in the follow-up, particularly early on, he had progressive spasticity and function and quite a low cognitive level, but at the age of 18, he was still able to walk with support and communicate in short sentences. Mostly, he was mobilising in a wheelchair. Unfortunately, two years after the transplant, he developed Ewing's sarcoma of his rib, and then eventually, at the time, the parents decided not to have chemotherapy, but just have the excision of the tumour, which was quite successful, but later on, the tumour recurred and he died of the complications at the age of 20. Moving on to my second case, this was a young lady who had normal perinatal history and normal early development, but at the age of two and a half, she was noted to have frequent falls and she was wobbly on her legs. In the following six months, there was a worsening of motor condition and frustration of not being able to do things. She developed, as they called it, weak eyes or strabismus and she had some difficulties with expressive speech. There was progression of the difficulties with fine motor skills, for example, taking lid off a pen and doing up the zip, and she was vulnerable to falling and injury because she couldn't protect herself. These reflexes weren't quite working. At four, she started school, but was noted to have gross and fine motor problems, balance and coordination problems. She had physiotherapy with some success at the time. At five, she was noted to have tremor and increased sensitivity of sound and more investigations were organized. At about the age of five and a half, her MRI showed poor myelination and suggesting MLD. The tests were done and by the age of six, she was diagnosed with MLD on the basis of enzymology and genetics. At the time, on examinations, she had mild hypotonia, poor reflexes, normal power and slightly abnormal balance. By the age of seven, she was eventually accepted into the gene therapy trial and she received ex vivo gene therapy. She is now 15, eight years post gene therapy and transplant. Currently, her GMFC assessment shows that she is at the motor level of five. She has no locomotion or sitting without support, but some head control is possible. Her communication is actually at the level of one. She can communicate in complete sentences with reduced performance for age. My final case is another lady who was generally healthy and had normal development until the age of five. At five, she became unsteady on her feet. Her behavior became immature. She developed poor attention. She had a brain scan, which showed leukodystrophy consistent with MLD. At the time, the examination showed ataxia, normal power and tone and some coordination problems. She wasn't accepted into the gene therapy trial. She had cognitive issues already at the time and now she's 18. Her GMFC score for expressive language is four, so she has no language at all. The level for the motor score is six, so she has no voluntary movement whatsoever. Her problems are as well as severe spasticity, obstructive sleep apnea, epilepsy, inflammatory bowel disease. She's fed via gastrostomy only. She's completely wheelchair dependent and she has a neuropathic bladder. So this is my own experience, but moving on from that to a larger study. So Tubingen Group just published a study last year where they looked at 97 patients. They enrolled patients with all types of the disease, including late infantile, 35 patients, early juvenile, 18 patients, late juvenile, 38 patients, and a smaller number of adult-onset patients. In summary, what they found was that late infantile and early juvenile patients presenting with motor symptoms underwent similar rapid disease progression. The late juvenile and adult-onset patients underwent also similarly rapid progression of disease if motor symptoms were present, but those that had purely cognitive problems, their disease progress was much slower. This was the split between different groups of patients and what were the early signs. So you could see that in the late infantile form, the majority of patients presented purely with the motor form and a smaller number with motor and cognitive. In the early juvenile, there was a relatively equal split between motor only and motor and cognitive. And then as the older-onset patients, the new group appears, these patients that present only with cognitive disease. What were the early motor signs? So typically patients have gait abnormalities and these were quite early at GMFC level 1 as we discussed earlier. They may also have abnormal movement pattern and for the patients who haven't by then learned to walk independently, it could be loss of gross motor function. For example, loss of crawling, rolling, pulling up, standing, independent sitting or assisted walking. The early cognitive symptoms that were described were the concentration problems, decline in school performance, reduced working speed, disorientation, behavioral problems such as mood disorders, personality changes, psychiatric symptoms and also what is considered as a cognitive problem is where there is a problem with fine motor skills and coordination in complex motor tasks without gait. So these were described as difficulties in conceptual planning of motor activity. So recently it became particularly really important to detect early signs of disease in these patients because a disease- modifying drug became available. So this is the ex vivo gene therapy in MLD. The way it works is that the cells are collected from the patient, particularly from the bone marrow. These cells need to be separated, isolating specifically a type of cells that can then be put back. The cells are then transduced with the lentiviral vector containing the healthy copy of the ARSA gene.
[00:21:11] Prof. Paul Gissen: The patient needs to be conditioned by essentially giving him chemotherapy such as busulfan and then once the space is there for the new cells to settle, the patient is given the cells with the new gene and then these cells need to be engrafted in the bone marrow of the patient. So the Milan group is the group that actually performed this clinical trial led by Alessandro Aiuti and they published the long- term results. This is a paper by Francesca Fumagalli who also gives a session here. So in summary, they had 29 patients with pre- symptomatic or early symptomatic early onset MLD and they were compared with untreated natural history cohort of 31 patients that were matched by age and disease subtype and then the efficacy endpoints were an improvement of more than 10% in GMFC score two years after treatment and also the change from baseline of the total peripheral blood mononuclear cell ARSA activity two years after treatment. So they had 26 patients who were still alive after a median of 3.16 years follow- up. There was a sustained multilineage engraftment of the modified hematopoietic stem and progenitor cells after busulfan conditioning and the ARSA activity was significantly increased above baseline two years after treatment by a mean of 18. 7- fold in patients with late infantile form and 5. 7- fold in the patients with early juvenile form. There were significant differences for the GMFC scores between the treated patients and the controls two years after treatment and this was 66% difference for late infantile and 42% difference for early juvenile. Most treated patients progressively acquired motor skills within the predicted range of healthy children or had stabilized motor performance. Further, most displayed normal cognitive development and prevention or delay of central or peripheral demyelination and brain atrophy. Here the lowest score is used, which is not as commonly used in MLD but more commonly used in ALD. But essentially what we're looking here, on the left graph the darker dots are the treated patients with the late infantile form and you can see that the disease stabilized on the MRI scans compared to the untreated patients. And on the right we're looking at patients with early juvenile form, where the darker blue dots are the ones who were early pre-symptomatic and the lighter blue dots who were early symptomatic and again you see stabilization of the MRI appearance in these patients, in most patients, compared to the controls. This is the graphs that show us the age at severe motor impairment or death and you see on the y- axis the proportion of the patients who are event- free in the late infantile form and in the bottom graph in the early juvenile form and you can see the big, big difference between the untreated patients in the lighter curve compared to the blue curves in the early juvenile and the darker green in the late infantile form. So libmeldi, which is the x- ray with gene therapy, is now licensed and this is their license. It's indicated in children with late infantile or early juvenile forms without clinical manifestation of the disease and also in children with early juvenile form, with early clinical manifestations. And what does early clinical manifestation mean? It means that these patients are still able to walk independently, which means that their GMFC score is one or less and they have cognitive function that hasn't started declining, means that the IQ is over or equals 85.. So, finally, the take- home points are that MLD is a rare, severe, rapidly progressing neurodegenerative disorder. The recently approved in Europe ex vivo gene therapy, libmeldi, changes the course of the disease and the early identification of cases is essential for the patients to be eligible to treatment with libmeldi. Development of other treatments for MLD is now in progress, but we already have something that patients have hoped for. So this is the end of my talk.
[00:26:55] Prof. Paul Gissen: Thank you very much for listening and I'll be very pleased to take any questions from the audience. Thank you very much. Let's see if we have any questions, okay, the first question is, in most cases, which comes first: physical or neurological signs? At what age does late infantile MLD present? Okay, so I'll answer the second question first. And the late infantile MLD is defined as the disease that the symptoms appearing by the age of two and a half or 30 months and what we see in this group of patients that the majority present with motor signs, although some may have motor and cognitive. So, as I showed you earlier, I maybe just jump back to to those slides from the Tübingen group here. that probably will answer your question best. So you could see that in the late infantile you see the majority of patients present with its dark blue which is the motor forms and then the yellow one is a combination of motor and the cognitive. In the early juvenile it's some of them present only with motor but also there is a quite a proportion will be motor and cognitive and the patient of course who already have cognitive deterioration they would not be eligible to libmeldi. And then as you go to the later presenting forms of the disease there is this light blue form which is cognitive only and as I mentioned the group is writing that the cognitive form of the disease is a slower progressing form and of course the drug is not currently licensed for the later forms of the disease. Okay let's see if we have more questions. In the case one I said that there is no signs before the age of 12. Is this common to have such a drop from being top of the class to being diagnosed? Were there no other signs to allow for an early diagnosis? It's a good question and it's of course in hindsight it's easy to criticize the doctors that saw this child earlier on. So he had the late juvenile form of the disease and he presented with both cognitive and motor signs. There really were no signs before the age of 12. That's not uncommon in this form of the disease and then yes when he had the cognitive deterioration I think the school weren't necessarily alerted to the fact that this child needs to be diagnosed. So it took about a year for him to get to a neurologist and then of course when he did see a neurologist then they immediately initiated the investigations and that included the brain MRI scan as well as the kind of a panel of enzyme assays and that was picked up pretty quickly. So when you are looking for it you can find it's not very difficult to diagnose this disease. It's thinking about it that's where I guess that's what this set of seminars is about. Okay next question if we have any. MRI leopard skin appearance image can it be confused with other disorders? So this MRI appearance is quite late. So it may be on just one MRI but I you know there are other leukodystrophies. So I guess the kind of report that would bne typically arriving on you rdesk is that you see there is appearance of leukodystrophy and it could be MLD. The point is what you are going to do about it and which test are you going to order? So these days we are now 2022 so I hope that the test you will order is probably going to be the enzyme assays for a number of neurodegenerative disorders which will include the ARSA enzyme assay and you will probably do genetics at the same time that would be not uncommon that you will request a panel leukodystrophy panel so you wouldn't miss MLD if you do that. I think in some places you know it depends which country the question comes from but but I guess in some places you you know people may still do a one disease targeted test but in many countries now we moved on to panel testing and the important thing is that try to do it as soon as possible so but of course also you would want to be detecting these patients earlier before you have such a severe disease. So I hope I coped with that question all right. Is there any development of a screening test like testing unity sulfatides to diagnose the patient early before developing symptoms? So I think that's probably a loaded question I think. Thank you for this. The yes, why not do an enzyme test as a screening test? The issues, as I already mentioned, is the, the pseudo deficiency, so that would bring up quite a lot of false positives. So, indeed, sulfatides screening test is being developed and looked as the possibility for even a neonatal screening. So this is being discussed and for sure, of course, now there is the treatment and the treat with gene therapy and, considering that we want to be picking up these patients very early, before they develop any signs or symptoms of MLD in the late infantile form, the only way to pick up these patients early enough is doing neonatal screening or if we are detecting the siblings before they develop the the disease. So, yes, the answer to that is yes, there is work on developing the screening tests, including- and that of course, for urinary sulfatides, but also the dry blood spot for sulfatides is also. The work is also in progress. So how soon that's going to be possible I don't know, because of course it may be possible just to do the in some countries. Screening by genomes, that would be another one, but of course there is a lot of pros and cons on doing that. So again, I hope I answered that. So, yes, as I mentioned.
[00:34:50] Prof. Paul Gissen: So the next question is: can newborn screening for MLD help us to identify new MLD cases and candidates for gene therapy? Absolutely so. Newborn screening would be ideal for detecting that and considering how good the results of gene therapy are. That's exactly the way to go. But the test needs to be developed and that needs to be a test that would be accepted by screening committees. I work in the UK and UK screening committee is very strict at which tests appropriate to use a newborn screening. So the test has to satisfy the criteria for that and this, as I said, work is going on. On the sulfatides, enzyme assay may not be the most appropriate one. Genomics may be a possibility. Yes, the work is going on. Thank you for that question too. When is the optimum time to start ex vivo gene therapy? When is it too late to use? So we need to stick to the license and, as I mentioned, in late infantile, so the earliest form of the disease where we have to. You know the patients that already have symptoms by the age of 30 months. So that's really pretty tough to pick up these patients before symptoms, unless there is newborn screening or we are screening siblings of the patients who already presented. So for late infantile form, we have to treat patients without any symptoms whatsoever. For the early juvenile form, and that's the form of the disease when the patient presents between the ages of two and a half and six. So these patients can be either pre-symptomatic and again, the only way to diagnose these patients is if they are siblings or there is some sort of screening. That happens and they may be also early symptomatic. What that means is they have a very early motor symptoms, ie just a bit of a gait abnormality, but they can walk independently and have not started deteriorating at all cognitively. And that really falls on to the, the treating physician, to detect the cognitive. So of course we need to do the full cognitive assessments and if the patient deteriorated by the time they are being they are getting the drug. Then the patient will not be eligible. Thank you very much for all the questions. There's no further questions. I'm going to now end the webinar again. Thanks very much for listening to the audience. Goodbye.