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The first therapy targeted at modifying a mutant gene associated with amyotrophic lateral sclerosis (ALS), approved in early 2023, has offered reassurance that the biology of ALS, when known, is targetable. Historically, the disease has been considered a clinical diagnosis, but the
Despite a narrow indication, the only therapy targeted at an ALS-associated gene so far, SOD1 ALS, supports the premise that the biology of ALS can be modified, according to Christina N. Fournier, MD, an associate professor in the Department of Neurology, Emory University, Atlanta, Georgia.
Rather than a single pathological entity, ALS is best understood as the end result of many different pathological processes. Each might require its own targeted therapy in order to interrupt the upstream biological pathways that drive disease.
About 15% of ALS Has An Identifiable Genetic Cause
A family history of ALS is present in about 10% of cases. A genetic cause can be identified in approximately 15%. Cases without an identifiable genetic etiology are considered sporadic. So far, the only approved therapy that modifies the function of a gene associated with ALS is tofersen (Qalsody, Biogen), an antisense oligonucleotide. Tofersen inhibits RNA transcription of the superoxide dismutase 1 (SOD1) gene to decrease production of the SOD1 protein.
This first gene therapy for ALS is a breakthrough, but it is indicated for only a small proportion of ALS patients. Even though SOD1 gene mutations represent the second most common genetic cause of ALS after the C90rf72 gene, the proportion of patients who are candidates for tofersen is low. Efficacy is expected only in about 1% of those with familial ALS and 1% of those with sporadic ALS, or about 2% of all patients with ALS.
The evidence of benefit from a treatment with a specific target has provided the basis for concluding that “we are onto something,” Dr. Fournier said. An expert in ALS, she sees reason for excitement about the prospects in treatment with the growing focus on the underlying pathways of disease rather than the downstream consequences.
“The hope is that new gene-targeted therapies will be developed in the future to treat the broader ALS population,” said Dr. Fournier, explaining that the move toward rationally targeted treatments, whether related to gene mutations or independent molecular pathways of ALS progression, has created excitement in the field.
Numerous Disease Processes Are Potentially Targetable
As treatments are developed to address nongenetic molecular processes that contribute to the risk or progression of ALS, such as neuroinflammation or abnormal protein misfolding and aggregation, individualized treatment is likely to become key. Just as not all genetic cases share mutations in the same gene, the key molecular drivers of disease are likely to differ between patients. If so, it is hoped that biomarkers reflective of this underlying biology can be identified to appropriately target treatments.
“The excitement behind the newer targets in clinical trials is based on both basic science and early clinical data that support treatment based on specific drivers of disease,” Dr. Fournier said.
In 2023 and just prior to the FDA approval of tofersen, a set of expert consensus guidelines were published calling for genetic testing to be offered to all patients with ALS. These recommendations suggested that SOD1, C9orf72, FUS, and TARDBP should be included routinely into the panel of genes evaluated, calling for additional genes to be added as they emerge as potential therapeutic targets.
Even before these guidelines were released, genetic testing was already being offered at many centers with expertise in ALS. The rationale was to differentiate ALS with a genetic etiology from that with a nongenetic etiology, as well as to counsel family members when genetic risk was identified, but genetic testing has now assumed new urgency. In addition to the potential for offering a specific treatment for SOD1-related ALS, patients with other genetic forms of disease might be candidates for genetically focused clinical trials.
Genetic testing should be performed as soon as a diagnosis of ALS is made, according to Dr. Fournier. Although not all patients have accepted genetic testing, particularly in the past when there was no immediate clinical gain from establishing the presence of a genetic mutation, she said there is no longer any controversy about clinical relevance.
Genetic Testing Is Key to Genetic Therapies
“We do not want to miss the opportunity to treat patients when we have the chance,” said Dr. Fournier, referring to both the likely advantage of an early start of the approved gene therapy as well as the opportunity to participate in a clinical trial with other gene therapies in development.
Prior to the approval of tofersen, riluzole and edaravone had been the only disease-modifying agents in widespread use, but these drugs are nonspecific. There are no established biomarkers for establishing which patients are most likely to benefit.
In the case of riluzole, a pivotal trial conducted 30 years ago showed a survival benefit relative to placebo at 12 months (74% vs. 58%; P = 0.014). In a retrospective study published in 2022 that evaluated survival in a database of 4778 ALS patients of whom 3446 received riluzole, early diagnosis of ALS and prompt treatment with riluzole was associated with longer survival than delayed treatment. The benefit of edaravone has been validated with clinical measures, such as the revised Amyotrophic Lateral Sclerosis Functional Scale (ALSFRS-R).
The retrospective study of riluzole provides the basis for predicting better benefits from disease-modifying therapies if started earlier in the course of ALS. The same premise will be explored with newer therapies that target ALS-associated genes.
Early Treatment Presumed More Effective
“We think that earlier treatment in the course of ALS is probably better for gene therapies as well,” Dr. Fournier said. She cautioned that follow-up is not yet long enough to confirm a survival benefit with tofersen, but she said it is reasonable to anticipate better and longer response when neurologic damage is limited. Citing the effect of gene therapy in spinal muscular atrophy (SMA), where progression is halted if gene therapy is initiated early in life, Dr. Fourier suggested that the emphasis on early treatment stems from the low likelihood for treatments to reverse functional impairments.
“It is conceivable that future treatments might be developed to reverse symptoms, but current drug development is largely aimed at slowing progression,” she explained. Under some circumstances, halting progression has the potential to allow some function to be regained, but as the etiologies of ALS and the pathways of progression are better understood, she believes that all targeted therapy will be started as early as possible to prevent rather than treat neurological damage.
Tofersen, the gene therapy for SOD1-ALS, has provided an opportunity to test the idea that it may be possible to prevent ALS. In a phase 3 trial called ATLAS, unaffected carriers of SOD1 variants that are associated with aggressive disease and high or complete penetrance are enrolled for a run-in phase (Part A) during which participants are followed for a rise in neurofilament light chain (NfL) levels. Based on a previous natural history study called the Pre-Symptomatic Familial ALS (Pre-fALS) study, NfL rises in the serum of unaffected SOD1 carriers prior to phenoconversion. A low NfL is an entry criterion for ATLAS.
ATLAS End Point Is Reduction in Phenoconversion to Clinically Manifest ALS
People in whom NfL rises above a predefined threshold during the run-in stage will be eligible for randomization (Part B) to receive either tofersen or placebo. Efficacy will be measured by comparing the rates of phenoconversion to clinically manifest ALS between those who receive placebo and those who receive tofersen.
Two other groups enrolled in ATLAS will be followed on open-label tofersen. One comprises people who phenoconvert during Part B and the other comprises those who develop ALS during the run-in and therefore are not enrolled in Part B. These patients, forming Parts C and D of the study, provide another set of data to evaluate whether earlier rather than later introduction of therapy provides better outcomes.
“There is a lot of interest and optimism about the trial,” said Dr. Fournier, who praised the trial design and thinks the hypothesis being explored “makes sense.”
Michael Benatar, MD, PhD, professor of neurology and public health, University of Miami School of Medicine, Miami, Florida, is the principal investigator of ATLAS and also leads the Pre-Symptomatic Familial ALS study together with a colleague, Joanne Wuu, Associate Director of Research at the University of Miami ALS Center. The hope from these initiatives, according to Dr. Fournier, is that ATLAS will offer broader learnings beyond just the SOD1 population, providing critical information about the optimal timing of treatment initiation.
The benefit from targeting genes considered causative for ALS is not yet a sure thing. A clinical trial targeting C9orf72, for example, failed to support an approvable therapy. There is a trial of a gene therapy for the FUS variant that is ongoing. Yet, the introduction of a gene therapy for SOD1 variant ALS has already established that highly targeted therapies can be effective, an important step forward after so many failed treatment trials with nonspecific drugs.
“We are seeing more and more therapies being developed to address specific ALS biology,” said Dr. Fournier, who predicts a pivot toward conceptualizing ALS as an array of pathologies rather than one disorder driven by a single mechanism. More effort is being directed to recognizing phenotypes as well as genotypes. Hopefully, more biomarkers that distinguish between ALS variants will emerge and help in individualizing treatment.
“We are not there yet, but I think many of us in the field see this as a way forward,” she said.
Multidisciplinary Care, Symptomatic Management, and Palliative Care Are Still Essential for ALS
Disease-modifying therapies are the ultimate goal in ALS, but Dr. Fournier said that the other side of the equation is multidisciplinary and palliative care. To the extent that almost all ALS therapies only modify the course of disease modestly, palliative care remains the cornerstone of day-to-day care.
“Multidisciplinary and palliative care are not necessarily novel, but they are still critically important. There are clear data to show that multidisciplinary care improves functional status and quality of life, and that this is meaningful to patients,” Dr. Fournier said.
There have been numerous improvements in the areas of multidisciplinary and palliative care, some of which can be credited to advancing technology. In centers of excellence, the multidisciplinary approach has been focused on helping patients sustain a sense of independence and self-worth.
Now robotics, devices, and software are being increasingly employed to extend patient capabilities even in relatively advanced stages of disease, according to Dr. Fournier. As one example, she cited current work in brain-computer interfaces to record electrical activity in the central nervous system to allow patients to communicate even when speech is impaired.
A focus on patient-centered clinical care is appropriate because it is the best current opportunity to improve the lives of patients with ALS. Clinically, this work is very rewarding, according to Dr. Fournier, who described ALS patients overall as generally ”very invested in advocacy and research initiatives and motivated to help others,” Dr. Fournier said.
“The diagnosis can be tough, but there is satisfaction in helping these patients navigate toward an acceptable and meaningful quality of life. They typically give a lot back,” she added.
Overall, there is a sense of progress in ALS, even though it remains a uniformly fatal disease. Dr. Fournier expressed hope that clinical research is reaching a tipping point and an emphasis on targeted treatments after a long list of failed trials over the past 30 years. However, with only one approved therapy modifying an ALS-associated gene, this approach is still in its early stages.
Dr. Fournier has financial relationships with Amylyx, Biogen, Corcept, Denali, Mitsubishi QurAlis, and Tanabe.
Suggested Reading
Benatar M et al. Design of a Randomized, Placebo-Controlled, Phase 3 Trial of Tofersen Initiated in Clinically Presymptomatic SOD1 Variant Carriers: the ATLAS Study. Neurotherapeutics. 2022 Jul;19(4):1248-1258. doi: 10.1007/s13311-022-01237-4.
Geronimo A et al. Ten Years of Riluzole Use in a Tertiary ALS Clinic. Muscle Nerve. 2022 Jun;65(6):659-666. doi: 10.1002/mus.27541.
Roggenbuck J et al. Evidence-Based Consensus Guidelines for ALS Genetic Testing and Counseling. Ann Clin Transl Neurol. 2023 Nov;10(11):2074-2091. doi: 10.1002/acn3.51895.
The first therapy targeted at modifying a mutant gene associated with amyotrophic lateral sclerosis (ALS), approved in early 2023, has offered reassurance that the biology of ALS, when known, is targetable. Historically, the disease has been considered a clinical diagnosis, but the
Despite a narrow indication, the only therapy targeted at an ALS-associated gene so far, SOD1 ALS, supports the premise that the biology of ALS can be modified, according to Christina N. Fournier, MD, an associate professor in the Department of Neurology, Emory University, Atlanta, Georgia.
Rather than a single pathological entity, ALS is best understood as the end result of many different pathological processes. Each might require its own targeted therapy in order to interrupt the upstream biological pathways that drive disease.
About 15% of ALS Has An Identifiable Genetic Cause
A family history of ALS is present in about 10% of cases. A genetic cause can be identified in approximately 15%. Cases without an identifiable genetic etiology are considered sporadic. So far, the only approved therapy that modifies the function of a gene associated with ALS is tofersen (Qalsody, Biogen), an antisense oligonucleotide. Tofersen inhibits RNA transcription of the superoxide dismutase 1 (SOD1) gene to decrease production of the SOD1 protein.
This first gene therapy for ALS is a breakthrough, but it is indicated for only a small proportion of ALS patients. Even though SOD1 gene mutations represent the second most common genetic cause of ALS after the C90rf72 gene, the proportion of patients who are candidates for tofersen is low. Efficacy is expected only in about 1% of those with familial ALS and 1% of those with sporadic ALS, or about 2% of all patients with ALS.
The evidence of benefit from a treatment with a specific target has provided the basis for concluding that “we are onto something,” Dr. Fournier said. An expert in ALS, she sees reason for excitement about the prospects in treatment with the growing focus on the underlying pathways of disease rather than the downstream consequences.
“The hope is that new gene-targeted therapies will be developed in the future to treat the broader ALS population,” said Dr. Fournier, explaining that the move toward rationally targeted treatments, whether related to gene mutations or independent molecular pathways of ALS progression, has created excitement in the field.
Numerous Disease Processes Are Potentially Targetable
As treatments are developed to address nongenetic molecular processes that contribute to the risk or progression of ALS, such as neuroinflammation or abnormal protein misfolding and aggregation, individualized treatment is likely to become key. Just as not all genetic cases share mutations in the same gene, the key molecular drivers of disease are likely to differ between patients. If so, it is hoped that biomarkers reflective of this underlying biology can be identified to appropriately target treatments.
“The excitement behind the newer targets in clinical trials is based on both basic science and early clinical data that support treatment based on specific drivers of disease,” Dr. Fournier said.
In 2023 and just prior to the FDA approval of tofersen, a set of expert consensus guidelines were published calling for genetic testing to be offered to all patients with ALS. These recommendations suggested that SOD1, C9orf72, FUS, and TARDBP should be included routinely into the panel of genes evaluated, calling for additional genes to be added as they emerge as potential therapeutic targets.
Even before these guidelines were released, genetic testing was already being offered at many centers with expertise in ALS. The rationale was to differentiate ALS with a genetic etiology from that with a nongenetic etiology, as well as to counsel family members when genetic risk was identified, but genetic testing has now assumed new urgency. In addition to the potential for offering a specific treatment for SOD1-related ALS, patients with other genetic forms of disease might be candidates for genetically focused clinical trials.
Genetic testing should be performed as soon as a diagnosis of ALS is made, according to Dr. Fournier. Although not all patients have accepted genetic testing, particularly in the past when there was no immediate clinical gain from establishing the presence of a genetic mutation, she said there is no longer any controversy about clinical relevance.
Genetic Testing Is Key to Genetic Therapies
“We do not want to miss the opportunity to treat patients when we have the chance,” said Dr. Fournier, referring to both the likely advantage of an early start of the approved gene therapy as well as the opportunity to participate in a clinical trial with other gene therapies in development.
Prior to the approval of tofersen, riluzole and edaravone had been the only disease-modifying agents in widespread use, but these drugs are nonspecific. There are no established biomarkers for establishing which patients are most likely to benefit.
In the case of riluzole, a pivotal trial conducted 30 years ago showed a survival benefit relative to placebo at 12 months (74% vs. 58%; P = 0.014). In a retrospective study published in 2022 that evaluated survival in a database of 4778 ALS patients of whom 3446 received riluzole, early diagnosis of ALS and prompt treatment with riluzole was associated with longer survival than delayed treatment. The benefit of edaravone has been validated with clinical measures, such as the revised Amyotrophic Lateral Sclerosis Functional Scale (ALSFRS-R).
The retrospective study of riluzole provides the basis for predicting better benefits from disease-modifying therapies if started earlier in the course of ALS. The same premise will be explored with newer therapies that target ALS-associated genes.
Early Treatment Presumed More Effective
“We think that earlier treatment in the course of ALS is probably better for gene therapies as well,” Dr. Fournier said. She cautioned that follow-up is not yet long enough to confirm a survival benefit with tofersen, but she said it is reasonable to anticipate better and longer response when neurologic damage is limited. Citing the effect of gene therapy in spinal muscular atrophy (SMA), where progression is halted if gene therapy is initiated early in life, Dr. Fourier suggested that the emphasis on early treatment stems from the low likelihood for treatments to reverse functional impairments.
“It is conceivable that future treatments might be developed to reverse symptoms, but current drug development is largely aimed at slowing progression,” she explained. Under some circumstances, halting progression has the potential to allow some function to be regained, but as the etiologies of ALS and the pathways of progression are better understood, she believes that all targeted therapy will be started as early as possible to prevent rather than treat neurological damage.
Tofersen, the gene therapy for SOD1-ALS, has provided an opportunity to test the idea that it may be possible to prevent ALS. In a phase 3 trial called ATLAS, unaffected carriers of SOD1 variants that are associated with aggressive disease and high or complete penetrance are enrolled for a run-in phase (Part A) during which participants are followed for a rise in neurofilament light chain (NfL) levels. Based on a previous natural history study called the Pre-Symptomatic Familial ALS (Pre-fALS) study, NfL rises in the serum of unaffected SOD1 carriers prior to phenoconversion. A low NfL is an entry criterion for ATLAS.
ATLAS End Point Is Reduction in Phenoconversion to Clinically Manifest ALS
People in whom NfL rises above a predefined threshold during the run-in stage will be eligible for randomization (Part B) to receive either tofersen or placebo. Efficacy will be measured by comparing the rates of phenoconversion to clinically manifest ALS between those who receive placebo and those who receive tofersen.
Two other groups enrolled in ATLAS will be followed on open-label tofersen. One comprises people who phenoconvert during Part B and the other comprises those who develop ALS during the run-in and therefore are not enrolled in Part B. These patients, forming Parts C and D of the study, provide another set of data to evaluate whether earlier rather than later introduction of therapy provides better outcomes.
“There is a lot of interest and optimism about the trial,” said Dr. Fournier, who praised the trial design and thinks the hypothesis being explored “makes sense.”
Michael Benatar, MD, PhD, professor of neurology and public health, University of Miami School of Medicine, Miami, Florida, is the principal investigator of ATLAS and also leads the Pre-Symptomatic Familial ALS study together with a colleague, Joanne Wuu, Associate Director of Research at the University of Miami ALS Center. The hope from these initiatives, according to Dr. Fournier, is that ATLAS will offer broader learnings beyond just the SOD1 population, providing critical information about the optimal timing of treatment initiation.
The benefit from targeting genes considered causative for ALS is not yet a sure thing. A clinical trial targeting C9orf72, for example, failed to support an approvable therapy. There is a trial of a gene therapy for the FUS variant that is ongoing. Yet, the introduction of a gene therapy for SOD1 variant ALS has already established that highly targeted therapies can be effective, an important step forward after so many failed treatment trials with nonspecific drugs.
“We are seeing more and more therapies being developed to address specific ALS biology,” said Dr. Fournier, who predicts a pivot toward conceptualizing ALS as an array of pathologies rather than one disorder driven by a single mechanism. More effort is being directed to recognizing phenotypes as well as genotypes. Hopefully, more biomarkers that distinguish between ALS variants will emerge and help in individualizing treatment.
“We are not there yet, but I think many of us in the field see this as a way forward,” she said.
Multidisciplinary Care, Symptomatic Management, and Palliative Care Are Still Essential for ALS
Disease-modifying therapies are the ultimate goal in ALS, but Dr. Fournier said that the other side of the equation is multidisciplinary and palliative care. To the extent that almost all ALS therapies only modify the course of disease modestly, palliative care remains the cornerstone of day-to-day care.
“Multidisciplinary and palliative care are not necessarily novel, but they are still critically important. There are clear data to show that multidisciplinary care improves functional status and quality of life, and that this is meaningful to patients,” Dr. Fournier said.
There have been numerous improvements in the areas of multidisciplinary and palliative care, some of which can be credited to advancing technology. In centers of excellence, the multidisciplinary approach has been focused on helping patients sustain a sense of independence and self-worth.
Now robotics, devices, and software are being increasingly employed to extend patient capabilities even in relatively advanced stages of disease, according to Dr. Fournier. As one example, she cited current work in brain-computer interfaces to record electrical activity in the central nervous system to allow patients to communicate even when speech is impaired.
A focus on patient-centered clinical care is appropriate because it is the best current opportunity to improve the lives of patients with ALS. Clinically, this work is very rewarding, according to Dr. Fournier, who described ALS patients overall as generally ”very invested in advocacy and research initiatives and motivated to help others,” Dr. Fournier said.
“The diagnosis can be tough, but there is satisfaction in helping these patients navigate toward an acceptable and meaningful quality of life. They typically give a lot back,” she added.
Overall, there is a sense of progress in ALS, even though it remains a uniformly fatal disease. Dr. Fournier expressed hope that clinical research is reaching a tipping point and an emphasis on targeted treatments after a long list of failed trials over the past 30 years. However, with only one approved therapy modifying an ALS-associated gene, this approach is still in its early stages.
Dr. Fournier has financial relationships with Amylyx, Biogen, Corcept, Denali, Mitsubishi QurAlis, and Tanabe.
Suggested Reading
Benatar M et al. Design of a Randomized, Placebo-Controlled, Phase 3 Trial of Tofersen Initiated in Clinically Presymptomatic SOD1 Variant Carriers: the ATLAS Study. Neurotherapeutics. 2022 Jul;19(4):1248-1258. doi: 10.1007/s13311-022-01237-4.
Geronimo A et al. Ten Years of Riluzole Use in a Tertiary ALS Clinic. Muscle Nerve. 2022 Jun;65(6):659-666. doi: 10.1002/mus.27541.
Roggenbuck J et al. Evidence-Based Consensus Guidelines for ALS Genetic Testing and Counseling. Ann Clin Transl Neurol. 2023 Nov;10(11):2074-2091. doi: 10.1002/acn3.51895.
The first therapy targeted at modifying a mutant gene associated with amyotrophic lateral sclerosis (ALS), approved in early 2023, has offered reassurance that the biology of ALS, when known, is targetable. Historically, the disease has been considered a clinical diagnosis, but the
Despite a narrow indication, the only therapy targeted at an ALS-associated gene so far, SOD1 ALS, supports the premise that the biology of ALS can be modified, according to Christina N. Fournier, MD, an associate professor in the Department of Neurology, Emory University, Atlanta, Georgia.
Rather than a single pathological entity, ALS is best understood as the end result of many different pathological processes. Each might require its own targeted therapy in order to interrupt the upstream biological pathways that drive disease.
About 15% of ALS Has An Identifiable Genetic Cause
A family history of ALS is present in about 10% of cases. A genetic cause can be identified in approximately 15%. Cases without an identifiable genetic etiology are considered sporadic. So far, the only approved therapy that modifies the function of a gene associated with ALS is tofersen (Qalsody, Biogen), an antisense oligonucleotide. Tofersen inhibits RNA transcription of the superoxide dismutase 1 (SOD1) gene to decrease production of the SOD1 protein.
This first gene therapy for ALS is a breakthrough, but it is indicated for only a small proportion of ALS patients. Even though SOD1 gene mutations represent the second most common genetic cause of ALS after the C90rf72 gene, the proportion of patients who are candidates for tofersen is low. Efficacy is expected only in about 1% of those with familial ALS and 1% of those with sporadic ALS, or about 2% of all patients with ALS.
The evidence of benefit from a treatment with a specific target has provided the basis for concluding that “we are onto something,” Dr. Fournier said. An expert in ALS, she sees reason for excitement about the prospects in treatment with the growing focus on the underlying pathways of disease rather than the downstream consequences.
“The hope is that new gene-targeted therapies will be developed in the future to treat the broader ALS population,” said Dr. Fournier, explaining that the move toward rationally targeted treatments, whether related to gene mutations or independent molecular pathways of ALS progression, has created excitement in the field.
Numerous Disease Processes Are Potentially Targetable
As treatments are developed to address nongenetic molecular processes that contribute to the risk or progression of ALS, such as neuroinflammation or abnormal protein misfolding and aggregation, individualized treatment is likely to become key. Just as not all genetic cases share mutations in the same gene, the key molecular drivers of disease are likely to differ between patients. If so, it is hoped that biomarkers reflective of this underlying biology can be identified to appropriately target treatments.
“The excitement behind the newer targets in clinical trials is based on both basic science and early clinical data that support treatment based on specific drivers of disease,” Dr. Fournier said.
In 2023 and just prior to the FDA approval of tofersen, a set of expert consensus guidelines were published calling for genetic testing to be offered to all patients with ALS. These recommendations suggested that SOD1, C9orf72, FUS, and TARDBP should be included routinely into the panel of genes evaluated, calling for additional genes to be added as they emerge as potential therapeutic targets.
Even before these guidelines were released, genetic testing was already being offered at many centers with expertise in ALS. The rationale was to differentiate ALS with a genetic etiology from that with a nongenetic etiology, as well as to counsel family members when genetic risk was identified, but genetic testing has now assumed new urgency. In addition to the potential for offering a specific treatment for SOD1-related ALS, patients with other genetic forms of disease might be candidates for genetically focused clinical trials.
Genetic testing should be performed as soon as a diagnosis of ALS is made, according to Dr. Fournier. Although not all patients have accepted genetic testing, particularly in the past when there was no immediate clinical gain from establishing the presence of a genetic mutation, she said there is no longer any controversy about clinical relevance.
Genetic Testing Is Key to Genetic Therapies
“We do not want to miss the opportunity to treat patients when we have the chance,” said Dr. Fournier, referring to both the likely advantage of an early start of the approved gene therapy as well as the opportunity to participate in a clinical trial with other gene therapies in development.
Prior to the approval of tofersen, riluzole and edaravone had been the only disease-modifying agents in widespread use, but these drugs are nonspecific. There are no established biomarkers for establishing which patients are most likely to benefit.
In the case of riluzole, a pivotal trial conducted 30 years ago showed a survival benefit relative to placebo at 12 months (74% vs. 58%; P = 0.014). In a retrospective study published in 2022 that evaluated survival in a database of 4778 ALS patients of whom 3446 received riluzole, early diagnosis of ALS and prompt treatment with riluzole was associated with longer survival than delayed treatment. The benefit of edaravone has been validated with clinical measures, such as the revised Amyotrophic Lateral Sclerosis Functional Scale (ALSFRS-R).
The retrospective study of riluzole provides the basis for predicting better benefits from disease-modifying therapies if started earlier in the course of ALS. The same premise will be explored with newer therapies that target ALS-associated genes.
Early Treatment Presumed More Effective
“We think that earlier treatment in the course of ALS is probably better for gene therapies as well,” Dr. Fournier said. She cautioned that follow-up is not yet long enough to confirm a survival benefit with tofersen, but she said it is reasonable to anticipate better and longer response when neurologic damage is limited. Citing the effect of gene therapy in spinal muscular atrophy (SMA), where progression is halted if gene therapy is initiated early in life, Dr. Fourier suggested that the emphasis on early treatment stems from the low likelihood for treatments to reverse functional impairments.
“It is conceivable that future treatments might be developed to reverse symptoms, but current drug development is largely aimed at slowing progression,” she explained. Under some circumstances, halting progression has the potential to allow some function to be regained, but as the etiologies of ALS and the pathways of progression are better understood, she believes that all targeted therapy will be started as early as possible to prevent rather than treat neurological damage.
Tofersen, the gene therapy for SOD1-ALS, has provided an opportunity to test the idea that it may be possible to prevent ALS. In a phase 3 trial called ATLAS, unaffected carriers of SOD1 variants that are associated with aggressive disease and high or complete penetrance are enrolled for a run-in phase (Part A) during which participants are followed for a rise in neurofilament light chain (NfL) levels. Based on a previous natural history study called the Pre-Symptomatic Familial ALS (Pre-fALS) study, NfL rises in the serum of unaffected SOD1 carriers prior to phenoconversion. A low NfL is an entry criterion for ATLAS.
ATLAS End Point Is Reduction in Phenoconversion to Clinically Manifest ALS
People in whom NfL rises above a predefined threshold during the run-in stage will be eligible for randomization (Part B) to receive either tofersen or placebo. Efficacy will be measured by comparing the rates of phenoconversion to clinically manifest ALS between those who receive placebo and those who receive tofersen.
Two other groups enrolled in ATLAS will be followed on open-label tofersen. One comprises people who phenoconvert during Part B and the other comprises those who develop ALS during the run-in and therefore are not enrolled in Part B. These patients, forming Parts C and D of the study, provide another set of data to evaluate whether earlier rather than later introduction of therapy provides better outcomes.
“There is a lot of interest and optimism about the trial,” said Dr. Fournier, who praised the trial design and thinks the hypothesis being explored “makes sense.”
Michael Benatar, MD, PhD, professor of neurology and public health, University of Miami School of Medicine, Miami, Florida, is the principal investigator of ATLAS and also leads the Pre-Symptomatic Familial ALS study together with a colleague, Joanne Wuu, Associate Director of Research at the University of Miami ALS Center. The hope from these initiatives, according to Dr. Fournier, is that ATLAS will offer broader learnings beyond just the SOD1 population, providing critical information about the optimal timing of treatment initiation.
The benefit from targeting genes considered causative for ALS is not yet a sure thing. A clinical trial targeting C9orf72, for example, failed to support an approvable therapy. There is a trial of a gene therapy for the FUS variant that is ongoing. Yet, the introduction of a gene therapy for SOD1 variant ALS has already established that highly targeted therapies can be effective, an important step forward after so many failed treatment trials with nonspecific drugs.
“We are seeing more and more therapies being developed to address specific ALS biology,” said Dr. Fournier, who predicts a pivot toward conceptualizing ALS as an array of pathologies rather than one disorder driven by a single mechanism. More effort is being directed to recognizing phenotypes as well as genotypes. Hopefully, more biomarkers that distinguish between ALS variants will emerge and help in individualizing treatment.
“We are not there yet, but I think many of us in the field see this as a way forward,” she said.
Multidisciplinary Care, Symptomatic Management, and Palliative Care Are Still Essential for ALS
Disease-modifying therapies are the ultimate goal in ALS, but Dr. Fournier said that the other side of the equation is multidisciplinary and palliative care. To the extent that almost all ALS therapies only modify the course of disease modestly, palliative care remains the cornerstone of day-to-day care.
“Multidisciplinary and palliative care are not necessarily novel, but they are still critically important. There are clear data to show that multidisciplinary care improves functional status and quality of life, and that this is meaningful to patients,” Dr. Fournier said.
There have been numerous improvements in the areas of multidisciplinary and palliative care, some of which can be credited to advancing technology. In centers of excellence, the multidisciplinary approach has been focused on helping patients sustain a sense of independence and self-worth.
Now robotics, devices, and software are being increasingly employed to extend patient capabilities even in relatively advanced stages of disease, according to Dr. Fournier. As one example, she cited current work in brain-computer interfaces to record electrical activity in the central nervous system to allow patients to communicate even when speech is impaired.
A focus on patient-centered clinical care is appropriate because it is the best current opportunity to improve the lives of patients with ALS. Clinically, this work is very rewarding, according to Dr. Fournier, who described ALS patients overall as generally ”very invested in advocacy and research initiatives and motivated to help others,” Dr. Fournier said.
“The diagnosis can be tough, but there is satisfaction in helping these patients navigate toward an acceptable and meaningful quality of life. They typically give a lot back,” she added.
Overall, there is a sense of progress in ALS, even though it remains a uniformly fatal disease. Dr. Fournier expressed hope that clinical research is reaching a tipping point and an emphasis on targeted treatments after a long list of failed trials over the past 30 years. However, with only one approved therapy modifying an ALS-associated gene, this approach is still in its early stages.
Dr. Fournier has financial relationships with Amylyx, Biogen, Corcept, Denali, Mitsubishi QurAlis, and Tanabe.
Suggested Reading
Benatar M et al. Design of a Randomized, Placebo-Controlled, Phase 3 Trial of Tofersen Initiated in Clinically Presymptomatic SOD1 Variant Carriers: the ATLAS Study. Neurotherapeutics. 2022 Jul;19(4):1248-1258. doi: 10.1007/s13311-022-01237-4.
Geronimo A et al. Ten Years of Riluzole Use in a Tertiary ALS Clinic. Muscle Nerve. 2022 Jun;65(6):659-666. doi: 10.1002/mus.27541.
Roggenbuck J et al. Evidence-Based Consensus Guidelines for ALS Genetic Testing and Counseling. Ann Clin Transl Neurol. 2023 Nov;10(11):2074-2091. doi: 10.1002/acn3.51895.