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Tofersen

Phase 3

Amyotrophic Lateral Sclerosis Associated With a SOD1 Gene Mutation | Small molecule | Neurology |Biogen Inc.|Last Updated: Mar 30, 2026

Target and mechanism

Molecular targetSOD1
Target classAntisense Inhibitor
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindNO_TREATMENT_CONTROLLEDDMC
Total Trials1
Total Enrollment158

FDA Designations

PRIORITY_REVIEW

Clinical trial landscape

Tofersen · 5 trials · 5 indications

Phase 3 3Phase 2 1Phase 1 1
NCT04856982A Study of BIIB067 (Tofersen) Initiated in Clinically Presymptomatic Adults With a Confirmed Superoxide Dismutase 1 MutationAmyotrophic Lateral Sclerosis Associated With a SOD1 Gene Mutation
ACTIVE NOT_RECRUITING158 Analytics
NCT03070119Long-Term Evaluation of BIIB067 (Tofersen)ALS Caused by Superoxide Dismutase 1 (SOD1) Mutation
COMPLETED139 Analytics
NCT02623699An Efficacy, Safety, Tolerability, Pharmacokinetics and Pharmacodynamics Study of BIIB067 (Tofersen) in Adults With Inherited Amyotrophic Lateral Sclerosis (ALS)Amyotrophic Lateral Sclerosis
COMPLETED176 Analytics
PHASE3ACTIVE NOT_RECRUITING
A Study of BIIB067 (Tofersen) Initiated in Clinically Presymptomatic Adults With a Confirmed Superoxide Dismutase 1 Mutation
Amyotrophic Lateral Sclerosis Associated With a SOD1 Gene MutationUnlock trial analytics
PHASE3COMPLETED
Long-Term Evaluation of BIIB067 (Tofersen)
ALS Caused by Superoxide Dismutase 1 (SOD1) MutationUnlock trial analytics
PHASE3COMPLETED
An Efficacy, Safety, Tolerability, Pharmacokinetics and Pharmacodynamics Study of BIIB067 (Tofersen) in Adults With Inherited Amyotrophic Lateral Sclerosis (ALS)
Amyotrophic Lateral SclerosisUnlock trial analytics

Study Endpoints

Primary Endpoints

Parts B and C: Percentage of Participants with Emergence of Clinically Manifest ALS Within 24 Months of Part B Baseline
Up to 24 months
Number of Participants With Treatment Emergent Adverse Events (TEAEs) and Treatment Emergent Serious AEs (TESAEs)
From first dose of the study drug in the current study up to end of follow-up period (up to Week 364)

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. An SAE is any untoward medical occurrence that at any dose results in death, life-threatening event, requires inpatient hospitalization, significant disability/incapacity or congenital anomaly. TEAEs were defined as any AEs or SAE with an onset date and time that was on or after the first dose of study drug, or any pre-existing condition that worsened in severity after the first dose of study drug.

Parts A and B: Number of Participants Experiencing Adverse Events (AEs) and Serious Adverse Events (SAEs)
Part A: First dose up to Day 63; Part B: First dose up to Day 289

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. A SAE is any untoward medical occurrence that at any dose results in death, life-threatening event, requires inpatient hospitalization, significant disability/incapacity or congenital anomaly.

Parts A and B: Number of Participants With Clinically Significant Laboratory Abnormalities
Part A: Up to Day 57; Part B: Up to Day 169

Clinical laboratory assessments included hematology, chemistry, and urinalysis.

Parts A and B: Number of Participants With Clinically Significant Vital Sign Abnormalities
Part A: Up to Day 57; Part B: Up to Day 169

The criteria for clinically significant vital sign abnormalities include: Temperature: \>38 degree Celsius (°C) or an increase from baseline of ≥1°C; Pulse: \>120 beats per minute (bpm) or an increase from baseline of \>20 bpm, \<50 bpm or a decrease from baseline of \>20 bpm; Systolic blood pressure (BP): \>180 mmHg or an increase from baseline of \>40 mmHg, \<90 mmHg or a decrease from baseline of \>30 mmHg; Diastolic BP: \>105 mmHg or an increase from baseline of \>30 mmHg, \<50 mmHg or a decrease from baseline of \>20 mmHg.

Parts A and B: Number of Participants With Clinically Significant Physical Examination Abnormalities
Part A: Up to Day 57; Part B: Up to Day 169

Clinically significant physical examination abnormalities included weight decreased.

Parts A and B: Number of Participants With Clinically Significant Neurological Examination Abnormalities
Part A: Up to Day 57; Part B: Up to Day 169

Clinically significant neurological examination abnormalities included hyporeflexia.

Parts A and B: Number of Participants With Clinically Significant 12-lead Electrocardiograms (ECGs) Abnormalities
Part A: Up to Day 57; Part B: Up to Day 169
Parts A and B: PK Parameter of BIIB067 in Plasma: Maximum Observed Concentration (Cmax)
Part A: Pre-dose, 1, 2, 4, 6 hrs post-dose on Day 1; Part B: Pre-dose, 1, 2, 4, 6 hrs post-dose on Day 1 and 1, 2, 4, 6 hrs post-dose on Day 85
Parts A and B: PK Parameter of BIIB067 in Plasma: Time to Reach Maximum Observed Concentration (Tmax)
Part A: Pre-dose, 1, 2, 4, 6 hrs post-dose on Day 1; Part B: Pre-dose, 1, 2, 4, 6 hrs post-dose on Day 1 and 1, 2, 4, 6 hrs post-dose on Day 85
Parts A and B: PK Parameter of BIIB067 in Plasma: Area Under the Concentration-Time Curve From Time Zero to 24 Hours (AUC0-24h)
Parts A and B: Pre-dose, 1, 2, 4, 6 hrs post-dose on Day 1
Parts A and B: PK Parameter of BIIB067 in Plasma: Area Under the Concentration-time Curve From Time Zero to Infinity (AUCinf)
Part A: Pre-dose Day 1, Days 29 and 57; Part B: Pre-dose Days 1, 15, 29, 57 and 85; Day 106 and 169
Parts A and B: PK Parameter of BIIB067 in Plasma: Area Under the Concentration-time Curve From Time Zero to the Time of the Last Measurable Concentration (AUClast)
Part A: Pre-dose Day 1, Days 29 and 57; Part B: Pre-dose Days 1, 15, 29, 57 and 85; Day 106 and 169
Parts A and B: PK Parameter of BIIB067 in Plasma: Apparent Terminal Elimination Half-life (t1/2)
Part A: Pre-dose Day 1, Days 29 and 57; Part B: Pre-dose Days 1, 15, 29, 57 and 85; Day 106 and 169
Parts A and B: PK Parameters of BIIB067 in CSF Levels: Terminal Elimination Half-life (t1/2)
Part A: Pre-dose Day 1, Days 29 and 57; Part B: Pre-dose Days 1, 15, 29, 57 and 85; Day 106 and 169
Part C: Change From Baseline in Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) Total Score at Week 28
Baseline, Week 28 (Day 197)

The ALSFRS-R measures 4 functional domains, including respiratory, bulbar function, gross motor skills, and fine motor skills. There are 12 questions, each scored from 0 (no function) to 4 (full function), for a total possible score of 48. Scores decline with disease progression. ALSFRS-R scores calculated at diagnosis can be compared to scores throughout time to determine the speed of progression. Higher scores represent better function, negative change from baseline indicates disease progression.

Proportion of participants with ≥30% reduction in plasma NfL
From Baseline to Week 28
BIIB067 Concentrations Throughout the CNS
1 to 24 hours post-dose on Day 1

BIIB067 concentrations throughout the CNS will be estimated by single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of 99mTc-MAG3-BIIB067.

Secondary Endpoints

Parts B and C: Time to Emergence of Clinically Manifest ALS
Up to 5.6 years
Parts B and C: Change in ALS Functional Rating Scale (ALSFRS-R) Total Score
Up to 5.6 years
Parts B and C: Change from Baseline in Percent Predicted Slow Vital Capacity (SVC)
Up to 5.6 years
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Part A: Natural History Run-inNO_INTERVENTIONParticipants enrolled in Part A will undergo blood draws approximately once every 28 days to assess neurofilament light chain (NfL) levels.
Part B: Randomized, Double-Blind, Placebo-ControlledEXPERIMENTALParticipants from Part A who meet the protocol-defined NfL threshold and remain presymptomatic may be eligible to participate in Part B. During Part B, participants will receive tofersen 100 milligram (mg) or placebo via intrathecal (IT) injection on Days 1, 15, 29, and every 28 days thereafter for up to approximately 5.6 years.
Part C: Open-Label ExtensionEXPERIMENTALParticipants from Part B who develop clinically manifest ALS may be eligible to participate in Part C. During Part C, participants who received placebo in Part B will receive tofersen 100 mg via IT injection on Days 1, 15, 29, and every 28 days thereafter up to the final maintenance dost visit. Participants who received tofersen during Part B will receive tofersen 100 mg on Days 1, 29, and every 28 days thereafter up to the final maintenance dost visit, with a dose of placebo on Day 15 to maintain the study blind. The combined duration of Part B and Part C is up to approximately 5.6 years.
Part D: Open-Label TreatmentEXPERIMENTALParticipants from Part A who develop clinically manifest ALS prior to randomization in Part B may be eligible to participate in Part D. During Part D, participants will receive tofersen100 mg via IT injection on Days 1, 15, 29, and every 28 days thereafter for up to 2 years.
BIIB067EXPERIMENTALParticipants who have completed Parts A, B, or C of study 233AS101 will be placed in this arm.
Part A-SAD: Combined PlaceboPLACEBO_COMPARATORParticipants will be administered tofersen-matching placebo once by intrathecal bolus injection on Day 1 of Cohorts 1, 2, 3, and 4 respectively.
Part A-SAD: Cohort 1: Tofersen 10 mgEXPERIMENTALParticipants will be administered tofersen 10 mg once by intrathecal bolus injection on Day 1.
Part A-SAD: Cohort 2: Tofersen 20 mgEXPERIMENTALParticipants will be administered tofersen 20 mg once by intrathecal bolus injection on Day 1 of Cohort 2 after the safety review of Cohort 1.
Part A-SAD: Cohort 3: Tofersen 40 mgEXPERIMENTALParticipants will be administered tofersen 40 mg once by intrathecal bolus injection on Day 1 of Cohort 3 after the safety review of Cohort 2.
Part A-SAD: Cohort 4: Tofersen 60 mgEXPERIMENTALParticipants will be administered tofersen 60 mg once by intrathecal bolus injection on Day 1 of Cohort 4 after the safety review of Cohort 3.
Part B-MAD: Combined PlaceboPLACEBO_COMPARATORParticipants will be administered tofersen-matching placebo, 3 loading doses once every 2 weeks on Days 1, 15, 29 and 2 maintenance doses once every 4 weeks on Days 57 and 85 by intrathecal injection.
Part B-MAD: Cohort 5: Tofersen 20 mgEXPERIMENTALParticipants will be administered tofersen 20 mg, 3 loading doses once every 2 weeks on Days 1, 15, 29 and 2 maintenance doses once every 4 weeks on Days 57 and 85 by intrathecal injection.
Part B-MAD: Cohort 6: Tofersen 40 mgEXPERIMENTALParticipants will be administered tofersen 40 mg, 3 loading doses once every 2 weeks on Days 1, 15, 29 and 2 maintenance doses once every 4 weeks on Days 57 and 85 by intrathecal injection after the safety and PK review of Cohort 5.
Part B-MAD: Cohort 7: Tofersen 60 mgEXPERIMENTALParticipants will be administered tofersen 60 mg, 3 loading doses once every 2 weeks on Days 1, 15, 29 and 2 maintenance doses once every 4 weeks on Days 57 and 85 by intrathecal injection after the safety, PK review and SOD1 PD review of Cohort 6.
Part B-MAD: Cohort 8: Tofersen 100 mgEXPERIMENTALParticipants will be administered tofersen 100 mg, 3 loading doses once every 2 weeks on Days 1, 15, 29 and 2 maintenance doses once every 4 weeks on Days 57 and 85 by intrathecal injection after the safety, PK review and SOD1 PD review of Cohort 7.
Part C-Pivotal: PlaceboPLACEBO_COMPARATORParticipants will be administered tofersen-matching placebo, 3 loading doses administered once every 2 weeks on Days 1, 15, 29 followed by 5 maintenance doses administered once every 4 weeks on Days 57, 85, 113, 141, 169 up to 24 weeks by intrathecal bolus injection.
Part C-Pivotal: Tofersen 100 mgEXPERIMENTALParticipants will be administered tofersen 100 mg, 3 loading doses administered once every 2 weeks on Days 1, 15, 29 followed by 5 maintenance doses administered once every 4 weeks on Days 57, 85, 113, 141, 169 up to 24 weeks by intrathecal bolus injection.
TofersenEXPERIMENTAL -
BIIB067 High Dose + 99mTc-MAG3-BIIB067 in 15 mL aCSFEXPERIMENTALParticipants will receive intrathecal injection consisting of unlabeled BIIB067 and 99mTc-MAG3-BIIB067 in 15 milliliter (mL) artificial cerebrospinal fluid (aCSF).
BIIB067 Low Dose + 99mTc-MAG3-BIIB067 in 15 mL aCSFEXPERIMENTALParticipants will receive intrathecal injection consisting of unlabeled BIIB067 and 99mTc-MAG3-BIIB067 in 15 mL aCSF.
BIIB067 Low Dose + 99mTc-MAG3-BIIB067 in 5 mL aCSFEXPERIMENTALParticipants will receive intrathecal injection consisting of unlabeled BIIB067 and 99mTc-MAG3-BIIB067 in 5 mL aCSF.
BIIB067 Low Dose + 99mTc-MAG3-BIIB067 in up to 20 mL aCSFEXPERIMENTALParticipants will receive intrathecal injection consisting of unlabeled BIIB067 and 99mTc-MAG3-BIIB067 in up to 20 mL aCSF.

Interventions

NameTypeDescription
TofersenDRUGAdministered as specified in the treatment arm
PlaceboDRUGAdministered as specified in the treatment arm
99mTc-MAG3-BIIB067DRUGAdministered as specified in the treatment arm.
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites32

Key Part A Inclusion Criteria: * Participants should have a protocol-defined rapidly progressive SOD1 mutation, confirmed by a central reader, or a SOD1 mutation that is approved for inclusion by an external mutation adjudication committee. * Participants with plasma NfL level less than the protoco...

Countries:United StatesAustraliaBelgiumBrazilCanadaFranceGermanyItalyJapanPolandSouth KoreaSpainSwedenUnited KingdomDenmark
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Recent Changes (Last 90 Days)

MEDIUMMay 26, 2026NCT04856982primaryCompletionDate: changed
LOWMay 24, 2026NCT07294144studyFirstPostDate: changed
LOWMay 24, 2026NCT04856982studyFirstPostDate: changed

Frequently asked questions about Tofersen

What is Tofersen used for?

Tofersen is an investigational antisense inhibitor being developed for amyotrophic lateral sclerosis (ALS), including ALS caused by a superoxide dismutase 1 (SOD1) gene mutation. It is also being studied in healthy volunteers and in non-SOD1 ALS. It is not approved and remains in clinical development.

What does Tofersen target?

Tofersen targets SOD1, the superoxide dismutase 1 enzyme. It is an antisense inhibitor designed to reduce production of SOD1 protein, which is relevant in ALS caused by SOD1 mutations. The drug is being studied in patients with SOD1-related ALS.

Who makes Tofersen?

Tofersen is developed by Biogen Inc., traded on the NASDAQ under the ticker BIIB. Biogen is conducting clinical trials of Tofersen in ALS, including studies in patients with SOD1 gene mutations and in non-SOD1 ALS.

What phase is Tofersen in?

Tofersen is in Phase 2 clinical development for non-SOD1 ALS, with a recruiting trial. It has completed Phase 3 trials in SOD1-related ALS and a Phase 1 trial in healthy volunteers. The drug is investigational and not FDA approved.

What clinical trials is Tofersen in?

Tofersen has been studied in several trials. NCT02623699 and NCT03070119 are completed Phase 3 trials in SOD1-related ALS. NCT03764488 is a completed Phase 1 microdose study in healthy volunteers. NCT07294144 is a recruiting Phase 2 trial in non-SOD1 ALS.

Is Tofersen the same as BIIB067?

Yes, Tofersen is also known as BIIB067. Clinical trial titles refer to BIIB067 (Tofersen), and the drug is being studied under this name in trials for ALS and healthy volunteers.