Adults 18 to 75, any sex, with Epilepsy, Focal Seizures, Partial Seizures. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Change From Baseline in Log-Transformed Seizure Frequency During Weeks 8 to 24 of TreatmentPrimary· Baseline, Week 8 to Week 24
Seizures included were focal aware seizures with motor signs, focal impaired awareness seizures and focal to bilateral tonic-clonic seizure. Focal aware seizures without motor signs were not included. Seizure clusters (where individual seizures cannot be distinguished) were counted as 1 seizure per cluster on each day that they are present. Study baseline seizure frequency (number of seizures per 28 days) was calculated based on participant's seizure diary data during prospective baseline phase. Seizure frequency (SF) at post baseline visit was calculated based on sum of the seizures reported
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
-0.43
± 0.162
Natalizumab 300 mg (Placebo-controlled Phase)
-0.58
± 0.165
Percentage of Responders During Weeks 8 to 24 of TreatmentSecondary· Week 8 to Week 24
Responders were defined as participants with \>=50% reduction from study baseline in seizure frequency during Weeks 8 to 24. Study baseline seizure frequency (number of seizures per 28 days) was calculated based on participants' seizure diary data during the prospective Baseline Phase (number of seizures during Baseline Phase/number of days with non-missing seizure frequency\*28). Participants who withdrew from treatment or required protocol specified modifications of antiepileptic drug (AEDs) prior to Week 24 (completion of the Placebo-controlled Phase) or death related to Epilepsy were consi
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
17.6
Natalizumab 300 mg (Placebo-controlled Phase)
31.3
Number of Participants Free From Seizures During Weeks 8 to 24 of TreatmentSecondary· Week 8 to Week 24
Seizure free is defined as a participant with no seizure reported and no missing diary during Weeks 8 to 24. Participants who withdrew from treatment, required modifications of AEDs prior to Week 24 (completion of the Placebo-controlled Phase), or any missing diary data during Weeks 8 to 24 of treatment were not considered as seizure free in the analysis.
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
1
Natalizumab 300 mg (Placebo-controlled Phase)
0
Percent Change From Baseline of Seizure-Free Days Change During Weeks 8 to 24 of TreatmentSecondary· Baseline, Week 8, Week 12, Week 16, Week 20, Week 24
Study baseline seizure free days (number of seizure free days per 28 days) was calculated based on the diary data during the prospective baseline Phase (Number of seizures during baseline Phase/Number of days with non-missing seizure frequency\*28). Seizure frequency at post baseline visit was calculated based on the sum of the seizures reported in the subject seizure diary and the number of days with non-missing seizure frequency data in the subject seizure diary on or after the previous visit date.
Baseline
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
16.23
± 7.347
Natalizumab 300 mg (Placebo-controlled Phase)
17.54
± 7.223
Week 8
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
4.33
± 50.740
Natalizumab 300 mg (Placebo-controlled Phase)
39.23
± 130.988
Week 12
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
2.41
± 52.613
Natalizumab 300 mg (Placebo-controlled Phase)
32.59
± 104.775
Week 16
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
-0.40
± 43.380
Natalizumab 300 mg (Placebo-controlled Phase)
44.04
± 153.714
Week 20
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
18.48
± 101.318
Natalizumab 300 mg (Placebo-controlled Phase)
40.44
± 144.768
Week 24
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
4.27
± 47.125
Natalizumab 300 mg (Placebo-controlled Phase)
33.92
± 114.436
Percentage of Participants With Inadequate Treatment Response During Weeks 8 to 24 of TreatmentSecondary· Week 8 to Week 24
Inadequate treatment response includes participants who withdraw from treatment due to lack of efficacy or require protocol specified modifications of antiepileptic drugs (AEDs) prior to Week 24 (completion of the placebo- controlled phase) or death related to Epilepsy.
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
6
Natalizumab 300 mg (Placebo-controlled Phase)
3
Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)Secondary· From first dose up to 24 weeks after the last dose of study treatment (up to Week 68)
An AE is any untoward medical occurrence in a 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 assessment such as an abnormal laboratory value), 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, in the view of the Investigator, places the participa
AEs
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
22
Natalizumab 300 mg (Placebo-controlled Phase)
24
Placebo to Natalizumab 300 mg (Open-label Phase)
20
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
17
SAEs
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
1
Natalizumab 300 mg (Placebo-controlled Phase)
1
Placebo to Natalizumab 300 mg (Open-label Phase)
3
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
2
Number of Participants With Clinically Significant Laboratory AbnormalitiesSecondary· From first dose up to 16 weeks after the last dose of study treatment (up to Week 60)
The laboratory assessments included hematology, blood chemistry, serology, urinalysis and vital signs assessment.
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
0
Placebo to Natalizumab 300 mg (Open-label Phase)
0
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
0
Number of Participants With Electronic Columbia-Suicide Severity Rating Scale (eC-SSRS) or C-SSRS ScoreSecondary· Placebo-controlled Phase: Baseline, Weeks 4, 8, 12, 16, 20 and 24; Open-label Phase: Baseline, Weeks 28, 32, 36, 40, 44, 48 and 60/End of Study (EOS)
C-SSRS is a prospective assessment tool to evaluate suicidal ideation and behavior. C-SSRS score for suicidal ideation ranges from 1 to 10, where 1=Wish to be Dead; 2=Nonspecific Active Suicidal Thoughts; 3=Active Suicidal Ideation with Any Methods (Not Plan) without Intent to Act; 4=Active Suicidal Ideation with Some Intent to Act, without Specific Plan; 5=Active Suicidal Ideation with Specific Plan and Intent; and for suicidal behavior ranges from 6=Preparatory Acts or Behavior, 7=Aborted Attempt, 8=Interrupted Attempt, 9=Actual Attempt (nonfatal), 10=Completed Suicide. Participants with a C
Baseline: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
1
Placebo to Natalizumab 300 mg (Open-label Phase)
1
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
1
Week 4: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
0
Week 8: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
0
Week 12: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
1
Week 16: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
0
Natalizumab 300 mg (Placebo-controlled Phase)
3
Week 20: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
1
Natalizumab 300 mg (Placebo-controlled Phase)
2
Week 24: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo (Placebo-controlled Phase)
1
Natalizumab 300 mg (Placebo-controlled Phase)
2
Week 28: Suicidal Ideation or Behavior (1-10)
Group
Value
95% CI
Placebo to Natalizumab 300 mg (Open-label Phase)
3
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
2
Adverse events — posted to ClinicalTrials.gov
Time frame: From first dose up to 24 weeks after the last dose of study treatment (up to Week 68).
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Placebo (Placebo-controlled Phase)
Serious: 1/34 (3%)
Deaths: 0/34
Natalizumab 300 mg (Placebo- Controlled Phase)
Serious: 1/32 (3%)
Deaths: 0/32
Placebo to Natalizumab 300 mg (Open-label Phase)
Serious: 3/31 (10%)
Deaths: 0/31
Natalizumab 300 mg to Natalizumab 300 mg (Open-label Phase)
The primary efficacy objective of the study is to determine if adjunctive therapy of natalizumab 300 mg intravenous (IV) every 4 weeks reduces the frequency of seizures in adult participants with drug-resistant focal epilepsy. The secondary efficacy objective is to assess the effects of natalizumab versus placebo in drug-resistant focal epilepsy on additional measures of seizure frequency.
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
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· Phase 1
· completed
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· active not recruiting
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· terminated
NCT05532163 — A Study to Investigate the Radiological Onset of Action After Treatment Initiation With Subcutaneous (SC) Natalizumab in
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Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Biogen
Last refreshed: 14 December 2021
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03283371.