Autoimmune Encephalitis (AE)Phase 2PolarisNCT07583641
A Study to Learn About How Well the Medicine Efgartigimod Works to Treat Autoimmune Encephalitis In Children 12 Years or Older and Adults
A Phase 2 study testing Efgartigimod PH20 (ARGX-113) SC in people with Autoimmune Encephalitis (AE), run by argenx at 2 sites in United States.
Trial summary
The POLARIS study is designed to evaluate how well efgartigimod PH20 SC may work (called "efficacy") and how safe it is for people diagnosed with Autoimmune Encephalitis (AIE). The study consists of 4 parts: in part A participants will receive efgartigimod SC; in part B, participants will be randomized to receive… Read more about this study
- Who is it for?
- Ages 12 years and older
- Conditions the study is for
- Autoimmune Encephalitis (AE)
- What is being tested?
- Efgartigimod PH20 (ARGX-113) SC
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 170 participants
- Where
- 2 sitesUnited States
- Study dates
- 1 Apr 2027to 30 Jul 2030
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 12 years and older
- All sexes
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- Is at least 12 years of age.
- Meeting at least the criteria for possible AIE according to the Graus criteria.
- Part A:
- Must not have received prior treatment for AIE with PLEX or Ig (participants may have received glucocorticoids); and must not have received PLEX or Ig for any other medical condition in the last 3 months
- Part B: Either completing Part A, or If directly entering Part B, must have received first-line treatment for AIE (i.e. corticosteroids, PLEX, and/or Ig) and have a CASE score of 3 or higher, or a score of 2 or higher in a single sub-item
Who cannot join
- Known anti-myelin oligodendrocyte glycoprotein (anti-MOG) antibody positivity.
- Any medical condition that would interfere with an accurate assessment of clinical symptoms of AIE.
- Recent major surgery (within 3 months of screening) or intention to have major surgery during the study, except for surgeries for AIE-related teratomas and thymomas.
- History (within 12 months before screening) of current alcohol, drug (including recreational or prescribed cannabinoids), or medication abuse.
- Psychiatric or cognitive impairment unrelated to AIE.
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
United States2 sites
Texas Institute for Neurological Disorders
Sherman, Texas, 75092-7371
Laurie Laurie, (903) 893-5141 x4358, ljarvis@texasneurologyinstitute.com
Bharathy Sundaram
Center for Neurosciences
Tucson, Arizona, 85718
Gwendolyn Grabiec, (520) 529-5234, ggrabiec@neurotucson.com
Francisco Valdivia
About this study
Official title: A Global, Multicenter, Randomized, Double-Blinded, Placebo-Controlled, Phase 2 Study to Evaluate the Efficacy, Safety, and Tolerability of Efgartigimod PH20 SC in Adult and Adolescent Participants With Autoimmune Encephalitis
The POLARIS study is designed to evaluate how well efgartigimod PH20 SC may work (called "efficacy") and how safe it is for people diagnosed with Autoimmune Encephalitis (AIE). The study consists of 4 parts: in part A participants will receive efgartigimod SC; in part B, participants will be randomized to receive either efgartigimod SC or placebo; in part C, participants who completed part B will receive efgartigimod SC; in part D, participants who completed part C will be observed after their last dose of efgartigimod SC. If AIE symptoms return, efgartigimod SC treatment may be restarted during this time.
The maximum overall study duration for participants is up to 3 years. More information can be found in clinicaltrials.argenx.com/polaris
Read the detailed description
The study is designed to address the unmet need for effective immunomodulatory therapy in AIE, enrolling patients across multiple antibody-defined subgroups, with the anti-NMDAR encephalitis group serving as the primary cohort for statistical analysis.
- Conditions
- Autoimmune Encephalitis (AE)
- Being tested
- Efgartigimod PH20 (ARGX-113) SC, Placebo PH20 SC
- Keywords
- Autoimmune Encephalitis (AIE), Adolescents
- Medical subject headings
- Autoimmune Diseases of the Nervous System
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Efgartigimod PH20 (ARGX-113) SCBiological
subcutaneous administrations of efgartigimod PH20 SC given by prefilled syringe (PFS). For participants aged 12 to <18 years with body weight ≤50 kg, the study drug will be administered by vial and syringe.
Placebo PH20 SCOther
subcutaneous administrations of placebo PH20 SC given by prefilled syringe (PFS). For participants aged 12 to <18 years with body weight
≤50 kg, the study drug will be administered by vial and syringe
| Study group | Role | What they receive |
|---|---|---|
| Part A (Open-Label Lead-in Period): Efgartigimod PH20 SC | Experimental | All participants will receive efgartigimod PH20 SC open label for 8 weeks Receives: Biological: Efgartigimod PH20 (ARGX-113) SC |
| Part B (Double-blinded treatment period): Efgartigimod PH20 SC | Experimental | Participants will receive efgartigimod PH20 SC for 24 weeks Receives: Biological: Efgartigimod PH20 (ARGX-113) SC |
| Part B (Maintenance double-blinded treatment period): Placebo PH20 SC | Placebo comparator | Participants will receive placebo for 24 weeks Receives: Other: Placebo PH20 SC |
| Part C (Open-Label Extension Period): Efgartigimod PH20 SC | Experimental | Participants who complete Part B will receive efgartigimod PH20 SC for 24 weeks Receives: Biological: Efgartigimod PH20 (ARGX-113) SC |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in CASE score in the NMDAR population
CASE= Clinical Assessment Scale in Autoimmune Encephalitis; NMDAR=N-methyl-D-aspartate receptor; Neuropsychological Status. The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: up to week 24
Secondary outcomes (54)
Change in mRS
The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities. Scores range from 0 (no symptoms) to 6(dead).
Measured: up to week 8
Change in CASE score
The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: up to week 8
Change in MoCA total score
MoCA= Montreal Cognitive Assessment
Measured: up to week 8
Change in NPI-C total score
The NPI-C (Neuropsychiatric Inventory--Clinician) total score will be used as a global measure of neuropsychiatric symptoms.Total score is calculated by summing the scores of all the individual domains.Each domain score is determined by summing the item scores within that domain. The NPI-C uses a clinician rating method, where ratings for frequency, severity, and caregiver distress are provided for each item.These item scores are then summed to create a total domain score.
Measured: up to week 8
Change from baseline in CGI-S
Expression of Change. CGI is a clinician-rated scale that measures illness severity (CGI-S) and global improvement or change (CGI-C).It is rated on a 7-point scale, from 1 (normal) to 7 (amongst the most severely ill patients) for CGI-S and from 1 (very much improved) to 7 (very much worse) for CGI-C.
PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: up to week 8
Change from baseline in PGI-S
A Impression of Severity; PGI-S= Patient Global Impression Scale. PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: up to week 8
Change from baseline in CGI-C
CGI-C= Clinical Global Expression of Change . CGI is a clinician-rated scale that measures illness severity (CGI-S) and global improvement or change (CGI-C).It is rated on a 7-point scale, from 1 (normal) to 7 (amongst the most severely ill patients) for CGI-S and from 1 (very much improved) to 7 (very much worse) for CGI-C.
PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: up to week 8
Change from baseline in PGI-C
A Impression of Severity; PGI-C= Patient Global Expression of Change . PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: up to week 8
Incidence and severity of AEs
AEs= Adverse Effects
Measured: up to week 8
Incidence and severity of SAEs
SAEs = Serious Adverse Effects
Measured: up to week 8
Trough efgartigimod serum concentrations over time
Measured: up to week 8
Percent change from baseline in total IgG levels in serum over time
IgG= Immunoglobulin G
Measured: up to week 8
Incidence and prevalence of ADA against efgartigimod in serum over time
ADA = antidrug antibody(ies)
Measured: up to week 8
Incidence and prevalence of antibodies against rHuPH20 in plasma over time
rHuPH20 = Recombinant Human Hyaluronidase PH20
Measured: up to week 8
Change in mRS in the NMDAR population
The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities. Scores range from 0 (no symptoms) to 6(dead)
Measured: up to week 24
Change in NPI-C total score in the NMDAR population
NPI-C=Neuropsychiatric Inventory-Clinician; NMDAR=N-methyl-D-aspartate receptor. The NPI-C (Neuropsychiatric Inventory--Clinician) total score will be used as a global measure of neuropsychiatric symptoms. Total score is calculated by summing the scores of all the individual domains. Each domain score is determined by summing the item scores within that domain. The NPI-C uses a clinician rating method, where ratings for frequency, severity, and caregiver distress are provided for each item.These item scores are then summed to create a total domain score.
Measured: up to week 24
Change in RBANS in the NMDAR population
RBANS=Repeatable Battery for the Assessment of Neuropsychological Status; NMDAR=N-methyl-D-aspartate receptor. The RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) is a performance outcome measure developed to identify and characterize cognitive impairment by assessing an individual's current level of cognitive performance.
Measured: up to week 24
Percentage of CASE responders in the NMDAR population.
CASE = Clinical Assessment Scale in AIE ; NMDAR=N-methyl-D-aspartate receptor
Measured: at week 24
Change in CASE score in the non-NMDAR population
CASE = Clinical Assessment Scale in AIE; NMDAR=N-methyl. The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure,memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: up to week 24
Change in RBANS in the non-NMDAR population
RBANS= Repeatable Battery for the Assessment of Neuropsychological Status; NMDAR=N-methyl-D-aspartate receptor. The RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) is a performance outcome measure developed to identify and characterize cognitive impairment by assessing an individual's current level of cognitive performance.
Measured: up to week 24
Change in NPI-C total score in the non-NMDAR population
NPI-C= Neuropsychiatric Inventory-Clinician; NMDAR=N-methyl-D-aspartate receptor. The NPI-C Neuropsychiatric Inventory--Clinician) total score will be used as a global measure of neuropsychiatric symptoms. Total score is calculated by summing the scores of all the individual domains. Each domain score is determined by summing the item scores within that domain. The NPI-C uses a clinician rating method, where ratings for frequency, severity, and caregiver distress are provided for each item.
Measured: up to week 24
Change in mRS in the non-NMDAR population
mRS= modified Rankin Scale; NMDAR=N-methyl-D-aspartate receptor. The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities.Scores range from 0 (no symptoms) to 6 (dead).
Measured: up to week 24
Percentage of CASE responders in the non-NMDAR population.
CASE = Clinical Assessment Scale in AIE ; NMDAR=N-methyl-D-aspartate receptor. The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: at week 24
Incidence and severity of AEs
AEs = Adverse Effects
Measured: week 24 onwards
Incidence and severity of SAEs
SAEs = Serious Adverse Effects
Measured: week 24 onwards
Proportion of participants with presence of neuropsychiatric symptoms, defined by NPI-C total score of at least 1 point
NPI-C= Neuropsychiatric Inventory-Clinician. The NPI-C (Neuropsychiatric Inventory--Clinician) total score will be used as a global measure of neuropsychiatric symptoms. Total score is calculated by summing the scores of all the individual domains. Each domain score is determined by summing the item scores within that domain. The NPI-C uses a clinician rating method, where ratings for frequency, severity, and caregiver distress are provided for each item.
Measured: at week 24
Change in MoCA total score
MoCA= Montreal Cognitive Assessment
Measured: up to week 24
Proportion of participants with a favorable outcome in mRS where favorable outcome is defined as no worsening for participants with a baseline mRS score of ≤2 or improvement of ≥1 point for participants with a baseline mRS score of >2
mRS=modified Rankin Scale. The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities. Scores range from 0 (no symptoms) to 6 (dead).
Measured: up to week 24
Change in CGI-S
CGI-S= Clinical Global Impression of Severity. CGI is a clinician-rated scale that measures illness severity (CGI-S) and global improvement or change (CGI-C).It is rated on a 7-point scale, from 1 (normal) to 7 (amongst the most severely ill patients) for CGI-S and from 1 (very much improved) to 7 (very much worse) for CGI-C.
Measured: up to week 24
Change in CGI-C
CGI-C= Clinical Global Impression of Change. CGI is a clinician-rated scale that measures illness severity (CGI-S) and global improvement or change (CGI-C).It is rated on a 7-point scale, from 1 (normal) to 7 (amongst the most severely ill patients) for CGI-S and from 1 (very much improved) to 7 (very much worse) for CGI-C.
Measured: up to week 24
Change in PGI-C
PGI-C =Patient Global Expression of Change. PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: week 0 to week 24
Change in PGI-S
PGI-S= Patient Global Expression of Severity. PGI-S and PGI-C are the patient-reported counterparts to CGI-S and CGI-C, respectively.
Measured: week 0 to week 24
Time to resolution of status epilepticus
Measured: up to 24 weeks
Time to first occurrence of seizure freedom.
Seizure freedom is defined as no seizures for at least 28 consecutive days
Measured: up to 24 weeks
Proportion of participants with seizure freedom for at least the 28 consecutive days
Measured: up to 24 weeks
Time to use of rescue therapy after randomization
Measured: up to 24 weeks
Trough efgartigimod serum concentrations over time
Measured: up to 24 weeks
Percent change in total IgG levels in serum
IgG = Immunoglobulin G
Measured: up to 24 weeks
Incidence and prevalence of ADA against efgartigimod in serum over time
ADA = anti drug antibodies
Measured: up to 24 weeks
Incidence and prevalence of antibodies against rHuPH20 in plasma over time
rHuPH20 = Recombinant Human Hyaluronidase PH20
Measured: up to 24 weeks
Change in CASE score in the NMDAR population compared with the non-NMDAR population
CASE = Clinical Assessment Scale in AIE ; NMDAR=N-methyl-D-aspartate receptor. . The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: up to 24 weeks
Change in RBANS total score
The RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) is a performance outcome measure developed to identify and characterize cognitive impairment by assessing an individual's current level of cognitive performance.
Measured: week 24 to week 48
Percentage of participants with maintained change in the CASE total score (defined as stable or improving)
The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: week 24 to week 48
Percentage of participants with maintained mRS score (defined as stable or improving)
The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities. Scores range from 0 (no symptoms) to 6 (dead).
Measured: week 24 to week 48
Change in NPI-C total score
The NPI-C (Neuropsychiatric Inventory--Clinician) total score will be used as a global measure of neuropsychiatric symptoms.Total score is calculated by summing the scores of all the individual domains. Each domain score is determined by summing the item scores within that domain. The NPI-C uses a clinician rating method, where ratings for frequency, severity, and caregiver distress are provided for each item. These item scores are then summed to create a total domain score.
Measured: week 24 to week 48
Proportion of participants requiring rescue or second-line AIE therapies
AIE = Auto-Immune Encephalitis
Measured: week 24 to week 48
Time to participants requiring rescue or second-line AIE therapies
AIE = Auto-Immune Encephalitis
Measured: week 24 to week 48
Change in CASE
The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
Measured: week 24 to week 48
Change in mRs
The mRS (modified Rankin Scale) is commonly used to measure the degree of disability or dependence in the daily activities of people with neurological disabilities. Scores range from 0 (no symptoms) to 6 (dead).
Measured: week 24 to week 48
Change in RBANS
The RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) is a performance outcome measure developed to identify and characterize cognitive impairment by assessing an individual's current level of cognitive performance.
Measured: week 24 to week 48
Time to resolution of status epilepticus
Measured: week 24 to week 48
Proportion of participants with seizure freedom for at least the 28 consecutive days preceding the participants in final Part of trial
mRS=modified Rankin Scale
Measured: week 24 to week 48
Incidence and prevalence of ADA against efgartigimod in serum
ADA = antidrug antibody(ies)
Measured: week 24 to week 48
Percent change in total IgG levels in serum
IgG = Immunoglobulin G
Measured: week 24 to week 48
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 May 2026
- Study start1 Apr 2027 (estimated)
- Primary completionJul 2030 (estimated)
- Study completion30 Jul 2030 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Autoimmune Encephalitis (AE)Studies of the same condition, open and under way.
- More trials run by argenxThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Investigator
- Enrolment
- 170 participants (estimated)
Sponsor and investigators
- Lead sponsor
- argenx
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07583641
- Sponsor's protocol ID
- ARGX-113-22-AIE-2001
- Acronym
- Polaris
- Status last verified
- May 2026
- First submitted
- 7 May 2026
- Last updated
- 22 Sep 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 22 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Global, Multicenter, Randomized, Double-Blinded, Placebo-Controlled, Phase 2 Study to Evaluate the Efficacy, Safety, and Tolerability of Efgartigimod PH20 SC in Adult and Adolescent Participants With Autoimmune Encephalitis
- ClinicalTrials.gov ID
- NCT07583641
- Acronym / sponsor ID
- Polaris / ARGX-113-22-AIE-2001
- Conditions
- Autoimmune Encephalitis (AE)
- Keywords
- Autoimmune Encephalitis (AIE), Adolescents
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 170 participants (estimated)
- Lead sponsor
- argenxIndustry (pharma, biotech, devices)
- Study start
- 1 Apr 2027 (estimated)
- Primary completion
- Jul 2030 (estimated)
- Study completion
- 30 Jul 2030 (estimated)
- First posted
- 13 May 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The POLARIS study is designed to evaluate how well efgartigimod PH20 SC may work (called "efficacy") and how safe it is for people diagnosed with Autoimmune Encephalitis (AIE). The study consists of 4 parts: in part A participants will receive efgartigimod SC; in part B, participants will be randomized to receive either efgartigimod SC or placebo; in part C, participants who completed part B will receive efgartigimod SC; in part D, participants who completed part C will be observed after their last dose of efgartigimod SC. If AIE symptoms return, efgartigimod SC treatment may be restarted during this time.
The maximum overall study duration for participants is up to 3 years. More information can be found in clinicaltrials.argenx.com/polaris
Detailed description
The study is designed to address the unmet need for effective immunomodulatory therapy in AIE, enrolling patients across multiple antibody-defined subgroups, with the anti-NMDAR encephalitis group serving as the primary cohort for statistical analysis.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, care provider, investigator)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Part A (Open-Label Lead-in Period): Efgartigimod PH20 SC | Experimental | Biological: Efgartigimod PH20 (ARGX-113) SCAll participants will receive efgartigimod PH20 SC open label for 8 weeks |
| Part B (Double-blinded treatment period): Efgartigimod PH20 SC | Experimental | Biological: Efgartigimod PH20 (ARGX-113) SCParticipants will receive efgartigimod PH20 SC for 24 weeks |
| Part B (Maintenance double-blinded treatment period): Placebo PH20 SC | Placebo comparator | Other: Placebo PH20 SCParticipants will receive placebo for 24 weeks |
| Part C (Open-Label Extension Period): Efgartigimod PH20 SC | Experimental | Biological: Efgartigimod PH20 (ARGX-113) SCParticipants who complete Part B will receive efgartigimod PH20 SC for 24 weeks |
Who may qualify
- Ages
- 12 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (5 listed)
- Is at least 12 years of age.
- Meeting at least the criteria for possible AIE according to the Graus criteria.
- Part A:
- Must not have received prior treatment for AIE with PLEX or Ig (participants may have received glucocorticoids); and must not have received PLEX or Ig for any other medical condition in the last 3 months
- Part B: Either completing Part A, or If directly entering Part B, must have received first-line treatment for AIE (i.e. corticosteroids, PLEX, and/or Ig) and have a CASE score of 3 or higher, or a score of 2 or higher in a single sub-item
Key exclusion criteria (5 listed)
- Known anti-myelin oligodendrocyte glycoprotein (anti-MOG) antibody positivity.
- Any medical condition that would interfere with an accurate assessment of clinical symptoms of AIE.
- Recent major surgery (within 3 months of screening) or intention to have major surgery during the study, except for surgeries for AIE-related teratomas and thymomas.
- History (within 12 months before screening) of current alcohol, drug (including recreational or prescribed cannabinoids), or medication abuse.
- Psychiatric or cognitive impairment unrelated to AIE.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Efgartigimod PH20 (ARGX-113) SCsubcutaneous administrations of efgartigimod PH20 SC given by prefilled syringe (PFS). For participants aged 12 to <18 years with body weight ≤50 kg, the study drug will be administered by vial and syringe. | Biological | Part A (Open-Label Lead-in Period): Efgartigimod PH20 SC, Part B (Double-blinded treatment period): Efgartigimod PH20 SC, Part C (Open-Label Extension Period): Efgartigimod PH20 SC |
| Placebo PH20 SCsubcutaneous administrations of placebo PH20 SC given by prefilled syringe (PFS). For participants aged 12 to <18 years with body weight ≤50 kg, the study drug will be administered by vial and syringe | Other | Part B (Maintenance double-blinded treatment period): Placebo PH20 SC |
Primary outcome
Change in CASE score in the NMDAR population
Time frame: up to week 24
CASE= Clinical Assessment Scale in Autoimmune Encephalitis; NMDAR=N-methyl-D-aspartate receptor; Neuropsychological Status. The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.
54 secondary outcomes
Change in mRS
Time frame: up to week 8
Change in CASE score
Time frame: up to week 8
Change in MoCA total score
Time frame: up to week 8
Change in NPI-C total score
Time frame: up to week 8
Change from baseline in CGI-S
Time frame: up to week 8
Change from baseline in PGI-S
Time frame: up to week 8
Change from baseline in CGI-C
Time frame: up to week 8
Change from baseline in PGI-C
Time frame: up to week 8
Incidence and severity of AEs
Time frame: up to week 8
Incidence and severity of SAEs
Time frame: up to week 8
Trough efgartigimod serum concentrations over time
Time frame: up to week 8
Percent change from baseline in total IgG levels in serum over time
Time frame: up to week 8
Incidence and prevalence of ADA against efgartigimod in serum over time
Time frame: up to week 8
Incidence and prevalence of antibodies against rHuPH20 in plasma over time
Time frame: up to week 8
Change in mRS in the NMDAR population
Time frame: up to week 24
Change in NPI-C total score in the NMDAR population
Time frame: up to week 24
Change in RBANS in the NMDAR population
Time frame: up to week 24
Percentage of CASE responders in the NMDAR population.
Time frame: at week 24
Change in CASE score in the non-NMDAR population
Time frame: up to week 24
Change in RBANS in the non-NMDAR population
Time frame: up to week 24
Change in NPI-C total score in the non-NMDAR population
Time frame: up to week 24
Change in mRS in the non-NMDAR population
Time frame: up to week 24
Percentage of CASE responders in the non-NMDAR population.
Time frame: at week 24
Incidence and severity of AEs
Time frame: week 24 onwards
Incidence and severity of SAEs
Time frame: week 24 onwards
Proportion of participants with presence of neuropsychiatric symptoms, defined by NPI-C total score of at least 1 point
Time frame: at week 24
Change in MoCA total score
Time frame: up to week 24
Proportion of participants with a favorable outcome in mRS where favorable outcome is defined as no worsening for participants with a baseline mRS score of ≤2 or improvement of ≥1 point for participants with a baseline mRS score of >2
Time frame: up to week 24
Change in CGI-S
Time frame: up to week 24
Change in CGI-C
Time frame: up to week 24
Change in PGI-C
Time frame: week 0 to week 24
Change in PGI-S
Time frame: week 0 to week 24
Time to resolution of status epilepticus
Time frame: up to 24 weeks
Time to first occurrence of seizure freedom.
Time frame: up to 24 weeks
Proportion of participants with seizure freedom for at least the 28 consecutive days
Time frame: up to 24 weeks
Time to use of rescue therapy after randomization
Time frame: up to 24 weeks
Trough efgartigimod serum concentrations over time
Time frame: up to 24 weeks
Percent change in total IgG levels in serum
Time frame: up to 24 weeks
Incidence and prevalence of ADA against efgartigimod in serum over time
Time frame: up to 24 weeks
Incidence and prevalence of antibodies against rHuPH20 in plasma over time
Time frame: up to 24 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 22 Sep 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Efgartigimod PH20 (ARGX-113) SC in people with Autoimmune Encephalitis (AE), run by argenx at 2 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 22 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Sabine Coppieters, MD (857-350-4834, Clinicaltrials@argenx.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in CASE score in the NMDAR population (time frame: up to week 24). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 22 Sep 2026.