ClinicalTrials.gov record NCT07583641

A Study to Learn About How Well the Medicine Efgartigimod Works to Treat Autoimmune Encephalitis In Children 12 Years or Older and Adults

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Sep 17, 2026

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

StatusNot yet recruitingThe study has been registered but has not started enrolling. Sites and contacts may not be listed yet.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 2A study that tests whether a treatment has the intended effect and continues to check safety, usually in a larger group than phase 1.
Age12 years old and older
SexAll
LocationUnited States
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This Phase 2 study tests efgartigimod PH20 SC for people aged 12 years and older with Autoimmune Encephalitis. The study has an open-label 8‑week lead-in (Part A), a randomized double‑blind 24‑week drug versus placebo period (Part B), a 24‑week open‑label extension (Part C), and a post‑treatment observation period (Part D). The main statistical cohort is people with anti‑NMDAR antibody–defined disease. Overall participation can last up to about 3 years.

What it is studying. The study is testing whether efgartigimod PH20 SC is effective, safe, and tolerable for treating Autoimmune Encephalitis. It will measure clinical disability and neurocognitive scales (including CASE, mRS, MoCA, RBANS, NPI‑C), seizure outcomes, drug blood levels, total IgG changes, and the development of anti‑drug or anti‑rHuPH20 antibodies, and will compare results in NMDAR versus non‑NMDAR subgroups.

What the researchers hope to learn. To evaluate the efficacy (primary: change in CASE score in the anti‑NMDAR subgroup), safety, and tolerability of efgartigimod PH20 SC; to assess effects on disability, cognition, and neuropsychiatric symptoms; to measure seizure outcomes; and to characterize pharmacokinetics, total IgG changes, and antibody responses (anti‑drug and anti‑rHuPH20), including comparisons between NMDAR and non‑NMDAR groups.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

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

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Biological
  • Efgartigimod PH20 (ARGX-113) SC
Other
  • Placebo PH20 SC

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • 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

Exclusion criteria

  • 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.

Study description and what participation involves

The study's detailed description, as published on ClinicalTrials.gov.

Detailed description from the registry

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.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participation can last up to 3 years and has four parts: Part A (8 weeks open‑label efgartigimod), Part B (24 weeks randomized, double‑blind efgartigimod versus placebo), Part C (24 weeks open‑label efgartigimod for those who complete Part B), and Part D (observation after the last dose; treatment may be restarted if AIE symptoms return). Most doses are given under the skin (subcutaneous) with a prefilled syringe; for participants aged 12 to <18 years who weigh ≤50 kg the drug is given from a vial and syringe. You will attend regular clinic visits for neurological exams and rating scales (for example CASE and mRS), cognitive tests, safety monitoring, and blood samples to measure drug levels, antibodies, and IgG, plus routine tests. During the randomized part you may receive placebo and the study is masked so you and many study staff will not know which treatment you receive.

How the study is structured. A randomized, triple‑masked (blinded), placebo‑controlled Phase 2 trial with multiple parts. Part A: open‑label lead‑in where all participants receive efgartigimod for 8 weeks. Part B: 24‑week randomized double‑blind period comparing efgartigimod with placebo. Part C: 24‑week open‑label extension where those who complete Part B receive efgartigimod. Part D: observation after last dose; efgartigimod can be restarted if symptoms return. Total follow‑up for a participant can be up to about 3 years.

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • Some participants receive a placebo. How is that decided, and what happens for placebo-group participants when the study ends?
  • The registry says recruitment has not started. When is it expected to open, and can I register interest now?
  • The listed sites are in United States. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on autoimmune encephalitis

Clinical trials40 trials listed for autoimmune encephalitisEvery trial the registry lists for autoimmune encephalitis, with recruitment status, phase and sites, updated from ClinicalTrials.gov.See all trials →Research updatesWhat changed in autoimmune encephalitis researchLatest monthly update: September 2026. Includes: Efgartigimod reports. New research summarized each month in plain language, with links to every source paper.Read the latest update →

Important dates

Study start
Apr 1, 2027 (estimated)
Primary completion
July 2030 (estimated)
Study completion
Jul 30, 2030 (estimated)
Target enrollment
170 participants (estimated)
Last updated on registry
Sep 22, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
argenx

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (2)

Terms used on this page · explanations by MedicalUpdates.ai

randomized
Participants are assigned to the study groups by chance, like a coin toss, rather than chosen by the doctor or the participant. This is done so the groups are comparable.
placebo
A treatment that looks like the study treatment but contains no active ingredient. Some participants receive it instead of the study treatment, usually without knowing which they got.
prior treatment
Treatment a person has already had for the condition. A 'line of therapy' is one course of treatment; studies often require, or limit, the number of prior lines.
glucocorticoids
Steroid medicines, such as prednisone, that reduce inflammation. Studies often require a stable dose at entry or measure whether the study treatment allows the dose to be reduced.
before screening
The checks done before enrolment to see whether a person qualifies, such as tests, scans or a review of medical history.
Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
Exclusion Criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.
cohort
A group of people who share a characteristic, such as a diagnosis, and are studied together. 'Prospective' means they are followed forward from enrolment; 'retrospective' means existing records are reviewed.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

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