Recruiting
Phase 2

Efgartigimod

Sponsor:

argenx

Code:

NCT07583641

Conditions

Autoimmune Encephalitis (AE)

Eligibility Criteria

Sex: All

Age: 12+

Healthy Volunteers: Not accepted

Interventions

Efgartigimod PH20 (ARGX-113) SC

Placebo PH20 SC

Study Details

Brief 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 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

Conditions

Autoimmune Encephalitis (AE)

Study ID

NCT07583641

Start date

Aug 15, 2026

Status verified date

May, 2026

Completion date

May 12, 2029

Anticipated

Primary completion date

Jan 20, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 12+

Healthy Volunteers: Not accepted

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 Design

Enrollment

170 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Part A (Open-Label Lead-in Period): Efgartigimod PH20 SC

All participants will receive efgartigimod PH20 SC open label for 8 weeks

experimental: Part B (Double-blinded treatment period): Efgartigimod PH20 SC

Participants will receive efgartigimod PH20 SC for 24 weeks

placebo comparator: Part B (Maintenance double-blinded treatment period): Placebo PH20 SC

Participants will receive placebo for 24 weeks

experimental: Part C (Open-Label Extension Period): Efgartigimod PH20 SC

Participants who complete Part B will receive efgartigimod PH20 SC for 24 weeks

Interventions

Efgartigimod PH20 (ARGX-113) SC

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 SC

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

Primary outcome measure

  • Change in CASE score in the NMDAR population [ Time Frame: up to week 24 ]

Central Contacts and Locations

Central contacts

Sabine Coppieters, MD

857-350-4834Clinicaltrials@argenx.com

Locations

Center for Neurosciences

Recruiting

Tucson, Arizona, United States, 85718

Contacts

Gwendolyn Grabiec

(520) 529-5234ggrabiec@neurotucson.com

Principal Investigator:

Francisco Valdivia

Texas Institute for Neurological Disorders

Recruiting

Sherman, Texas, United States, 75092-7371

Contacts

Laurie Laurie

(903) 893-5141 x4358ljarvis@texasneurologyinstitute.com

Principal Investigator:

Bharathy Sundaram

More Information

Sponsor

argenx

Last update posted

Aug 24, 2026

Last verified

May, 2026

Keywords

  • Autoimmune Encephalitis (AIE)
  • Adolescents

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by argenx on 2026-08-24.