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

NCT07583641 | Not Yet Recruiting Phase 2 DMC FDA Drug

• 1 other identifier: ARGX-113-22-AIE-2001
• Study Type: interventional
• Target: 170
• Locations: 0 countries
• Sites: N/A

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)

Keywords

Autoimmune Encephalitis (AIE); Adolescents

Outcome Measures

Primary Outcomes (1)

• 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.

  up to week 24

Secondary Outcomes (54)

• Change in mRS

  up to week 8

• Change in CASE score

  up to week 8

• Change in MoCA total score

  up to week 8

• Change in NPI-C total score

  up to week 8

• Change from baseline in CGI-S

  up to week 8

Study Arms (4)

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

EXPERIMENTAL

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

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

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

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

Biological: Efgartigimod PH20 (ARGX-113) SC

Interventions

Efgartigimod PH20 (ARGX-113) SC BIOLOGICAL

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.

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 SC OTHER

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

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

Eligibility Criteria

• Age: 12 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• 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

You may not qualify if:

• 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.

Sponsors & Collaborators

• argenx: lead

MeSH Terms

Conditions

Autoimmune Diseases of the Nervous System

Interventions

efgartigimod alfa

Condition Hierarchy (Ancestors)

Nervous System Diseases; Autoimmune Diseases; Immune System Diseases

Central Study Contacts

Sabine Coppieters, MD

CONTACT

857-350-4834; Clinicaltrials@argenx.com

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: May 7, 2026
• First Posted: May 13, 2026
• Study Start: July 13, 2026
• Primary Completion (Estimated): January 20, 2029
• Study Completion (Estimated): May 12, 2029
• Last Updated: July 20, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share