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

Conditions

• Autoimmune Encephalitis (AE)

Eligibility Criteria

Sex

ALL

Age

12 Years - N/A

Healthy Volunteers

Not accepted

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.
• 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

Study Details

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

Key Dates

First listed

May 13, 2026

Start date

Aug 15, 2026

Status verified

May 2026

Primary completion

Jan 20, 2029

Completion

May 12, 2029

Study Design

Enrollment

170 participants (estimated)

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

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

Primary Outcome Measure

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

Central Contacts

• Sabine Coppieters, MD
  857-350-4834
  [email protected]

Locations (2)

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