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Autoimmune EncephalitisPhase 1NCT06575153

Phase 1 Study of ART5803 in Healthy Participants

A Phase 1 study testing ART5803 in people with Autoimmune Encephalitis, run by Arialys Therapeutics at 1 site in Australia.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

The study is a Phase 1, single-center, randomized, double-blind, placebo-controlled, single ascending dose (SAD) and multiple ascending dose (MAD) study to assess the safety, tolerability, pharmacokinetics (PK), and immunogenicity of ART5803 compared with placebo in healthy adult participants Read more about this study

Who is it for?
Ages 18 to 65 yearsHealthy volunteers can take part
Conditions the study is for
Autoimmune Encephalitis
What is being tested?
ART5803
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
64 participants
Where
1 siteAustralia
Study dates
19 Sep 2024to 31 Oct 2025
Phase
Phase 1
Are there results?
None posted in the registry

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 18 to 65 years
  • All sexes
  • Healthy volunteers accepted
  • Adult, Older adult

Who may be able to join

  • The participant is a male or female, 18 to 65 years of age, inclusive, at the time of informed consent and has a body mass index (BMI) of ≥18 to ≤32 kg/m²
  • The participant is healthy, as determined by medical history, physical examinations, and the clinical Investigator's judgment.
  • The participant must be willing and able to provide written, signed informed consent after the nature of the study has been explained, and prior to any research-related procedures.
  • The participant must be willing and able to comply with all study procedures.
  • Sexually active female participants of childbearing potential and male participants with female partner(s) of childbearing potential must be willing to use a highly effective method of contraception while participating in the study.
  • Female participants of childbearing potential must have a negative pregnancy test at Screening and be willing to have additional pregnancy tests during the study. Females considered not of childbearing potential include those who are surgically sterile (surgical bilateral oophorectomy, bilateral salpingectomy, or hysterectomy) confirmed by medical history or are post-menopausal (i.e., no menstrual bleeding for more than 12 months without an alternative medical cause and confirmation with more than 1 follicle-stimulating hormone measurement of at least > 40 IU/L [or higher per local institutional guidelines]).Women of non-childbearing potential are not required to use any contraceptive method.
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  • Male participants with female partners of childbearing potential must agree to use highly effective methods of contraception, from study drug administration until at least 90 days after the last study drug administration.
  • Male participants must agree not to donate sperm and female participants must agree not to donate eggs, for the duration of the study and until at least 90 days after the last study drug administration.
  • Participants must agree to not donate blood for at least 3 months after the end-of-study (EOS) visit

Who cannot join

  • The participant is pregnant or breastfeeding at Screening or planning to become pregnant (self or partner) at any time during the study.
  • The participant has used an investigational product or investigational medical device within 30 days prior to Screening, or is required to use any investigational agent prior to completion of all scheduled study assessments.
  • Has a condition of such severity and acuity, in the opinion of the Investigator, that it warrants immediate surgical intervention or other treatment or may not allow safe participation in the study.
  • The participant has a history of cancer, apart from squamous cell carcinoma of the skin or basal cell carcinoma of the skin. Squamous cell and basal cell carcinomas should be treated with documented success of curative therapy >3 months prior to randomization.
  • The participant has any clinically significant illness, such as cardiovascular, neurologic, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, immunologic, endocrine, or psychiatric disease or disorder, or other abnormality, which may interfere with the evaluation or administration of the study drug, interpretation of participant safety or study results, or would make participation in the study an unacceptable risk including any significant acute or chronic medical condition. It is the responsibility of the Investigator to assess the clinical significance; however, consultation with the medical monitor may be warranted.
  • Has a concurrent disease or condition that, in the view of the Principal Investigator, places the participant at high risk of poor treatment compliance or of not completing the study, or would interfere with study participation or would affect safety. Participants with fully resolved childhood asthma that has had no reoccurrences or hospitalizations remain eligible for participation.
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  • The participant is a regular smoker (cigarettes, e-cigarettes, and vaping included), defined as smoking daily. Participants that are non-daily smokers (up to ≤5 cigarettes per week [or vaping or e-cigarette equivalent]) are permitted to participate in the study and must agree to refrain from smoking from 2 weeks before the first study drug administration until the end of the inpatient stay (Part 1: Day 5; Part 2: Day 29).
  • The participant has a contraindication to undergo LP, including international normalized ratio (INR) >1.4 or other coagulopathy, platelet cell count of <120,000/µL, infection at the desired LP site, current use of anti-coagulant medication except for low dose acetylsalicylic acid, degenerative arthritis, spinal scoliosis, back surgery, suspected increased intracranial pressure on history or neurologic exam, non-communicating hydrocephalus or intracranial mass, or prior history of spinal mass or trauma.
  • The participant has severe drug allergic history or anaphylaxis to 2 or more food products or medicines (including known sensitivity to acetaminophen/paracetamol, diphenhydramine or equivalent antihistamine, methylprednisolone or equivalent glucocorticoid, or lidocaine).
  • The participant has a known history of allergy or reaction to any component of the investigational agent formulation or placebo, or history of anaphylaxis following any biologic therapy.
  • The participant has a history of alcohol abuse or drug addiction in the past 12 months.
  • The participant has undergone significant trauma or major surgery within 4 weeks of Screening.
  • The participant has had a vaccination with live virus, attenuated live virus, or any live viral components within 2 weeks prior to study drug administration or is planning to receive these vaccines at any time during the study and up to 8 weeks following the last study drug administration.
  • The participant has ANY of the following abnormalities in clinical laboratory tests at Screening, as assessed by the study-specific laboratory and confirmed by a single repeat, if deemed necessary:
  • Serum creatinine level more than 1.25× upper limit of normal (ULN) or an estimated glomerular filtration rate value <80 mL/min/1.73 m² calculated with the Chronic Kidney Disease Epidemiology Collaboration formula and more than trace protein in urine.
  • Total bilirubin, aspartate aminotransferase (AST) or alanine aminotransferase (ALT) values more than >2×ULN. Note: participants with a history of Gilbert's syndrome are excluded from participation in the study.
  • Hematological or coagulation values outside the normal reference range for local laboratory results unless regarded as clinically not significant.
  • Confirmed positive test for hepatitis B serology (hepatitis B surface antigen and core antibody) and/or hepatitis C polymerase chain reaction.
  • The participant has a 12-lead ECG demonstrating corrected QT interval by Fridericia (QTcF) >450 ms. If QTcF exceeds 450 ms the ECG should be repeated 2 more times and the average of the 3 QTcF values should be used to determine the participant's eligibility.
  • The participant has Investigator determined coronavirus disease of 2019 (COVID-19) within 4 weeks prior to Day -1, received the COVID-19 vaccine within 2 weeks prior to study drug administration, or plans to receive a COVID-19 vaccine within 9 weeks after study drug administration. Regional and site COVID-19 testing policies should be followed throughout the study.
  • The participant has a positive urine or blood result for drugs of abuse (defined as any illicit drug use) at Screening or check-in (Day -1).
  • The participant has received any NMDAR modulator other than the study drug (e.g., ketamine, memantine, dextromethorphan, amantadine, ifenprodil, phencyclidine [PCP], acamprosate, D-cycloserine) or IVIG from within 30 days or 5 half-lives of the other NMDAR modulator or IVIG (whichever is longer) of study drug administration until the end of the study.
  • The participant has a known history of a primary immunodeficiency (congenital or acquired) or an underlying condition such as human immunodeficiency virus infection
  • The participant has had a bacillus of Calmette and Guérin vaccine within 1 year of enrollment.
  • The participant has a history of severe depression, bipolar disease, or schizophrenia.
  • The participant has a risk of suicide per the C-SSRS (a score of 4 or 5 on ideation or any suicidal behavior) or according to the Investigator's clinical judgment, has made a suicide attempt in the previous 6 months, or has a history of deliberate self-harm in the past 6 months

Trial locations and contacts

1 site in 1 country.

Australia1 site

  • Nucleus Network Pty Ltd

    Melbourne, Victoria, 3004

Other trials in Australia

About this study

Official title: A Phase 1, Randomized, Double-blind, Single Ascending Dose and Multiple Ascending Dose Study to Assess the Safety, Tolerability, and Pharmacokinetics of ART5803 Compared With Placebo in Healthy Participants

The study is a Phase 1, single-center, randomized, double-blind, placebo-controlled, single ascending dose (SAD) and multiple ascending dose (MAD) study to assess the safety, tolerability, pharmacokinetics (PK), and immunogenicity of ART5803 compared with placebo in healthy adult participants

Read the detailed description

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is one of the most common causes of autoimmune encephalitis. The disease is caused by the development of autoantibodies against the amino (N)-terminal domain (NTD) of the NMDAR subunit 1 (NR1) that bind and cross link the receptors, leading to receptor internalization and loss of function. Arialys has developed a monovalent (one-armed) antibody, ART5803, that binds to the NTD of the NMDAR NR1 subunit without causing NMDAR inhibition, activation, or receptor internalization, while simultaneously blocking the ability of the pathogenic anti-NMDAR autoantibodies to bind to the receptor. This first-in-human (FIH) study will assess the safety, tolerability, pharmacokinetics (PK), and immunogenicity of ART5803 compared with placebo in healthy participants.

Being tested
ART5803
Keywords
Anti-N-methyl-D-aspartate receptor (NMDAR), Encephalitis, Anti-N-methyl-D-aspartate receptor (NMDAR) Encephalitis
Medical subject headings
Autoimmune Diseases of the Nervous System, Encephalitis

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • ART5803Drug

    A monovalent (one-armed) antibody, that binds to the NTD of the NMDAR NR1 subunit without causing NMDAR inhibition, activation, or receptor internalization, while simultaneously blocking the ability of the pathogenic anti-NMDAR autoantibodies to bind to the receptor.

Study groups in NCT06575153
Study groupRoleWhat they receive
Part 1 (SAD) Cohort 1 - Dose Level 1Experimental3 mg/kg of ART5803 IV infusion over approximately 90 minutes (±60 minutes)
Receives: Drug: ART5803
Part 1 (SAD) Cohort 2- Dose Level 2Experimental10 mg/kg of ART5803 IV infusion over approximately 90 minutes (±60 minutes)
Receives: Drug: ART5803
Cohort 3 (SAD)/Cohort A (MAD) - Dose Level 3Experimental30 mg/kg of ART5803 IV infusion over approximately 90 minutes (±60 minutes)
Receives: Drug: ART5803
Cohort 4 (SAD)/Cohort B (MAD) - Dose Level 4Experimental60 mg/kg of ART5803 IV infusion over approximately 90 minutes (±60 minutes)v
Receives: Drug: ART5803
Cohort 5 (SAD)/Cohort C (MAD) - Dose Level 5Experimental100 mg/kg of ART5803 IV infusion over approximately 90 minutes (±60 minutes)
Receives: Drug: ART5803
PlaceboNo intervention0.9% normal saline IV infusion over approximately 90 minutes (±60 minutes)

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Safety will be assessed by the incidence and severity of treatment-emergent adverse events (TEAEs)

    ART5803 safety, as measured by the number of treatment emergent adverse events compared with placebo.

    Measured: 12 weeks

  2. Safety will be assessed by clinically significant changes in physical and neurological examination findings

    ART5803 safety, will be assessed by clinically significant changes in physical and neurological examination findings compared with placebo.

    Measured: 12 weeks

  3. Safety by assessed by clinically significant changes in vital signs

    ART5803 safety, will be assessed by clinically significant changes in vital signs including systolic and diastolic blood pressure, pulse rate, respiration rate, and body temperature as compared to placebo.

    Measured: 12 weeks

  4. Safety by assessed by clinically significant changes in clinical laboratory outcomes

    ART5803 safety, will be assessed by clinically significant changes in clinical laboratory outcomes including clinical chemistry, hematology, coagulation, and urinalysis as compared to placebo.

    Measured: 12 weeks

  5. Safety by assessed by clinically significant changes in 12-lead ECG findings

    ART5803 safety, will be assessed by clinically significant changes 12-lead ECG findings as compared to placebo.

    Measured: 12 weeks

  6. Safety by assessed by clinically significant changes in concomitant medications

    ART5803 safety, will be assessed by clinically significant changes in concomitant medications as compared to placebo.

    Measured: 12 weeks

  7. Safety by assessed by clinically significant changes in presence of anti-drug antibodies (ADAs)

    ART5803 safety, will be assessed by clinically significant changes in presence of anti-drug antibodies (ADAs) as compared to placebo.

    Measured: 12 weeks

  8. Safety will be assessed by incidence of dose-limiting toxicity (DLTs)

    ART5803 safety, will be assessed by incidence of dose-limiting toxicity (DLTs) as compared to placebo.

    Measured: 12 weeks

  9. Safety will be assessed by change in suicidal tendency measured by Columbia-Suicide Severity Rating Scale (C-SSRS)

    ART5803 safety, will be assessed by change in suicidal tendency as measured by the incidence of positive responses (Yes) to Item 4 or 5 on the Columbia-Suicide Severity Rating Scale (C-SSRS) as compared to placebo.

    Measured: 12 weeks

Secondary outcomes (9)

  1. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by maximum concentration (Cmax) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  2. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by minimum concentration (Cmin) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  3. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by time at which Cmax is observed (tmax) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  4. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by area under the curve from time 0 to the last measurable concentration (AUC0-t) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  5. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by area under the curve from time 0 extrapolated to infinity (AUC0-∞) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  6. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by the half-life (t½) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  7. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by the volume of distribution (Vd) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  8. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To characterize and compare the PK profile of single ascending IV doses and multiple ascending IV doses of ART5803 as measured by clearance (CL) as compared with placebo.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

  9. To assess the pharmacokinetics (PK) of single ascending IV doses and multiple ascending IV doses of ART5803 compared with placebo

    To asses the CSF/serum ratio of ART5803 at multiple time points.

    Measured: Serum collected over 96 hours after administration, Day 8, Day 15, Day 29, Day 43, Day 57, Day 71, and Day 85; CSF collected 48 hours after administration, Day 29 and Day 43

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted28 Aug 2024
  2. Study start19 Sep 2024
  3. Primary completion11 Sep 2025
  4. Study completion31 Oct 2025

Resources

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 1
Primary purpose
Other
Allocation
Randomised
Intervention model
Sequential
Model description
This study will include up to 5 cohorts in Part 1 (SAD) and up to 3 cohorts in Part 2 (MAD). Each cohort will consist of 8 participants who will receive a single IV dose of either ART5803 or placebo (6 active \[ART5803\], 2 placebo) based on the individual participant's randomly assigned treatment.
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
64 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06575153
Sponsor's protocol ID
ART5803-101
Status last verified
Apr 2026
First submitted
15 Aug 2024
Last updated
27 Apr 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 1 study testing ART5803 in people with Autoimmune Encephalitis, run by Arialys Therapeutics at 1 site in Australia.

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 9 inclusion and 26 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: finished, as of the sponsor's last update on 27 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Australia. 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. 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 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Safety will be assessed by the incidence and severity of treatment-emergent adverse events (TEAEs) (time frame: 12 weeks). The study lists 9 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06575153.

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 27 Apr 2026.

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