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    Clinical Trial Results:
    A Phase II Randomized, Double-Blind, Placebo-Controlled Study of the Efficacy, Safety, and Tolerability of Arbaclofen Administered for the Treatment of Social Function in Children and Adolescents with Autism Spectrum Disorders.

    Summary
    EudraCT number
    		 2018-000942-21
    Trial protocol
    		 GB  
    Global end of trial date
    27 Jan 2023

    Results information
    Results version number
    		 v1(current)
    This version publication date
    20 Jun 2026
    First version publication date
    20 Jun 2026
    Other versions
    Summary report(s)
    		 SUMMARY
    primary paper

    Trial information

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    Trial identification
    Sponsor protocol code
    AIMS-2-CT1
    Additional study identifiers
    ISRCTN number
    		 -
    US NCT number
    		 NCT03682978
    WHO universal trial number (UTN)
    		 -
    Sponsors
    Sponsor organisation name
    Hospital General Universitario Gregorio Marañón
    Sponsor organisation address
    C/ Dr Esquerdo 46, Madrid, Spain, 28007
    Public contact
    Professor Andre Strydom, Institute of Psychiatry, Psychology and Neuroscience, King's College London, +44 7894551353, andre.strydom@kcl.ac.uk
    Scientific contact
    Professor Andre Strydom, Institute of Psychiatry, Psychology and Neuroscience, King's College London, +34 914265006, carango@hggm.es
    Paediatric regulatory details
    Is trial part of an agreed paediatric investigation plan (PIP)
    No
    Does article 45 of REGULATION (EC) No 1901/2006 apply to this trial?
    No
    Does article 46 of REGULATION (EC) No 1901/2006 apply to this trial?
    No
    Results analysis stage
    Analysis stage
    Final
    Date of interim/final analysis
    27 Jan 2024
    Is this the analysis of the primary completion data?
    Yes
    Primary completion date
    27 Jan 2023
    Global end of trial reached?
    Yes
    Global end of trial date
    27 Jan 2023
    Was the trial ended prematurely?
    No
    General information about the trial
    Main objective of the trial
    The overall goal of this project is to improve patient outcomes. For this study the primary objective is to examine the effect of Arbaclofen compared to placebo on social function in children and adolescents (age 5 - 17) with Autism spectrum disorders.
    Protection of trial subjects
    Patients were protected by being treated by professional and experienced clinicians and research workers. The protocol was followed at all times and when protocol procedures were difficult or strenuous, the study teams and clinical teams have provided breaks and reassurance. If patients did not want particular protocol procedures (such as blood taking) they were not included in the study. If patients showed resistance after initially providing assent, this was handled according to good practice, and either the procedures were stopped and the patient excluded, or the patient was sufficiently reassured and calm when proceeding.
    Background therapy
    		 -
    Evidence for comparator
    		 -
    Actual start date of recruitment
    01 Nov 2018
    Long term follow-up planned
    No
    Independent data monitoring committee (IDMC) involvement?
    Yes
    Population of trial subjects
    Number of subjects enrolled per country
    Country: Number of subjects enrolled
    United Kingdom: 25
    Country: Number of subjects enrolled
    France: 22
    Country: Number of subjects enrolled
    Spain: 77
    Worldwide total number of subjects
    124
    EEA total number of subjects
    99
    Number of subjects enrolled per age group
    In utero
    0
    Preterm newborn - gestational age < 37 wk
    0
    Newborns (0-27 days)
    0
    Infants and toddlers (28 days-23 months)
    0
    Children (2-11 years)
    54
    Adolescents (12-17 years)
    70
    Adults (18-64 years)
    0
    From 65 to 84 years
    0
    85 years and over
    0

    Subject disposition

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    Recruitment
    Recruitment details
    		 FPFV: 19Sep20219 LPLV: 27Jan2023

    Pre-assignment
    Screening details
    		 18 patients were screen failures or discontinued before randomization - COVID restrictions government (n=1) - Participant requested to discontinue (n=4) - Screening failure, patient does not meet all in-exclusion criteria (n=12) - Rescreening (n=1)

    Period 1
    Period 1 title
    overall trial (overall period)
    Is this the baseline period?
    		 Yes
    Allocation method
    Randomised - controlled
    Blinding used
    		 Double blind
    Roles blinded
    		 Subject, Investigator, Monitor, Data analyst, Carer, Assessor
    Blinding implementation details
    all study team members dealing directly with the subject were blinded, as was the subject. the only person not blinded was the pharmacist handing out the medication, and the unblinded monitor, checking randomisation procedures.

    Arms
    Arm title
    		 placebo and arbaclofen
    Arm description
    		 reporting both arms together
    Arm type
    		 combined

    Investigational medicinal product name
    arbaclofen
    Investigational medicinal product code
    Other name
    Pharmaceutical forms
    Tablet
    Routes of administration
    Oral use
    Dosage and administration details
    orally disintegrating tabs, round, white and bevelled edges placebo: 0mg arbaclofen: 5mg, 10mg, 15mg and 20mg

    Number of subjects in period 1 [1]
    		placebo and arbaclofen
    Started
    123
    Completed
    116
    Not completed
    7
         Physician decision
    1
         too stressful
    2
         other
    1
         Lost to follow-up
    2
         Protocol deviation
    1
    Notes
    [1] - The number of subjects reported to be in the baseline period are not the same as the worldwide number enrolled in the trial. It is expected that these numbers will be the same.
    Justification: During the study, a number of participants were identified as screening failures. Hence the number of subjects in the baseline period is not equal to the worldwide number enrolled in the trial.

    Baseline characteristics

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    Baseline characteristics reporting groups
    Reporting group title
    overall trial
    Reporting group description
    		 -

    Reporting group values
    		 overall trial Total
    Number of subjects
    		 123 123
    Age categorical
    Units: Subjects
        Adolescents (12-17 years)
    		 66 66
        Children (5-11)
    		 57 57
    Age continuous
    Units: years
        arithmetic mean (standard deviation)
    		 12 ( 3.2 ) -
    Gender categorical
    Units: Subjects
        Female
    		 102 102
        Male
    		 21 21
    Subject analysis sets

    Subject analysis set title
    primary endpoint
    Subject analysis set type
    		 Intention-to-treat
    Subject analysis set description
    A total of 59 ITT patients in arbaclofen vs 63 in placebo were analysed. The Socialization domain of the Vineland-3 was chosen as the primary outcome. We, therefore, explored changes after treatment in each treatment arm for the Socialization Standard score (with mean 100 and standard deviation 15 – Table 11.4.1-1) and the average of its three subdomains (i.e. play and leisure, social skills and interpersonal relationships – Table 11.4.1-2) Growth Scale Values.

    Subject analysis sets values
    		 primary endpoint
    Number of subjects
    122
    Age categorical
    Units: Subjects
        Adolescents (12-17 years)
    66
        Children (5-11)
    57
    Age continuous
    Units: years
        arithmetic mean (standard deviation)
    12 ( 3.2 )
    Gender categorical
    Units: Subjects
        Female
    102
        Male
    20

    End points

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    End points reporting groups
    Reporting group title
    placebo and arbaclofen
    Reporting group description
    		 reporting both arms together

    Subject analysis set title
    primary endpoint
    Subject analysis set type
    		 Intention-to-treat
    Subject analysis set description
    A total of 59 ITT patients in arbaclofen vs 63 in placebo were analysed. The Socialization domain of the Vineland-3 was chosen as the primary outcome. We, therefore, explored changes after treatment in each treatment arm for the Socialization Standard score (with mean 100 and standard deviation 15 – Table 11.4.1-1) and the average of its three subdomains (i.e. play and leisure, social skills and interpersonal relationships – Table 11.4.1-2) Growth Scale Values.

    Primary: Vineland Socialization Standard Score

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    End point title
    		 Vineland Socialization Standard Score [1]
    End point description
    End point type
    Primary
    End point timeframe
    standard score of the socialization domain, adjusting for baseline, age, sex and site
    Notes
    [1] - No statistical analyses have been specified for this primary end point. It is expected there is at least one statistical analysis for each primary end point.
    Justification: The statistical analysis corresponding to this part of the results is clearly described in the paper - Parellada et al, 2026 doi: 10.1016/j.eclinm.2026.103760
    End point values
    		 placebo and arbaclofen primary endpoint
    Number of subjects analysed
    122
    122
    Units: number
        arithmetic mean (standard deviation)
    72 ( 18 )
    72 ( 18 )
    No statistical analyses for this end point

    Adverse events

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    Adverse events information [1]
    Timeframe for reporting adverse events
    overall trial
    Assessment type
    		 Systematic
    Dictionary used for adverse event reporting
    Dictionary name
    		 MedDRA
    Dictionary version
    21
    Reporting groups
    Reporting group title
    arbaclofen
    Reporting group description
    		 -

    Reporting group title
    Placebo
    Reporting group description
    		 -

    Serious adverse events
    		 arbaclofen Placebo
    Total subjects affected by serious adverse events
         subjects affected / exposed
    0 / 49 (0.00%)
    0 / 63 (0.00%)
         number of deaths (all causes)
    0
    0
         number of deaths resulting from adverse events
    0
    0
    Frequency threshold for reporting non-serious adverse events: 5%
    Non-serious adverse events
    		 arbaclofen Placebo
    Total subjects affected by non serious adverse events
         subjects affected / exposed
    0 / 49 (0.00%)
    0 / 63 (0.00%)
    Notes
    [1] - There are no non-serious adverse events recorded for these results. It is expected that there will be at least one non-serious adverse event reported.
    Justification: The adverse events corresponding to these results are clearly described in the paper - Parellada et al, 2026 doi: 10.1016/j.eclinm.2026.103760

    More information

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    Substantial protocol amendments (globally)
    Were there any global substantial amendments to the protocol? Yes
    Date
    Amendment
    17 Sep 2019
    substantial amendment #1 - protocol 4.0 various administrative changes
    04 Feb 2020
    substantial amendment #2 - protocol 5.0 extension expiry date medication
    02 Sep 2020
    substantial amendment #3 - protocol 6.0 remote assessments
    16 Nov 2020
    substantial amendment #4 - protocol 7.1 adding digital biomarkers
    23 Feb 2021
    substantial amendment #5 - protocol 7.2 1) in the protocol, tables 4.1-1, 4.1-2 and appendix 5 have been corrected to indicate that the collection of the digital biomarkers equipment will be done on visit 7 (and not 8) 2) This change has also been reflected in the consent form for parents and +18 (figure) 3) in the protocol, we have substituted San Sebastian for the centres in Castille-Leon
    19 Apr 2022
    non-substantial amendment #6 to extend recruitment - protocol v9.0 - approved by Spain

    Interruptions (globally)
    Were there any global interruptions to the trial? Yes
    Date
    Interruption
    Restart date
    13 Mar 2020
    Corona
    -

    Limitations and caveats
    Limitations of the trial such as small numbers of subjects analysed or technical problems leading to unreliable data.
    Efficacy results have yielded mixed results. We hypothesized that treatment with arbaclofen would improve social function as measured with the Vineland-3 Socialization domain. Our results, however, show that both arbaclofen and placebo-treated patien
    For support, Contact us.
    The status and protocol content of GB trials is no longer updated since 1 January 2021. For the UK, as of 31 January 2021, EU Law applies only to the territory of Northern Ireland (NI) to the extent foreseen in the Protocol on Ireland/NI. Legal notice
    As of 31 January 2023, all EU/EEA initial clinical trial applications must be submitted through CTIS . Updated EudraCT trials information and information on PIP/Art 46 trials conducted exclusively in third countries continues to be submitted through EudraCT and published on this website.

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