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    Clinical Trial Results:
    A Phase 3, Multicenter, Randomized, Double-Blinded, Placebo-Controlled Trial to Evaluate the Efficacy and the Safety of Efgartigimod (ARGX-113) PH20 Subcutaneous in Adult Patients With Primary Immune Thrombocytopenia

    Summary
    EudraCT number
    		 2020-004032-21
    Trial protocol
    		 IE   PT   DE   BG   NO   DK   GR   IT   FR   RO   ES  
    Global end of trial date
    09 Oct 2023

    Results information
    Results version number
    		 v1(current)
    This version publication date
    24 Oct 2024
    First version publication date
    24 Oct 2024
    Other versions

    Trial information

    		 Close Top of page
    Trial identification
    Sponsor protocol code
    ARGX-113-2004
    Additional study identifiers
    ISRCTN number
    		 -
    US NCT number
    		 NCT04687072
    WHO universal trial number (UTN)
    		 -
    Sponsors
    Sponsor organisation name
    argenx BV
    Sponsor organisation address
    Industriepark Zwijnaarde 7, Zwijnaarde (Ghent), Belgium, 9052
    Public contact
    Regulatory manager, argenx BV, regulatory@argenx.com
    Scientific contact
    Regulatory manager, argenx BV, regulatory@argenx.com
    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
    31 Jul 2024
    Is this the analysis of the primary completion data?
    No
    Global end of trial reached?
    Yes
    Global end of trial date
    09 Oct 2023
    Was the trial ended prematurely?
    No
    General information about the trial
    Main objective of the trial
    To evaluate the efficacy of efgartigimod PH20 SC compared to placebo PH20 SC in achieving a sustained platelet count response in participants with chronic primary ITP, with a sustained platelet count response defined as platelet counts of ≥50×10^9/L for at least 4 of the 6 visits between week 19 and week 24 of the trial.
    Protection of trial subjects
    This study was conducted in accordance with the protocol and consensus ethical principles derived from international guidelines, including the Declaration of Helsinki, applicable International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use Good Clinical Practice guidelines, and applicable laws and regulations. The sponsor appointed an independent Data and Safety Monitoring Board (DSMB) consisting of clinical experts and a statistician not involved in the study management. The DSMB reviewed all unblinded safety and immunoglobulin (Ig)G data as specified in the DSMB charter.
    Background therapy
    		 Participants were permitted to continue ≥1 protocol-specified concurrent ITP therapy if at a stable dosage and frequency for ≥4 weeks before randomization.
    Evidence for comparator
    		 -
    Actual start date of recruitment
    16 Dec 2020
    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
    Australia: 7
    Country: Number of subjects enrolled
    Argentina: 4
    Country: Number of subjects enrolled
    Bulgaria: 4
    Country: Number of subjects enrolled
    Chile: 3
    Country: Number of subjects enrolled
    China: 30
    Country: Number of subjects enrolled
    Georgia: 11
    Country: Number of subjects enrolled
    Greece: 6
    Country: Number of subjects enrolled
    Ireland: 1
    Country: Number of subjects enrolled
    Italy: 6
    Country: Number of subjects enrolled
    Japan: 9
    Country: Number of subjects enrolled
    Jordan: 20
    Country: Number of subjects enrolled
    Korea, Republic of: 6
    Country: Number of subjects enrolled
    Mexico: 1
    Country: Number of subjects enrolled
    New Zealand: 1
    Country: Number of subjects enrolled
    Norway: 2
    Country: Number of subjects enrolled
    Poland: 6
    Country: Number of subjects enrolled
    Portugal: 3
    Country: Number of subjects enrolled
    Romania: 9
    Country: Number of subjects enrolled
    Russian Federation: 7
    Country: Number of subjects enrolled
    South Africa: 6
    Country: Number of subjects enrolled
    Thailand: 14
    Country: Number of subjects enrolled
    Tunisia: 13
    Country: Number of subjects enrolled
    Türkiye: 23
    Country: Number of subjects enrolled
    United Kingdom: 6
    Country: Number of subjects enrolled
    United States: 9
    Worldwide total number of subjects
    207
    EEA total number of subjects
    37
    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)
    0
    Adolescents (12-17 years)
    0
    Adults (18-64 years)
    169
    From 65 to 84 years
    38
    85 years and over
    0

    Subject disposition

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    Recruitment
    Recruitment details
    		 A regionally diverse participant population was enrolled (including but not limited to North America, East Asia, Europe, and the rest of world [ROW]).

    Pre-assignment
    Screening details
    		 A total of 207 participants were randomized to IMP: 137 participants in the efgartigimod PH20 subcutaneous (SC) arm and 70 participants in the placebo PH20 SC arm.

    Period 1
    Period 1 title
    Overall Study (overall period)
    Is this the baseline period?
    		 Yes
    Allocation method
    Randomised - controlled
    Blinding used
    		 Double blind
    Roles blinded
    		 Investigator, Subject

    Arms
    Are arms mutually exclusive
    Yes

    Arm title
    		 Efgartigimod PH20 SC
    Arm description
    		 Participants receiving efgartigimod PH20 SC treatment.
    Arm type
    		 Experimental

    Investigational medicinal product name
    Efgartigimod PH20 SC
    Investigational medicinal product code
    ARGX-113
    Other name
    Pharmaceutical forms
    Solution for injection
    Routes of administration
    Subcutaneous use
    Dosage and administration details
    Subcutaneous injection with efgartigimod PH20 SC.

    Arm title
    		 Placebo PH20 SC
    Arm description
    		 Participants receiving placebo PH20 SC treatment.
    Arm type
    		 Placebo

    Investigational medicinal product name
    Placebo PH20 SC
    Investigational medicinal product code
    Other name
    Pharmaceutical forms
    Solution for injection
    Routes of administration
    Subcutaneous use
    Dosage and administration details
    Subcutaneous injection with placebo PH20 SC.

    Number of subjects in period 1
    		Efgartigimod PH20 SC Placebo PH20 SC
    Started
    137
    70
    Completed
    113
    62
    Not completed
    24
    8
         Adverse event, serious fatal
    1
    -
         Physician decision
    1
    -
         Adverse event, non-fatal
    2
    -
         Requires prohibited medication
    2
    -
         Pregnancy
    1
    -
         Miscellaneous
    4
    1
         Withdrawal of consent
    11
    6
         Lack of efficacy
    2
    1

    Baseline characteristics

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    Baseline characteristics reporting groups
    Reporting group title
    Efgartigimod PH20 SC
    Reporting group description
    		 Participants receiving efgartigimod PH20 SC treatment.

    Reporting group title
    Placebo PH20 SC
    Reporting group description
    		 Participants receiving placebo PH20 SC treatment.

    Reporting group values
    		 Efgartigimod PH20 SC Placebo PH20 SC Total
    Number of subjects
    		 137 70 207
    Age categorical
    Units: Subjects
    Age continuous
    Units: years
        arithmetic mean (standard deviation)
    		 47.3 ( 17.22 ) 50.0 ( 15.29 ) -
    Gender categorical
    Units: Subjects
        Female
    		 88 43 131
        Male
    		 49 27 76
    Ethnicity
    Units: Subjects
        Hispanic or Latino
    		 8 2 10
        Not Hispanic or Latino
    		 129 68 197
        Unknown or Not Reported
    		 0 0 0
    Race
    Units: Subjects
        Asian
    		 44 18 62
        Black or African American
    		 4 2 6
        White
    		 88 49 137
        Other
    		 1 1 2

    End points

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    End points reporting groups
    Reporting group title
    Efgartigimod PH20 SC
    Reporting group description
    		 Participants receiving efgartigimod PH20 SC treatment.

    Reporting group title
    Placebo PH20 SC
    Reporting group description
    		 Participants receiving placebo PH20 SC treatment.

    Primary: Percentage of Participants With Chronic Immune Thrombocytopenia (ITP) With a Sustained Platelet Count Response Between Weeks 19 and 24

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    End point title
    		 Percentage of Participants With Chronic Immune Thrombocytopenia (ITP) With a Sustained Platelet Count Response Between Weeks 19 and 24
    End point description
    A participant was considered a responder for this endpoint (i.e., had a sustained platelet count response) if the participant had platelet counts of ≥50 × 10^9/L for ≥4 of the 6 analysis visits between Weeks 19 and 24. Full Analysis Set (FAS)-Chronic: Participants from the FAS (all randomized participants) including only participants with chronic ITP.
    End point type
    Primary
    End point timeframe
    Up to 6 weeks (between Weeks 19 and 24)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    124
    68
    Units: percentage of participants
        number (not applicable)
    13.7
    16.2
    Statistical analysis title
    		 Efgartigimod PH20 SC versus (vs.) Placebo PH20 SC
    Statistical analysis description
    The adjusted difference in percentages and 95% confidence interval (CI) (Klingenberg approach) were presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    192
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.5081 [1]
    Method
    		 Cochran-Mantel-Haenszel
    Parameter type
    		 Difference in percentage
    Point estimate
    -3.5
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -14.7
         upper limit
    		 7
    Notes
    [1] - The p-value was calculated using the Cochran-Mantel-Haenszel test used in the hierarchical testing procedure.

    Secondary: Extent of Disease Control Over the 24-Week Treatment Period in the Chronic ITP Population

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    End point title
    		 Extent of Disease Control Over the 24-Week Treatment Period in the Chronic ITP Population
    End point description
    Extent of disease control was defined as the number of cumulative weeks over the planned 24-week treatment period with platelet counts of ≥50×10^9/L in the chronic ITP population. FAS-Chronic: Participants from the FAS (all randomized participants) including only participants with chronic ITP.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    124
    68
    Units: weeks
        median (full range (min-max))
    0.5 (0 to 24)
    0.0 (0 to 23)
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The Hodges-Lehmann estimator of the treatment difference and 95% CI are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    192
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.4925 [2]
    Method
    		 Wilcoxon (Mann-Whitney)
    Parameter type
    		 Location shift
    Point estimate
    0
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 0
         upper limit
    		 0
    Notes
    [2] - The p-value was calculated using the stratified Mann-Whitney test used in the hierarchical testing procedure.

    Secondary: Percentage of Participants in the Overall Population (Chronic and Persistent ITP) With a Sustained Platelet Count Response Between Weeks 19 and 24

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    End point title
    		 Percentage of Participants in the Overall Population (Chronic and Persistent ITP) With a Sustained Platelet Count Response Between Weeks 19 and 24
    End point description
    A participant was considered a responder for this endpoint (i.e., had a sustained platelet count response) if the participant had platelet counts of ≥50 × 10^9/L for ≥4 of the 6 analysis visits between Weeks 19 and 24. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 6 weeks (between Weeks 19 and 24)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
        number (not applicable)
    16.1
    15.7
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The adjusted difference in percentages and 95% CI (Klingenberg approach) were presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.9314 [3]
    Method
    		 Cochran-Mantel-Haenszel
    Parameter type
    		 Difference in percentage
    Point estimate
    -0.5
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -11.7
         upper limit
    		 10
    Notes
    [3] - The p-value was calculated using the Cochran-Mantel-Haenszel test used in the hierarchical testing procedure.

    Secondary: Percentage of Participants in the Overall Population With Sustained Platelet Count Response Between Weeks 17 and 24

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    End point title
    		 Percentage of Participants in the Overall Population With Sustained Platelet Count Response Between Weeks 17 and 24
    End point description
    A participant was considered a responder for this endpoint (i.e., had a sustained platelet count response) if the participant had platelet counts of ≥50 × 10^9/L for ≥6 of the 8 analysis visits between weeks 17 and 24. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 8 weeks (between Weeks 17 and 24)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
        number (not applicable)
    12.4
    14.3
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The adjusted difference in percentage and 95% CI (Klingenberg approach) are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.7379 [4]
    Method
    		 Cochran-Mantel-Haenszel
    Parameter type
    		 Difference in percentage
    Point estimate
    -1.7
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -12.4
         upper limit
    		 8.2
    Notes
    [4] - The Cochran-Mantel-Haenszel test p-value was used in the hierarchical testing procedure.

    Secondary: Percentage of Participants in the Overall Population Achieving Overall Platelet Count Response at Any Time During the 24-week Treatment Period

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    End point title
    		 Percentage of Participants in the Overall Population Achieving Overall Platelet Count Response at Any Time During the 24-week Treatment Period
    End point description
    A participant was considered a responder for this endpoint (i.e., had an overall platelet count response) if the participant had platelet counts of ≥50 × 10^9/L for ≥4 analysis visits at any time during the 24-week treatment period. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
        number (not applicable)
    29.9
    25.7
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    4.2
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -9.3
         upper limit
    		 16.8

    Secondary: Extent of Disease Control Until Week 12 in the Overall Population

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    End point title
    		 Extent of Disease Control Until Week 12 in the Overall Population
    End point description
    Extent of disease control was defined as the number of cumulative weeks until Week 12 with platelet counts of ≥50×10^9/L in the overall population.
    End point type
    Secondary
    End point timeframe
    Up to 12 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: weeks
        median (full range (min-max))
    0.00 (0.00 to 12.00)
    0.00 (0.00 to 11.00)
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The Hodges-Lehmann estimator of the treatment difference and 95% CI are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.726 [5]
    Method
    		 Wilcoxon (Mann-Whitney)
    Parameter type
    		 Location shift
    Point estimate
    0
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 0
         upper limit
    		 0
    Notes
    [5] - The p-value was calculated using the stratified Mann-Whitney test.

    Secondary: Percentage of Participants in the Overall Population Achieving Overall Platelet Count Response at Any Time Until Week 12

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    End point title
    		 Percentage of Participants in the Overall Population Achieving Overall Platelet Count Response at Any Time Until Week 12
    End point description
    A participant was considered a responder for this endpoint (i.e., had an overall platelet count response) if the participant had platelet counts of ≥50 × 10^9/L for ≥4 analysis visits at any time until Week 12. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 12 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
        number (not applicable)
    18.2
    15.7
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    2.5
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -9.6
         upper limit
    		 13

    Secondary: Mean Change From Baseline in Platelet Count at Each Visit in the Overall Population

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    End point title
    		 Mean Change From Baseline in Platelet Count at Each Visit in the Overall Population
    End point description
    Change from Baseline at time point t = value at time point t - Baseline value. Baseline was defined as the last available value prior to first administration of the investigational medicinal product (IMP). Values of "99999" indicate standard deviation could not be calculated as a single participant was analyzed. FAS: All randomized participants with available data.
    End point type
    Secondary
    End point timeframe
    Baseline and Weeks 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, Safety and Efficacy Follow-up Visit 1 (SEFU1) (up to Week 29), and SEFU2 (up to Week 33)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    136
    69
    Units: platelets x10^9/L
    arithmetic mean (standard deviation)
        Week 1 (N = 136, 69)
    13.84 ( 41.150 )
    8.82 ( 34.355 )
        Week 2 (N = 135, 68)
    16.62 ( 49.408 )
    23.54 ( 85.005 )
        Week 3 (N = 133, 69)
    17.07 ( 39.855 )
    19.22 ( 71.947 )
        Week 4 (N = 132, 68)
    12.39 ( 37.886 )
    9.31 ( 26.813 )
        Week 5 (N = 129, 67)
    18.14 ( 54.335 )
    12.24 ( 30.059 )
        Week 6 (N = 127, 65)
    34.61 ( 112.204 )
    16.35 ( 40.891 )
        Week 7 (N = 126, 67)
    28.25 ( 107.932 )
    13.46 ( 41.876 )
        Week 8 (N = 126, 66)
    21.77 ( 52.308 )
    16.57 ( 42.508 )
        Week 9 (N = 123, 64)
    19.90 ( 54.542 )
    20.42 ( 53.488 )
        Week 10 (N = 119, 66)
    21.73 ( 47.685 )
    15.42 ( 33.119 )
        Week 11 (N = 122, 63)
    20.13 ( 42.193 )
    14.54 ( 25.588 )
        Week 12 (N = 120, 62)
    21.02 ( 43.882 )
    22.28 ( 56.173 )
        Week 13 (N = 118, 63)
    22.29 ( 44.654 )
    15.51 ( 37.651 )
        Week 14 (N = 119, 65)
    23.60 ( 47.521 )
    24.04 ( 55.678 )
        Week 15 (N = 116, 59)
    21.30 ( 45.776 )
    28.05 ( 67.897 )
        Week 16 (N = 113, 58)
    30.32 ( 71.553 )
    23.09 ( 46.154 )
        Week 17 (N = 112, 58)
    25.12 ( 54.747 )
    30.05 ( 56.581 )
        Week 18 (N = 115, 60)
    28.54 ( 53.115 )
    31.64 ( 57.309 )
        Week 19 (N = 114, 62)
    33.86 ( 59.323 )
    37.26 ( 68.832 )
        Week 20 (N = 107, 61)
    30.87 ( 55.342 )
    25.85 ( 48.409 )
        Week 21 (N = 108, 59)
    30.04 ( 61.438 )
    26.23 ( 50.323 )
        Week 22 (N = 110, 61)
    33.26 ( 61.558 )
    29.23 ( 55.175 )
        Week 23 (N = 111, 60)
    29.51 ( 53.437 )
    24.89 ( 41.103 )
        Week 24 (N = 113, 59)
    25.51 ( 52.203 )
    24.91 ( 42.972 )
        SEFU1 (N = 9, 1)
    40.44 ( 64.860 )
    48.70 ( 99999 )
        SEFU2 (N = 10, 2)
    30.00 ( 35.011 )
    56.25 ( 85.206 )
    No statistical analyses for this end point

    Secondary: Time to Platelet Count Response in the Overall Population

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    End point title
    		 Time to Platelet Count Response in the Overall Population
    End point description
    Time to platelet count response, defined as the time to have 2 consecutive platelet counts of ≥50 × 10^9/L via Kaplan-Meier estimates. Values of "999999" indicate the median and/or confidence intervals were not calculable due to insufficient event data. FAS: All randomized participants. Participants with no occurrence of platelet count response, early discontinuation of treatment, or dose and/or frequency of concurrent ITP therapy increased or a new ITP therapy were censored. If multiple censoring conditions apply, the earliest censoring date is considered.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137 [6]
    70 [7]
    Units: days
        median (confidence interval 95%)
    999999 (155.0 to 999999)
    999999 (999999 to 999999)
    Notes
    [6] - Median and upper confidence interval were not calculable due to fewer than 50% events.
    [7] - Median and confidence intervals were not calculable due to insufficient event data.
    No statistical analyses for this end point

    Secondary: Extent of Disease Control Over the 24-Week Treatment Period in the Overall Population

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    End point title
    		 Extent of Disease Control Over the 24-Week Treatment Period in the Overall Population
    End point description
    Extent of disease control was defined as the number of cumulative weeks over the planned 24-week treatment period with platelet counts of ≥30×10^9/L with at least ≥20×10^9/L above Baseline in the overall population. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: weeks
        median (full range (min-max))
    1.0 (0 to 24)
    1.0 (0 to 24)
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The Hodges-Lehmann estimator of the treatment difference and 95% CI are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.2929 [8]
    Method
    		 Wilcoxon (Mann-Whitney)
    Parameter type
    		 Location shift
    Point estimate
    0
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 0
         upper limit
    		 1
    Notes
    [8] - The p-value was calculated using the stratified Mann-Whitney test.

    Secondary: Extent of Disease Control Over the 24-Week Treatment Period in the Overall Population for Participants With Baseline Platelet Count of <15×10^9/L

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    End point title
    		 Extent of Disease Control Over the 24-Week Treatment Period in the Overall Population for Participants With Baseline Platelet Count of <15×10^9/L
    End point description
    Extent of disease control was defined as the number of cumulative weeks over the planned 24-week treatment period with platelet counts of ≥30×10^9/L with at least ≥20×10^9/L above Baseline in the overall population. FAS: All randomized participants with Baseline Platelet Count of <15×10^9/L.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    59
    35
    Units: weeks
        median (full range (min-max))
    1.0 (0.0 to 23)
    0.0 (0.0 to 24)
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The Hodges-Lehmann estimator of the treatment difference and 95% CI are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    94
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.1475 [9]
    Method
    		 Wilcoxon (Mann-Whitney)
    Parameter type
    		 Location shift
    Point estimate
    0
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 0
         upper limit
    		 1
    Notes
    [9] - The p-value was calculated using the stratified Mann-Whitney test.

    Secondary: Number of the World Health Organization (WHO)-Classified Bleeding Events (Grade ≥1) in the Overall Population

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    End point title
    		 Number of the World Health Organization (WHO)-Classified Bleeding Events (Grade ≥1) in the Overall Population
    End point description
    Assessed using the WHO bleeding scale. The WHO bleeding scale is a five-point scale where Grade 0 = no bleeding; Grade 1 = petechial bleeding; Grade 2 = mild blood loss; Grade 3 = gross blood loss (requires transfusion); and Grade 4 = debilitating blood loss, associated with fatality. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: bleeding events
        median (full range (min-max))
    9.0 (0.00 to 24)
    10.0 (0.00 to 24)
    Statistical analysis title
    		 WHO Classified Bleeding Event Grade ≥1
    Statistical analysis description
    The Hodges-Lehmann estimator of the treatment difference and 95% CI are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 superiority
    P-value
    		 = 0.7677 [10]
    Method
    		 Wilcoxon (Mann-Whitney)
    Parameter type
    		 Location shift
    Point estimate
    0
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -2
         upper limit
    		 2
    Notes
    [10] - The p-value was calculated using the stratified Mann-Whitney test used in the hierarchical testing procedure.

    Secondary: Percentage of Participants With a Platelet Count International Working Group (IWG) Response

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    End point title
    		 Percentage of Participants With a Platelet Count International Working Group (IWG) Response
    End point description
    IWG complete response was defined as platelet counts of ≥100 × 10^9/L and the absence of bleeding events (WHO Grading = 0 [no bleeding]) for at least 2 separate, consecutive analysis visits at least 7 days apart. IWG response was defined as platelet counts of ≥30 × 10^9/L and a 2-fold increase of platelet count from Baseline and the absence of bleeding events (WHO grading = 0) for at least 2 separate, consecutive analysis visits that were at least 7 days apart. Initial response was defined as platelet counts of ≥30 × 10^9/L and a 2-fold increase from the Baseline platelet count at analysis visit 5. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
    number (not applicable)
        IWG Complete Response
    10.2
    11.4
        IWG Response
    28.5
    20.0
        Initial Response
    19.7
    17.1
    Statistical analysis title
    		 IWG Complete Response
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    -1.2
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -11.8
         upper limit
    		 7.3
    Statistical analysis title
    		 IWG Response
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    8.5
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -4.6
         upper limit
    		 20.2
    Statistical analysis title
    		 Initial Response
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    2.6
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -9.7
         upper limit
    		 13.3

    Secondary: Rate of Receipt of Rescue Therapy (Rescue Per Participant Per Month) in the Overall Population

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    End point title
    		 Rate of Receipt of Rescue Therapy (Rescue Per Participant Per Month) in the Overall Population
    End point description
    Rescue therapy was defined as an occurrence where the participant needed treatment with 1 or more rescue treatments. An occurrence was defined as a period of maximum 5 days where 1 or more rescue treatments were administered simultaneously or consecutively to the trial participant. The following rescue treatments were permitted: methylprednisolone, dexamethasone, prednisone, normal immunoglobulins, anti-D (Rho) immunoglobins, or platelet transfusions. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 24 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: rescues per participant per month
        arithmetic mean (standard deviation)
    0.25 ( 0.553 )
    0.17 ( 0.363 )
    No statistical analyses for this end point

    Secondary: Percentage of Participants for Whom Dose and/or Frequency of Concurrent ITP Therapies Have Increased at Week 12 or Later in the Overall Population

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    End point title
    		 Percentage of Participants for Whom Dose and/or Frequency of Concurrent ITP Therapies Have Increased at Week 12 or Later in the Overall Population
    End point description
    A change in ITP therapy was defined as either an increase in the dose and/or frequency of a concurrent ITP therapy relative to Baseline or the initiation of a new concurrent ITP therapy. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Up to 13 weeks (between Weeks 12 and 24)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: percentage of participants
        number (not applicable)
    11.7
    15.7
    Statistical analysis title
    		 Efgartigimod PH20 SC vs. Placebo PH20 SC
    Statistical analysis description
    The 95% Agresti-Min CIs are presented.
    Comparison groups
    Efgartigimod PH20 SC v Placebo PH20 SC
    Number of subjects included in analysis
    207
    Analysis specification
    Pre-specified
    Analysis type
    		 other
    Method
    Parameter type
    		 Difference in percentage
    Point estimate
    -4
    Confidence interval
         level
    		 95%
         sides
    2-sided
         lower limit
    		 -15.6
         upper limit
    		 5.7

    Secondary: Change From Baseline in Functional Assessment of Chronic Illness Therapy Fatigue Scale (FACIT-Fatigue) at Week 24 in the Overall Population

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    End point title
    		 Change From Baseline in Functional Assessment of Chronic Illness Therapy Fatigue Scale (FACIT-Fatigue) at Week 24 in the Overall Population
    End point description
    The FACIT-fatigue scale is a short, 13-item, easy-to-administer tool that measures an individual's level of fatigue during his/her usual daily activities over the past week. The level of fatigue was measured by recording item responses on a 5-point Likert scale ranging from 0 "not at all" to 4 "very much". All items were summed to create a single fatigue score with a range from 0 to 52, where a higher FACIT-F score indicated more severe symptoms. A negative change score from Baseline indicated improvement in quality of life (QoL). FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Baseline and Week 24
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: score on a scale
        least squares mean (standard deviation)
    -0.025 ( 0.712 )
    0.741 ( 0.985 )
    No statistical analyses for this end point

    Secondary: Change From Baseline in Functional Assessment of Cancer Therapy Questionnaire-Th6 (Fact-Th6) at Week 24 in the Overall Population

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    End point title
    		 Change From Baseline in Functional Assessment of Cancer Therapy Questionnaire-Th6 (Fact-Th6) at Week 24 in the Overall Population
    End point description
    The FACT-Th6 uses a 5-level Likert scale (0=not at all to 4=very much), with participants rating their degree of concern in the past 7 days. The 6 selected items pertain to ability to do usual activities, worry about problems with bleeding or bruising, worry about the possibility of serious bleeding, avoidance of physical or social activity because of concern with bleeding or bruising and frustration due to the inability to carry out usual activities. All items were summed to create a single score with a range from 0 to 24, where a higher score indicated less severe symptoms. A positive change score from Baseline indicated improvement in QoL. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Baseline and Week 24
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: score on a scale
    least squares mean (standard error)
        Week 24
    0.225 ( 0.360 )
    0.359 ( 0.498 )
    No statistical analyses for this end point

    Secondary: Change From Baseline in Short Form-36 (SF-36) at Week 24 in the Overall Population

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    End point title
    		 Change From Baseline in Short Form-36 (SF-36) at Week 24 in the Overall Population
    End point description
    The SF-36 is a 36-item scale constructed to survey health-related QoL on 8 domains: limitations in physical activities due to health problems; limitations in social activities due to physical or emotional problems; limitations in usual role activities due to physical health problems; bodily pain; general mental health (psychological distress and well-being); limitations in usual role activities due to emotional problems; vitality (energy and fatigue); and general health perceptions. The scores from the 8 domains were evaluated independently and aggregated into 2 norm-based summary component measures of physical and mental health. The summary component scores could range from 0 to 100, where a higher score indicated improvement in QoL. A positive change score from Baseline indicated improvement in QoL. FAS: All randomized participants.
    End point type
    Secondary
    End point timeframe
    Baseline and Week 24
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    137
    70
    Units: score on a scale
    least squares mean (standard error)
        Week 24: Mental Component
    1.215 ( 0.620 )
    0.957 ( 0.841 )
        Week 24: Physical Component
    -0.848 ( 0.525 )
    -0.850 ( 0.712 )
    No statistical analyses for this end point

    Secondary: Incidence and Prevalence of Antibodies to Efgartigimod and/or rHuPH20 in the Overall Population

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    End point title
    		 Incidence and Prevalence of Antibodies to Efgartigimod and/or rHuPH20 in the Overall Population
    End point description
    Anti-drug antibody (ADA) incidence was defined as the percentage of participants with treatment-induced or treatment boosted ADA (denominator: number of evaluable participants). ADA prevalence was defined as the percentage of participants with treatment-unaffected ADA, treatment-induced ADA or treatment-boosted ADA (denominator: number of evaluable participants). SAF: All participants who received at least 1 dose or part of a dose including only antibody-evaluable participants.
    End point type
    Secondary
    End point timeframe
    Up to 35 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    136
    70
    Units: percentage of participants
    number (not applicable)
        Incidence of Antibodies to Efgartigimod
    5.1
    2.9
        Prevalence of Antibodies to Efgartigimod
    16.2
    7.1
        Incidence of Antibodies to rHuPH20
    41.2
    20.0
        Prevalence of Antibodies to rHuPH20
    50.0
    31.4
    No statistical analyses for this end point

    Secondary: Titers of Antibodies to Efgartigimod and/or rHuPH20 in the Overall Population

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    End point title
    		 Titers of Antibodies to Efgartigimod and/or rHuPH20 in the Overall Population
    End point description
    A titer was determined in the samples with a positive assay response. Values of "99999" indicate standard deviation could not be calculated as a single participant was analyzed. SAF: All participants who received at least 1 dose or part of a dose with available data.
    End point type
    Secondary
    End point timeframe
    Weeks 3, 7, 11, 15, 19, 23, 24, SEFU1 (up to Week 29), and SEFU2 (up to Week 33)
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    45
    16
    Units: titer
    arithmetic mean (standard deviation)
        Week 3: ADA Against Efgartigimod Titer (N = 0, 2)
    0.0 ( 0.0 )
    16.5 ( 15.50 )
        Week 7: ADA Against Efgartigimod Titer (N = 1, 3)
    1.0 ( 99999 )
    11.3 ( 10.33 )
        Week 11: ADA Against Efgartigimod Titer (N = 0, 3)
    0.0 ( 0.0 )
    6.3 ( 4.84 )
        Week 15: ADA Against Efgartigimod Titer (N = 0, 2)
    0.0 ( 0.0 )
    8.5 ( 7.50 )
        Week 19: ADA Against Efgartigimod Titer (N = 0, 0)
    0.0 ( 0.0 )
    0.0 ( 0.0 )
        Week 23: ADA Against Efgartigimod Titer (N = 0, 1)
    0.0 ( 0.0 )
    2.0 ( 99999 )
        Week 24: ADA Against Efgartigimod Titer (N = 3, 2)
    16.3 ( 8.95 )
    1.0 ( 0.00 )
        SEFU1: ADA Against Efgartigimod Titer (N = 2, 0)
    2.5 ( 1.50 )
    0.0 ( 0.0 )
        SEFU2: ADA Against Efgartigimod Titer (N = 2, 0)
    17.0 ( 15.00 )
    0.0 ( 0.0 )
        Week 3: ADA Against rHuPH20 Titer (N = 15, 11)
    12.7 ( 2.53 )
    14.1 ( 3.15 )
        Week 7: ADA Against rHuPH20 Titer (N = 23, 8)
    645.9 ( 314.79 )
    14.4 ( 4.27 )
        Week 11: ADA Against rHuPH20 Titer (N = 32, 7)
    2204.8 ( 1297.43 )
    11.4 ( 2.37 )
        Week 15: ADA Against rHuPH20 Titer (N = 34, 7)
    3209.3 ( 1325.96 )
    15.7 ( 2.02 )
        Week 19: ADA Against rHuPH20 Titer (N = 42, 11)
    3742.7 ( 1414.15 )
    49.1 ( 27.87 )
        Week 23: ADA Against rHuPH20 Titer (N = 45, 15)
    5936.6 ( 2180.33 )
    58.3 ( 27.83 )
        Week 24: ADA Against rHuPH20 Titer (N = 45, 16)
    4731.3 ( 1898.96 )
    69.1 ( 26.60 )
        SEFU1: ADA Against rHuPH20 Titer (N = 2, 0)
    5122.5 ( 5117.50 )
    0.0 ( 0.0 )
        SEFU2: ADA Against rHuPH20 Titer (N = 2, 0)
    5160.0 ( 5080.00 )
    0.0 ( 0.0 )
    No statistical analyses for this end point

    Secondary: Incidence and Prevalence of Neutralizing Antibodies (NAb) to Efgartigimod and/or rHuPH20 in the Overall Population

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    End point title
    		 Incidence and Prevalence of Neutralizing Antibodies (NAb) to Efgartigimod and/or rHuPH20 in the Overall Population
    End point description
    Samples were tested for the presence of NAb against efgartigimod and/or rHuPH20 and titers for NAb against rHuPH20. Values of "9999" indicate no participants were analyzed at that timepoint. NAb incidence is defined as the total percentage of participants with participant classification “baseline negative–postbaseline positive” and “baseline positive–postbaseline positive”. NAb prevalence is defined as the total percentage of participants with participant classification “baseline negative–postbaseline positive,” “baseline positive–postbaseline positive,” or “baseline positive–postbaseline negative”. SAF: All participants who received at least 1 dose or part of a dose with available data.
    End point type
    Secondary
    End point timeframe
    Up to 35 weeks
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    136
    70
    Units: percentage of participants
    number (not applicable)
        Incidence of NAb to Efgartigimod
    0.7
    0.0
        Prevalence of NAb to Efgartigimod
    5.1
    0.0
        Incidence of NAb to rHuPH20
    0.0
    0.0
        Prevalence of NAb to rHuPH20
    0.0
    0.0
    No statistical analyses for this end point

    Secondary: Serum Efgartigimod Trough Concentration (Ctrough) in the Overall Population

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    End point title
    		 Serum Efgartigimod Trough Concentration (Ctrough) in the Overall Population [11]
    End point description
    All pharmacokinetic (PK) samples were collected predose, on the day of IMP administration. PK Analysis Set: Safety analysis set excluding placebo participants and including participants with at least one serum post dose PK measurement.
    End point type
    Secondary
    End point timeframe
    Predose on Weeks 1, 2, 3, 17, 19, 21, 23, and 24
    Notes
    [11] - The end point is not reporting statistics for all the arms in the baseline period. It is expected all the baseline period arms will be reported on when providing values for an end point on the baseline period.
    Justification: Data collection was pre-specified for the Efgartigimod arm only.
    End point values
    		 Efgartigimod PH20 SC
    Number of subjects analysed
    135
    Units: μg/mL
    arithmetic mean (standard deviation)
        Week 1 (N = 135)
    13.2 ( 6.46 )
        Week 2 (N = 133)
    16.6 ( 8.17 )
        Week 3 (N = 126)
    17.0 ( 7.95 )
        Week 17 (N = 89)
    15.1 ( 8.54 )
        Week 19 (N = 91)
    15.4 ( 7.43 )
        Week 21 (N = 78)
    15.1 ( 8.86 )
        Week 23 (N = 88)
    14.9 ( 7.79 )
        Week 24 (N = 91)
    14.7 ( 8.10 )
    No statistical analyses for this end point

    Secondary: Percentage Change From Baseline in Total IgG in the Overall Population

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    End point title
    		 Percentage Change From Baseline in Total IgG in the Overall Population
    End point description
    Samples were collected predose, on the day of IMP administration. Pharmacodynamic (PD) Analysis Set: Safety analysis set including participants with at least one serum post dose PD measurement.
    End point type
    Secondary
    End point timeframe
    Baseline and Weeks 1, 2, 3, 17, 19, 21, 23, and 24
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    133
    67
    Units: percentage of total IgG
    arithmetic mean (standard deviation)
        Week 1 (N = 133, 67)
    -33.64 ( 26.018 )
    0.60 ( 14.065 )
        Week 2 (N = 132, 64)
    -50.68 ( 34.973 )
    10.31 ( 44.858 )
        Week 3 (N = 131, 64)
    -56.80 ( 39.133 )
    4.97 ( 28.484 )
        Week 17 (N = 96, 45)
    -64.76 ( 11.478 )
    1.27 ( 16.749 )
        Week 19 (N = 98, 51)
    -60.98 ( 26.460 )
    9.28 ( 44.989 )
        Week 21 (N = 89, 49)
    -62.38 ( 15.176 )
    4.62 ( 25.406 )
        Week 23 (N = 92, 49)
    -62.45 ( 20.286 )
    2.45 ( 21.271 )
        Week 24 (N = 102, 55)
    -61.97 ( 18.200 )
    -0.36 ( 17.408 )
    No statistical analyses for this end point

    Secondary: Number of Participants With Antiplatelet Antibodies in the Overall Population

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    End point title
    		 Number of Participants With Antiplatelet Antibodies in the Overall Population
    End point description
    The antiplatelet antibody was positive if optical density value >0.129. PD Analysis Set: Safety analysis set including participants with at least one serum post dose PD measurement and tested positive for antiplatelet antibodies at Baseline.
    End point type
    Secondary
    End point timeframe
    Weeks 7, 15, 23, and 24
    End point values
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Number of subjects analysed
    36
    16
    Units: participants
        Week 7 (N = 36, 14)
    20
    10
        Week 15 (N = 33, 16)
    18
    10
        Week 23 (N = 28, 14)
    17
    9
        Week 24 (N = 32, 13)
    19
    8
    No statistical analyses for this end point

    Adverse events

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    Adverse events information
    Timeframe for reporting adverse events
    Up to 35 weeks
    Adverse event reporting additional description
    The total number of participants affected by other (not including serious) adverse events (AEs) include participants who experienced other AEs under the frequency threshold of 5%. SAF: All participants who received at least 1 dose or part of a dose.
    Assessment type
    		 Systematic
    Dictionary used for adverse event reporting
    Dictionary name
    		 MedDRA
    Dictionary version
    26.0
    Reporting groups
    Reporting group title
    Efgartigimod PH20 SC
    Reporting group description
    		 Participants receiving efgartigimod PH20 SC treatment.

    Reporting group title
    Placebo PH20 SC
    Reporting group description
    		 Participants receiving placebo PH20 SC treatment.

    Serious adverse events
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Total subjects affected by serious adverse events
         subjects affected / exposed
    14 / 137 (10.22%)
    10 / 70 (14.29%)
         number of deaths (all causes)
    1
    0
         number of deaths resulting from adverse events
    1
    0
    Reproductive system and breast disorders
    Heavy menstrual bleeding
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Intermenstrual bleeding
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Respiratory, thoracic and mediastinal disorders
    Epistaxis
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Investigations
    Haemoglobin decreased
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Platelet count decreased
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Injury, poisoning and procedural complications
    Head injury
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Nervous system disorders
    Cerebral infarction
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 2
    0 / 0
         deaths causally related to treatment / all
    0 / 1
    0 / 0
    Headache
         subjects affected / exposed
    2 / 137 (1.46%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    1 / 2
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Blood and lymphatic system disorders
    Immune thrombocytopenia
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Thrombocytopenia
         subjects affected / exposed
    1 / 137 (0.73%)
    2 / 70 (2.86%)
         occurrences causally related to treatment / all
    0 / 3
    0 / 2
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Eye disorders
    Amaurosis fugax
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Vitreous haemorrhage
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Gastrointestinal disorders
    Abdominal distension
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Haematochezia
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Inguinal hernia strangulated
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Melaena
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Hepatobiliary disorders
    Cholecystitis acute
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 2
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Renal and urinary disorders
    Haematuria
         subjects affected / exposed
    0 / 137 (0.00%)
    2 / 70 (2.86%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 2
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Endocrine disorders
    Autoimmune thyroiditis
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Musculoskeletal and connective tissue disorders
    Osteonecrosis
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Infections and infestations
    Arthritis infective
         subjects affected / exposed
    0 / 137 (0.00%)
    1 / 70 (1.43%)
         occurrences causally related to treatment / all
    0 / 0
    0 / 1
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    COVID-19
         subjects affected / exposed
    3 / 137 (2.19%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 3
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    COVID-19 pneumonia
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Meningitis aseptic
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    1 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Urosepsis
         subjects affected / exposed
    1 / 137 (0.73%)
    0 / 70 (0.00%)
         occurrences causally related to treatment / all
    0 / 1
    0 / 0
         deaths causally related to treatment / all
    0 / 0
    0 / 0
    Frequency threshold for reporting non-serious adverse events: 5%
    Non-serious adverse events
    		 Efgartigimod PH20 SC Placebo PH20 SC
    Total subjects affected by non serious adverse events
         subjects affected / exposed
    130 / 137 (94.89%)
    65 / 70 (92.86%)
    Vascular disorders
    Haematoma
         subjects affected / exposed
    7 / 137 (5.11%)
    3 / 70 (4.29%)
         occurrences all number
    10
    3
    Hypertension
         subjects affected / exposed
    7 / 137 (5.11%)
    4 / 70 (5.71%)
         occurrences all number
    16
    5
    General disorders and administration site conditions
    Fatigue
         subjects affected / exposed
    8 / 137 (5.84%)
    0 / 70 (0.00%)
         occurrences all number
    9
    0
    Injection site bruising
         subjects affected / exposed
    13 / 137 (9.49%)
    2 / 70 (2.86%)
         occurrences all number
    23
    3
    Injection site erythema
         subjects affected / exposed
    9 / 137 (6.57%)
    2 / 70 (2.86%)
         occurrences all number
    31
    6
    Injection site haemorrhage
         subjects affected / exposed
    14 / 137 (10.22%)
    14 / 70 (20.00%)
         occurrences all number
    17
    26
    Injection site pain
         subjects affected / exposed
    8 / 137 (5.84%)
    2 / 70 (2.86%)
         occurrences all number
    43
    2
    Injection site rash
         subjects affected / exposed
    7 / 137 (5.11%)
    1 / 70 (1.43%)
         occurrences all number
    12
    1
    Injection site reaction
         subjects affected / exposed
    10 / 137 (7.30%)
    1 / 70 (1.43%)
         occurrences all number
    28
    1
    Vessel puncture site haemorrhage
         subjects affected / exposed
    3 / 137 (2.19%)
    5 / 70 (7.14%)
         occurrences all number
    3
    6
    Respiratory, thoracic and mediastinal disorders
    Epistaxis
         subjects affected / exposed
    20 / 137 (14.60%)
    15 / 70 (21.43%)
         occurrences all number
    50
    38
    Investigations
    Blood urine present
         subjects affected / exposed
    43 / 137 (31.39%)
    20 / 70 (28.57%)
         occurrences all number
    77
    34
    C-reactive protein increased
         subjects affected / exposed
    3 / 137 (2.19%)
    8 / 70 (11.43%)
         occurrences all number
    3
    12
    Injury, poisoning and procedural complications
    Contusion
         subjects affected / exposed
    22 / 137 (16.06%)
    12 / 70 (17.14%)
         occurrences all number
    102
    43
    Nervous system disorders
    Dizziness
         subjects affected / exposed
    8 / 137 (5.84%)
    3 / 70 (4.29%)
         occurrences all number
    10
    3
    Headache
         subjects affected / exposed
    16 / 137 (11.68%)
    7 / 70 (10.00%)
         occurrences all number
    23
    9
    Blood and lymphatic system disorders
    Anaemia
         subjects affected / exposed
    10 / 137 (7.30%)
    6 / 70 (8.57%)
         occurrences all number
    10
    13
    Gastrointestinal disorders
    Diarrhoea
         subjects affected / exposed
    7 / 137 (5.11%)
    1 / 70 (1.43%)
         occurrences all number
    8
    1
    Dyspepsia
         subjects affected / exposed
    3 / 137 (2.19%)
    5 / 70 (7.14%)
         occurrences all number
    4
    8
    Gingival bleeding
         subjects affected / exposed
    14 / 137 (10.22%)
    10 / 70 (14.29%)
         occurrences all number
    17
    25
    Mouth haemorrhage
         subjects affected / exposed
    19 / 137 (13.87%)
    6 / 70 (8.57%)
         occurrences all number
    37
    16
    Oral blood blister
         subjects affected / exposed
    10 / 137 (7.30%)
    1 / 70 (1.43%)
         occurrences all number
    19
    2
    Skin and subcutaneous tissue disorders
    Ecchymosis
         subjects affected / exposed
    34 / 137 (24.82%)
    20 / 70 (28.57%)
         occurrences all number
    88
    83
    Petechiae
         subjects affected / exposed
    34 / 137 (24.82%)
    19 / 70 (27.14%)
         occurrences all number
    77
    40
    Purpura
         subjects affected / exposed
    15 / 137 (10.95%)
    11 / 70 (15.71%)
         occurrences all number
    56
    38
    Renal and urinary disorders
    Haematuria
         subjects affected / exposed
    32 / 137 (23.36%)
    23 / 70 (32.86%)
         occurrences all number
    47
    43
    Musculoskeletal and connective tissue disorders
    Arthralgia
         subjects affected / exposed
    3 / 137 (2.19%)
    4 / 70 (5.71%)
         occurrences all number
    4
    4
    Infections and infestations
    COVID-19
         subjects affected / exposed
    18 / 137 (13.14%)
    6 / 70 (8.57%)
         occurrences all number
    18
    6
    Upper respiratory tract infection
         subjects affected / exposed
    12 / 137 (8.76%)
    6 / 70 (8.57%)
         occurrences all number
    15
    8
    Urinary tract infection
         subjects affected / exposed
    8 / 137 (5.84%)
    6 / 70 (8.57%)
         occurrences all number
    11
    10
    Metabolism and nutrition disorders
    Hyperuricaemia
         subjects affected / exposed
    7 / 137 (5.11%)
    3 / 70 (4.29%)
         occurrences all number
    9
    4

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    Substantial protocol amendments (globally)
    Were there any global substantial amendments to the protocol? Yes
    Date
    Amendment
    12 Jan 2021
    - IgG subtype levels were removed from the PD secondary endpoint. - Which participants should complete the EoT visit was updated. - The inclusion criteria were updated for the requirement of mean platelet count of <30 × 10^9/L to require at least 3 documented qualifying counts where at least 2 of the qualifying counts must be taken during the screening period. If the third count is not available from the 3 preceding months, this third platelet count could be obtained during the screening period. - The contraception requirements were updated due to final reproductive toxicity study results, which did not indicate a risk to male or female fertility or embryo-fetal developmental toxicity. - The primary endpoint analysis was updated per the United States Food and Drug Administration recommendations. A supportive analysis was also added. - Additional details on prior ITP procedures and therapies were specified per the United States Food and Drug Administration recommendations.
    16 Jul 2021
    - Caregiver-related requirements were clarified. - An eligibility evaluation requirement was added for participants rolling over to study ARGX-113-2005 who had an SAE during ARGX-113-2004. - A disease-specific measure of health-related QoL for use in adults with ITP was added. - The following parameters were added to be tested at baseline and visit 14 for safety purposes: apolipoprotein B, lipoprotein A, fibrinogen, von Willebrand factor, D-dimer, PCSK9. - The inclusion criteria were updated to make an exception for the age of consent in certain countries with higher legal age. - The exclusion criteria were updated to exclude participants with active clinically significant bleeding of an organ or internal mucosal bleeding, other than expected in ITP, that warrants emergent treatment or therapeutic procedure. - The exclusion criteria were updated to exclude participants with an estimated high risk of clinically significant bleeding of an organ or internal mucosal bleeding, other than expected in ITP, that warrants emergent treatment or therapeutic procedure. - Baseline platelet count category was added to the analysis model for consistency with the primary endpoint analysis approach (Cochran-Mantel- Haenszel test). - Added suspected transmission of any infectious agent as an SAE per EMA guidelines.
    15 Jul 2022
    - The sample size was changed to approximately 180 participants with chronic ITP. - The hierarchical order for testing the third and fourth key secondary efficacy endpoints was updated. - The statistical method was modified for analysis of the key secondary efficacy endpoint “incidence and severity of the WHO-classified bleeding events in the overall population". - Contraception requirements and the required time period for collecting pregnancy information were updated. - It was specified that the baseline visit in ARGX-113-2005 would occur 7 days after the ARGX-113-2004 end of trial (EoT) visit for ARGX-113-2004 participants who met the criteria to transition to an every-other-week IMP dosing regimen based on their platelet counts at the EoT visit. - The clinical chemistry parameters apolipoprotein B, lipoprotein A, fibrinogen, von Willebrand factor, D-dimer, and PCSK9 were removed. - Updated safety reporting processes to align with the sponsor’s current practices.
    17 Feb 2023
    - The exclusion criterion and washout period for serious thromboembolic events were updated. The prohibited period for any major thrombotic or embolic event (eg, myocardial infarction, stroke, deep venous thrombosis, pulmonary embolism) was revised from within 12 months to within 5 years before randomization. - Language was added to clarify that any participant developing a new or recurrent malignancy except basal cell carcinoma would discontinue study treatment regardless of the relationship to IMP. - The collection time of PK/PD/anti-drug antibody samples was revised from within 2 hours to within the same day before IMP administration. - The contraception requirement for male participants was removed. - An efficacy objective was added to compare efgartigimod PH20 SC to placebo PH20 SC in IWG response and initial response, measuring the proportions of participants with an IWG response, an IWG complete response, and an initial response. - Anti-CD20 therapy (eg, rituximab) with a washout of 6 months before randomization was added. - The age of consent inclusion criterion was revised to state that participants should be at least the local legal age of consent for clinical studies when signing the informed consent form. - The follow-up time after IMP administration was revised from 15 to 30 minutes. - Language was added describing blinding procedures for albumin and urine total protein (quantitative) values per DSMB recommendations.
    06 Apr 2023
    The substantiality assessment was revised from referring to Article 2 §2 (13) of Regulation No 536/2014 of the European Parliament and the Council of the European Union to Article 10(a) of Directive 2001/20/EC of the European Parliament and the Council of the European Union.

    Interruptions (globally)
    Were there any global interruptions to the trial? No

    Limitations and caveats
    Limitations of the trial such as small numbers of subjects analysed or technical problems leading to unreliable data.
    None reported
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