Clinical trial • Phase II/III • Immunology | Haematology

EFGARTIGIMOD ALFA for Chronic immune thrombocytopenia (ITP) | Idiopathic thrombocytopenic purpura

Phase II/III trial of EFGARTIGIMOD ALFA for Chronic immune thrombocytopenia (ITP) | Idiopathic thrombocytopenic purpura.

Overview

Trial Therapeutic Area
Immunology | Haematology
Trial Disease
Chronic immune thrombocytopenia (ITP) | Idiopathic thrombocytopenic purpura
Trial Stage
Phase II/III
Drug Modality
Peptide/protein/enzyme
Paediatric Trial
Yes
Orphan Drug
Yes

Key dates

Initial CTIS Submission Date
30-05-2025
First CTIS Authorization Date
24-09-2025

Trial design

Randomised, open-label, placebo for efgartigimod iv (placebo iv) vs argx-113 (efgartigimod alfa) iv 12 mg/kg; dosing schedule: once weekly or once every other week in the double-blinded treatment period (dbtp). in oltps participants receive efgartigimod iv 12 mg/kg once weekly or once every other week; participants who turn 18 may receive adult dose 10 mg/kg once weekly or once every other week.-controlled Phase II/III trial in Hungary, Romania, Poland and others.

Randomised
Yes
Open Label
Yes
Comparator
Placebo for efgartigimod IV (placebo IV) vs ARGX-113 (efgartigimod alfa) IV 12 mg/kg; dosing schedule: once weekly or once every other week in the double-blinded treatment period (DBTP). In OLTPs participants receive efgartigimod IV 12 mg/kg once weekly or once every other week; participants who turn 18 may receive adult dose 10 mg/kg once weekly or once every other week.
Target Sample Size
27

Eligibility

Recruits 27 paediatric patients.

Pregnancy Exclusion
7) Pregnant or lactating state or intention to become pregnant during the study
Vulnerable Population
The study enrols pediatric participants aged 12 to <18 years. Informed assent is required from participants according to local regulations, and a parent or guardian must sign the informed consent form (ICF). Participants who have reached the age of majority per local law may sign the ICF themselves. Age-specific assent and parent/guardian ICF documents are provided (assent forms for 11-14, 12-17, 15-17 age groups and parent/guardian ICFs) in multiple language versions as indicated in the submitted ICF/assent materials.

Inclusion criteria

  • {"criterion_text":"- 1A. Is aged 12 to <18 years when completing the informed consent process, defined as providing informed assent according to local regulations and having a parent or guardian sign the ICF. Participants who are at the age of majority, according to local regulations, may sign the ICF\n- 10) Has documented baseline mean platelet count of <30 × 109/L before randomization on study day 1\n- 11) Has 1 documented qualifying platelet count (ie, a platelet count used in the formula for calculating the arithmetic mean) on study day 1 before randomization\n- 12) Has at least 2 documented qualifying platelet counts between study day −14 and study day 1 before randomization\n- 13) Has at least 3 documented qualifying platelet counts in the 3 months before randomization on study day 1\n- 14) Has no documented platelet count of >35 × 109/L within 30 days before randomization on study day 1\n- 2A. Is capable of completing the informed consent process as described in Section 10.1.3, and can comply with protocol requirements\n- 3) If an FAOCBP (defined in Section 10.4.1.1), agrees to use contraceptive measures consistent with local regulations and study requirements defined in Section 10.4.2.1\n- 4) If an FAOCBP, has a negative serum pregnancy test at screening and a negative urine pregnancy test at baseline before receiving IMP (Section 10.4.2.1)\n- 5) Has a documented diagnosis of primary ITP, as defined by the IWG1,3: a platelet count of <100 × 109 /L in the absence of other causes or disorders that may be associated with thrombocytopenia\n- 6A. Has a documented duration of primary ITP of more than 12 months on the date the informed consent process is complete\n- 7) Has documented prior ITP treatment with at least 1 of the following: corticosteroids, IVIg, anti-D immunoglobulin (for participants who are nonsplenectomized and Rho[D]-positive), TPO-RAs, or rituximab\n- 8) Has documented prior response, defined as 1 platelet count of ≥50 × 109 /L to at least 1 of the following ITP treatments: prednisone, other or nonspecified corticosteroids, IVIg, or anti-D immunoglobulin (for participants who are nonsplenectomized and Rho[D]-positive)\n- 9) Has documented insufficient response to a prior ITP treatment with corticosteroids, IVIg,anti-D immunoglobulin (for participants who are nonsplenectomized and Rho[D]-positive), TPO-RAs, rituximab, or splenectomy, as defined by any of the following criteria: a. No platelet count of ≥50 × 109/L after treatment b. Platelet count of ≥50 × 109/L after treatment followed by platelet count <50 × 109/L c. Less than 2-fold increase in platelet count from the pretreatment count d. No platelet count of ≥30 × 109/L after splenectomy e. Platelet count of ≥30 × 109/L after splenectomy followed by platelet count <30 × 109/L f. Reduction in platelet count to <30 × 109/L if tapering corticosteroids g. Ongoing need for continuous prednisone (or corticosteroid equivalent) 5 mg/day to maintain a platelet count of ≥30 × 109 /L and/or to avoid bleeding h. Repeated corticosteroid administration for at least 2 months to maintain a platelet count of ≥30 × 109/L and/or to avoid bleeding"}

Exclusion criteria

  • {"criterion_text":"- 1) Besides the indication under study, known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of chronic ITP or puts the participant at undue risk\n- 10) Different IMP received in another clinical study <12 weeks or <5 half-lives (whichever is longer) before screening\n- 11) Anti-CD20 or anti-CD19 antibody received <6 months before screening\n- 12) IVIg, SCIg, or PLEX received <3 weeks before screening\n- 13) Live or live-attenuated vaccine received <4 weeks before treatment\n- 14) Prior ITP therapy not discontinued per the defined washout period (refer to Table 10)\n- 15) Secondary ITP according to the following definition by the IWG1: all forms of immune-mediated thrombocytopenia except primary ITP\n- 16) Documented prior arterial or venous thrombosis within 12 months before screening\n- 17) Concurrent ITP therapy, except as specified in this protocol (refer to Section 6.9.3)\n- 18) Nonimmune thrombocytopenia\n- 19) History of hereditary thrombocytopenia\n- 2) Serious or severe active infection that is not sufficiently resolved in the investigator’s opinion\n- 20) ITP-associated critical or severe bleeding (refer to Table 12)\n- 21) Positive serum test result at screening for active infection with any of the following: a. HBV indicative of an acute or chronic infection unless associated with a negative HBV DNA test result b. HCV based on HCV antibody assay unless a negative RNA test result is available (Section 10.2.1.2) c. HIV based on confirmed positive serology results (Section 10.2.1.3)\n- 22) At the screening visit, clinically significant laboratory abnormalities as follows: a. Hemoglobin concentration ≤9 g/dL b. Severe renal impairment with eGFR <30 mL/min/1.73 m2. eGFR will be calculated using the bedside Schwartz formula. c. Aspartate aminotransferase and alanine aminotransferase >3.0× the ULN d. Total serum bilirubin concentration >1.5× the ULN e. Total IgG level below the lower limit of normal\n- 23) History of malignancy unless considered cured by adequate treatment a. With no evidence of recurrence for ≥3 years before first IMP administration b. One of the following cancers: • Basal cell or squamous cell skin cancer • Carcinoma in situ of the cervix • Carcinoma in situ of the breast • Incidental histological findings of prostate cancer (TNM stage T1a or T1b)\n- 24) Modification of concurrent ITP therapy during the screening period\n- 25A. Occurrence of rescue ITP therapy during the screening period (from the date the informed consent process is complete to randomization)\n- 3A. Recent major surgery (within 3 months of screening) or intention to have major surgery during the study\n- 4) Current participation in another interventional clinical study\n- 5) Known hypersensitivity to IMP or 1 of its excipients\n- This criterion was removed in version 2.0\n- 7) Pregnant or lactating state or intention to become pregnant during the study\n- 8) Previous participation in an efgartigimod clinical study and at least 1 dose of IMP received\n- 9) Monoclonal antibody that is not an anti-CD20 or Fc-fusion protein received <4 weeks before screening"}

Endpoints

Primary endpoints

  • {"endpoint_text":"- 1) Efgartigimod serum concentrations as input for compartmental, model-driven analysis to determine age and size dependency of clearance and volume of distribution of efgartigimod IV in the DBTP","definition_or_measurement_approach":"Measurement of efgartigimod serum concentrations over time to provide input for compartmental, model-driven PK analysis assessing age and size dependency of clearance and volume of distribution during the double-blinded treatment period (DBTP)."}
  • {"endpoint_text":"- 2) Total IgG levels as input for PK/PD modeling analysis in the DBTP","definition_or_measurement_approach":"Measurement of total IgG levels in serum over time to serve as input for PK/PD modelling analysis during the DBTP."}

Secondary endpoints

  • {"endpoint_text":"- 1) Efgartigimod serum concentrations over time during the DBTP","definition_or_measurement_approach":"Serial serum concentration measurements during DBTP to characterize PK profile."}
  • {"endpoint_text":"- 2) Percent change from baseline in total IgG levels in serum over time during the DBTP","definition_or_measurement_approach":"Percent change from baseline measurements of total IgG in serum across DBTP visits."}
  • {"endpoint_text":"- 3) Incidence, severity, and relatedness of the IMP to AEs, SAEs, and AEs leading to IMP discontinuation","definition_or_measurement_approach":"Standard safety monitoring and AE/SAE reporting assessing causality and severity."}
  • {"endpoint_text":"- 4) Clinically significant changes in laboratory parameters, ECGs, and vital signs","definition_or_measurement_approach":"Monitoring of lab values, ECGs and vitals for clinically significant changes versus baseline."}
  • {"endpoint_text":"- 5) Sustained platelet count response, defined as achieving platelet counts of ≥50 × 109/L for at least 4 of the 6 study visits between study weeks 19 and 24 of the DBTP and in OLTP1 for participants receiving placebo in the DBTP","definition_or_measurement_approach":"Platelet count measurements at scheduled visits; responder defined as ≥50×10^9/L for ≥4 of 6 visits between weeks 19-24 (and in OLTP1 for former placebo participants)."}
  • {"endpoint_text":"- 6) Extent of disease control, defined as the number of cumulative weeks with a platelet count of ≥50 × 109/L during the DBTP and the first 24 weeks of OLTP1 for participants receiving placebo in the DBTP","definition_or_measurement_approach":"Count of weeks with platelet count ≥50×10^9/L during specified periods."}
  • {"endpoint_text":"- 7) Actual values and changes from baseline for platelet counts over time","definition_or_measurement_approach":"Serial absolute platelet count measurements and comparison to baseline values."}
  • {"endpoint_text":"- 8) Incidence and severity of bleeding, assessed by the Modified Buchanan and Adix Bleeding Score for pediatric ITP15","definition_or_measurement_approach":"Bleeding assessments using the Modified Buchanan and Adix Bleeding Score for pediatric ITP."}
  • {"endpoint_text":"- 9) Incidence and prevalence of ADA and NAb against efgartigimod in serum","definition_or_measurement_approach":"Immunogenicity testing for anti-drug antibodies (ADA) and neutralizing antibodies (NAb) in serum."}
  • {"endpoint_text":"- 10) Change from baseline in: − EQ-5D-5L − KIT Child Self-Report and KIT Parent Impact Report − pedsFACIT-F","definition_or_measurement_approach":"Patient- and parent-reported outcome instruments (EQ-5D-5L, KIT, pedsFACIT-F) administered per schedule; changes vs baseline calculated."}
  • {"endpoint_text":"- 11) Measurement of immature platelet fractions (IPF#and IPF%) in blood samples over time","definition_or_measurement_approach":"Laboratory measurement of immature platelet fraction number and percent in blood samples at scheduled timepoints."}

Recruitment

Planned Sample Size
27
Recruitment Window Months
50
Consent Approach
Informed consent is obtained from the parent or guardian and informed assent from pediatric participants aged 12 to <18 according to local regulations. Participants at the age of majority per local law may sign the ICF themselves. Age-specific assent and parent/guardian consent documents are provided (assent forms for 11-14, 12-17, 15-17 age groups; parent/guardian ICFs), with documentation available in multiple languages as submitted in the recruitment/ICF materials.

Methods

  • GP letters to primary care physicians (K2_GP Letter) — provider-targeted recruitment materials to inform referring clinicians.
  • Doctor-to-patient letters and doctor referral materials (K2_Doctor_to_Patient, K2_Doctor Letter) — clinician-mediated recruitment.
  • Flyers, posters, patient brochures and parent brochures (K2_Flyer, K2_Patient_Brochure, K2_Parent_Brochure) — patient-facing printed recruitment materials in participating countries/languages.
  • HCP cards / IE cards (K2_HCP_Card, K2_IE CARD) — materials for healthcare professionals to support referral.
  • ICF flipbooks and recruitment/ICF procedure documents (K1_Recruitment_and_IC_Procedure) — structured recruitment and informed consent procedures provided to sites.

Geography

Total Number Of Sites
27
Total Number Of Participants
19

Hungary

Earliest CTIS Part Ii Submission Date
22-07-2025
Latest Decision Or Authorization Date
29-09-2025
Processing Time Days
69
Number Of Sites
3
Number Of Participants
2

Sites

Site Name
Semmelweis University
Department Name
Gyerekklinika, Tűzoltó utcai telephely
Contact Person Name
Gabor Kovacs
Site Name
University Of Debrecen
Department Name
Klinikai Központ Gyermekgyógyászati Klinika Gyermekhematológiai-Onkológiai Részleg
Contact Person Name
Istvan Szegedi
Contact Person Email
iszegedi@med.unideb.hu
Site Name
Borsod-Abauj-Zemplen Varmegyei Koezponti Korhaz Es Egyetemi Oktatokorhaz
Department Name
Velkey László Gyermekegészségyügyi Központ, Gyermek Onko-haematológiai és Csontvelő Transzplantációs
Contact Person Name
Reka Simon
Contact Person Email
reka.simondr@gmail.com

Romania

Earliest CTIS Part Ii Submission Date
18-06-2025
Latest Decision Or Authorization Date
17-10-2025
Processing Time Days
121
Number Of Sites
1
Number Of Participants
1

Sites

Site Name
Institutul Clinic Fundeni
Department Name
Pediatrie 2
Contact Person Name
Anca Colita
Contact Person Email
secretariat@icfundeni.ro

Poland

Earliest CTIS Part Ii Submission Date
25-08-2025
Latest Decision Or Authorization Date
03-11-2025
Processing Time Days
70
Number Of Sites
5
Number Of Participants
3

Sites

Site Name
Samodzielny Publiczny Dzieciecy Szpital Kliniczny Im. Jozefa Polikarpa Brudzinskiego W Warszawie
Department Name
Klinika Onkologii, Hematologii Dziecięcej, Transplantologii Klinicznej i Pediatrii
Contact Person Name
Paweł Łaguna
Contact Person Email
plaguna@wum.edu.pl
Site Name
Uniwersytecki Szpital Dzieciecy W Lublinie
Department Name
Oddział Hematologii, Onkologii i Transplantologii Dziecięcej
Contact Person Name
Katarzyna Drabko
Contact Person Email
katarzyna.drabko@umlub.pl
Site Name
Samodzielny Publiczny Zaklad Opieki Zdrowotnej Centralny Szpital Kliniczny Uniwersytetu Medycznego W Lodzi
Department Name
Klinika Pediatrii, Onkologii i Hematologii
Contact Person Name
Wojciech Młynarski
Site Name
Uniwersytecki Szpital Dzieciecy W Krakowie
Department Name
Klinika Onkologii i Hematologii Dziecięcej
Contact Person Name
Kinga Kwiecińska
Contact Person Email
kinga.kwiecinska@uj.edu.pl
Site Name
Uniwersyteckie Centrum Kliniczne
Department Name
Klinika Pediatrii, Hematologii i Onkologii
Contact Person Name
Oskar Budziło
Contact Person Email
obudzilo@uck.gda.pl

Lithuania

Earliest CTIS Part Ii Submission Date
22-08-2025
Latest Decision Or Authorization Date
26-09-2025
Processing Time Days
35
Number Of Sites
2
Number Of Participants
2

Sites

Site Name
Lietuvos sveikatos mokslu universiteto ligonine Kauno klinikos
Department Name
The Center of Pediatric Oncology and Hematology
Contact Person Name
Giedre Rutkauskiene
Site Name
Vilniaus Universiteto Ligonine Santaros Klinikos Vsi
Department Name
Children’s hospital, center for Pediatric Oncology and Hematology
Contact Person Name
Sonata Saulyte Trakymiene

Spain

Earliest CTIS Part Ii Submission Date
04-08-2025
Latest Decision Or Authorization Date
21-10-2025
Processing Time Days
78
Number Of Sites
5
Number Of Participants
3

Sites

Site Name
Hospital Universitari Vall D Hebron
Department Name
Pediatric Oncology
Contact Person Name
Thais Murciano Carrillo
Contact Person Email
thais.murciano@vallhebron.cat
Site Name
Hospital Infantil Universitario Nino Jesus
Department Name
Pediatric Oncology
Contact Person Name
Julián Sevilla Navarro
Site Name
Hospital General Universitario Gregorio Maranon
Department Name
Pediatric Oncology
Contact Person Name
David Díaz Pérez
Contact Person Email
ddiazp@salud.madrid.org
Site Name
Hospital Sant Joan De Deu Barcelona
Department Name
Pediatric Oncology
Contact Person Name
Rubén Berrueco Moreno
Contact Person Email
ruben.berrueco@sjd.es
Site Name
Hospital Universitario 12 De Octubre
Department Name
Pediatric Oncology
Contact Person Name
Carmen Garrido Colino
Contact Person Email
cgarridoc@salud.madrid.org

Italy

Earliest CTIS Part Ii Submission Date
22-08-2025
Latest Decision Or Authorization Date
24-09-2025
Processing Time Days
33
Number Of Sites
6
Number Of Participants
3

Sites

Site Name
Ospedale Pediatrico Bambino Gesu
Department Name
Oncoematologia e terapia genica
Contact Person Name
Giuseppe Palumbo
Contact Person Email
Giuseppe.palumbo@opbg.net
Site Name
Fondazione IRCCS San Gerardo Dei Tintori
Department Name
Dipartimento di Ematologia-Oncologia Pediatrica
Contact Person Name
Marco Spinelli
Site Name
Azienda Ospedaliera Universitaria Citta Della Salute E Della Scienza Di Torino
Department Name
Dipartimento Patologia e Cura del Bambino
Contact Person Name
Franca Fagioli
Contact Person Email
Franca.fagioli@unito.it
Site Name
IRCCS Istituto Giannina Gaslini
Department Name
UOC Ematologia
Contact Person Name
Maurizio Miano
Contact Person Email
mauriziomiano@gaslini.org
Site Name
Azienda Ospedaliero Universitaria Di Modena
Department Name
Dipartimento Materno-Infantile – SC Pediratria ad indirizzo onco-ematologico
Contact Person Name
Giovanni Palazzi
Contact Person Email
palazzi.giovanni@aou.mo.it
Site Name
Azienda Ospedaliero-Universitaria Di Bologna IRCCS Istituto Di Ricerca E Di Cura A Carattere Scientifico
Department Name
Oncoematologia pediatrica
Contact Person Name
Elena Facchini
Contact Person Email
elena.facchini@aosp.bo.it

France

Earliest CTIS Part Ii Submission Date
10-09-2025
Latest Decision Or Authorization Date
29-09-2025
Processing Time Days
19
Number Of Sites
2
Number Of Participants
2

Sites

Site Name
Centre Hospitalier Universitaire De Lille
Department Name
Hématologie Pédiatrique
Contact Person Name
Brigitte NELKEN
Contact Person Email
Brigitte.NELKEN@chu-lille.fr
Site Name
Centre Hospitalier Universitaire De Bordeaux
Department Name
Pediatric Hemato-immunology
Contact Person Name
Nathalie ALADJIDI

Germany

Earliest CTIS Part Ii Submission Date
22-01-2026
Latest Decision Or Authorization Date
05-02-2026
Processing Time Days
14
Number Of Sites
3
Number Of Participants
3

Sites

Site Name
Universitaetsklinikum Heidelberg AöR
Department Name
Klinik für Pädiatrische Onkologie, Hämatologie, Immunologie und Pneumologie
Contact Person Name
Laura Tagliaferri
Site Name
Medical Center - University Of Freiburg
Department Name
Kinder- und Jugendklinik
Contact Person Name
Sarah Salou
Site Name
Universitaetsklinikum Koeln AöR
Department Name
Klinik und Poliklinik für Kinder- und Jugendmedizin Pädiatrische Onkologie und Hämatologie
Contact Person Name
Boris Decarolis
Contact Person Email
boris.decarolis@uk-koeln.de

Sponsor

Primary sponsor

Full Name
Argenx
Organisation Type
Pharmaceutical company
Country Of Registered Address
Belgium

Contract research organisations

Name
Icon Clinical Research Limited
Responsibilities
1, 12, 2, 5, 6
Name
Iqvia Biotech LLC
Responsibilities
15 (Safety Vendor)
Name
Iqvia Biotech Limited
Responsibilities
15 (Safety Vendor)
Name
Suvoda LLC
Responsibilities
3
Name
PPD Labs
Responsibilities
4, 7

Third parties

  • {"country":"United States","full_name":"Eresearchtechnology Inc.","duties_or_roles":"eCOA","organisation_type":"Pharmaceutical company"}
  • {"country":"United States","full_name":"Greenphire LLC","duties_or_roles":"Travel and Reimbursement Logistics","organisation_type":"Non-Pharmaceutical company"}
  • {"country":"United States","full_name":"Suvoda LLC","duties_or_roles":"3","organisation_type":"Non-Pharmaceutical company"}
  • {"country":"Belgium","full_name":"PPD Labs","duties_or_roles":"4, 7","organisation_type":"Health care"}
  • {"country":"Ireland","full_name":"Icon Clinical Research Limited","duties_or_roles":"1, 12, 2, 5, 6","organisation_type":"Pharmaceutical company"}
  • {"country":"United Kingdom","full_name":"Resolian Bioanalytics","duties_or_roles":"4","organisation_type":"Industry"}
  • {"country":"Switzerland","full_name":"Fisher Clinical Services GmbH","duties_or_roles":"14","organisation_type":"Pharmaceutical company"}
  • {"country":"United States","full_name":"Iqvia Biotech LLC","duties_or_roles":"15 (Safety Vendor)","organisation_type":"Pharmaceutical company"}
  • {"country":"United Kingdom","full_name":"Iqvia Biotech Limited","duties_or_roles":"15 (Safety Vendor)","organisation_type":"Pharmaceutical company"}
  • {"country":"Belgium","full_name":"SGS Belgium","duties_or_roles":"11, 13, 15 (IDMC)","organisation_type":"Pharmaceutical company"}

Investigational products

Investigational Product Name
ARGX-113
Active Substance
EFGARTIGIMOD ALFA
Modality
Peptide/protein/enzyme
Routes Of Administration
IV infusion
Route
IV infusion
Authorisation Status
PRD3337712 (prodAuthStatus: 1)
Orphan Designation
Yes
Starting Dose
12 mg/kg
Dose Levels
12 mg/kg (once weekly or once every other week as per DBTP/OLTP schedule)
Frequency
Once weekly or once every other week
Maximum Dose
Max daily 12 mg/kg; max total amount 1200 mg (as provided)
Investigational Product Name
Placebo for efgartigimod
Modality
Other
Frequency
Administered IV once weekly or once every other week (placebo arm mirrors ARGX-113 schedule)

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