A study to assess the effect and safety of efgartigimod IV in participants from 12 years to less than 18 years of age with chronic Immune Thrombocytopenia (ITP)

Overview

Sponsor-declared trial summary

Key facts

Sponsor

Argenx

Participant type

Pediatric, Patients

Age range

0-17 years

Gender

Male and Female

Therapeutic area

Diseases [C] - Immune System Diseases [C20]

Trial duration

7 Oct 2025 → ongoing

Decision date (initial)

2025-09-29

Transition trial

No

Low-intervention

No

Rare-disease indication

No

Vulnerable population

No

Trial design

CTIS Part I — objectives, methods, condition coding

Main objective

Scope: Pharmacodynamic, Efficacy, Safety, Pharmacokinetic, Others

To confirm an appropriate dose of efgartigimod IV in participants with chronic ITP in the DBTP

Secondary objectives 6

1. 1) To evaluate the PK and PD effects of efgartigimod IV in participants with chronic ITP in the DBTP
2. 2) To assess the safety and tolerability of efgartigimod IV compared with placebo and the long-term safety and tolerability of efgartigimod IV in participants with chronic ITP in the DBTP and the OLTPs
3. 3) To assess the efficacy of efgartigimod IV compared with placebo IV and the longterm efficacy of efgartigimod IV in participants with chronic ITP in the DBTP and OLTP1
4. 4) To assess the immunogenicity of efgartigimod IV in participants with chronic ITP in the DBTP and OLTP1
5. 5) To assess the effects of efgartigimod IV compared with placebo IV and the longterm effects of efgartigimod IV on COAs in participants with chronic ITP in the DBTP and OLTP1
6. 6) To explore the effects of efgartigimod IV on ITP pathophysiology

Conditions and MedDRA coding

Chronic Idiopathic thrombocytopenic purpura

Study design 1 period

Regulatory references

EMA paediatric investigation plan (PIP)

EMEA-002597-PIP04-21

Plan to share IPD

No

Eligibility criteria

Principal inclusion / exclusion criteria as submitted by sponsor

Inclusion criteria 14

1. 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
2. 2A. Is capable of completing the informed consent process as described in Section 10.1.3, and can comply with protocol requirements
3. 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
4. 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)
5. 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
6. 6A. Has a documented duration of primary ITP of more than 12 months on the date the informed consent process is complete
7. 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
8. 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)
9. 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
10. 10) Has documented baseline mean platelet count of <30 × 109/L before randomization on study day 1
11. 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
12. 12) Has at least 2 documented qualifying platelet counts between study day −14 and study day 1 before randomization
13. 13) Has at least 3 documented qualifying platelet counts in the 3 months before randomization on study day 1
14. 14) Has no documented platelet count of >35 × 109/L within 30 days before randomization on study day 1

Exclusion criteria 25

1. 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
2. 2) Serious or severe active infection that is not sufficiently resolved in the investigator’s opinion
3. 3A. Recent major surgery (within 3 months of screening) or intention to have major surgery during the study
4. 4) Current participation in another interventional clinical study
5. 5) Known hypersensitivity to IMP or 1 of its excipients
6. This criterion was removed in version 2.0
7. 7) Pregnant or lactating state or intention to become pregnant during the study
8. 8) Previous participation in an efgartigimod clinical study and at least 1 dose of IMP received
9. 9) Monoclonal antibody that is not an anti-CD20 or Fc-fusion protein received <4 weeks before screening
10. 10) Different IMP received in another clinical study <12 weeks or <5 half-lives (whichever is longer) before screening
11. 11) Anti-CD20 or anti-CD19 antibody received <6 months before screening
12. 12) IVIg, SCIg, or PLEX received <3 weeks before screening
13. 13) Live or live-attenuated vaccine received <4 weeks before treatment
14. 14) Prior ITP therapy not discontinued per the defined washout period (refer to Table 10)
15. 15) Secondary ITP according to the following definition by the IWG1: all forms of immune-mediated thrombocytopenia except primary ITP
16. 16) Documented prior arterial or venous thrombosis within 12 months before screening
17. 17) Concurrent ITP therapy, except as specified in this protocol (refer to Section 6.9.3)
18. 18) Nonimmune thrombocytopenia
19. 19) History of hereditary thrombocytopenia
20. 20) ITP-associated critical or severe bleeding (refer to Table 12)
21. 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)
22. 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
23. 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)
24. 24) Modification of concurrent ITP therapy during the screening period
25. 25A. Occurrence of rescue ITP therapy during the screening period (from the date the informed consent process is complete to randomization)

Endpoints

Primary and secondary outcome measures (English text)

Primary endpoints 2

1. 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
2. 2) Total IgG levels as input for PK/PD modeling analysis in the DBTP

Secondary endpoints 11

1. 1) Efgartigimod serum concentrations over time during the DBTP
2. 2) Percent change from baseline in total IgG levels in serum over time during the DBTP
3. 3) Incidence, severity, and relatedness of the IMP to AEs, SAEs, and AEs leading to IMP discontinuation
4. 4) Clinically significant changes in laboratory parameters, ECGs, and vital signs
5. 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
6. 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
7. 7) Actual values and changes from baseline for platelet counts over time
8. 8) Incidence and severity of bleeding, assessed by the Modified Buchanan and Adix Bleeding Score for pediatric ITP15
9. 9) Incidence and prevalence of ADA and NAb against efgartigimod in serum
10. 10) Change from baseline in: − EQ-5D-5L − KIT Child Self-Report and KIT Parent Impact Report − pedsFACIT-F
11. 11) Measurement of immature platelet fractions (IPF#and IPF%) in blood samples over time

Investigational products

Investigational medicinal products (IMPs), comparators, placebo, auxiliary

Test 1

Placebo 1

Sponsors and contacts

Sponsor organisations, regulatory contacts, third parties

Argenx

Sponsor organisation

Argenx

Address

Industriepark-Zwijnaarde 7

City

Gent

Postcode

9052

Country

Belgium

Scientific contact point

Organisation

Argenx

Contact name

Sabina Coppieters

Public contact point

Organisation

Argenx

Contact name

Vice President Clinical Development

Third parties 10

Locations

8 EU/EEA countries · 29 investigational sites

By country

Investigational sites

Country notifications

Trial-start, recruitment-start, end and early-termination notifications submitted per Member State

Results and documents

Annex IV summary of results, Annex V layperson summary, and all documents registered in CTIS for this trial

Documents 166 files

Public protocol annexes, IB summaries, regulatory submissions and post-authorisation documents registered in CTIS.

Application history

17 submissions — initial application plus substantial / non-substantial modifications