A Phase 3 Study to Evaluate the Safety and Efficacy of Efgartigimod PH20 Subcutaneous in Adult Patients With Primary Immune Thrombocytopenia

Study Overview
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Brief Summary
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A Phase 3 study to evaluate the safety and efficacy of efgartigimod PH20 subcutaneous in adult patients with primary immune thrombocytopenia

Official Title
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A Phase 3, Multicenter, Open-Label, Long-Term Trial to Evaluate the Safety and Efficacy of Efgartigimod (ARGX-113) PH20 Subcutaneous in Adult Patients With Primary Immune Thrombocytopenia

Conditions
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Primary Immune Thrombocytopenia

Intervention / Treatment
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* Biological: efgartigimod PH20 SC


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Ability to understand the requirements of the trial and provide written informed consent (including consent for the use and disclosure of research-related health information), willing and able to comply with the trial protocol procedures (including attending the required trial visits). Participants enrolled in the ARGX-113-2004 trial who completed the 24-week trial period. Note: If a participant has had an SAE during the ARGX-113-2004 trial, their eligibility should be evaluated by the investigator and the sponsor's trial physician. The decision of enrolling the participant will be evaluated case by case. 3a. Agree to use contraceptives consistent with local regulations and the following: • Female participants of childbearing potential must have a negative urine pregnancy test at baseline before receiving IMP. In addition to the above criteria, for participants who want to continue receiving efgartigimod during an additional 52-week treatment period (only applicable in case efgartigimod is not yet commercially available for patients with primary ITP or available through another patient program for patients with primary ITP), the following criteria apply: 4. Ability to understand the requirements of the additional 52-week treatment period of the trial, to provide written informed consent (including consent for the use and disclosure of research-related health information), and to comply with the trial protocol procedures (including required trial visits). 5. Participant has completed a 52-week treatment period. Exclusion criteria: Introduction or continuation of nonpermitted medications during the ARGX-113-2004 trial (such as anti-CD20 therapy, romiplostim, monoclonal antibodies, Fc fusion proteins, or live/live-attenuated vaccines) Use of any other investigational drug or participation in any other investigational trial Known hypersensitivity reaction to efgartigimod PH20 SC or any of its excipients Pregnant or lactating females and those who intend to become pregnant during the trial or within 90 days after last dose of efgartigimod PH20 SC

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: efgartigimod PH20 SC<br>Patients receiving efgartigimod PH20 SC treatment | Biological: efgartigimod PH20 SC<br>* Subcutaneous injection with efgartigimod PH20 SC<br>* Other names: ARGX-113 PH20 SC;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence, frequency, and severity of adverse events (AEs), AEs of special interest (AESIs), and serious AEs (SAEs) |  | 216 weeks | 
| Vital sign measurement: blood pressure in the overall population |  | 216 weeks | 
| ECG: PR, QT and QRS interval in the overall population |  | 216 weeks | 
| Laboratory safety evaluations: CRP analysis in the overall population |  | 216 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Extent of disease control defined as the percentage of weeks in the trial with platelet counts of ≥50×10E9/L |  | 52 weeks | 
| Proportion of patients with overall platelet count response defined as achieving a platelet count of ≥50×10E9/L on at least 4 occasions at any time during the 52-week treatment period |  | 52 weeks | 
| Mean change from baseline in platelet count at each visit |  | 52 weeks | 
| For patients rolling over from the ARGX-113-2004 trial with a platelet count of <30×10E9/L: time to response defined as the time to achieve 2 consecutive platelet counts of ≥50×10E9/L |  | 52 weeks | 
| The percentage of weeks in the trial with platelet counts of ≥30×10E9/L and ≥20×10E9/L above baseline |  | 52 weeks | 
| In patients with a baseline platelet count of <15×10E9/L in the current trial (ARGX-113-2005), the percentage of weeks in the trial with platelet counts of ≥30×10E9/L and ≥20×10E9/L above baseline |  | 52 weeks | 
| In patients with the first exposure to efgartigimod PH20 SC, the proportion of patients who achieve a sustained platelet response defined as achieving platelet counts of ≥50×10E9/L for at least 4 of the 6 visits between week 19 and week 24 |  | 5 weeks (week 19-24) | 
| In patients with the first exposure to efgartigimod PH20 SC, the proportion of patients achieving platelet counts of ≥50×10E9/L for at least 6 of the 8 visits between week 17 and week 24 |  | 7 weeks (week 17-24) | 
| Proportion of patients for whom dose and/or frequency of concurrent ITP therapies have been reduced compared to baseline |  | 52 weeks | 
| Rate of receipt of rescue therapy (rescue per patient per month) |  | 52 weeks | 
| Incidence of the World Health Organization (WHO)-classified bleeding events |  | 52 weeks | 
| Severity of the World Health Organization (WHO)-classified bleeding events |  | 52 weeks | 
| Serum efgartigimod concentration observed predose (Ctrough) |  | 52 weeks | 
| Change from baseline in PRO (Functional Assessment of Chronic Illness Therapy Fatigue Scale [FACIT-fatigue]) at planned visits |  | 52 weeks | 
| Change from baseline in PRO (Functional Assessment of Cancer Therapy questionnaire-Th6 [FACT-Th6]) at planned visits |  | 52 weeks | 
| Change from baseline in PRO (QoL (Short Form-36 [SF-36]) at planned visits |  | 52 weeks | 
| Pharmacodynamics markers: total IgG |  | 52 weeks | 
| Number of patients who performed self-administration at home over time |  | 52 weeks | 
| Percentage of patients who performed self-administration at home over time |  | 52 weeks | 
| Number of caregivers who administered the injection to the patient at home over time |  | 52 weeks | 
| Percentage of caregivers who administered the injection to the patient at home over time |  | 52 weeks | 
| Number of training visits needed for the participant or caregiver to be competent to start administering efgartigimod PH20 SC |  | 52 weeks | 
| Number of self- or caregiver-supported administrations at home |  | 52 weeks | 
| Percentage of self- or caregiver-supported administrations at home |  | 52 weeks | 
| Incidence and prevalence of antibodies to efgartigimod |  | 216 weeks | 
| Titers of antibodies to efgartigimod |  | 216 weeks | 
| Presence of neutralizing antibodies (NAb) against efgartigimod |  | 216 weeks |