A Study Evaluating the Safety and Efficacy of Long-term Dosing of Romiplostim in Thrombocytopenic Pediatric Patients With Immune (Idiopathic) Thrombocytopenia Purpura

Study Overview
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Brief Summary
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This is an extension study designed to assess the safety and durability of platelet count increases with romiplostim treatment of thrombocytopenic patients with immune (Idiopathic) thrombocytopenia purpura. This study is available to pediatric patients who have completed a previous romiplostim ITP study and meet the eligibility criteria of this study.

Official Title
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An Open Label Study Evaluating the Safety and Efficacy of Long-term Dosing of Romiplostim in Thrombocytopenic Pediatric Subjects With Immune (Idiopathic) Thrombocytopenia Purpura (ITP)

Conditions
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Thrombocytopenia in Pediatric Subjects With Immune Idiopathic Thrombocytopenic Purpura ITP

Intervention / Treatment
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* Biological: Romiplostim


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subject or subject's legally acceptable representative has provided informed consent. Subject completed a romiplostim study for the treatment of thrombocytopenia in pediatric subjects with ITP. Exclusion Criteria: Subject has or previously had any bone marrow stem cell disorder (any abnormal bone marrow findings other than those typical of ITP must be approved by Amgen before a subject may be enrolled in the study). Subject has any new active malignancy diagnosed since enrollment in the previous romiplostim ITP study. Subject received any alkylating agents within four weeks before the screening visit or anticipated use during the time of the proposed study. Other investigational medications are excluded. Currently enrolled in another investigational device or drug study, or less than 30 days since ending another investigational device or drug study(s), or receiving other investigational agent(s) (with the exception of romiplostim in a previous clinical study). Female subject of child bearing potential (defined as having first menses) is not willing to use highly effective contraception during treatment and for 4 weeks after the end of treatment. Female subject is pregnant or breast feeding, or planning to become pregnant within 4 weeks after the end of treatment. Subject has known sensitivity to any of the products to be administered during dosing. Subject previously has entered this study (this will depend on the type of study). Subject will not be available for protocol required study visits, to the best of the subject and investigator's knowledge. Subject has any kind of disorder that, in the opinion of the investigator, may compromise the ability of the subject to give written informed consent and/or to comply with all required study procedures.

Ages Eligible for Study
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Minimum Age: 1 Year

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: Supportive Care
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Romiplostim<br>Participants received romiplostim administered by subcutaneous injection once a week. The starting dose of romiplostim was 1 μg/kg; weekly dose increases continued in increments of 1 μg/kg/week to a maximum dose of 10 μg/kg in an attempt to reach a target platelet count of between 50 x 10^9/L and 200 x 10^9/L. | Biological: Romiplostim<br>* Administered by subcutaneous injection once a week.<br>* Other names: Nplate;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Participants With Adverse Events | The adverse event (AE) severity grading scale used was the Common Terminology Criteria for Adverse Events (CTCAE) version 3.0 grading scale, where Grade 1 = Mild AE; Grade 2 = Moderate AE; Grade 3 = Severe AE; Grade 4 = Life-threatening or disabling AE; Grade 5 = Death related to AE. A serious adverse event was defined as an adverse event that met at least one of the following serious criteria: fatal life threatening (places the subject at immediate risk of death) required in-patient hospitalization or prolongation of existing hospitalization resulted in persistent or significant disability/incapacity congenital anomaly/birth defect other medically important serious event. The investigator assessed whether each adverse event was possibly related to the investigational product. | From first dose of study drug until 1 week after last dose. The median (minimum, maximum) duration of treatment was 135.0 weeks (5, 363 weeks). | 
| Duration Adjusted Rate of Treatment Emergent Adverse Events | Exposure adjusted rate was defined as the total number of events divided by the duration of time participants were under observation. The adverse event (AE) severity grading scale used was the Common Terminology Criteria for Adverse Events (CTCAE) version 3.0 grading scale, where Grade 1 = Mild AE; Grade 2 = Moderate AE; Grade 3 = Severe AE; Grade 4 = Life-threatening or disabling AE; Grade 5 = Death related to AE. A serious adverse event was defined as an adverse event that met at least one of the following serious criteria: fatal life threatening (places the subject at immediate risk of death) required in-patient hospitalization or prolongation of existing hospitalization resulted in persistent or significant disability/incapacity congenital anomaly/birth defect other medically important serious event. The investigator assessed whether each adverse event was possibly related to the study drug. | From first dose of study drug until 1 week after last dose. The median (minimum, maximum) duration of treatment was 135.0 weeks (5, 363 weeks). | 
| Number of Participants Who Developed Antibodies to Romiplostim | Two validated assays were used to test for antibodies to romiplostim / the thrombopoietin-mimetic peptide component of romiplostim (TMP). The first was an immunoassay to confirm the presence of antibodies. The second was a cell-based bioassay to detect neutralizing or inhibitory effects in vitro. If a sample was positive in both assays, a participant was defined as positive for neutralizing antibodies. Transient antibodies are those positive post-baseline but negative at the last time point tested. Persistent antibodies were those positive at the last time point tested. | Once a year until the end of treatment and 1 week after the end of treatment; median (minimim, maximum) time on study was 34 (2, 91) months. | 
| Number of Participants Who Developed Antibodies to Endogenous Thrombopoietin | Two validated assays were used to test for antibodies to endogenous thrombopoietin (TPO). The first was an immunoassay to confirm the presence of antibodies. The second was a cell-based bioassay to detect neutralizing or inhibitory effects in vitro. If a sample was positive in both assays, a participant was defined as positive for neutralizing antibodies. Transient antibodies are those positive post-baseline but negative at the last time point tested. Persistent antibodies were those positive at the last time point tested. | Once a year until the end of treatment and 1 week after the end of treatment; median (minimim, maximum) time on study was 34 (2, 91) months. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Participants With a Platelet Response | Platelet response was defined as at least one platelet count ≥ 50 x 10^9/L in the absence of rescue medication during the study. | Assessed every 4 weeks for the duration of treatment; the median (minimum, maximum) duration of treatment was 135.0 weeks (5, 363 weeks). | 
| Percentage of Participants Who Used Concomitant ITP Therapy |  | From baseline to the end of treatment; the median (minimum, maximum) duration of treatment was 135.0 weeks (5, 363 weeks). | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Immune thrombocytopenic Purpura, Pediatric, Thrombocytopenia