A Continuation Study of Mezagitamab in Adults With Chronic Primary Immune Thrombocytopenia

Phase 3

Not yet recruiting

• Conditions: Immune Thrombocytopenic Purpura (ITP)
• Interventions: Drug: Mezagitamab

• Registration Number: NCT06948318
• Lead Sponsor: Takeda

Brief Summary

Primary immune thrombocytopenia (ITP) is a condition where the immune system mistakenly destroys platelets, which are cells that help stop bleeding. This leads to a lower number of platelets, making it easier to bruise or bleed. The main aim of this study is to check how safe mezagitamab is and how well it is tolerated by adults with chronic primary ITP, if given over a longer time. Other aims are to learn how effective treatment with mezagitamab is and how the body processes it (called pharmacokinetics or PK) over a longer time.

Participants of the following previous mezagitamab studies will be invited to join this continuation study: TAK-079-3002 and TAK-079-1004. In this continuation study, participants will receive mezagitamab when certain protocol criteria are met.

During the study, participants will visit their study clinic several times.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2025-04-25
• Study First Submitted QC: 2025-04-28
• Study First Posted: 2025-04-29
• Status Verified: 2025-05
• Last Update Submitted: 2025-05-02
• Last Update Posted: 2025-05-06
• Study Start: 2025-08-29
• Primary Completion: 2029-07-29
• Study Completion: 2029-07-29

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 150

Inclusion Criteria

1. The participant has completed TAK-079-3002 (end of trial [EOT]) or TAK-079-1004 (EOT).

• Key Exclusion criteria:

For TAK-079-3002 participants:

1. The participant has a history of severe allergic or anaphylactic reactions to recombinant proteins or excipients used in the mezagitamab formulation.

For TAK-079-1004 participants:

1. The participant has had any thrombotic or embolic event within 12 months before signing the ICF.

2. The participant has had a splenectomy within 3 months before signing the ICF.

3. The participant has active infection with hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV).

4. History of malignancy (including myelodysplastic syndrome) within 5 years of signing the ICF, except for treated non-melanoma skin cancer or cervical carcinoma in situ.

5. In the opinion of the investigator, the participant has a serious medical or psychiatric illness that could potentially interfere with the completion of treatment according to this protocol.

6. The participant has received anti-cluster of differentiation (CD) 20 treatment within 12 months before screening and either of the following applies:

   1. The last dose was received within 6 months before screening.
   2. The last dose was received between 6 and 12 months before screening and the participant has a CD19+ count below the lower limit of normal.

7. The participant has received any monoclonal or polyclonal antibody for immunomodulation within 6 months before Visit 1.

8. The participant has been exposed to another investigational agent within 4 weeks or 5 half-lives, whichever is longer, before Visit 1.

9. The participant has used anticoagulants (for example, vitamin K antagonists, direct oral anticoagulants) within 3 weeks prior to Visit 1.

10 The participant has received a live or live-attenuated vaccine within 4 weeks prior to the first dose of trial treatment or has any live or live-attenuated vaccine planned during the trial.

11. The participant has used the following immunosuppressive agents as specified prior to Visit 1: alkylating agents (for example, cyclophosphamide) within 8 weeks, vinca alkaloids (for example, vincristine) within 4 weeks, sulfones (for example, dapsone) within 3 weeks, antiproliferative agents: (for example, mycophenolate mofetil and azathioprine) within 2 weeks, and calcineurin inhibitors: (for example, cyclosporine) within 2 weeks.

12. The participant has a history of severe allergic or anaphylactic reactions to recombinant proteins or excipients used in the mezagitamab formulation.

Other protocol defined inclusion/exclusion criteria may apply.

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Mezagitamab	Mezagitamab	Eligible participants who completed the TAK-079-3002 or TAK-079-1004 studies can receive on-demand treatment in this continuation study. The on-demand treatment course may be repeated as needed based on the pre-specified on-demand dosing criteria and investigator's clinical judgement.

Primary Outcome Measures

Name	Time	Method
Number of Participants With Treatment-Emergent Adverse Events (TEAEs) and Serious TEAEs	Up to approximately 108 weeks	An adverse event (AE) is any untoward medical occurrence in a clinical trial participant, temporally associated with the use of the trial intervention, whether or not the occurrence is considered related to the trial intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of the trial intervention. TEAEs are defined as AEs with start dates at the time of or following the first exposure to mezagitamab in the parent trial for Cohort 1 and in this trial for Cohort 2. A serious TEAE is a TEAE that meets 1 or more of the criteria: results in death, is life threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect or was otherwise considered medically important.
Number of Participants With TEAEs Leading to Permanent Withdrawal of Mezagitamab	Up to approximately 108 weeks	An AE is any untoward medical occurrence in a clinical trial participant, temporally associated with the use of the trial intervention, whether or not the occurrence is considered related to the trial intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of the trial intervention. TEAEs are defined as AEs with start dates at the time of or following the first exposure to mezagitamab in the parent trial for Cohort 1 and in this trial for Cohort 2.

Secondary Outcome Measures

Name	Time	Method
Number of Participants Requiring Rescue Therapy	Up to approximately 108 weeks
Serum Concentrations of Mezagitamab	Pre-dose and at multiple time points post-dose up to Week 104
Number of Participants With Anti-Drug Antibodies (ADA)	Pre-dose and at multiple time points post-dose up to Week 104
Number of Participants With Neutralizing Antibody (NAb)	Pre-dose and at multiple time points post-dose up to Week 104
Duration of Platelet Response	Up to approximately 108 weeks	The duration of platelet response will be measured by the cumulative number of weeks on which platelet count was ≥30,000/microliters (μL) and ≥50,000/μL throughout the trial.
Duration Between On-Demand Treatment Courses	Up to approximately 108 weeks
Time to Initiation of the First On-Demand Treatment Course	Up to approximately 108 weeks
Number of Participants With Complete Response	Up to approximately 108 weeks	Complete response is defined as achieving platelet counts ≥100,000/μL on at least 2 visits.
Number of Participants With Immune Thrombocytopenia (ITP) Remission	Up to approximately 108 weeks	ITP Remission is defined as all platelet counts ≥50,000/μL for at least 24 weeks after any mezagitamab treatment cycle in the absence of further therapy for ITP.
Number of Participants With Reduction in Dose and/or Frequency of Concomitant ITP Medications	Up to approximately 108 weeks	Concomitant ITP medications are defined as those given in addition to the trial intervention to treat your ITP. These medications include corticosteroids, thrombopoietin receptor agonists (TPO-RA), or fostamatinib.