Long-term Safety and Efficacy Evaluation of Mezagitamab in Adults with Chronic Primary Immune Thrombocytopenia: A Phase 3 Open-label Multicenter Continuation Trial

The primary objective is to evaluate the long-term safety and tolerability of mezagitamab in adults with chronic primary immune thrombocytopenia. The secondary objectives include:

• Assessment of long-term efficacy.
• Evaluation of the reduction in concomitant medications.
• Assessment of rescue therapy utilization.
• Collection of pharmacokinetic concentrations of mezagitamab.
• Characterization of immunogenicity.

This clinical trial involves 53 participants diagnosed with chronic primary immune thrombocytopenia. The study population includes both male and female patients aged 18 years or older. Selection is limited to individuals who have completed previous clinical studies, specifically TAK-079-3002 or TAK-079-1004. For those transitioning from the TAK-079-1004 study, a documented platelet response to mezagitamab during the main study or open-label extension is required. The sponsor did not provide information regarding lifestyle considerations or general health status beyond the specified diagnosis.

This Phase 3, open-label, multicenter continuation trial is designed to evaluate the long-term safety and efficacy of mezagitamab administered via subcutaneous injection in adults diagnosed with chronic primary immune thrombocytopenia. The study involves participants who have completed previous clinical trials, specifically TAK-079-3002 or TAK-079-1004, with those from the latter trial having demonstrated a specific platelet response. The primary objectives are to monitor the occurrence of treatment-emergent adverse events (TEAEs), serious TEAEs, and any TEAEs resulting in the permanent withdrawal of the study drug. Secondary endpoints include the duration of response, time to initiation of on-demand treatment, occurrence of remission, reduction in concomitant medications, and the evaluation of pharmacokinetics and the development of immunogenicity, such as anti-drug antibodies. The trial is expected to continue through July 2029.

The experimental treatment consists of mezagitamab, provided as a solution for injection. This investigational medicinal product is administered via subcutaneous injection.

Efficacy will be evaluated through several secondary endpoints in adults with chronic primary immune thrombocytopenia. Parameters include the duration of platelet response, the time interval between on-demand treatment courses, and the time to initiation of the first on-demand treatment course. The assessment also involves monitoring the occurrence of complete response and ITP remission.

Additional efficacy measures include the reduction in dose or frequency of concomitant medications, the use of rescue therapy, and the evaluation of pharmacokinetic concentrations at selected timepoints. The occurrence of anti-drug antibodies and neutralizing antibodies will also be assessed.