Takeda Reveals Promising Phase 2b Data on Mezagitamab for Primary Immune Thrombocytopenia

June 22, 2024 - Takeda (TSE:4502/NYSE:TAK) has reported promising outcomes from a Phase 2b randomized, double-blind, placebo-controlled study evaluating the safety, tolerability, and efficacy of mezagitamab (TAK-079) in patients with persistent or chronic primary immune thrombocytopenia (ITP). ITP is a rare autoimmune disorder marked by the accelerated destruction of platelets in the bloodstream, leading to a reduced platelet count and increased risk of debilitating bleeding.

These findings were shared at the oral Late-Breakthrough Session during the 32nd Congress of the International Society on Thrombosis and Haemostasis (ISTH) in Bangkok, Thailand. Takeda is planning a global Phase 3 trial of mezagitamab for ITP patients in the latter half of FY2024.

The TAK-079-1004 trial (NCT04278924) assessed three doses of subcutaneous mezagitamab (100mg, 300mg, and 600mg) compared to a placebo, administered once weekly for eight weeks to patients with chronic or persistent primary ITP, followed by over eight weeks of safety monitoring. The study’s primary endpoint focused on the percentage of patients experiencing Grade 3 or higher treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), and adverse events (AEs) leading to mezagitamab discontinuation. Secondary endpoints looked at various platelet response metrics.

Results from the Phase 2b trial indicated that mezagitamab treatment led to improved platelet responses across all tested dose levels compared to the placebo. Patients receiving mezagitamab demonstrated rapid and sustained platelet count increases, surpassing the therapeutic threshold of 50,000/µL, which lasted up to eight weeks after the final dose and continued through Week 16, highlighting mezagitamab's long-lasting effects on platelet response.

David Kuter, M.D., D.Phil., a leading expert in ITP and presenter of the study at ISTH, noted, “Despite available treatments, there remains a significant disease burden and need for more tolerable, disease-modifying treatments for those living with ITP. The Phase 2b results are encouraging, showing mezagitamab’s favorable efficacy and safety profile, which paves the way for further clinical evidence of this anti-CD38 monoclonal antibody’s potential efficacy in ITP.”

Mezagitamab displayed a favorable safety profile, consistent with previous studies, with no new safety signals. The rates of TEAEs leading to discontinuation, Grade 3 or higher TEAEs, and SAEs for the combined mezagitamab dose groups compared to placebo were 14.3% vs. 0%, 17.9% vs. 23.1%, and 14.3% vs. 7.7%, respectively.

Obi Umeh, M.D., M.Sc., Vice President, Franchise Global Program Leader at Takeda, expressed pride in the Phase 2b results being selected for presentation at the ISTH Congress. He confirmed plans for a Phase 3 study of mezagitamab in ITP for the second half of FY2024, reinforcing Takeda’s commitment to developing transformative treatments for high unmet patient needs.

Mezagitamab is a fully human IgG1 monoclonal antibody with a high affinity for CD38-expressing cells, including plasmablasts, plasma cells, and natural killer cells, leading to their depletion. It is designed to deliver rapid and sustained improvements in platelet response, aiming to restore platelet counts to functional levels. The U.S. Food and Drug Administration has granted mezagitamab Orphan Drug Designation and Fast Track Designation for chronic/persistent ITP treatment. It remains an investigational compound not yet approved by any regulatory authority.

The Phase 2b trial conducted a pre-specified interim analysis, evaluating safety, tolerability, and efficacy in patients with persistent or chronic primary ITP. Twenty-five participants were randomized to receive either 100mg or 300mg of mezagitamab or a placebo in Part A, while 16 participants received either 600mg of mezagitamab or a placebo in Part B. The study's primary endpoint was the percentage of patients with TEAEs, including Grade 3 or higher events, SAEs, and AEs leading to mezagitamab discontinuation. Secondary efficacy endpoints required specific platelet count increases without needing rescue treatment in the prior four weeks.

ITP is characterized by the accelerated destruction of platelets due to autoantibodies, leading to decreased platelet counts and increased bleeding risks. Approximately 20 percent of ITP patients do not achieve a platelet count above 50,000/µL with current treatments, highlighting the need for more effective and tolerable therapies.

Takeda remains committed to transforming patient care through innovative treatments in various therapeutic areas, including rare diseases, oncology, and plasma-derived therapies. The company’s extensive research and development efforts aim to address significant unmet needs and improve patient outcomes globally.

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