Mezagitimab appears safe and potentially effective for persistent immune thrombocytopenia

1. In this phase 2 randomized controlled trial, weekly subcutaneous mezagitimab was well-tolerated and associated with symptomatic improvement among patients with chronic primary immune thrombocytopenia.

2. Mezagitimab was also associated with greater platelet response than placebo. 

Evidence Rating Level: 1 (Excellent)

Study Rundown: Immune thrombocytopenia (ITP) is an autoantibody-mediated disease leading to low platelet counts and increased risk of bleeding. Current pharmacotherapies are not effective for up to twenty percent of patients with ITP. Mezagitimab is a monoclonal antibody targeting CD38, a plasma cell surface antigen which is a common drug target for multiple myeloma. This phase 2 randomized controlled trial aimed to assess the safety and efficacy of weekly subcutaneous mezagitimab in patients with persistent or chronic primary ITP. It was found that adverse events occurred at a similar frequency between the intervention and placebo groups. However, serious adverse events were more common in the mezagitimab group, including four which led to treatment discontinuation. With regard to efficacy, those who received higher doses of mezagitimab generally had numerically greater increases in platelet count than placebo groups, although these differences were not statistically significant. In exploratory analyses, patients who received mezagitimab reported subjective improvements in symptom severity, physical activity, and overall quality of life which were not observed in placebo patients. One limitation of this study was a small sample size which had insufficient power for detecting differences in efficacy. In summary, this trial demonstrated that mezagitimab had a favorable safety profile and some potential signs of efficacy as a therapeutic for persistent ITP.

Click to read the study in NEJM

Relevant Reading: Trial in progress: Study design of a randomized, phase 3 trial evaluating the efficacy and safety of mezagitamab (TAK-079) compared with placebo in adults with chronic primary immune thrombocytopenia

In-Depth [randomized controlled trial]: This phase 2 randomized controlled trial evaluated the safety and efficacy of CD38 inhibitor mezagitimab in patients with chronic or persistent primary ITP. Eligible participants were adults who had ITP for at least three months and had an average platelet count of less than 30,000 per microliter. Patients who had recently used rituximab, had a splenectomy, or had a thromboembolic event were excluded. A total of 41 participants were enrolled in two parts. In part A, 24 participants were assigned randomly in a 1:1:1 ratio to receive subcutaneous mezagitimab at a dose of 100 mg, 300 mg, or placebo. In part B, new participants were randomly assigned in a 2:1 ratio to receive either the trial drug at 600 mg or placebo. Safety outcomes were similar between groups, with 9 of 28 participants (68%) in the combined mezagitamab groups and 9 of 13 participants (69%) in the combined placebo groups experiencing any adverse event. Serious adverse events occurred in 14% of patients receiving mezagitimab versus 8% of those receiving placebo; these events included allergic conjunctivitis, staphylococcal bacteremia, renal complications, and worsened thrombocytopenia. Regarding efficacy, the mezagitimab group had numerically greater platelet responses as compared to placebo. For instance, 91% of patients receiving 600 mg of mezagitimab had a clinically meaningful platelet response, compared to 31% of placebo (percentage-point difference, 60; 95% confidence interval [CI], 22 to 86). Exploratory endpoints included patient-reported scales for symptom severity and quality of life; those on higher doses of mezagitimab achieved clinically meaningful improvements on many scales, whereas none on placebo demonstrated improvements. Further, serum studies showed a mean decrease in natural killer cells and IgA, IgG, and IgM in the mezagitimab group. Overall, this small phase 2 study demonstrated that mezagitimab was a safe and potentially effective pharmacotherapy in patients with persistent ITP.

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