Efficacy and Safety of Rituximab Biosimilars in Treating Immune Thrombocytopenia

Arthur Mageau, PhD

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The results of an observational study suggested that rituximab biosimilars, Rixathon and Truxima, were not only effective but also well-tolerated in the treatment of immune thrombocytopenia.

While these biosimilars have been extensively studied and utilized in various medical conditions, their effectiveness and safety in treating immune thrombocytopenia had not been evaluated until recently. Immune thrombocytopenia is an autoimmune disorder characterized by low platelet counts, leading to an increased risk of bleeding.

Arthur Mageau, PhD, Centre de référence des cytopénies auto-immunes de l’adulte, Service de Médecine Interne, Hôpital Henri Mondor, APHP, UPEC, Créteil, France, and a team of investigators performed the observational study to assess the response rates and safety profile of rituximab biosimilars in adult patients with immune thrombocytopenia.

Assessing Safety and Efficacy of Rituximab Biosimilars

The study employed a matched design which consisted of adults who received a rituximab biosimilar for immune thrombocytopenia treatment. For patients who were rituximab-naive, each individual was matched with 2 controls from the historic immune thrombocytopenia-ritux registry.

The response to the biosimilar was compared with the response to the reference product for non-naive patients. Investigators defined the response status based on international criteria. A total of 107 patients were included, with 55 receiving Rixathon and 52 receiving Truxima.

The Efficacy

After 3 months after the initial infusion of rituximab biosimilars, the overall response rate was found to be 47 out of 74 patients (63.5%) for the biosimilar group compared with 76 out of 142 patients (53.5%) for the matched control group receiving the reference product.

According to the data, this finding was not statistically significant (p = 0.13), though it suggested a favorable trend toward improved response rates in the biosimilar group. Notably, the 3-month overall response rate was 76.5% for Rixathon, which was significantly higher than the matched control group's response rate of 51.5% (p = 0.01).

The response rate for Truxima was 52.5% compared with 55.4% for the matched controls, showing similar response patterns (p = 0.81) to those previously observed with the reference product among non-naive patients.

The Safety

The safety profile of rituximab biosimilars was found to be analogous to that observed with the reference product. No unexpected or severe adverse events were reported in the study population. The study stated this indicates that rituximab biosimilars are not only effective but also well-tolerated in the treatment of immune thrombocytopenia.

The study also stated that although the overall response rate between the biosimilar group and the matched control group did not reach statistical significance, the higher response rate observed with Rixathon provides evidence of its potential superiority.

Furthermore, the comparable response rate of Truxima to the matched control group showed the treatment may be a viable alternative.

"Physicians should remain vigilant about the risk of late-onset post-rituximab neutropenia, especially in patients switching from the reference product to the biosimilar," investigators wrote. "The use of rituximab biosimilars for ITP treatment is a reliable option and offers hope for decreasing the cost of treatment for the challenged healthcare system."

References:

1. Arthur Mageau, Bernard Bonnotte, Mikael Ebbo, Antoine Dossier, Lionel Galicier, Odile Souchaud-Debouverie, Corentin Orvain, Mathieu Gerfaud-Valentin, Delphine Gobert, Etienne Riviere, Sylvain Audia, Matthieu Mahevas, Marc Michel, Jean-Francois Viallard & Bertrand Godeau (2023) Efficacy and safety of two rituximab biosimilars for treating immune thrombocytopenia: a reference-product matched study, Platelets, 34:1, DOI: 10.1080/09537104.2023.2200848