(098) Evaluation of Fixed-Dose Rituximab for the Treatment of Non-Malignant Immune-Mediated Hematologic Diseases

Poster Abstract: Background

Rituximab is a chimeric monoclonal antibody that targets the B-cell antigen CD20. Rituximab is currently FDA-approved for the treatment of malignancies, as well as several non-malignant autoimmune disorders. Rituximab is frequently used to treat a variety of non-malignant immune-mediated hematological disorders including thrombotic thrombocytopenic purpura (TTP), immune thrombocytopenic purpura (ITP), acquired hemophilia A (AHA), and autoimmune hemolytic anemia (AIHA). The dosing regimen commonly used in these hematologic disorders is 375 mg/m2 IV for four weeks (standard dosing). Many rheumatologic disorders use a fixed-dose regimen of 1,000 mg IV once every two weeks for two doses. This dosing strategy was developed because non-malignant autoimmune conditions are thought to have a lower total lymphocyte mass and therefore the effective dose of rituximab is likely less. Rituximab is recommended for the treatment of TTP, ITP, AHA, and AIHA, however, societal guidelines do not provide specific dosing recommendations. The University of North Carolina (UNC) Benign Hematology service has historically used the standard dosing regimen for the treatment of non-malignant immune-mediated hematologic disorders. During the COVID-19 pandemic, UNC Benign Hematology moved to utilizing a fixed-dose strategy that has demonstrated efficacy in autoimmune conditions. UNC has continued to utilize the fixed-dose protocol given its simplicity and associated lower costs. Currently, there is a lack literature evaluating the efficacy of a fixed dose regimen in non-malignant immune-mediated hematologic disorders.

Objective

The objective of this study is to compare the efficacy of two different rituximab dosing strategies used for the treatment of hematologic disorders including TTP, ITP, AIHA, and AHA.

Methods

This was a single center, retrospective pre/post study of patients treated with one of two dosing regimens of rituximab for a non-malignant immune-mediated hematologic disorder. Patients meeting the following criteria were included in analysis: (1) age >/= 18 years and (2) treated with either standard dose or fixed dose rituximab for an acute episode of ITP, TTP, AIHA, or AHA between April 1, 2017, and April 1, 2023. Patients were excluded if they received rituximab within the previous year, had an active malignancy, had a history of solid organ or stem cell transplant, were pregnant/breastfeeding, or were HIV, hepatitis B or C positive. The primary outcome was complete response rate at six and twelve months. Secondary outcomes include partial response rate, relapse rate, time to complete response, and incidence of adverse reactions.

Results/Discussion/Conclusions

This study is currently in progress, and results, discussion, and conclusions are forthcoming.

References (must also be included in final poster): RITUXAN (rituximab). FDA. 2012.

Abdulla NE, Ninan MJ, Markowitz AB. Rituximab. ProQuest. 2012;2(26): 71-82.

Zhang XL, Vesely SK, Cataland SR, et al. ISTH guidelines for treatment of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;00:1–7.

Neunert C, Terrell DR, Arnold DM, et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. American Society of Hematology: Blood Advances. 2019;3(23): 3829-3866.

Srivastava A, Santagostino E, Dougall A, et al. WFH Guidelines for the Management of Hemophilia, 3rd edition. Hemophilia. 2020;26(Suppl 6):1–158.

Hill A, Hill QA. Autoimmune hemolytic anemia. Hemolytic Am Soc Hematol Educ Program. 2018(1): 382-389.