ISR Autumn Meeting 2019

1st Place Regular Poster

Robert Harrington

TBA (19A143)

Cost Effectiveness and Efficacy of Reduced Dose Rituximab Biosimilar in a Seropositive Rheumatoid Arthritis DMARD resistant cohort

Author(s)

Robert Harrington Barry O'Shea Richard Conway

Department(s)/Institutions

St. James's Rheumatology Department

Introduction

Low dose rituximab (2x500mg) has been shown to be non-inferior to the original approved dose (2x1000mg) in seropositive rheumatoid arthritis refractory to conventional DMARDs.

Aims/Background

This study assesses the real world application and pharmacoeconomic implications of rituximab biosimilar Truxima at reduced dose of 2x500mg infusions in a small cohort of ACA positive patients.

Method

The patient cohort consisted of DMARD refractory RA patients who were either previously treated with the original licenced dose of 1000mg or biologic naïve. It consisted of 14 patients in total, 3 male and 11 female, with an age range of 49 to 85 and median of 68.

To date, 3 of 14 patients have failed reduced dose Truxima treatment at the usual 6 monthly 2x500mg infusions. Failure was defined as lack of clinical efficacy as defined by DAS28CRP score.

Results

Of note reduced dose Truxima successfully depleted B Cells in all 3 patients deemed to have relapsed. In the first relapse case flow cytometry demonstrated a depleted B Cells but a normal T Cell population. It was decided to administer a further 1g Truxima infusion. In the second relapse case flow cytometry revealed depleted B Cells and a low T Cell population. It was also decided to administer a further 1g Truxima infusion. In the third relapse flow cytometry showed depleted B Cells and normal T cell population. It was deemed safe to switch treatment and commence abatacept to inhibit the T Cell pathway.

Conclusions

Within this small cohort, results to date show successful B cell depletion with reduced dose rituximab biosimilar comparable to conventional full dose. It is known that B cells play a role in stimulating T cell activation in synovium through expression of co-stimulatory molecules. However ongoing flow cytometry B and T cell population analysis demonstrates that B cell depletion alone does not always maintain clinical remission and may be used to aid decision making in switching biologic classes.

From the pharmacoeconomic perspective, the first 12 courses of treatment, where each course consisted of two 500mg Truxima infusions two weeks apart, has saved €33,475 over the first 10 months of investigation.