Rituximab Plus Three Cycles of Dexamethasone In the Treatment of Immune Thrombocytopenia (ITP): a Pilot Study.
Authors: Elstrom Rebecca , Lee Soo Y. , Bussel James B. 
Published: October 2019

Abstract
Abstract 3697

Introduction:
Rituximab has been a useful treatment for patients with ITP; many hundreds of patients have been treated. 30–40% of patients will achieve a complete remission (CR: platelet count >150 × 109/l) with initial treatment and, of this group, the CR will last at least a year in almost all patients. However, emerging data suggests that at least 40% of these patients in CR will relapse between 1 and 3 years from initial treatment suggesting that long-term “cures” only occur in 20% of the initial patients. Therefore it would be desirable if CR's could be achieved in more patients and especially if these would be durable in more than 20%. One approach would be to use rituximab maintenance, however it results in suppression of B-cells for more than 2 years. Dexamethasone has also been used to achieve “cure” in ITP especially in adults at or near diagnosis. Cheng's study suggested that approximately 50% of patients would achieve a long-term response with only one 4-day cycle of high dose (40 mg/day) dexamethasone (N Engl J Med, 2003). A follow up study from GIMEMA suggested that 3–4 cycles of dexamethasone would be better than 1 cycle (Blood, 2007). Finally, Zaja's study suggested that rituximab plus one cycle of dexamethasone was superior to dexamethasone alone with a > 50% CR rate at 6 months (Blood, 2010). Therefore, we elected to perform a pilot study to explore the combination of rituximab with three cycles of dexamethasone at 14 day intervals.

Methods:
Patients with ITP with platelet counts < 30,000 off therapy and in need of treatment were enrolled. The standard dose (4 infusions of 375mg/m2) rituximab was given on days 1, 8, 15 and 22 and dexamethasone 40 mg (adjusted for size) on days 1–4, 15–18, and 29–32.

Results:
Fourteen patients between the ages of 4 and 53 years with ITP were treated with rituximab and dexamethasone (R&D) (Table 1). All had received previous steroid therapy as well as other treatments. The median platelet count was 40,000 at initiation of rituximab (range 7,000-230,000); several patients with low counts started with dexamethasone prior to initiating Rituximab to sustain their counts during initial treatment. Patients received rituximab weekly for between 2 and 4 doses and dexamethasone for either 2 or 3 courses at intervals between 1 and 8 weeks (median 2 week intervals). A summary of the results is shown in table 2 demonstrating short-lived platelet increases in response to dexamethasone in almost all patients. With short follow up, there were 7 CR's, 3 PR's and 4 NR's. If this was divided by duration of ITP prior to R&D, there were 4 CR's and 1 NR for ≤ 12 months and 3 CR, 3 PR, and 3 NR for > 12 months. More of the children who were treated had chronic disease than did adults explaining their apparently poorer response. Observed toxicities included hyperglycemia, grade 1 and 2 liver function abnormalities, weight gain, and 1 episode of colitis requiring hospitalization. Three patients opted to skip the third cycle of dexamethasone.

Conclusion:
A regimen of rituximab + 2–3 courses of dexamethasone is active in patients with pretreated ITP with appreciable but usually manageable toxicity. It appears to yield superior results if administered to patients within one year of diagnosis. This combination merits further exploration in a prospective clinical trial.

Disclosures:
Bussel: Portola: Consultancy; Amgen: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; GlaxoSmithKline: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ligand: Membership on an entity's Board of Directors or advisory committees, Research Funding; Shionogi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Eisai, Inc.: Membership on an entity's Board of Directors or advisory committees; Cangene: Research Funding; Genzyme: Research Funding.