Low-Dose Rituximab In Idiopathic Autoimmune Hemolytic Anemia: Biological Studies
Authors: Barcellini Wilma , Zaja Francesco , Zaninoni Anna , Imperiali Francesca Guia , Battista Marta Lisa , Di Bona Eros , Consonni Dario , Zanella Alberto 
Published: October 2019

Abstract
Abstract 3206

Background:
Conventional therapy of warm autoimmune hemolytic anemia (WAIHA) include administration of corticosteroids and immunosuppressive agents, or splenectomy, whereas no effective treatment exists for cold hemagglutinin disease (CHD). A substantial proportion of patients with WAIHA do not respond to or relapse after corticosteroid therapy and may experience clinically relevant side effects. Favorable responses to rituximab at standard doses (375 mg/m2 weekly for 4–6 courses) have been reported in both WAIHA and CHD, idiopathic or secondary, as well as in other autoimmune diseases, such as rheumatoid arthritis and primary immune thrombocytopenia. Recently, low dose (LD)-rituximab (100 mg fixed dose weekly for 4 courses) has been proven effective in patients with autoimmune cytopenias, particularly immune thrombocytopenia.

Aims:
To evaluate the safety, activity and the duration of the response of LD-rituximab associated with standard oral prednisone (PDN) as first line therapy in newly diagnosed WAIHA and CHD, and as second line therapy in WAIHA relapsed after standard oral PDN. To correlate the clinical response to biological parameters (cytokine and anti-erythrocyte antibody production).

Methods:
In this single-arm prospective pilot study, LD-rituximab was administered at 100 mg fixed dose weekly on days +7, +14, +21, +28 along with standard oral PDN (1 mg/kg/die p.o. from day +1 to + 30, followed by quick tapering: 10 mg/week until 0.5/mg/kg/die, then 5 mg/week until stop). Complete and partial initial responses (iCR and iPR) were defined as Hb >/= 12 g/dL and >/= 10 g/dL at month +2 from the beginning of therapy, respectively; sustained response (SR) was defined as Hb >/= 10 g/dL at month +6 and +12, in the absence of any treatment. Mitogen stimulated cultures were performed to measure anti-RBC antibodies (at enrolment and month +1, +3, +6 and +12) and cytokines (at enrolment and month, +3, and +6) by ELISA.

Results:
Twenty-one patients (14 female, 7 male; median age 52 yrs, range 28–77) were enrolled after informed consent. The median follow-up was 11 months (range 2–25). An iCR and iPR were observed in 14 (67%) and 4 (19%) out of 21 patients, respectively; the median Hb level increased from 9.1 g/dL (range 4.4–12.3) at enrolment to 12.5 g/dL (range 9.1–15.3) at month +2. A SR at month +6 was observed in 13/14, and at month +12 in 11/11 evaluable patients. A total of 3 patients relapsed: one at month +16 (retreated with the same protocol with iPR at month +18), another at month +7 (retreated with a SR at month +13), ad the last at month +5 (splenectomy planned). No side effects or serious adverse events were observed. For 10 relapsed AIHA patients (with a follow-up post treatment of at least 12 months) laboratory data (Hb, LDH, reticulocytes) and steroid administration were available before LD-rituximab treatment: a lower cumulative dose (roughly 50%) of steroid was administered to patients during LD-rituximab study compared with previous therapy, without significant differences in the general trend of Hb, LDH, and reticulocytes. Biological studies showed that anti-RBC antibody production decreased until month +6 (from 556 ng/ml at enrolment to 125 ng/ml) and slightly increased at month +12 (307 ng/ml). Regarding cytokine production, at enrolment TNF-α, IFN-γ, IL-12 and TGF-β were lower in patients vs controls, and increased at month +6, without reaching normal values. IL-17 was 10-fold normal values at enrolment, and diminished during the follow-up without reaching normal values. These preliminary results seem to indicate that the addition of LD-rituximab to standard corticosteroid therapy is a feasible and active treatment in AIHA. Data on SR are intriguing, particularly regarding the possible steroid sparing effect of LD-rituximab. Cytokine and anti-erythrocyte antibody production offer new insights into the immunomodulating activity of the drug.

Disclosures:
No relevant conflicts of interest to declare.