Abstract 2514

The overall short term effectivity of Rituximab in the treatment of ITP is reported to be around 50%. In most studies the traditional CD20 dosing scheme of 4 weekly interspaced 375 mg/m2 doses is used although other single-arm studies suggest comparable effectivity of lower doses. To investigate alternative dosing schemes, we conducted an open label phase II multicenter trial and randomized 156 ITP patients that were refractory for corticosteroid treatment, between three schemes. Questions were: are higher CD20 peak levels of value and is dose saving a feasible approach in early responding patients? The treatment arms were: A) 375 mg/m2 once a week for 4 weeks, B) 750 mg/m2 once a week for 2 weeks and C) 375 mg/m2 once a week for 2 weeks, in early and sustained responding patients (= within 15 days and still responding at 43 days) and another 2 × 375 mg/m2 to patients not fulfilling these criteria. In retrospect, seven of the 156 patients appeared ineligible at randomization and were therefore excluded from all analyses. Here we report on the best response within 71 days as primary end point for the first 105 patients that were included, i.e. 35 per treatment arm

Arm A (n=35) 4 × 375 mg/m2Arm B (n=35) 2 × 750 mg/m2Arm C (n=35) 2 or 4 × 375 mg/m2
Patient characteristics    
Male/female, % 37/63 49/51 43/57 
WHO 0/1/2/not reported, % 86/6/–/9. 77/20/3/– 91/9/–/– 
Age in years, median (range) 56 (19–77) 56 (17–82) 41 (18–80) 
On stable corticosteroid, % 36 29 46 
Splenectomized, % – 15 11 
Baseline plt count × 109/l, median (range) 16 (3–31) 15 (1–30) 19 (2–30) 
Treatment outcome, %    
Early responses in Arm C   26 
All best responses within 71d 46 42 51 
CR: >150 × 109 plt/l 20 14 14 
GR: >50 × 109 plt/l 20 14 23 
MR: >30 × 109 plt/l AND >2 × baseline 6 14 14 
No response 54 58 49 
Treatment failure at 6 months, % (standard error) 57 (8) 60 (8) 54 (9) 
Arm A (n=35) 4 × 375 mg/m2Arm B (n=35) 2 × 750 mg/m2Arm C (n=35) 2 or 4 × 375 mg/m2
Patient characteristics    
Male/female, % 37/63 49/51 43/57 
WHO 0/1/2/not reported, % 86/6/–/9. 77/20/3/– 91/9/–/– 
Age in years, median (range) 56 (19–77) 56 (17–82) 41 (18–80) 
On stable corticosteroid, % 36 29 46 
Splenectomized, % – 15 11 
Baseline plt count × 109/l, median (range) 16 (3–31) 15 (1–30) 19 (2–30) 
Treatment outcome, %    
Early responses in Arm C   26 
All best responses within 71d 46 42 51 
CR: >150 × 109 plt/l 20 14 14 
GR: >50 × 109 plt/l 20 14 23 
MR: >30 × 109 plt/l AND >2 × baseline 6 14 14 
No response 54 58 49 
Treatment failure at 6 months, % (standard error) 57 (8) 60 (8) 54 (9) 
View Large

So far, on the basis of the within 71 days overall response data, no superior dosing scheme of CD20 can yet be discerned.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
inosine triphosphate, interim analysis, phase 2 clinical trials, purpura, thrombocytopenic, idiopathic, rituximab, cd20 antigens, adrenal corticosteroids, glucocorticoids, mineralocorticoids, standard error

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2010 by The American Society of Hematology
2010
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