Re-Treatment with Rituximab in ITP: Comparison of Standard Dose with 2 Forms of Augmented Rituximab.

The purpose of this study was to investigate treatment (tmt) with Rituximab ® in patients (pts) with ITP who had previously received R. Re-treatment (re-tmt) was administered either at standard (std) dose (375 mg/m2 x 4) n=15 or as augmented R, n= 14 (below). Eligibility criteria included primary chronic ITP, platelet count (plt ct)< 30K x 2 within a month, age > 12 years, and prior receipt of std dose R.

Augmented R pts were randomised to receive either R-CVP (group A,n=7) or Double Dose R (DDR) (group B,n=7). Group A pts received 1 dose of std dose R 1st and then 3 doses of R-CVP consisting of R, IV doses of Cyclophosphamide 750 mg/m² & vincristine 1.4 mg/m² (max 2 mg) and 100 mg prednisone PO daily for 5 days at 3 week intervals. Group B pts were treated with R 750 mg/m²/dose IV weekly for 4 weeks. Pts could receive IVIG during the initial tmt period. Two heavily pre-treated pts did not tolerate R-CVP well and refused the 3rd cycle; 1 std dose pt had an allergic reaction and could not complete her 4th infusion of re-tmt. Otherwise tmt was well tolerated. All pts had decline in circulating CD 19 positive B cells to < 0.03 X 10⁹ and there were no significant decreases in IgG or IgM levels.

The table below summarises the response to the various tmts with R.

Among 15 pts on re-tmt with std dose R after ITP relapse, there were 7 complete responses (CR’s) (plt ct > 150,000/ul [150k] for 2 consecutive weeks) and 3 partial responses (PR’s) (plt ct between 50–150k for 2 consecutive weeks). Response to the 1st and 2nd std dose tmt courses was similar (n=15) but 3 pts (#3, 17 & 20 {see table}) with initial CR’s had limited to absent responses to re-tmt. No HAMA or HACA were detected in the 3 pts.

With augmented R, there were 3 CR’s among 7 pts randomized to the DDR group (#2, 11, 12). All 3 pts also had CR’s with the 1st tmt. Among 7 pts randomized to the R-CVP group, 1 pt had CR (also had CR with 1st R), 1 had PR (#6) and 4 pts failed to respond altogether; 1 pt just started R-CVP. No pt who did not respond to initial std dose R, responded to either DDR or R-CVP (see figure). 4 pts received re-tmt with std dose R and then augmented R. At this time it does not seem that augmented R has provided additional benefit to these 4 or the other retreated pts.

In conclusion, Rituximab re-tmt at std or double dose is well tolerated and generally produces similar response durations to initial R tmt in pts with relapsed chronic ITP. However 3/15 CR pts had no response to re-tmt. Augmented R, either as R-CVP or as DDR, did not provide any clear benefit to pts not responding initially to std R but may be superior to std dose R in some pts. R-CVP was less well tolerated than other regimens.

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Quality of Response: Comparision of Initial Treatment Vs Re-Treatment with DDR R-CVP

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Quality of Response: Comparision of Initial Treatment Vs Re-Treatment with DDR R-CVP

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