Prophylactic Rituximab May Decrease Relapse in Immune Thrombotic Thrombocytopenic Purpura

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Prophylactic rituximab may decrease relapse in immune thrombotic thrombocytopenic purpura by maintaining detectable levels of ADAMTS13 activity.
Prophylactic rituximab may decrease relapse in immune thrombotic thrombocytopenic purpura by maintaining detectable levels of ADAMTS13 activity.

Maintenance of activity levels of ADAMTS13 above 10% can prevent relapse in patients with immune thrombotic thrombocytopenic purpura (iTTP), according to a recent study published in Blood.

ADAMTS13 is an enzyme that cleaves a protein involved in blood clotting. According to the authors of the study, prophylactic rituximab can decrease clinical relapse in patients by maintaining detectable levels of ADAMTS13 activity and has a favorable long-term risk-benefit profile.

Researchers assessed the long-term outcomes of 92 patients with iTTP in clinical remission who received prophylactic rituximab after detection of ADAMTS13 activity under 10% during follow-up. Data were from a French registry. All patients were followed for at least 1 year and measurements of ADAMTS13 activity were taken every 3 months.

The study included 92 patients and 37 experienced more than 1 iTTP episode. The median cumulative relapse incidence prior to preemptive rituximab was 0.33 episodes per year (interquartile range [IQR], 0.23-0.66).

After receiving preemptive rituximab, the median cumulative relapse incidence across all patients decreased to 0 episodes per year (IQR, 0-1.32; P <.001). Therapy with rituximab resulted in sustained recovery of ADAMTS13 activity in 37% of patients during more than 2.5 years of follow-up.

Severe ADAMTS13 deficiency (<10%) recurred in 49% of patients after an initial improvement. Additional rounds of rituximab typically resulted in improvements in ADAMTS13 activity. ADAMTS13 activity remained undetectable in 14% of patients after the first round of rituximab. Nonetheless, retreatment with rituximab was efficacious in 6 of 10 cases.

A total of 15% of patients experienced clinical relapse, and 20.7% of patients experienced benign adverse events. Four patients experienced serum sickness. No severe infections or interruptions to treatment occurred.

In patients who responded to therapy, prophylactic rituximab correlated with a change in ADAMTS13 conformation. In a group of 23 historical patients with iTTP and persistently undetectable ADAMTS13 activity, 74% experienced clinical relapse after a 7-year follow-up.

“Additional studies are needed to determine the optimal dose of rituximab and to better identify, among patients with undetectable ADAMTS13 activity, those at a higher short-term risk of relapse and who will need a more personalized preemptive strategy,” concluded the authors.

Reference

1. Jestin M, Benhamou Y, Schelpe AS, et al. Preemptive rituximab prevents long-term relapses in immune-mediated thrombotic thrombocytopenic purpura [published online August 16, 2018]. Blood. doi: 10.1182/blood-2018-04-840090

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