Fig. 2.

Antibody incidence in ITP patients and healthy subjects across clinical studies. a Pre-existing antibodies to romiplostim or TPO include subjects who had binding antibodies prior to administration of romiplostim. Some of these antibodies continued to persist even after romiplostim dosing and were considered pre-existing. b Post-exposure antibodies to romiplostim or TPO included subjects who had binding antibodies following dosing with romiplostim. Serum samples from healthy subjects that were a part of two initial Phase 1 studies were evaluated for pre-existing and post-exposure binding antibodies to romiplostim and TPO. The antibody incidence was compared to that observed for ITP patients enrolled across ten clinical studies. ITP patients had a higher incidence of pre-existing and post-exposure antibodies to romiplostim as compared to the healthy subjects. Similarly, ITP patients had a higher post-exposure incidence of anti-TPO binding antibodies compared to healthy subjects