A Predictive Cost-Effectiveness Analysis of the Treatment of Chronic, Refractory Immune Thrombocytopenic Purpura (ITP) with Novel Agents: An Economic Model Based on Long-Term Treatment Data with Rituximab Versus Romiplostim.

Introduction : Novel non-surgical options for treatment of chronic immune thrombocytopenic purpura (ITP) are emerging. These include rituximab, an anti-CD20 monoclonal antibody, and romiplostim, a soon to be approved thrombopoeitic receptor agonist. However, long-term clinical data with these agents have not been reported previously and the cost of romiplostim treatment has not been announced. Herein, we report a “break-even” cost-effectiveness analysis, based on 2.5 years clinical outcome data for both agents, which yields a suggested market cost for romiplostim that would result in equivalent cost-effectiveness profiles for the two agents when administered as treatment for chronic ITP.

Methods: Effectiveness data were based on 2.5-years results from studies of chronic ITP patients treated with rituximab or romiplostim. We calculated the total costs of treating a cohort of chronic ITP patients with ritiuxan with splenectomy salvage (estimated cost of $8,100) as the therapeutic choice for treatment failures. We subsequently calculated a break-even price for romiplostin with splenectomy salvage that would result in a total cost of treating an ITP cohort equivalent to the costs of treating the rituximab/splenectomy cohort.

Results: At 2.5 years follow-up, a cohort of 100 chronic ITP patients initially treated with rituximab is associated with 40 therapeutic failures going on to splenectomy annually. Total treatment costs for this cohort is estimated at $2.2 million. At 2.5 years follow-up, a cohort of 100 chronic ITP patients initially treated with romiplostim is associated with 10 splenectomy failures per year. Total 2.5 year treatment costs for this cohort is $1.9 million for splenectomy plus the costs of treating 70 ITP patients with romiplastim for 2.5 years, 20 ITP patients for two years, and 10 ITP patients for one year. Hence, annual break-even costs for romipslatim are estimated at $20,000. The higher annual cost with romiplostim versus rituximab is related to better 2.5 year outcome rates. Hence, these cost estimates are preliminary, pending reporting of additional long-term studies.

Conclusions: It will be of interest to compare this value with cost-effectiveness estimates that are based on actual pricing of romiplostim (when the drug receives FDA approval). Policy makers would be wise to develop break-even cost estimates for novel drugs prior to FDA approval. These analyses may help inform initial price setting efforts.