Krishnarajah G, Knox H, Graham CN, Christiansen S, Zuraw B. Subcutaneous C1-inhibitor prophylactic treatment for hereditary angioedema: a budget impact model. Poster presented at the 2018 AMCP Managed Care & Specialty Pharmacy Annual Meeting; April 23, 2018. Boston, MA. [abstract] J Manag Care Pharm. 2018 Apr; 24(4-a):S37.

BACKGROUND: Hereditary angioedema (HAE) attacks may be treated acutely with on-demand therapies or prevented with prophylactic medication. A subcutaneous C1-inhibitor (C1-INH [SC] HAEGARDA®, CSL Behring) was approved in 2017 by the FDA as routine prophylaxis to prevent HAE attacks in adolescents and adults, having demonstrated a 95% median reduction in attacks relative to placebo.

OBJECTIVE: An economic model was developed to assess the budget impact of introducing C1-INH (SC) to the market relative to current HAE treatment options, including on-demand therapies and C1-INH (IV) for long-term prophylaxis (LTP).

METHODS: The budget impact was assessed by examining the difference in total annual costs with and without C1-INH (SC) 60 IU/kg on the market for a population with an average patient weight of 80 kg. To estimate the average cost associated with treated and untreated HAE attacks and HAE attack-free periods for each treatment paradigm modeled, a decision-tree model was used to account for differences in treatments over time (eg, method and location of administration, ED visits, hospitalizations), attack severity, and possibility of death due to laryngeal attack. Efficacy of prophylaxis was modeled using (1) median reduction in attacks for the base-case estimate, and (2) mean event ratio for sensitivity analyses conducted around C1-INH (SC) market uptake, dosing of C1-INH (IV), and number of attacks/month.

RESULTS: For a 1-million-member health plan, 19 patients were eligible for HAE treatment (75% on-demand, 25% LTP). Using median reduction in attacks as a measure of efficacy, switching 40% of patients treated with C1-INH (IV) to C1-INH (SC) would result in 37 attacks avoided. Total annual costs for the health plan with and without C1-INH (SC) were estimated at $8.81M and $9.22M, a cost-savings of $408,172 overall, $1,790 per treated member per month (PTMPM), and $0.03 per member per month (PMPM). Using mean attack event ratios (0.15 for C1-INH[SC]), costs with and without C1-INH (SC) would be $8.88M and $9.23M, a cost-savings of $354,079 overall, $1,553 PTMPM, and $0.03 PMPM, with 29 attacks avoided. Under all sensitivity analyses, addition of C1-INH (SC) remained a cost-saving strategy for the health plan.

CONCLUSIONS: In each of the efficacy scenarios and sensitivity analyses, C1-INH (SC) reduced total annual costs associated with HAE treatment. The magnitude of reduction is dependent on the market share gained and size of the treated population (assumed to be 25% of diagnosed HAE patients). Cost savings increased with greater number of HAE attacks avoided.

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