Comparing the Cost Per Treatment Success of Thrombopoietin Receptor Agonists to Watch & Rescue for the Treatment of Primary Adult Chronic Immune Thrombocytopenia (ITP) in the US

To compare the drug costs relative to response of two thrombopoietin receptor agonists, romiplostim and eltrombopag, to Watch & Rescue for the treatment of chronic immune thrombocytopenia (ITP), from a health plan perspective. ITP, a diagnosis of exclusion, is characterized by low platelet counts and, depending on platelet count level, increased risk of bleeding (Rodeghiero F, et al. Blood. 2009:113(11):2386–2393).

An Excel^® model compared 2011 US drug costs (wholesale acquisition cost) to the overall patient response rates (four or more weekly platelet counts of ≥50 × 10⁹/L during the study from week 2 to 25) observed in individual 6-month placebo-controlled trials for romiplostim, eltrombopag, and placebo (or Watch & Rescue) (http://www.nice.org.uk/nicemedia/live/12025/50715/50715.pdf). These trials studied patients with median baseline platelet counts of 16 × 10⁹/L (in both the romiplostim and eltrombopag trials) with 51% of the eltrombopag and 64% of the romiplostim patients receiving ≥3 previous treatments prior to joining each respective trial (Kuter, D, et al. Lancet. 2008:371:395–403; Cheng G, et al. Lancet. 2011:377:393–402; Bussel, J, et al. Lancet. 2009:373:641–648). The model considers a 55 mg daily dose of eltrombopag, and an average dose (including wastage) derived from a trial-based simulation for the US of 286 mcg per weekly administration of romiplostim. It assumes that 30% of US patients are splenectomized. The model considers a 1 g/kg overall dose of IVIg per rescue event at an average romiplostim trial-based weighted average (by splenectomy status) rate of 2.29 administrations per 6-month period (Weitz, I, et al. Curr Med Res Opin. 2012:28(5):789–796).

For romiplostim patients, the expected cost of treating a patient with romiplostim over a 6-month period (trial period) is $34,655, with an overall response rate of 83%, or a cost per patient with an overall response of $41,753 ($34,655÷83%). The expected 6-month cost of treating the same patient with eltrombopag is $28,516, for an overall response rate of 57%, or a cost per patient with an overall response of $50,028 ($28,516÷57%). Comparatively, the expected 6-month cost of treating the same patient with Watch & Rescue is $11,681, with an overall response rate of 9%, or a cost per patient with an overall response of $129,789 ($11,681÷9%). Patients treated with thrombopoietin receptor agonists experience a 48 to 74% higher overall response rates than patients treated with Watch & Rescue, at a 153 to 196% reduction in resources to achieve the response. Sensitivity analyses were performed on key variables; a ±50% change in the average 6-month cost of IVIg (from either a decrease in cost or a decrease in the average number of administrations) resulted in ±50% change in the Watch & Rescue cost per response ($64,894 to $194,683). A decrease of 25% to the response rates for romiplostim and eltrombopag individually resulted in a 33% increase in the overall cost per patient with an overall response to $55,670 for romiplostim and $66,704 for eltrombopag.

In chronic adult ITP, the use of thrombopoietin receptor agonists represents an efficient use of healthcare resources, with better health outcomes at a significantly lower cost per treatment success than treatment with Watch & Rescue.

Northridge:Amgen Inc.: Consultancy, Research Funding. Danese:Amgen Inc.: Consultancy, Research Funding. Deuson:Amgen Inc.: Employment, Equity Ownership.