Cost per Treatment Success of Thrombopoietin Receptor Agonists Vs "Watch and Rescue" Strategy for Treating Adult Non-Splenectomized Patients with Chronic Immune Thrombocytopenia: A US Payer Perspective

Background:

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelet count level and increased risk of bleeding. Non-splenectomized patients account for the vast majority of adult patients with ITP in US clinical practice (Cetin et al, Blood, 2014).

Two thrombopoietin receptor agonists (TPO-RAs, romiplostim [once-weekly subcutaneous injection] and eltrombopag [once-daily oral agent]) are indicated for the treatment of non-splenectomized adults with chronic ITP who have had an insufficient response to corticosteroids or immunoglobulins. Both TPO-RAs have been shown to increase and maintain platelet counts and reduce the incidence of bleeding-related episode (BRE, defined as a bleeding event and/or use of rescue therapy).

Using a US payer perspective and recent price and cost data, this analysis estimates the cost relative to treatment success (measured as overall platelet response) of the two TPO-RAs and a "watch and rescue" strategy (monitoring patients until rescue therapies [eg, intravenous immunoglobulin] are required) in non-splenectomized adults with chronic ITP.

Methods:

The analysis was conducted based on time horizon (24 weeks) and data for non-splenectomized patients of phase 3 registrational trials of romiplostim (Kuter et al, Lancet, 2008) and eltrombopag (Cheng et al, Lancet, 2011) in adult patients with chronic ITP.

Rates of overall platelet response (see definitions based on number of weeks with platelet count ≥ 50 x 10⁹/L in Cooper et al, Int J Technol Assess Health Care, 2014) were estimated using trial data (Kuter et al, Lancet, 2008; NICE Appraisal of Eltrombopag, 2012): 87.8% for romiplostim, 71.8% for eltrombopag, and 14.5% for "watch and rescue" (from pooled data for placebo arms).

Drug acquisition cost was calculated using wholesale acquisition cost values as of July 16, 2015 ($5.8256 per mcg for romiplostim, $4.0824 per mg for eltrombopag 25 mg tablet, $3.9875 per mg for eltrombopag 50 or 75 mg tablet) and average dose in the trials (317 mcg/week for romiplostim [assuming 100% wastage of unused dose in an opened vial], 55 mg/day for eltrombopag).

Costs for drug administration (for romiplostim only, once per week), physician visit and platelet count monitoring (for all three strategies, once per week in weeks 1-4 and once every 4 weeks in weeks 5-24), and liver function monitoring (for eltrombopag only, once every 2 weeks in weeks 1-4 and once every 4 weeks in weeks 5-24) were obtained from CMS Physician Fee Schedule (July 2015 release) and Clinical Laboratory Fee Schedule (January 2015 release).

Cost of BREs (ie, cost for treating bleeding events and/or cost for rescue therapy) was derived on the basis of incidence rates of BRE (0.128 per patient-week for non-responder and 0.031 per patient-week for responder, calculated from data reported in Weitz et al, Curr Med Res Opin, 2012) and average treatment cost per BRE ($6,006, in inflation-adjusted June 2015 $) estimated from BREs identified during 2007-2013 in a study of a large US administrative healthcare claims database (Cetin et al, Blood, 2014).

Cost per response was computed as total cost (summation of all the cost items aforementioned) divided by overall platelet response rate.

Results:

The cost per response results by treatment strategy are summarized in the Table. Compared to the "watch and rescue" strategy, use of any of the two TPO-RAs is associated with a fewer number of BREs, a lower cost for treating BREs, and a lower cost per response. Cost per response estimates of the two TPO-RAs are broadly comparable, with romiplostim associated with lower cost per response than eltrombopag.

Conclusion:

In non-splenectomized adults with chronic ITP, the use of TPO-RAs represents an efficient way in achieving treatment success, with lower cost per treatment success than the "watch and rescue" strategy.