Eltrombopag and High-Dose Dexamethasone As First Line Treatment For ITP

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder that involves antibody and cell mediated destruction of platelets as well as suppression of their production. Prednisone is the initial standard therapy in adults¹. High-dose dexamethasone as front-line therapy given as pulses of 40 mg per day for 4 consecutive days, was effective in 85% of patients, nevertheless, 50% relapsed within six months². The prices of ITP drugs for 1 month of treatment in an adult range from prednisone; $16, eltrombopag; $5,934, intravenous immune globulin (IVIG) (80 g); $9,648, to rituximab (2 g); $15,5963. Only prednisone/dexamethasone and eltrombopag are available in oral presentation, for this reason, ambulatory treatment is an alternative for these patients.

The trombopoietin receptor agonists are effective for the treatment of patients with chronic ITP, although response is dependent on continued administration. Eltrombopag is a small molecule agonist of the c-mpl (TpoR) receptor, which is the physiological target of thrombopoietin. This drug effectively raises the platelet count in adult patients (aged 18 years and over) as second/third line therapy, that is for patients refractory to corticosteroids and IVIG who have had their spleen removed or when splenectomy is not an option4. Our group, as well as others, has previously sought to improve response rates in these patients, particularly with the use of rituximab^{5, 6}. To our knowledge neither eltrombopag nor romiplostim have been used as front line therapy in ITP, therefore the purpose of this study was to assess the efficacy of eltrombopag and dexamethasone in this setting.

This was a prospective, phase 2 study, using the combination of eltrombopag (50 mg PO once a day for 4 weeks) and high-dose dexamethasone (40 mg PO days 1,2,3,4) in untreated adult patients with immune thrombocytopenia or in patients with less than 7 days of treatment with corticosteroids.

Complete response (CR) was defined as an increase in platelet count >100×10⁹/L. Partial response (PR) was defined as an increase in the platelet count greater to 30 ×10⁹/L according to standard criteria. Duration of response was considered from the day of initial administration to the first time of relapse (platelet count <30×109/L).

Twelve consecutive patients were enrolled from June 2012 to June 2013, 6 women and 6 men. The median age at diagnosis was 50 years (range, 20 - 80 years). The median platelet count at diagnosis was 7 x 10⁹/L (range, 2 - 29 x 10⁹/L). Patients were followed for a median of 2.5 months (range 1.1 - 13). After steroid treatment at day +5, ten patients had responded (83.3%), five had achieved CR (41.7%), and five PR. After completing treatment with eltrombopag at day +34, all patients responded (100%), nine patients achieved CR (75%) and three PR (25%). Two patients relapsed in a median time of 39.5 days (range, 30.1 - 49), both regaining CR after treatment with another high-dose dexamethasone course and low-dose rituximab (4 doses of 100 mg every week). At 3 months follow-up 66.7% remained in CR and 33.3% in PR (n=6). At 6 months follow-up two patients remained in CR and two in PR (n=4). Time to best response achieved was 34 days from diagnosis (range, 19 – 64.1). At the end of follow-up 9 patients (75%) remained in CR and 3 patients in PR (25%). Total treatment cost per patient was $1,640 approximately.

Currently the initial treatment of ITP patients is based on prednisone or high dose dexamethasone with or without IVIG. This approach is associated with high cost and high relapse rate. The results from our pilot study suggest that high dose dexamethasone and eltrombopag are very effective as first line treatment for acute ITP in adults. This treatment is ambulatory, affordable and well tolerated; however, we still don't know if this approach will have a favorable impact on the relapse rate of this disease.

Off Label Use: Eltrombopag as first line treatment for ITP.