Tacrolimus Plus High-Dose Dexamethasone Versus High-Dose Dexamethasone Alone As First-Line Treatment for Adult Immune Thrombocytopenia: The Phase 2, Open Label, Randomized Trial (TARGET 020)

Introduction

Immune thrombocytopenia (ITP) is an acquired, organ-specific, autoimmune disease and one of the most common bleeding disorders seriously endangering human health. Glucocorticoids and intravenous immunoglobulin are first-line treatments recommended by guidelines for patients with ITP. However, approximately 50%-85% of patients relapse during the first year of treatment. In addition, long-term use of glucocorticoids increases the risk for dose- and time-dependent glucocorticoid-related complications and serious side effects. Therefore, in-depth studies investigating new solutions for the first-line treatment of ITP are urgently needed. Tacrolimus is a calcineurin inhibitor, which forms a complex by binding to FK506-binding protein. It is currently widely used in the prevention of graft-versus-host disease for organ transplantation as well as for the treatment of autoimmune diseases. In addition to recent retrospective studies and case reports demonstrating its effectiveness in ITP, tacrolimus has been shown to improve anti-platelet antibody-mediated thrombocytopenia in mice, suggesting it may be a potential treatment for ITP. The aim of this study was to compare two first-line treatment options for ITP-a standard glucocorticoid-only regimen versus tacrolimus in combination with a standard glucocorticoid regimen-to determine which could help patients achieve stable platelet counts faster and experience a longer duration of remission.

Methods

This open-label, randomized, phase 2 trial, enrolled adult ITP patients from seven different tertiary medical centers in China. Elderly patients had confirmed, newly diagnosed, treatment-naive ITP, platelet counts <30×10 ⁹/L, or < 50×10 ⁹/L and significant bleeding symptoms (World Health Organization bleeding scale ≥ 2). Eligible patients were randomly assigned 1:1 with an interactive web-based response system to receive either oral tacrolimus (initial 0.03 mg/kg/day and maintain blood concentration at 3-5 ng/mL for 12 weeks) plus high-dose dexamethasone (HD-DXM) or HD-DXM monotherapy for 12 weeks. DXM (40 mg) was administered orally daily for 4 consecutive days to both study arms. The 4-day course of DXM was repeated on days 11-14 in patients who lacked response by day 10. The primary endpoint was 6-month sustained response (SR), defined as platelet count maintained >50×10 ⁹/L without any additional ITP-modifying therapy at the 6-month follow-up. Key secondary endpoints included initial response by day 14 (OR, platelet count ≥30×10 ⁹/L and at least 2-fold increase in baseline platelet count and absence of bleeding; and CR, platelet count ≥ 100×10 ⁹/L), duration of response, bleeding scores, and adverse events (AEs). This trial was registered with ClinicalTrials.gov (NCT04747080).

Results

Total 140 patients newly diagnosed with ITP were randomly assigned to either the tacrolimus plus HD-DXM (n=72) or HD-DXM monotherapy (n=68) groups. At the 6-month follow-up, the proportion of patients exhibiting SR was significantly higher in the tacrolimus plus HD-DXM group than in the HD-DXM monotherapy group (65.3% vs 42.6%, p= 0.007). Of the 140 patients with ITP (males accounted for 48.6%), the mean age was 32.8 years, the mean platelet count was 16.7×10 ⁹/L. The combination group exhibited a higher 14-day early remission rate than the monotherapy group (76.4% vs 55.9%, P=0.001). Significantly fewer treatment failures occurred in patients randomly assigned to the combination group(19.4% vs 38.2%, P=0.0014). During the follow-up period, fewer patients in the combination group experienced relapse than in the monotherapy group; the median time to relapse was 77 days (Tacrolimus+HD-DXM) vs 36 days (HD-DXM). The combination group exhibited a lower proportion of bleeding events and a lower bleeding score. The incidence of serious AEs, rescue therapy, and treatment side effects were similar between the two groups, and treatment was well tolerated by all patients, with no grade 4 AEs or treatment-related deaths reported. There was no statistically significant difference in the incidence of treatment-related AEs between the two groups.

Conclusions

Low-dose tacrolimus plus HD-DXM was an effective and safe treatment for ITP as first-line therapy and elicited a sustained prolonged response in adults. This therapy may be a new treatment option for adult patients with ITP.