Tacrolimus in the treatment of myasthenia gravis in patients with an inadequate response to glucocorticoid therapy: randomized, double-blind, placebo-controlled study conducted in China

Abstract

Background: To determine the efficacy of low-dose, immediate-release tacrolimus in patients with myasthenia gravis (MG) with inadequate response to glucocorticoid therapy in a randomized, double-blind, placebo-controlled study.

Methods: Eligible patients had inadequate response to glucocorticoids (GCs) after ⩾6 weeks of treatment with prednisone ⩾0.75 mg/kg/day or 60-100 mg/day. Patients were randomized to receive 3 mg tacrolimus or placebo daily (orally) for 24 weeks. Concomitant glucocorticoids and pyridostigmine were allowed. Patients continued GC therapy from weeks 1-4; from week 5, the dose was decreased at the discretion of the investigator. The primary efficacy outcome measure was a reduction, relative to baseline, in quantitative myasthenia gravis (QMG) score assessed using a generalized linear model; supportive analyses used alternative models.

Results: Of 138 patients screened, 83 [tacrolimus (n = 45); placebo (n = 38)] were enrolled and treated. The change in adjusted mean QMG score from baseline to week 24 was -4.9 for tacrolimus and -3.3 for placebo (least squares mean difference: -1.7, 95% confidence interval: -3.5, -0.1; p = 0.067). A post-hoc analysis demonstrated a statistically significant difference for QMG score reduction of ⩾4 points in the tacrolimus group (68.2%) versus the placebo group (44.7%; p = 0.044). Adverse event profiles were similar between treatment groups.

Conclusions: Tacrolimus 3 mg treatment for patients with MG and inadequate response to GCs did not demonstrate a statistically significant improvement in the primary endpoint versus placebo over 24 weeks; however, a post-hoc analysis demonstrated a statistically significant difference for QMG score reduction of ⩾4 points in the tacrolimus group versus the placebo group. This study was limited by the low number of patients, the absence of testing for acetylcholine receptor antibody and the absence of stratification by disease duration (which led to a disparity between the two groups). ClinicalTrials.gov identifier: NCT01325571.

Keywords: immunology; myasthenia gravis; tacrolimus.

Figure 1.

Patient disposition. *The patient was excluded from both the full analysis set and the per-protocol set due to no assessment of quantitative MG scale at any post-baseline visit.

Figure 2.

Mean QMG score with tacrolimus versus placebo over 24 weeks [FAS (LOCF)]. FAS, full analysis set; LOCF, last observation carried forward; QMG, quantitative myasthenia gravis; SD, standard deviation.

Figure 3.

Patients with clinically important improvement in QMG score (⩾4) between baseline and week 24 [FAS (LOCF)]. FAS, full analysis set; LOCF, last observation carried forward; QMG, quantitative myasthenia gravis.