Tacrolimus as Single-Agent Immunotherapy for Adult-Onset Myasthenia Gravis: Remission, Relapse, and Safety

To identify factors influencing remission and relapse, and to evaluate the safety of tacrolimus monotherapy (TAMO) in adult-onset mild-to-moderate myasthenia gravis (MG).

This retrospective analysis was conducted on MG patients receiving TAMO. Remission was defined as achieving minimal symptom expression (MSE), and multivariable Cox regression analysis identified predictors of remission and relapse. Cancer risk was assessed by standardized incidence ratio (SIR), based on the age-specific cancer incidence rates in China in 2022.

Among 153 patients, 77.8% achieved MSE, with a median time of 6.0 months. Age at onset (hazard ratio [HR] = 0.982, 95% confidence interval [CI] = 0.968-0.995, p = 0.009) and new-onset MG (HR = 2.065, 95% CI = 1.266-3.368, p = 0.004) were independent predictors of time to achieving MSE. The optimal cut-off value for age at onset was 70 years. Relapse occurred in 31% of patients. Tacrolimus concentration at MSE (HR = 0.815, 95% CI = 0.695-0.956, p = 0.012) and dose reduction speed (HR = 1.717, 95% CI = 1.280-2.305, p < 0.001) were independent predictors of relapse. The cut-off values were 5.30 ng/mL and 1.08 mg/year, respectively. Adverse drug reactions (ADRs) occurred in 45.0% of the 200 patients receiving TAMO, with hyperglycemia being the most common (17.5%). Eight patients developed cancer, and the SIR was 2.86 (95% CI = 1.23-5.63, p = 0.005) compared with the general Chinese population.

TAMO was associated with higher rates of MSE in adult-onset mild-to-moderate MG patients with new-onset disease or with an onset age ≤ 70 years. To avoid MG relapse, tacrolimus concentration > 5.30 ng/mL at MSE and dose reduction speed ≤ 1.08 mg/year can be considered. Cancer surveillance may be considered for elderly patients undergoing long-term tacrolimus therapy. Limitations include the retrospective, uncontrolled design, moderate sample sizes, and limited follow-up duration; thus, long-term safety, particularly cancer risk, requires further validation.