The efficacy and safety of mycophenolate mofetil in Thai neuromyelitis optica spectrum disorder patients.

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) often leaves patients with a residual disability after each attack. Several studies have demonstrated that mycophenolate mofetil (MMF) effectively prevents relapse in NMOSD. So far, there has been no data on the effectiveness, dosage, and safety of MMF in the Thai population.

OBJECTIVES

To analyze the efficacy and safety of MMF in Thai NMOSD patients.

MATERIALS AND METHODS

We performed a retrospective review of NMOSD patients at Siriraj Hospital from January 1994 to December 2020. The primary outcomes were changes in annualized relapse rate (ARR) and time to relapse after MMF. Pre- and post-MMF Expanded Disability Status Scale (EDSS) scores and visual functional system scores were also compared.

RESULTS

Fifty-eight NMOSD patients taking MMF were included. The median dose required was 1,250 (IQR 1,000 - 1,500) mg/day or 23.1 (IQR 17.6-30.8) mg/kg/day. Thirty-five patients (65.5%) were relapse-free after MMF with a median follow-up period of 46.8 months (IQR 24.0-60.9). The median ARR was reduced from 0.80 (IQR 0.45-1.39) to 0 (IQR 0-0.31) after MMF treatment (p < 0.001). Over 90% had either stabilized or improved EDSS. The median EDSS score decreased from 3.5 (IQR 3-6) to 3 (IQR 2-6) (p = 0.004). Nine patients experienced adverse events from MMF, with lymphopenia and infection observed in 8.6% and 5.1% of the cohort, respectively. No serious adverse events were observed. A subgroup analysis of 25 patients switching to MMF after azathioprine failure showed a significant ARR and EDSS reduction.

CONCLUSIONS

MMF is effective for relapse prevention in Thai NMOSD patients and has a low risk of adverse events. It could be a salvage therapy for patients with azathioprine failure.