Efgartigimod efficacy and safety in refractory myasthenia gravis: UK's first real-world experience.

Background: We report our experience of patients with generalised myasthenia gravis (gMG) treated with efgartigimod, an neonatal Fc receptor antagonist, under the Early Access to Medicine Scheme (EAMS) in the UK.

Methods: Data from all UK patients treated with efgartigimod under the EAMS July 2022 to July 2023 were collected retrospectively. Efgartigimod was administered as per the ADAPT protocol (consisting of a treatment cycle of four infusions at weekly intervals with further cycles given according to clinical need).

Results: 48 patients with acetylcholine receptor antibody-positive gMG were treated in 12 centres. Most (75%) were female and most had a disease duration of over 10 years. The average MG-Activities of Daily Living (ADL) score at baseline was 11.2. Most (72.9%) patients had undergone thymectomy. 77.0% were taking prednisolone at baseline. All patients had used non-steroidal immunosuppressant treatments, the average number tried was 2.6 (range 1-6). 51% had received rituximab. 54.2% of patients required regular intravenous immunoglobulin/plasma exchange.75% of patients had a mean reduction in the MG-ADL of≥2 points in the first cycle and this remained stable throughout the study. The mean intracycle reduction in the MG-ADL score in the first, second, third and fourth cycles were -4.6 to -3.9, -3.4 and -4.2, respectively. Side effects were generally mild. No rescue treatments were required. At the end of the study, 96% of patients remained on efgartigimod.

Conclusion: Efgartigimod is a safe and effective treatment for patients with refractory, treatment-resistant gMG.