Efgartigimod efficacy and safety in refractory Myasthenia Gravis - UK’s first real-world experience

Background We report our experience of patients with generalised MG (gMG) treated with Efgartigimod, an FcN antagonist, under the Early Access to Medicine Scheme (EAMS) in the UK. Methods Data from all UK patients treated with Efgartigimod under the EAMS June 22-July 23 were collected retrospectively. Efgartigimod was administered as per the ADAPT protocol (consisting of a treatment cycle of 4 infusions at weekly intervals with further cycles given according to clinical need). Results 48 patients with AChR 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-ADL score at baseline was 11.2. Most (72.9%) patients had undergone thymectomy. 77.0% were taking prednisolone at baseline. All patients had utilized non-steroidal immunosuppressant treatments, the average number tried was 2.6 (range 1-6). 51% had received Rituximab. 54.2% of patients required regular IVIg/PLEX. 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 1st, 2nd, 3rd and 4th cycles were -4.6, -3.9, -3.4 and -4.2 respectively. Side effects were generally mild though one patient stopped treatment due to severe hypokalemia. 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of King's College Hospital gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. * ### ABBREVIATIONS IQR : interquartile range IVIg : intravenous immunoglobulin g MG : generalised MG MG : Myasthenia Gravis MG-ADL : Myasthenia Gravis Activities of Daily Living NSIST : non-steroid immunosuppression treatment TPE : plasmapheresis