Therapeutic Plasma Exchange Eased Refractory MG
Therapeutic plasma exchange improved symptoms related to hard-to-treat myasthenia gravis, resulted in reduced use of immunosuppressants, and was well-tolerated by patients, according to a new study.
That study, “Clinical experience with maintenance therapeutic plasma exchange in refractory generalized myasthenia gravis,” was published in the Journal of Clinical Apheresis.
Although most people with myasthenia gravis (MG) respond well to standard therapies, such as acetylcholinesterase inhibitors, glucocorticosteroids, and immunosuppressants, roughly 10–20% of patients do not. These difficult-to-treat cases are referred to as “refractory” cases.
Therapeutic plasma exchange (TPE), in which a patient’s plasma — the fraction of blood not containing blood cells — is removed, cleaned of potential autoantibodies that trigger disease, and replaced, has emerged as a way to treat acute MG exacerbations. Little is known, however, about how well TPE functions as a long-term maintenance therapy.
To probe this question, a team led by researchers from the University of Missouri, Columbia, examined how one year of maintenance TPE affected the MG composite (MGC) scores, MG activities of daily living (MG-ADL), number of acute exacerbations, medication changes, and adverse side effects among 14 people with refractory generalized MG.
The investigators reviewed the medical charts of these patients, evaluating data at three-month intervals for one year before and after beginning TPE treatment.
Overall, clinically meaningful improvements occurred in MGC and MG-ADL scores. This improvement in scores began gradually after TPE was initiated, reaching clinically significant levels three months after starting therapy and holding over the course of the study period in all participants. Clinically significant levels were determined to be a drop of more than two points on the MG-ADL and of more than three points on the MGC scores.
Participants also needed less daily prednisone and Mestinon (pyridostigmine) use after 12 months of TPE therapy. All participants were taking prednisone prior to starting TPE (average dose of 44.6 mg) and all reduced their daily dose while on TPE to an average of 17.1 mg. The average daily Mestinon dose in 13 patients decreased from 177.7 mg to 83.1 mg after TPE treatment.
Those taking intravenous immunoglobulins (three patients) or rituximab (two patients) no longer needed these medications 12 months after starting TPE.
Importantly, participants experienced a significant reduction in acute MG exacerbations, which fell from a mean of 7.8 annually per patient at 12-month pre-TPE to approximately two per patient over the first year of TPE treatment.
Adverse events related to the treatment often involved the port, or site where the infusion is made into a patient’s body. These included one infection, three cases of bleeding, and difficulty with access at the site. Two patients who experienced bleeding needed a plasma transfusion. Five patients showed sensitivity to the albumin given along with TPE, which was managed by changing brands. One of these individuals had a more severe allergic reaction — anaphylactic reaction — to the first brand of albumin.
Overall, the team concluded that “over a period of 12 months, maintenance TPE therapy for refractory generalized MG improved MG-ADL, and MGC with decreased immunosuppressant requirement, while being well-tolerated.”
“Larger controlled studies with a more robust design are warranted to confirm these additional potential benefits of TPE in treatment-refractory generalized MG,” the team added.