Rituximab-Plasma Exchange Combo Reduced MG Severity

Combination therapy of rituximab and plasma exchange reduced disease severity in nine patients with refractory myasthenia gravis, a case series reports. 

The case series, “Treatment of refractory myasthenia gravis by double‐filtration plasmapheresis and rituximab: A case series of nine patients and literature review,” was published in the Journal of Clinical Apheresis. 

Myasthenia gravis (MG) is caused by autoantibodies in the body’s immune system attacking components of the neuromuscular junctions — the sites where nerves and muscle cells communicate — causing muscle weakness. The major autoantibodies associated with MG are against proteins critical to the function of the neuromuscular junction, namely acetylcholine receptors (anti-AchR) and muscle-specific kinase (anti-MuSK). 

Patients with refractory MG are resistant to conventional treatments such as acetylcholinesterase inhibitors, corticosteroids and thymectomy (surgical removal of the antibody-producing thymus gland). Those patients have had promising outcomes with rituximab, which depletes antibody-producing B-cells, and plasma exchange (or plasmapheresis), in which a patient’s blood plasma is removed, filtered of harmful autoantibodies, and returned to the body.

The case series is the first to describe patients resistant to previous therapies who were treated with both double-filtration plasmapheresis (DFPP) and rituximab. The study was conducted at a single center in France with data collected retrospectively from nine refractory MG patients treated from 2018 to 2020. Clinical response to treatment was measured using the Myasthenia Gravis Foundation of America (MGFA) classification before and after treatment, and at one month, six months, and one year post-treatment.

Of the nine patients, six were women and the average age was 53. All nine patients experienced a reduction in disease severity following treatment. Before treatment, three patients were retired and six were on sick leave. Of the six employed patients, five returned to work and all nine reported self-sufficiency post-DFPP. No serious side effects were reported in any patient. 

Patient 1 was a 76-year-old woman with anti-AchR MG who had a thymectomy. Due to previous treatment resistance, she received five daily DFPP sessions followed by one rituximab infusion. Her muscle weakness, as assessed by the MGFA score, was reduced from moderate after the fifth DFPP session and remained mild at each post-DFPP follow-up. Following treatment, she no longer required an at-home nurse.

Patients 2 and 3 had anti-AchR MG and both initially refused rituximab treatment. Patient 2, a 38-year-old woman with asthma, received 11 DFPP sessions after her MG worsened postpartum. The treatment decreased her muscle weakness from moderate to mild, and she maintained remission for one-year post-DFPP. In turn, patient 3, a 70-year-old man, had 10 DFPP sessions. His muscle weakness was moderate, and he relapsed one month after treatment, prompting two rituximab infusions. His muscle weakness, while still moderate, eased and remained stable for one year.

Patients 4 and 5 had anti-MuSK MG. Patient 4, a 27-year-old man, had five daily DFPP sessions followed by a rituximab infusion, reducing muscle weakness to moderate and being clinically stable for eight months post-DFPP. At age 54, patient 5 had five daily DFPP sessions followed by a rituximab infusion that reduced her muscle weakness from moderate to mild, but failed to achieve remission before a second rituximab infusion.

In turn, patients 6 and 8, both women, had a form of thyroid gland inflammation known as Hashimoto’s thyroiditis and anti-AchR MG.

Patient 6, age 60, had two DFPP sessions with 28 sessions of immunoadsorption (IA) — removal of antibodies from circulation — which reduced muscle weakness to moderate. After three rituximab infusions, she discontinued IA sessions and achieved clinical stability with mild muscle weakness, maintained at two years post-DFPP. The 71-year-old patient 8 underwent many treatments, including thymectomy. As her symptoms worsened, she received 10 DFPP sessions, followed by three rituximab infusions, and remained in stable clinical condition with mild muscle weakness 25 months post-DFPP.

Patients 7 and 9 were both women with a history of pulmonary embolism (blockage of lung arteries) when diagnosed with MG. The 34-year-old patient 7 was hospitalized one month after her MG diagnosis for acute respiratory distress requiring intubation. She had a relapse after previous treatments including two rituximab infusions. The patient received seven DFPP sessions and a third rituximab infusion, reducing muscle weakness from the most severe to mild. She subsequently underwent thymectomy and remained in stable remission at 29 months post-DFPP.

Patient 9, a 48-year old with a history of endometriosis, received five DFPP sessions over five days, followed by two rituximab infusions, which decreased her muscle weakness from severe to moderate, and then mild. She relapsed after three months and received 10 DFPP sessions along with pyridostigmine bromide (sold as Mestinon, among others), followed by a rituximab infusion. Although her muscle weakness decreased, she was the only patient who remained on sick leave at study conclusion.

“A combined therapy of [DFPP and rituximab] is a good therapeutic option for MG patients, particularly those that had anti-AchR or anti-MuSK autoantibodies; this combined therapy could be started very early after MG diagnosis,” the scientists wrote. 

Rituximab is sold under the brand name Rituxan in the U.S. and MabThera in Europe, among others.