Treatments: Will targeting autoantibodies work?
In the second part of her talk, Dr. Scheibenbogen summarized clinical trials of the following treatment approaches that involve targeting autoantibodies as a way to alleviate ME/CFS symptoms:
Rituximab: Work on infusions of the B-cell depleting agent has been conducted by Norwegian researchers beginning in 2011 with a small randomized trial and an open-label, phase 2 study in 2015, both showing clinical responses in ME/CFS. However, a subsequent phase 3, randomized clinical trial of 151 patients, again diagnosed using the Canadian criteria, was negative.
There are several possible explanations for this, Dr. Scheibenbogen noted. For one, the maintenance dose had to be reduced because of a lack of financial support. “This was probably critical. The lower dose was insufficient to adequately deplete B cells.” Also, there may have been a strong placebo response in the control group since they were being given better care than they normally would receive during the trial. “I think probably nobody will again do a rituximab trial. This was very disappointing for all of us. But, we still have other opportunities to follow this path,” she said.
Dr. Komaroff agreed. “I don’t think the failure of one drug that hits malignant B cells is proof against the autoimmune hypothesis per se. I think the evidence is that rituximab doesn’t work, but that doesn’t invalidate the autoimmunity hypothesis.”
Cyclophosphamide: The same Norwegian group also showed positive findings in an open-label, phase 2 trial of the immune-modifying drug cyclophosphamide in 22 of 40 patients. Interestingly, HLA risk alleles were much more common in responders than nonresponders, Dr. Scheibenbogen noted.
Immunoadsorption: This technique, similar to dialysis, involves separating out the blood plasma by centrifugation and removing IgG autoantibodies by a binding column, then returning the plasma back to the patient. It is used, primarily in Europe, to treat severe autoimmune diseases including dilative cardiomyopathy and refractory systemic lupus erythematosus (SLE).
Dr. Scheibenbogen’s group has conducted two studies of immunoadsorption in ME/CFS. In one, a 5-day procedure led to rapid symptom improvement in 7 of 10 patients, with sustained improvement in 3 patients after 2 years. Autoantibodies decreased rapidly in 9 of the 10 patients. In a follow-up study of five of the responders 2 years later, retreatment with a modified immunoadsorption protocol led to rapid and sustained improvement in four. Further study has been on hold because of the pandemic.
Next-gen IgG-targeting therapies: Another approach that could offer promise for ME/CFS involves therapies that block the Fc receptors of IgG. Several are in phase 1-3 trials for autoimmune conditions. One candidate drug, the Fc fragment efgartigimod, is currently in phase 3 trials for several conditions, including generalized myasthenia gravis, primary immune thrombocytopenia, and chronic inflammatory demyelinating polyneuropathy. Phase 3 trials are planned for the monoclonal antibody rozanolixizumab in those same conditions.
Newer-generation monoclonal antibodies targeting CD19 or CD20 that show benefit in various autoimmune conditions are another possibility for ME/CFS. These include ocrelizumab (Ocrevus), approved in the United States for treating relapsing and progressive multiple sclerosis and in trials for SLE; obinutuzumab (Gazyva), approved for treating lymphoma and also in development for SLE; and ublituximab, in phase 3 trials for multiple sclerosis.
“Most of them are more effective than rituximab,” Dr. Scheibenbogen noted, adding that “currently the data look quite promising. They are effective in different autoimmune diseases and they are quite well tolerated. There’s great hope now with COVID-19 that we can convince some companies to do such trials in ME/CFS as well.”
Dr. Scheibenbogen’s institution, the Charité Fatigue Center, has a patent for beta2-adrenergic receptor antibodies for diagnosing ME/CFS under her name together with Celltrend. Dr. Komaroff has received personal fees from Serimmune.