Rituximab, a medication used for certain cancers and autoimmune disorders, appeared effective for a subset of patients with chronic inflammatory demyelinating polyneuropathy (CIDP) who were refractory to first-line immunotherapies.
Outcome measures, including muscle strength, disability scores and functional status, improved in some of the patients over the course of the retrospective study. The results from this small clinical case series was published in the January 10 online issue of Muscle and Nerve.
There are no published data from placebo-controlled trials testing rituximab in patients with CIDP. B-cell depletion therapy with rituximab is used for the treatment of myasthenia gravis and some neurologists suspect that it could work at targeting nodal and paranodal autoantibodies that have been identified in CIDP patients.
The autoimmune disease targets the myelin sheath but most patients also develop secondary axonal degeneration. Early and effective treatment can prevent further disability. Some patients don't respond to the immunotherapies now offered to patients, and neurologists are testing other strategies, including rituximab, cyclophosphamide, and bone marrow transplantation.
For this study, the investigators, led by Suray A. Muley, MD—of the neurology department of the Barrow Neurological Institute in Phoenix— identified 11 patients (eight women and three men) with CIDP who were getting progressively worse despite taking two or more immunotherapy drugs. These patients were seen at three different academic medical centers: the Barrow Neurological Institute in Arizona, University of Kansas Medical Center, and University of Minnesota.
The scientists had access to the medical records and all patients had a baseline Medical Research Council sum score (MRC) and an Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, before treatment with rituximab, and then again at least six months later. The protocols were different at each institute. There was an induction dose (two doses of 1 g rituximab delivered two weeks apart in most patients) followed in most cases by different maintenance doses—either 500 mg or 1 g and that was also given at different times, anywhere from three to six months after the first dose.
The duration of treatment with rituximab ranged from one to 72 months (with a median of 12 months): seven patients received treatments for less than a year, and four received only induction therapy.
The scientists analyzed "the time to first response, the time to maximal improvement, MRC and INCAT disability scores at maximal improvement, functional status at maximum improvement, and duration of treatment with rituximab."
Ten of 11 patients had significant weakness in both arms and legs at baseline. These were patients who had been sick anywhere from four months to 14 years.
They observed the first signs of improvement in the first one to three months: five patients were showing improvement within the first month; four between the first and second month, and two more improved by the third month. Most continued to improve over time. Nine patients reached their maximum improvement within six months, and the other two within 18 months. All of the primary outcome measures improved significantly in nine of 11 cases.
"Six of 11 patients were walking normally without assistance at maximal improvement, two of 11 patients were walking independently with ankle-foot orthoses, and the remaining three patients were walking with a cane or walker," the investigators reported. The medication was well tolerated without significant side effects.
The scientists said that a placebo-controlled trial to test the effectiveness of rituximab for CIDP patients is warranted. They noted that only three of the patients had antibody testing performed for nodal antibodies that had been identified in some CIDP patients, and that further studies should be done to see whether refractory patients who harbor specific antibodies would have a better treatment response to rituximab in comparison with antibody-negative cases. That was impossible to tell from this study.
"Given the robust response to rituximab in our patients, our findings support the suggestion that, at a minimum, rituximab is efficacious in a subset of patients with idiopathic CIDP," the study authors wrote.
The authors stated no conflicts of interest.
Link Up for More Information:
Muley SA, Jacobsen B, Parry G, et al. Rituximab in refractory chronic inflammatory demyelinating polyneuropathy. Muscle Nerve 2020; Epub 2020 Jan 10.