The whys and hows of rituximab in thyroid eye disease

Bronx, NY-Treatment of thyroid eye disease varies greatly among physicians.

“Immunobiologic agents are used early in patients with thyroid eye disease,” said Simeon Lauer, MD, clinical associate professor, Albert Einstein College of Medicine, Bronx, NY. “In most cases when an immunologic agent is thought to be needed, it is not. These drugs must be used in the context of individual physicians’ multimodality therapy.”

The goal of treatment, Dr. Lauer said, is to limit disease progression and reverse its effects.

“Rituximab is a non-specific treatment that causes B-cell depletion,” he said. “Its use in thyroid eye disease is off-label, but it is available to patients who need it in very selected cases.”

The chimeric monoclonal antibody targets the CD20 antigen on an ion channel specific to mature B-lymphocytes. Rituximab causes systemic depletion of those mature B-lymphocytes within 3 to 4 weeks of treatment.

The effect lasts 9 to 12 months, and after that time, lymphocyte levels and function return to normal.

Rituximab is used as part of the initial medical therapy to limit disease progression by controlling severe inflammation as well, Dr. Lauer said.

“The drug also facilitates decompression and other surgeries by limiting secondary inflammation and smoothing the postoperative course,” he said. “Physicians cannot wait until the medical and surgical regimens have failed before beginning treatment with rituximab-that is too late.”

Dr. Lauer underscored the need for highly selective use of rituximab as well.

In cases with severe inflammation that may need an immunobiologic, he said, the disease can improve spontaneously, while the inflammation resolves and the disease becomes self-limiting.

“Our patients are very anxious and may push for prescription of rituximab,” Dr. Lauer said. “Try to avoid the full sense of urgency created by the thyroid eye disease personality.”

When and how physicians use rituximab depends on when and how other treatments are used, he said.

Endoscopic orbital decompression can limit tissue manipulation, he said, so physicians need to determine how rituximab fits into their style of treating thyroid eye disease.

“While it is not FDA approved, sufficient evidence supports its safety and efficacy,” Dr. Lauer said.

Psychosocial support, he said, is the most important intervention.

 “The body cannot produce the inflammatory clinical signs of redness and swelling when it has been depleted of B-lymphocytes (caused by rituximab),” Dr. Lauer said. “Rituximab does not reduce proptosis-which is irreversible-and it does not affect the restrictive myopathy, which is accomplished surgically.”

The drug suppresses the inflammation without substantial immunosuppression and can produce a minor predisposition to infections, such as flu and upper respiratory infection.

Rituximab has an excellent safety profile with one important exception, he said: The agent can cause a rare degenerative neurologic condition (i.e., progressive multifocal leukoencephalopathy) that is primarily a risk in patients with lymphoma and severe autoimmune diseases when four or more infusions are needed, but can develop with fewer infusions.

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