An experimental drug that can halt a rare and sometimes paralyzing nerve disease with a single infusion is moving closer to becoming the first approved treatment of its kind, according to a new report published by its maker, Annexon Biosciences. The drug, tanruprubart, is designed to target Guillain-Barré syndrome (GBS), a disease in which the body's immune system mistakenly attacks the nerves. There is currently no FDA-approved treatment for the condition anywhere in the world, despite at least 150,000 people being affected by it per year.
"These compelling clinical results depict how a rapid gain in muscle strength can lead to a better state of health with a single infusion of tanruprubart in a real world setting," Henk-André Kroon, M.D., senior vice president of Translational Medicine at Annexon, said in a 2025 statement after announcing improved clinical outcomes. "As the potential first targeted immunotherapy in GBS, we are eager to move tanruprubart forward for patients in need." GBS leads to more than 22,000 hospitalizations annually in the U.S. and Europe alone, according to Annexon. The rare autoimmune disease typically starts with weakness or tingling in the hands and feet, which can spread quickly and, in severe cases, cause complete paralysis requiring intensive care and mechanical ventilation.
Most patients recover over months or years, though some are left with lasting weakness, numbness or fatigue, and the disease can be fatal. Tanruprubart works by blocking C1q, a molecule that triggers the immune attack on nerve cells. Given as a single intravenous infusion, it is designed to stop the nerve damage in its early stages, allowing patients to regain strength and independence faster than with current treatments.
New data show the drug's effects appear quickly and last. However, these results have yet to be peer-reviewed. A real-world study matched patients who received tanruprubart in Annexon's Phase 3 trial against patients treated with the current standard of care—intravenous immunoglobulin or plasma exchange—drawn largely from Western countries in the International GBS Outcomes Study registry.
By the first week of treatment, tanruprubart patients showed roughly a 10-point improvement in muscle strength over those on standard treatments, measured on the Medical Research Council sumscore. Patients given tanruprubart were also about three times more likely to be in a better state of health at four, eight and 26 weeks, based on the GBS-Disability Scale. Separate Phase 3 trial data showed benefits emerging within a week of a single 30 mg/kg dose, including improvements in strength, mobility, balance and coordination that held up through 26 weeks.
Patients regained the ability to move independently, handle personal tasks and return to daily routines more quickly than those on standard care. Shernell Surratt-Gary, clinical adviser of Aura Wellness in Kentucky, spoke with Newsweek about Annexon's ambitions. "I believe the clinically relevant result of this research isn’t just that there was an improvement in the clinical status of the patients, but when that improvement appeared," Surratt-Gary said.
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