HEFEI, China – A drug originally developed to treat myasthenia gravis has shown striking benefits in a patient with a rare and often debilitating neurological condition, offering new hope for people with limited treatment options. Doctors at Huashan Hospital have reported the first known case of successful treatment of Lambert-Eaton myasthenic syndrome (LEMS) using efgartigimod, a targeted immune therapy currently approved for myasthenia gravis. Their findings suggest the drug may represent a fast-acting, safer alternative for critically ill LEMS patients—particularly those with cancer.
Understanding Lambert-Eaton Myasthenic Syndrome
LEMS is an autoimmune disorder in which antibodies attack calcium channels at the nerve–muscle junction, preventing proper release of acetylcholine and causing profound muscle weakness. About half of all patients develop LEMS as a paraneoplastic syndrome, most commonly associated with small cell lung cancer. Patients often experience difficulty walking, speaking, chewing, and breathing. Standard treatment focuses first on controlling the underlying cancer, alongside drugs that boost nerve signaling or broadly suppress the immune system. However, many of these therapies act slowly or carry significant side effects.
The Patient’s Rapid Decline
The patient described in the report was a 73-year-old man who had been treated with chemotherapy for small cell lung cancer for two years. In mid-2024, he rapidly developed classic LEMS symptoms: drooping eyelids, slurred speech, severe swallowing difficulty, inability to lift his head, and progressive weakness that left him bedridden. Blood tests revealed very high levels of voltage-gated calcium channel antibodies and positive SOX-1 antibodies, confirming the diagnosis. Electrical nerve testing showed the characteristic pattern of LEMS.
Failure of Standard Therapy and Escalating Risk
Doctors initially treated him with high-dose corticosteroids and pyridostigmine, a standard symptomatic therapy. Instead of improving, his condition worsened. He developed severe breathing difficulty and further limb weakness—dangerous signs that he was approaching a life-threatening neuromuscular crisis. Complicating matters, ultrasound revealed deep venous thrombosis in his leg, making traditional emergency treatments such as plasma exchange or intravenous immunoglobulin risky because of their association with blood clots.
A Targeted Immune Strategy
At this critical point, the medical team turned to an off-label option: efgartigimod. The drug works by targeting the neonatal Fc receptor, which normally protects IgG antibodies from being broken down. By blocking this receptor, the drug accelerates the removal of harmful autoantibodies from the bloodstream without broadly suppressing the immune system. The medication is marketed under the brand name Vyvgart and is approved in multiple countries for antibody-positive myasthenia gravis.
Rapid and Dramatic Clinical Improvement
The patient received weekly infusions of efgartigimod at a dose of 10 mg/kg. After just one dose, his condition began to improve. Within a week, he could sit up on his own, eat independently, brush his teeth, and lift his legs off the bed—abilities he had completely lost. After four weekly treatments, his daily living disability score dropped from 11 to 1, objective strength measurements fell into the mild range, total IgG levels dropped by more than half, and pathogenic VGCC antibodies fell from 162 pmol/L to just 5.57 pmol/L, essentially returning to normal. Other immune proteins such as IgA and IgM remained stable, confirming the drug’s selective effect. The patient experienced no reported side effects.
Unexpected Death After Apparent Recovery
One month after his final dose, he was living independently with minimal limitations. Tragically, more than a month later, he died suddenly at home following acute chest and back pain. Given his known deep venous thrombosis and the nature of his symptoms, doctors suspect a pulmonary embolism or sudden cardiac event as the likely cause. There is currently no evidence linking efgartigimod to sudden death, and the drug would have been fully cleared from his body within two weeks of the final dose.
Why This Case Is Scientifically Important
This report represents the first documented use of efgartigimod in LEMS, a rare disease with few rapid-acting treatment options—especially in patients with cancer or blood-clot risk. Compared with plasma exchange or IVIG, FcRn inhibitors offer several advantages, including faster onset of action, selective removal of disease-causing IgG, lower risk of serious complications such as kidney failure or thrombosis, and outpatient administration.
Limitations and Future Directions
The authors emphasize that this is a single-patient case report rather than a clinical trial. Many questions remain, including the safety of long-term use in cancer patients, potential effects on tumor growth, and whether the drug’s benefits are sustained with repeated cycles. Despite these uncertainties, the dramatic clinical and laboratory response strongly suggests that FcRn inhibition could become a powerful new strategy for antibody-mediated neuromuscular diseases beyond myasthenia gravis.
Implications for Patients and Clinicians
Clinicians now hope this case will prompt formal clinical studies of efgartigimod in larger groups of LEMS patients. If confirmed, the approach could reshape emergency and long-term management of this rare but devastating condition—particularly for patients who cannot safely undergo plasma exchange or IVIG.
Contacts
Yue Zhang
Email [email protected]
or
Jie Wei
Email [email protected]