NCMP-02. MYASTHENIA GRAVIS INDUCED BY AVELUMAB

Abstract

Abstract Monoclonal antibodies targeting PD- 1 (nivolumab and pembrolizumab) and PD-L1 (avelumab, atezolizumab, and durvalumab) are FDA approved for the treatment of metastatic cancers. Immune-related adverse events (irAEs) are autoimmune diseases which occur following treatment with PD-1 and PD-L1 inhibitors. Neurological irAEs following PD-L1 blockade are rarely reported, and mainly consist of Myasthenia Gravis (MG) and myositis. MG induced by avelumab has not been previously reported. We present a 74-year-old female with stage IV ovarian adenocarcinoma who entered a clinical trial involving avelumab and entinostat after disease progression following extensive resection, chemotherapy with doxorubicin, then docetaxol and cisplatin. She developed progressive generalized weakness and fatigue two months after entering the trial, leading to respiratory weakness and hypoventilation, and resulting in intubation and mechanical ventilation. Exam showed head-drop, diplopia, and proximal > distal upper and lower limb weakness. Antibodies to acetylcholine receptors, muscle specific tyrosine kinase, and voltage-gated calcium channels (P/Q and N type) were negative, and serum creatine kinase was normal. Repetitive nerve stimulation showed significant decrement in the left spinal accessory nerve motor response with recording at trapezius. She was diagnosed with seronegative MG and was treated with IVIG, 2 grams/kg divided over 4 days, prednisone 60 mg daily, and pyridostigmine, which resulted in successful extubation, followed by gradual resolution of MG symptoms over a period of 3 months. At approximately 2 year follow-up, she remains on maintenance IVIG at 0.5 grams/kg every 3 weeks, as she develops proximal lower limb and neck extension weakness at the end of each IVIG cycle. We conclude that MG is a potentially life threatening but treatable irAE associated with avelumab. Our case also adds to the accumulating literature of the role of PD-1 signaling in the pathogenesis of autoimmune diseases of the muscles and neuromuscular junctions.