This is an open label, single arm study, to evaluate the safety , tolerability and preliminary efficacy of HN2302 for refractory myasthenia gravis.

The study will consist of an up to 4-week Screening Period, Treatment Period and one year Follow-up Period.

Inclusion Criteria:

• Age: 18-80 years, no gender restriction;
• Confirmed diagnosis of generalized myasthenia gravis (MG) with positive AchR or MuSK antibodies, meeting at least one of the following conditions：(1) Repetitive nerve stimulation suggesting neuromuscular transmission defect; (2) Positive response to neostigmine test; (3) Clinically judged improvement of --MG symptoms after oral cholinesterase inhibitor therapy;
• Clinical classification of MG according to MGFA types IIa-IVb (including IIa, IIb, IIIa, IIIb, IVa, IVb);
• Baseline MG-ADL score ≥6, ocular-related score <50%;
• Poor response and/or lack of efficacy under standard therapies;
• Minimum life expectancy > 12 weeks;
• Adequate bone marrow, coagulation, cardiopulmonary, liver, and renal function.

Exclusion Criteria:

• Subjects positive for hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb) with detectable or quantifiable HBV DNA, positive for hepatitis C antibody (HCV Ab) with detectable or quantifiable HCV RNA, positive for HIV antibody, positive CMV DNA, or CMV DNA above the lower limit of detection; positive for syphilis antigen or antibody;
• Presence of other uncontrolled active infections;
• History of major organ transplantation (e.g., heart, lung, liver, kidney) or bone marrow/hematopoietic stem cell transplantation;
• Pregnant or breastfeeding women;
• Receipt of any mRNA-LNP products or other LNP-based drugs within the past two years;
• History of any of the following cardiovascular conditions within 6 months prior to screening: New York Heart Association (NYHA) Class III or IV heart failure, myocardial infarction, unstable angina, uncontrolled or symptomatic atrial arrhythmias, any ventricular arrhythmias, or other clinically significant cardiac disease;
• History of ≥Grade 2 bleeding events within 30 days prior to screening, or requiring long-term continuous anticoagulation therapy (e.g., warfarin, low molecular weight heparin, Xa factor inhibitors);
• History of live vaccination within 30 days prior to screening;
• Severe central nervous system diseases or pathological changes, including but not limited to: cerebrovascular accident, aneurysm, epilepsy, seizures/convulsions, aphasia, stroke, severe brain injury, dementia, Parkinson's disease, cerebellar disorders, organic brain syndromes, or psychosis;
• History of asthma or severe allergies;
• Any condition that, in the investigator's opinion, may increase the patient's risk or interfere with study assessments.