Study to Assess Safety, Efficacy, and Cellular Kinetics of YTB323 in Generalized Myasthenia Gravis

Eligibility Criteria

• 1. Confirmed gMG diagnosis supported by the following:
• * Documented report of positive serology testing for either AChR antibodies or MuSK antibodies at screening AND at least one of the following:
• * History of abnormal neuromuscular transmission test demonstrated by repetitive nerve stimulation or single-fiber electromyography
• * History of positive acetylcholinesterase inhibitor test
• * Improvement in MG signs on an oral acetylcholinesterase inhibitor as assessed by the treating physician
• 2. MGFA Class III-IVa (gMG) at screening
• 3. Treatment-resistant gMG as defined by: MG-ADL score ≥ 6 at screening despite adequate treatment trials with at least two different non-steroidal immunosuppressive drugs given at adequate doses and duration of therapy.
• 4. If on chronic corticosteroids, the ability and willingness to taper to a maximum dose of 10 mg prednisolone daily or equivalent at least one week before leukapheresis
• 5. If treated with cholinesterase inhibitors, patients must be on a stable dose for at least two weeks prior to screening
• 1. Exclusively ocular myasthenia gravis (MGFA I), mild symptoms (MGFA II), or severe bulbar disease or MG crisis, MGFA Class IVb or V at screening
• 2. History of bone marrow/hematopoietic stem cell or solid organ transplantation.
• 3. Clinically significant active, opportunistic, chronic or recurrent infection (including positive for hepatitis B or hepatitis C) confirmed by clinical evidence, imaging, or positive laboratory tests one month prior to leukapheresis
• 4. Other uncontrolled disease states, such as asthma, or inflammatory bowel disease, where flares are commonly treated with oral or parenteral corticosteroids, at screening
• 5. Participants with a known immunodeficiency syndrome (AIDS, hereditary immune deficiency, drug induced immune deficiency), or tested positive for HIV antibody, at screening
• 6. Prior treatment with anti-CD19 therapy, adoptive T cell therapy or any prior gene therapy product (e.g. CAR-T cell therapy).