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

Prior treatment

• Other uncontrolled disease states, such as asthma, or inflammatory bowel disease, where flares are commonly treated with oral or parenteral corticosteroids, at screening
• Prior treatment with anti-CD19 therapy, adoptive T cell therapy or any prior gene therapy product (e.g. CAR-T cell therapy).
  • Other protocol-defined inclusion/exclusion criteria may apply

Other illness

• Exclusively ocular myasthenia gravis (MGFA I), mild symptoms (MGFA II), or severe bulbar disease or MG crisis, MGFA Class IVb or V at screening
• History of bone marrow/hematopoietic stem cell or solid organ transplantation.
• Participants with a known immunodeficiency syndrome (AIDS, hereditary immune deficiency, drug induced immune deficiency), or tested positive for HIV antibody, at screening

Lab values

• 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

• 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
• MGFA Class III-IVa (gMG) at screening
• Treatment-resistant gMG as defined by: MG-ADL score ≥ 6 (≥50% non-ocular) at screening despite adequate treatment trials with at least two different non-steroidal immunosuppressive drugs given at adequate doses and duration of therapy.
• If on chronic corticosteroids, must be on a stable dose of corticosteroids for ≥1 month prior to screening and have the ability and willingness to taper to a maximum dose of 10 mg prednisolone daily or equivalent at least one week before leukapheresis
• If treated with cholinesterase inhibitors, patients must be on a stable dose for at least two weeks prior to screening