The AURORA Study is evaluating the safety, tolerability, and efficacy of an investigational mRNA CAR T-cell therapy known as Descartes-08 in adults with acetylcholine receptor autoantibody -positive generalized myasthenia gravis. Part 1 of the study will last around 6 months. For eligible participants, Part 2 will last around 8 months.

Inclusion Criteria:

• Patient must be at least 18 years of age.
• Patient must have generalized myasthenia gravis (gMG), Myasthenia Gravis Foundation of America (MGFA) clinical classification grades 2-4 at the time of Sscreening.
• MG-Activities of Daily Living (MG ADL) total score ≥ 6.
• Concomitant immunosuppressive drugs must be deemed necessary by the investigator. The dose must be stable for a minimum of 8 weeks prior to Baseline visit.
• If a patient is using corticosteroids, the daily dose should not exceed 40 mg/day of prednisone equivalent. The dose must have been stable for a minimum of 8 weeks prior to Baseline visit.
• Acetylcholine receptor autoantibody (anti-nAChR) titer or anti-AChR cluster antibody must be above the reference laboratory upper normal limit (UNL) and documented within the past 10 years of screening.
• Patient must be willing to return for all study visits.
• Patient must be able to give written informed consent.
• Women of childbearing potential must agree to use highly effective birth control from Screening until 14 days post last dose of Descartes-08,

Exclusion Criteria:

• Major chronic illness that is not well managed at the time of study entry and in the opinion of the investigator may increase the risk to the patient.
• Diagnosis of gMG within 12 months of screening.
• No history of systemic treatment for gMG other than acetylcholine esterase inhibitors.
• Diagnosis of a neuromuscular disease other than gMG.
• Patient is pregnant or lactating.
• Treatment with intravenous immunoglobulin (IVIG) or plasma exchange within 4 weeks prior to the Baseline visit.
• Treatment with rituximab or ocrelizumab within 12 months prior to Baseline visit; treatment with calcineurin inhibitors (e.g. tacrolimus, cyclosporine, cyclophosphamide), Neonatal Fc receptor antagonists, and/or other biologics within 3 weeks prior to planned leukapheresis and within 8 weeks prior to Baseline visit.
• The patient has started treatment with a complement 5a (C5a) inhibitor, such as eculizumab, within 8 weeks of Baseline visit. (NOTE: patients who have been receiving a C5a inhibitor for more than 8 weeks and meet other criteria for enrollment are eligible for treatment).
• Prior treatment with B-cell maturation antigen (BCMA)-directed therapy (e.g. monoclonal antibody, T-cell engager, or chimeric antigen receptor T-cell [CAR-T]).
• Abnormal prothrombin (PT)/international normalized ratio (INR) or partial thromboplastin time (PTT) increased > 1.5-fold above the normal range at Screening or patient is on anticoagulation therapy (except in cases of elevated PTT with documented lupus anticoagulant; or in patients who have been on stable doses of anticoagulation therapy for more than 6 months of venous thromboembolism (VTE) diagnosis; or in patients on stable doses of anticoagulation therapy for at least 8 weeks of atrial fibrillation diagnosis; these conditions will not be exclusionary unless, in the investigator's opinion, they make participation in the study unsafe).
• Absolute neutrophil count (ANC) < 1000 cells/microliter.
• Hemoglobin < 8.0 g/dL.
• Platelets < 50,000/mm3.
• Alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) > 3x above normal.
• Creatine clearance less than 30 mL/min.
• History of primary immunodeficiency, organ, or allogeneic bone marrow transplant.
• Patients must be seronegative for hepatitis B surface antigen.
• Patients must be seronegative for hepatitis C antibody. If hepatitis C antibody test is positive, then patients must be tested for the presence of viremia by reverse transcriptase polymerase chain reaction (RT-PCR) and must be hepatitis C virus (HCV) ribonucleic acid (RNA) negative.
• History of positive human immunodeficiency virus (HIV) or positive HIV at screening.
• Active tuberculosis or positive QuantiFERON test at screening.
• Any other clinical or laboratory abnormality that, in the opinion of the investigator, may jeopardize the subject's ability to participate in the study or could affect study outcome.
• Any active significant cardiac or pulmonary disease that, in the opinion of the Principal Investigator, is significant and/or uncontrolled.

Note: Patients with asthma and chronic obstructive pulmonary disease (COPD) controlled with inhaled medications are allowed.

• History of malignancy that required treatment in the past 3 years, except for squamous cell carcinoma, basal cell carcinoma of the skin, or breast or early-stage colon cancer that is surgically removed and did not require adjuvant chemotherapy or radiotherapy.
• Treatment with any investigational agent 4 weeks prior to screening or 5 half-lives of the investigational drug (whichever is longer).
• Receipt of a live vaccination within 4 weeks prior to Baseline visit or intent to receive live vaccination during the study (Note: messenger RNA [mRNA]-based vaccines such as those against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not considered live; likewise, the Janssen Covid-19 vaccine is not live).
• History of significant recurrent infections or any active infection that in the opinion of the Investigator may interfere with the patient's participation in the opinion of the investigator.
• Any known psychiatric illness that in the opinion of the Investigator, may interfere with the patient's participation in the study in the opinion of the investigator.

first part of the study is double blinided and the second part of the study is open label