A Pilot Study of Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) in Generalized Myasthenia Gravis

Inclusion Criteria: * Must be between 18 and 80 years of age * Established diagnosis of myasthenia based on: the presence of fatigable weakness of ocular, oropharyngeal, and/or limb muscles AND the presence of abnormal acetylcholine receptor binding antibodies ≥ 0.4 nmol/l. * Patients of childbearing potential must agree to use a medically acceptable form of contraception defined by consistent use of oral contraceptive medications or history of tubal ligation or men who are in sexual relationship with such women during and for at least 8 weeks following completion of the study. * Patient or designee must have the ability to self-inject investigational product * If thymectomized, the procedure must have been performed at least one year prior to screening. * Dose of current anticholinesterase drugs must be constant for 2 weeks prior to screening. * If taking prednisone, dose must be stable for ≥4 weeks prior to screening. Exclusion criteria: * exclusively ocular MG (MGFA Class I) * severe respiratory and/ or swallowing muscle weakness (MGFA Class Vb or V) * presence of thymoma * Must not have received plasm exchange or IVIG within 4 weeks of screening * Must not have received immuno-modulating agents within the 4 weeks of screening, including Azathioprine (Imuran), Cyclosporine (Sandimmune, Neoral), Mycophenolate mofetil (CellCept), GM-CSF (Filgrastim; Neupogen; pegfilgrastim, sargramostim), or any other chronic immunosuppressive agent * History of tuberculosis or evidence of latent tuberculosis (positive PPD skin test or a chest X-ray with evidence of tuberculosis) * vital capacity of less than 1.2 liters or on supplemental oxygen therapy. * severe comorbidities including lung disease, stroke, congestive heart failure of any severity, myocardial infarction, EKG abnormalities, uncontrolled hypertension - (sitting systolic BP \<80 or \> 160 mm Hg or diastolic BP \> 100 mm Hg, unstable angina pectoris, hepatic or renal disease, insulin-dependent diabetes mellitus, history of cancer (other than in-situ cervical cancer or resected, cutaneous basal cell or squamous cell carcinoma), open cutaneous ulcers, known hepatitis B surface antigen (HbsAg) or hepatitis C virus (HCV) positive, or any other concurrent medical condition, which would make it unsafe for subjects to participate in the trial or interfere with the interpretation of the results. * Laboratories values which, at the time of the screening visit or at any time during the study that in the opinion of the Investigator would preclude participation in the study including: serum creatinine \> 2.5 mg/dL, serum potassium \< 3.5 mmol/L or \> 5.5 mmol/L, serum aspartate transaminase (AST), alanine transaminase (ALT), or alkaline phosphatase (ALP)\> 3 times the upper limit of normal, platelet count \< 100,000/mm3, WBC count \< 3,000 cells/mm3, Hemoglobin, hematocrit, or red blood cell count outside 30% of the upper or lower limits of normal * Receipt of a live vaccine within 3 months of screening * participation in another investigational drug study within 90 days of screening. * known hypersensitivity to GM-CSF or any of its components * Known HIV-positive status or known history of any other immuno-suppressing disease. * Any mycobacterial disease. * Active severe infections within 4 weeks before screening visit, or between the screening and baseline visits. * Untreated Lyme disease. * History of TB or TB exposure, chronic hepatitis B or hepatitis C, SLE, history of multiple sclerosis, transverse myelitis, optic neuritis or epilepsy. * History of recent alcohol or substance abuse (\< 1 year) * Pregnant or lactating females * History of non-compliance with other therapies * abnormal mental status sufficient to exclude informed consent * History of any opportunistic infection - to include but not limited to Pneumocystis carinii, aspergillosis, histoplasmosis, or atypical mycobacterium * History of Sickle cell disease.