Hematopoietic Stem Cell Therapy for Patients With Refractory Myasthenia Gravis

Overview

MG may be neonatal, congenital, or autoimmune. Neonatal MG arises from transplacental transfer of ACh receptor antibodies from a mother with autoimmune MG to the fetus. Neonatal MG resolves with post delivery clearance of maternal antibodies. Congenital MG results from a genetic defect in the ACh receptor. Patients with congenital MG do not have ACh receptor antibodies. Both neonatal and congenital MG are excluded from this study. Autoimmune MG, which is the most common form of MG, affects approximately 25,000 Americans. Like most autoimmune diseases, it is associated with particular HLA genotypes, has a female predominance, and environmental factors involved in breaking tolerance to the ACh receptor are unknown. Patients with refractory and severe autoimmune MG will be considered candidates for this study. The purpose of this study is to assess the toxicity/feasibility (phase I) of autologous hematopoietic stem cell transplantation for refractory myasthenia gravis.

There will be no randomization in this study. All subjects who are determined to be eligible for the study treatment will receive high dose cyclophosphamide and ATG followed by infusion of autologous peripheral blood stem cells. The procedures the subject will undergo are as follows: 1. Physician visit to determine potential eligibility for the study. Subjects will be evaluated by a transplant physician and a neurologist. They will have a complete physical examination and will provide a full medical history at these visits. The study will be described in detail by the transplant physician and nurse and the consent form will be provided to be taken home to read. 2. Insurance verification. Subjects who remain interested in pursuing the study treatment and who have refractory myasthenia gravis will proceed to the insurance verification phase. Third party payment or self-pay must be verified before subjects can proceed. 3. Consent form. Prior to proceeding, the appropriate signatures will be obtained on the consent form. Subjects will be given an opportunity to ask further questions of the attending physician and transplant nurse prior to signing the consent form. 4. Pre-transplant testing. To determine final eligibility for the study, subjects will undergo a series of tests/procedures. These include: CXR; electrocardiogram; MUGA or echocardiogram; pulmonary function test; CT scan of the sinuses; CT scan of the chest to r/o thymoma; dental examination; urinalysis; and blood testing to include CBC, chemistries, liver and kidney function tests, coagulation studies, viral studies and, for females, a pregnancy test. All pre-transplant testing is routine medical testing done to verify diagnosis and to insure adequate organ function and absence of viral illnesses which would preclude a safe transplant course. 5. Autologous peripheral blood stem cell collection. Subjects who are proceeding to transplant will undergo a routine procedure for the mobilization and collection of peripheral blood stem cells. This includes the administration of IV cyclophosphamide, given as an inpatient requiring an overnight stay, followed by the subcutaneous administration of G-CSF, to be self-administered as an outpatient. Approximately ten days after the administration of IV cyclophosphamide, the peripheral blood stem cells will be collected as an outpatient in the Blood Center. A pheresis catheter will be placed for this purpose on the first day of leukopheresis. Leukopheresis will be continued on a daily basis until an adequate number of peripheral blood stem cells have been collected (a maximum of four leukophereses may be performed). G-CSF will continue to be administered until leukopheresis is completed. The pheresis catheter will be discontinued when stem cell harvesting is completed. Processed cells will be frozen and stored until they are reinfused after the conditioning regimen. 6. PICC line placement. Subjects will have a double lumen PICC line placed prior to the administration of study treatment for the administration of chemotherapy, IV fluids, blood products and the withdrawal of blood samples. The placement of a PICC line is a routine medical procedure. 7. Study treatment. Subjects will undergo conditioning which will include four days of intravenous high dose cyclophosphamide and three days of intravenous anti-thymocyte globulin (ATG). Both cyclophosphamide and ATG are common immune suppressive agents. The previously collected peripheral blood stem cells will be reinfused following the completion of the conditioning regimen. 8. Post-treatment follow-up. Subjects will have a history and physical by the transplant physician and neurologist at 3 months, 6 months, 12 months, and yearly for 5 years. In addition, routine urinalysis and blood testing will be performed at these same intervals to include CBC, chemistries, kidney and liver function tests.