Reduced Intensity Conditioning Therapy Using Campath -1H Is Successful for Stem Cell Transplantation in Non-Malignant Disorders.

Stem cell transplantation (SCT), indicated for many non-malignant disorders, is limited by donor availability, graft rejection (GR), toxicities of conditioning, morbidity and mortality (TRM), and graft versus host disease (GVHD). To overcome these barriers, we tested a novel conditioning for SCT. It was designed to support engraftment by deleting host immune reactive lymphocytes and macrophages. Campath -1H (anti-CD52 mab) was given on days -21, -20, and -19 (total dose 48 mg), fludarabine (day -8 to -4) (total 150 mg/m²) and melphalan on day -3 (140 [n=15] or 70 [n=1] mg/m²). Stem cell sources were related/unrelated bone marrow (BM) (8), peripheral blood (PB) (5) and umbilical cord blood (UCB) (3). GVHD prophylaxis was cyclosporine (tapered after 3 months), methylprednisone (tapered after day +28) and methotrexate on days +1, +3, and +6. Methotrxate was not used in UCBT. End points of the study included engraftment and TRM. Sixteen patients (1.5–40 yrs) diagnosed with aplastic anemia (5), Hurler’s (2), sickle cell anemia, XLAAD, histiocytosis (3), thalassemia, adrenoleukodystrophy, Evan’s syndrome and dyserythropoietic anemia were transplanted. Median follow-up was 219 days (66–845). The regimen was well tolerated. All patients that survived >1 month engrafted. Neutrophils (ANC >500/dL) engrafted at a median of 12.5 (10–36) days and platelets (>50,000/dL) at a median of 21 (12 –63) days. Skin GVHD developed in 3 patients and resolved early. Four are tapering immune suppression; 8 are successfully off immune suppression. All survivors have either stable disease or are cured. One recipient had a normal pregnancy and delivered twins. Two patients died prior to engraftment from previously acquired Pseudomonas infection. A third patient died of CMV disease (day +112) and another recipient died of intracranial hemorrhage/refractory thrombocytopenia (day +43) after engraftment. Other complications were bacterial and viral infections occurring within the first 100 days post-transplant. All but 1 CMV+ recipient reactivated CMV as assessed by PCR. Profound lymphopenia was present in all recipients on day +30. NK cells recovered by day +100, CD8+ cells by day +180, CD4+ and B cells between days 180–270 after transplant. Immunoglobulin (Ig M and A) levels dropped post transplant and normalized by 9 months. Ig A recovered later than IgM. In summary, successful engraftment despite varied stem cell sources, was achieved without significant toxicity or GVHD. Lymphopenia resulted in a significant infection risk within the first 100 days post transplant, requiring close surveillance and early intervention. This transplant regimen is well tolerated and may preserve fertility, making it a promising alternative to conventional SCT.