Cyclophosphamide improves engraftment in patients with SCD and severe organ damage who undergo haploidentical PBSCT

The prevalence of pulmonary hypertension in adults with sickle cell disease, the mechanism of its development, and its prospective prognostic significance are unknown. We performed Doppler echocardiographic assessments of pulmonary-artery systolic pressure in 195 consecutive patients (82 men and 113 women; mean [+/-SD] age, 36+/-12 years). Pulmonary hypertension was prospectively defined as a tricuspid regurgitant jet velocity of at least 2.5 m per second. Patients were followed for a mean of 18 months, and data were censored at the time of death or loss to follow-up. Doppler-defined pulmonary hypertension occurred in 32 percent of patients. Multiple logistic-regression analysis, with the use of the dichotomous variable of a tricuspid regurgitant jet velocity of less than 2.5 m per second or 2.5 m per second or more, identified a self-reported history of cardiovascular or renal complications, increased systolic blood pressure, high lactate dehydrogenase levels (a marker of hemolysis), high levels of alkaline phosphatase, and low transferrin levels as significant independent correlates of pulmonary hypertension. The fetal hemoglobin level, white-cell count, and platelet count and the use of hydroxyurea therapy were unrelated to pulmonary hypertension. A tricuspid regurgitant jet velocity of at least 2.5 m per second, as compared with a velocity of less than 2.5 m per second, was strongly associated with an increased risk of death (rate ratio, 10.1; 95 percent confidence interval, 2.2 to 47.0; P<0.001) and remained so after adjustment for other possible risk factors in a proportional-hazards regression model. Pulmonary hypertension, diagnosed by Doppler echocardiography, is common in adults with sickle cell disease. It appears to be a complication of chronic hemolysis, is resistant to hydroxyurea therapy, and confers a high risk of death. Therapeutic trials targeting this population of patients are indicated. Copyright 2004 Massachusetts Medical Society

High-dose, posttransplantation cyclophosphamide (PTCy) is an effective strategy for preventing graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (alloBMT). However, the mechanisms by which PTCy modulates alloimmune responses are not well understood. We studied early T cell reconstitution in patients undergoing alloBMT with PTCy and the effects of mafosfamide, a cyclophosphamide (Cy) analog, on CD4(+) T cells in allogeneic mixed lymphocyte reactions (MLRs) in vitro. Patients exhibited reductions in naïve, potentially alloreactive conventional CD4(+) T cells with relative preservation of memory CD4(+)Foxp3(+) T cells. In particular, CD4(+)CD45RA(-)Foxp3(+hi) effector regulatory T cells (Tregs) recovered rapidly after alloBMT and, unexpectedly, were present at higher levels in patients with GVHD. CD4(+)Foxp3(+) T cells from patients and from allogeneic MLRs expressed relatively high levels of aldehyde dehydrogenase (ALDH), the major in vivo mechanism of Cy resistance. Treatment of MLR cultures with the ALDH inhibitor diethylaminobenzaldehyde reduced the activation and proliferation of CD4(+) T cells and sensitized Tregs to mafosfamide. Finally, removing Tregs from peripheral blood lymphocyte grafts obviated PTCy's GVHD-protective effect in a xenogeneic transplant model. Together, these findings suggest that Treg resistance to Cy through expression of ALDH may contribute to the clinical activity of PTCy in preventing GVHD.

Allogeneic marrow transplantation can cure sickle cell disease; however, HLA-matched donors are difficult to find, and the toxicities of myeloablative conditioning are prohibitive for most adults with this disease. We developed a nonmyeloablative bone marrow transplantation platform using related, including HLA-haploidentical, donors for patients with sickle cell disease. The regimen consisted of antithymocyte globulin, fludarabine, cyclophosphamide, and total body irradiation, and graft-versus-host disease prophylaxis with posttransplantation high-dose cyclophosphamide, mycophenolate mofetil, and tacrolimus or sirolimus. After screening 19 patients, we transplanted 17, 14 from HLA-haploidentical and 3 from HLA-matched related donors. Eleven patients engrafted durably. With a median follow-up of 711 days (minimal follow up 224 days), 10 patients are asymptomatic, and 6 patients are off immunosupression. Only 1 patient developed skin-only acute graft-versus-host disease that resolved without any therapy; no mortality was seen. Nonmyeloablative conditioning with posttransplantation high-dose cyclophosphamide expands the donor pool, making marrow transplantation feasible for most patients with sickle cell disease, and is associated with a low risk of complications, even with haploidentical related donors. Graft failure, 43% in haploidentical pairs, remains a major obstacle but may be acceptable in a fraction of patients if the majority can be cured without serious toxicities.