Istvan Redei

Pharmacokinetics and pharmacodynamics of anti-thymocyte globulin in recipients of partially HLA-matched blood hematopoietic progenitor cell transplantation

Polyclonal anti-thymocyte globulin (ATG) administered before allogeneic blood hematopoietic progenitor cell transplantation reduces the risks of graft rejection and graft-versus-host disease, but may delay posttransplant immune reconstitution caused by delayed clearance of ATG from the blood. We studied graft-versus-host disease, infections, and the kinetics of immune reconstitution in 28 patients with very poor-risk hematologic malignancies who received lymphocyte-depleted, CD34(+) cell-enriched hematopoietic progenitor cell grafts from partially HLA-matched related donors (PMRD). The incidence of these clinical events was correlated with blood ATG levels in 19 transplant recipients who received rabbit ATG (r-ATG, thymoglobulin) during conditioning. Total r-ATG and the fraction of ATG antibodies that bind human cells (active ATG) were measured for up to 45 days posttransplantation using enzyme-linked immunosorbent assay and flow cytometry assays. Three patients received equine ATG (e-ATG; total dose of 60 mg/kg/day), 3 patients received 10 mg/kg r-ATG, and 22 patients received 6 mg/kg r-ATG during conditioning. All evaluable patients engrafted. Median numbers of blood CD4(+) and CD8(+) T cells at 100 days posttransplantation were 15 and 8 cells/microL, respectively. Acute graft-versus-host disease developed in 3 of 3 recipients of e-ATG and 1 of 25 recipients of r-ATG. Rapid T-cell reconstitution was seen only in younger patients. Overall mortality was 93% (26/28 patients) with poor immune reconstitution contributing to death in 21 of 28 patients. Recipients of 6 mg/kg r-ATG had peak levels of total and active r-ATG of 64+/-20 microg/mL and 9.2+/-5.8 microg/mL, respectively, with clearance of active r-ATG (t(1/2)6 days) to sub-therapeutic levels (<1 microg/mL) by a median of 15 days posttransplantation (range, 8-38 days). Delayed immune reconstitution is likely a consequence of ex vivo and in vivo purging of donor T cells in the graft coupled with inadequate thymic function rather than persistence of active r-ATG in the blood for months posttransplantation.

Allogeneic bone marrow transplantation with matched unrelated donors for patients with hematologic malignancies using a preparative regimen of high-dose cyclophosphamide and fractionated total body irradiation

Allogeneic bone marrow transplantation (BMT) from an HLA-identical sibling donor is effective therapy for patients with bone marrow failure states and those with hematologic malignancies. However, only a minority of them will have an HLA-identical sibling donor; unrelated donors, matched or partially mismatched, have been used successfully for patients lacking a related donor. Even though results with allogeneic transplants using unrelated donors are encouraging, the incidence of complications including graft-versus-host disease (GVHD) and graft rejection or late graft failure is increased compared to identical sibling transplants. The combination of cyclophosphamide and total body irradiation (TBI) has been used as an effective preparative regimen for allogeneic transplants, however, the total dosage and dosing schedule of both the cyclophosphamide and TBI has varied significantly among studies. To decrease the rate of graft rejection and late graft failure with volunteer donors, we evaluated a preparative regimen of high-dose cyclophosphamide (200 mg/kg over 4 consecutive days, days −8, −7, −6, −5) followed by fractionated TBI (1400 cGy administered in eight fractions over 4 days, days −4, −3, −2, −1). GVHD prophylaxis included FK506 and methotrexate. From July 1993 to January 1996, 43 adult patients, median age 38 years (range 18–58 years), were treated with this preparative regimen. Seventeen patients had low-risk disease and 26 had high-risk disease. Thirty-one donor/recipient pairs were matched for HLA-A, -B, and -DR by serology and molecular typing. Seven additional pairs were minor mismatched at the HLA-A or HLA-B loci. Four other donor/recipient pairs were HLA-A,-B, and -DR identical by serology but allele mismatched at either DRB1 or DQB. Forty patients were evaluable for myeloid engraftment. Engraftment occurred in all 40 patients at a median of 19 days. There were no cases of graft rejection or late graft failure. Nephrotoxicity was the primary adverse event with 26 patients (60%) experiencing a doubling of their creatinine. Hepatic veno-occlusive disease occurred in seven patients, six of whom had high-risk disease. All patients who had relapsed or refractory disease prior to BMT achieved a complete remission following BMT. Six patients transplanted for high-risk disease relapsed a median of 377 days post-BMT. None of the patients with low-risk disease have relapsed following transplant; the Kaplan–Meier survival for those patients with low-risk disease is 62% and 37% for those patients transplanted with high-risk disease (P = 0.0129). The median Karnofsky performance status is 100% (range 70–100%). Therefore, a preparative regimen of high-dose cyclophosphamide and fractionated TBI is an acceptable regimen for patients receiving an allograft from unrelated donors.

Successful engraftment after primary graft failure in aplastic anemia using G-CSF mobilized peripheral stem cell transfusions

A 19-year-old male underwent allogeneic BMT for severe aplastic anaemia (SAA) from his HLA- and blood group-identical sister. He was conditioned with cyclophosphamide (CY) and single fraction total lymphoid irradiation (TLI). GVHD prophylaxis consisted of FK506 and a short course of methotrexate. The patient failed to achieve durable trilineage hematopoietic engraftment. There was no significant myeloid response to GM-CSF or G-CSF. Evaluation of FACS-sorted peripheral T cells from the patient by fluorescence in situ hybridization (FISH) revealed mixed chimerism (44% host origin). Fifty-three days after the first BMT, he was treated with G-CSF primed, unmanipulated PBSC transfusions (5.28 × 108/kg mononuclear, 4.28 × 106/kg CD34+, 292.51 × 106/kg CD3+ cells) from his original donor without reconditioning. FK506 was continued at the same dose. Neutrophil recovery to 0.5 × 109/l and platelet engraftment to 20 × 109/l was achieved 11 and 27 days following the first dose of allogeneic PBSC transfusion, respectively. On day 23 a repeat FISH on the patient’s sorted peripheral T lymphocytes revealed 91% donor origin T cells. The patient is currently well with a stable engraftment 6 months following allogeneic PBSC transfusion, with no signs of acute of chronic GVHD.

Rapid hematopoietic engraftment following fractionated TBI conditioning and transplantation with CD34 + enriched hematopoietic progenitor cells from partially mismatched related donors

Nineteen adult patients with poor-risk hematologic malignancy received T cell-depleted (TCD) hematopoietic progenitor cell (HPC) transplant from partially mismatched related donors (PMRD). The preparative regimen (FITFA) included fractionated TBI, thiotepa, fludarabine, and horse (n = 3) or rabbit (n = 16) anti-thymocyte anti-sera (ATG). GVHD prophylaxis consisted of TCD by positive/negative selection using the Isolex 300i system and pre-transplant ATG with no post-transplant immunosuppression. The mean number (±s.d.) of transplanted CD34+ and CD3+ cells were 8.9 × 106/kg ±4.3 (range 2.6–19.3) and 1.4 × 104/kg ±1.2 (range 0.3–4.6) respectively. Seventeen patients evaluable for neutrophil engraftment achieved an ANC >0.5 × 109/l at a median of 12 days (range 9–27), with evidence of full donor chimerism. Thirteen patients died of the following causes: relapse (n = 6), infections (n = 5), interstitial pneumonia (n = 1), and unknown causes (n = 1) None of the recipients of rabbit ATG required therapy for acute or chronic GVHD. Five patients are alive and disease-free at a median time of 303 days post transplant (range 100–660). The FITFA preparative regimen using fractionated TBI is well tolerated and is sufficiently immunosuppressive to allow rapid and stable donor origin hematopoietic engraftment without ‘mega’ doses of CD34+ cells. Combination of stringent ex vivo TCD and pre-transplant ATG is effective GVHD prophylaxis.