A pilot study of nonmyeloablative allogeneic hematopoietic stem cell transplant for advanced systemic mastocytosis

Systemic mastocytosis (SM) is a disease characterized by tissue infiltration of neoplastic mast cells originating from hematopoietic stem cells. Patients with advanced SM have a poor prognosis, and there is no mast cell ablative therapy available for most patients who carry an activating point mutation in the c-kit gene. We report results of a prospective study evaluating the safety, engraftment, and possibility of inducing a graft-versus-mast cell (GvMC) effect after allogeneic nonmyeloablative hematopoietic cell transplantation (HCT) from an HLA-identical sibling. Three patients with advanced SM were transplanted. All achieved complete donor T cell chimerism followed by clinical evidence for GvMC effect. However, all patients experienced disease progression with the longest response duration of 39 months. The GvMC effect can be observed after nonmyeloablative HCT with limited efficacy. Effective cytoreductive therapy prior to HCT may be required for long-term disease control and cure.

Allogeneic peripheral blood stem cell transplantation for high-risk non-Hodgkin's lymphoma

A high incidence of nonrelapse mortality (NRM) has limited the use of allogeneic transplantation for poor prognosis non-Hodgkin's lymphoma (NHL). We sought to improve the outcome of allografting by utilizing Filgrastim-mobilized peripheral blood stem cells (PBSC) in combination with either standard ablative or reduced-intensity conditioning. A total of 21 patients with intermediate/high-grade lymphoma and seven patients with low-grade histology were enrolled on protocols using PBSC. All patients were considered high risk for recurrence and/or NRM because of age >50 (n=16), refractory disease (n=17), failed autologous transplant (n=11) and abnormal organ function (n=2). In all, 17 patients received ablative regimens and 11 received modified conditioning including fludarabine, intravenous busulfan and ATG. Tacrolimus and mini-dose methotrexate were used for graft-versus-host-disease (GVHD) prophylaxis. Median follow-up was 38 months. Disease-free and overall survival were 57 and 58%. Seven of the 11 patients who relapsed after a previous transplant remain disease free. Four of the 10 patients with recurrent/persistent disease post transplant responded to additional therapy including withdrawal of immunosuppression+/-DLI. These results support a potent graft-versus-lymphoma effect and suggest that patients who relapse after an autologous transplant can be salvaged with an allogeneic transplant.

Optimized clinical-scale culture conditions for ex vivo selective depletion of host-reactive donor lymphocytes: a strategy for GvHD prophylaxis in allogeneic PBSC transplantation

BACKGROUND

Ex vivo selective depletion (SD) is a strategy to prevent GvHD, in which host-reactive donor lymphocytes are selectively eliminated from a PBSC allograft while conserving useful donor immune function. Prior to testing this strategy in patients, our goal was to develop a clinical-scale SD process, which involves co-culture of donor lymphocytes and irradiated recipient cells, followed by the addition of an immunotoxin (IT) directed against the alpha-chain of the IL-2 receptor (CD25), expressed on activated donor T cells.

METHODS

Stimulator cells were generated from immunomagnetically selected and expanded recipient T lymphocytes. Donor PBMCs from G-CSF-mobilized peripheral blood were co-cultured for 72 h with irradiated stimulator cells. Alloreactive T cells were targeted for elimination by the addition of the anti-CD25 IT, RFT5-SMPT-dgA, and the IT enhancer, NH(4)Cl.

RESULTS

Stimulator-cell selection/expansion yielded > 2 x 10(10) highly enriched CD3(+) cells (98.9 +/- 2.2%). After SD, cell recovery was 68.5 +/- 23.3% and viability was 84.6 +/- 6.4%. This permitted a potential T-cell dose >/= 1 x 10(8) CD3(+) cells kg(-1) to transplant recipients. Although SD donor lymphocytes retained little proliferative capacity against the original stimulator cells (2.6 +/- 0.6%), responses were conserved against third party cells (107.6 +/- 18.6%), the bacterial superantigen staphylococcus enterotoxin B (108.2 +/- 4.2%), and CMV Ag (72.1 +/- 3.8%).

DISCUSSION

We have demonstrated that ex vivo SD is feasible in clinical-scale culture conditions. The ability of this strategy to prevent GvHD is the subject of an ongoing clinical trial, in which the SD lymphocyte product is transplanted in conjunction with a T cell-depleted PBSC allograft.

Transplant dose of CD34(+) and CD3(+) cells predicts outcome in patients with haematological malignancies undergoing T cell-depleted peripheral blood stem cell transplants with delayed donor lymphocyte add-back

We sought to optimize and standardize stem cell and lymphocyte doses of T cell-depleted peripheral blood stem cell transplants (T-PBSCT), using delayed add-back of donor T cells (DLI) to prevent relapse and enhance donor immune recovery. Fifty-one patients with haematological malignancies received a T-PBSCT from an HLA-identical sibling, followed by DLI of 1 x 10(7) and 5 x 10(7) CD3(+) cells/kg on d +45 and +100 respectively. Twenty-four patients were designated as standard risk and twenty-seven patients with more advanced leukaemia were designated as high risk. Median recipient age was 38 years (range 10-56). Median (range) of CD34(+) and CD3(+) cell transplant doses were 4.6 (2.3-10.9) x 10(6)/kg and 0.83 (0.38-2) x 10(5)/kg respectively. The cumulative probability of acute GVHD was 39%. No patient died from GVHD or its consequences. The probability of developing chronic GVHD was 54% (18% extensive). The probability of relapse was 12% for the standard-risk patients and 66% for high-risk patients. In multivariate analysis, the risk factors for lower disease-free survival and overall survival were high-risk disease, CD34(+) dose < 4.6 x 10(6)/kg and CD3(+) dose < 0.83 x 10(5)/kg. Predictive factors for chronic GVHD were a T-cell dose at transplant > 0.83 x 10(5) CD3(+) cells/kg. These results further define the impact of CD34 and CD3 cell dose on transplant outcome and show that careful dosing of stem cells and lymphocytes may permit the control and optimization of transplant outcome.

Regression of metastatic renal-cell carcinoma after nonmyeloablative allogeneic peripheral-blood stem-cell transplantation

BACKGROUND

Since allogeneic stem-cell transplantation can induce curative graft-versus-leukemia reactions in patients with hematologic cancers, we sought to induce analogous graft-versus-tumor effects in patients with metastatic renal-cell carcinoma by means of nonmyeloablative allogeneic peripheral-blood stem-cell transplantation.

METHODS

Nineteen consecutive patients with refractory metastatic renal-cell carcinoma who had suitable donors received a preparative regimen of cyclophosphamide and fludarabine, followed by an infusion of a peripheral-blood stem-cell allograft from an HLA-identical sibling or a sibling with a mismatch of a single HLA antigen. Cyclosporine, used to prevent graft-versus-host disease, was withdrawn early in patients with mixed T-cell chimerism or disease progression. Patients with no response received up to three infusions of donor lymphocytes.

RESULTS

At the time of the last follow-up, 9 of the 19 patients were alive 287 to 831 days after transplantation (median follow-up, 402 days). Two had died of transplantation-related causes, and eight from progressive disease. In 10 patients (53 percent) metastatic disease regressed; 3 had a complete response, and 7 had a partial response. The patients who had a complete response remained in remission 27, 25, and 16 months after transplantation. Regression of metastases was delayed, occurring a median of 129 days after transplantation, and often followed the withdrawal of cyclosporine and the establishment of complete donor-T-cell chimerism. These results are consistent with a graft-versus-tumor effect.

CONCLUSIONS

Nonmyeloablative allogeneic stem-cell transplantation can induce sustained regression of metastatic renal-cell carcinoma in patients who have had no response to conventional immunotherapy.

Engraftment kinetics after nonmyeloablative allogeneic peripheral blood stem cell transplantation: full donor T-cell chimerism precedes alloimmune responses

Nonmyeloablative allogeneic stem cell transplantation has recently been explored as a safer alternative to conventional high-dose transplant regimens. Although a high incidence of mixed chimerism after nonmyeloablative procedures has been reported, the exact kinetics of engrafting donor cells in specific cellular lineages has yet to be defined. We investigated lineage-specific chimerism in 15 patients receiving an allogeneic peripheral blood stem cell (PBSC) transplant from an HLA-identical (n = 14) or a 5/6 antigen-matched sibling donor after a preparative regimen of cyclophosphamide and fludarabine. Donor chimerism was assessed weekly in T lymphocytes and myeloid cells by polymerase chain reaction (PCR) of minisatellite regions. Eight patients survived between 121 to 409 days after transplant. Ten of 14 patients surviving more than 30 days (71.4%) had delayed disease regression consistent with a graft-versus-malignancy (GVM) effect. One patient rejected the transplant with subsequent recovery of autologous hematopoiesis. Hematological recovery was rapid (median, 11 days to >/=500 neutrophils/microL) and was initially predominantly recipient in origin. Donor myeloid chimerism gradually supplanted recipient hematopoiesis and became fully donor in all survivors by 200 days after transplantation. In contrast, T-cell engraftment was more rapid, with full chimerism in 7 patients by day 30 and in 6 further patients by day 200 after cyclosporine withdrawal and donor lymphocyte infusion. Full donor T-cell engraftment preceded donor myeloid engraftment, acute graft-versus-host disease, and disease regression, consistent with a requirement for 100% donor T-cell chimerism for full expression of the alloresponse. These results emphasize the importance of lineage-specific chimerism analysis to successfully manipulate engraftment after nonmyeloablative allogeneic PBSC transplantation.

Molecular remission of chronic myeloid leukaemia following a non-myeloablative allogeneic peripheral blood stem cell transplant: in vivo and in vitro evidence for a graft-versus-leukaemia effect

Two patients with chronic myeloid leukaemia (CML) received a non-myeloablative preparative regimen of cyclophosphamide and fludarabine, followed by an unmanipulated, G-CSF-mobilized, peripheral blood stem cell transplant from an HLA-identical sibling. Chimaerism, evaluated in myeloid and T-lymphoid lineages by PCR of minisatellite variable regions, showed day 14 post-transplant haemopoietic recovery to be 90% autologous in both patients. On day 30 the bone marrow showed only 1/20 and 2/18 donor metaphases. By day 100 post transplant both had 100% donor myeloid and lymphoid lineages as assessed by karyotype and minisatellite chimaerism analysis. They subsequently became RT-PCR negative for BCR-ABL. Both survive 7 and 14 months post transplant in molecular remission of CML. In one, donor T cells, stimulated with pre-transplant CML cells, induced 30-50% inhibition of pre-transplant leukaemic CFU-GM, but did not inhibit CFU-GM in the day 60 marrow (46% Ph-negative recipient, 54% donor). These results show that a non-myeloablative allotransplant can induce molecular remissions of CML through a graft-versus-leukaemia effect.