Peter Dreger

G-CSF-mobilized peripheral blood progenitor cells for allogeneic transplantation: safety, kinetics of mobilization, and composition of the graft.

Allogeneic transplantation of peripheral blood progenitor cells (PBPC) markes the general anaesthesia of the donor unnecessary and may result in more rapid engraftment and faster recovery of the immune system. We have studied G‐CSF‐mediated PBPC mobilization in healthy donors and analysed the cellular composition of the resulting PBPC grafts. PBPC grafts were obtained from nine healthy donors (18‐67 years old) for allogeneic or syngeneic transplantation. Six donors received 10 μg/kg G‐CSF per day, the others 5‐6 μg/kg. Mobilization and harvesting were well tolerated except for moderate bone pain which occurred in all donors primed with 10 μg/kg. With 10 μg/kg, a 31‐fold (9‐62) enrichment of circulating CD34+ cells was observed with peak values constantly occurring on day 5 after the start of G‐CSF administration. Starting harvest on day 5, one to three collections on consecutive days yielded 5.5 x 106/kg (0.9‐10.7) CD34+ cells, 219 x 106/kg (106–314) T cells, and 34 x 106/kg (23–67) NK cells per 10 litres leukapheresis volume. Altogether, PBPC grafts contained 3 times more CD34+ cells, 7 times more T cells, and 20 times more NK cells than five allogeneic marrow grafts that were analysed for comparison. The yield of CD34+ cells per 10 litres apheresis volume as well as the height of the CD34+ peak in peripheral blood were inversely correlated to the age of the donor. In the donors primed with 5–6μg/kg G‐CSF the increase of circulating CD34+ cells (4–7‐fold enrichment) and the CD34+ cell yield per 10 litres leukapheresis volume (1 x 106/kg [0.8‐2‐2]) was much smaller compared with the 10μg/kg group. In conclusion, sufficient amounts of PBPC capable of restoring haemopoiesis in allogeneic recipients can be mobilized safely by administration of G‐CSF (10 μg/kg s.c. for 5 d) in healthy donors, and harvested with one or two leukapheresis procedures. Whether the large numbers of T‐cells and NK cells that are contained in the collection products may influence graft‐versus‐host and graft‐versus‐leukaemia reactivities of PBPC grafts remains to be determined.

Comparative analysis of minimal residual disease detection using four-color flow cytometry, consensus IgH-PCR, and quantitative IgH PCR in CLL after allogeneic and autologous stem cell transplantation

The clinically most suitable method for minimal residual disease (MRD) detection in chronic lymphocytic leukemia is still controversial. We prospectively compared MRD assessment in 158 blood samples of 74 patients with CLL after stem cell transplantation (SCT) using four-color flow cytometry (MRD flow) in parallel with consensus IgH-PCR and ASO IgH real-time PCR (ASO IgH RQ-PCR). In 25 out of 106 samples (23.6%) with a polyclonal consensus IgH-PCR pattern, MRD flow still detected CLL cells, proving higher sensitivity of flow cytometry over PCR-genescanning with consensus IgH-primers. Of 92 samples, 14 (15.2%) analyzed in parallel by MRD flow and by ASO IgH RQ-PCR were negative by our flow cytometric assay but positive by PCR, thus demonstrating superior sensitivity of RQ-PCR with ASO primers. Quantitative MRD levels measured by both methods correlated well (r=0.93). MRD detection by flow and ASO IgH RQ-PCR were equally suitable to monitor MRD kinetics after allogeneic SCT, but the PCR method detected impending relapses after autologous SCT earlier. An analysis of factors that influence sensitivity and specificity of flow cytometry for MRD detection allowed to devise further improvements of this technique.

Quantitative MRD monitoring identifies distinct GVL response patterns after allogeneic stem cell transplantation for chronic lymphocytic leukemia: results from the GCLLSG CLL3X trial

The purpose of this study was to prospectively analyze minimal residual disease(MRD) kinetics after reduced-intensity allogeneic stem cell transplantation (allo-SCT) in high-risk chronic lymphocytic leukemia (CLL). Subjects were the first 30 consecutive patients from a prospective clinical trial, and seven pilot patients treated identically. Using real-time quantitative-PCR (RQ-PCR) and/or flow-based MRD monitoring (sensitivity ⩾10−4), five distinct patterns of MRD kinetics could be identified: patients who promptly achieved durable MRD negativity without direct evidence of graft-versus-leukemia (GVL) effects (Group 1) (n=4; no clinical relapse); patients with complete and sustained MRD response after GVL induced by immunosuppression tapering (Group 2) or donor lymphocyte infusions (Group 3) (n=18; one relapse); patients without MRD response due to lack of GVL (Group 4) (n=2; two relapses); patients with incomplete and transient MRD response to GVL (Group 5) (n=4; three relapses). In summary, this study provides a comprehensive map of possible MRD courses and their prognostic implications after T-replete allo-SCT in high-risk CLL, indicating that effective GVL activity is induced virtually in all patients who develop chronic GVHD. However, in a significant proportion of cases, this does not translate into sustained disease control due to development of secondary GVL resistance.

Effective mobilisation of peripheral blood progenitor cells with 'Dexa-BEAM' and G-CSF: timing of harvesting and composition of the leukapheresis product.

The mini-BEAM regimen (BCNU, etoposide, cytarabine, melphalan) and its modification Dexa-BEAM are effective salvage protocols for relapsed Hodgkins disease and non-Hodgkins lymphoma. Since many patients with relapsed lymphoma are eligible for high-dose chemotherapy with autologous stem cell rescue, we were interested in the suitability of these second line regimens for mobilising peripheral blood progenitor cells (PBPC). The kinetics of PBPC were studied in 15 patients treated with Dexa-BEAM and granulocyte colony-stimulating factor (G-CSF). Leukocytes started to rise from < 0.5 nL-1 on day 18 (16-22) after Dexa-BEAM, and exceeded 10 nL-1 on day 20 (18-28). Peripheral blood CFU-GM peaked on day 21 (19-28) and declined slowly thereafter; the median leukocyte count was 18.7 nL-1 (12.2-60) on the day of CFU-GM-peak. The maximum number of CFU-GM circulating in peripheral blood was inversely correlated to the duration of leukopenia after Dexa-BEAM. Measurement of CD34+ cells with the monoclonal antibody 8G12-PE (HPCA-2) predicted the number of CFU-GM precisely in both peripheral blood and leukapheresis products (r = 0.90-0.95). Two to six leukapheresis procedures yielded 6.39 x 10(8) mononuclear cells kg-1 (1.82-13.49) containing 44.4 x 10(4) CFU-GM kg-1 (2.2-213.8). Immunophenotypical analysis revealed that the percentage of CD19+ B cells was very low in all collection products (less than 1%). Nine patients were autografted with PBPC (15.4-213.8 x 10(4) CFU-GM kg-1) after myeloablative chemotherapy and experienced rapid and sustained engraftment (Platelets > 50 nL-1 on day +13 [9-22]). We conclude that PBPC can be mobilised effectively by Dexa-BEAM plus G-CSF. An adequate timing of PBPC collection (when the leukocyte count has exceeded 10 nL-1) and evaluation of the progenitor content of the leukapheresis products with 8G12-PE will allow to minimise the number of leukaphereses.

Early stem cell transplantation for chronic lymphocytic leukaemia: a chance for cure?

B-cell chronic lymphocytic leukaemia (CLL) cannot be cured by conventional therapy. To improve the prognosis of patients with CLL, we have designed a sequential treatment strategy that comprises intensive chemotherapy for mobilization of peripheral blood progenitor cells (PBPCs) and induction of minimal disease, followed by high-dose radiochemotherapy with stem cell reinfusion and post-transplant molecular monitoring by polymerase chain reaction (PCR) amplification of the complementary determining region III (CDRIII) gene. In a prospective study, we have evaluated this protocol in 18 patients with CLL, also including early stages of the disease. The median age was 49 (29-61) years; Binet stages were A, six; B, nine; and C, three. Adverse prognostic factors [high lymphocyte count and/or diffuse bone marrow (BM) infiltration] were present in 16 out of 18 patients. All patients showed a clone-specific molecular marker as demonstrated by PCR amplification of CDRIII rearrangements. For stem cell mobilization and reduction of tumour load, one to two cycles of Dexa-BEAM chemotherapy were administered, resulting in minimal disease (circulating lymphoma cells <1 x 10(9) l(-1); BM infiltration <20%; lymphomas <2 cm) in 16 out of 18 patients, including four patients who already had minimal disease before Dexa-BEAM. Stem cell harvesting was successful in 14 patients. All grafts [three BM, 11 peripheral blood (PB)] were purged from leukaemic cells using immunomagnetic methods. Thirteen patients having achieved minimal disease were reinfused with purged autologous stem cells (ASC) after preparation with total body irradiation and cyclophosphamide. Engraftment was delayed in patients receiving BM (n = 3) but prompt [neutrophils >0.5 x 10(9) l(-1) after 10 (9-13) days, platelets >20 x 10(9) l(-1) after 11 (9-214) days] in patients restored with PBPCs (n = 10). Procedure-related deaths did not occur. Although the results of CDRIII PCR suggest persistence or recurrence of the leukaemic clone in at least three cases, to date only one patient has relapsed, whereas all others survive without clinical evidence of disease with a maximum follow-up of 48 months. We conclude that sequential high-dose therapy using Dexa-BEAM and autologous stem cell transplantation is a safe and highly effective treatment for patients with CLL. However, a longer follow-up is needed to assess whether definite cures can be achieved using this strategy.

Allogeneic MHC-mismatched activated natural killer cells administered after bone marrow transplantation provide a strong graft-versus-leukaemia effect in mice.

Allogeneic lymphocytes administered with an unmanipulated bone marrow transplant provide a strong antileukaemic effect, the so‐called graft‐versus‐leukaemia (GVL) effect. On the other hand, T‐cell‐mediated graft‐versus‐host‐disease (GVHD) observed after transplantation of unmanipulated BM graft causes substantial morbidity and mortality. The aim of the present study was to determine the antileukaemic potential of enriched IL‐2 activated NK cells administered 2u2003h after BMT. Balb/c (H‐2d) mice were given a dose of A20 (H‐2d, B‐cell leukaemia) cells 2u2003d prior to lethal total body irradiation (TBI) and transplantation of either syngeneic or allogeneic anti‐Thy1.2 (CD90) depleted bone marrow cells. Either syngeneic (Balb/c, H‐2d) or allogeneic (C57BL/6, H‐2b) enriched and IL‐2 (200u2003U/ml for 24 h) activated NK cells were given 2u2003h after BMT. Injection of A20 leukaemia into normal Balb/c recipients led to death after a median of 14u2003d. A lethal dose of TBI followed by either syngeneic or allogeneic Thy1.2‐depleted BMT resulted in a modest antileukaemic effect. The adoptive transfer of syngeneic enriched and IL‐2 preincubated NK cells given at time of BMT exerted a significantly better GVL effect. However, the infusion of allogeneic enriched NK cells resulted in a stronger GVL effect. These results clearly demonstrate that allogeneic NK cells are superior to syngeneic NK cells in their potential to eradicate residual leukaemia cells after BMT without mediating clinical overt GVHD. This experimental setting may offer a strategy for treatment of haematological malignancies in a phase of minimal residual disease.

Myeloablative radiochemotherapy followed by reinfusion of purged autologous stem cells for Waldenström's macroglobulinaemia

Waldenströms macroglobulinaemia (WM) is an incurable lymphoproliferative disorder. The purpose of this study was to investigate the role of autologous peripheral blood stem cell transplantation (ASCT) for the treatment of WM. Seven patients (untreated or after first‐line therapy) with symptomatic WM underwent two or three cycles of Dexa‐BEAM chemotherapyu2003+u2003G‐CSF with stem cell harvesting and proceeded to total body irradiation and high‐dose cyclophosphamide followed by reinfusion of ex‐vivo B‐cell‐depleted stem cells. Engraftment was prompt, and procedure‐related deaths did not occur. A strong reduction or normalization of BM infiltration and serum IgM levels occurred in all evaluable patients, but immunofixation electrophoresis revealed persistent paraproteinaemia in five of them. With 3–30 months of follow‐up, all patients are alive without clinical or serological signs of disease progression. This pilot trial shows for the first time that high‐dose radiochemotherapy with purged stem cells is effective and may improve the course of patients with WM. In the majority of cases, however, complete eradication of the disease does not appear to be possible with ASCT alone.

Combined positive/negative selection for highly effective purging of PBPC grafts: towards clinical application in patients with B-CLL.

Autologous PBPC transplantation is a potentially curative treatment for patients with chronic lymphocytic leukemia (CLL). As the autografts are frequently contaminated with large numbers of tumor cells, we have studied double purging of PBPC using immunomagnetic CD34+ cell selection (Isolex 300i) followed by negative depletion with anti-CD19/20/23/37-labeled immunomagnetic beads. In four small-scale experiments using PBPC from patients with CLL or leukemic low-grade lymphoma, double purging resulted in CD34+ enrichment from 0.9–4.4% to 95.8–99.4%. Lymphoma cells were always undetectable by FACS and PCR (CDR3 or t(14;18)) after negative depletion. Next, seven heavily contaminated full grafts from five patients with CLL or lymphoplasmocytoid immunocytoma were subjected to the double purging procedure, resulting in a CD34+ enrichment from 1.6% (0.7–5.6) to 98.5% (96–99.8). The CD34+ yield after double purging was 1.3–6.3u2009×u2009106/kg, according to a median recovery of 32%. The overall reduction of lymphoma cells was 5.6 (>4.6–6) log. Although CLL cells were completely absent after purging in five cases as assessed by FACS, all grafts remained PCR positive. The first two patients have been reinfused with double selected products after myeloablative radiochemotherapy and showed prompt and uneventful hematopoietic engraftment. We conclude that without significant loss of CD34+ cells, negative depletion adds 2 log of CLL cell depletion to CD34+ selection, resulting in an overall purging efficacy of more than 5 log. This combination of positive and negative selection can be successfully applied even to heavily contaminated PBPC grafts.

Autografting of highly purified peripheral blood progenitor cells following myeloablative therapy in patients with lymphoma: a prospective study of the long-term effects on tumor eradication, reconstitution of hematopoiesis and immune recovery.

In a prospective study, we have investigated CD34+ selection of peripheral blood progenitor cells (PBPC) for autotransplantation in patients with lymphoma. Twenty-six consecutive patients (10 follicular lymphomas, seven mantle cell lymphomas, seven B-CLL, two immunocytomas) were mobilized using chemotherapy plus G-CSF. Sufficient numbers of PBPC could be collected from 24 patients and were immunoselected with the semiautomated Isolex 300 (n = 17) or the fully integrated Isolex 300i (n = 7) devices. The selection products were assayed by PCR amplification of clonal CDRIII or t(14;18) rearrangements for residual tumor cell content. Residual disease and long-term hematopoietic and immune recovery were studied by assessing the following parameters at 3, 6, and 12 months post-transplant: CDRIII or t(14;18) PCR, platelet count, lymphocyte subsets, serum IgG, serum IgA, and measles titer. With the Isolex 300 device 26% (10–65) of input CD34+ cells were recovered with a median purity of 89.2% (49.4–98.9) after CD34+ selection. The Isolex 300i device allowed significantly better recoveries (46% (22–86)) and purities of CD34+ cells (98.8% (92.2–99.2)). The overall purging efficacy was 3.2 (0.6–5.1) log. Twenty patients have been reinfused with CD34+ selected grafts after myeloablative preparation. Rapid engraftment occurred in all patients. With a median follow-up of 28 (19–42) months, 14 patients are alive without clinical or molecular evidence of disease recurrence, whereas five have relapsed and one additional patient shows persistent presence of the disease-specific molecular marker without clinical progression. Cellular and serological parameters of hematopoietic and immune functions were largely normal at 12 months post-transplant including the measles titer which was present in all patients. Kinetics of immunohematopoietic recovery were similar to those of 12 control patients who had received unmanipulated PBPC during the same time period except for the recovery of CD4+ CD45RA+ T cells which was significantly delayed in the CD34+ group. During the first year post-transplant, transient monoclonal or oligoclonal gammopathies were observed in seven of 16 study patients. We conclude that CD34+ selection with the Isolex system allows preparation of highly purified CD34+ fractions and effective tumor cell depletion. The CD34+ products can be reinfused safely after myeloablative treatment and result in sustained hematopoietic and immune recovery. The fact that all patients retained their specific measles immunity suggests that myeloablative treatment with reinfusion of highly purified CD34+ PBPC is not immunoablative.

Long-term disease-free survival of patients with advanced mantle-cell lymphoma following high-dose chemotherapy

In advanced stage mantle cell lymphoma, conventional chemotherapy yields a complete remission rate below 40%, and the median survival rate is only about 3 years. Between 1991 and 1996 we treated nine such patients (six male; three female) with high-dose chemotherapy (six of these also with 12 Gy fractionated total body irradiation (TBI)) and peripheral stem cell support (n = 8) or allogeneic bone marrow transplantation (n = 1). The median age was 47 years (range, 28–61). At the time of high-dose chemotherapy, five patients were in first complete remission (CR), two in first partial remission (PR) and two in second remission (CR = 1; PR = 1). High-dose chemotherapy included TBI (12 Gy), etoposide and cyclophosphamide (patients 1–5), TBI and cyclophosphamide (patient 7), busulfan, etoposide and cyclophosphamide (patients 6 and 9), cyclophosphamide and busulfan (patient 8). The patterns of toxicity according to the Bearman score were usually mild (mucositis grade 2, n = 7; renal grade I, n = 2) with no therapy-related fatality. Only one patient developed hepatic toxicity grade III (veno-occlusive disease) but recovered completely. The median time to neutrophil engraftment was 10 days (range, 8–15). After high-dose chemotherapy all patients achieved complete remission. After a median follow-up of 22 months (range, 9.4–64) all patients remain in continuous complete remission. These encouraging results suggest that high-dose chemotherapy can be applied safely and leads to long-term disease-free survival in otherwise incurable disease.