Cord blood NK cells engineered to express IL-15 and a CD19-targeted CAR show long-term persistence and potent antitumor activity

Chimeric antigen receptors (CARs) have been used to redirect the specificity of autologous T cells against leukemia and lymphoma with promising clinical results. Extending this approach to allogeneic T cells is problematic as they carry a significant risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are highly cytotoxic effectors, killing their targets in a non-antigen-specific manner without causing GVHD. Cord blood (CB) offers an attractive, allogeneic, off-the-self source of NK cells for immunotherapy. We transduced CB-derived NK cells with a retroviral vector incorporating the genes for CAR-CD19, IL-15 and inducible caspase-9-based suicide gene (iC9), and demonstrated efficient killing of CD19-expressing cell lines and primary leukemia cells in vitro, with marked prolongation of survival in a xenograft Raji lymphoma murine model. Interleukin-15 (IL-15) production by the transduced CB-NK cells critically improved their function. Moreover, iC9/CAR.19/IL-15 CB-NK cells were readily eliminated upon pharmacologic activation of the iC9 suicide gene. In conclusion, we have developed a novel approach to immunotherapy using engineered CB-derived NK cells, which are easy to produce, exhibit striking efficacy and incorporate safety measures to limit toxicity. This approach should greatly improve the logistics of delivering this therapy to large numbers of patients, a major limitation to current CAR-T-cell therapies.

Allogeneic stem-cell transplantation in patients with cutaneous lymphoma: updated results from a single institution

BACKGROUND

Cutaneous T-cell lymphomas (CTCLs) and its common variants mycosis fungoides (MF) and leukemic Sézary syndrome (SS) are rare extranodal non-Hodgkin's lymphomas. Patients who present with advanced disease and large-cell transformation (LCT) are incurable with standard treatments. In this article, we report the largest single-center experience with allogeneic stem-cell transplantation (SCT) for advanced CTCL.

PATIENTS AND METHODS

This is a prospective case series of 47 CTCL patients who underwent allogeneic SCT after failure of standard therapy between July 2001 and September 2013. The Kaplan-Meier method was used to estimate overall survival (OS) and progression-free survival (PFS) curves. The method of Fine and Gray was used to fit regression models to the same covariates for these cumulative incidence data.

RESULTS

The Kaplan-Meier estimates of OS and PFS at 4 years were 51% and 26%, respectively. There was no statistical difference in the OS in patients who had MF alone, SS, MF with LCT, or SS with LCT. PFS at 4 years was superior in patients who had SS versus those who did not (52.4% versus 9.9%; P = 0.02). The cumulative incidences of grade 2-4 acute graft-versus-host disease (GVHD) and chronic GVHD were 40% and 28%, respectively. The cumulative nonrelapse mortality rate was 16.7% at 2 years.

CONCLUSION

Allogeneic SCT may result in long-term remissions in a subset of patients with advanced CTCL. Although post-SCT relapse rates are high, many patients respond to immunomodulation and achieve durable remissions.

CLINICALTRIALSGOV

NCT00506129.

Bevacizumab/high-dose chemotherapy with autologous stem-cell transplant for poor-risk relapsed or refractory germ-cell tumors

BACKGROUND

High-dose chemotherapy (HDC) using sequential cycles of carboplatin/etoposide is curative for relapsed germ-cell tumors (GCT). However, outcomes of high-risk patients in advanced relapse remain poor. We previously developed a new HDC regimen combining infusional gemcitabine with docetaxel/melphalan/carboplatin (GemDMC), with preliminary high activity in refractory GCT. Given the high vascular endothelial growth factor expression in metastatic GCT and the synergy between bevacizumab and chemotherapy, we studied concurrent bevacizumab and sequential HDC using GemDMC and ifosfamide/carboplatin/etoposide (ICE) in patients with poor-risk relapsed or refractory disease.

PATIENTS AND METHODS

Eligibility criteria included intermediate/high-risk relapse (Beyer Model), serum creatinine ≤ 1.8 mg/dl and adequate pulmonary/cardiac/hepatic function. Patients received sequential HDC cycles with bevacizumab preceding GemDMC (cycle 1) and ICE (cycle 2). The trial was powered to distinguish a target 50% 2-year relapse-free survival (RFS) from an expected 25% 2-year RFS in this population.

RESULTS

We enrolled 43 male patients, median age 30 (20-49) years, with absolute refractory (N = 20), refractory (N = 17) or cisplatin-sensitive (N = 6) disease, after a median 3 (1-5) prior relapses. Disease status right before HDC was unresponsive (N = 24, progressive disease 22, stable disease 2), partial response with positive markers (PRm(+)) (N = 8), PRm(-) (N = 7) or complete response (N = 4). Main toxicities were mucositis and renal. Four patients (three with baseline marginal renal function) died from HDC-related complications. Tumor markers normalized in 85% patients. Resection of residual lesions (N = 13) showed necrosis (N = 4), mature teratoma (N = 2), necrosis/teratoma (N = 3) and viable tumor (N = 4). At median follow-up of 46 (9-84) months, the RFS and overall survival rates are 55.8% and 58.1%, respectively.

CONCLUSIONS

Sequential bevacizumab/GemDMC-bevacizumab/ICE shows encouraging outcomes in heavily pretreated and refractory GCT, exceeding the results expected in this difficult to treat population.

CLINICALTRIALSGOV

NCT00936936.

Outcomes of autologous bone marrow transplantation in non-Hodgkin's lymphoma patients who failed peripheral blood stem cell mobilization

7040

Background: Patients (pts) with relapsed/refractory non-Hodgkin's lymphoma (NHL) who fail to mobilize adequate peripheral blood stem cells (PBSC) often undergo bone marrow (BM) harvest for autologous transplantation. The outcome of these pts is not known. Methods: In this retrospective study (May 1996-September 2006), we identified 36 out of a total of 750 pts with advanced NHL, who failed to collect adequate PBSC and subsequently underwent BM harvest followed by ABMT. Decision to harvest BM was left to the treating clinician. Median age at transplant was 53 years (range 15–73). Twenty of 36 pts (55%) were male. Histology was intermediate grade in 31 (86%) patients and low grade in 5 (14%). Twelve pts (35%) had history of BM involvement with lymphoma. Median number of chemotherapy cycles received prior to mobilization was 3 (range 1–6). At the time of stem cell mobilization 18 (50%) were in complete remission (CR), 13 (37%) were in partial remission (PR) and 5 (13%) had progressive disease (PD). Twenty four (67%) pts underwent chemo-mobilization and 12 (33%) were mobilized with cytokines alone. Results: The median total nucleated cell dose and CD34+ cell dose harvested/kg were 3.72 x 108 (range 0.25–58.0) and 1.6 x 106 (range 0.03–5.8), respectively. After ABMT, 33 of 35 evaluable (94%) pts engrafted neutrophils with median time to ANC 0.5 x 109/L of 23 days (range 8–47). Median time to platelet count 20 x 109/L was 63 days (range 11–375). Two of 35 (6 %) evaluable pts failed to engraft. After ABMT, 25/36 (70%) pts achieved a CR. The incidence of NRM at 100 days was 15%. Sixteen (45%) pts relapsed at a median of 11 months (range 2–59) from ABMT. After a median follow-up of 34 months (range 0.4–100), the 3-year OS and DFS were 47% and 35%, respectively. Causes of death were: disease progression/relapse in 15 (60%), secondary malignancy in 3 (12%), multiorgan failure in 5 (20%), and unknown in 2 (8%). Conclusions: ABMT is feasible in pts who fail to mobilize adequate PBSC, however, these pts have longer time to engraftment. Although the CR rate after transplant is high, the NRM is higher than expected. Non-myeloablative allogeneic transplantation may provide better outcomes with similar toxicity and needs to be further studied.

No significant financial relationships to disclose.

Age at diagnosis does not adversely affect outcome in patients with Hodgkin's Disease (HD) after autologous transplantation

e19507

Background: Age at diagnosis is a poor prognostic factor for overall survival after standard therapy for HD. Whether older age is a prognostic factor for outcome after autologous transplantation is not known. We sought to evaluate the effect of older age at diagnosis on transplant outcome. Patients and Methods: All patients with HD undergoing autologous transplantation with BEAM conditioning (BCNU, Etoposide, Cytarabine, and Melphalan) between January 1996 and December 2007 were included in this study. During these 12 years, 248 patients (103 males) underwent autologous transplantation. Seventy two patients (29%) were older than 40 years of age at the time of initial diagnosis. Median age at transplantation was 31 years (range 11–74). At transplantation, 63 (25%) were in complete remission (CR); 148 (60%) were in partial remission (PR); and 37 (15%) had stable (SD) or progressive disease (PD). Forty-six patients (19%) had received more than 3 courses of chemotherapy prior to transplantation. LDH was elevated in 131 (53%). Peripheral blood stem cells were used as stem cell source in 241 (97%) patients. Results: With a median follow up of 48 months (range, 1–143 months), the 48-month overall (OS) and event-free survival (EFS) were 72% (95% CI; 65%-77%) and 57% (95% CI; 50%-63%), respectively. The cumulative incidence of non-relapse mortality at 1 year was 1.6%. The cumulative incidence of secondary MDS or AML was 8%. In univariate analysis, disease status (p<0.001) and number of prior chemotherapy regimens (p=0.007) were the only factors significantly predicting OS. Disease status was the only factor significant (p<0.01) in a multivariate analysis with a hazard ratio of 2.7 (1.1–6.9) and 9.2 (3.4–25) for patients in PR, and SD/PD respectively (CR reference group). Age at diagnosis was not a significant factor (see table ). Conclusions: High-dose chemotherapy and autologous transplantation abrogate the adverse impact of age at diagnosis in patients with HD.

[Table: see text]

No significant financial relationships to disclose.

Feasibility of allo-SCT after hypomethylating therapy with decitabine for myelodysplastic syndrome

Decitabine is a hypomethylating agent with activity in myelodysplastic syndrome (MDS). It is largely unknown whether treatment with this drug before allo-SCT will increase the toxicity of the preparative regimen or otherwise affect the results of the transplant. We report the outcome of 17 patients with MDS with a median age of 55.5 years (range, 36-66 years) who underwent an allo-SCT (12 siblings, 5 unrelated) after prior therapy with decitabine. Preparative regimens consisted of fludarabine in combination with BU (n=8) or melphalan (n=9). The source of stem cells was marrow in four patients and peripheral blood (PB) in 13 patients. Thirteen patients were in CR within 100 days of transplant. With a median follow-up of 12 months (range, 3-35 months), 11 patients are alive; eight in CR and three with progressive disease. Prior therapy with hypomethylating agents did not increase toxicity and may improve the outcome of allogeneic transplant in MDS and should be evaluated in a prospective trial.

Transplantation of ex vivo expanded cord blood cells using the copper chelator tetraethylenepentamine: a phase I/II clinical trial

The copper chelator tetraethylenepentamine (TEPA; StemEx) was shown to attenuate the differentiation of ex vivo cultured hematopoietic cells resulting in preferential expansion of early progenitors. A phase I/II trial was performed to test the feasibility and safety of transplantation of CD133+ cord blood (CB) hematopoietic progenitors cultured in media containing stem cell factor, FLT-3 ligand, interleukin-6, thrombopoietin and TEPA. Ten patients with advanced hematological malignancies were transplanted with a CB unit originally frozen in two fractions. The smaller fraction was cultured ex vivo for 21 days and transplanted 24 h after infusion of the larger unmanipulated fraction. All but two units contained <2 x 10(7) total nucleated cells (TNCs) per kilogram pre-expansion. All donor-recipient pairs were mismatched for one or two HLA loci. Nine patients were beyond first remission; median age and weight were 21 years and 68.5 kg. The average TNCs fold expansion was 219 (range, 2-620). Mean increase of CD34+ cell count was 6 (over the CD34+ cell content in the entire unit). Despite the low TNCs per kilogram infused (median=1.8 x 10(7)/kg), nine patients engrafted. Median time to neutrophil and platelet engraftment was 30 (range, 16-46) and 48 (range, 35-105) days. There were no cases of grades 3-4 acute graft-versus-host disease (GVHD) and 100-day survival was 90%. This strategy is feasible.

Efficacy of prophylactic transfusions using single donor apheresis platelets versus pooled platelet concentrates in AML/MDS patients receiving allogeneic hematopoietic stem cell transplantation

Superiority of single-donor apheresis platelets (SDAP) over pooled platelet concentrates (PPC) transfusions is largely assumed, but unproven. We hypothesized that prophylactic SDAP and PPC transfusions are clinically equivalent after allogeneic hematopoietic stem cell transplants (HSCT). We studied all transfusions administered to 33 patients with AML/MDS during the first 100 days after busulfan-based, myeloablative HSCT. All donor-recipient pairs were ABO identical. Transfusion threshold was a platelet count < or =15 x 10(9)/l. The corrected increment (CCI) was used for all comparisons. Median time to platelet engraftment was 13 days (n=30). PPC transfusions (n=105) were ABO compatible, while 10% of 41 SDAP were not (P=0.006). Median post-transfusion platelet count was 51K/microl (5-118K) after SDAP and 36K/microl (3-115K) after PPC (P=0.0004). Median CCI was 14.178 (SDAP) versus 7.793 (PPC) (P=0.0001). Median time to another transfusion was 3 days (SDAP) and 2 days (PPC; P=0.3). In the week following any given transfusion, the median number of new transfusions was similar (n=2), as well as the need of further transfusion (16 versus 24%, P=0.2). A total of 17% of SDAP and 30% of PPC transfusions were labeled 'ineffective' (P=0.1). There were two non-lethal hemorrhage episodes (6%). SDAP transfusions produced better platelet counts, but SDAP and PPC were equally effective in preventing hemorrhage.

Long-term survival of patients with AML in remission after reduced intensity allogeneic hematopoietic stem cell transplantation (RISCT)

7002

Background: RISCT was developed to harness graft versus leukemia effect to treat older patients (pts) and pts with comorbidities. Limited data are available on long term outcome of pts with high risk AML treated in complete remission (CR), a group most likely to benefit from this approach. Methods: Thirty six consecutive pts with AML in CR, treated between 1999 and 2006 with Fludarabine 120–125 mg/m2 and Melphalan 100–140 mg/m2 are included. Pts were not eligible for myeloablative transplantation because of age or comorbidity. Tacrolimus and Methotrexate were used as GVHD prophylaxis. Additionally pts receiving stem cells from an unrelated donor received rabbit antithymocyte globulin. Results: There were 24 males and 12 females with a median age of 57 (range 21–71). Eighteen(50%) pts had secondary AML. Thirty(83%) pts were in first CR and 6(17%) in second CR. Cytogenetic risk groups were as follows: 2 good risk (in CR2), 22 intermediate risk(61%), and 10(28%) poor risk. Source of stem cells was peripheral blood in 18 pts (50%) and bone marrow in 18 pts (50%). Donors were siblings in 21(58%) pts and unrelated in 15 (42%)pts. Hematopoietic cell transplant specific comorbidity score of 3 or higher was present in 26 pts (72%). All pts engrafted achieving full donor chimerism by day 30 with median time to neutrophil engraftment of 12.5 days (8–19 days). Cumulative incidence of grade 2–4 acute graft versus host disease (GVHD), grade 3–4 GVHD and chronic GVHD was 25% (95% CI; 14%–44%), 11% (95% CI; 4%–28%), and 63% (95% CI; 47%–84%) respectively. Cumulative incidence of nonrelapse mortality was 19% (95% CI; 8%–41%). With a median follow up of 852 days, 3 year overall and disease free survival is 75% (SE 9%) and 63% (SE 10%) respectively. Comorbidity scores didnot impact outcome. Conclusions: Reduced intensity allogeneic transplantation with Fludarabine and Melphalan conditioning produces durable long term remission in pts with high risk AML in complete remission. These results in older pts and/or pts with comorbidities are comparable to published results in younger pts receiving myeloablative transplantation. Comorbidity scores by themselves should not be used to exclude patients from receiving transplant.

No significant financial relationships to disclose.

Elevated stem cell marker CD133 mRNA in peripheral blood predicts colon cancer recurrence

10504

Background: CD133 is a specific stem cell marker that enriches cancer stem cells of many tumor types including colon cancer as well as circulating endothelial progenitors (CEP). CEP is vital in postnatal angiogenesis and elevated CEP is a proven favoable prognositic marker for heart disease but a potentially poor prognostic marker for cancer. We examined whether elevated CD133 mRNA expression levels in peripheral blood mononuclear cells (PBMC) predict recurrence in colon cancer patients. Methods: We developed and validated a semi-quantitative real-time RT-PCR to quantify CD133 mRNA levels relative to GADPH mRNA. Sixty-six colon cancer patients were enrolled between February 2002 and December 2003. The protocol excluded patients with history of cardiac disease or surgery < 4 weeks from the enrollment and were followed for recurrence for a median 30 months. A central statistician performed multivariate unconditional logistics regression analysis. Results: Among the patients without recurrence, 93% had a CD133 mRNA level < 4.79, whereas 7% had a CD133 mRNA value ≥ 4.79 (p = 0.029). Among patients with a CD133 mRNA value ≥ 4.79, 85% had experienced recurrence compared to 15% of the patient who had no recurrence (p = 0.03). Elevated CD133 mRNA levels at a cut-off point ≥ 4.79 versus < 4.79 were associated with an odd ratio of 22.6 for recurrence (95% CI, 1.7–291.2; p = 0.02); in comparison, the odds ratio for recurrence was 17.2 (95% CI, 1.8–164; p = 0.01) for stage IV patients versus stage I-III patients. No other predictive variables for recurrence were identified including age, race, sex, tumor differentiation, smoking, and diabetes etc. We also observed an trend of association with elevated carcinoma embryonic antigen (CEA) levels (p = 0.03, one sided) and a decreased survival (p = 0.035, one sided) with elevated CD133 mRNA level at a cutoff point ≥ 4.79. Conclusions: Elevated CD133 mRNA levels at a cutoff ≥ 4.79 in PBMC predict colon cancer recurrence independent of stage IV disease. The current assay has certain advantages over flow cytometry for wider clinical application. CD133+ cells measured by CD133 mRNA may contain both CEP and cancer stem cells, leading to increased risks of recurrence.

No significant financial relationships to disclose.

Microbial contamination of hematopoietic progenitor cell products: clinical outcome

We reviewed the results of routine microbiological assays of 3078 infused hematopoietic progenitor cell (HPC) products for autologous and allogeneic transplantation between January 2001 and December 2005. Thirty-seven (1.2%) contaminated products were found. All patients receiving contaminated infusions received empirical antibiotic prophylaxis according to the assay result. None of these patients developed a positive blood culture with the same agent, developed infections that could be attributable to the contaminated product or experienced any clinical sequelae. Coagulase-negative Staphylococcus was found in 32 (86.5%) products. Admission lengths and time to engraftment were within the expected time frame for autologous and allogeneic transplants. Microbial contamination of HPC products occurs at a low frequency; prophylactic use of antibiotics based on the microbiological assay appears to be effective in preventing clinical complications.

Ex vivo expanded umbilical cord blood T cells maintain naive phenotype and TCR diversity

BACKGROUND

Umbilical cord blood (CB) is a promising source of hematopoietic stem cells for allogeneic transplantation. However, delayed engraftment and impaired immune reconstitution remain major limitations. Enrichment of donor grafts with CB T cells expanded ex vivo might facilitate improved T-cell immune reconstitution post-transplant. We hypothesized that CB T cells could be expanded using paramagnetic microbeads covalently linked to anti-CD3 and anti-CD28 Ab.

METHODS

CB units were divided into three fractions: (1) cells cultured without beads, (2) cells cultured with beads and (3) cells cultured with beads following CD3+ magnetic enrichment. All fractions were cultured for 14 days in the presence of IL-2 (200 IU/mL).

RESULTS

A mean 100-fold expansion (range 49-154) of total nucleated cells was observed in the CD3+ magnetically enriched fraction. Following expansion, CB T cells retained a naive and/or central memory phenotype and contained a polyclonal TCR diversity demonstrated by spectratyping.

DISCUSSION

Our data provide evidence that naive and diverse CB T cells may be expanded ex vivo and warrant additional studies in the setting of human CB transplantation.

Steroid myopathy in patients with acute graft-versus-host disease treated with high-dose steroid therapy

High-dose steroids are the first line of treatment for acute graft-versus-host disease (aGVHD). Steroid myopathy is a debilitating steroid-induced complication that significantly impairs a patient's performance status. To determine the frequency and severity of steroid myopathy and other steroid related complications in patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) who developed grade >or=2 aGVHD after allogeneic hematopoietic stem cell transplantation (HSCT), we performed a retrospective analysis. Patients were included in the analysis if they had a diagnosis of AML/MDS, underwent an allogeneic HSCT between January 1996 and December 2001 and developed grade >or=2 aGVHD that was treated with 2 mg/kg of methylprednisolone and survived at least 100 days post transplant. A total of 70 patients fulfilled our inclusion criteria. Steroid myopathy was identified in 29 (41%) patients. Steroid myopathy was generally of moderate severity with severe debilitating steroid myopathy seen in only 3% of patients. We concluded that steroid myopathy is a common complication of high-dose steroid therapy after allogeneic HSCT in AML/MDS. Interventions aimed at preventing and treating this complication are warranted and need to be explored in prospective clinical trials.

Intravenous (i.v.) busulfan (Bu) plus melphalan (Mel) is a well-tolerated preparative regimen for stem cell transplantation (SCT) in patients (pts) with advanced lymphoid malignancies

6548

Background: High dose chemotherapy and SCT is an accepted treatment option for pts with relapsed lymphoid malignancies. However, relapse remains a significant problem. A double alkylating regimen of Bu and Mel has been suggested as an effective and myeloablative pre-transplant conditioning regimen. Historically, oral Bu was used and the combination resulted in considerable mucositis and VOD. An i.v. formulation of Bu has been developed that has less pharmacokinetic variability. We are investigating i.v. Bu-Mel in pts with lymphoid malignancies undergoing auto- or allo-SCT. Patients and Methods: The conditioning regimen consists of i.v. Bu 130 mg/m2 over 3 hr daily for 4 days, either as a fixed dose per BSA, or to target an average daily AUC of 5,000 μMol-min ± 12% determined by a test dose of i.v. Bu at 32 mg/m2 given 48 hours prior to the high dose regimen. After the 4 daily Bu doses, there is a rest day, followed by 2 daily doses of Mel at 70mg/m2. Stem cells are infused the following day. Dilantin is given for seizure prophylaxis. GVHD prophylaxis is tacrolimus and methotrexate for pts receiving allo-SCT. Results: Patient characteristics, engraftment, and regimen-related toxicities are listed below: Grade I or II mucositis was the most common regimen-related toxicity. There were no cases of VOD; reversible hyperbilirubinemia was observed in 3 pts receiving allo-SCT. No grade IV toxicity was noted, and there were no regimen-related deaths with longest follow-up of 10 months. All allo-SCT pts had 100% donor chimerism by day 30. 27 pts had i.v. Bu delivered per test dose guidance; 6 pts received fixed dose Bu at 130 mg/m2. The median daily systemic Bu exposure was 4867 μMol-min. Conclusion: Intravenous Bu-Mel is well tolerated, and enables prompt neutrophil and platelet engraftment. Individualized PK-directed dosing of i.v. Bu is feasible, and likely contributes to the low toxicity profile of this regimen. Longer time is needed to assess disease control.

[Table: see text]

No significant financial relationships to disclose.

Superior ex vivo cord blood expansion following co-culture with bone marrow-derived mesenchymal stem cells

One factor limiting the therapeutic efficacy of cord blood (CB) hematopoietic progenitor cell (HPC) transplantation is the low cell dose of the graft. This is associated with an increased incidence of delayed or failed engraftment. Cell dose can be increased and the efficacy of CB transplantation potentially improved, by ex vivo CB expansion before transplantation. Two ex vivo CB expansion techniques were compared: (1) CD133+ selection followed by ex vivo liquid culture and (2) co-culture of unmanipulated CB with bone-marrow-derived mesenchymal stem cells (MSCs). Ex vivo culture was performed in medium supplemented with granulocyte colony-stimulating factor, stem cell factor and either thrombopoietin or megakaryocyte growth and differentiation factor. Expansion was followed by measuring total nucleated cell (TNC), CD133+ and CD34+ cell, colony-forming unit and cobblestone area-forming cell output. When compared to liquid culture, CB-MSC co-culture (i) required less cell manipulation resulting in less initial HPC loss and (ii) markedly improved TNC and HPC output. CB-MSC co-culture therefore holds promise for improving engraftment kinetics in CB transplant recipients.

Ex vivo expansion of umbilical cord blood

The efficacy of cord blood (CB) transplantation is limited by the low cell dose available. Low cell doses at transplant are correlated with delayed engraftment, prolonged neutropenia and thrombocytopenia and elevated risk of graft failure. To potentially improve the efficacy of CB transplantation, approaches have been taken to increase the cell dose available. One approach is the transplantation of multiple cord units, another the use of ex vivo expansion. Evidence for a functional and phenotypic heterogeneity exists within the HSC population and one concern associated with ex vivo expansion is that the expansion of lower 'quality' hematopoietic progenitor cells (HPC) occurs at the expense of higher 'quality' HPC, thereby impacting the reserve of the graft. There is evidence that this is a valid concern while other evidence suggests that higher quality HPC are preserved and not exhausted. Currently, ex vivo expansion processes include: (1) liquid expansion: CD34+ or CD133+ cells are selected and cultured in medium containing factors targeting the proliferation and self-renewal of primitive hematopoietic progenitors; (2) co-culture expansion: unmanipulated CB cells are cultured with stromal components of the hematopoietic microenvironment, specifically mesenchymal stem cells (MSC), in medium containing growth factors; and (3) continuous perfusion: CB HPC are cultured with growth factors in 'bioreactors' rather than in static cultures. These approaches are discussed. Ultimately, the goal of ex vivo expansion is to increase the available dose of the CB cells responsible for successful engraftment, thereby reducing the time to engraftment and reducing the risk of graft failure.

Sirolimus in combination with tacrolimus and corticosteroids for the treatment of resistant chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) remains a major cause of morbidity and mortality in haematopoietic transplant recipients. Sirolimus is a macrocyclic triene antibiotic with immunosuppressive, antifungal and antitumour properties, that has activity in the prevention and treatment of acute GVHD. We conducted a phase II trial of sirolimus combined with tacrolimus and methylprednisolone in patients with steroid-resistant cGVHD. Thirty-five patients who developed GVHD after day 100 post-transplant were studied. Six patients had a complete response and 16 a partial response with an overall response rate of 63%. Major adverse events related to the combination of tacrolimus and sirolimus were hyperlipidaemia, renal dysfunction and cytopenias. Four patients had thrombotic microangiopathy (TMA) and 27 (77%) had infectious complications. The median survival for the whole group was 15 months. A significantly better outcome was observed in patients with a platelet count > or = 100 x 10(9)/l, as well as in those with true chronic manifestations of GVHD compared to those with acute GVHD beyond day 100. Controlled trials comparing this approach with alternative strategies to determine which can best achieve the goal of GVHD-free survival are warranted.

CD8+ cell depletion of donor lymphocyte infusions using cd8 monoclonal antibody-coated high-density microparticles (CD8-HDM) after allogeneic hematopoietic stem cell transplantation: a pilot study

A CD8 murine monoclonal antibody-coated high-density microparticle (HDM) has been developed, which allows for the rapid depletion of CD8+ T cells from apheresis products by gravity sedimentation. We conducted a study to determine the efficacy and safety of CD8 depletion of donor lymphocyte infusions (DLI) to treat relapse after stem cell transplantation using the Eligix CD8-HDM Cell Separation System. Patients were targeted to receive 3 x 10(7) CD4+ T cells/kg. Nine patients were enrolled, three with CML, three myeloma, two CLL, and one NHL. A median of 1 x 10(10) mononuclear cells were obtained by apheresis and processed. The median depletion of CD8+ cells was 99.3% (97.8->99.5%). CD8 depletion was highly specific, with a median recovery of CD4+ cells of 75%. A median of 2.9 x 10(7) CD4+ cells/kg was infused. No infusional toxicity was noted. All CML patients achieved a complete molecular remission. A CLL patient demonstrated a complete response. One patient developed GVHD (grade II acute GVHD and subsequently chronic GVHD). The CD8-HDM Cell Separation System appears to be highly selective and effective in depleting CD8+ T cells from DLI apheresis products, and CD8-depleted DLI is capable of mediating a graft-versus-leukemia effect while minimizing GVHD.