Andreas Humpe

Allogeneic stem cell transplantation provides durable disease control in poor-risk chronic lymphocytic leukemia: long-term clinical and MRD results of the German CLL Study Group CLL3X trial

The purpose of this prospective multicenter phase 2 trial was to investigate the long-term outcome of reduced-intensity conditioning allogeneic stem cell transplantation (alloSCT) in patients with poor-risk chronic lymphocytic leukemia. Conditioning was fludarabine/ cyclophosphamide-based. Longitudinal quantitative monitoring of minimal residual disease (MRD) was performed centrally by MRD-flow or real-time quantitative polymerase chain reaction. One hundred eligible patients were enrolled, and 90 patients proceeded to alloSCT. With a median follow-up of 46 months (7-102 months), 4-year nonrelapse mortality, event-free survival (EFS) and overall survival (OS) were 23%, 42%, and 65%, respectively. Of 52 patients with MRD monitoring available, 27 (52%) were alive and MRD negative at 12 months after transplant. Four-year EFS of this subset was 89% with all event-free patients except for 2 being MRD negative at the most recent assessment. EFS was similar for all genetic subsets, including 17p deletion (17p-). In multivariate analyses, uncontrolled disease at alloSCT and in vivo T-cell depletion with alemtuzumab, but not 17p-, previous purine analogue refractoriness, or donor source (human leukocyte antigen-identical siblings or unrelated donors) had an adverse impact on EFS and OS. In conclusion, alloSCT for poor-risk chronic lymphocytic leukemia can result in long-term MRD-negative survival in up to one-half of the patients independent of the underlying genomic risk profile. This trial is registered at http://clinicaltrials.gov as NCT00281983.

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.

A cell‐based approach to the minimization of immunosuppression in renal transplantation

Five renal transplant recipients were preoperatively treated with transplant acceptance‐inducing cells (TAICs) in a Phase‐I safety study of TAICs as an adjunct immune‐conditioning therapy in living‐donor kidney transplantation. Initially, patients received anti‐thymocyte globulin induction therapy in combination with tacrolimus and steroid immunosuppression. Over the course of 12 weeks, steroids were withdrawn and tacrolimus therapy was minimized. Three of the five patients were able to tolerate low‐dose tacrolimus monotherapy and one patient was withdrawn from all immunosuppression for over 8 months. No acute or delayed adverse events were associated with the infusion of TAICs. Monitoring of the recipient anti‐donor reactivity of TAIC‐treated patients in mixed lymphocyte cultures demonstrated that, during periods of clinically stable graft function, recipient T‐cell proliferation and cytokine secretion in response to stimulation with donor alloantigen was relatively suppressed. Therefore, although the TAIC‐II trial did not provide conclusive evidence of a beneficial effect of preoperative TAIC treatment, the results were encouraging because they suggest that TAICs promote a state of alloantigen‐specific unresponsiveness, which might allow safe minimization of pharmacological immunosuppression.

A clinically-feasible protocol for using human platelet lysate and mesenchymal stem cells in regenerative therapies

The transplantation of human stem cells seeded on biomaterials holds promise for many clinical applications in cranio-maxillo-facial tissue engineering and regenerative medicine. However, stem cell propagation necessary to produce sufficient cell numbers currently utilizes fetal calf serum (FCS) as a growth supplement which may subsequently transmit animal pathogens. Human platelet lysate (HPL) could potentially be utilized to produce clinical-grade stem cell-loaded biomaterials as an appropriate FCS substitute that is in line with clinically-applicable practice. The goal of this study was to investigate whether HPL can be successfully used to propagate human mesenchymal stem cells (HMSCs) seeded on clinically-approved collagen materials under clinically-applicable conditions using FCS as a control. HMSCs were isolated from bone marrow and cultured in the presence of 10% FCS or 10% HPL. Characterization of HMSCs was performed by flow cytometry and through osteogenic and adipogenic differentiation assays. Proliferative capacity of HMSCs on both matrices was investigated by mitochondrial dehydrogenase assays (WST) and tissue coverage scanning electron microscopy (SEM). The isolated HMSC differentiated into osteogenic and adipogenic cells authenticating the multipotentiality of the HMSCs. WST tests and the SEM images demonstrated that HPL was generally superior to FCS in promoting growth of seeded HMSCs. For all other tests HPL supported HMSCs at least equal to FCS. In conclusion, HPL is an effective growth factor to allow expansion of clinical-grade HMSCs on clinically-approved biomaterials for maxillofacial and oral implantology applications.

Establishment and optimization of a flow cytometric method for evaluation of viability of CD34+ cells after cryopreservation and comparison with trypan blue exclusion staining.

BACKGROUND:  Trypan blue exclusion staining is probably the most frequently applied method (Method I) for assessment of viability in peripheral blood progenitor cell grafts after cryopreservation. Alternatively, a flow cytometry–based method (Method II) was established and optimized.

Mimicking an Induced Self Phenotype by Coating Lymphomas with the NKp30 Ligand B7-H6 Promotes NK Cell Cytotoxicity

Induced self expression of the NKp30 ligand B7-H6 facilitates NK cell-mediated elimination of stressed cells. A fusion protein consisting of the ectodomain of B7-H6 and the CD20 single-chain fragment variable 7D8 was generated to mimic an induced self phenotype required for NK cell-mediated target cell elimination. B7-H6:7D8 had bifunctional properties as reflected by its ability to simultaneously bind to the CD20 Ag and to the NKp30 receptor. B7-H6:7D8 bound by CD20+ lymphoma cells activated human NK cells and triggered degranulation. Consequently, the immunoligand B7-H6:7D8 induced killing of lymphoma-derived cell lines as well as fresh tumor cells from chronic lymphocytic leukemia or lymphoma patients. B7-H6:7D8 was active at nanomolar concentrations in a strictly Ag-specific manner and required interaction with both CD20 and NKp30. Remarkably, NK cell cytotoxicity was further augmented by concomitant activation of Fcγ receptor IIIa or NK group 2 member D. Thus, B7-H6:7D8 acted synergistically with the CD20 Ab rituximab and the immunoligand ULBP2:7D8, which was similarly designed as B7-H6:7D8 but engaging the NK group 2 member D receptor. In conclusion, to our knowledge, B7-H6:7D8 represents the first Ab-based molecule stimulating NKp30-mediated NK cell cytotoxicity for therapeutic purposes and provides proof of concept that Ag-specific NKp30 engagement may represent an innovative strategy to enhance antitumoral NK cell cytotoxicity.

Increasing FcγRIIa affinity of an FcγRIII-optimized anti-EGFR antibody restores neutrophil-mediated cytotoxicity.

Antibody-dependent cell-mediated cytotoxicity (ADCC) has been suggested as an essential mechanism for the in vivo activity of cetuximab, an epidermal growth factor receptor (EGFR)-targeting therapeutic antibody. Thus, enhancing the affinity of human IgG1 antibodies to natural killer (NK) cell-expressed FcγRIIIa by glyco- or protein-engineering of their Fc portion has been demonstrated to improve NK cell-mediated ADCC and to represent a promising strategy to improve antibody therapy. However, human polymorphonuclear (PMN) effector cells express the highly homologous FcγRIIIb isoform, which is described to be ineffective in triggering ADCC. Here, non-fucosylated or protein-engineered anti-EGFR antibodies with optimized FcγRIIIa affinities demonstrated the expected benefit in NK cell-mediated ADCC, but did not mediate ADCC by PMN, which could be restored by FcγRIIIb blockade. Furthermore, eosinophils and PMN from paroxysmal nocturnal hemoglobinuria patients that expressed no or low levels of FcγRIIIb mediated effective ADCC with FcγRIII-optimized anti-EGFR antibody. Additional experiments with double FcγRIIa/FcγRIII-optimized constructs demonstrated enhanced PMN-mediated ADCC compared with single FcγRIII-optimized antibody. In conclusion, our data demonstrate that FcγRIIIb engagement impairs PMN-mediated ADCC activity of FcγRIII-optimized anti-EGFR antibodies, while further optimization of FcγRIIa binding significantly restores PMN recruitment.

Fusion proteins between ligands for NKG2D and CD20-directed single-chain variable fragments sensitize lymphoma cells for natural killer cell-mediated lysis and enhance antibody-dependent cellular cytotoxicity

Fusion proteins between ligands for NKG2D and CD20-directed single-chain variable fragments sensitize lymphoma cells for natural killer cell-mediated lysis and enhance antibody-dependent cellular cytotoxicity

The novel tribody [(CD20) 2 xCD16] efficiently triggers effector cell-mediated lysis of malignant B cells

Bispecific antibodies (bsab) offer a promising approach for optimizing antibody-based therapies. In the present study, [(CD20)2xCD16], a recombinant CD20- and CD16-directed bsab in the tribody format, was designed to optimize recruitment of FcγRIII (CD16)-positive effector cells. [(CD20)2xCD16] retained the antigen specificities of the parental monoclonal antibodies and binding to FcγRIIIa was not compromised by the F/V polymorphism at amino-acid position 158. [(CD20)2xCD16] mediated potent lysis of lymphoma cell lines and freshly isolated tumor cells from patients, even at low picomolar concentrations (∼10 pM). Irrespective of the CD16a allotype, potency as well as efficacy of lysis obtained with the tribody was significantly higher than lysis triggered by rituximab. Tumor cell killing also occurred when autologous NK cells were used as effector cells. Compared with rituximab, the tribody demonstrated depletion of autologous B cells in ex vivo whole blood assays at 100-fold lower antibody concentration. In mice with a reconstituted humanized hematopoietic system, established by transplantation of human CD34-positive cord blood cells, this novel tribody significantly depleted autologous human B cells. Thus, tribodies such as [(CD20)2xCD16], recruiting CD16-positive effector cells, may represent promising candidates for clinical development.

The Fc-engineered CD19 antibody MOR208 (XmAb5574) induces natural killer cell-mediated lysis of acute lymphoblastic leukemia cells from pediatric and adult patients

The Fc-engineered CD19 antibody MOR208 (XmAb5574) induces natural killer cell-mediated lysis of acute lymphoblastic leukemia cells from pediatric and adult patients