The novel immunotoxin HM1.24-ETA' induces apoptosis in multiple myeloma cells.

Despite new treatment modalities, the clinical outcome in a substantial number of patients with multiple myeloma (MM) has yet to be improved. Antibody-based targeted therapies for myeloma patients could make use of the HM1.24 antigen (CD317), a surface molecule overexpressed on malignant plasma cells and efficiently internalized. Here, a novel immunotoxin, HM1.24-ETA', is described. HM1.24-ETA' was generated by genetic fusion of a CD317-specific single-chain Fv (scFv) antibody and a truncated variant of Pseudomonas aeruginosa exotoxin A (ETA'). HM1.24-ETA' inhibited growth of interleukin 6 (IL-6)-dependent and -independent myeloma cell lines. Half-maximal growth inhibition was observed at concentrations as low as 0.3 nM. Target cell killing occurred via induction of apoptosis and was unaffected in co-culture experiments with bone marrow stromal cells. HM1.24-ETA' efficiently triggered apoptosis of freshly isolated/cryopreserved cells of patients with plasma cell leukemia and MM and was active in a preclinical severe combined immunodeficiency (SCID) mouse xenograft model. Importantly, HM1.24-ETA' was not cytotoxic against CD317-positive cells from healthy tissue (monocytes, human umbilical vein endothelial cells). These results indicate that CD317 may represent a promising target structure for specific and efficient immunotoxin therapy for patients with plasma cell tumors.

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)(2)xCD16], a recombinant CD20- and CD16-directed bsab in the tribody format, was designed to optimize recruitment of FcγRIII (CD16)-positive effector cells. [(CD20)(2)xCD16] 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)(2)xCD16] 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)(2)xCD16], recruiting CD16-positive effector cells, may represent promising candidates for clinical development.

Human kappa light chain targeted Pseudomonas exotoxin A--identifying human antibodies and Fab fragments with favorable characteristics for antibody-drug conjugate development.

Antibody-drug conjugates (ADC) represent promising agents for targeted cancer therapy. To allow rational selection of human antibodies with favorable characteristics for ADC development a screening tool was designed obviating the need of preparing individual covalently linked conjugates. Therefore, α-kappa-ETA' was designed as a fusion protein consisting of a human kappa light chain binding antibody fragment and a truncated version of Pseudomonas exotoxin A. α-kappa-ETA' specifically bound to human kappa light chains of human or human-mouse chimeric antibodies and Fab fragments. Antibody-redirected α-kappa-ETA' specifically inhibited proliferation of antigen-expressing cell lines at low toxin and antibody concentrations. Selected antibodies that efficiently delivered α-kappa-ETA' in the novel assay system were used to generate scFv-based covalently linked immunotoxins. These molecules efficiently triggered apoptosis of target cells, indicating that antibodies identified in our assay system can be converted to functional immunoconjugates. Finally, a panel of human epidermal growth factor receptor (EGFR) antibodies was screened--demonstrating favorable characteristics with antibody 2F8. These data suggest that antibodies with potential for Pseudomonas exotoxin A-based ADC development can be identified using the novel α-kappa-ETA' conjugate.

Crescentic glomerulonephritis associated with myeloperoxidase-antineutrophil-cytoplasmic antibodies: first report on the efficacy of primary anti-TNF-alpha treatment.

We report on successful induction of remission in a patient with necrotizing crescentic glomerulonephritis associated with myeloperoxidase-antineutrophil-cytoplasm antibodies by primary use of the anti-tumor necrosis factor (TNF)-alpha chimeric monoclonal antibody infliximab in combination with corticosteroids only. The standard treatment containing cyclophosphamide has reduced the former high mortality from systemic vasculitides. However, the toxicity of this alkylating agent limits its long-term use. As TNF-alpha has been shown to play a central pathogenic role in vasculitis as well as in crescentic glomerulonephritis, anti-TNF-alpha treatment in combination with cyclophosphamide has been found to be effective in therapy-resistant vasculitis. Previous reports on TNF-alpha-blocking therapies without additional cyclophosphamide did not include patients with active and severe crescentic glomerulonephritis. As our patient refused cyclophosphamide, he was given four infusions of infliximab (4 mg/kg on weeks 0, 2, 6 and 10) and methylprednisolone pulses (1 g on days 1-3), followed by daily oral prednisolone (starting with 2 mg/kg and tapering down to 5 mg daily within 3 months). After 12 weeks, control biopsy demonstrated lack of active glomerular inflammation while initially reduced renal function (creatinine 271 versus 172 mol/l, clearance 26 versus 62 ml/min) and proteinuria (2.4 versus 1.0 g/d) improved. Under remission maintenance therapy with azathioprine and prednisolone, the patient showed no relapses during a 1-year follow-up. Finally we demonstrate that there might be patients with crescentic glomerulonephritis who do not require therapy with alkylating substances and that less toxic agents such as the TNF-alpha-blocking monoclonal antibody infliximab could play a role in future primary treatment of crescentic glomerulonephritis.

[Significance and scope of interdisciplinary cooperation in the specialty of internal medicine (inpatients)]. / Bedeutung und Umfang der interdisziplinären Zusammenarbeit im Fachgebiet Innere Medizin (stationär).

In a department of internal medicine of a district hospital all consultations given by representatives of non-internal medical specialties and by specialized or highly specialized representatives of the subject of internal medicine in a period of five months were registered. In 29% of all patients attended in the period of observation consultation achievements were demanded. 65% of these achievements could be realized by physicians working in hospitals or outpatient departments of the district. 23% of the consultations were carried out by specialists from institutions conducted by county authorities. 11% of the consultations were carried out by highly specialized physicians of university clinics and academy institutes. The investigation confirms the high significance of the inter-disciplinary cooperation for the subject of internal medicine. cooperation for the subject of internal