A randomized, open-label, multicenter, phase II study evaluating the efficacy and safety of BTH1677 (1,3-1,6 beta glucan; Imprime PGG) in combination with cetuximab and chemotherapy in patients with advanced non-small cell lung cancer

Introduction BTH1677, a 1,3–1,6 beta-glucan immunomodulator, stimulates a coordinated anti-cancer immune response in combination with anti-tumor antibody therapies. This phase II study explored the efficacy, pharmacokinetics (PK), and safety of BTH1677 combined with cetuximab/carboplatin/paclitaxel in untreated stage IIIB/IV non-small cell lung cancer (NSCLC) patients. Methods Patients were randomized 2:1 to the BTH1677 arm (N=60; BTH1677, 4 mg/kg, weekly; cetuximab, initial dose 400 mg/m² and subsequent doses 250 mg/m², weekly; carboplatin, 6 mg/mL/min AUC (area-under-the-curve) by Calvert formula, once each 3-week cycle [Q3W]); and paclitaxel, 200 mg/m², Q3W) or Control arm (N=30; cetuximab/carboplatin/paclitaxel as above). Carboplatin/paclitaxel was discontinued after 4–6 cycles; patients who responded or remained stable received maintenance therapy with BTH1677/cetuximab (BTH1677 arm) or cetuximab (Control arm). Investigator and blinded central radiology reviews were conducted. Efficacy assessments included objective response rate (ORR; primary endpoint), disease control rate, duration of objective response, time-to-progression and overall survival (OS); safety was assessed by adverse events (AEs). Potential biomarker analysis for BTH1677 response was also conducted. Results Compared to control treatment, the addition of BTH1677 numerically increased ORR by both investigator (47.8% vs 23.1%; p=0.0468) and central (36.6% vs 23.1%; p=0.2895) reviews. No other endpoints differed between arms. PK was consistent with previous studies. BTH1677 was well tolerated, with AEs expected of the backbone therapy predominating. Biomarker-positive patients displayed better ORR and OS than negative patients. Conclusions BTH1677 combined with cetuximab/carboplatin/paclitaxel was well tolerated and improved ORR as first-line treatment in patients with advanced NSCLC. Future patient selection by biomarker status may further improve efficacy

ClinicalTrials.gov Identifier: NCT00874848

Treatment of malignant pleural effusion with the trifunctional antibody catumaxomab (anti-EpCAM x anti-CD3): Results of a phase I/II study

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Background: The trifunctional antibody catumaxomab specifically binds EpCAM+ tumor cells, CD3+ T lymphocytes and accessory cells via the Fcγ RI/III. Thus the antibody induces tumor specific cell mediated cytotoxicity in vitro and in vivo. Its intraperitoneal administration has demonstrated safety and led to efficient tumor cell killing and reduction of malignant ascites in ovarian cancer patients (pts.). The present study was conducted to evaluate safety, tolerability and preliminary efficacy of catumaxomab administered intrapleurally (i.pl.) into pts. with EpCAM+ malignant pleural effusion. Methods: This phase I/II trial was a multi-center uncontrolled, dose-escalating study. Pts. (ECOG ≤3) with recurrent malignant pleural effusion containing EpCAM+ tumor cells were included. Three escalating doses from 5–200 μg catumaxomab were administered i.pl. Primary objectives were toxicity and definition of the maximum tolerated dose (MTD). In addition, preliminary data on efficacy (reduction of pleural fluid and tumor cell killing) were generated. Results: 13/24 pts. received 3 infusions as planned. Reasons for early termination of infusions were 3 deteriorations of performance status, 2 exanthemas, 2 dyspnoea, 2 others. The dose regimen of 20–50–100 μg catumaxomab was defined as MTD. Most frequent drug related AEs were symptoms of cytokine release syndrome. 32 SAEs were reported in 18 pts., 4 SAEs were possibly drug related (1 death due to pleural empyema, 1 pneumonia, 1 erythema, 1 increase of liver enzymes). 8/9 deaths were not drug related but due to underlying disease. Induction of human-anti-mouse (HAMA) or human-anti-rat (HARA) antibodies after treatment was found in 8/11 pts. 8/13 fully treated pts. were defined as responders (1 complete, 4 partial, 3 NA) showing reduction of effusion and of drainage necessity. 5/13 were non-responders. A reduction of tumor cells up to log 5 was seen in 10/13 pts. Conclusions: 20–50–100 μg of catumaxomab can safely be administered i. pl. This regimen will further be investigated in a randomized phase II trial comparing catumaxomab to talcum-based pleurodesis.

[Table: see text]

Constitutive activation of the MAPkinase p38 is critical for MMP-9 production and survival of B-CLL cells on bone marrow stromal cells

In the present work we investigated the role and biological significance of mitogen activated protein kinases (MAPK) in B-cell chronic lymphocytic leukaemia (B-CLL). The MAPK p38 was constitutively activated in B-CLL, but not in normal peripheral B cells. In addition, we demonstrated that the upstream kinases of p38, MKK3/6 were also constitutively activated in B-CLL cells. Furthermore, we determined by EMSA that the p38 MAP kinase pathway was not linked to the constitutive high expression of NF-kappaB, a critical survival factor of B-CLL cells. Recently, it has been shown that serum levels of angiogenic factors like VEGF, bFGF and MMP-9 are elevated in the serum of CLL patients and correlate with an unfavorable prognosis. We showed that the constitutive expression of MMP-9 was dependent on p38-activity and inhibition of p38 strongly downregulated MMP-9 expression. Coculture of B-CLL cells and stromal cells can protect spontaneous apoptosis of leukemic B cells. To determine the role of permanently activated p38 and MMP-9 expression, we cocultured B-CLL cells with bone marrow stromal cells. Survival of B-CLL cells on stroma was severely impaired when p38 was inhibited. Furthermore, blockade of MMP-9 activity also antagonized the antiapoptotic effect of stromal cells.

An open label, non-comparative phase II study of topotecan as salvage treatment for patients with soft tissue sarcoma

BACKGROUND

The number of effective cytotoxic agents for the treatment of patients with metastatic soft tissue sarcoma (STS) is limited, especially when patients have failed anthracyline-based chemotherapy.

PATIENTS AND METHODS

Between 1999 and 2000 a total of 16 patients with histologically proven STS progressing during or after first-line anthracycline-based chemotherapy were entered into this open-label, noncomparative study. Topotecan was administered as a 30-min infusion at a dosage of 1.5 mg/m(2) on five consecutive days every 3 weeks. All patients had received an anthracycline- or ifosfamide-based first-line chemotherapy.

RESULTS

None of the 16 included patients achieved an objective response to topotecan. Six patients achieved stable disease (38%), lasting for at least 6 weeks in four patients (25%) and for less than 6 weeks in two patients (13%). Ten patients (62%) had progressive disease. The median time to progression was 79 days calculated from the start of topotecan therapy (range, 28-230). The treatment was well tolerated; however, both anemia and thrombopenia grade III/IV occurred in 25% of the patients as well as severe neutropenia in 69% of the patients. Nonhematologic toxicities grade III/IV such as diarrhea and severe bleeding occurred only in one patient each (6%).

DISCUSSION

Topotecan is well tolerated in anthracycline-resistant patients with metastatic STS, but no objective response has been observed in this trial.

Cyclin-dependent kinase inhibitor Roscovitine induces apoptosis in chronic lymphocytic leukemia cells

A new class of cell cycle inhibitors is currently entering clinical trials. These drugs exert their activity by inhibition of cyclin-dependent kinases (cdk) and induce cell cycle arrest and apoptosis in cancer cells. Roscovitine, a cdk2-inhibitor that is in preclinical evaluation, induced apoptosis in B-CLL cells at doses that were not cytotoxic for normal human B cells. At 20 microM, Roscovitine induced apoptosis in 21 of 28 B-CLL samples and was equally effective in zap-70-positive or -negative samples. Caspase-3 was cleaved in B-CLL cells exposed to Roscovitine and the pancaspase inhibitor z.VAD.fmk-blocked Roscovitine-induced apoptosis. Expression of the proapoptotic protein Bak was increased and Bax cleavage and conformational change was observed in Roscovitine-treated B-CLL cells. Antiapoptotic proteins Mcl-1 and XIAP were downregulated, but the expression of Bcl-2 remained unchanged. In contrast to previous reports in cancer cell lines, Roscovitine treatment was not accompanied by nuclear accumulation of p53. Cyc202 (R-Roscovitine) is in early clinical trials in cancer patients. Given its powerful effects on zap-70-positive and -negative B-CLL cells, but not on normal lymphocytes, Roscovitine might be an attractive drug to be tested in this incurable disease.

Dynamics of BCR-ABL mRNA expression in first-line therapy of chronic myelogenous leukemia patients with imatinib or interferon α/ara-C

We sought to determine dynamics of BCR-ABL mRNA expression levels in 139 patients with chronic myelogenous leukemia (CML) in early chronic phase, randomized to receive imatinib (n=69) or interferon (IFN)/Ara-C (n=70). The response was sequentially monitored by cytogenetics from bone marrow metaphases (n=803) and qualitative and quantitative RT-PCR from peripheral blood samples (n=1117). Complete cytogenetic response (CCR) was achieved in 60 (imatinib, 87%) vs 10 patients (IFN/Ara-C, 14%) after a median observation time of 24 months. Within the first year after CCR, best median ratio BCR-ABL/ABL was 0.087%, (imatinib, n=48) vs 0.27% (IFN/Ara-C, n=9, P=0.025). BCR-ABL was undetectable in 25 cases by real-time PCR, but in only four patients by nested PCR. Median best response in patients with relapse after CCR was 0.24% (n=3) as compared to 0.029% in patients with continuous remission (n=52, P=0.029). We conclude that (i) treatment with imatinib in newly diagnosed CML patients is associated with a rapid decrease of BCR-ABL transcript levels; (ii) nested PCR may reveal residual BCR-ABL transcripts in samples that are negative by real-time PCR; (iii) BCR-ABL transcript levels parallel cytogenetic response, and (iv) imatinib is superior to IFN/Ara-C in terms of the speed and degree of molecular responses, but residual disease is rarely eliminated.

Cell cycle progression of chronic lymphocytic leukemia cells is controlled by cyclin D2, cyclin D3, cyclin-dependent kinase (cdk) 4 and the cdk inhibitor p27

B-CLL cells are arrested in G0/early G1 phase of the cell cycle and are characterized by a marked hyporesponsiveness towards a variety of polyclonal B cell activators. We have previously demonstrated that costimulation with CpG-ODN and IL-2 can overcome this proliferative defect. Cyclin D3 is the principal D-type cyclin which mediates G1 progression in normal B cells, but in B-CLL cells both cyclin D2 and cyclin D3, were strongly upregulated upon stimulation. Both cyclins were associated with cdk4 but not with cdk6, which is the catalytic partner of D-type cyclins in normal B cells. Moreover, immune complexes consisting of cyclin D2 and cdk4 or cyclin D3 and cdk4 were both functional and phosphorylated the RB protein in vitro. The cell cycle inhibitor p27 plays a pivotal role in cell cycle progression of B lymphocytes and has been shown to be overexpressed in B-CLL cells. P27 was rapidly downregulated in B-CLL cells even when stimulated with a non-CpG-ODN or IL-2 alone, while only moderate regulation could be observed in normal B cells. Taken together, our findings demonstrate that regulation of early cell cycle progression differs between B-CLL cells and normal B cells. These findings do not only contribute to the understanding of B-CLL pathophysiology, but might ultimately lead to the identification of new therapeutic targets.

Immunostimulatory CpG-oligonucleotides induce functional high affinity IL-2 receptors on B-CLL cells: costimulation with IL-2 results in a highly immunogenic phenotype

OBJECTIVE

CpG-oligodeoxynucleotides (CpG-ODN) have been shown to induce proliferation, cytokine production, and surface molecule regulation in normal and malignant human B cells. In the present study, we investigated the potential of CpG-ODN to induce functional high-affinity receptors in leukemic and normal B cells and the effects of costimulation with IL-2 on proliferation, cytokine secretion, and surface molecule regulation.

METHODS

Highly purified B cells from B-CLL patients and normal controls were stimulated with CpG-ODN with or without IL-2. Expression of CD25 was determined using FACS, and the presence of high-affinity IL-2 receptors was determined by scatchard analysis. Costimulatory effects of IL-2 and CpG-ODN were investigated using proliferation assays, ELISA (IL-6, TNF-alpha), and FACS analysis (CD80, CD86 expression). Reactivity of autologous and allogeneic T cells toward activated B-CLL cells was determined in mixed lymphocyte reactions and Interferon-gamma Elispot assays.

RESULTS

The CpG-ODN DSP30 caused a significantly stronger induction of the IL-2 receptor alpha chain in malignant as compared with normal B cells (p = 0.03). This resulted in the expression of functional high-affinity IL-2 receptors in B-CLL cells, but fewer numbers of receptors with less affinity were expressed in normal B cells. Although addition of IL-2 to CpG-ODN-stimulated cells augmented proliferation in both normal B cells and B-CLL cells, no costimulatory effect on cytokine production or surface molecule expression could be observed in normal B cells. In contrast, TNF-alpha and IL-6 production was increased in B-CLL cells, and the expression of CD80 and CD86 was further enhanced when IL-2 was used as a costimulus. Autologous and allogeneic immune recognition of B-CLL cells stimulated with CpG-ODN and IL-2 was increased compared with B-CLL cells stimulated with CpG-ODN alone.

CONCLUSION

Stimulation of B-CLL cells with CpG-ODN and IL-2 might be an attractive strategy for potential immunotherapies for B-CLL patients.

Immunostimulatory CpG-oligonucleotides cause proliferation, cytokine production, and an immunogenic phenotype in chronic lymphocytic leukemia B cells

Bacterial DNA and synthetic CpG-oligodeoxynucleotides (ODNs) derived thereof have attracted attention because they activate cells of the immune system in a sequence-dependent manner. Here we investigated the potential of CpG-ODNs to cause proliferation, cytokine production, and regulation of surface molecules in human B-chronic lymphocytic leukemia (CLL) cells. CpG-ODN induced proliferation in both B-CLL cells and normal B cells; however, only B-CLL cells increased proliferative responses when CpG-ODN was added to co-cultures of CD40-ligand transfected mouse fibroblasts (CD40LF) and B cells. Production of interleukin-6 and tumor necrosis factor alpha was detectable at borderline levels, using CpG-ODN as the only stimulus. In contrast, when CpG-ODN was added to co-cultures of B cells and CD40LF, a strong increase in cytokine production occurred in B-CLL cells as well as in normal B cells. The surface molecules CD40, CD58, CD80, CD86, CD54, and MHC class I molecules were up-regulated in B-CLL cells, whereas CD95 expression was not influenced by CpG-ODN stimulation. The same pattern of surface molecule regulation was observed in normal B cells, but up-regulation of CD40 was significantly stronger in B-CLL cells. Costimulation with CpG-ODN and CD40LF resulted in further up-regulation of CD58, CD80, CD86, and MHC class I molecules. In contrast, CD95 expression induced by CD40-ligation was inhibited by CpG-ODN. CpG-ODN activated B-CLL cells acquired a strong stimulatory capacity toward T cells in allogeneic mixed lymphocyte reaction. This effect was completely inhibited by a combination of anti-CD80 and anti-CD86 monoclonal antibody. Taken together, these findings suggest the possible use of CpG-ODN for immunotherapeutic strategies in patients with B-CLL.

Thrombotic thrombocytopenic purpura in metastatic carcinoma of the breast

We present a case of a 52-year-old woman with thrombotic thrombocytopenic purpura associated with progressive metastatic adenocarcinoma of the breast. The patient received plasma exchange therapy. Thrombocytopenic purpura resolved 2 months after discontinuation of plasma exchange while the patient received chemotherapy. After 3 more months, a fulminant relapse of the thrombocytopenic purpura developed, and there were signs of tumor progression. She died despite adequate treatment. We conclude that effective treatment of the underlying tumor can be crucial to control cancer-associated thrombocytopenic purpura.

IFN-alpha stimulates proliferation and cytokine secretion of CD40-stimulated B cell chronic lymphocytic leukemia cells in vitro

Interferon (IFN)-alpha has a therapeutic effect in several B cell malignancies, including low-grade non-Hodgkin's lymphoma (NHL), multiple myeloma, and hairy cell leukemia, whereas its efficacy in the treatment of B cell chronic lymphocytic leukemia (B-CLL) is rather limited. In the present study, we investigated the effect of IFN-alpha on the biologic functions of B-CLL cells, which were stimulated by cross-linking of the CD40 antigen. In cell samples from 16 B-CLL patients, the addition of IFN-alpha to CD40-stimulated purified B-CLL cells caused a significant increase in [3H]thymidine uptake (p < 0.003). In B-CLL cells maximally activated by CD40 cross-linking and interleukin-2 (IL-2)/IL-10, proliferation was not further enhanced or inhibited by IFN-alpha. In contrast, proliferation of normal tonsillar B cells stimulated by the combination CD40/IL-2/IL-10 was significantly inhibited by IFN-alpha. Because B-CLL activation might be enhanced by induction of the autocrine growth factor tumor necrosis factor-alpha (TNF-alpha), we investigated the effect of IFN-alpha on the secretion of B cell tropic cytokines. In fact, IFN-alpha significantly stimulated the secretion of IL-6 and TNF-alpha in CD40-activated B-CLL cells (p < 0.01). Although exogenous addition of TNF-alpha did not influence activation of CD40-stimulated B-CLL cells, neutralization of TNF-alpha by polyclonal antibodies led to a complete inhibition of CD40-mediated proliferation of B-CLL cells, suggesting that enhanced proliferation and increased cytokine production by CD40-activated B-CLL cells are independent IFN-alpha-mediated events. The studies presented here provide evidence that IFN-alpha mediates costimulatory signals in the context of T cell-mediated B-CLL cell activation.

Autocrine transforming growth factor-beta from chronic lymphocytic leukemia-B cells interferes with proliferative T cell signals

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of noncycling B cells in lymphatic and extralymphatic tissues. In the present study we investigated the possible contribution of TGF-beta, as secreted by CLL-B cells, on this low proliferative state. CLL-B cells were shown to express TGF-beta RNA and to release bioactive TGF-beta into culture supernatants. Antibody neutralization of endogenously secreted TGF-beta increased the proliferation of CLL-B cells as cultured in the presence of IL-2 or IL-4 or in direct contact with activated CD4+ T cells. In these culture systems, addition of exogenous TGF-beta downregulated basal and cytokineinduced proliferation of CLL-B cells. In contrast, neither neutralization of endogeneous TGF-beta, nor addition of exogeneous TGF-beta changed the proliferation of CLL-B cells as cultured in the CD40 system. In order to further explore this differential antiproliferative effect of TGF-beta, cytokine secretion of B cells and of CD4+ T cells as well as surface marker expression of CD4+ T cells were assessed in relation to TGF-beta: There was no negative effect of TGF-beta on autocrine secretion of TNF-alpha or sCD23 by CLL-B cells. Unlike tonsillar B cells, CLL-B cells cultured alone or in the CD40 system did no release significant amounts of IL-6 or IL-8 into supernatants. Secretion of IL-2 or IL-4 by activated CD4+ T cells was higher, when T cells were cocultured with normal tonsillar B cells than with CLL-B cells. The amount of IL-2 or IL-4 released by CD4+ T cells cocultured in direct contact with tonsillar or CLL-B cells was not consistently influenced either by neutralization of endogenous TGF-beta or by addition of TGF-beta. Exogenous TGF-beta did not downregulate expression of CD40L, CD27, CD28, CD54 or mTNF-alpha by T helper cells activated with anti-CD3 or PHA. In conclusion, autocrine secretion of TGF-beta exhibits an antiproliferative effect on CLL-B cells. This effect is most relevant in B cells cultured in direct contact with activated CD4+ T cells suggesting an indirect mode of action.

Idarubicin and intermediate-dose cytarabine for myeloid blast crisis of chronic myelogenous leukemia--results of a phase-II trial

Sixteen patients with Philadelphia chromosome-positive chronic myelogenous leukemia (CML) in myeloid blast crisis were treated with cytarabine (AraC) 600 mg/m2 two times daily for 5 days and idarubicin 12 mg/m2 for 3 days. Patients achieving a second chronic phase received interferon (IFN) alpha 2b 5 mio units/day daily and AraC 20 mg/day subcutaneously 14 days every month. Study end points were remission rate and survival. Four patients (25%) entered a second chronic phase and had a median survival of 31.1 weeks (range 16.1-111 weeks). Nine patients (56%) experienced blast crisis again and had a median survival of 12.9 weeks (range 5.1-59.3 weeks). Three patients (18.8%) died of septic complications during marrow aplasia. The median overall survival was 16.1 weeks (range 2.6-111 weeks) with no significant difference between responders and nonresponding patients. We conclude that AraC/idarubicin is as effective as other intensive regimens in inducing second chronic phase in patients with myeloid blast crisis of CML. Remission duration and survival are comparable to previous results. Further studies to improve survival are required.

Direct cellular interaction with activated CD4(+) T cells overcomes hyporesponsiveness of B-cell chronic lymphocytic leukemia in vitro

The proliferative response of clonal B cells from patients with chronic lymphocytic leukemia (B-CLL) is drastically reduced compared to normal B lymphocytes stimulated via the B cell antigen receptor complex or by CD40 ligation. In the present study we demonstrate that hyporesponsiveness of CLL-B cells can be overcome by stimulatory pathways mediated by activated CD4(+) T cells. In contrast to CD40 ligation, costimulation with activated T cells promotes a proliferative response in CLL-B cells identical to that in normal B cells. Furthermore, coculture with activated T cells improved survival of CLL-B cells in vitro. Differentiation of CLL-B cells into IgM producing cells was promoted, as well. However, the capacity for IgM secretion remained impaired compared to that of normal B cells. For T-cell-mediated B cell activation direct cellular contact with activated T helper cells is absolutely required. Prevention of CD40/CD40L interaction by CD40 antibody caused only partial inhibition of B cell activation, suggesting that additional signals are involved in T-B cell interaction. Whereas interruption of the ligand pairs CD11a/CD54, CD5/CD72, CD27/CD70 had no influence, the addition of CD58 antibody completely inhibited B cell activation by activated T cells. In costimulation with cellular signals the presence of B-cell-tropic cytokines, such as IL-2 and IL-4, was required to optimize B-CLL proliferation, as demonstrated by the use of neutralizing antibodies. We conclude from these results that proliferative hyporesponsiveness by CLL-B cells can be circumvented by antigen-nonspecific signals in addition to CD40 which are mediated by direct contact with activated T helper cells.

Immunomodulatory and hematopoietic effects of recombinant human interleukin-6 in patients with advanced renal cell cancer

Interleukin-6 (IL-6) is a cytokine with pleiotropic biologic activities on B cells, T cells, and hematopoietic progenitors. The present study was undertaken to assess pharmacodynamic effects of subcutaneous administration of IL-6 on blood counts, immunologic parameters, and acute-phase reactants. Blood samples were taken from patients with advanced renal cell cancer participating in a phase II trial of recombinant human IL-6. Multiparameter FACS analyses of peripheral blood mononuclear cells were performed using antibodies against CD3, CD4, CD8, HLA-DR, CD56, CD28, CD38, CD19, sIgM, and sIgG. Serum levels of IL-10, soluble CD23 (sCD23), sCD25, IL-1 receptor antagonist protein (IL-1RA), soluble tumor necrosis factor (TNF) receptors (sTNF-R) p55 and p75, and soluble IL-6 receptor (sIL-6R) were detected by ELISA systems. Levels of C-reactive protein (CRP), neopterin, fibrinogen, beta 2-microglobulin, and immunoglobulins M, G, and A were measured by standard methods. In response to administration of IL-6, a significant increment in platelet counts was observed, reaching peak levels after 21 days of treatment. In contrast, leukocyte subsets remained unaffected. No change in number of immunophenotype of peripheral blood B cells, T cells, or natural killer cells could be detected following IL-6 administration. Blood levels of sCD23, IL-10, sIL-6R, neopterin, beta 2-microglobulin, and immunoglobulin subsets were not influenced by cytokine therapy. However, administration of IL-6 led to a slow increment of acute-phase reactants CRP and fibrinogen. Furthermore, the anti-inflammatory molecules sTNF-R p55 and p75 were induced by IL-6, whereas serum levels of IL-1RA remained unchanged. Finally, an increase in blood levels of sCD25 was observed. In conclusion, IL-6 in vivo predominantly acts as a regulator of inflammation and a megakaryocyte differentiation factor.

Preliminary results of stem cell mobilization in chronic myeloid leukemia with a moderate intensity chemotherapy regimen and G-CSF or G-CSF plus IL-3

Mobilization of Philadelphia chromosome (Ph) negative peripheral blood stem cells has been reported subsequent to intensive chemotherapy. We asked whether peripheral blood stem cells can be harvested subsequent to a less toxic chemotherapy regimen. Patients were treated with idarubicin 12 mg/m2 on day 1 and 2 and ara-C 100 mg/m2 days 1-5 and 5 or 10 micrograms/m2 G-CSF. In case of insufficient yield chemotherapy was repeated using IL-3 and G-CSF for mobilization of stem cells. Fourteen patients received 18 cycles of chemotherapy. The majority of patients were in late chronic phase and treated after secondary (interferon-alpha) IFN-alpha resistance. sufficient numbers of peripheral blood stem cells were harvested in 11 out of 14 patients. Although mixed Ph positive/Ph negative leukaphereses were harvested in the majority of patients, in no case were sufficient numbers of purely Ph negative progenitor cells for transplantation obtained. No toxic deaths were observed during the aplasia and the toxicity was acceptable. These preliminary results demonstrate that this procedure can be safely applied in patients with chronic phase CML and allows the harvesting of sufficient numbers of peripheral blood stem cells. The efficacy of this regimen for the mobilization of Ph negative cells should be further explored in patients at an earlier stage of the disease.

Biotherapy of chronic myelogenous leukemia

The aim of this review is to summarize the current knowledge on the clinical results of biotherapy of chronic myelogenous leukemia (CML) and potential mechanisms of the antitumor action of interferon alpha. IFN alpha treatment induces hematologic and cytogenetic remissions in patients with chronic phase CML. In addition, the duration of the chronic phase is prolonged by IFN alpha resulting in a significant survival benefit. In two randomized clinical trials this survival benefit was demonstrated in all chronic phase CML patients independent of their risk scores. Moreover, IFN treatment also delays the onset of clinical relapse after allogeneic bone marrow transplantation. The critical mechanisms of IFN action have not yet been identified. Both direct and indirect antiproliferative mechanisms have been described. In particular, differential regulation of growth promoting and growth inhibiting cytokines represents an attractive hypothetical mechanism of IFN action. Nevertheless, no leukemia specific IFN activities explaining cytogenetic remissions and/or delay of disease progression have been identified. Further research on that field are required to further improve biological CML therapies.