High efficacy of combined rituximab and gemcitabine on Epstein–Barr virus-associated human B-cell lymphoma obtained after Hodgkin's xenograft in immunodeficient mice

Pixantrone-rituximab versus gemcitabine-rituximab in relapsed/refractory aggressive non-Hodgkin lymphoma

We describe the rationale and design of the ongoing randomized, active-controlled, multicenter, Phase III study evaluating the efficacy of pixantrone and rituximab versus gemcitabine and rituximab in patients with diffuse large B-cell lymphoma or follicular grade 3 lymphoma, who are ineligible for high-dose chemotherapy and stem cell transplantation, and who failed front-line regimens containing rituximab. The administration schedule is pixantrone 50 mg/m(2) intravenously (iv.) or gemcitabine 1000 mg/m(2) iv. on days 1, 8 and 15, combined with rituximab 375 mg/m(2) iv. on day 1, up to six cycles. Pixantrone has a conditional European marketing approval for monotherapy in adults with multiple relapsed or refractory aggressive B-cell non-Hodgkin lymphoma. Our trial explores the efficacy of combining pixantrone with rituximab and completes postauthorization measures.

TRIAL REGISTRATION NUMBER

NCT01321541.

Rituximab in Hodgkin lymphoma: is the target always a hit?

In 1997, the anti-CD20 monoclonal antibody (MAb) rituximab became the first MAb approved for clinical use in oncology, and ushered in a new era of rationally designed targeted agents in cancer therapeutics. It is currently approved for use in non-Hodgkin lymphoma (NHL), chronic lymphoid leukemia (CLL), and rheumatoid arthritis (RA). Rituximab is non-mutagenic, associated with low treatment-related toxicity, and few, if any, long term adverse events, making it an attractive agent to be tried in off-label settings like Hodgkin lymphoma (HL). HL consists of two distinct subtypes - classic HL (cHL) and lymphocyte predominant HL (LPHL). CD20 is present in virtually all patients with LPHL, and in a significant minority of patients with cHL. In this CD20 positive sub-population, the use of rituximab is a rational intervention strategy. Rituximab has been used in patients with cHL as well as LPHL with good efficacy. In this article, we provide a clinically-oriented overview of the use of rituximab in the different sub-types of HL, and report updated results of our series of 8 LPHL patients treated with rituximab. A systematic review of the literature is also presented.

A multicenter study of gemcitabine-containing regimen in relapsed or refractory Hodgkin's lymphoma patients

The aim of this study was to assess the efficacy of a gemcitabine-containing regimen in pretreated Hodgkin's lymphoma (HL) patients. Relapsed or refractory HL patients treated with gemcitabine, used alone or in combination with other cytotoxic agents, were retrospectively reviewed. Fifty-five patients were included in the study. Initial characteristics before gemcitabine administration were: Ann Arbor stage III-IV: 84%; International Prognostic Score less than 3 in 18/39 cases (46%); 31 primary refractory patients at the end of first-line therapy (56%); median number of previous chemotherapy regimens of 3. Twenty-nine patients received gemcitabine alone with a median maximal dose of 900 mg/m2 per injection (range: 300-1500 mg/m2). Gemcitabine was administered at a maximal dose of 1000 mg/m2 per injection (range: 650-1250) in combination with vinorelbine in 10 patients, oxaliplatin in 13 patients, and other drugs in three patients, with a median of six injections (range: 1-18). Reported toxicity was mainly hematologic. Overall response rate was 20% with 11% of complete remission. On univariate analysis, two adverse factors at progression were significant for response to gemcitabine-based regimen: stage III-IV disease and hemoglobin level was less than 10.5 g/dl. This study demonstrated the limited efficacy of gemcitabine-containing regimen in heavily pretreated HL patients.

Imatinib mesylate reduces rituximab-induced tumor-growth inhibition in vivo on Epstein-Barr virus-associated human B-cell lymphoma

We have reported earlier an increase of tumor-growth inhibition following chemotherapy combined with concomitant administration of imatinib mesylate. Conversely, the combination of imatinib and rituximab has been reported in very few cases of patients and remains controversial. To explore this particular combination of targeted therapies, we therefore investigated the in-vivo impact of rituximab plus imatinib on B-cell lymphoproliferation. Combination of the tyrosine kinase inhibitor imatinib mesylate (STI571) and the anti-CD20 monoclonal antibody rituximab was evaluated on an Epstein-Barr virus-associated B-cell lymphoproliferative disorder xenografted into severe combined immunodeficient or Rag2/gammac-/- (B-, T- and NK-) mice. Using severe combined immunodeficient mice, we found that STI571 diminished the efficacy of rituximab to inhibit tumor growth in vivo. Using alymphoid Rag2/gammac-/- mice, we showed that the effect of STI571 was not dependent on the presence of natural killer cells. In contrast, serum complement administered after STI571 treatment reversed this inhibitory effect. Finally, using nonimmunodeficient mice, we observed an in-vivo decrease of CD4-positive T-cells and mature B-cell lymphocytes after imatinib administration. We found that STI571 decreased the in-vivo efficacy of rituximab via serum protein components that could influence complement-dependent cytotoxicity. In contrast, this effect was not dependent on the presence of natural killer cells.

Impact of imatinib on the pharmacokinetics and in vivo efficacy of etoposide and/or ifosfamide

Background

Using a human small cell lung cancer (SCLC) xenografted in nude mice, we have previously reported enhanced tumor growth inhibition following chemotherapy in combination with imatinib (STI571). We therefore investigated the in vivo impact of imatinib on the pharmacokinetics and efficacy of chemotherapy.

Methods

Two different human tumors were used: SCLC6 small cell lung cancer xenografted in nude mice, and LY-3 EBV-associated human B-cell lymphoma xenografted in SCID mice. Plasma, urine, and fecal concentrations of etoposide (VP16) were determined by a validated high performance liquid chromatography method. Plasma concentrations of ifosfamidewere determined by a validated gas chromatography assay with nitrogen-phosphorus detection.

Results

Slight tumor growth inhibition was induced by imatinib administered alone in one in vivo EBV-associated B-cell lymphomatous xenograft. In contrast, an increase of the chemotherapy-induced antitumor effect was observed in the lymphoma model but not in a small cell lung cancer model when mice bearing human xenografted tumors were treated concomitantly by imatinib and chemotherapy. This antitumor effect was not influenced by concomitant administration of fluconazole. The AUC0-3 h (Area Under the concentration-time Curve) of etoposide was increased when mice were treated with etoposide + imatinib due to decreased fecal excretion. In contrast, imatinib did not appear to influence the urinary excretion of etoposide, and concomitant administration of the CYP3A4 inhibitor, fluconazole, with imatinib did not modify the pharmacokinetics of etoposide plus imatinib alone.

Conclusion

Altogether, these results therefore justify further prospective phase I and II clinical trials with combinations of etoposide-based chemotherapy and imatinib in patients with certain cancers, such as malignant lymphoma, with careful toxicologic monitoring.

Targeting calcineurin activation as a therapeutic strategy for T-cell acute lymphoblastic leukemia

Calcineurin is a calcium-activated serine/threonine phosphatase critical to a number of developmental processes in the cardiovascular, nervous and immune systems. In the T-cell lineage, calcineurin activation is important for pre-T-cell receptor (TCR) signaling, TCR-mediated positive selection of thymocytes into mature T cells, and many aspects of the immune response. The critical role of calcineurin in the immune response is underscored by the fact that calcineurin inhibitors, such as cyclosporin A (CsA) and FK506, are powerful immunosuppressants in wide clinical use. We observed sustained calcineurin activation in human B- and T-cell lymphomas and in all mouse models of lymphoid malignancies analyzed. In intracellular NOTCH1 (ICN1)- and TEL-JAK2-induced T-cell lymphoblastic leukemia, two mouse models relevant to human malignancies, in vivo inhibition of calcineurin activity by CsA or FK506 induced apoptosis of leukemic cells and rapid tumor clearance, and substantially prolonged mouse survival. In contrast, ectopic expression of a constitutively activated mutant of calcineurin favored leukemia progression. Moreover, CsA treatment induced apoptosis in human lymphoma and leukemia cell lines. Thus, calcineurin activation is critical for the maintenance of the leukemic phenotype in vivo, identifying this pathway as a relevant therapeutic target in lymphoid malignancies.