Synergistic efficacy of dual PI3K-d/g inhibitor Duvelisib with Bcl2 inhibitor Venetoclax in Richter's Syndrome PDX models

Blood ◽  
2021 ◽  
Author(s):  
Andrea Iannello ◽  
Nicoletta Vitale ◽  
Silvia Coma ◽  
Francesca Arruga ◽  
Amy Chadburn ◽  
...  
Keyword(s):  
Ex Vivo ◽  
B Cell Lymphoma ◽  
Lymphocytic Leukemia ◽  
Tumor Growth Inhibition ◽  
Small Subset ◽  
Apoptotic Pathways ◽  
Novel Therapeutic Strategies ◽  
Pdx Models ◽  
Richter’S Syndrome

A small subset of cases of chronic lymphocytic leukemia undergoes transformation to diffuse large B-cell lymphoma, Richter's Syndrome (RS), which is associated with a poor prognosis. Conventional chemotherapy results in limited responses, underlining the need for novel therapeutic strategies. Here, we investigate the ex-vivo and in vivo efficacy of the dual PI3K-d/g inhibitor Duvelisib (Duv) and the Bcl-2 inhibitor Venetoclax (Ven) using four different RS-patient-derived xenograft (PDX) models. Ex-vivo exposure of RS cells to Duv, Ven or their combination results in variable apoptotic responses, in line with the expression levels of target proteins. While RS1316, IP867/17 and RS9737 cells express PI3K-d, PI3K-g and Bcl-2 and respond to the drugs, RS1050 cells, expressing very low levels of PI3K-g and lacking Bcl-2, are fully resistant. Moreover, the combination of these drugs is more effective than each agent alone. When tested in vivo, RS1316 and IP867/17 show the best tumor growth inhibition responses, with Duv/Ven combination leading to complete remission at the end of treatment. The synergistic effect of Duv and Ven relies on the crosstalk between PI3K and apoptotic pathways occurring at the GSK3β level. Indeed, inhibition of PI3K signaling by Duv results in GSK3β activation, leading to ubiquitination and subsequent degradation of both c-Myc and Mcl-1, making RS cells more sensitive to Bcl-2 inhibition by Ven. This work provides, for the first time, a proof-of-concept of the efficacy of dual targeting of PI3K-d/g and Bcl-2 in RS, opening for a Duv/Ven combination for these patients. Clinical studies in aggressive lymphomas, including RS, are underway (NCT03892044).

scholarly journals Ex Vivo Mitochondrial Respiration Parallels Biochemical Response to Ibrutinib in CLL Cells

Cancers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 354
Author(s):  
Subir Roy Chowdhury ◽  
Cheryl Peltier ◽  
Sen Hou ◽  
Amandeep Singh ◽  
James B. Johnston ◽  
...  
Keyword(s):  
Mitochondrial Respiration ◽  
Ex Vivo ◽  
Standard Dose ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Clinical Tool ◽  
Potential Biomarker ◽  
Apoptotic Pathways ◽  
The Impact

Mitochondrial respiration is becoming more commonly used as a preclinical tool and potential biomarker for chronic lymphocytic leukemia (CLL) and activated B-cell receptor (BCR) signaling. However, respiration parameters have not been evaluated with respect to dose of ibrutinib given in clinical practice or the effect of progression on ibrutinib treatment on respiration of CLL cells. We evaluated the impact of low and standard dose ibrutinib on CLL cells from patients treated in vivo on mitochondrial respiration using Oroboros oxygraph. Cytokines CCL3 and CCL4 were evaluated using the Mesoscale. Western blot analysis was used to evaluate the BCR and apoptotic pathways. We observed no difference in the mitochondrial respiration rates or levels of plasma chemokine (C-C motif) ligands 3 and 4 (CCL3/CCL4), β-2 microglobulin (β-2 M) and lactate dehydrogenase (LDH) between low and standard doses of ibrutinib. This may confirm why clinical observations of the safety and efficacy of low dose ibrutinib are observed in practice. Of interest, we also observed that the mitochondrial respiration of CLL cells paralleled the increase in β-2 M and LDH at progression. Our study further supports mitochondrial respiration as a biomarker for response and progression on ibrutinib in CLL cells and a valuable pre-clinical tool.

Triterpenoids Display Single Agent Activity in a Mouse Model of CLL/SBL.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2530-2530
Author(s):  
Christina L. Kress ◽  
Marina Konopleva ◽  
Maryla Krajewska ◽  
Vanesa Martinez-Garcia ◽  
Sophie Lefebvre ◽  
...  
Keyword(s):  
B Cells ◽  
Mouse Model ◽  
Drug Testing ◽  
Ex Vivo ◽  
Single Agent ◽  
B Cell Lymphoma ◽  
Lymphocytic Leukemia ◽  
Clinical Activity ◽  
Potent Inducer

Abstract The synthetic triterpenoid 2-Cyano-3,12-Dioxooleana-1,9-Dien-28-Oic Acid (CDDO) induces apoptosis of leukemia cells through a novel mechanism and has recently entered Phase I human clinical trials. We studied the effects of CDDO and its imidazolide derivative (CDDO-Im) on cultured human chronic lymphocytic leukemia (CLL) cells and on B cells from TRAF2DN/Bcl-2 transgenic mice, a new mouse model of CLL and small B cell lymphoma (SBL). Both triterpenoids efficiently induced death of malignant human and mouse B-cells ex vivo, although CDDO-Im was over 10-fold more potent than CDDO. Treating TRAF2DN/Bcl-2 mice that had developed leukemia with liposome-formulated CDDO or CDDO-Im resulted in significant reductions of B cells in blood, spleen and lung, with CDDO-Im more potent than CDDO, while treatment with empty liposomes had no impact on disease. Analysis of blood cells recovered from treated mice showed that CDDO-Im is a potent inducer of cell dead in vivo. Furthermore, CDDO-Im efficiently eradicated mouse CLL cells but had a lesser effect on the viability of normal B cells. These results demonstrate that triterpenoids CDDO and CDDO-Im reduce leukemia and lymphoma burden in vivo in a transgenic mouse model of CLL/SBL and suggest that CDDO-based synthetic triterpenoids should be tested for clinical activity in patients with CLL. Our results also provide evidence of the suitability of our mouse model of CLL/SBL as a preclinical platform for chemotherapeutic drug testing.

Discovery of HBW-3-10: A potent, orally active, reversible Bruton’s tyrosine kinase (BTK) inhibitor with antitumor activity in mice.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e15062-e15062
Author(s):  
Ning Lee ◽  
Yingfu Li ◽  
Chester Yuan ◽  
Guanfeng Liu ◽  
Chunchao Yue
Keyword(s):  
B Cell ◽  
Second Generation ◽  
Tumor Model ◽  
B Cell Lymphoma ◽  
Lymphocytic Leukemia ◽  
Tumor Growth Inhibition ◽  
Wild Type ◽  
Btk Inhibitor ◽  
Btk Inhibitors

e15062 Background: The first generation irreversible BTK inhibitor ibrutinib has been approved for the treatment of B cell-related diseases, including chronic lymphocytic leukemia (CLL), for several years. However, CLL patients who used ibrutinib may develop drug resistance due to acquired mutations, in particular BTK C481S that directly impacts the binding of ibrutinib. In recent years, efforts have been made to develop the second generation reversible BTK inhibitors that are effective against both wild-type and C481S mutated B-cell malignancies. LOXO-305 and ARQ-531 are two examples of the second generation reversible BTK inhibitors in advanced clinical trials for ibrutinib-resistant CLL. Methods: New reversible BTK inhibitors were designed, synthesized and tested for enzymatic activities against wild-type and C481S-mutated BTK. Highly active compounds were confirmed for growth effects in diffuse large B-cell lymphoma derived TMD8 cells. Their microsomal stability and ADME properties were also assessed. Potent and bioavailable compounds were further evaluated in vivo efficacy using a TMD8 xenograft tumor model in mice. A 14-day toxicity study in rats was performed correspondingly. Results: As shown in the table, HBW-3-10 has greater potency and pharmacokinetic profile (rats, 10mg/kg PO) than ARQ-531. In a TMD8 mouse xenograft study, HBW-3-10, ARQ-531 and ibrutinib were compared directly, all dosed at 10mg/kg QD, and the resulting tumor growth inhibition rates (TGI) are 38.3%, 9.3% and 22.5%, respectively. Based on our data, HBW-3-10 is more efficacious than ARQ-531 and ibrutinib. In a 14-day preliminary toxicity experiment in rats, both HBW-3-10 and ARQ-531 were dosed 100mg/kg QD. Animals in ARQ531 group started showing signs of sickness on day 3, and all died on day 6 due toxicity; in contrast, no animal in HBW-3-10 group showed any sign of sickness or died during the entire course of study. Conclusions: We have discovered a novel second generation reversible BTK inhibitors HBW-3-10, that has a superior preclinical profile, efficacy and safety than other known ones. HBW-3-10 provides a valuable clinical candidate for treating Ibrutinib resistant CLL and beyond![Table: see text]

Pathologic up-regulation of TNFSF15–TNFRSF25 axis sustains endothelial dysfunction in unprovoked venous thromboembolism

2019 ◽  
Vol 116 (3) ◽  
pp. 698-707
Author(s):  
Silvia Della Bella ◽  
Francesca Calcaterra ◽  
Monica Bacci ◽  
Claudia Carenza ◽  
Chiara Pandolfo ◽  
...  
Keyword(s):  
Venous Thromboembolism ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Death Receptor ◽  
Lower Growth ◽  
Endothelial Colony Forming Cells ◽  
Healthy Donors ◽  
Novel Therapeutic Strategies ◽  
Microarray Expression

Abstract Aims The pathogenetic mechanisms underlying unprovoked venous thromboembolism (uVTE) are largely unknown. In this study, we investigated the molecular mechanisms involved in uVTE pathogenesis by using ex vivo expanded endothelial colony-forming cells (ECFCs), which represent a valuable non-invasive tool for the assessment of endothelial function. Methods and results We isolated and expanded ECFCs from the peripheral blood of uVTE patients and observed that these cells underwent earlier senescence and showed lower growth rate compared with ECFCs obtained from healthy donors. Through microarray expression profiling, we demonstrated that 2905 genes were differentially expressed between patients and controls. Among them, the anti-angiogenic cytokine TNF superfamily member 15 (TNFSF15) and its death-receptor TNFRSF25 were up-regulated in uVTE ECFCs, and this finding was validated by RT-qPCR. TNFSF15 up-regulation was confirmed at the protein level in ECFC supernatants, and the in vivo relevance of these findings was further corroborated by demonstrating that also the plasmatic levels of TNFSF15 are increased in uVTE patients. After proving that exogenous TNFSF15 exerts pro-apoptotic and anti-proliferative activity on control ECFCs, we demonstrated through blocking experiments that TNFSF15 up-regulation contributes to impaired survival and proliferation of uVTE ECFCs. Conclusion By providing evidence that TNFSF15 impairs ECFC functions crucial to endothelial repair, and that uVTE patients have increased TNFSF15 levels both ex vivo and in vivo, the results of this study suggest that pathologic up-regulation of TNFSF15–TNFRSF25 axis may contribute to uVTE pathogenesis, and may represent the target for novel therapeutic strategies aimed at preventing recurrences in uVTE patients.

A Non-Internalizing Anti-CD40 Antibody, CHIR-12.12, Blocks CD40L-Induced Cytokine Production and Mediates Greater ADCC Than Rituximab in Primary CLL Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2964-2964
Author(s):  
Xia Tong ◽  
Sharon Lea Aukerman ◽  
Karen Lin ◽  
Natasha Aziz ◽  
Cheryl Goldbeck ◽  
...  
Keyword(s):  
Cell Surface ◽  
B Cell ◽  
Cytokine Production ◽  
Ex Vivo ◽  
Lymphocytic Leukemia ◽  
Target Cells ◽  
Adcc Activity ◽  
Effector Cells ◽  
Cells Cultured

Abstract CD40 is expressed on chronic lymphocytic leukemia (CLL) cells, and CD40 activation leads to signaling critical for cell survival and proliferation. We have previously described a novel, fully human IgG1 anti-CD40 antagonistic monoclonal antibody, CHIR-12.12, generated in XenoMouse® mice (Abgenix, Inc.), and have demonstrated that it inhibits normal human B cell proliferation and survival and mediates potent antibody-dependent cellular cytotoxicity (ADCC) against primary CLL and non-Hodgkin’s lymphoma cells. In this study, we examined the ability of CHIR-12.12 to modulate cytokine production by primary CLL cells and compared the ADCC activity of CHIR-12.12 with rituximab against primary CLL cells. Primary CLL cells stimulated with CD40L produced a variety of cytokines, including IL-10, TNF-α , IL-8, GM-CSF, IL-6, MCP-1, and MIP-1β. Addition of CHIR-12.12 to primary CLL cells inhibited CD40L-mediated production of these cytokines. Cytokine production by primary CLL cells cultured with CHIR-12.12 alone in the absence of CD40L did not exceed levels produced by CLL cells cultured in medium. These data suggest that CHIR-12.12 is a potent antagonist for CD40L-mediated cytokine production by primary CLL cells and shows no agonistic activity by itself. We next compared the relative ADCC activity of CHIR-12.12 and rituximab against ex vivo primary CLL cells from 8 patients. CHIR-12.12 exhibited greater ADCC than rituximab against CLL cells from all patients. The average percent of maximum lysis by CHIR-12.12 and rituximab were 49 ± 16% and 31 ± 14%, respectively. CHIR-12.12 was greater than 10-fold more potent than rituximab, as measured by ED50 values (14.1 pM versus 155.5 pM, respectively). Quantitative CD20 and CD40 density on CLL cells and the degree of antibody internalization were investigated as potential reasons for the difference in ADCC activity. The greater ADCC potency and efficacy of CHIR-12.12 was not dependent on a higher density of cell surface CD40 molecules, as there were 1.3 to 14-fold higher numbers of CD20 than CD40 molecules on the cell surface. Antibody internalization studies using primary CLL cells conducted by flow cytometry and confocal microscopy show that upon binding to CD40 at 37°C, CHIR-12.12 remains uniformly distributed on the cell surface, even after 3 hours. In contrast, after binding at 37°C, rituximab is redistributed into caps and internalized. These data suggest that the potent ADCC activity of CHIR-12.12 may be partly related to its ability to remain on the surface of target cells uniformly, allowing optimal interaction with effector cells. Taken together, these results suggest that CHIR-12.12 may be effective at mediating potent ADCC against CLL cells in vivo. CHIR-12.12 is currently in Phase I trials for B-cell malignancies.

Anti-Tumor Activity of the Aurora a Inhibitor MLN8237 in Diffuse Large B-Cell Lymphoma Preclinical Models.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1592-1592 ◽  
Author(s):  
Jessica J Huck ◽  
Mengkun Zhang ◽  
Marc L Hyer ◽  
Mark G Manfredi
Keyword(s):  
Tumor Growth ◽  
Growth Inhibition ◽  
Tumor Model ◽  
B Cell Lymphoma ◽  
Tumor Growth Inhibition ◽  
Aurora A ◽  
Hct 116 ◽  
Xenograft Models

Abstract Aurora A kinase is a serine/threonine protein kinase that is essential for normal transit of cells through mitosis. In many tumor types the Aurora A gene is amplified and/or the protein is over-expressed. The Aurora A small-molecule inhibitor MLN8237 demonstrated robust tumor growth inhibition in xenograft models of solid tumors grown subcutaneously (S.C.) in immunocompromised mice. Here we explored the antitumor activity of MLN8237 in models of diffuse large B-cell lymphoma (DLBCL) both in vitro and in vivo. In vivo three established DLBCL xenograft models (OCI-Ly7, OCI-Ly19, and WSU-DLCL2; all cells expressing luciferase) and a primary DLBCL tumor model PHTX-22-06 were tested using MLN8237 at different doses. Rituximab, an anti-CD20 monoclonal antibody that is active against CD20+ malignant B cells and is a standard of care agent was used for comparison. Using these model systems, tumor cells were injected either I.V. (to evaluate disseminated disease), or S.C. in severe combined immunodeficient mice (SCID). Animals were dosed orally for 21 days with MLN8237 (QD or BID) at various doses, or Rituximab dosed at 10mg/kg IV (once/week) and tumor growth inhibition was monitored using either bioluminescent imaging for the disseminated models or vernier calipers for the S.C. models. Tumor growth inhibition by MLN8237 was dose dependent with 20 mg/kg bid being the most efficacious dose (TGI>100% in both disseminated OCI-Ly19 and WSU models). All animals in the OCI-Ly19 disseminated model 20 mg/kg BID treatment group demonstrated regressions and remained disease free until the end of the study, day 65. In this study the Rituximab treated animals were euthanized on day 31 due to a high level of tumor burden. In the primary tumor model, PHTX-22-06, MLN8237 dosed at 20 mg/kg BID was also the most efficacious with a TGI of 95%. Moreover, tumor growth inhibition was durable as determined by prolonged tumor growth delay (>50 days). Significant efficacy was achieved in all models tested, whether grown as disseminated or subcutaneous models. A noted increase in durability of response was observed with MLN8237 treatment when compared with previous data from solid tumor models. In vitro, MLN8237 treatment increased levels of apoptosis in the OCI-Ly19 cells in comparison to the solid tumor cell line HCT-116 (colon). Greater Annexin V positive cells and greater cleaved PARP and Caspase-3 signals were detected in the MLN8237 treated OCI-Ly19 cells when compared to HCT-116 cells. The demonstration of robust and durable anti-tumor activity in preclinical models treated with MLN8237 provides the basis for its clinical evaluation as a treatment option for DLBCL. MLN8237 is currently in multiple Phase I clinical trials.

A Novel Mutation In Bruton Tyrosine Kinase Confers Acquired Resistance To Ibrutinib (PCI-32765) In CLL

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4914-4914 ◽  
Author(s):  
Richard R. Furman ◽  
Shuhua Cheng ◽  
Pin Lu ◽  
Menu Setty ◽  
Alexandar Perez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Ex Vivo ◽  
Novel Mutation ◽  
Expression Profiles ◽  
Covalent Binding ◽  
Lymphocytic Leukemia ◽  
Brdu Incorporation ◽  
Bruton Tyrosine Kinase ◽  
Pre Treatment

Abstract The Bruton tyrosine kinase (BTK) inhibitor, ibrutinib has produced durable remissions in chronic lymphocytic leukemia (CLL). We describe a CLL patient who progressed while receiving ibrutinib following 20 months of once daily dosing. A cysteine-to-serine amino acid replacement was identified in BTK at position 481 that disrupts the covalent, but not non-covalent, binding of ibrutinib to BTK in silico structural modeling1. The mutation was present in relapsed samples while absent in the pre-treatment and responding samples. Following the mutation, the B cell receptor (BCR) pathway was reactivated as evidenced by increased cell signaling activities and gene expression profiles. Comparing the relapsed samples with the pre-treatment and responding samples, at the cellular level, mutated CLL cells displayed higher levels of the cell proliferation marker Ki67 in vivo and higher levels of ex-vivo BrdU incorporation. Transfection of the C481S mutant construct into a sensitive lymphoma cell line rendered it much more resistant to ibrutinib treatment demonstrating the cellular impact of the mutation (see attached graph). Interestingly, the ibrutinib-resistant CLL cells remained sensitive to other BCR inhibitors such as dasatinib and SYK inhibitors. These results confirm BTK as an important pharmacologic target of ibrutinib. Further, a mechanism of resistance was revealed, and alternative therapeutic options for ibrutinib resistance were explored. (First three authors with equal contribution) Disclosures: Furman: Genentech: Consultancy, Speakers Bureau; GlaxoSmithKline: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy; Gilead: Consultancy. Chang:Pharmacyclics: Employment, Equity Ownership.

Development of a Human Therapeutic L-Cyst(e)Ine-Degrading Enzyme for the Treatment of Hematological Malignancies

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1587-1587
Author(s):  
Giulia Agnello ◽  
Susan Alters ◽  
Joseph Tyler ◽  
Jinyun Liu ◽  
Peng Huang ◽  
...  
Keyword(s):  
Research Funding ◽  
Hematological Malignancies ◽  
Ex Vivo ◽  
Redox Balance ◽  
Lymphocytic Leukemia ◽  
Employment Equity ◽  
Equity Ownership ◽  
Antioxidant Mechanisms

Abstract Cancer cells experience higher intrinsic oxidative stress than their normal counterparts and acquire adaptive antioxidant mechanisms to maintain redox balance. This increased antioxidant capacity has been correlated to malignant transformation, metastasis and resistance to standard anticancer drugs. This enhanced antioxidant state also correlates with cancer cells being more vulnerable to additional oxidative insults, therefore disruption of adaptive antioxidant mechanisms may have significant therapeutic implications. Hematological malignancies including Chronic Lymphocytic Leukemia (CLL), Acute Lymphocytic Leukemia (ALL), Acute Myeloid Leukemia (AML) and Multiple Myeloma (MM) are critically dependent on the cellular antioxidant glutathione (GSH), consistent with the higher intrinsic oxidative stress. L-cysteine is the rate-limiting substrate for GSH biosynthesis and adequate levels of cysteine are critical to maintain the intracellular homeostasis of GSH. CLL and a subset of ALL cells have been reported to rely on the stromal supply of cysteine to increase the synthesis of GSH in order to maintain redox balance, which in turn promotes cell survival and fosters drug resistance. One approach to target this cancer specific dependency is by therapeutic depletion of amino acids via enzyme administration; a clinically validated strategy for the treatment of ALL. Aeglea BioTherapeutics Inc. has developed a bioengineered cysteine and cystine degrading enzyme (Cyst(e)inase, AEB3103) and evaluated its therapeutic efficacy against hematological malignancies in in vitro, ex vivo and in vivo pre-clinical studies. The TCL1-TG:p53 -/- mouse model exhibits a drug resistant phenotype resembling human CLL with unfavorable cytogenetic alterations and highly aggressive disease progression. AEB3103 greatly decreased the viability of TCL1-TG:p53 -/- cells cultured in vitro, whereas the CLL therapeutic, fludarabine, showed minimal cytotoxic effects. In vivo treatment of TCL1-TG:p53 -/- mice with AEB3103 resulted in an increase in median survival time (7 months, p<0.0001) compared to the untreated control group (3.5 months, p<0.001) and a fludarabine treated group (5.3 months, p<0.001). These results indicate a superior therapeutic effect of AEB3103 compared to fludarabine. Additionally, evaluation of AEB3103 in in vitro 2D cultures of patient-derived CLL and MM cells, and in ex vivo 3D cultures of cells derived from ALL and AML PDx models resulted in significant cell growth inhibition with therapeutically relevant IC50 values. Collectively these results demonstrate the sensitivity of hematological malignancies to modulation of GSH levels via AEB3103-mediated cyst(e)ine depletion. Disclosures Agnello: Aeglea BioTherapeutics: Employment. Alters:Aeglea BioTherapeutics: Employment, Equity Ownership. Tyler:Aeglea BioTherapeutics: Employment, Equity Ownership. Huang:Aeglea BioTherapeutics: Research Funding. Stone:Aeglea Biotherapeutics: Consultancy, Equity Ownership, Research Funding; University of Texas at Austin: Employment, Patents & Royalties: I am an inventor of technology related to this abstract. Georgiou:Aeglea Biotherapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Lowe:Aeglea BioTherapeutics: Employment, Equity Ownership. Rowlinson:Aeglea BioTherapeutics: Employment, Equity Ownership.

scholarly journals Four ricin chain A-based immunotoxins directed against the common chronic lymphocytic leukemia antigen: in vitro characterization

Blood ◽  
1993 ◽  
Vol 82 (2) ◽  
pp. 536-543
Author(s):  
GB Faguet ◽  
JF Agee
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
T Lymphocytes ◽  
Ex Vivo ◽  
Lymphocytic Leukemia ◽  
Fab Fragment ◽  
In Vitro Characterization ◽  
The Common ◽  
Dose Dependent

The common B-chronic lymphocytic leukemia (B-CLL) antigen (cCLLa) appears to be ideal for targeted immunotherapy in that it is the most prevalent and disease-restricted marker in B-CLL. To assess this potential, we developed four immunotoxins (ITs) of anti-cCLLa monoclonal antibody CLL2m (an IgG2a kappa), using ricin chain A (RTA) or its deglycosylated derivative (dgA), each conjugated to either the whole IgG molecule or its Fab' fragment. Each IT was tested in vitro for specificity and cytotoxic activity (assessed by protein synthesis inhibition [PSI] and by cell kill [CK] in the clonogenic assay) against B-CLL cells. RTA-based anti-CD5 ITs and enriched normal B and T lymphocytes were used as controls. Each IT exhibited antigen-specific, dose-dependent activity. Thus, whereas B-CLL cells exhibited dose- dependent PSI and CK (whether the B-CLL clone was CD5+ or CD5-), normal B (cCLLa-/CD5-) and T lymphocytes (cCLLa-/CD5+) remained unaffected. IT potency was independent of toxin glycosylation, but was slightly influenced by antibody valence; divalent ITs were twice as potent as monovalent ITs (IC50, 2.3 v 7.1 x 10(-11) mol/L; CK, 2.6- v 2.0-log reached with 524 v 1,072 IT molecules bound/cell, respectively). In the presence of ammonium chloride or Verapamil, IT-induced CK was enhanced 10- to 80-fold. These data suggest that the cCLLa is a promising target for IT-based immunotherapy of B-CLL in vivo and ex vivo.

Sign in / Sign up

Export Citation Format

Share Document