Improving the Treatment Outcome of Patients with Chronic Lymphocytic Leukemia Through Targeted Antibody Therapy

Dexamethasone-(C21-phosphoramide)-[anti-EGFR]: molecular design, synthetic organic chemistry reactions, and antineoplastic cytotoxic potency against pulmonary adenocarcinoma (A549)

PURPOSE

Corticosteroids are effective in the management of a variety of disease states, such as several forms of neoplasia (leukemia and lymphoma), autoimmune conditions, and severe inflammatory responses. Molecular strategies that selectively "target" delivery of corticosteroids minimize or prevents large amounts of the pharmaceutical moiety from passively diffusing into normal healthy cell populations residing within tissues and organ systems.

MATERIALS AND METHODS

The covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR] was synthesized by reacting dexamethasone-21-monophosphate with a carbodiimide reagent to form a dexamethasone phosphate carbodiimide ester that was subsequently reacted with imidazole to create an amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate. Monoclonal anti-EGFR immunoglobulin was combined with the amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate, resulting in the synthesis of the covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Following spectrophotometric analysis and validation of retained epidermal growth factor receptor type 1 (EGFR)-binding avidity by cell-ELISA, the selective anti-neoplasic cytotoxic potency of dexamethasone-(C21-phosphoramide)-[anti-EGFR] was established by MTT-based vitality stain methodology using adherent monolayer populations of human pulmonary adenocarcinoma (A549) known to overexpress the tropic membrane receptors EGFR and insulin-like growth factor receptor type 1.

RESULTS

The dexamethasone:IgG molar-incorporation-index for dexamethasone-(C21-phosphoramide)-[anti-EGFR] was 6.95:1 following exhaustive serial microfiltration. Cytotoxicity analysis: covalent bonding of dexamethasone to monoclonal anti-EGFR immunoglobulin did not significantly modify the ex vivo antineoplastic cytotoxicity of dexamethasone against pulmonary adenocarcinoma at and between the standardized dexamethasone equivalent concentrations of 10(-9) M and 10(-5) M. Rapid increases in antineoplastic cytotoxicity were observed at and between the dexamethasone equivalent concentrations of 10(-9) M and 10(-7) M where cancer cell death increased from 7.7% to a maximum of 64.9% (92.3%-35.1% residual survival), respectively, which closely paralleled values for "free" noncovalently bound dexamethasone.

DISCUSSION

Organic chemistry reaction regimens were optimized to develop a multiphase synthesis regimen for dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Attributes of dexamethasone-(C21-phosphoramide)-[anti-EGFR] include a high dexamethasone molar incorporation-index, lack of extraneous chemical group introduction, retained EGFR-binding avidity ("targeted" delivery properties), and potential to enhance long-term pharmaceutical moiety effectiveness.

Targeted antisense radiotherapy and dose fractionation using a (177)Lu-labeled anti-bcl-2 peptide nucleic acid-peptide conjugate

INTRODUCTION

The overall goal of these studies was to test the hypothesis that simultaneous down-regulation of a tumor survival gene and delivery of internally emitted cytotoxic radiation will be more effective than either treatment modality alone. The objectives were to evaluate the therapeutic efficacy of a (177)Lu-labeled anti-bcl-2-PNA-Tyr(3)-octreotate antisense conjugate in a mouse model bearing human non-Hodgkin's lymphoma (NHL) tumor xenografts and to optimize targeted antisense radiotherapy by dose fractionation.

METHODS

In the initial therapy studies, tumor-bearing mice were given saline, nonradioactive DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate, (177)Lu-DOTA-Tyr(3)-octreotate, (177)Lu-DOTA-PNA-peptide alone, or (177)Lu-DOTA-PNA-peptide followed by a chase dose of nonradioactive PNA-peptide. The MTD of (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate was then determined. Subsequently single dose MTD and four weekly fractionated doses were directly compared, followed by histopathologic evaluation.

RESULTS

Antisense radiotherapy using 4.44 MBq of the (177)Lu-DOTA-PNA-peptide followed by nonradioactive PNA-peptide was significantly more effective than other low dose treatment regimens. A dose of 18.5 MBq of (177)Lu-DOTA-PNA-peptide was determined to be the approximate maximum tolerated dose (MTD). The median times to progression to a 1cm(3) tumor volume were 32 and 49 days for single dose MTD and fractionated dose (4 × 4.63 MBq) groups, respectively. Histopathology revealed metastases in the single dose groups, but not in the dose fractionation group.

CONCLUSIONS

Targeted antisense radiotherapy using (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate and DOTA-PNA-peptide conjugate effectively inhibited tumor progression in a mouse model of NHL. Furthermore, a dose fractionation regimen had a significant advantage over a single high dose, in terms of tumor growth inhibition and prevention of metastasis.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Down-regulating bcl-2, an anti-apoptotic proto-oncogene, is a mechanism to reverse chemotherapy resistance or failure in humans with NHL. We have developed a (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate conjugate for targeted antisense radiotherapy, in which down-regulation of bcl-2 and delivery of cytotoxic radiation occur simultaneously. Our previous studies have shown highly specific inhibition of bcl-2 protein, additive in vitro cytotoxic effects on human lymphoma cells, and favorable biodistribution and dosimetric properties. Lutetium-177 targeted antisense radiotherapy demonstrates a significant advantage over conventional (177)Lu-peptide receptor radionuclide therapy in a mouse model of NHL. Our preclinical studies identified an effective combination of antisense and radionuclide therapy, with the goal of future clinical trials in patients.

Pro-apoptotic effect of an anti-CD37 scFv-Fc fusion protein, in combination with the anti-CD20 antibody, ofatumumab, on tumour cells from B-cell malignancies

SMIP-016, a new anti-tumour agent, is a mouse/human chimeric fusion protein built on the ADAPTIR™ (modular protein therapeutic) platform targeting human CD37. In this study, for the first time, we examined pro-apoptotic activity of SMIP-016 in combination with monoclonal anti-CD20 antibody, ofatumumab (HuMax-CD20) in de novo chronic lymphocytic leukaemia (CLL) cells and in different B-cell neoplasm-derived lines. In CLL cells SMIP-016 exerted significant cytotoxicity (versus control - p=0.01). In the in vitro models, SMIP-016 was also distinctly active against Raji line (Burkitt lymphoma; BL) (versus control - p=0.007), Riva-1 line (diffuse large B-cell lymphoma; DLBCL) (versus control - p=0.002) and RPMI 8226 line (multiple myeloma cells; MM) (versus control - p=0.03). In studies combining SMIP-016 and ofatumumab, the cytotoxicity against CLL cells was significantly higher than the agents used alone (p<0.03). Remarkably enhanced cytotoxic activity of SMIP-016 and ofatumumab in combination was also observed in Raji and Riva-1 cell lines (p<0.01 and p<0.003, respectively). Importantly, both agents induced cytotoxicity at very low concentrations which suggests that potential side-effects may be decreased in clinical practice. The mechanism responsible for cytotoxicity of SMIP-016 in all the examined models was connected with caspase-dependent apoptosis. In majority of cell types SMIP-016 induced overexpression of Bax protein, as well as downregulation of Bcl-2, cIAP1 (p<0.03) and Smac/DIABLO (p<0.003) apoptosis-regulating proteins. In conclusion, our study demonstrated high pro-apoptotic activity of SMIP-016, especially in combination with ofatumumab, against ex vivo CLL cells, and BL or DLBCL in vitro cell lines. Thus, further preclinical studies in in vivo models are warranted, as this combination may be a promising therapeutic concept for treatment of those malignancies.

Matrix metalloproteinase-9 is involved in chronic lymphocytic leukemia cell response to fludarabine and arsenic trioxide

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) contributes to chronic lymphocytic leukemia (CLL) pathology by regulating cell migration and preventing spontaneous apoptosis. It is not known if MMP-9 is involved in CLL cell response to chemotherapy and we address this in the present study, using arsenic trioxide (ATO) and fludarabine as examples of cytotoxic drugs.

METHODS

We used primary cells from the peripheral blood of CLL patients and MEC-1 cells stably transfected with an empty vector or a vector containing MMP-9. The effect of ATO and fludarabine was determined by flow cytometry and by the MTT assay. Expression of mRNA was measured by RT-PCR and qPCR. Secreted and cell-bound MMP-9 was analyzed by gelatin zymography and flow cytometry, respectively. Protein expression was analyzed by Western blotting and immunoprecipitation. Statistical analyses were performed using the two-tailed Student's t-test.

RESULTS

In response to ATO or fludarabine, CLL cells transcriptionally upregulated MMP-9, preceding the onset of apoptosis. Upregulated MMP-9 primarily localized to the membrane of early apoptotic cells and blocking apoptosis with Z-VAD prevented MMP-9 upregulation, thus linking MMP-9 to the apoptotic process. Culturing CLL cells on MMP-9 or stromal cells induced drug resistance, which was overcome by anti-MMP-9 antibodies. Accordingly, MMP-9-MEC-1 transfectants showed higher viability upon drug treatment than Mock-MEC-1 cells, and this effect was blocked by silencing MMP-9 with specific siRNAs. Following drug exposure, expression of anti-apoptotic proteins (Mcl-1, Bcl-xL, Bcl-2) and the Mcl-1/Bim, Mcl-1/Noxa, Bcl-2/Bax ratios were higher in MMP-9-cells than in Mock-cells. Similar results were obtained upon culturing primary CLL cells on MMP-9.

CONCLUSIONS

Our study describes for the first time that MMP-9 induces drug resistance by modulating proteins of the Bcl-2 family and upregulating the corresponding anti-apoptotic/pro-apoptotic ratios. This is a novel role for MMP-9 contributing to CLL progression. Targeting MMP-9 in combined therapies may thus improve CLL response to treatment.

Targeted therapy in chronic lymphocytic leukemia: past, present, and future

BACKGROUND

Chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in the western world. Recent advances in understanding the biology of B-cell malignancies have resulted in the development of novel agents targeting key prosurvival pathways in the neoplastic B cell.

OBJECTIVE

The goal of this article was to summarize current literature on the emerging therapeutic approaches in CLL and B-cell malignancies.

METHODS

A literature review was performed, identifying pathways and key clinical trials involving novel therapies in CLL, with special emphasis on B-cell receptor (BCR)-targeting agents.

RESULTS

Understanding the biology of the BCR-signaling pathway has led to identification of novel molecular targets. Most notably, inhibitors of Bruton tyrosine kinase and phosphatidylinositide 3-kinase-δ have entered clinical trials and demonstrated high response rates in CLL, including high-risk disease. Cyclin-dependent kinase inhibitors may evolve into an alternative therapeutic approach in CLL. New drugs that target molecules within and outside of the BCR-signaling pathway have shown promise in preclinical studies.

CONCLUSIONS

Both preclinical and early clinical trial results involving novel targeted therapies suggest that the standard treatment paradigm in CLL and B-cell malignancies will soon change. Particular attention should be paid to the BCR-targeting agents, whose favorable adverse effect profile may improve the lives of elderly patients with CLL.