Local delivery of c-myc neutrally charged antisense oligonucleotides with transport catheter inhibits myointimal hyperplasia and positively affects vascular remodeling in the rabbit balloon injury model

Therapeutic potential of c-Myc inhibition in the treatment of hypertrophic cardiomyopathy

Investigating the pathophysiological importance of the molecular and mechanical development of cardiomyopathy is critical to find new and broader means of protection against this disease that is increasing in prevalence and impact. The current available treatment options for cardiomyopathy mainly focus on treating symptoms and strive to make the patient more comfortable while preventing progression of disease and sudden death. The proto-oncogene c-Myc (Myc) has been shown to be increased in many different types of heart disease, including hypertrophic cardiomyopathy, before any signs of the disease are present. As the mechanisms of action and multiple pathways of dependent actions of Myc are being dissected by many research groups, inhibition of Myc is becoming an attractive paradigm for prevention and treatment of cardiomyopathy and heart failure. Elucidating the role Myc plays in the development, propagation and perpetuation of cardiomyopathy and heart failure will one day translate into potential therapeutics for cardiomyopathy.

First human experience with local delivery of novel antisense AVI-4126 with Infiltrator catheter in de novo native and restenotic coronary arteries: 6-month clinical and angiographic follow-up from AVAIL study

BACKGROUND

A novel antisense phosphorodiamidate morpholino oligomer, AVI-4126, was shown to be effective in reducing neointimal formation in different animal models following delivery by pluronic gels, porous balloon catheters, and coated stents. The purpose of the AVAIL study was to investigate both the safety and the efficacy of AVI-4126 delivered locally via Infiltrator catheter after percutaneous coronary intervention in humans.

METHODS

The AVAIL trial is a prospective, evaluator-blinded, randomized study including clinical follow-up at 30 days and 6 months after intervention and 6-month angiographic and intravascular ultrasound (IVUS) follow-up. An Infiltrator catheter was advanced to target lesion and either drug was delivered (Groups A and B) or catheter was advanced (Group C) after stent implantation in de novo lesions or percutaneous transluminal coronary angioplasty in restenotic lesions. Primary end points include major adverse cardiovascular events (MACE), target vessel revascularization (TVR), angiographic restenosis, and IVUS at 6 months.

RESULTS

Forty-four patients with either de novo lesions or restenosis were randomized into three groups: (A) low dose, 3 mg (19 patients); (B) high dose, 10 mg (15 patients), and (C) control (10 patients). Baseline angiographic characteristics did not differ between the groups (reference vessel diameter, 2.5-4 mm; lesion length, <16 mm). Procedural success was 81. 82% (unable to advance Infiltrator catheter to target lesion in 8 patients, 5 from Group B and 3 from Group C). There was no in-hospital or 30-day MACE recorded in any group. Clinical follow-up was available in 25 patients. At 6 months, four patients (50%) from the control group (Group C, n=8) and 7 (100%) patients from the low-dose group (Group A, n=7) required TVR. In contrast, in the high-dose group (Group B, n=10) only 1 patient (10%) needed TVR. Angiographic follow-up in 25 patients (Group A, 8 patients; Group B, 7 patients; and Group C, 10 patients) demonstrated late loss of 1.4+ to 0.54, 0.8+ to 0.55, and 1.5+ to 0.65, respectively (P=.025). Binary restenosis was 38% in Group C (control), 29% in Group A (low dose), and 0% in Group B (high dose).

CONCLUSION

Local delivery of antisense is feasible. These preliminary findings from the small cohort of patients require confirmation in a larger trial utilizing more sophisticated drug-eluting technologies.

c-MYC antisense phosphosphorodiamidate morpholino oligomer inhibits lung metastasis in a murine tumor model

BACKGROUND

c-MYC amplification and overexpression has been correlated with progression and chemotherapy resistance in lung cancer. AVI-4126, a neutral antisense phosphorodiamidate morpholino oligomer (PMO) has been identified to specifically inhibit c-MYC expression in multiple disease models and identified in Phase I clinical studies to be safe and bioavailable in solid tumors. The present study evaluates AVI-4126 on the development of lung metastasis in the LLC1 syngeneic murine tumor model. Further, this is the first study to show in vivo mis-splicing of c-MYC post-AVI-4126 treatment.

METHODS AND RESULTS

Subcutaneous administration of AVI-4126 at local tumor site (50 microg/day) for 3 cycles of 5 days a week starting day 1 post-tumor cell implantation showed significantly decreased tumor burden, number of tumorlets formed in the lung in comparison to saline or control PMO treatment groups, although no significant reduction of the subcutaneous tumor was observed. AVI-4126 treated lung had markedly reduced mitotic activity but higher rate of apoptosis compared to the controls. HPLC-based analysis of tumor and lung lysates confirmed the presence of intact PMO. In addition to decrease in c-MYC expression, a moderate reduction in the levels of MMP-9 mRNA, a pro-angiogenic extracellular matrix protein postulated to be involved in extravasation of cells from the localized tumor or implantation into the distant metastatic site was observed in the LLC1 tumor tissue of AVI-4126 treated animals.

CONCLUSIONS

The study results are significant in the development of novel anti-tumoral therapeutic strategies directed to c-MYC-overexpressing tumors and establish AVI-4126 as a strong clinical candidate for metastatic disease.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Vascular delivery of c-myc antisense from cationically modified phosphorylcholine coated stents

c-Myc is involved in the formation of neointimal hyperplasia. We investigated in vitro, ex vivo and in vivo release of antisense c-myc from cationically modified phosphorylcholine-coated stents, as well as the effects on c-Myc expression and neointima formation in a porcine coronary stent model. In vitro experiments were performed to determine optimal loading of stents with antisense. Stents loaded with labelled antisense were deployed in porcine arteries ex vivo and in vivo. Antisense was detected in the vessel wall directly surrounding the stent of pig carotid and coronary artery up to 48 h after stent deployment. Nuclear uptake was observed in endothelial and vascular smooth muscle cells. Labelled antisense within peripheral tissues in vivo was <1.0% of that within stented arterial segments. Control and antisense loaded stents implanted into 10 pig coronary arteries and analysed at 28 days post-stenting showed that lumen area within the antisense stents was significantly increased (i.e. 30.5% greater, P<0.01), whilst both neointimal area and neointimal thickness were significantly reduced (17.5% and 19.5%, respectively, P<0.01) compared to control stents. Cationically modified phosphorylcholine coated stent-based delivery of c-myc antisense is feasible with minimal systemic delivery and is associated with a reduction of in-stent neointimal hyperplasia in pig coronary arteries.

siRNA-based approaches in cancer therapy

The availability of the human genome sequence has revolutionized the strategy of employing nucleic acids with sequences complementary to specific target genes to improve drug discovery and target validation. Development of sequence-specific DNA or RNA analogs that can block the activity of selected single-stranded genetic sequences offers the possibility of rational design with high specificity, lacking in many current drug treatments for various diseases including cancer, at relatively inexpensive costs. Antisense technology is one such example that has shown promising results and boasts of yielding the only approved drug to date in the genomics field. However, in vivo delivery issues have yet to be completely overcome for widespread clinical applications. In contrast to antisense oligonucleotides, the mechanism of silencing an endogenous gene by the introduction of a homologous double-stranded RNA (dsRNA), transgene or virus is called post-transcriptional gene silencing (PTGS) or RNA interference. PTGS is a natural mechanism whereby metazoan cells suppress expansion of genes when they come across dsRNA molecules with the same sequence. Short interfering RNA is currently the fastest growing sector of this antigene field for target validation and therapeutic applications. Although, in theory, the development of genomics-based agents to inhibit gene expression is simple and straightforward, the fundamental concern relies upon the capacity of the oligonucleotide to gain access to the target RNA. This paper summarizes the advances in the last decade in the field of PTGS using RNA interference approaches and provides relevant comparisons with other oligonucleotide-based approaches with a specific focus on oncology applications.

In vivo bioavailability and pharmacokinetics of a c-MYC antisense phosphorodiamidate morpholino oligomer, AVI-4126, in solid tumors

Phosphorodiamidate morpholino oligomers (PMO) inhibit targeted gene expression by preventing ribosomal assembly, thereby preventing mRNA translation. AVI-4126, a PMO targeted against c-MYC, has been extensively characterized in multiple cancer and other disease models and is currently in human clinical trials. A phase I clinical study was conducted to address the issue of PMO bioavailability in malignant tumors surgically excised from patients with adenocarcinoma of prostate and breast 1 day after i.v. administration of a single dose of 90 mg AVI-4126 PMO. The study objectives were to evaluate safety, to determine AVI-4126 concentration in tissue samples of the tumors, and to examine the distribution of AVI-4126 (margin versus tumor core). Significant concentrations of intact PMO similar to the animal models were detected in both human prostate and breast tumor tissues with increased distribution in the tumor core for the vascular breast tumors. No serious adverse events (graded according to National Cancer Institute Common Toxicity Criteria) were reported. Another phase I study was conducted in normal human volunteers to assess AVI-4126 plasma pharmacokinetics following single i.v. administration of 90 mg AVI-4126. Data from both human studies indicated similar plasma concentration-time profile. These studies show PMO bioavailability in tumor tissue and establish the feasibility of using PMO targeting specific genes in human cancer clinical trials.

Intratumoural administration of dendritic cells: hostile environment and help by gene therapy

Like paratroopers in special operations, dendritic cells (DCs) can be deployed behind the enemy borders of malignant tissue to ignite an antitumour immune response. 'Cross-priming T cell responses' is the code name for their mission, which consists of taking up antigen from transformed cells or their debris, migrating to lymphoid tissue ferrying the antigenic cargo, and meeting specific T cells. This must be accomplished in such an immunogenic manner that specific T lymphocytes would mount a robust enough response as to fully reject the malignancy. To improve their immunostimulating activity, local gene therapy can be very beneficial, either by transfecting DCs with genes enhancing their performance, or by preparing tumour tissue with pro-inflammatory mediators. In addition, endogenous DCs from the tumour host can be attracted into the malignant tissue following transfection of certain chemokine genes into tumour cells. On their side, tumour stroma and malignant cells set up a hostile immunosuppressive environment for artificially released or attracted DCs. This milieu is usually rich in transforming growth factor-beta, vascular endothelial growth factor, and IL-10, -6 and -8, among other substances that diminish DC performance. Several molecular strategies are being devised to interfere with the immunosuppressive actions of these substances and to further enhance the level of anticancer immunity achieved after artificial release of DCs intratumourally.

The drug-based pipeline against restenosis

More than 1 million percutaneous coronary interventions (PCIs) are performed yearly worldwide. Restenosis is the recurrent narrowing that can occur within 6 months following an initially successful PCI. Although drug-eluting stents have accomplished remarkable success, restenosis has not been eliminated and optimisation of both the polymers and drugs associated with them is desirable. This article reviews the presently available and potential preventive approaches against restenosis, including the sirolimus and paclitaxel drug-eluting stents.

Systemic targeted delivery of antisense with perflourobutane gas microbubble carrier reduced neointimal formation in the porcine coronary restenosis model

HYPOTHESIS

The antisense phosphorodiamidate morpholino oligomer (PMO), AVI-4126, has been effective in reducing neointimal formation in animal models following delivery by pluronic gels, local delivery catheters and coated stents. Greater flexibility of repeated-dosage regimens and reduced procedure complexity may be provided by systemic injection of AVI-4126 bound to perfluorobutane gas microbubble carriers. The purpose of this study was to investigate the effects of perfluorocarbon gas microbubble carrier (PGMC)-based systemic delivery of AVI-4126 on expression of the c-myc in vascular tissue and restenosis after stent implantation.

METHODS

Seven pigs underwent stent implantation (3 stents/animal). Five pigs received IV injection of PGMC and 2 mg of AVI-4126 (AVI BioPharma). Two served as control. Four hours postprocedure, 3 pigs were sacrificed and stented segments analyzed by high-performance liquid chromatography (HPLC) and Western blot. In chronic experiments, 4 pigs (12 stent sites) were sacrificed at 28 days.

RESULTS

HPLC analysis of plasma samples of treated animals showed minimal presence of AVI-4126. HPLC of the treated arteries demonstrated easily detected concentrations of AVI-4126. Western blot analysis of the stented vessels demonstrated modest inhibition of c-myc. Morphometry showed that the neointimal area was significantly reduced in the AVI-4126/PGMC group compared with control (2.63+/-1.99 vs. 4.77+/-.1.71 mm2, respectively, P<.05).

CONCLUSION

In the porcine coronary stent model, systemic targeted delivery of AVI-4126 using PGMC carrier significantly inhibited neointimal formation.

Advanced c-myc antisense (AVI-4126)-eluting phosphorylcholine-coated stent implantation is associated with complete vascular healing and reduced neointimal formation in the porcine coronary restenosis model

An advanced six-ring morpholino backbone c-myc antisense (AVI-4126) was shown to inhibit c-myc expression and intimal hyperplasia after local catheter delivery in a porcine balloon injury model. The purpose of this study was to investigate the effects of an AVI-4126-eluting phosphorylcholine-coated (PC) stent on c-myc expression restenosis and vascular healing after stent implantation in porcine coronary arteries. PC stents were loaded with AVI-4126 using soak trap. Nine pigs underwent AVI-4126 PC coronary stent implantation (two stents/animal). Two to six hours postprocedure, three pigs were sacrificed and stented segments were analyzed by Western blot for c-myc expression. In chronic experiments, six pigs (12 stent sites) were sacrificed at 28 days following intervention and vessels were perfusion-fixed. High-performance liquid chromatography analysis of plasma samples showed minimal presence of the antisense. Western blot analysis of the stented vessels demonstrated inhibition of c-myc expression at 2 and 6 hr after procedure. Quantitative histologic morphometry showed that the neointimal area was significantly reduced (by 40%) in the antisense-coated group compared with control (2.3 +/- 0.7 vs. 3.9 +/- 0.8 mm(2), respectively; P = 0.0077). Immunostaining and electron microscopy demonstrated complete endothelialization, without fibrin deposition, thrombosis, or necrosis in all implanted stents. In the porcine coronary model, an advanced c-myc-eluting PC stent blocked c-myc expression and significantly inhibited myointimal hyperplasia and allowed complete reendothelialization and healing response.

Concerted effect of transforming growth factor-β, cyclin inhibitor p21, and c-mycon smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-β (TGF-β) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-β inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c- myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-β in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-β gene from aortic SMC, which resulted in a significant increase ( P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [3H]thymidine uptake assay). In TGF-β-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c- myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation ( P < 0.002) in TASMC. Similar treatment with c- myc antisense oligonucleotides significantly ( P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-β sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-β at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.

Resistance to chemotherapeutic drugs overcome by c-Myc inhibition in a Lewis lung carcinoma murine model

Chemotherapy resistance is a significant obstacle in lung cancer therapy, and has been found to frequently correlate with amplification and overexpression of the c-myc oncogene. Earlier studies have shown that c-Myc inhibition alone is not always effective in cancer models. The purpose of this study was to test different dosing regimen, which included commonly used chemotherapeutic drugs in combination with c-Myc inhibition in a Lewis lung syngeneic drug-resistant murine tumor model. Inhibition of c-myc was specifically achieved by using phosphorodiamidate Morpholino oligomer (PMOs), a novel, non-toxic antisense DNA chemistry for inhibition of gene expression by an RNase H-independent mechanism. When administration of cisplatin overlapped with c-myc PMO (AVI-4126) treatment there was no additional effect on tumor growth inhibition compared to cisplatin alone. In contrast, using a dosing regimen in which cisplatin or taxol treatment preceded AVI-4126, a dramatic decrease in tumor growth rate was observed with tumor areas less then 0.5 cm2 in 60% of the animals at the end of the study. This effect was specific to c-Myc inhibition as other antisense PMOs against p21 or Rad51 showed no such effect in combination with chemotherapy. Immunoblot and HPLC-based analysis of tumor lysates at the end of the study confirmed c-Myc inhibition and detection of intact AVI-4126, respectively. In conclusion, AVI-4126 potentiates the efficacy of chemotherapeutic drugs in a manner that is schedule dependent.

Inhibition of human chorionic gonadotropin beta-subunit modulates the mitogenic effect of c-myc in human prostate cancer cells

BACKGROUND

Amplification of the proto-oncogene c-myc has been identified as one of the most common genetic alterations in prostate cancer, thus making it an attractive therapeutic target. However, certain prostate cancer cells are unresponsive to c-Myc inhibition. The purpose of this study was to test the hypothesis that effective growth inhibition in the refractory cancer cells can be achieved by blocking c-myc along with a growth factor using a novel phosphorodiamidate morpholino antisense oligomer-based approach. Human chorionic gonadotropin, a growth factor implicated in neoplasm, causes activation of c-myc through a G-protein-coupled pathway of signal transduction.

METHODS

In this study, the effect of inhibition of beta-hCG and c-myc singly or in combination was evaluated in DU145 (RB -/-, p53-/-, androgen-independent) and LNCaP (Rb+/+, p53 +/+, androgen-sensitive) human prostate cancer cell lines and in a DU145 subcutaneous xenograft murine model.

RESULTS

Antisense phosphorodiamidate morpholino oligomers directed against beta-hCG and c-myc caused a specific decrease of the target protein levels. Unlike LNCaP cells, DU145 cell growth was refractory to c-Myc inhibition. Unresponsiveness to c-myc inhibition in DU145 cells was overcome by targeting both beta-hCG and c-myc genes, resulting in potentiation of the antiproliferative effect seen with inhibition of beta-hCG alone.

CONCLUSIONS

The inhibition of beta-hCG sensitizes prostate cancer cells to the antiproliferative effects of c-Myc inhibition, including tumors that are refractory to c-Myc decrease alone.

Intramural coronary delivery of advanced antisense oligonucleotides reduces neointimal formation in the porcine stent restenosis model

OBJECTIVES

We evaluated the long-term influence of intramural delivery of advanced c-myc neutrally charged antisense oligonucleotides (Resten-NG) on neointimal hyperplasia after stenting in a pig model.

BACKGROUND

Neointimal hyperplasia after percutaneous coronary interventions is one of the key components of the restenotic process. The c-myc is a critical cell division cycle protein involved in the formation of neointima.

METHODS

In short-term experiments, different doses (from 500 microg to 5 mg) of Resten-NG or saline were delivered to the stent implantation site with an infiltrator delivery system (Interventional Technologies, San Diego, California). Animals were euthanized at 2, 6 and 18 h after interventions, and excised vessels were analyzed for c-myc expression by Western blot. In long-term experiments, either saline or a dose of 1, 5 or 10 mg of Resten-NG was delivered in the same fashion, and animals were euthanized at 28 days after the intervention.

RESULTS

Western blot analysis demonstrated inhibition of c-myc expression and was dose dependent. Morphometry showed that the intimal area was 3.88 +/- 1.04 mm(2) in the control. There was statistically significant reduction of intimal areas in the 5 and 10 mg groups (2.01 +/- 0.66 and 1.95 +/- 0.91, respectively, p < 0.001) but no significant reduction in the 1 mg group (2.81 +/- 0.56, p > 0.5) in comparison with control.

CONCLUSIONS

This study demonstrated that intramural delivery of advanced c-myc neutrally charged antisense morpholino compound completely inhibits c-myc expression and dramatically reduces neointimal formation in a dose dependent fashion in a porcine coronary stent restenosis model, while allowing for complete vascular healing.

c-Myc oncoprotein: a dual pathogenic role in neoplasia and cardiovascular diseases?

A growing body of evidence indicates that c-Myc can play a pivotal role both in neoplasia and cardiovascular diseases. Indeed, alterations of the basal machinery of the cell and perturbations of c-Myc-dependent signaling network are involved in the pathogenesis of certain cardiovascular disorders. Down-regulation of c-Myc induced by intervention with antioxidants or by antisense technology may protect the integrity of the arterial wall as well as neoplastic tissues. Further intervention studies are necessary to investigate the effects of tissue-specific block of c-Myc overexpression in the development of cardiovascular diseases.

Complete vascular healing and sustained suppression of neointimal thickening after local delivery of advanced c-myc antisense at six months follow-up in a rabbit balloon injury model

BACKGROUND

Neointimal hyperplasia following percutaneous transluminal coronary angioplasty (PTCA) is one of the major components of the process of restenosis. We evaluated the long-term impact of local delivery of c-myc neutrally charged antisense oligonucleotides (Resten-NG) upon neointimal formation following PTCA in a rabbit model.

METHODS

PTCA was performed in the iliac arteries of 10 New Zealand white rabbits at 8 atm for 30 s, three times. An infusion of 500 micro g Resten-NG (n=6) or saline (n=4) was delivered to the site at 2 atm via the outer balloon pores of the transport catheter over 2 min. The diet was supplemented with 0.25% cholesterol for 10 days before and 6 months following PTCA.

RESULTS

After 6 months, animals were sacrificed and vessels were fixed in formalin, processed and stained with hematoxylin, eosin, and movat. Histological analysis revealed complete vascular healing in both groups of animals. Planimetry showed that intimal areas were 1.71+/-0.25 and 0.65+/-0.36 mm2 in the control and antisense delivery groups, respectively (P<.05).

CONCLUSION

We conclude that local delivery of Resten-NG significantly inhibited neointimal thickening following PTCA in a rabbit for up to 6 months.