Gene Therapy For Heart Failure Research Articles

B-Type Natriuretic Peptide Inhibits the Expression and Function of SERCA2a in Heart Failure.

B-type natriuretic peptide (BNP) possesses protective cardiovascular properties; however, there has not been sufficient serious consideration of the side effects of BNP. As for sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), it was once considered a new target for the treatment of heart failure (HF). Nevertheless, clinical trials of SERCA2a gene therapy in HF have finally become unsuccessful. Research has found that elevated BNP levels and decreased SERCA2a expression are two important HF characteristics, which are always negatively correlated. We hypothesize that BNP inhibits SERCA2a expression and, therefore, exerts negative effects on SERCA2a expression and function.The effects of BNP on endogenous SERCA2a expression and function were tested in mice with HF induced by transverse aortic constriction and neonatal rat cardiomyocytes (NRCM). Furthermore, to verify the effects of BNP on exogenous SERCA2a gene transduction efficacy, BNP was added to the myocardium and cardiomyocytes infected with an adenovirus overexpressing SERCA2a.In vivo, BNP levels were increased, SERCA2a expression was reduced in both the BNP intervention and HF groups, and BNP reduced the overexpressed exogenous SERCA2a protein in the myocardium. Our in vitro data showed that BNP dose-dependently inhibited the total and exogenous SERCA2a expression in NRCM by activating the cGMP-dependent protein kinase G. BNP also inhibited the effects of SERCA2a overexpression on Ca2+ transience in NRCM.The expression and function of endogenous and exogenous SERCA2a are inhibited by BNP. The opposite relationship between BNP and SERCA2a should be given serious attention in the treatment of HF via BNP or SERCA2a gene therapy.

Abstract 16778: Design of a Pan Heart Failure Gene Therapy by Targeting Telomere-p53 Axis

Introduction: Cardiovascular disease and heart failure is among the top causes of morbidity and mortality worldwide with a critical need for innovative therapies to reverse the course of ventricular dysfunction. We established that heart failure cardiomyocytes exhibit telomere uncapping and shortening, which leads to DNA damage p53 activation and inhibition of mitochondrial biogenesis. Hypothesis: We hypothesize that reprotection of telomeric ends can prevent p53-induced mitochondrial dysfunction and restore cardiac function. Methods: We designed a pan-HF gene therapy (AAV9-modhTERT) - that acts through telomeric reprotection to turn off p53 and restore myocardial mitochondrial biogenesis - and validate safety and efficacy in Ang II and TAC heart failure murine models. Cardiac specificity in human induced pluripotent stem cell derived cardiomyocytes, biodistribution in mice, and dose titration studies on Ang II and TAC mice were performed. Results: One dose of AAV9-modhTERT sufficiently improved ejection fraction by ~20%, prevented cardiac fibrosis and expression of HF biomarkers. Molecularly, AAV9-modTERT blocked DNA damage activation, reversed mitochondrial biogenesis, restored mitochondrial ultrastructure and respiration, and reversed transcriptomic profiles. Conclusions: These preclinical studies demonstrate considerable potential for the first pan-HF single-dose gene therapy that can reverse cardiac function and prevent myocardial remodeling which would be invaluable clinically and an Investigator Initiated Trial (IIT) (NCT05837143) was launched in April 2023.

Gene therapy for heart failure: A novel treatment for the age old disease

Across the globe, cardiovascular disease (CVD) is the leading cause of mortality. According to reports, around 6.2 million people in the United states have heart failure. Current standards of care for heart failure can delay but not prevent progression of disease. Gene therapy is one of the novel treatment modalities that promises to fill this limitation in the current standard of care for Heart Failure. In this paper we performed an extensive search of the literature on various advances made in gene therapy for heart failure till date. We review the delivery methods, targets, current applications, trials, limitations and feasibility of gene therapy for heart failure. Various methods have been employed till date for administering gene therapies including but not limited to arterial and venous infusion, direct myocardial injection and pericardial injection. Various strategies such as AC6 expression, S100A1 protein upregulation, VEGF-B and SDF-1 gene therapy have shown promise in recent preclinical trials. Furthermore, few studies even show that stimulation of cardiomyocyte proliferation such as through cyclin A2 overexpression is a realistic avenue. However, a considerable number of obstacles need to be overcome for gene therapy to be part of standard treatment of care such as definitive choice of gene, gene delivery systems and a suitable method for preclinical trials and clinical trials on patients. Considering the challenges and taking into account the recent advances in gene therapy research, there are encouraging signs to indicate gene therapy for heart failure to be a promising treatment modality for the future. However, the time and feasibility of this option remains in a situation of balance.

Barriers in Heart Failure Gene Therapy and Approaches to Overcome Them.

Barriers in Heart Failure Gene Therapy and Approaches to Overcome Them.

Cas9/AAV9-Mediated Somatic Mutagenesis Uncovered the Cell-Autonomous Role of Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2 in Murine Cardiomyocyte Maturation.

Sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) is a key player in cardiomyocyte calcium handling and also a classic target in the gene therapy for heart failure. SERCA2 expression dramatically increases during cardiomyocyte maturation in the postnatal phase of heart development, which is essential for the heart to acquire its full function in adults. However, whether and how SERCA2 regulates cardiomyocyte maturation remains unclear. Here, we performed Cas9/AAV9-mediated somatic mutagenesis (CASAAV) in mice and achieved cardiomyocyte-specific knockout of Atp2a2, the gene coding SERCA2. Through a cardiac genetic mosaic analysis, we demonstrated the cell-autonomous role of SERCA2 in building key ultrastructures of mature ventricular cardiomyocytes, including transverse-tubules and sarcomeres. SERCA2 also exerts a profound impact on oxidative respiration gene expression and sarcomere isoform switching from Myh7/Tnni1 to Myh6/Tnni3, which are transcriptional hallmarks of cardiomyocyte maturation. Together, this study uncovered a pivotal role of SERCA2 in heart development and provided new insights about SERCA2-based cardiac gene therapy.

Abstract 10631: Exosome-Encapsulated Adeno-Associated Viruses as a Novel Cardiotropic Vector for Gene Therapy in Heart Failure

Adeno-associated viruses (AAVs) are the vectors of choice for long-term delivery of genes to the heart and due to their safety in clinics. Despite its many favorable features, a notable drawback is the presence of preexisting neutralizing antibodies (NAb), which bind to free AAVs and impair their clinical effect. Here, we describe delivery of AAVs encapsulated in extracellular vesicles (eAAV), as a superior cardiac gene delivery system that offers higher NAb resistance. Methods: Ultracentrifuge-isolated eAAVs were characterized using TEM, DLS, qNano, nanoflow cytometry, ExoView, qPCR and Western blot. Gene delivery efficacy of free AAV and eAAVs were compared with and without NAbs using human cardiomyocytes in vitro, and in mice in vivo, using flow cytometry (with mCherry) and bioluminescence imaging (with luciferase). Therapeutic efficacy of gene delivery by free AAV and eAAV in presence and absence of NAb was determined using a cardiac contractile gene SERCA2a in a mouse model of myocardial infarction (MI). eAAV uptake and trafficking was studied both in vitro and in vivo using fluorescence dye-labeled eAAV. Results: eAAV outperformed free AAV in delivering genes even in the presence of NAbs, both in vitro and in vivo. SERCA2a delivered by eAAV significantly improved cardiac function (ejection fraction, %EF, ~60%) compared to when delivered by free AAV (~40%) or saline control (~20%), in intramyocardially injected MI mice with NAb. Fluorescence-tagged eAAVs injected to mouse hearts were internalized into all cell types (CMs and non-CMs), but, eAAV-mCherry was primarily expressed in CMs, indicating that eAAV-mediated gene delivery is cardiotropic. eAAVs were uptaken in to acidic endosomal (Rab5 & 7 positive) compartments of cultured cardiomyocytes and delivered significantly higher amounts of luciferase to the nucleus of human CMs compared to free AAVs. This uptake of eAAVs was inhibited by the proton pump inhibitor in endosomes, Bafilomycin A1. Conclusion: Our study demonstrated that eAAV-mediated gene delivery can circumvent neutralizing antibody (NAb) issue for gene therapy. eAAVs are cardiotropic and deliver genes to the nucleus via uptake into acidic endosomes. eAAV is a superior gene delivery vector and a new platform to treat heart failure.

Abstract MP101: Functional Maintenance of the Sarcomere Requires Bag3-dependent Autophagy

Bcl2-associated athanogene-3 (BAG3) is a pro-autophagy co-chaperone highly expressed in the heart. Clinical studies show BAG3 haploinsufficiency and mutations are associated with heart failure (HF). However, these studies are largely observational and fail to go beyond the observed phenotype and study mechanism. One study in neonatal myocytes suggests a role for BAG3 in structural maintenance of the sarcomere. However, the structural and functional significance of BAG3 in adult myocytes is not known. We found that myofilament BAG3 expression decreases in human heart failure and is associated with impaired myofilament force-generating capacity (F max ). To assess whether rescuing BAG3 levels could restore function, we used a mouse model of HF and treated with BAG3 gene therapy via AAV9. Myofilament function was assessed in skinned cardiomyocytes by force-calcium relationship. HF mice experienced a reduction in F max , but this was fully restored to sham levels by BAG3 gene therapy.To explore mechanism, we used mass spectrometry to identify the BAG3-interactome at the myofilament and found heat shock proteins (HSP) 70 and B8 among the top hits. Immunofluorescence further showed that HSP70, B8, and BAG3 each localized to the sarcomere z-disk. This BAG3-Hsp complex had previously been described to promote ubiquitin-dependent autophagy in skeletal muscle. Notably, in both human HF samples and in the mouse HF model, myofilament ubiquitin levels increased significantly. However, BAG3 gene therapy in HF reduces ubiquitin levels and restores autophagy flux. This suggests that BAG3 serves a role in proteostasis for the sarcomere, which may explain the functional effect of BAG3 gene therapy.To further explore the impact of the BAG3/HSP complex on myofilament function, we used a mouse model with the P209L BAG3 mutation, which had previously been described to disrupt client processing by the complex. We found cardiomyocytes from P209L mice had significantly reduced F max and elevated myofilament ubiquitin levels, suggesting BAG3-dependent autophagy is required to maintain function. Together, our data identify a functional role for BAG3 at the sarcomere and indicate BAG3-mediated autophagy is an important mechanism for maintaining myofilament proteostasis.

Viral expression of a SERCA2a-activating PLB mutant improves calcium cycling and synchronicity in dilated cardiomyopathic hiPSC-CMs

There is increasing momentum toward the development of gene therapy for heart failure (HF) that is defined by impaired calcium (Ca2+) transport and reduced contractility. We have used FRET (fluorescence resonance energy transfer) between fluorescently-tagged SERCA2a (the cardiac Ca2+ pump) and PLB (phospholamban, ventricular peptide inhibitor of SERCA) to test directly the effectiveness of loss-of-inhibition/gain-of-binding (LOI/GOB) PLB mutants (PLBM) that were engineered to compete with the binding of inhibitory wild-type PLB (PLBWT). Our therapeutic strategy is to relieve PLBWT inhibition of SERCA2a by using the reserve adrenergic capacity mediated by PLB to enhance cardiac contractility. Using a FRET assay, we determined that the combination of a LOI PLB mutation (L31A) and a GOB PLB mutation (I40A) results in a novel engineered LOI/GOB PLBM (L31A/I40A) that effectively competes with PLBWT binding to cardiac SERCA2a in HEK293-6E cells. We demonstrated that co-expression of PLBM enhances SERCA Ca-ATPase activity by increasing enzyme Ca2+ affinity (1/KCa) in PLBWT-inhibited HEK293 cell homogenates. For an initial assessment of PLBM physiological effectiveness, we used human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) from a healthy individual. In this system, we observed that adeno-associated virus 2 (rAAV2)-driven expression of PLBM enhances the amplitude of SR Ca2+ release and the rate of SR Ca2+ re-uptake. To assess therapeutic potential, we used a hiPSC-CM model of dilated cardiomyopathy (DCM) containing PLB mutation R14del, where we observed that rAAV2-driven expression of PLBM rescues arrhythmic Ca2+ transients and alleviates decreased Ca2+ transport. Thus, we propose that PLBM transgene expression is a promising gene therapy strategy that directly targets the underlying pathophysiology of abnormal Ca2+ transport and thus contractility in underlying systolic heart failure.

Abstract 270: Loss of S100A1 Protein Negatively Impacts Glucose Metabolism and Energy Homeostasis in Cardiomyocytes

Introduction: As a true metabolic omnivore, the heart is able to utilize different substrates for energy production. In the hypertrophied and early failing state, cardiac muscle leans towards glucose as a major carbon substrate to meet its energetic demand. Given that S100A1 gene therapy reverses the compromised energetic balance of the failing heart, we were interested in determining the specific role of the EF-hand calcium sensor S1001A1 in cardiomyocyte energy metabolism. Methods and results: To study metabolic changes in response to different carbon substrates, we used neonatal rat ventricular cardiomyocytes (NRVMs), which were subjected to electrical stimulation (2Hz) in culture and adenoviral-mediated anti-S100A1 shRNA silencing or scr-shRNA, and either fed with glucose, oleate or lactate only for 24hrs. Of note, lack of S100A1 expression only impaired energy metabolism of cardiomyocytes in response to glucose as reflected by a significantly decreased ATP content and subsequently enhanced AMP/ATP and p-AMPK/AMPK ratios with consecutive elevated p-ACC/ACC and Glut4 protein levels. In contrast, energy metabolism appeared to remain normal in response to oleate in S100A1-deprived cells. Targeted metabolomics yielded a tremendous decrease in glucose-6-phosphate levels as the first key step in glucose metabolism despite enhanced AMPK activation in glucose-fed S100A1-defiecient cardiomyocytes. Conclusion: Our novel in vitro data indicate that S100A1 protein may be crucial for cardiomyocytes to meet their energetic demand when glucose is the major substrate. Since the latter becomes the preferred substrate for functionally compromised heart over fatty acids, lack of S100A1 expression - as a result of fetal gene reprogramming - most likely impairs the ability of the heart to sufficiently utilize glucose to meet its energetic demand. These data shed new mechanistic light on the sustained therapeutic efficacy of S100A1 gene therapy of heart failure where S100A1 may be a key factor enabling the heart to sufficiently use glucose to reverse its compromised energetic state. Further studies answering these pressing questions are underway for an informed design of a best-case patient enrollment scenario for a first-in-men clinical study.

Current Landscape of Heart Failure Gene Therapy.

Gene therapy for patients with HF is now on the cusp of being successfully translated from the laboratory to the clinical arena. It is no longer a theoretical vision, but a realistic opportunity for the future treatment of patients with HFrEF. This transition is attributed to an increased understanding of the optimization of the various AAV serotypes, a better understanding of the efficacy of the various cardiac‐restricted promoters, and clarification of the most effective delivery systems. Although recent studies in humans did not prove efficacious, they were of great importance because they demonstrated the safety of gene therapy and defined the methods for gene delivery. Nonetheless, challenges remain. First, the development of AAVs that are nonimmunogenic will allow treatment of patients with preexisting AAV antibodies and will obviate, or at least lessen, the risk of the development of adaptive immunity. Second, the construction of AAVs that can package large genes will facilitate the generation of new therapies for individuals with mutations that are not currently approachable (eg, titin and lamin) or that require indirect approaches. Third, the identification of new HFrEF‐causing mutations in large‐scale genomic studies, such as the recently initiated All of Us study, will expand the number of patients who can benefit from gene therapy. And, finally, development of highly cardiac trophic vectors may allow therapy to be delivered intravenously rather than intracoronary with comparable or greater efficiency of transduction.

Cardiac gene therapy of heart failure with phosphodiesterase PDE4B in mice

Chronic beta-AR activation is detrimental because it promotes cardiac remodeling and ultimately leads to heart failure (HF). Multiple cyclic nucleotide phosphodiesterases (PDEs) finely tune beta-AR responses by degrading and compartmentalizing cAMP. Since chronic treatment with PDE inhibitors increases mortality in HF, we postulated that decreasing cAMP levels by overexpressing PDE4B in the heart may have therapeutic effects. To test this hypothesis, we explored whether AAV9-mediated cardiac overexpression of PDE4B (10 12 viral particles) could prevent maladaptive hypertrophy in mice subjected either to transverse aortic constriction (TAC) for 6 weeks or 2 weeks isoproterenol (Iso) and phenylephrine (Phe) infusion (30μg/g/day each). Cardiac function was assessed by echocardiography. In control mice injected with a Luciferase-AAV9 (LUC), TAC decreased ejection fraction (EF, - 34.2 ± 6%, N = 6, P < 0.0001), increased left ventricular weight/body weight ratio (LVW/BW, + 86.7 ± 15.7%, N = 6, P < 0.0001). Although PDE4B overexpression did not ameliorate EF, it delayed the decrease of EF at 2 weeks ( N = 9, P < 0.05), prevented LV hypertrophy ( N = 9, P < 0.001) and fibrosis ( N = 9, P < 0.05). Chronic Iso and Phe treatment induced LV hypertrophy (LVW/BW, + 37.8 ± 6.2%, N = 7, P < 0.001) and decreased EF (- 25 ± 3.5%, N = 7, P < 0.0001). While PDE4B overexpression only slightly ameliorated EF (- 17 ± 3%, N = 9) in this model, LV hypertrophy was significantly diminished ( N = 9, P < 0.05). PDE4B protein level was assessed by western blotting and revealed a ∼6 to 9-fold increased expression in both HF models. We are currently analyzing whether PDE4B overexpression can prevent fibrosis induced by catecholamines and limit ventricular arrhythmias induced by catheter-mediated burst pacing following intraperitoneal injection of isoprenaline. Altogether, our preliminary results suggest that gene therapy with PDE. Chronic ß-AR activation is detrimental because it promotes cardiac remodeling and ultimately leads to heart failure (HF). Multiple cyclic nucleotide phosphodiesterases (PDEs) finely tune ß-AR responses by degrading and compartmentalizing cAMP. Since chronic treatment with PDE inhibitors increases mortality in HF, we postulated that decreasing cAMP levels by overexpressing PDE4B in the heart may have therapeutic effects. To test this hypothesis, we explored whether AAV9-mediated cardiac overexpression of PDE4B (10 12 viral particles) could prevent maladaptive hypertrophy in mice subjected either to transverse aortic constriction (TAC) for 6 weeks or 2 weeks isoproterenol (Iso) and phenylephrine (Phe) infusion (30μg/g/day each). Cardiac function was assessed by echocardiography. In control mice injected with a Luciferase-AAV9 (LUC), TAC decreased ejection fraction (EF, -34.2 ± 6%, N = 6, P < 0.0001), increased left ventricular weight/body weight ratio (LVW/BW, + 86.7 ± 15.7%, N = 6, P < 0.0001). Although PDE4B overexpression did not ameliorate EF, it delayed the decrease of EF at 2 weeks ( N = 9, P < 0.05), prevented LV hypertrophy ( N = 9, P < 0.001) and fibrosis ( N = 9, P < 0.05). Chronic Iso and Phe treatment induced LV hypertrophy (LVW/BW, + 37.8 ± 6.2%, N = 7, P < 0.001) and decreased EF (- 25 ± 3.5%, N = 7, P < 0.0001). While PDE4B overexpression only slightly ameliorated EF (- 17 ± 3%, N = 9) in this model, LV hypertrophy was significantly diminished ( N = 9, P < 0.05). PDE4B protein level was assessed by western blotting and revealed a ∼6 to 9-fold increased expression in both HF models. We are currently analyzing whether PDE4B overexpression can prevent fibrosis induced by catecholamines and limit ventricular arrhythmias induced by catheter-mediated burst pacing following intraperitoneal injection of isoprenaline. Altogether, our preliminary results suggest that gene therapy with PDE4B is a potential therapeutic approach for cardiac maladaptive hypertrophy.4B is a potential therapeutic approach for cardiac maladaptive hypertrophy.

Abstract 16920: Permanent Reduction of Ryr2 Improves Lv Ejection Fraction in Heart Failure

Introduction: Ryanodine receptor type 2 (RyR-2), the main Ca 2+ release channel from sarcoplasmic reticulum in cardiomyocytes, plays an important role in regulation of myocardial contractile function and cardiac hypertrophy. Hypothesis: RyR-2 is a target of gene therapy in heart failure. Methods and Results: Two CRISPR-Cas9 gRNA targeting RyR-2 were identified: one located on the gene N terminal and the other on the C terminal. Adeno-associated virus was used to express CRISPR-Cas9 to knockdown RyR-2 in two weeks transverse aortic constriction (TAC) model of mice. After one week of administration of the virus, compared with the control, cardiac mass, heart size and fibrosis decreased and the LV ejection fraction increased significantly in the model with CRISPR-Cas9 gRNA on the RyR-2 N terminal, and the other one had a similar result but not significantly. Conclusions: Our results hint genome editing with CRISPR-Cas9 disrupts the RyR-2 in vivo with partly restore the function of the heart.

Non-invasive detection of adeno-associated viral gene transfer using a genetically encoded CEST-MRI reporter gene in the murine heart

Research into gene therapy for heart failure has gained renewed interest as a result of improved safety and availability of adeno-associated viral vectors (AAV). While magnetic resonance imaging (MRI) is standard for functional assessment of gene therapy outcomes, quantitation of gene transfer/expression relies upon tissue biopsy, fluorescence or nuclear imaging. Imaging of gene expression through the use of genetically encoded chemical exchange saturation transfer (CEST)-MRI reporter genes could be combined with clinical cardiac MRI methods to comprehensively probe therapeutic gene expression and subsequent outcomes. The CEST-MRI reporter gene Lysine Rich Protein (LRP) was cloned into an AAV9 vector and either administered systemically via tail vein injection or directly injected into the left ventricular free wall of mice. Longitudinal in vivo CEST-MRI performed at days 15 and 45 after direct injection or at 1, 60 and 90 days after systemic injection revealed robust CEST contrast in myocardium that was later confirmed to express LRP by immunostaining. Ventricular structure and function were not impacted by expression of LRP in either study arm. The ability to quantify and link therapeutic gene expression to functional outcomes can provide rich data for further development of gene therapy for heart failure.

Therapeutic Benefit and Gene Network Regulation by Combined Gene Transfer of Apelin, FGF2, and SERCA2a into Ischemic Heart.

Despite considerable advances in cardiovascular disease treatment, heart failure remains a public health challenge. In this context, gene therapy appears as an attractive approach, but clinical trials using single therapeutic molecules result in moderate benefit. With the objective of improving ischemic heart failure therapy, we designed a combined treatment, aimed to simultaneously stimulate angiogenesis, prevent cardiac remodeling, and restore contractile function. We have previously validated IRES-based vectors as powerful tools to co-express genes of interest. Mono- and multicistronic lentivectors expressing fibroblast growth factor 2 (angiogenesis), apelin (cardioprotection), and/or SERCA2a (contractile function) were produced and administrated by intramyocardial injection into a mouse model of myocardial infarction. Data reveal that combined treatment simultaneously improves vessel number, heart function parameters, and fibrosis prevention, due to FGF2, SERCA2a, and apelin, respectively. Furthermore, addition of SERCA2a in the combination decreases cardiomyocyte hypertrophy. Large-scale transcriptome analysis reveals that the triple treatment is the most efficient in restoring angiogenic balance as well as expression of genes involved in cardiac function and remodeling. Our study validates the concept of combined treatment of ischemic heart disease with apelin, FGF2, and SERCA2a and shows that such therapeutic benefit is mediated by a more effective recovery of gene network regulation.

Gene therapy in heart failure: the unexpected results from the CUPID 2 trial

Heart failure is still a major cause of morbidity and mortality in Europe and North America. In the last three decades, gene therapy emerged as a target in the molecular mechanisms implicated in heart failure encouraging preclinical gene therapy studies in small and large animal models. Prior studies documented a decreased expression of sarcoplasmic reticulum Ca2+-ATPase protein (SERCA2a), a major cardiac calcium cycling protein, in heart failure. These results paved the way to preliminary studies based on gene transfer strategies of SERCA2a. The encouraging results in terms of safety and surrogate clinical endpoints led to a large randomized clinical study, the CUPID trial, including patients with heart failure and reduced ejection fraction. This phase IIb trial enrolling 250 patients randomized to intracoronary delivery of adeno-associated virus 1 (AAV1)/SERCA2a or placebo concluded with a non-superiority of the studied therapy, thus not confirming the results of the previous experiences with the same approach. In the present manuscript, we provide an overview of the scientific experiences that preceded the design of this major trial, then critically revising its structure and results. Finally we tried to understand the reasons of this unexpected failure and which are the future perspectives of gene therapy for heart failure.

Gene therapy: No improvement in outcomes with gene therapy for heart failure.

Gene therapy: No improvement in outcomes with gene therapy for heart failure.

Gene therapy for cardiovascular disease: advances in vector development, targeting, and delivery for clinical translation.

Gene therapy is a promising modality for the treatment of inherited and acquired cardiovascular diseases. The identification of the molecular pathways involved in the pathophysiology of heart failure and other associated cardiac diseases led to encouraging preclinical gene therapy studies in small and large animal models. However, the initial clinical results yielded only modest or no improvement in clinical endpoints. The presence of neutralizing antibodies and cellular immune responses directed against the viral vector and/or the gene-modified cells, the insufficient gene expression levels, and the limited gene transduction efficiencies accounted for the overall limited clinical improvements. Nevertheless, further improvements of the gene delivery technology and a better understanding of the underlying biology fostered renewed interest in gene therapy for heart failure. In particular, improved vectors based on emerging cardiotropic serotypes of the adeno-associated viral vector (AAV) are particularly well suited to coax expression of therapeutic genes in the heart. This led to new clinical trials based on the delivery of the sarcoplasmic reticulum Ca2+-ATPase protein (SERCA2a). Though the first clinical results were encouraging, a recent Phase IIb trial did not confirm the beneficial clinical outcomes that were initially reported. New approaches based on S100A1 and adenylate cyclase 6 are also being considered for clinical applications. Emerging paradigms based on the use of miRNA regulation or CRISPR/Cas9-based genome engineering open new therapeutic perspectives for treating cardiovascular diseases by gene therapy. Nevertheless, the continuous improvement of cardiac gene delivery is needed to allow the use of safer and more effective vector doses, ultimately bringing gene therapy for heart failure one step closer to reality.

41 Gene Therapy for Heart Failure: The Challenge of Neutralising Antibodies: Abstract 41 Table 1

Introduction The treatment of heart failure is entering a new era with the potential for gene therapy to directly target the underlying molecular abnormalities of the failing myocyte. One barrier to delivering gene therapy is the exclusion of patients who have neutralising antibodies (nAbs) to the recombinant viral vector due to previous exposure to the wild type virus. Aims To review the prevalence of nAbs against adeno-associated virus serotype 1 (AAV1) in published literature and to prospectively determine the prevalence of nAbs in a UK cohort of heart failure patients. Methods We reviewed the literature using the following search terms on Pubmed: (prevalence, neutralising antibodies, adeno-associated virus, AAV) which resulted in 19 studies. Five of these studies were suitable and provided data for 14 countries and a total of 1984 people. In addition, a total of 155 samples from heart failure patients at our institution were analysed for the presence of nAbs using a titre cut-off of 1:2. Results Globally there is a wide variation in the prevalence of nAbs to AAV1, ranging from 13 to 79%. These data are generally from young healthy volunteers and there is no standard cut-off for what titre constitutes a nAb positive result, though a titre cut-off of 1:20 was used in most of these studies. From our UK based heart failure cohort, 60.6% of patients were nAb positive at a titre of 1:2 and hence ineligible for gene therapy. The only characteristic associated with being nAb positive was age with the prevalence of nAbs increasing significantly with age (Table 1). Conclusion If gene therapy proves to be an effective treatment, then currently three-fifths of heart failure patients in the UK may be ineligible to receive it due to presence of nAbs. This barrier seems to be greater in the older patients. Published data on the prevalence of nAbs does, however, suggest there is a wide geographic variation. Strategies are in development to overcome the barrier of nAbs but until these are effective we must be conscious of this limitation when discussing gene therapy as either a research or therapeutic option with our patients in the UK.

The Current and Future Landscape of SERCA Gene Therapy for Heart Failure: A Clinical Perspective

Gene therapy has been applied to cardiovascular disease for over 20 years but it is the application to heart failure that has generated recent interest in clinical trials. There is laboratory and early clinical evidence that delivery of sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) gene therapy is beneficial for heart failure and this therapy could become the first positive inotrope with anti-arrhythmic properties. In this review we will discuss the rationale for SERCA2a gene therapy as a viable strategy in heart failure, review the published data, and discuss the ongoing clinical trials, before concluding with comments on the future challenges and potential for this therapy.

Ribonucleotide reductase-mediated increase in dATP improves cardiac performance via myosin activation in a large animal model of heart failure.

Heart failure remains a leading cause of morbidity, hospitalizations, and deaths. We previously showed that overexpression of the enzyme ribonucleotide reductase (RNR) in cardiomyocytes increased levels of the myosin activator, 2-deoxy-ATP, catalysed enhanced contraction, and improved cardiac performance in rodent hearts. Here we used a swine model of myocardial infarction (MI) to test preliminarily a novel gene therapy for heart failure based on delivery of the human RNR enzyme complex under the control of a cardiac-specific promoter via an adeno-associated virus serotype 6 vector--designated as BB-R12. We induced heart failure following MI in Yucatan minipigs by balloon occlusion of the left anterior descending artery. Two weeks, later, pigs received BB-R12 at one of three doses via antegrade coronary infusion. At 2 months post-treatment, LVEF and systolic LV dimension (measured by echocardiography) improved significantly in the high-dose group, despite further deterioration in the saline controls. Haemodynamic parameters including LV end-diastolic pressure, +dP/dt, and -dP/dt all trended towards improvement in the high-dose group. We observed no difference in the histopathological appearance of hearts or other organs from treated animals vs. controls, nor did we encounter any safety or tolerability concerns following BB-R12 delivery. These pilot results suggest cardiac-specific gene therapy using BB-R12 may reverse cardiac dysfunction by myosin activation in a large-animal heart failure model with no observed safety concerns. Thus further research into the therapeutic potential of BB-R12 for patients with chronic heart failure appears warranted.