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

Abstract

Aims 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-adenosine triphosphate, catalyzed 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. Methods and Results 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 two months post-treatment, left ventricular (LV) ejection fraction and systolic LV dimension (measured by echocardiography) improved significantly in the high-dose group, despite further deterioration in the saline controls. Hemodynamic 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 histopathologic appearance of hearts or other organs from treated animals versus controls, nor did we encounter any safety or tolerability concerns following BB-R12 delivery. Conclusion 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.

Translation of Cardiac Myosin Activation With 2-Deoxy-ATP to Treat Heart Failure Via an Experimental Ribonucleotide Reductase-Based Gene Therapy

“…At the end of the study, there were no gross or microscopic pathological findings in any organ. The results of this pilot cardiac pharmacological study of BB-R12 in an MI/HF swine model extended the findings from rodent pharmacology studies, with safe and sustained increases in global cardiac function observed following a single administration and in a dose-responsive manner(42). …”

“…* P <0.05, ** P <0.01 compared to sham, mixed effects regression model; data represented as mean ± SEM. Figure adapted from Kadota 2015(42). …”

Cardiac Myosin Activation with Gene Therapy Produces Sustained Inotropic Effects and May Treat Heart Failure with Reduced Ejection Fraction

“…At the end of the study, there were no gross or microscopic pathological findings in any organ nor any histopathologic differences in the infarct area. The results of this pilot large animal cardiac pharmacological study of the effects of BB-R12 in an MI/HF swine model extended the findings from rodent pharmacology studies, with safe and sustained increases in global cardiac function observed following a single administration and in a dose-responsive manner (Kadota et al 2015). …”

Fast and sensitive HPLC–MS/MS method for direct quantification of intracellular deoxyribonucleoside triphosphates from tissue and cells

“…We have previously shown that small increases in dATP levels increases cardiac force and rate of force development by altering myosin cycling [31,32]. Our novel gene therapy method increases cardiac intracellular dATP levels by cardiac-specific overexpression of ribonucleotide reductase, the rate-limiting step in the de novo dNTP synthesis pathway, and is shown to increase contractility in rodents and pigs with cardiac dysfunction[32,33]. …”