Entering a new era in vascular and cardiac regeneration research
AstraZeneca is pushing the boundaries of science in a new era of vascular and cardiac regeneration research. As we move novel therapeutic modalities from the laboratory into clinical trials, we are focusing on the repair and regeneration of tissues with the potential to treat life threatening cardiovascular diseases such as heart failure.
“Millions of people around the world7 are currently living restricted lives due to heart failure, which has a prognosis worse than some forms of cancer2. It is therefore incredibly exciting that our regeneration research is addressing the underlying damage to heart muscle that causes this devastating disease,” said Regina Fritsche-Danielson, Vice President and Head of Cardiovascular, Renal and Metabolism, IMED Biotech Unit.
Our pioneering research is based on:
• Major scientific advances in understanding of vascular biology and the biological action of vascular endothelial growth factor A (VEGF-A) in stimulating formation of new blood vessels and helping to repair damaged heart muscle
• Exciting scientific developments in mRNA technology to boost production of VEGF-A in areas of the heart
The vascular and cardiac regeneration initiative brings together the complementary skills and expertise of scientists from AstraZeneca and Moderna Therapeutics. This important collaboration, which began in 2013, is advancing the science of tissue regeneration for cardiovascular and metabolic diseases and in other therapy areas. It is rapidly translating laboratory findings into clinical trials of novel therapeutic modalities.
“Our collaboration is so fruitful because we share the same sense of urgency and passion to develop medicines to meet the unmet needs of patients. Within our collaboration, AstraZeneca brings unparalleled depth of understanding of cardiovasular disease biology and the discovery and development of medicines in this area, while Moderna brings advanced mRNA technology and the ability to engineer multiple different mRNAs into therapeutic proteins,” said Tal Zaks, Chief Medical Officer, Moderna Therapeutics.
For the estimated 26 million people worldwide with heart failure1, recent scientific progress in blood vessel and heart muscle regeneration may lead to new ways of treating their disease.
Each year, over a million people are admitted to hospital with heart failure in Europe and the USA, making it the leading cause of hospitalisation in these parts of the world.1 Indeed, heart failure specialists frequently talk about ‘an epidemic of heart failure’. This is due to the fact that although more people are surviving heart attacks than ever before, they are being left with serious damage to their heart muscle. In addition, a growing number of people are living into old age, by which time their heart becomes diseased and works less efficiently.
Despite significant advances in treatment over the last three decades, up to 45% of people with heart failure worldwide die within a year of being discharged from hospital, and the majority within five years.2 Unfortunately, heart failure currently has a worse prognosis than many forms of cancer.2
This is why major scientific advances in cell biology related to growth of new blood vessels and muscle cells in the heart are so exciting.
Not so long ago, we assumed that heart failure was an almost inevitable consequence of damage to or death of cells in the heart’s main pumping chamber, the left ventricle, caused by lack of oxygen due to an impaired blood supply. However, we now know that there may be ways to help regeneration of blood vessels around heart muscle cells that are damaged by a heart attack or by high blood pressure or other cardiovascular problems that occur as people get older.
VEGF-A – growing new blood vessels in the heart
At AstraZeneca, an important focus of our Cardiovascular, Renal and Metabolism (CVRM) research programme is vascular endothelial growth factor A (VEGF-A) – a protein that stimulates formation of new blood vessels and protects heart muscle cells (cardiomyocytes) from dying.
In 2010, we established a multidisciplinary cardiac regeneration team to gain a deeper understanding of the targets and pathways involved in repair of damaged heart muscle, including how VEGF-A-based treatment might be used to help patients with heart failure.
For more than 20 years, other researchers have tried to turn VEGF-A into a treatment for heart disease. They have used systemic injections of recombinant VEGF-A protein to try to improve the blood supply to damaged heart muscle. They have also tried conventional gene therapy to deliver sequences of DNA with the genetic blueprint that cells need to make VEGF-A. But all these previous efforts have met with limited success.
‘Naked’ mRNA – a breakthrough for VEGF-A expression
Since 2013, AstraZeneca has collaborated with Moderna Therapeutics on a different approach. This involves using messenger RNA (mRNA) – the ‘middle man’ in the process by which genetic information contained in DNA is transferred to make proteins. Through this collaboration, we are testing the effects of injections of VEGF-A mRNA into heart tissue to trigger production of the protein.
In preclinical studies, we have seen new blood vessels appearing at the borders of half-dead heart muscle. This was in response to injections of VEGF-A modified mRNA that are carefully targeted at areas where oxygen levels were low. More than that, we have also seen improved cardiac function in these preclinical models as a result of the improved blood and oxygen supply being delivered to the heart.
By using the mRNA approach, we aim to maintain precise control over how much VEGF-A is made. This reduces the risk of side effects such as leaky blood vessels and tissue oedema which can appear if the VEGF-A signal is turned on for too long.
Perhaps the biggest breakthrough of our research came when we discovered we can inject ‘naked’ mRNA contained in a simple buffer solution into the heart muscle. This means there is no need to first wrap it in lipid nanoparticles or other protective coatings to protect it from enzymes in the blood that could break down the mRNA before it reached the inside of cells where it acts. This was an unexpected and exciting finding as it appears that significant uptake of ‘naked’ mRNA is only possible in both skin and heart tissue.
Where next for regeneration therapy?
There are a number of obvious areas to explore for the potential of regeneration therapy. In chronic kidney disease (CKD), there is loss of small blood vessels, and the prospect of developing a mRNA-based therapy to enhance VEGF-A protein production is therefore attractive.
Skin grafting for serious burns and other complex wounds is another area with great potential, given the need for new blood vessel formation in such patients. All too often, patients currently lose skin grafts or suffer serious scarring owing to poor oxygenation of new tissues.
Combining VEGF-A with other growth factors in mRNA therapy is another potentially interesting approach. For example, if we could combine VEGF-A with a cardiomyocyte proliferation factor in a single mRNA injection, we would be able to address the need for both new blood vessels and new cardiac muscle cells in patients with heart failure.
Leading a team from the start of our regeneration programme has been hugely rewarding. We have had to overcome a lot of scepticism within the science community about whether such an approach could possibly work in heart failure. But, working with Moderna, we are delighted to have already made significant progress and we believe this is just the beginning for human vascular and cardiac regeneration therapies.
Vascular endothelial growth factor A (VEGF-A) plays a pivotal role in ensuring adequate blood supply to all parts of the body. It is a naturally occurring protein secreted from many different types of cells, including:3
• Endothelial cells that line the inner surface of blood vessels
• Stem cells that can develop into many different types of cells
• Heart muscle cells (cardiomyocytes)
When VEGF-A binds to receptors, notably VEGFR-1 and VEGFR-2, it generates signals that promote proliferation, differentiation and assembly of all the types of cells needed to make new blood vessels. This happens from the early stages of embryo development and throughout life to replace diseased or damaged blood vessels. 3
VEGF-A plays an important role in ‘homing’ mechanisms that attract stem cells and get them to migrate to sites where they are needed to differentiate into specific cells such as cardiomyocytes in heart muscle. 3
It is also involved in dilation of blood vessels, via stimulation of nitric oxide release from vascular endothelium. This process helps to improve blood flow to heart muscle.3
It has been implicated in inducing a ‘fate switch’ in epicardial progenitor cells, directing them away from the default fibroblast lineage and into vascular cell types. 4
VEGF-A and heart failure
Dysfunctional blood vessel regulation is a key component of heart failure. 3 The muscle of the left ventricle, which pumps blood around the body, becomes enlarged in an effort to keep up with demand. This is associated with reduction in density of blood capillaries supplying oxygen to the muscle (vascular rarefaction) and continuing deterioration of cardiac function.3
In the early stages of heart failure, VEGF-A production increases in response to reduced oxygen supply to heart muscle. However, as the disease progresses, levels gradually run low.3
Potential of VEGF-A therapy in heart failure
VEGF-A therapy has the potential to improve heart failure by:
• Stimulating blood vessel growth in the border zone around damaged heart muscle
• Improving the function of damaged blood vessels and their ability to dilate and increase blood flow in response to the need for oxygen
• Recruiting stem cells that are circulating in the bloodstream and encouraging them to migrate through blood vessel walls into the heart where they secrete more VEGF-A and other growth factors that contribute to repair and regeneration
• Enhancing blood vessel formation by inducing a ‘fate switch’ in epicardial progenitor cells towards vascular cell types
The driving forces behind VEGF-A research in heart failure are the clear unmet need for treatment in the ageing population and the realisation that, by increasing VEGF-A production close to damaged heart muscle, we really do have the exciting opportunity for cardiac regeneration.
Messenger ribonucleic acid (mRNA) is an essential part of the process by which genes in the form of deoxyribonucleic acid (DNA) are decoded (expressed) to make proteins.5
In the first step, called transcription, double stranded DNA in the nucleus of the cell acts as a template for formation of single stranded mRNA.5 This then carries the genetic code to the cell’s protein-making machinery, the ribosomes, where it is ‘translated’ into the amino acid building blocks of protein.5
mRNA was discovered in the late 1960s when scientists were trying to understand the role of genes in protein synthesis. 6 However, it is only recently that its potential has been recognised as a new therapeutic modality to enable the body to produce proteins, such as growth factors, hormones and enzymes, wherever they are needed.
mRNA sequences for proteins, such as vascular endothelial growth factor A (VEGF-A), are now being synthesised in the laboratory. When they are injected into cells they move towards ribosomes, just as they would if they had been produced naturally in the nucleus. The ribosomes then assemble chains of different amino acids according to the instructions from the mRNA.
When complete, these chains of amino acids form proteins with the same structure as those made when the cell starts with its own DNA instead of the mRNA injection.
To improve the uptake and activity of mRNA-based therapeutics such as VEGF-A, scientists are modifying the three main regions of mRNA. They are modifying the ‘cap’ region to improve translational efficiency so more protein is made per molecule, the poly A ‘tail’ region to increase the molecule’s stability, and the ‘middle’ region that holds the protein code so the recipient’s immune system is less likely to see it as foreign and react against it.
In AstraZeneca’s vascular and cardiac regeneration programme, carefully targeted injections of VEGF-A mRNA have already shown promising effects on growth of blood vessels in pre-clinical heart failure models and encouraging safety, tolerability and proof of mechanism data in early clinical studies.
Using mRNA to redirect the cell to make a therapeutic protein sounds simple enough, but we’ve had to reinvent some of the science to ensure that cells don’t reject our mRNA as foreign. As a result, they now recognise our mRNA as something that they would make themselves, and they use it to produce a protein with potential therapeutic benefits, such as VEGF-A.
From the moment in March 2013 that AstraZeneca and Moderna Therapeutics announced an agreement to discover, develop and commercialise mRNA therapeutics, scientists across the groundbreaking team have relished the open, honest and energetic nature of the fast-moving collaboration.
“The key to the success of the collaboration has been the closeness of our interactions and being able to talk openly about our challenges and share our data. It has meant that we’ve been able to make rapid progress towards our common goal, and it’s been a lot of fun talking science with such a great team of people,” explained Regina Fritsche-Danielson, Vice President and Head of Cardiovascular, Renal and Metabolism, IMED Biotech Unit.
Tal Zaks, Chief Medical Officer, Moderna, shares Regina’s enthusiasm for the high-performing research collaboration:
“It’s been super exciting to partner with a team that completely shares your motivation, passion and sense of urgency and brings a competency set that’s so complementary to ours. When we get together, we have a really deep and common understanding of the potential for the discovery and development of mRNA medicines.”
Focused on new treatments for serious cardiovascular, metabolic and renal diseases, and cancer, AstraZeneca is leading preclinical, clinical development and if succesful commercialisation of the novel mRNA-based treatments emerging from the collaboration, while Moderna is responsible for designing and manufacturing mRNAs against selected targets.
Showing signs of a perfect match, in January 2016 the companies announced a new agreement to co-develop and co-commercialise mRNA candidates for the treatment of a range of cancers. This included two research programmes in immuno-oncology, in which AstraZeneca has industry-leading expertise.
In July 2016, AstraZeneca filed a Clinical Trial Application in Germany to initiate a Phase I clinical trial in cardiovascular disease with a VEGF-A mRNA under development as part of the collaboration and are now continuing with a Phase 2a study.
“Nobody has ever worked before on the VEGF modalities and mechanism of action the way we are doing it within our collaboration, constantly challenging each other so that we can be successful in reaching our ultimate goal of helping patients in need of better care,” said Anna Collén, Senior Project Director in Pharmaceutical Sciences, IMED Biotech Unit.
Following the completion of this first ever clinical trial of an mRNA therapeutic in cardiovascular disease, the AstraZeneca-Moderna team is poised for further joint developments in vascular and cardiac regeneration research. AstraZeneca and Moderna recently announced a second strategic agreement in the cardiometabolic space, whereby the companies will advance an mRNA therapeutic encoding for the hormone relaxin as an investigational treatment for heart failure.
“We really are sailing in uncharted waters – working with new science for which no one has written a textbook. In the last four years, we’ve moved from a simple proposal about mRNA to clinical trials of a potential medicine, thanks to a collaboration that has brought together all the tools we needed to get from the laboratory to the patient,” said Li-Ming Gan, Senior Medical Director, Early Clinical Development, Cardiovascular, Renal and Metabolism, IMED Biotech Unit.
Tal Zaks Chief Medical Officer, Moderna Therapeutics
When I started my working life in a pediatric intensive care unit, I could not possibly have imagined that, 30 years later, I would be living through a phenomenal scientific revolution in which we are using mRNA to give the instructions a cell uses to make proteins. Even as recently as 2003, when the human genome was cloned and we were all brimming with curiosity about what it meant for DNA-based therapies, I do not think we realized that mRNA therapeutics would prove so attractive.
The beauty of mRNA therapy is that it acts locally and transiently. We are not trying to integrate it into a person’s genome, as we would with DNA, and make a permanent change. What we are doing is trying to accelerate and improve what the body does on its own.
With VEGF-A mRNA in heart failure, we are aiming to boost the body’s own healing mechanisms. We know, for example, that the body produces more VEGF-A after a heart attack to try and prevent heart muscle damage. We have also seen that there is a fine line between the amount of muscle damage that has very little effect on a patient’s life and the amount that leaves them waking up at night short of breath and unable to live normally.
Our preclinical and pathophysiological models suggest that, following a heart attack, a single intervention could have the potential to allow a patient to produce enough VEGF-A, for long enough after an injection, to enable them to ‘self-heal’ and not be left with potentially life-changing heart failure.
Injecting someone with mRNA very precisely into their heart after a heart attack may sound scary. But cardiologists already routinely put drug-eluting stents into the coronary arteries and carry out bypass surgery. We expect such targeted treatment will not be a barrier to mRNA therapy for heart failure.
Moderna’s collaboration with AstraZeneca to discover and develop a potential mRNA therapy for heart failure has been very productive, as our teams have a shared sense of mission and urgency but complementary skills and competencies. At Moderna, we have had success in producing our mRNA with the right process and purity so that the immune cells did not see them as invader and attack them, while AstraZeneca’s expertise in drug delivery and cardiovascular medicine has enabled VEGF-A mRNA therapy to move into clinical trials.
To successfully get mRNA therapies into cells, we have worked through a lot of research steps. These have included optimising the chemistry of the mRNA and the way we make it and formulating it into a drug that gets through cell membranes. No single advance has provided all the answers, and we have needed a pharmaceutical engineering mind-set to work out how to solve all the problems. The good news is that, like digital software, our optimized mRNA platform is highly reproducible and we can use it again and again to make mRNAs for different proteins.
In collaboration with AstraZeneca, we are now moving ahead with the development of a relaxin mRNA for the treatment heart failure. Relaxin is a natural hormone that works during pregnancy to enable a woman’s cardiovascular system to adjust to her need for increased blood volume and cardiac output. We want to use mRNA to boost production of relaxin in people with heart failure to achieve a similar effect in increasing cardiac output to meet the body’s needs. A recombinant protein form of relaxin has already been tested in heart failure but failed to improve outcomes. We believe that this is because relaxin has a short half-life, and it is not practical to infuse it for a long enough period to achieve the required effects. We want to develop an mRNA which results in production of a form of relaxin that has an extended half-life so tissue exposure will be longer and, hopefully, will result in a clinical benefit.
In the longer term, we envision patients being given combinations of mRNA therapies to treat cardiovascular and other diseases. As scientists, we tend to take a reductionist approach to treatment whereby we address one target at a time. But the body does not work like that. It is continually using dozens of mRNAs to simultaneously make dozens of proteins. Based on our experience at Moderna of using multiple mRNAs for vaccines, we believe that it should be relatively straightforward to extend that approach and combine mRNAs for future drug therapies. The challenge will come in choosing the right combination, in the right ratio.
As we move forward with mRNA therapies, our main priority should be to marry the exciting scientific innovations we are making with the unmet clinical needs that are still, in the real world, leading to significant numbers of deaths and limiting people’s lives.
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2. World Heart Failure Alliance. Heart failure: preventing disease and death worldwide, 2014
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