Preview Mode Links will not work in preview mode

Circulation on the Run


Oct 17, 2022

This week, please join author Sunil Rao and Guest Editor and Editorialist Gregory Lip as they discuss the article "A Multicenter, Phase 2, Randomized, Placebo-Controlled, Double-Blind, Parallel-Group, Dose-Finding Trial of the Oral Factor XIa Inhibitor Asundexian to Prevent Adverse Cardiovascular Outcomes After Acute Myocardial Infarction" and the editorial "Factor XIa Inhibition: Is It a Novel Alternative Antithrombotic Strategy for High-Risk ACS Patients?"

Dr. Carolyn Lam:

Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts. I'm Dr. Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.

Dr. Greg Hundley:

And I'm Dr. Greg Hundley, Associate Editor Director of the Pauley Heart Center at VCU Health in Richmond, Virginia.

Dr. Carolyn Lam:

Greg, today's feature paper is about the factor XI inhibitor asundexian. It's the trial that we've been waiting for the PACIFIC-AMI trial. You really have to listen to it because these factor XI inhibitors are super interesting. What? We're going to tell you about the other papers in today's issue first. Aren't we, Greg? Do you want to go first?

Dr. Greg Hundley:

You bet, Carolyn. Thank you so much. Carolyn, did you ever consider the genetic underpinnings of venous thromboembolism? Well, as you know, venous thromboembolism is a complex disease with environmental and genetic determinants. And in this study, this large investigative team represented by Dr. Nicholas Smith from the University of Washington in Seattle, and their colleagues present new cross-ancestry meta-analyzed genome-wide association study results from 30 studies with replication of novel loci and their characterization through in silicone genomic interrogations.

Dr. Carolyn Lam:

Wow. Sounds like a really large effort, Greg. What did they find?

Dr. Greg Hundley:

Right, Carolyn. In the author's initial genetic discovery effort that included 55,330 participants with venous thromboembolism: 47,000 were European, 6,000 African, and a little over 1000 Hispanic ancestry. They identified 48 novel associations of which 34 are replicated after correction for multiple testing. In their combined discovery replication analysis, so that's 81,669 venous thromboembolism participants and ancestry stratified meta-analyses from the European, African and Hispanic ethnic groups. They identified another 44 novel associations, which are new candidate venous thromboembolism associated loci requiring replication. And many of the replicated loci were outside of known or currently hypothesized pathways to thrombosis. Carolyn, in summary, these findings from this very large GWAS analysis highlight new pathways to thrombosis and provide novel molecules that may be useful in the development of anti-thrombosis treatments with reducing the risk of bleed.

Dr. Carolyn Lam:

Wow. Super interesting and very related to that feature paper that we just discuss. But nonetheless, this next paper I love as well, if I may say so myself. It deals with frailty and as we know, frailty is increasing in prevalence. And because frail patients are often perceived to have a less favorable benefit risk profile, they may be less likely to receive new pharmacological treatments. And so, we and led by Professor John McMurray from the University of Glasgow, decided to investigate the efficacy and tolerability of dapagliflozin according to frailty status in the DELIVER trial.

Dr. Greg Hundley:

The DELIVER trial. Carolyn, tell us about the DELIVER trial?

Dr. Carolyn Lam:

Sure. In deliver dapagliflozin compared to placebo, reduced the risk of worsening heart failure events or cardiovascular death and improved symptoms in more than 6,000 patients with heart failure and mildly reduced and preserved ejection fraction, so ejection fraction above 40%. Now in this pre-specified analysis, we examine the efficacy and safety of dapagliflozin according to frailty status. That was determined using the Rockwood cumulative deficit approach.

And so, what we found was that greater frailty was associated with more impairment of health status and worse clinical outcomes in patients with heart failure and ejection fraction of 40%. The beneficial effects of dapagliflozin compared to placebo on clinical outcomes were consistent regardless of frailty class. But interestingly, the improvement in symptoms, physical function and quality of life were larger in the frailest patients. Adverse events were not more common in individuals randomized to receive dapagliflozin compared to placebo irrespective of frailty class. And so, the take home message is the benefit risk balance related to frailty in patients with heart failure with mildly reduced and preserved ejection fraction is favorable for dapagliflozin. And so, these findings should challenge any clinical reluctance to introduce dapagliflozin in patients perceived to be frail.

Dr. Greg Hundley:

Wow. Carolyn, really interesting. You could see with the diuretic effect in someone that's frail, the potential hesitancy, but very interesting study results in this world of frailty and the use of dapagliflozin. Well, Carolyn, this next study is very interesting and it comes to us from the world of preclinical science that takes a very interesting approach to a scientific question. Now, as you may know, RNA-binding proteins or RBPs are master orchestrators of genetic expression regulation. They regulate hundreds of transcripts at once by recognizing specific motifs, thus characterizing RBPs targets is critical to harvest their full therapeutic potential. However, such investigation has often been restricted to a few RBP targets, thereby limiting our understanding of their function.

Carolyn, these investigators led by Dr. Grégoire Ruffenach from UCLA were interested in assessing pulmonary arterial hypertension and they turned to the world of cancer research. Carolyn, in cancer, the RNA-binding protein hnRNPA2B1, and we're going to abbreviate that as A2B1, promotes a pro proliferative anti-apoptotic phenotype. The same phenotype is present in pulmonary arterial smooth muscle cells and is responsible for the development of pulmonary arterial hypertension. However, the A2B1 function that's never really been investigated in pulmonary arterial hypertension.

Dr. Carolyn Lam:

Oh, Greg, that's not only fascinating, but so beautifully described. Thank you. What did they find?

Dr. Greg Hundley:

Right, Carolyn. These authors found that A2B1 expression and it's nuclear localization are increased in human pulmonary arterial hypertension, pulmonary arterial smooth muscle cells. Using bioinformatics, they identified three known motifs of A2B1 and all mRNAs carrying them and demonstrated the complimentary non-redundant function of A2B1 motifs as all motifs are implicated in different aspects of the cell cycle. In addition, they showed that pulmonary arterial smooth muscle cells and A2B1 promote the expression of its targets. Additionally, in vivo A2B1 inhibition in the lungs rescued pulmonary hypertension in rats. And so, Carolyn, through the integration of computational and experimental biology, this team study revealed the role of A2B1 as a master orchestrator of pulmonary arterial smooth muscle cells in pulmonary hypertension and that phenotype and its relevance as a therapeutic target in pulmonary arterial hypertension.

Dr. Carolyn Lam:

Wow, that's super, Greg. Thanks. Shall we go through what else is in today's issue?

Dr. Greg Hundley:

You bet, Carolyn. There's a Research Letter from Professor Mustroph entitled, “Empagliflozin Inhibits Cardiac Late Sodium Current versus Calcium Calmodulin‐dependent Kinase II.”

Dr. Carolyn Lam:

There's also an exchange of letters between Doctors Omarjee and Diederichsen regarding vitamin K2 and D in patients with aortic valve calcification: [an] absence of evidence might not be evidence of absence? And finally, there's an On My Mind paper by me and Scott Solomon and it's entitled, “Delivering Therapeutic Efficacy Across the Ejection Fraction Spectrum of Heart Failure.” But let's go on now to talk about the Factor XI inhibitor, shall we, Greg?

Dr. Greg Hundley:

You bet. Well, listeners, welcome to this feature discussion on October 18th at a very special article today. And we have with us the lead author, Dr. Sunil Rao from NYU in New York City and also our associate guest editor as well as editorialist, Dr. Gregory Lip from Liverpool. Welcome, gentlemen. Sunil, we'll start with you. Can you describe for us some of the background information that went into the preparation of your study and what was the hypothesis that you wanted to address?

Dr. Sunil Rao:

Yeah, great. Thanks so much, Greg. It's a real pleasure to be here with you. The background of the PACIFIC-AMI study is really rooted in the fact that patients who have acute myocardial infarction are really at risk for recurrent thrombotic events, even after their event. And this risk continues despite the fact that we have evidence based therapies that are really around targeting the platelet as well as aspects of the coagulation cascade. There have been studies that have looked at the use of dual antiplatelet therapy plus an anticoagulant or single antiplatelet therapy plus an anticoagulant. And those studies have shown a benefit. However, their clinical use is limited because of the bleeding risk.

Factor XI is an interesting target, because factor XI is likely involved in the amplification of thrombin generation after plaque rupture. But it really doesn't play much of a role in hemostasis. And so, as a target in reducing events after acute coronary syndrome, activated factor XI is a very attractive one. And so, the hypothesis of this study was that a highly bioavailable oral, direct, selective activated factor XI inhibitor called asundexian would be safe and effective in the treatment of patients who experience acute coronary syndrome at reducing adverse events. Now, this is a phase two study, so it really wasn't powered for clinical events. It was really a dose-finding study, so it was really looking at adverse events and sort of bleeding complications.

Dr. Greg Hundley:

Very nice. Asundexian, a new factor XI inhibitor. And Sunil, can you describe for us your study design and then maybe a little bit more about the study population, how many subjects?

Dr. Sunil Rao:

Sure. Again, this is a phase two study. It was a randomized, double-blind, parallel-group design where patients, who were admitted with acute coronary syndrome were randomized to three different doses of asundexian and or placebo in a one-to-one to one-to-one fashion. Patients who met criteria for enrollment were: patients who were admitted with a diagnosis of acute MI; if they were older than or equal to 45 years of age; they were hospitalized in acute coronary syndrome that did not occur in the context of revascularization, so it was not a type 4 event; and they were planned to be treated with dual antiplatelet therapy after hospital discharge.

Dr. Greg Hundley:

Sunil, thank you for describing this very interesting study design. Now, how many subjects did you include and could you just describe for us the study population?

Dr. Sunil Rao:

We had a total of 1,601 patients that were randomized at 157 centers in 14 countries between June 2020 and July 2021. And in order to be eligible for enrollment into the study: patients had to be admitted with a diagnosis of acute MI, they had to be greater than or equal to 45 years of age, and be hospitalized with that acute MI that did not occur in the context of revascularization, so type 4 MIs were excluded. The other inclusion criteria was that they had to be planned to be treated with dual antiplatelet therapy after hospital discharge. Now, we allowed randomization up to five days after hospital admission and randomization occurred after patients were clinically stabilized and any planned PCI was performed. We included both patients with STEMI as well as non-ST segmental elevation ACS, but we capped the number of patients with STEMI that were included to no more than 50%. Now, the main exclusion criteria were things that you would expect for a phase two trial. Obviously, hemodynamic instability at the time of randomization, active bleeding or bleeding dialysis, severe renal dysfunction, planned use of full-dose anticoagulation.

Dr. Greg Hundley:

Very nice. And so, we have several doses of this new factor XI inhibitor. Describe for us your study results?

Dr. Sunil Rao:

Again, this was a phase two trial that was really looking at safety and adverse events as you would expect. The study groups were pretty balanced across all of the dosing arms. When we looked at the pharmacokinetic and pharmacodynamic data, we found something really interesting, which was that there was a dose relationship between the dose of asundexian and the factor XIa activity. Factor XIa is activated factor XI. The higher the dose, the more suppression of factor XI activity. In fact, the highest dose nearly eliminated factor XI activity. The drug clearly works in the way that it was intended. Now again, the clinical data, it wasn't powered for clinical data. But when we look at the bleeding results, we found that there was in fact an increase in bleeding as the dose of asundexian increased. The overall rate of bleeding in the highest dose of asundexian was in 50 milligrams was 10.5% with type 2 or 3 or 5 BARC bleeding, a placebo is about 9.02%. Again, the efficacy outcomes, very, very low rates of overall events. Again, not powered to show a difference. Essentially, very similar across all the arms.

Dr. Greg Hundley:

And did you find the same results for the men and the women? And what about older individuals and younger individuals?

Dr. Sunil Rao:

Yeah. We did look at some subgroups. And you had to be a little bit cautious because again, the trial itself is relatively small. I mean, we didn't notice any significant patterns across these subgroups. And the overall interaction p-values were really non-significant. But I think what this does show is like a phase two trial that the drug works as in the way that it's intended. Overall, safety was as expected. And I think it really sets up data for a larger study.

Dr. Greg Hundley:

Well, listeners, what a fantastic presentation. And now, we're going to turn to our guest editor and editorialist, Dr. Gregory Lip from Liverpool. Greg, I know working for circulation, you have many papers come across your desk. What attracted you to this particular paper? And then maybe secondly, can you help us put the results of this study in the context of other studies that have been evaluating these factor XI therapies?

Dr. Gregory Lip:

Thanks, Greg. Well, I think this is an important paper, because it is a phase two trial with a novel, orally bioavailable inhibitor factor XI. And this is intriguing because factor XI efficiency in humans and experimentally in animals is associated with a reduced risk of thrombotic events like stroke or venous thromboembolism. But spontaneous bleeding is rare and also bleeding in response to trauma or surgery is much milder. Really it's the holy grail of trying to get an anticoagulant that reduces thrombosis but doesn't cause an excess of bleeding. Now, this was the quest with different anticoagulants.

And I think it was very exciting to see this particular paper in the patients who've had an acute coronary syndrome, because there was a lot of interest in the use of anticoagulants, particularly in combination with antiplatelet therapy from trials such as ATLAS and COMPASS, where there was certainly a reduction in adverse cardiovascular events. But a downside with those drugs and when using combination, was an excess of bleeding by the combination of the available anticoagulants now plus antiplatelets. The factor XIs agents offered the possibilities we might have combination therapy to reduce cardiovascular events but not causing an excess of bleeding.

Dr. Greg Hundley:

Well, listeners, what a wonderful discussion that we've had here. Let's circle back with both individuals. Sunil, we'll start with you. What do you see as the next study to really be performed in this sphere of research?

Dr. Sunil Rao:

I think that factor XI is a very attractive target in patients with acute coronary syndrome. Again, the rationale for why we did this phase two trial was to show that inhibition of activated factor XI should result in a low rate of ischemic events without a significant increase in bleeding. This phase two trial was really to try and decide which doses result in potent inhibition of factor XIa and potentially which doses should be carried forward into a larger study. What we found in the PACIFIC-AMI trial was that the doses of asundexian and the factor XIa inhibitor were very, very well tolerated with a low rate of adverse events. It resulted in a dose-dependent near complete inhibition of factor XIa activity without a significant increase in bleeding and a low rate of ischemic events. I think, again, it's a very attractive target in patients with ACS and this really provides support for a larger adequately powered clinical trial in patients with acute coronary syndrome that is really looking at clinical events such as MACE as well as bleeding.

Dr. Greg Hundley:

And Greg as an editorialist, what did you see with this paper? Maybe some unanswered questions that we'd like to pursue further?

Dr. Gregory Lip:

Well, I think this does raise a lot of questions in the sense that it'll be interesting because as a phase two trial, it's a relatively moderate sized trial. It's not like a phase three large outcome trial and phase two trials also testing different doses of the novel agent. We need to see the definitive phase three trial and to look at the magnitude of benefit versus potential for bleeding if in the large phase three trial and obviously, the net clinical benefit and importantly are some of the subgroups: ST elevation, myocardial infarction, undergoing primary PCI, for example, those with renal impairment. And I think particularly intriguing would be looking at the patients in this scenario who get the new antiplatelet drugs such as ticagrelor and prasugrel. And the reason I say that is what we have with warfarin or Coumadin and from the current DOACs or NOACs, depending on the risk side upon. We refer to them, that's the direct oral anticoagulants or non-vitamin K antagonist or anticoagulants.

Well, if you give a more potent antiplatelet like prasugrel or ticagrelor, the risk of bleeding not surprisingly is higher. Hence, the guidelines recommend that if you use an anticoagulant or a DOAC, you use it with a P2Y 12 inhibitor clopidogrel as opposed to the more potent ones. If this new class of drugs, the factor XI inhibitors can work well in combination with one of the more potent antiplatelets without causing an excessive bleeding, again, this is going to be a substantial advance.

Well, with these new class of anticoagulants, will be really interesting to see the phase three trials when applied to other chronic conditions. For example, stroke prevention and atrial fibrillation. And the other category of patients would be those who've had an embolic stroke of uncertain source or ESUS or in old terminology cryptogenic stroke. With the ESUS group of patients, they're currently treated with aspirin because the trials which tried a NOAC or DOAC, they were not showing a positive result. They'll be interesting again with the factor XI inhibitors, whether we are going to see this benefit with the reduction in recurrence stroke with no excessive bleeding.

Dr. Greg Hundley:

Very nice. Well, listeners, we want to thank Dr. Sunil Rao from NYU in New York City and Dr. Gregory Lip from the University of Liverpool for bringing us this study highlighting that in patients with recent acute myocardial infarction, three doses of asundexian when added to aspirin plus a P2Y 12 inhibitor resulted in dose-dependent near complete inhibition of factor XIa activity without a significant increase in bleeding and a low rate of ischemic events. And certainly, the data from this study support the investigation of asundexian at a dose of 50 milligrams daily in an adequately powered clinical trial of patients following acute myocardial infection.

Well, on behalf of Carolyn and myself, we want to wish you a great week and we will catch you next week On the Run. This program is copyright of the American Heart Association 2022. The opinions expressed by speakers in this podcast are their own and not necessarily those of the editors or of the American Heart Association. For more, please visit ahajournals.org.