The ixCELL-DCM Trial: Rationale and Design

Trials and tribulations of cell therapy for heart failure: an update on ongoing trials

Heart failure (HF) remains a leading cause of mortality, responsible for 13% of all deaths worldwide. The prognosis for patients with HF is poor, with only a 50% survival rate within 5 years. A major challenge of ischaemia-driven HF is the loss of cardiomyocytes, compounded by the minimal regenerative capacity of the adult heart. To date, replacement of irreversibly damaged heart muscle can only be achieved by complete heart transplantation. In the past 20 years, cell therapy has emerged and evolved as a promising avenue for cardiac repair and regeneration. During this time, cell therapy for HF has encountered substantial barriers in both preclinical studies and clinical trials but the field continues to progress and evolve from lessons learned from such research. In this Review, we provide an overview of ongoing trials of cell-based and cell product-based therapies for the treatment of HF. Findings from these trials will facilitate the clinical translation of cardiac regenerative and reparative therapies not only by evaluating the safety and efficacy of specific cell-based therapeutics but also by establishing the feasibility of novel or underexplored treatment protocols such as repeated intravenous dosing, personalized patient selection based on pharmacogenomics, systemic versus intramural cell delivery, and epicardial engraftment of engineered tissue products.

Stem Cell-based Therapies in Cardiovascular Diseases: From Pathophysiology to Clinical Outcomes

Over 20 years of intensified research in the field of stem cells brought about unprecedented possibilities in treating heart diseases. The investigators were initially fascinated by the idea of regenerating the lost myocardium and replacing it with new functional cardiomyocytes, but this was extremely challenging. However, the multifactorial effects of stem cell-based therapies beyond mere cardiomyocyte generation, caused by paracrine signaling, would open up new possibilities in treating cardiovascular diseases. To date, there is a strong body of evidence that the anti-inflammatory, anti-apoptotic, and immunomodulatory effects of stem cell therapy may alleviate atherosclerosis progression. In the present review, our objective is to provide a brief overview of the stem cell-based therapeutic options. We aim to delineate the pathophysiological mechanisms of their beneficial effects in cardiovascular diseases especially in coronary artery disease and to highlight some conclusions from important clinical studies in the field of regenerative medicine in cardiovascular diseases and how we could further move onwards.

On recurrent-event win ratio

The win ratio approach proposed by Pocock et al. (2012) has become a popular tool for analyzing composite endpoints of death and non-fatal events like hospitalization. Its standard version, however, draws on the non-fatal event only through the first occurrence. For statistical efficiency and clinical interpretability, we construct and compare different win ratio variants that make fuller use of recurrent events. We pay special attention to a variant called last-event-assisted win ratio, which compares two patients on the cumulative frequency of the non-fatal event, with ties broken by the time of its latest episode. It is shown that last-event-assisted win ratio uses more data than the standard win ratio does but reduces to the latter when the non-fatal event occurs at most once. We further prove that last-event-assisted win ratio rejects the null hypothesis with large probability if the treatment stochastically delays all events. Simulations under realistic settings show that the last-event-assisted win ratio test consistently enjoys higher power than the standard win ratio and other competitors. Analysis of a real cardiovascular trial provides further evidence for the practical advantages of the last-event-assisted win ratio. Finally, we discuss future work to develop meaningful effect size estimands based on the extended rules of comparison. The R-code for the proposed methods is included in the package WR openly available on the Comprehensive R Archive Network.

OUP accepted manuscript

Numerous components of the immune system, including inflammatory mediators, immune cells and cytokines, have a profound modulatory effect on the homeostatic regulation and regenerative activity of endogenous stem cells and progenitor cells. Thus, understanding how the immune system interacts with stem/progenitor cells could build the foundation to design novel and more effective regenerative therapies. Indeed, utilizing and controlling immune system components may be one of the most effective approaches to promote tissue regeneration. In this review, we first summarize the effects of various immune cell types on endogenous stem/progenitor cells, focusing on the tissue healing context. Then, we present interesting regenerative strategies that control or mimic the effect of immune components on stem/progenitor cells, in order to enhance the regenerative capacity of endogenous and transplanted stem cells. We highlight the potential clinical translation of such approaches for multiple tissues and organ systems, as these novel regenerative strategies could considerably improve or eventually substitute stem cell-based therapies. Overall, harnessing the power of the cross-talk between the immune system and stem/progenitor cells holds great potential for the development of novel and effective regenerative therapies.

Win odds: An adaptation of the win ratio to include ties

The win ratio, a recently proposed measure for comparing the benefit of two treatment groups, allows ties in the data but ignores ties in the inference. In this article, we highlight some difficulties that this can lead to, and we propose to focus on the win odds instead, a modification of the win ratio which takes ties into account. We construct hypothesis tests and confidence intervals for the win odds, and we investigate their properties through simulations and in a case study. We conclude that the win odds should be preferred over the win ratio.

Stem cell therapy in heart failure: Where do we stand today?

Heart failure is a global epidemic that drastically cuts short longevity and compromises quality of life. Approximately 6 million Americans ≥20 years of age carry a diagnosis of heart failure. Worldwide, about 40 million adults are affected. The treatment of HF depends on the etiology. If left untreated it rapidly progresses and compromises quality of life. One of the newer technologies still in its infancy is stem cell therapy for heart failure. This review attempts to highlight the clinical studies done in ischemic cardiomyopathy, dilated cardiomyopathy and restrictive cardiomyopathy. A combined approach of simultaneous revascularization and stem cell therapy appears to produce maximum benefit in ischemic cardiomyopathy. Treatment of dilated cardiomyopathy with stem cells also holds promise but needs more definition with regards to timing, route of cell delivery and type of cell used to achieve reproducible results. The variability noted in response to stem cell therapy in patients could also be secondary to their co-morbidities. Abnormalities of glucose metabolism and diabetes in particular impair stem cell and angiogenic cell mobilization. This opens up a whole new area of investigation into exploring the biochemical microenvironment which could influence the efficacy of stem cell therapy. This article is part of a Special Issue entitled: Stem Cells and Their Applications to Human Diseases edited by Hemachandra Reddy.

The Role of the Stem Cells Therapy in the Peripheral Artery Disease

Vascular complications of diabetes mellitus are an important issue for all clinicians involved in the management of this complex pathology. Although many therapeutic advances have been reached, peripheral arterial disease is still an unsolved problem that each year compromises the quality of life and life span of affected patients. Oftentimes, patients, after ineffective attempts of revascularization, undergo greater amputations. At the moment, there is no effective and definitive treatment available. In this scenario, the therapeutic use of stem cells could be an interesting option. The aim of the present review is to gather all the best available evidence in this regard and to define a new role of the stem cells therapy in this field, from biomarker to possible therapeutic target.

Myths, reality and future of mesenchymal stem cell therapy

Mesenchymal stem cell (MSC) therapy represents an alternative approach for tissue regeneration and inflammation control. In spite of a huge amount of preclinical data that has been accumulated on the therapeutic properties of MSCs, there are many conflicting results, possibly due to differences in the properties of MSCs obtained from different sources or underestimated mechanisms of MSC in vivo behavior. This review consolidates the in vivo effects of MSC therapy, discusses the fate of MSCs after intravascular and local delivery and proposes possible trends in MSC therapy.

Mesenchymal Stem Cell-Based Therapy for Cardiovascular Disease: Progress and Challenges

Administration of mesenchymal stem cells (MSCs) to diseased hearts improves cardiac function and reduces scar size. These effects occur via the stimulation of endogenous repair mechanisms, including regulation of immune responses, tissue perfusion, inhibition of fibrosis, and proliferation of resident cardiac cells, although rare events of transdifferentiation into cardiomyocytes and vascular components are also described in animal models. While these improvements demonstrate the potential of stem cell therapy, the goal of full cardiac recovery has yet to be realized in either preclinical or clinical studies. To reach this goal, novel cell-based therapeutic approaches are needed. Ongoing studies include cell combinations, incorporation of MSCs into biomaterials, or pre-conditioning or genetic manipulation of MSCs to boost their release of paracrine factors, such as exosomes, growth factors, microRNAs, etc. All of these approaches can augment therapeutic efficacy. Further study of the optimal route of administration, the correct dose, the best cell population(s), and timing for treatment are parameters that still need to be addressed in order to achieve the goal of complete cardiac regeneration. Despite significant progress, many challenges remain.

Ixmyelocel-T for patients with ischaemic heart failure: a prospective randomised double-blind trial

BACKGROUND

Ixmyelocel-T is an expanded, multicellular therapy produced from a patient's own bone marrow by selectively expanding two key types of bone marrow mononuclear cells: CD90+ mesenchymal stem cells and CD45+ CD14+ auto-fluorescent+ activated macrophages. Early phase clinical trials suggest that intramyocardial delivery of ixmyelocel-T might improve clinical, functional, symptomatic, and quality-of-life outcomes in patients with heart failure due to ischaemic dilated cardiomyopathy. We aimed to assess the safety and efficacy of catheter-based transendocardial injection of ixmyelocel-T cell therapy in patients with heart failure and reduced ejection fractions.

METHODS

In this randomised, double-blind, placebo-controlled phase 2B trial (ixCELL-DCM), patients from 31 sites in North America with New York Heart Association class III or IV symptomatic heart failure due to ischaemic dilated cardiomyopathy, who had left ventricular ejection fraction 35% or less, an automatic implantable cardioverter defibrillator, and who were ineligible for revascularisation procedures were randomly assigned (1:1) to receive ixmyelocel-T or placebo at the time of bone marrow aspiration and followed for 12 months. Randomisation was done through an interactive (voice/web) response system. The pharmacist, treating physician, and coordinator at each site were unblinded, but the the follow-up team was completely blinded. The primary endpoint was a composite of all-cause death, cardiovascular admission to hospital, and unplanned clinic visits to treat acute decompensated heart failure based on the blinded adjudication of an independent clinical endpoint committee. Primary efficacy endpoint analyses and safety analyses were done by modified intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01670981.

FINDINGS

Between April 2, 2013, and Jan 28, 2015, 126 participants were randomly assigned to receive either ixmyelocel-T (n=66) or placebo (n=60). 114 (90%) patients comprised the modified intention-to-treat population and 109 (87%) patients were included in the per-protocol primary efficacy analysis (58 in the ixmyelocel-T group and 51 in the placebo group). The primary efficacy endpoint was observed in 47 patients: 50 events in 25 (49%) of 51 patients in the placebo group and 38 events in 22 (38%) of 58 patients in the ixmyelocel-T group, which represents a 37% reduction in cardiac events compared with placebo (risk ratio 0·63 [95% CI 0·42-0·97]; p=0·0344). 41 (75%) of 51 participants in the placebo group had serious adverse events versus 31 (53%) of 58 in the ixmyelocel-T group (p=0·0197).

INTERPRETATION

To the best of our knowledge, ixCELL-DCM is the largest cell therapy study done in patients with heart failure so far. The transendocardial delivery of ixmyelocel-T in patients with heart failure and reduced ejection fraction due to ischaemic dilated cardiomyopathy resulted in a significant reduction in adjudicated clinical cardiac events compared with placebo leading to improved patient outcomes.

FUNDING

Vericel Corporation.