Meta-analysis of the effects of endothelin receptor blockade on survival in experimental heart failure

Endothelin type A receptor blockade attenuates aorto-caval fistula-induced heart failure in rats with angiotensin II-dependent hypertension

OBJECTIVE

Evaluation of the effect of endothelin type A (ET A ) receptor blockade on the course of volume-overload heart failure in rats with angiotensin II-dependent hypertension.

METHODS

Ren-2 renin transgenic rats (TGR) were used as a model of hypertension. Heart failure was induced by creating an aorto-caval fistula (ACF). Selective ET A receptor blockade was achieved by atrasentan. For comparison, other rat groups received trandolapril, an angiotensin-converting enzyme inhibitor (ACEi). Animals first underwent ACF creation and 2 weeks later the treatment with atrasentan or trandolapril, alone or combined, was applied; the follow-up period was 20 weeks.

RESULTS

Eighteen days after creating ACF, untreated TGR began to die, and none was alive by day 79. Both atrasentan and trandolapril treatment improved the survival rate, ultimately to 56% (18 of 31 animals) and 69% (22 of 32 animals), respectively. Combined ACEi and ET A receptor blockade improved the final survival rate to 52% (17 of 33 animals). The effects of the three treatment regimens on the survival rate did not significantly differ. All three treatment regimens suppressed the development of cardiac hypertrophy and lung congestion, decreased left ventricle (LV) end-diastolic volume and LV end-diastolic pressure, and improved LV systolic contractility in ACF TGR as compared with their untreated counterparts.

CONCLUSION

The treatment with ET A receptor antagonist delays the onset of decompensation of volume-overload heart failure and improves the survival rate in hypertensive TGR with ACF-induced heart failure. However, the addition of ET A receptor blockade did not enhance the beneficial effects beyond those obtained with standard treatment with ACEi alone.

A Systematic Review Comparing Experimental Design of Animal and Human Methotrexate Efficacy Studies for Rheumatoid Arthritis: Lessons for the Translational Value of Animal Studies

Simple Summary

If we want to use animal studies to predict what will happen if we give a drug to humans, it makes sense to perform the animal studies as similarly to human studies as possible. For example, if animal tests of a drug only look at the effect of injecting the drug in young healthy animals, we cannot expect the results to be similar in human tests giving tablets to older patients who may have other diseases besides the one for which they receive the drug. We did an in-depth analysis of how 147 animal and 512 human studies of the drug methotrexate for rheumatoid arthritis were performed. Important differences were present, for example, animal studies used more males, while rheumatoid arthritis occurs more in females. We calculated the human-equivalent age of the animals, and they were on average younger than humans. Many studies did not fully report the way the experiments were performed. In spite of these differences, the drug methotrexate works well against rheumatoid arthritis in animal models and humans. Further (literature) research is still needed; we do not yet understand when we can reliably predict human effects from animal studies.

Abstract

Increased awareness and understanding of current practices in translational research is required for informed decision making in drug development. This paper describes a systematic review of methotrexate for rheumatoid arthritis, comparing trial design between 147 animal and 512 human studies. Animal studies generally included fewer subjects than human studies, and less frequently reported randomisation and blinding. In relation to life span, study duration was comparable for animals and humans, but included animals were younger than included humans. Animal studies often comprised males only (61%), human studies always included females (98% included both sexes). Power calculations were poorly reported in both samples. Analyses of human studies more frequently comprised Chi-square tests, those of animal studies more frequently reported analyses of variance. Administration route was more variable, and more frequently reported in animal than human studies. Erythrocyte sedimentation rate and c-reactive protein were analysed more frequently in human than in animal studies. To conclude, experimental designs for animal and human studies are not optimally aligned. However, methotrexate is effective in treating rheumatoid arthritis in animal models and humans. Further evaluation of the available evidence in other research fields is needed to increase the understanding of translational success before we can optimise translational strategies.

Can prospective systematic reviews of animal studies improve clinical translation?

Systematic reviews are powerful tools with the potential to generate high quality evidence. Their application to animal studies has been instrumental in exposing the poor quality of these studies, as well as a catalyst for improvements in study design, conduct and reporting. It has been suggested that prospective systematic reviews of animal studies (i.e. systematic reviews conducted prior to clinical trials) would allow scrutiny of the preclinical evidence, providing valuable information on safety and efficacy, and helping to determine whether clinical trials should proceed. However, while prospective systematic reviews allow valuable scrutiny of the preclinical animal data, they are not necessarily able to reliably predict the safety and efficacy of an intervention when trialled in humans. Consequently, they may not reliably safeguard humans participating in clinical trials and might potentially result in lost opportunities for beneficial clinical treatments. Furthermore, animal and human studies are often conducted concurrently, which not only makes prospective systematic reviews of animal studies impossible, but suggests that animal studies do not inform human studies in the manner presumed. We suggest that this points to a confused attitude regarding animal studies, whereby tradition demands that they precede human studies but practice indicates that their findings are often ignored. We argue that it is time to assess the relative contributions of animal and human research in order to better understand how clinical knowledge is actually produced.

Assessment of safety and efficacy of mesenchymal stromal cell therapy in preclinical models of acute myocardial infarction: a systematic review protocol

BACKGROUND

Despite advances in treatment, acute myocardial infarction (MI) is still associated with significant morbidity and mortality, especially in patients with extensive damage and scar formation. Based on some promising preclinical studies, there is interest in the use of mesenchymal stromal cells (MSCs) to promote cardiac repair after acute MI. However, there is a need for a systematic review of this evidence to summarize the efficacy and safety of MSCs in preclinical models of MI. This will better inform the translation of MSC therapy for acute MI and guide the design of a future clinical trial.

METHODS/DESIGN

A systematic literature search of MEDLINE, Embase, and BIOSIS Previews will be conducted. We will identify comparative preclinical studies (randomized and non-randomized) of myocardial infarction that include animals given MSC therapy versus a vehicle/placebo. The primary outcome will be left ventricular ejection fraction. Secondary and tertiary outcomes will include death, infarct size, measures of cardiac function, biochemical outcomes, and MSC retention and differentiation. Risk of bias will be assessed using the Cochrane Risk of Bias Tool. Subgroup analyses will be performed to measure how various sources of preclinical study heterogeneity affect the direction and magnitude of the primary outcome. We will meta-analyze data using inverse variance random effects modeling.

DISCUSSION

This systematic review of preclinical evidence will provide a summary of the efficacy and safety of MSCs in animal models of MI. The results will help determine whether sufficient evidence exists to conduct a clinical trial in humans and inform its design.

Clinical and Hemodynamic Effects of Endothelin Receptor Antagonists in Patients With Heart Failure

The clinical benefit of endothelin receptor antagonists (ERA) for the management of heart failure (HF) remains controversial. To examine this question, we performed a meta-analysis of randomized controlled trials (RCTs) to investigate the clinical and hemodynamic effects of ERA in HF patients.We searched the PubMed, Medline, Embase, and Cochrane Library from inception to March 20, 2016 to identify the pertinent studies. Risk ratio (RR) and weighted mean difference (WMD) were calculated using a fixed or random effect model.A total of 15 RCTs with 3,624 HF patients were included. Compared with control groups, ERA might not improve the mortality (RR 1.12, 95%CI 0.81 to 1.54, P = 0.51) or incidence of worsening HF or cardiovascular events (WHF/ CVE) (RR 1.06, 95%CI 0.94 to 1.19, P = 0.35) in HF patients. Subgroup analysis also suggested that neither nonselective nor selective ERAs had an impact on mortality and WHF/CVE. However, the hemodynamic variables of HF patients, including cardiac index (WMD 0.32, 95%CI 0.22 to 0.43, P < 0.01), pulmonary capillary wedge pressure (WMD -3.10, 95%CI -3.99 to -2.20, P < 0.01), mean pulmonary arterial pressure (WMD -4.42, 95%CI -5.50 to -3.33, P < 0.01), systemic vascular resistance (WMD -276.35, 95%CI -399.62 to -153.09, P < 0.01), and pulmonary vascular resistance (WMD -69.42, 95%CI -105.33 to -33.52, P < 0.01) were significantly improved by ERA.In conclusion, this meta-analysis suggests that ERA therapy could effectively improve cardiac output and pulmonary and systemic hemodynamics, but with less benefit to the clinical outcomes of HF patients.

Evaluating mesenchymal stem cell therapy for sepsis with preclinical meta-analyses prior to initiating a first-in-human trial

Evaluation of preclinical evidence prior to initiating early-phase clinical studies has typically been performed by selecting individual studies in a non-systematic process that may introduce bias. Thus, in preparation for a first-in-human trial of mesenchymal stromal cells (MSCs) for septic shock, we applied systematic review methodology to evaluate all published preclinical evidence. We identified 20 controlled comparison experiments (980 animals from 18 publications) of in vivo sepsis models. Meta-analysis demonstrated that MSC treatment of preclinical sepsis significantly reduced mortality over a range of experimental conditions (odds ratio 0.27, 95% confidence interval 0.18–0.40, latest timepoint reported for each study). Risk of bias was unclear as few studies described elements such as randomization and no studies included an appropriately calculated sample size. Moreover, the presence of publication bias resulted in a ~30% overestimate of effect and threats to validity limit the strength of our conclusions. This novel prospective application of systematic review methodology serves as a template to evaluate preclinical evidence prior to initiating first-in-human clinical studies.

DOI:http://dx.doi.org/10.7554/eLife.17850.001

Most attempts to transform exciting findings from laboratories into clinical treatments are unsuccessful. One reason for this may be the failure to consider all of the laboratory work that has been performed before deciding to test a treatment on patients for the first time. In particular, negative findings (that suggest that a potential new treatment is ineffective) may be overlooked.

Stem cells may help to treat life-threatening infections, but this has not been tested in human patients. However, the effectiveness of stem cell treatments has been tested in animals that act as models of human infection.

Before deciding to begin a clinical trial of stem cell therapy for life-threatening infections, Lalu et al. performed an exhaustive search to find all the studies in which stem cells were used to treat animal models of infection. Combining the results of all of these studies using particular analysis techniques revealed that stem cell therapy increased the survival of these animals overall. These positive effects were seen over a range of different experimental conditions (for example, when treating the animals with different doses of stem cells, or giving the doses at different times).

Lalu et al. also identified some limitations with most of the laboratory studies that had tested stem cell therapy for infections. Many of the studies used animal models that may not be the best representations of humans with severe infection. In addition, many of the scientists did not report that they had used methods (such as randomization) that would generate the most confidence in their results. Despite these limitations, there was a lot of consistency in the reported results.

Overall, the results support the decision to proceed to a clinical trial that tests the effectiveness of stem cells for treating human infections. More generally, Lalu et al.’s analysis demonstrates a way of considering all laboratory evidence before deciding to proceed to a first clinical trial in humans. This may help researchers to identify promising therapies to further develop, and also to identify potential failures before they are tested in patients.

DOI:http://dx.doi.org/10.7554/eLife.17850.002

Neurological recovery and antioxidant effects of curcumin for spinal cord injury in the rat: a network meta-analysis and systematic review

Spinal cord injury (SCI) is a devastating condition affecting young, healthy individuals worldwide. Existing agents have inadequate therapeutic efficacy, and some are associated with side effects. Our objective is to summarize and critically assess the neurological recovery and antioxidant effects of curcumin for treatment of SCI in rat models. PubMed, Embase, and Chinese databases were searched from their inception date to February 2014. Two reviewers independently selected animal studies that evaluated neurological recovery and antioxidant effects of curcumin, compared to placebo, in rats with SCI, extracted data, and assessed the methodological quality. A pair-wise analysis and a network meta-analysis were performed. Eight studies with adequate randomization were selected and included in the systematic review. Two studies had a higher methodological quality. Overall, curcumin appears to significantly improve neurological function, as assessed using the Basso, Beattie, Bresnahan (BBB) locomotor rating scale (four studies, n=132; pooled mean difference [MD]=3.09; 95% confidence interval [CI], 3.40-4.45; p=0.04), in a random-effects model and decrease malondialdehyde (MDA) using a fixed-effects model (four studies, n=56; pooled MD=-1.00; 95% CI=-1.59 to -0.42; p=0.00008). Effect size, assessed using the BBB scale, increased gradually with increasing curcumin dosage. The difference between low- and high-dose curcumin using the BBB scale was statistically significant. Neurological recovery and antioxidant effects of curcumin were observed in rats with SCI despite poor study methodological quality.

How to increase value and reduce waste when research priorities are set

The increase in annual global investment in biomedical research--reaching US$240 billion in 2010--has resulted in important health dividends for patients and the public. However, much research does not lead to worthwhile achievements, partly because some studies are done to improve understanding of basic mechanisms that might not have relevance for human health. Additionally, good research ideas often do not yield the anticipated results. As long as the way in which these ideas are prioritised for research is transparent and warranted, these disappointments should not be deemed wasteful; they are simply an inevitable feature of the way science works. However, some sources of waste cannot be justified. In this report, we discuss how avoidable waste can be considered when research priorities are set. We have four recommendations. First, ways to improve the yield from basic research should be investigated. Second, the transparency of processes by which funders prioritise important uncertainties should be increased, making clear how they take account of the needs of potential users of research. Third, investment in additional research should always be preceded by systematic assessment of existing evidence. Fourth, sources of information about research that is in progress should be strengthened and developed and used by researchers. Research funders have primary responsibility for reductions in waste resulting from decisions about what research to do.

Clinical trials with endothelin receptor antagonists: what went wrong and where can we improve?

In the early 1990s, within three years of cloning of endothelin receptors, orally active endothelin receptor antagonists (ERAs) were tested in humans and the first clinical trial of ERA therapy in humans was published in 1995. ERAs were subsequently tested in clinical trials involving heart failure, pulmonary arterial hypertension, resistant arterial hypertension, stroke/subarachnoid hemorrhage and various forms of cancer. The results of most of these trials - except those for pulmonary arterial hypertension and scleroderma-related digital ulcers - were either negative or neutral. Problems with study design, patient selection, drug toxicity, and drug dosing have been used to explain or excuse failures. Currently, a number of pharmaceutical companies who had developed ERAs as drug candidates have discontinued clinical trials or further drug development. Given the problems with using ERAs in clinical medicine, at the Twelfth International Conference on Endothelin in Cambridge, UK, a panel discussion was held by clinicians actively involved in clinical development of ERA therapy in renal disease, systemic and pulmonary arterial hypertension, heart failure, and cancer. This article provides summaries from the panel discussion as well as personal perspectives of the panelists on how to proceed with further clinical testing of ERAs and guidance for researchers and decision makers in clinical drug development on where future research efforts might best be focused.

Can animal models of disease reliably inform human studies?

H. Bart van der Worp and colleagues discuss the controversies and possibilities of translating the results of animal experiments into human clinical trials.

Animal studies in spinal cord injury: a systematic review of methylprednisolone

The objective of this study was to examine whether animal studies can reliably be used to determine the usefulness of methylprednisolone (MP) and other treatments for acute spinal cord injury (SCI) in humans. This was achieved by performing a systematic review of animal studies on the effects of MP administration on the functional outcome of acute SCI. Data were extracted from the published articles relating to: outcome; MP dosing regimen; species/strain; number of animals; methodological quality; type of injury induction; use of anaesthesia; functional scale used; and duration of follow-up. Subgroup analyses were performed, based on species or strain, injury method, MP dosing regimen, functional outcome measured, and methodological quality. Sixty-two studies were included, which involved a wide variety of animal species and strains. Overall, beneficial effects of MP administration were obtained in 34% of the studies, no effects in 58%, and mixed results in 8%. The results were inconsistent both among and within species, even when attempts were made to detect any patterns in the results through subgroup analyses. The results of this study demonstrate the barriers to the accurate prediction from animal studies of the effectiveness of MP in the treatment of acute SCI in humans. This underscores the need for the development and implementation of validated testing methods.

Ethics of cancer gene transfer clinical research

Cancer gene transfer is a relatively novel intervention strategy. In part because of this novelty, trials often present greater uncertainties than those investigating more conventional approaches. In the following review, I examine how this greater uncertainty might affect how clinical studies are designed, when they are initiated, their degree of risk, and whether such risk can be justified in terms of therapeutic benefit. The review also discusses two other ethical issues presented by gene transfer clinical research: fairness in subject selection and communications with the public. I conclude with a series of recommendations directed toward researchers, policymakers, and ethics committee members.

Systematic Reviews of Animal Experiments Demonstrate Poor Human Clinical and Toxicological Utility

The assumption that animal models are reasonably predictive of human outcomes provides the basis for their widespread use in toxicity testing and in biomedical research aimed at developing cures for human diseases. To investigate the validity of this assumption, the comprehensive Scopus biomedical bibliographic databases were searched for published systematic reviews of the human clinical or toxicological utility of animal experiments. In 20 reviews in which clinical utility was examined, the authors concluded that animal models were either significantly useful in contributing to the development of clinical interventions, or were substantially consistent with clinical outcomes, in only two cases, one of which was contentious. These included reviews of the clinical utility of experiments expected by ethics committees to lead to medical advances, of highly-cited experiments published in major journals, and of chimpanzee experiments — those involving the species considered most likely to be predictive of human outcomes. Seven additional reviews failed to clearly demonstrate utility in predicting human toxicological outcomes, such as carcinogenicity and teratogenicity. Consequently, animal data may not generally be assumed to be substantially useful for these purposes. Possible causes include interspecies differences, the distortion of outcomes arising from experimental environments and protocols, and the poor methodological quality of many animal experiments, which was evident in at least 11 reviews. No reviews existed in which the majority of animal experiments were of good methodological quality. Whilst the effects of some of these problems might be minimised with concerted effort (given their widespread prevalence), the limitations resulting from interspecies differences are likely to be technically and theoretically impossible to overcome. Non-animal models are generally required to pass formal scientific validation prior to their regulatory acceptance. In contrast, animal models are simply assumed to be predictive of human outcomes. These results demonstrate the invalidity of such assumptions. The consistent application of formal validation studies to all test models is clearly warranted, regardless of their animal, non-animal, historical, contemporary or possible future status. Likely benefits would include, the greater selection of models truly predictive of human outcomes, increased safety of people exposed to chemicals that have passed toxicity tests, increased efficiency during the development of human pharmaceuticals and other therapeutic interventions, and decreased wastage of animal, personnel and financial resources. The poor human clinical and toxicological utility of most animal models for which data exists, in conjunction with their generally substantial animal welfare and economic costs, justify a ban on animal models lacking scientific data clearly establishing their human predictivity or utility.

Translating animal research into clinical benefit

Poor methodological standards in animal studies mean that positive results rarely translate to the clinical domain

Clinical trials of endothelin antagonists in heart failure: publication is good for the public health

The failure of endothelin antagonists to show benefit in heart failure cannot be understood until all the clinical trials are fully published.

Bench to bedside: the quest for quality in experimental stroke research

Over the past decades, great progress has been made in clinical as well as experimental stroke research. Disappointingly, however, hundreds of clinical trials testing neuroprotective agents have failed despite efficacy in experimental models. Recently, several systematic reviews have exposed a number of important deficits in the quality of preclinical stroke research. Many of the issues raised in these reviews are not specific to experimental stroke research, but apply to studies of animal models of disease in general. It is the aim of this article to review some quality-related sources of bias with a particular focus on experimental stroke research. Weaknesses discussed include, among others, low statistical power and hence reproducibility, defects in statistical analysis, lack of blinding and randomization, lack of quality-control mechanisms, deficiencies in reporting, and negative publication bias. Although quantitative evidence for quality problems at present is restricted to preclinical stroke research, to spur discussion and in the hope that they will be exposed to meta-analysis in the near future, I have also included some quality-related sources of bias, which have not been systematically studied. Importantly, these may be also relevant to mechanism-driven basic stroke research. I propose that by a number of rather simple measures reproducibility of experimental results, as well as the step from bench to bedside in stroke research may be made more successful. However, the ultimate proof for this has to await successful phase III stroke trials, which were built on basic research conforming to the criteria as put forward in this article.

Where is the evidence that animal research benefits humans?

Much animal research into potential treatments for humans is wasted because it is poorly conducted and not evaluated through systematic reviews