Lessons learned from recent cardiovascular clinical trials: Part II

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Protein kinases in cardiovascular diseases

ABSTRACT

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Therefore, exploring the mechanism of CVDs and critical regulatory factors is of great significance for promoting heart repair, reversing cardiac remodeling, and reducing adverse cardiovascular events. Recently, significant progress has been made in understanding the function of protein kinases and their interactions with other regulatory proteins in myocardial biology. Protein kinases are positioned as critical regulators at the intersection of multiple signals and coordinate nearly every aspect of myocardial responses, regulating contractility, metabolism, transcription, and cellular death. Equally, reconstructing the disrupted protein kinases regulatory network will help reverse pathological progress and stimulate cardiac repair. This review summarizes recent researches concerning the function of protein kinases in CVDs, discusses their promising clinical applications, and explores potential targets for future treatments.

A third trial oversight committee: Functions, benefits and issues

Background/aims:

Clinical trial oversight is central to the safety of participants and production of robust data. The United Kingdom Medical Research Council originally set out an oversight structure comprising three committees in 1998. The first committee, led by the trial team, is hands-on with trial conduct/operations (‘Trial Management Group’) and essential. The second committee (Data Monitoring Committee), usually completely independent of the trial, reviews accumulating trial evidence and is used by most later phase trials. The Independent Data Monitoring Committee makes recommendations to the third oversight committee. The third committee, (‘Trial Steering Committee’), facilitates in-depth interactions of independent and non-independent trial members and gives broader oversight (blinded to comparative analysis). We investigated the roles and functioning of the third oversight committee with multiple research methods. We reflect upon these findings to standardise the committee’s remit and operation and to potentially increase its usage.

Methods:

We utilised findings from our recent published suite of research on the third oversight committee to inform guideline revision. In brief, we conducted a survey of 38 United Kingdom–registered Clinical Trials Units, reviewed a cohort of 264 published trials, observed 8 third oversight committee meetings and interviewed 52 trialists. We convened an expert panel to discuss third oversight committees. Subsequently, we interviewed nine patient/lay third committee members and eight committee Chairs.

Results:

In the survey, most Clinical Trials Units required a third committee for all their trials (27/38, 71%) with independent members (ranging from 1 to 6). In the survey and interviews, the independence of the third committee was valued to make unbiased consideration of Independent Data Monitoring Committee recommendations and to advise on trial progress, protocol changes and recruitment issues in conjunction with the trial leadership. The third committee also advised funders and sponsors about trial continuation and represented patients and the public by including lay members. Of the cohort of 264 published trials, 144 reported a ‘steering’ committee (55%), but the independence of these members was not described so these may have been internal Trial Management Groups. Around two thirds of papers (60%) reported having an Independent Data Monitoring Committee and 26.9% neither a steering nor an Independent Data Monitoring Committee. However, before revising the third committee charter (Terms of Reference), greater standardisation is needed around defining member independence, composition, primacy of decision-making, interactions with other committees and the lifespan.

Conclusion:

A third oversight committee has benefits for trial oversight and conduct, and a revised charter will facilitate greater standardisation and wider adoption.

Exploring the ethical and regulatory issues in pragmatic clinical trials

The need for high-quality evidence to support decision making about health and health care by patients, physicians, care providers, and policy-makers is well documented. However, serious shortcomings in evidence persist. Pragmatic clinical trials that use novel techniques including emerging information and communication technologies to explore important research questions rapidly and at a fraction of the cost incurred by more "traditional" research methods promise to help close this gap. Nevertheless, while pragmatic clinical trials can bridge clinical practice and research, they may also raise difficult ethical and regulatory challenges. In this article, the authors briefly survey the current state of evidence that is available to inform clinical care and other health-related decisions and discuss the potential for pragmatic clinical trials to improve this state of affairs. They then propose a new working definition for pragmatic research that centers upon fitness for informing decisions about health and health care. Finally, they introduce a project, jointly undertaken by the National Institutes of Health Health Care Systems Research Collaboratory and the National Patient-Centered Clinical Research Network (PCORnet), which addresses 11 key aspects of current systems for regulatory and ethical oversight of clinical research that pose challenges to conducting pragmatic clinical trials. In the series of articles commissioned on this topic published in this issue of Clinical Trials, each of these aspects is addressed in a dedicated article, with a special focus on the interplay between ethical and regulatory considerations and pragmatic clinical research aimed at informing "real-world" choices about health and health care.

Prevalence, characteristics, and predictors of early termination of cardiovascular clinical trials due to low recruitment: insights from the ClinicalTrials.gov registry

BACKGROUND

Early termination of clinical trials due to low recruitment represents an understudied challenge for clinical research. We aimed to describe characteristics of cardiovascular trials terminated because of low recruitment and identify the major predictors of such early termination.

METHODS

We reviewed all cardiovascular clinical trials (7,042 studies) registered in ClinicalTrials.gov from February 29, 2000, to January 17, 2013, and assessed information about trials that were completed and those that were terminated early. Logistic regression models were developed to identify independent predictors of early termination due to low recruitment.

RESULTS

Our search strategy identified 6,279 cardiovascular clinical trials, of which 684 (10.9%) were terminated prematurely. Of these halted trials, the main reason for termination was lower than expected recruitment (278 trials; 53.6%). When comparing trials that terminated early because of low recruitment with those that were completed, we found that studies funded by the National Institutes of Health or other US federal agencies (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.14-0.89), studies of behavior/diet intervention (OR 0.35, 95% CI 0.19-0.65), and single-arm design studies (OR 0.57, 95% CI 0.42-0.78) were associated with a lower risk of early termination. University/hospital-funded (OR 1.52, 95% CI 1.10-2.10) and mixed-source-funded studies (OR 2.14, 95% CI 1.52-3.01) were associated with a higher likelihood of early termination due to lower than expected recruitment rates.

CONCLUSIONS

Low recruitment represents the main cause of early termination of cardiovascular clinical trials. Funding source, type of intervention, and study design are factors associated with early termination due to low recruitment and might be good targets for improving enrollment into cardiovascular clinical trials.

Nutrition intervention to decrease symptoms in patients with advanced heart failure

For a majority of patients with advanced heart failure, there is a need for complementary, non-pharmacologic interventions that could be easily implemented by health care providers to provide palliative care. Three major pathologic pathways underlying heart failure symptoms have been identified: fluid overload, inflammation, and oxidative stress. Prior research has demonstrated that three nutrients-sodium, omega-3 fatty acids, and lycopene-can alter these pathologic pathways. Therefore, the purposes of this study are to test the effects of a 6-month nutrition intervention of dietary sodium reduction combined with supplementation of lycopene and omega-3 fatty acids on heart failure symptoms, health-related quality of life, and time to heart failure rehospitalization or all-cause death. The aims of this double blind-placebo controlled study are (1) to determine the effects of a 6-month nutrition intervention on symptom burden (edema, shortness of air, and fatigue) and health-related quality of life at 3 and 6 months, and time to heart failure rehospitalization or all-cause death over 12 months from baseline; (2) compare dietary sodium intake, inflammation, and markers of oxidative stress between the nutrition intervention group and a placebo group at 3 and 6 months; and (3) compare body weight, serum lycopene, and erythrocyte omega-3 index between the nutrition intervention group and a placebo group at 3 and 6 months. A total of 175 patients with advanced heart failure will be randomized to either the nutrition intervention or placebo group.

Protein kinase C, an elusive therapeutic target?

Protein kinase C (PKC) has been a tantalizing target for drug discovery ever since it was first identified as the receptor for the tumour promoter phorbol ester in 1982. Although initial therapeutic efforts focused on cancer, additional indications--including diabetic complications, heart failure, myocardial infarction, pain and bipolar disorder--were targeted as researchers developed a better understanding of the roles of eight conventional and novel PKC isozymes in health and disease. Unfortunately, both academic and pharmaceutical efforts have yet to result in the approval of a single new drug that specifically targets PKC. Why does PKC remain an elusive drug target? This Review provides a short account of some of the efforts, challenges and opportunities in developing PKC modulators to address unmet clinical needs.

The child and adolescent psychiatry trials network (CAPTN): infrastructure development and lessons learned

BACKGROUND

In 2003, the National Institute of Mental Health funded the Child and Adolescent Psychiatry Trials Network (CAPTN) under the Advanced Center for Services and Intervention Research (ACSIR) mechanism. At the time, CAPTN was believed to be both a highly innovative undertaking and a highly speculative one. One reviewer even suggested that CAPTN was "unlikely to succeed, but would be a valuable learning experience for the field."

OBJECTIVE

To describe valuable lessons learned in building a clinical research network in pediatric psychiatry, including innovations intended to decrease barriers to research participation.

METHODS

The CAPTN Team has completed construction of the CAPTN network infrastructure, conducted a large, multi-center psychometric study of a novel adverse event reporting tool, and initiated a large antidepressant safety registry and linked pharmacogenomic study focused on severe adverse events. Specific challenges overcome included establishing structures for network organization and governance; recruiting over 150 active CAPTN participants and 15 child psychiatry training programs; developing and implementing procedures for site contracts, regulatory compliance, indemnification and malpractice coverage, human subjects protection training and IRB approval; and constructing an innovative electronic casa report form (eCRF) running on a web-based electronic data capture system; and, finally, establishing procedures for audit trail oversight requirements put forward by, among others, the Food and Drug Administration (FDA).

CONCLUSION

Given stable funding for network construction and maintenance, our experience demonstrates that judicious use of web-based technologies for profiling investigators, investigator training, and capturing clinical trials data, when coupled to innovative approaches to network governance, data management and site management, can reduce the costs and burden and improve the feasibility of incorporating clinical research into routine clinical practice. Having successfully achieved its initial aim of constructing a network infrastructure, CAPTN is now a capable platform for large safety registries, pharmacogenetic studies, and randomized practical clinical trials in pediatric psychiatry.

Prevention of diabetes and cardiovascular disease in patients with impaired glucose tolerance: rationale and design of the Nateglinide And Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) Trial

Patients with impaired glucose tolerance (IGT) have increased risk for developing type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Lifestyle modification and medication can prevent or delay progression to diabetes (PD), but whether such interventions also reduce the risk of CVD has not been rigorously tested. The Nateglinide And Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial is a multinational, randomized, double-blind, 2 x 2 factorial trial in subjects with IGT (on a screening oral glucose tolerance test [OGTT]) aged > or = 50 years with known CVD or aged > or = 55 years with > or = 1 CVD risk factor. Enrollment began in January 2002 and was completed January 2004, with 9,518 patients randomized to receive 1 of 4 possible treatment combinations as follows: nateglinide with valsartan, nateglinide with valsartan-placebo, nateglinide-placebo with valsartan, or nateglinide-placebo with valsartan-placebo. All subjects are participating in a clinic-based and telephone-based lifestyle intervention aimed at reducing weight and dietary fat and increasing physical activity. The 3 coprimary end points are new onset of T2DM, a "core" composite of major cardiovascular events (death, myocardial infarction, stroke, or hospitalization for heart failure), and an "extended" composite including the components of the core composite plus coronary revascularization and hospitalization for unstable angina. The study was designed to evaluate whether reducing postprandial hyperglycemia, blockade of the renin-angiotensin-aldosterone system, or both interventions reduce the risk of T2DM or cardiovascular events in patients with IGT.

Role of lifestyle and oral anti-diabetic agents to prevent type 2 diabetes mellitus and cardiovascular disease

Patients with type 2 diabetes mellitus (DM) and those with impaired glucose tolerance are at increased risk for the development of cardiovascular disease. With an increasing global incidence and prevalence of type 2 DM, and with the 2003 lowering of the glucose threshold required for the diagnosis of impaired glucose tolerance to 100 mg/dl (5.6 mmol/L), the concept of DM prevention, and presumed reduction of cardiovascular risk, is attractive. However, there is little evidence to guide the choice of DM prevention strategy and no certainty that DM prevention will result in reduced cardiovascular events or an overall favorable balance of benefit to risk. In conclusion, this review examines previous reports on DM prevention, with special attention to evidence for cardiovascular event reduction in association with specific interventions to prevent DM.

Defining the balance of risk and benefit in the era of genomics and proteomics

The ability to measure the function of genes and proteins has spawned the construct of personalized medicine, in which patients' own risks and preferences are used to choose diagnostic and therapeutic strategies. The complexity of clinical data required to guide personalized medicine calls for improvements in our system of clinical research, including (1) overhauling it to produce networks that can do adequate-size pragmatic trials; (2) synchronization of regulatory and payment systems to encourage adequate studies; and (3) an investment in education of providers and patients to improve the understanding of the probabilistic predictions forming the basis of personalized medicine.

Prior convictions

Large, randomized clinical trials ("megatrials") are key drivers of modern cardiovascular practice, since they are cited frequently as the authoritative foundation for evidence-based management policies. Nevertheless, fundamental limitations in the conventional approach to statistical hypothesis testing undermine the scientific basis of the conclusions drawn from these trials. This review describes the conventional approach to statistical inference, highlights its limitations, and proposes an alternative approach based on Bayes' theorem. Despite its inherent subjectivity, the Bayesian approach possesses a number of practical advantages over the conventional approach: 1). it allows the explicit integration of previous knowledge with new empirical data; 2). it avoids the inevitable misinterpretations of p values derived from megatrial populations; and 3). it replaces the misleading p value with a summary statistic having a natural, clinically relevant interpretation-the probability that the study hypothesis is true given the observations. This posterior probability thereby quantifies the likelihood of various magnitudes of therapeutic benefit rather than the single null magnitude to which the p value refers, and it lends itself to graphical sensitivity analyses with respect to its underlying assumptions. Accordingly, the Bayesian approach should be employed more widely in the design, analysis, and interpretation of clinical megatrials.

The challenges of conducting clinical endpoint studies

In order to evaluate the effects of a particular treatment strategy on mortality and major morbidity within a disease entity, large, multinational, relatively long-term clinical endpoint studies are often conducted. The primary challenge of conducting these studies is to maintain consistency in the interpretation of the clinical endpoints across different geographic areas and over the long time course of the study. The success of a clinical endpoint study depends on understanding the challenges and incorporating the special requirements of these studies into the protocol design and operational procedures throughout the study.

Integrating quality into the cycle of therapeutic development

The quality of healthcare, particularly as reflected in current practice versus the available evidence, has become a major focus of national health policy discussions. Key components needed to provide quality care include: 1) development of quality indicators and performance measures from specific practice guidelines, 2) better ways to disseminate such guidelines and measures, and 3) development of support tools to promote standardized practice. Although rational decision-making and development of practice guidelines have relied upon results of randomized trials and outcomes studies, not all questions can be answered by randomized trials, and many treatment decisions necessarily reflect physiology, intuition, and experience when treating individuals. Debate about the role of "evidence-based medicine" also has raised questions about the value of applying trial results in practice, and some skepticism has arisen about whether advocated measures of clinical effectiveness, the basic definition of quality, truly reflect a worthwhile approach to improving medical practice. We provide a perspective on this issue by describing a model that integrates quantitative measurements of quality and performance into the development cycle of existing and future therapeutics. Such a model would serve as a basic approach to cardiovascular medicine that is necessary, but not sufficient, to those wishing to provide the best care for their patients.