Cytel Blog

In this blog we share a case study of work our strategic consulting team conducted supporting accurate event prediction for a cardiovascular outcomes research trial using the Major Adverse Cardiac Events ( MACE) composite endpoint. 

 The Global Cardiovascular Clinical Trialists Forum is a key event bringing together leading experts from across the spectrum of opinion leaders, clinical trialists, investigators, regulators, statisticians and practitioners to address the most pressing questions in cardiovascular clinical development today.  At the December conference, eminent biostatisticians Cyrus Mehta and Stuart Pocock led a packed workshop tackling the advantages and limitations of adaptive designs within this space.

In honor of World Obesity Day (celebrated on Oct. 11 2015) here is an American Heart Association Statistical Primer on Cardiovascular Research. Cardiovascular outcome trials (sometimes called CVOTs) are clinical trials that are critical for determining the safety of new anti-obesity and diabetes drugs. Early CVOTs like TECOS and SAVOR-TIMI enrolled over 14,000 and 16,000 patients respectively.

Cyrus Mehta, president and co-founder of Cytel, has been on the forefront of developing novel designs to shorten the length of these trials while maintaining high statistical rigor. In this primer he provides an overview of fixed sample, GS and adaptive designs for cardiovascular trials. Other topics include: adaptive sample size re-estimation, and SSR with enrichment for high and low risk subpopulations. 

Powering a trial for superiority can be financially risky. In some instances it may also prove unnecessary.

In August 2006 AstraZeneca completed the ARISE trial, which aimed to determine whether AGI-1067 was effective in reducing atherosclerosis in patients with acute coronary artery disease [1][2]. A double-blind, placebo controlled, Phase 3 trial, the primary efficacy endpoint was a composite endpoint which included major adverse cardiovascular events (MACE) like cardiovascular death, resuscitated cardiac arrest, non-fatal myocardial infarction and non-fatal stroke. However, it also included two less serious but more frequently observed events, namely hospitalization due to coronary revascularization and hospitalization due to unstable angina with evidence of ischemia [2]. 

When the FDA first began to require pharmaceuticals to perform cardiovascular outcome trials to establish the safety of certain new drugs, many worried that this new regulatory requirement would diminish investments in therapeutic areas like diabetes and obesity [1]. CVOTs are typically designed as massive time-to-event trials that need to enroll several thousands of patients to establish safety [2][3]. The sheer number of patients and size of the trial increases the time that it takes for these drugs to get to market.

So what is it the makes US and EU regulatory strategy different for diabetes and weightloss drugs, and how should this effect clinical development strategy?

A well-timed interim analysis can generally supply added benefits to the operational and administrative aspects of a clinical trial. Particularly when clean data and safety adjudications provide information that is instrumental for stopping a trial early or informing sensitive interim decisions, the timing of an interim look may play a crucial role in leveraging all of the flexibility that a complex, adaptive design has to offer. 

Cardiovascular outcome trials (CVOTs) have earned the reputation of being the untamable behemoths of the clinical world. Needless to say these trials are long and require extremely large sample-sizes. The Contrave LIGHT study required 8900 patients. The SAVOR TIMI trial enrolled 16,492 patients. Even the EXAMINE trial, which benefited from a promising zone design, required 650 patients. 

However, since the explosive controversy over the FDA’s conditional approval of anti-obesity drug Contrave four years ago, there is much we have learned about how to make these trials shorter while also diminishing the financial risks of investing in them. For example, one of our clients managed to shorten the expected study length of an a CVOT by two years using a four point MACE Assessment (see below). 

In this post, we explore some of the lessons we have learned when designing these large-scale clinical trials.  

A new publication co-authored by Cytel Co-Founder and President Cyrus Mehta considers a range of clinical development methods for cardiovascular outcome trials. Cardiovascular outcome trials, (often referred to as CVOTs), reflect safety standards implemented by the FDA and EMA to determine whether or not new drugs impose undue cardiovascular risk on patients. CVOTs typically occur after Phase 3 trials, and often make up for the slow rate of observed events by enrolling thousands of patients. This adds substantial delay in getting a drug to market.

In this paper, Cyrus and his co-authors explore how adaptive and group sequential methods might shorten this process without compromising the quality of the trial. In particular they consider increases in sample size and early stopping boundaries. They consider the possible benefits of unblinded sample size re-estimation (also known as the Promising Zone Design) in CVOT trials.