Canadian Study of Arterial Inflammation in Patients With Diabetes and Vascular Events: EvaluatioN of Colchicine

Inflammation is a key to atherosclerosis and its serious effects (MI, stroke) and represents a potentially transformative therapeutic target. Several recent trials have revealed potential outcome benefit in patients with cardiovascular disease who are treated with anti-inflammatory therapy. The LoDoCo trial showed a reduction in cardiovascular events in patients with known coronary artery disease who were treated with colchicine (1). Although the LoDoCo trial did show outcome benefit, and in fact reduced the number of acute coronary syndromes in the treatment group, colchicine's mechanism of action at the level of the atherosclerotic plaque in patients remains unknown. The COLCOT trial was recently published which further demonstrated the potential benefit of anti-inflammatory therapy with colchicine. Compared with placebo, colchicine significantly reduced the risk of cardiovascular events for patients who recently experienced a myocardial infarction (2). It is not clear at the present time whether colchicine mainly reduces the systemic inflammatory milieu, thus reducing the likelihood of plaque progression and new lesion formation; or whether it has a direct effect on local "hot" inflammatory cell activity, thus pacifying the inflammatory plaque to reduce events. Insight into colchicine's mechanism of action may help identify the most suitable patients for this novel approach.

Inflammation imaging may represent a solution. 18F-fluorodeoxyglucose (FDG) PET-CT imaging can define plaque inflammation and identify patients and plaques vulnerable to rupture and events. Improved FDG uptake occurs with therapies that effectively reduced vascular events but not with therapies with no outcome benefit. It is provocative to consider inflammation imaging strategies that may positively impact therapy decisions to yield better patient selection and outcomes.

The long term goal of this research is to determine the pathobiological effect of colchicine on plaque inflammation and determine if inflammation imaging can be integrated into clinical assessment to personalize decisions for anti-inflammation therapies. As the first step for this goal, the investigators propose The CADENCE study is the first step towards this goal; it is a mechanistic and proof-of-concept study that will be the basis for a future 2nd phase definitive RCT integrating inflammation imaging and biomarker strategies.

The Primary Objective is to determine the pathobiological effect of the medication colchicine compared to placebo, on plaque inflammation (measured by 18F-fluordeoxyglucose (FDG) PET/CT at baseline and 6 months) in the carotid arteries and thoracic aorta in high-risk patients with diabetes or pre-diabetes and recent vascular events (ACS/MI, TIA, stroke) to investigate whether its mechanism of action is primarily systemic or local at the plaque level. FDG PET/CT has been demonstrated to offer a pragmatic method to assess inflammation in the aorta.1 Several studies confirm that therapies that reduce aortic FDG uptake mirror clinical efficacy..

Secondary Objectives are to determine: a) whether baseline inflammation imaging (FDG PET/CT) and/or inflammation biomarker (hs-CRP) levels can identify the patients most likely to have a positive response to colchicine measured by the change in FDG uptake over 6 months; b) the relationship of the inflammation response on FDG PET/CT to hs-CRP at baseline and over the 6-month time-frame.

Exploratory Objectives are to determine: a) if there are regional differences (i.e. carotid or aorta) in response to colchicine in patients with recent coronary (ACS/MI) versus those with recent cerebral events (TIA, stroke); b) if other systemic inflammation biomarkers (e.g, IL-6, IL-1β, TNF-α, MCP-1, others) also predict the response to colchicine; c) the relationship of inflammation on FDG PET/CT to: i) systemic inflammation biomarkers; ii) monocyte activation; d) treatment effect on clinical outcomes such as major adverse CV events and all-cause mortality; and e) the effect on quality of life outcomes.

Methods:

In CADENCE patients with T2DM or pre-diabetes and a recent NonSTEMI, STEMI, stroke or TIA will be recruited to one of 2 arms: colchicine 0.6 mg daily; or placebo. At baseline and 6 months: patients will have FDG PET-CT of carotids and aorta; at 0, 3 and 6 months: clinical evaluation and blood sampling for inflammation biomarkers (eg hsCRP, IL-6, IL-1β, TNF-α, MCP-1). The primary endpoint will be the change in inflammation over 6 months measured as FDG tissue to blood ratio (TBR).

Expected Outcomes:

It is expected that colchicine will reduce arterial inflammation measured using FDG PET/CT and reduce biomarkers of systemic inflammation. This would validate that colchicine's mechanism of action is more than a systemic effect but also a local action at the level of the vessel wall and plaque. This would further identify arterial inflammation on imaging as a potential novel therapeutic target for those at high risk of CV events. Such proof-of-concept data would support a definitive RCT to evaluate and define the potential for new biomarker-imaging strategies to direct decisions for novel anti-inflammation therapies in this population.

Current therapies focus on lesion stenosis or ischemia with conflicting results. Use of inflammation imaging to direct proven treatments would be a bold practice-changing paradigm shift.