Discussion
The CANVAS trial has successfully recruited 4,330
individuals with T2DM to address the initial objectives
of the study. The characteristics of the participants
enrolled are mostly representative of a high-risk diabetic
population, both in terms of the nature of the complications
reported and the types of treatments they are
receiving. The proportion of participants with a history of
atherosclerotic vascular disease is higher than is typically
observed in this patient group but this reflects the
inclusion criteria that targeted the enrolment of individuals
with ischemic macrovascular complications. The
study is well placed to provide a robust assessment
of the effects of canagliflozin in a diverse population
group to which the agent might ultimately be applied in
clinical practice.
The study was designed to be done in 2 phases using
a novel, scientifically robust approach. The rationale
for the phased design was that it would enable key
safety information to be collected for regulatory
purposes, concurrent with the accrual of the data
required to address the primary hypothesis of cardiovascular
protection. The data from the initial follow-up
of the 4,330 participants included in phase one of the
study was also intended to provide insight into the
effects of the agent on biomarkers, with second phase
recruitment to progress only if there was evidence of
effects that would be expected to translate into
cardiovascular protection.
Fundamental to this study design was the capacity to
prevent the release of interim data defining the effects of
the compound on cardiovascular outcomes. Unblinding
of the primary outcome effect estimate at any point
before completion of the study would represent a
significant breach in the integrity of the trial and
undermine the design principles. Accordingly, a series
of procedures were put in place to ensure the effect
estimate remained blinded and plans were developed
such that the review of the data by the regulators would
not require disclosure of the effects on the cardiovascular
outcome. This was based upon identifying a specific and