Exercise treadmill testing for efficacy evaluation in randomized, controlled trials.

Area of Science:

• Cardiology
• Clinical Trials
• Pharmacology

Background:

• Exercise treadmill testing is a standard measure for functional capacity and myocardial ischemia, often used as an endpoint in clinical trials.
• Microvascular angina is a condition affecting functional capacity, and disease-modifying therapies are under investigation.
• Zibotentan, a selective endothelin-A receptor antagonist, was evaluated for its potential to treat microvascular angina.

Purpose of the Study:

• To evaluate the efficacy of zibotentan in improving functional capacity and angina symptoms in patients with microvascular angina.
• To analyze changes in exercise duration across sequential study visits within the trial.
• To identify factors associated with within-trial changes in exercise duration.

Main Methods:

• A randomized, double-blind, cross-over trial design was employed.
• Participants received either zibotentan (10-mg daily for 12 weeks) or a placebo.
• The primary outcome measure was exercise duration assessed via exercise treadmill testing.

Main Results:

• Zibotentan did not significantly improve exercise duration or angina symptoms compared to placebo.
• Exercise test duration increased progressively across sequential study visits for all participants, irrespective of treatment.
• This improvement in exercise duration was significantly associated with female sex (p=0.002).

Conclusions:

• Exercise treadmill testing may have limitations as an objective endpoint for efficacy in randomized trials.
• The observed improvement in exercise duration over time suggests a learning or adaptation effect, not solely attributable to the drug.
• Female sex was identified as a factor associated with improved exercise duration within the trial.