A drug that promises to overcome the limitations of current products used in imaging studies of coronary artery disease has achieved promising results in a Phase III study.

Regadenoson, developed by CV Therapeutics of the US and licensed to Japan’s Astellas, proved to be at least as effective as Astellas’ market-leading Adenoscan (adenosine) in the first of two Phase III trials designed to support its approval for myocardial perfusion imagining (MPI) in the USA. The second is ongoing and due to complete in early 2006. If successful, it will lead to a marketing application being filed for regadenoson in the USA.

The drug is a selective A2A adenosine receptor antagonist and is intended for use as a pharmacologic stress agent in MPI studies. In MPI testing, blood flow to the heart is measured during a period of exercise (stress) and is compared to the heart’s blood flow at rest. Agents such as Adenoscan are used to stress the heart in patients physically unable to exercise for the duration of the test.

According to CV Therapeutics, around 40% of patients who need an MPI test are unable to exercise, which has made Adenoscan a lucrative product for Astellas, with sales running at around $240 billion dollars a quarter [[02/02/05d]].

But Adenoscan can result in unwanted side effects, including flushing, dyspnea, and headache, and should not be used in patients with asthma, so there is a clinical need for an alternative drug. And unlike Adenoscan regadenoson can also be delivered by bolus injection, rather than infusion, which could reduce the cost and complexity of MPI testing.