Baxter Healthcare has advanced a human stem cell therapy for patients with coronary artery disease into Phase II testing, the first time this type of treatment has progressed to this stage of clinical development in the USA.

The move follows encouraging results from a 24-subject Phase I trial, which showed that stem cell therapy led to improvements in chest pain and exercise capacity in two thirds of patients with chronic myocardial insufficiency, a particularly severe form of CAD, and allowed them to reduce their requirement for nitrate drugs.

In CMI, blood vessels supplying the heart muscle become narrowed and blocked, leading to unstable angina, heart attacks and progressive heart failure unless blood flow to the affected area is restored. It affects 125,000 to 250,000 people in the USA each year.

Baxter’s Phase II procedure involves mobilizing stem cells from the bone marrow and into the blood using granulocyte-colony stimulating factor (G-CSF), harvesting them from the blood, and then injecting them directly into the areas of the heart which suffer from poor blood flow. The aim is to stimulate the formation of new blood vessels that will improve the delivery of oxygen and nutrients to the affected regions.

Critically, Baxter’s technique does not involve the use of embryonic stem cells, still the subject of a US government-imposed moratorium that prevents new cell lines being produced.

The trial will enroll approximately 150 adult patients who are currently on maximal medical therapy and are not suitable candidates for conventional procedures to improve blood flow to the heart, such as angioplasty, stents, or coronary artery bypass surgery. If successful, a Phase III programme could get underway in 2007.

Last week, German researchers reported in the Journal of the American Medical Association that giving G-CSF to patients with CAD was not effective in treating the disease. The hope was that mobilizing stem cells into the blood would be enough to encourage the growth of new blood vessels in the damaged heart.

Commenting on the results, Amit Patel, director of cardiac stem cell therapies at the University of Pittsburgh Medical Center in the USA, said: “Cell therapy is still in its infancy. No one knows why adult stem cells work. At this early stage, mobilizing cells systemically and hoping they’ll know where to go and what to do is simply unrealistic. The most effective way to treat patients is by administering the cells directly into the organ.”

Other companies vying to develop stem cell therapies for human diseases include US companies Ceregene, Geron, Novocell, StemCells and ViaCell, as well as NsGene of Denmark and the UK’s ReNeuron.