CHICAGO -- New research published online today in Circulation Research found that injections of adult patients' own CD34+ stem cells reduced reports of angina episodes and improved exercise tolerance time in patients with chronic, severe refractory angina (severe chest discomfort that did not respond to other therapeutic options).
The phase II prospective, double-blind, randomized, controlled clinical trial was conducted at 26 centers in the United States, and is part of a long-term collaboration between researchers at Northwestern University Feinberg School of Medicine and Baxter International Inc. The objective of the trial was to determine whether delivery of autologous (meaning one's own) CD34+ stem cells directly into multiple targeted sites in the heart might reduce the frequency of angina episodes in patients suffering from chronic severe refractory angina, under the hypothesis that CD34+ stem cells may be involved in the creation of new blood vessels and increase tissue perfusion.
"Early research across multiple disease categories suggests that stem cells generated within the body in adults may have therapeutic benefit. This is the first controlled trial treating chronic myocardial ischemia (CMI) patients with their own stem cells to achieve significant reductions in angina frequency and improvement in exercise tolerance," said lead investigator Douglas W. Losordo, MD, director, Feinberg Cardiovascular Research Institute and the Eileen M. Foell Professor of Heart Research at Northwestern's Feinberg School of Medicine and director, Program in Cardiovascular Regenerative Medicine at Northwestern Memorial Hospital. "While we need to validate these results in phase III studies before definitive conclusions can be drawn, we believe this is an important milestone in considering whether the body's own stem cells may one day be used to treat chronic cardiovascular conditions."
The research team mobilized and extracted stem cells from all participants before randomizing them to one of three treatment groups: low- or high-dose cell concentrations, or placebo, and administered the regimens in 10 distinct sites in the heart tissue through a multi-point injection catheter.
At six months after treatment, patients in the low-dose treatment group reported significantly fewer episodes of angina than patients in the control group (6.8 vs. 10.9 episodes per week), and maintained lower episodes at one year after treatment (6.3 vs. 11 episodes per week). Additionally, the low-dose treatment group was able to exercise (on a treadmill) significantly longer at six months after treatment, as compared with those in the control group (139 seconds vs. 69 seconds, on average). Angina episodes and exercise tolerance rates were also improved in the high-dose treated group at six months and at one year post treatment compared to the control group.
"The concept of using one's own stem cells to treat disease is highly attractive to the medical community and this research is consistent with Baxter's commitment to driving scientific advances that can lead to promising new treatments for critically ill patients," said Norbert Riedel, Ph.D., Baxter's chief scientific officer. "These results provide important insights into the potential for these cells to be used in larger scale settings, and we look forward to moving into phase III studies in the near future to hopefully substantiate these results."
When comparing major adverse cardiac events, there was no evidence of complications related to the autologous stem cells. Three deaths occurred during the trial, one from procedural complications due to the inherent risks of cardiac surgery, the others unrelated to the treatment (all in the control group). Myocardial infarction (MI or heart attack) occurred in seven of the control group patients. There were three MIs each in the low-dose and high-dose patient groups.
Previous preclinical studies of autologous CD34+ stem cells have shown an increase in capillary density and improved cardiac function in models of acute and chronic myocardial ischemia. This phase II study is based on a phase I/II study, which provided early evidence of the feasibility, safety and bioactivity of these autologous stem cells in a similar setting.
Angina is characterized as chest discomfort due to a lack of sufficient blood supply to the heart associated with obstructive coronary artery disease (CAD). More than 850,000 patients in the United States experience refractory angina that has not responded to other therapeutic options, according to current estimates. This leads patients to reduce their activity levels significantly and negatively impacts their quality of life.