In 2017, an international clinical trial closed early because of concerns about a lack of progress in its intended aim: reducing scar tissue caused by heart attacks. Three years later, newly published data shows that the study, conceived at Cedars-Sinai, was on the right track after all.

Newly analyzed results suggest that the trial, known as Allogeneic Heart Stem Cells to Achieve Myocardial Regeneration (ALLSTAR), showed a clear benefit for patients. ALLSTAR applied infusions of cardiosphere-derived cells (CDCs)—heart stem cells from a patient’s own tissue—to try to heal the scars that increase the risk of further cardiac failure.

Compared with patients who received a placebo, those receiving CDC infusions showed a decrease in the volume of blood in the heart both before and after it beats—indicating that the organ had not dilated, as it does progressively in heart failure. This is notable and positive because, during cardiac failure, the heart gets bigger and bigger, like a swelling balloon.

In another sign of success, a blood protein that measures the severity of heart failure was reduced in patients receiving CDC infusions but not in those receiving placebo. A third trial, in which CDCs were used to treat Duchenne muscular dystrophy patients, also demonstrated positive results.