The US National Heart, Lung, and Blood Institute (NHLBI) has paused a clinical trial of stem cells to treat heart failure after questions were raised about the validity of the science behind it.

The institute made the decision “out of an abundance of caution to ensure the study continues to meet the highest standards for participant safety and scientific integrity”, it said in a statement released on 29 October.

The study was based on research done by cardiologist Piero Anversa at Harvard Medical School and Brigham and Women’s Hospital in Boston. In 2002, he suggested that a type of stem cell in the heart, called c-kit cells, could regenerate heart muscle ¹ . The NHLBI study gave people with chronic heart failure infusions of c-kit cells or combinations of c-kit cells and bone marrow stem cells. It launched in 2015 with the goal of enrolling 144 participants; so far 125 patients have signed up.

Doubts about Anversa’s work arose in the early 2000s after other researchers failed to replicate his findings and questioned whether cardiac stem cells existed ^{2 , 3 , 4} .

Anversa closed his lab in 2015 and left Harvard. In 2017, Partners HealthCare System — which runs Brigham and Women’s Hospital — paid the US government US$10 million as part of a settlement over accusations that Anversa’s team had submitted fraudulent data in order to obtain federal funds.

Earlier this month, the hospital and Harvard called on journal editors to retract 31 of Anversa’s papers, after their investigations found that they contained data that had been manipulated or fabricated.

Anversa could not immediately be reached for comment.

The NHLBI says that the decision to halt the study was due to concerns about Anversa’s animal studies, and not due to any data generated by the trial itself. The agency says that it does not believe that the trial has compromised patient safety.