Melbourne company Mesoblast has announced positive results from preclinical trials of its patented adult stem cells injected by catheter directly into damaged heart muscle of sheep after a heart attack.

The trials were conducted at the Texas Heart Institute by Mesoblast's United States-based sister company, Angioblast Systems, using catheters from two of partner Johnson & Johnson's companies, Cordis Corporation and Biosense Webster.

The objective of the trials was to establish the safety and effectiveness of the stem cells in a clinically relevant and widely applicable protocol using catheters to implant the cells in damaged heart muscle of sheep shortly after a heart attack and re-opening of a blocked artery.

In the trial, 15 sheep with heart attacks underwent an early procedure to re-open the blocked artery, followed five to 10 days later by cardiac catheter injection. Stem cell implantation by catheter resulted in significant improvement of heart function and reduction in heart failure at the two-month endpoint of the study.

The company has now completed a number of large animal studies for the collation of data to be provided to the United States Food and Drug Administration (FDA) to support its Investigational New Drug (IND) submissions.

The studies have focused on treatment of heart attacks using cells from a non-related (allogeneic) donor which have been expanded and frozen: in effect, an 'off-the-shelf' stem cell product.

The Texas Heart Institute study establishes that the allogeneic stem cells can be implanted safely by cardiac catheter and are effective when used in combination with standard-of-care therapies to improve vascular blood flow, such as balloon angioplasty.

The results of this catheter-based protocol will now be used to support Angioblast's upcoming FDA submissions for Phase II clinical trials.