Scientists believe they may have found a way to ward off heart failure associated with Duchenne muscular dystrophy (DMD).
The heart is weakened in muscular dystrophy
Many people with DMD die in their 20s because their heart weakens and fails.
The experimental drug works as a chemical sticking plaster and strengthens heart muscle cells, making them less likely to break under strain.
Although the drug was tested in mice, the University of Michigan authors told Nature it may also work in humans.
However, they said many more studies were needed to verify this.
Lead researcher Dr Joseph Metzger said: "If issues of dosing and long-term safety can be resolved, our research suggests that poloxamer 188 could be a new therapeutic agent for preventing or limiting progressive damage to the hearts of patients with muscular dystrophy."
Several more years of animal research will be needed before trials can begin in humans, he said.
The study is also the first to show what happens to heart muscle cells in DMD.
DMD is caused by a genetic mutation in the gene that makes the protein dystrophin. These leads to progressive weakening and breakdown of muscle in the body, including the heart.
By looking at mice with the mutation, Dr Metzger's team found the heart muscle cells failed to relax and lengthen as readily as those in healthy mice without the mutation. This makes them prone to damage.
Dr Metzger explained: "They are stiffer than normal heart muscles cells and vulnerable to damage when stretched. That's where poloxamer 188 comes in."
The drug is a chemical sealant. To test whether it would help they devised a special stretching machine to work the heart muscle cells.
Without the drug, the cells became unstable, started shaking and showed evidence of damage.
However, when poloxamer 188 was added, the cells were able to handle the stretching with no problem, in the same way as healthy heart muscle cells.
When the researchers infused the drug into mice with DMD they found it restored the volume of the hearts major pumping chamber to that of normal mice.
The researchers then gave the DMD mice that had been treated with poloxamer 188 another drug to put stress on the heart and make it work harder and faster for 30 minutes.
None of the mice went into heart failure compared to 40% of DMD mice that had not had poloxamer 188 before being given the stressor drug.
Poloxamer 188 has already been tested in humans with sickle cell anaemia and was found to be safe in the short term - 24 hours of use.
However, because DMD is a chronic disease, the drug would be used for much longer periods in these instances. The long term safety, therefore, needs to be confirmed, stressed the researchers.
Professor Francesco Muntoni, professor of paediatric neurology at Imperial College London, said the work was very interesting and he thought human trials should go ahead.
"Either poloxamer 188 or something similar may well be something that can be used in clinical trials."
He said it would also be interesting to check whether the drug could limit damage to other muscle in the body in patients with DMD.
The British Heart Foundation said much more safety data was needed.
"The long term safety of this substance is not clear and concerns about this have been voiced by the researchers," said a spokeswoman.