Doctors are hopeful that a newly developed drug could be a much-needed breakthrough for children with spinal muscular atrophy, an incurable disease that often leads to paralysis and early death.

The progressive condition kills more infants than any other genetic disease, and about one in 6,000 babies are born with SMA. The disease can cause muscle weakness so severe that some children struggle to breathe.

Doctors involved in two international clinical trials were testing an experimental drug called nusinersen against a placebo on hundreds of children with the two most serious types of SMA -- type 1 and type 2 -- when they made the discovery.

In just a few months, scientists saw children on the drug get stronger while children on the placebo became weaker. Those treated with nusinersen showed significant improvements in muscle control. Some even gained the ability to sit on their own and crawl.

Both trials were cancelled early because the results were so promising that doctors couldn’t continue to administer the placebo in good conscience.

“It’s an amazing feeling, because this is the first time in the history of this disease where we can offer treatment to these babies,” Dr. Jiri Vajsar, a neurologist from the Hospital for Sick Children in Toronto, told CTV News.

Nusinersen is injected into the spine and works by delivering pieces of synthetic DNA to block the disease’s process.

Parents of children on the experimental drug say the results are indeed promising. Lilah Lamont, a 10-month-old girl with SMA, had her first injection about a month ago. Since then, her parents said they’ve seen small improvements.

“She has some leg moment. She moves her arms a bit more now as well. She smiles a lot bigger. She has definitely a stronger grip on our hands. It’s amazing to see,” said her father, Eric Lamont.

Cases like Lilah’s could be the first indicators of a major shift in future SMA treatment, doctors say.

“What we’re seeing is that kids who got treatment are actually improving over their baseline function. So we’re seeing positive results,” said Dr. Craig Campbell, a paediatrician with the Children’s Hospital at London Health Sciences Centre.

There is still no price tag on the drug, and it has yet to be approved for widespread use. The drug’s maker has applied for expedited approval in hopes of getting the drug to patients as soon as possible.

In the meantime, children involved in the research are being given nusinersen for free. That’s good news for children like Sophie Blair in London, Ont., whose mother has seen positive results since the little girl began receiving the doses.

“She can put her hands above her head now. When she started shuffling around on the floor again, that’s pretty good,” said Sophie’s mother, Jennie Ogden.

One in approximately 40 people carry the gene that can cause SMA, and both parents must be carriers to pass along the condition. Even if both parents are carriers, there is about a 25 per cent chance their child will be born with SMA, according to the Families of Spinal Muscular Atrophy Canada Society.

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip