Spinraza, a life-saving drug for spinal muscular atrophy remains out of reach

He has type two spinal muscular atrophy - a cruel, degenerative disease with no cure.

But in a remarkable breakthrough there is now a drug available that has seen some astounding results.

The drug, Nusinersen (brand name Spinraza), has been approved for use in Australia, but was rejected for listing on the PBS last year.

Without government subsidy, the only approved drug to treat the disease would cost at least $1 million just for initial treatment.

William, who is three in April, was diagnosed with the disease on June 7, a date his parents will never forget.

"It's a disease that is very, very cruel," Ms Taylor said.

"He's lost the ability to walk, to crawl. You eventually lose the ability to breath, to swallow, to talk.

"Usually the majority of deaths from SMA are due to respiratory illnesses like pneumonia.

"He's slowly losing the ability to do things that he used to do.

"His self-feeding has declined, we have to help sit him up, sit him down and roll him at night."

Since William was diagnosed, both parents have found out they are carriers, meaning their children have a one in three chance of getting the disease.

The Karabar family was full of hope when Spinraza went before the Pharmaceutical Benefits Advisory Committee in December, expecting an early Christmas present.

But the committee rejected the application, saying it needed more information to form a view on the treatment's cost-effectiveness.

"Time is of the essence," Ms Taylor said.

"SMA children don't have time to sit and wait they need it now so they don't lose any more vital skills.

"If my son was diagnosed at birth and given the drug, he could be walking today. "

Spinal Muscular Atrophy Incorporation chief executive officer Julie Cini said children would die this year if they were continued to be denied the drug.

The drug company has made it available to type one diagnosed patients - whose life expectancy is usually just a few years - on compassionate grounds.

But for type two patients - whose life expectancy ranges from childhood to early adulthood depending on severity - there is no way to access the drug without paying.

Ms Cini said this had meant some type one children were now surpassing the milestones of type two diagnosed children.

The group is petitioning the government to fund the drug outside the usual PBAC regime.

"Does a child have to die before somebody thinks that child should have had that drug?" Ms Cini said.

"How many kids have to go into critical care?"

A clinical trial, with two of the study sites in Australia, showed positive results last year.

One of the study sites was led by paediatric neurologist Dr Michelle Farrer, from Sydney Children's Hospital and the University of NSW.

In the blind trial of nusinersen involving 122 patients worldwide, 41 per cent of babies with various SMA types reached motor milestones (such as sitting, crawling and walking), compared to none in the group receiving the placebo.

"It was clear the treatment was working. We were seeing babies getting stronger, defying the natural history of progressive weakness and limited survival," Dr Farrar said.

A spokesman for federal Health Minister Greg Hunt said the minister backed the listing of Spinraza on the PBS.

"Minister Hunt is strongly supportive of the listing of Spinraza and has both encouraged the company to submit further evidence to the March meeting of the independent Pharmaceutical Benefits Advisory Committee, and guaranteed that if the PBAC recommends it the government will list it," the spokesman said.

"Under legislation made by the Australian Parliament, the government can't include a new drug on the PBS unless it has first been recommended by the independent Pharmaceutical Benefits Advisory Committee."

For parents like Ms Taylor and Mr McLennan, all they can do in the meantime is make the best life possible for their children.

William's treatment is currently focussed around physiotherapy and keeping him clear of infections.

His parents are careful not to wrap him in cotton wool, wanting him to experience everything his peers do.

"I want my son to have good life," Ms Taylor said.