muscle wasting

A personal reason to develop a better gene therapy

/ Kevin McCormack / 2 Comments

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Credit : Allison Dougherty, Broad Communications

For Sharif Tabebordbar, finding a gene therapy for genetic muscle wasting diseases was personal. When he was a teenager, his father was diagnosed with a rare genetic muscle disease that eventually left him unable to walk.

In an interview with the Broad Institute at MIT he said: “I watched my dad get worse and worse each day. It was a huge challenge to do things together as a family – genetic disease is a burden on not only patients but families. I thought: This is very unfair to patients and there’s got to be a way to fix this. That’s been my motivation during the 10 years that I’ve been working in the field of gene therapy.”

That commitment now seems to be paying off. In a study published in the journal Cell, Tabebordar and his team at MIT and Harvard showed how they have developed a new, safer and easier way to deliver genes to help repair wasting muscles.   

In earlier treatments targeting genetic muscle diseases, researchers used a virus to help deliver the gene that would correct the problem. However, to be effective they had to use high doses of the gene-carrying virus to ensure it reached as many muscles throughout the body as possible. But this meant that more of the payload often ended up in the liver and that led to severe side effects in some patients, even a few deaths.

The usual delivery method of these gene-correcting therapies is something called an adeno-associated virus (AAV), so Dr. Tabebordar set out to develop a new kind of AAV, one that would be safer for patients and more effective at tackling the muscle wasting.

They started by taking an adeno-associated virus called AAV9 and then set out about tweaking its capsid – that’s the outer shell that helps protect the virus and allows it to attach to another cell and penetrate it to deliver the corrected gene. They called this new viral vector MyoAAV and in tests it quickly showed it had an enhanced ability to deliver genes into cells.

The team showed that it not only was around 10 times more efficient at reaching muscle than other AAVs, but that it also reduces the amount that reaches the liver. This meant that MyoAAV could achieve impressive results in doses up to 250 times lower than those previously used.

In animal studies MyoAAV showed encouraging results in diseases like Duchenne Muscular Dystrophy and X-linked myotubular myopathy. Dr. Amy Wagers, a co-senior author of the study, says they are hopeful it will be equally effective in people.

“All of these results demonstrate the broad applicability of the MyoAAV vectors for delivery to muscle. These vectors work in different disease models and across different ages, strains and species, which demonstrates the robustness of this family of AAVs. We have an enormous amount of information about this class of vectors from which the field can launch many exciting new studies.”

Using heart stem cells to help boys battling a deadly disorder

/ Kevin McCormack / Leave a comment

 

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Caleb Sizemore, a young man with DMD, speaks to the CIRM Board about his treatment in the Capricor clinical trial.

It’s hard to imagine how missing just one tiny protein can have such a devastating impact on a person. But with Duchenne Muscular Dystrophy (DMD) the lack of a single protein called dystrophin has deadly consequences. Now a new study is offering hope we may be able to help people with this rare genetic disorder.

DMD is a muscle wasting condition that steadily destroys the muscles in the arms and legs, heart and respiratory system. It affects mostly boys and it starts early in life, sometimes as young as 3 years old, and never lets up. By early teens many boys are unable to walk and are in a wheelchair. Their heart and breathing are also affected. In the past most people with DMD didn’t survive their teens. Now it’s more common for them to live into their 20’s and 30’s, but not much beyond that.

Results from a clinical trial being run by Capricor Therapeutics – and funded by CIRM – suggest we may be able to halt, and even reverse, some of the impacts of DMD.

Capricor has developed a therapy called CAP-1002 using cells derived from heart stem cells, called cardiospheres. Boys and young men with DMD who were treated with CAP-1002 experienced what Capricor calls “significant and sustained improvements in cardiac structure and function, as well as skeletal muscle function.”

In a news release Dr. Ronald Victor, a researcher at Cedars-Sinai Heart Institute and the lead investigator for the trial, said they followed these patients for 12 months after treatment and the results are encouraging:

“Because Duchenne muscular dystrophy is a devastating, muscle-wasting disease that causes physical debilitation and eventually heart failure, the improvements in heart and skeletal muscle in those treated with a single dose of CAP-1002 are very promising and show that a subsequent trial is warranted. These early results provide hope for the Duchenne community, which is in urgent need of a major therapeutic breakthrough.”

According to the 12-month results:

  • 89 percent of patients treated with CAP-1002 showed sustained or improved muscle function compared to untreated patients
  • The CAP-1002 group had improved heart muscle function compared to the untreated group
  • The CAP-1002 group had reduced scarring on their heart compared to the untreated group.

Now, these results are still very early stage and there’s a danger in reading too much into them. However, the fact that they are sustained over one year is a promising sign. Also, none of the treated patients experienced any serious side effects from the therapy.

The team at Capricor now plans to go back to the US Food and Drug Administration (FDA) to get clearance to launch an even larger study in 2018.

For a condition like DMD, that has no cure and where treatments can simply slow down the progression of the disorder, this is a hopeful start.

Caleb Sizemore is one of the people treated in this trial. You can read his story and listen to him describing the impact of the treatment on his life.