Spinraza rival? With DMD flops in the rearview mirror, PTC Therapeutics posts strong SMA data

After years trying to push a thrice-failed Duchenne drug into the US market (and ultimately failing to do so), PTC Therapeutics is finally onto something interesting.

Giovanni Baranello

The New Jersey company’s stock $PTCT is soaring on news of a completely different program — one partnered with Roche — that’s just impressed analysts and investors with updated data from a Phase I trial.

This drug, called risdiplam or RG7916, is being tested in babies with spinal muscular atrophy, a genetic condition that robs people of physical strength by affecting the motor nerve cells in the spinal cord. It’s the number one genetic cause of death for infants. The disease is caused by a gene mutation that prevents the body from producing a muscle development protein called SMN, which leads to atrophy of the muscles, motor impairment, and paralysis. Babies born with the severest kind of SMA never learn to crawl, sit up, or walk, and many lose the ability to breathe. They often die within 18 months.

PTC’s drug, licensed to Roche in 2011, is designed to replace the missing SMN protein — and it can be taken orally. The small trial tested RG7916 in 21 babies born with the severest form of SMA. In the updated Phase I data, the drug showed to improve motor function in patients, with a median improvement of 5.5 points in a test known as the CHOP-INTEND. This test, developed by the Children’s Hospital of Philadelphia, measures muscle development milestones.

Seeing improvement in muscle function this early was a bit of a surprise — which is why investors are so giddy.

“Data on motor function seem more encouraging when we consider that we are seeing motor function improvements and milestones achievement at this early stage of the study, which was essentially a dose-finding study and most of the infants included have received their first dose after the age of 5 months,” said investigator Giovanni Baranello at the Fondazione Istituto Neurologico Carlo Besta. “It is exciting to see evidence of clinical benefit from a systemic oral treatment for SMA.”

Analysts are positing that RG7916 could one day be competitive to Spinraza — the blockbuster SMA drug developed by Ionis and licensed by Biogen. Spinraza, also designed to boost SMN protein, is delivered via a shot to the spine. If PTC/Roche’s drug was equally effective but easier to take via pill, the medicine could be a solid rival.

It should be noted that there’s another potential Spinraza rival coming down the pipeline: a gene therapy developed by Avexis and recently bought by Novartis in the $8.7 billion Avexis buyout in April.

Regardless, the data are good news for PTC, a company that’s been plagued with bad news for years due to the failure (after failure after failure) of its Duchenne muscular dystrophy drug ataluren. That drug, approved in Europe, has so far failed to please regulators in the US. Although PTC still isn’t giving up on DMD, investors are surely happy to see the company moving on to greener pastures. The company’s stock is up 23% Monday morning, trading at $46.29 as of press time. That’s up from Friday’s close of $37.55 per share.

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