Roche presses pause on PTC's SMA drug over a safety scare

Roche ($RHHBY) has suspended dosing in a Phase II trial of PTC Therapeutics' ($PTCT) in-development spinal muscular atrophy (SMA) trial, cautious of a potential safety problem stemming from a preclinical study.

The drug, RG7800, is in the midst of a 64-patient Phase II trial designed to determine its safety and efficacy in SMA, a rare and debilitating disease. RG7800 was well tolerated in a Phase I study on healthy volunteers, PTC said, and it charted a dose-dependent effect on the SMN2 gene, whose deficiency plays a role in the disease.

However, in long-term data from animal tests, investigators ran into an "eye finding," the company said in a regulatory filing. And, "as a precautionary measure, the collaboration partners decided in April 2015 to temporarily suspend dosing of additional patients to evaluate this finding and confirm next steps" for the ongoing Phase II trial, according to PTC.

The company isn't disclosing just what the finding was but did note that the animals in question were exposed to more RG7800 than any patient in any study thus far, and that the issue hasn't arisen in human trials. PTC didn't respond to a request for further details.

Roche bought an exclusive license to the program in 2011 for $30 million up front and up to $460 million down the road, partnering with PTC and its collaborators at the SMA Foundation. Earlier this year, the Swiss drugmaker signed on to pay as much as $545 million for Trophos, a French biotech at work on a Phase II SMA treatment that Roche has said could become the first approved therapy for the disease.

Meanwhile, PTC is pressing forward with its controversial Duchenne muscular dystrophy (DMD) drug amid rumors that management is looking around for potential buyers. The biotech won early European approval for the DMD-treating ataluren despite an earlier Phase II failure, and PTC is now working through Phase III with the goal of posting top-line data by year's end. Keeping ataluren on the European market is contingent on success in Phase III, and the same goes for a potential FDA nod for the drug.

- read the filing