PTC Therapeutics has presented clinical data on its Roche-partnered rival to Biogen and Ionis’ spinal muscular atrophy (SMA) drug Spinraza. The interim readout shows two-fifths of infants who received PTC and Roche’s oral SMA drug risdiplam were sitting eight months after starting treatment.
Risdiplam, a small molecule SMN2 splicing modifier, is the subject of a multi-front clinical program designed to show it improves outcomes in babies with Type 1 SMA and patients aged 2 to 25 years old who have Type 2 and 3 forms of the neuromuscular disorder. Researchers presented data from trials in both patient populations at the World Muscle Society annual congress this week.
In the first part of the Type 1 trial, researchers gave multiple ascending daily doses of risdiplam to 21 infants. Two of the infants died due to disease progression. Of the 14 participants with eight months of follow-up, six were able to sit as of the cutoff. Three of these six infants could sit without help.
The infants hit other motor milestones, too. Ten of the infants achieved full or partial head control, seven gained the ability to kick and four demonstrated rolling to the side. These outcomes translated into improved scores on the CHOP-INTEND motor skill assessment. The cohort achieved a median improvement of 16 points after eight months.
PTC compared the data favorably to natural history data, noting that infants with Type 1 SMA are never able to sit without treatment. However, if risdiplam comes to market it will have to do more than show it is better than not intervening at all. SMA patients can already access Biogen and Ionis’ Spinraza. And Novartis’ AveXis is moving a SMA gene therapy through the clinic.
Given the interim nature of the risdiplam data and challenges of cross-trial comparisons, it is hard to say exactly how PTC and Roche’s drug compares to these rivals. However, with a higher proportion of patients sitting and rolling in the risdiplam trial than in the pivotal Spinraza study, PTC and Roche are in a promising position, particularly as their oral asset may be more convenient for patients than Biogen’s drug.
PTC and Roche also presented data from the first part of a trial in Type 2 and 3 SMA patients. The use of different endpoints in the risdiplam and Spinraza trials in this population makes it hard to gauge how promising the data are compared to the competition. But participants in the risdiplam trial are outperforming the natural history data, suggesting PTC and Roche are well set as they head toward the readout from the fully-enrolled pivotal portion of the study.
“Patients with Type 2 and 3 SMA typically decline over the course of a year and the increase in motor function by over 3 points in SUNFISH when compared to natural history is exceptionally encouraging,” PTC CEO Stuart Peltz, Ph.D., said in a statement. “SMA is a systemic disease, and risdiplam which is an oral treatment that reaches all affected organs has the potential to be a best-in-class therapy.”