Roche and PTC Therapeutics have reported positive results from the second part of the SUNFISH trial of risdiplam to treat spinal muscular atrophy (SMA).

Risdiplam is an investigational, survival motor neuron-2 (SMN2) splicing modifier. The drug is intended to aid the SMN2 gene to generate more functional SMN protein.

The drug is said to increase and sustain SMN protein levels in the central nervous system and peripheral tissues. It is being developed as part of an alliance between Roche, PTC Therapeutics and the SMA Foundation.

SMA is an inherited, progressive neuromuscular disorder caused by the survival motor neuron 1 (SMN1) gene mutation, which leads to a deficiency of the SMN protein.

The two-part, double-blind, placebo-controlled SUNFISH study evaluated risdiplam to treat SMA type 2 or 3 patients aged two to 25.

Part one of the study determined the dose for the confirmatory part two, which evaluated the safety and efficacy of the drug.

The second part investigated participants’ motor function using total score of the Motor Function Measure 32 (MFM-32) scale at 12 months.

The MFM-32 scale is used to track the severity and progression of fine and gross motor function in patients with neuromuscular diseases, including SMA.

The study met the primary endpoint of change in the MFM-32 scale from baseline following one year of treatment with the drug compared to placebo.

Risdiplam’s safety was found to be consistent with its known profile, without any new safety signals. The drug did not demonstrate any safety findings that led to study withdrawal in any of its trials.

PTC Therapeutics CEO Stuart Peltz said: “The results from the study will be shared first with regulators globally and then will be presented at an SMA conference early next year. We believe that risdiplam has the potential to enter the market with a best-in-class profile for patients with all SMA types.”

The drug is being further studied in FIREFISH, JEWELFISH and RAINBOWFISH trials as an SMA treatment.