Shares in the Dutch biotech Prosensa closed up over 24% on the Nasdaq after it presented positive fresh data on drisapersen, the rights to which have just been returned by GlaxoSmithKline, which showed that it may still be a valid treatment for Duchenne muscular dystrophy.

Earlier this week, GSK gave up on drisapersen, after it failed a late-stage study last September last year. The Phase III trial involved 186 boys suffering from DMD, a severely debilitating childhood neuromuscular disease that affects one in 3,500 live male births and is caused by mutations in the dystrophin gene.

Drisapersen did not meet the primary endpoint in the GSK study of a statistically significant improvement of distance walked in six minutes compared to placebo. The failure came just three months after the US Food and Drug Administration granted breakthrough therapy designation to the antisense oligonucleotide.

Now, at the JP Morgan healthcare conference in San Francisco, Prosensa has presented initial findings from further analyses from the aggregate data from the drisapersen clinical programme. Notably, 96-week extension data from the DEMAND III study show a 49 metre difference between those on continual treatment (n=52) and those who had been on placebo for 48 weeks followed by active drug (n=31).

Chief executive Hans Schikan said "we are encouraged by these results that suggest that treating earlier in the disease and treating longer shows a delay in the progression". He added that these data "encourage us to engage patient groups, clinical experts and regulators to explore a path forward for drisapersen, which includes the possibility of re-dosing".

Prosensa has also announced that it will make certain data from the drisapersen clinical programme available to the scientific community and it has initiated a study "to better understand the natural history of DMD".