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Duchenne muscular dystrophy: safety and efficacy of Drisapersen

Duchenne muscular dystrophy is caused by dystrophin deficiency and muscle deterioration and preferentially affects boys. Antisense-oligonucleotide-induced exon skipping allows synthesis of partially functional dystrophin.
Efficacy and safety of Drisapersen, a 2′-O-methyl-phosphorothioate antisense oligonucleotide, given for 48 weeks were investigated.

In this exploratory, double-blind, placebo-controlled study ( DEMAND II ) researchers recruited male patients ( greater than or equal to 5 years of age; time to rise from floor less than or equal to 7 s ) with Duchenne muscular dystrophy from 13 specialist centres in nine countries during the period 2010-2012.

By use of a computer-generated randomisation sequence, researchers randomly allocated patients ( 2:2:1:1; block size of six; no stratification ) to Drisapersen 6 mg/kg or placebo, each given subcutaneously and either continuously ( once weekly ) or intermittently ( nine doses over 10 weeks ).

The primary endpoint was change in 6-min walk distance ( 6MWD ) at week 25 in patients in the intention-to-treat population for whom data were available.
Safety assessments included renal, hepatic, and haematological monitoring and recording of adverse events.

53 patients were recruited: 18 were given continuous Drisapersen, 17 were given intermittent Drisapersen, and 18 were given placebo ( continuous and intermittent groups combined ).

At week 25, mean 6MWD had increased by 31.5 m from baseline for continuous Drisapersen, with a mean difference in change from baseline of 35.09 m ( 95% CI 7.59 to 62.60; p=0.014 ) versus placebo.

No difference in 6MWD changes from baseline between intermittent Drisapersen ( mean change −0.1 ) and placebo ( mean difference 3.51 m [ −24.34 to 31.35 ] ) at week 25 was recorded.

The most common adverse events in Drisapersen-treated patients were injection-site reactions ( 14 patients given continuous Drisapersen, 15 patients given intermittent Drisapersen, and six given placebo ) and renal events ( 13 for continuous Drisapersen, 12 for intermittent Drisapersen, and seven for placebo ), most of which were subclinical proteinuria.
None of the serious adverse events reported ( one for continuous, two for intermittent, and two for placebo ) resulted in withdrawal from the study.

In conclusion, continuous Drisapersen resulted in some benefit in 6MWD versus placebo at week 25. The safety findings are similar to those from previous studies.
Ambulation improvements in this young population with early-stage Duchenne muscular dystrophy are encouraging but need to be confirmed in larger studies. ( Xagena )

Voit T et al, Lancet Neurology 2014; 13: 987–996

XagenaMedicine_2014