(Reuters) -Sarepta said on Monday that its late-stage study testing two gene-targeted therapies for Duchenne muscular dystrophy did not meet the main goal, sending its shares plummeting over 27% in extended trading.

The study took nine years to complete and enrolled 225 patients aged 6 to 13 with Duchenne, a rare genetic disorder that causes progressive muscle weakness and mostly affects boys.

The trial was designed to evaluate the therapies, casimersen and golodirsen, which belong to a class of drugs called phosphorodiamidate morpholino oligomers, or PMOs.

These therapies help certain patients produce a shorter but functional version of the dystrophin protein.

The main goal was to show a statistically significant improvement in how quickly patients could climb four steps after 96 week

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