Discussion: The primary objective was achieved - the continuous treatment arm showed a clinically meaningful and statistically significant difference from placebo on 6MWD at week 24. At week 48, both treatment arms showed a clinically meaningful difference from placebo on 6MWD (supported by improvement in other secondary endpoints). Drisapersen may represent an important treatment option for boys with DMD having mutations correctable by exon 51 skipping.
My quick thoughts:
A statistically significant drisapersen benefit on the six-minute walk test validates the drug's "exon-skipping" mechanism of action, which in turn, also helps to confirm the benefit already seen by Sarepta's eteplirsen. I said earlier this week that positive data from the drisapersen study should be viewed as a positive for Sarepta, and I still believe that.
It's hard to read too much into just how well drisapersen is working for DMD patients based on these data, but keep in mind that the data in the abstract are just placebo adjusted improvements in the six-minute walk test. We don't yet know baseline levels for patients, so we don't know if drisapersen patients actually improved their performance on the six-minute walk test over 24 weeks, or if the "benefit" was derived from placebo patients getting worse.
There is no data on dystrophin production in the abstract, which is disappointing. It's not clear if dystrophin levels were measured as part of this phase II study.
The safety profile of drisapersen is a bit better than expected, with all patients completing the study. We know that some drisaspersen patients in other ongoing studies have been hospitalized due to kidney toxicity and low white-blood cell counts. Eteplirsen's superior safety profile compared to drisapersen could be a positive, differentiator for Sarepta.
-- Reported by Adam Feuerstein in Boston.