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Biogen reported disappointing results Sunday from a late-stage clinical trial involving its experimental treatment for a rare, genetically defined form of amyotrophic lateral sclerosis, or Lou Gehrig’s disease.

In the Phase 3 study, the Biogen drug called tofersen failed to slow the neurologic and functional decline of ALS patients compared to a placebo. The drug showed some improvements on other measures of disease progression, the company said, although interpreting those secondary results is challenging because the study’s main goal was not met.


Tofersen targets an inherited form of ALS that is diagnosed in approximately 100 patients each year — just 2% of the overall diagnoses. Still, the negative study results are another unfortunate setback for the broader ALS patient community. ALS is a progressive and fatal neurodegenerative disease that has proven acutely resistant to effective treatments.

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