Horizon slumps after phase 3 Friedreich's ataxia trial flops

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Horizon has scrapped development of Actimmune in Friedreich's ataxia.

Horizon Pharma’s Actimmune has missed the primary endpoint in a phase 3 trial, sparking a 20% drop in its stock price. The study set out to show that interferon gamma-1b could improve outcomes in patients with the rare neurodegenerative movement disorder Friedreich's ataxia, but the drug failed to move the needle.

Dublin, Ireland-based Horizon enrolled 92 patients in the study and randomized them to receive either Actimmune or a placebo three times a week for 26 weeks. The study was primarily looking for changes to scores on the modified Friedreich's Ataxia Rating Scale, which assesses disease progression by looking at factors such as speech, limb coordination, gait and posture. Improvements over baseline in the treatment arm would suggest Actimmune was helping patients.

The data failed to show such improvements. And with Actimmune also failing to best placebo against secondary endpoints, Horizon has scrapped the Friedreich's ataxia development program. The move means Horizon won’t go ahead with a planned 26-week extension study.

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Horizon reached the decision after discussing the data with collaborators including the Friedreich's Ataxia Research Alliance (FARA). The company plans to sift through the data with FARA and the principal investigator in search of clues to inform further research, but it is the end of the line for Actimmune in the indication.

“While the results were not what we hoped for, this is the very reason why research and development is important—to find answers that may help inform future research,” Horizon CEO Timothy Walbert said in a statement.

Investors took a harder line on the misstep, driving down the value of Horizon’s stock when markets opened in the U.S.

The setback closes off one opportunity to grow sales of Actimmune, which is already approved for use in patients with chronic granulomatous disease and severe, malignant osteopetrosis.