Cytokinetics cans lead drug after phase 3 ALS wipeout

Cytokinetics reported numerical differences between the placebo and treatment arms but shied away from trying to spin a future for the asset.

Cytokinetics has stopped development of its lead drug. The San Francisco-based biotech made the decision after tirasemtiv failed to beat placebo against the primary endpoint or any of the secondary goals in a study of more than 700 patients with amyotrophic lateral sclerosis (ALS).

Researchers set out to learn whether tirasemtiv, a fast skeletal muscle troponin activator, could drive greater improvements on a measure of lung capacity than placebo over 24 weeks. Tirasemtiv failed to clear that bar. 

Cytokinetics reported numerical differences between the slow vital capacities of the placebo and treatment arms, particularly among patients who received and could tolerate higher doses of its drug, but shied away from trying to spin a future for the asset.


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“We have decided to suspend the development of tirasemtiv,” Cytokinetics CEO Robert Blum said in a statement.

That decision was simplified by the comprehensiveness of the phase 3 flop. The primary endpoint miss was compounded by tirasemtiv’s inability to beat placebo against any of the 48-week secondary endpoints, which assessed the drug’s effect on an ALS functional rating scale and muscle strength. Tirasemtiv also failed a phase 2b in ALS back in 2014. 

Cytokinetics’ decision to drop tirasemtiv was also influenced by its belief its pipeline contains a candidate that addresses the shortcomings of its now ex-lead asset. 

That drug, CK-2127107, is another fast skeletal muscle activator that has delivered phase 1 data suggesting it may offer better tolerability and efficacy than its more advanced sibling. Tirasemtiv’s ability to cross the blood-brain barrier limited its therapeutic window. 

With more than $300 million in cash and investments at the last count, Cytokinetics has the means to push CK-2127107 down the pipeline without tapping its backers for money. 

Shares in the biotech fell 27% following news of the phase 3 failure.

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