Cytokinetics axes lead drug after it implodes in a PhIII muscle trial for ALS, shares crater

Cytokinetics $CYTK lead muscle drug has crashed in a Phase III study for ALS.

The biotech reported this morning that tirasemtiv, designed to amp up the muscles of sick patients, failed to hit the primary endpoint on what’s called slow vital capacity, which measures how much air can be exhaled. And now the therapy is being shelved as the biotech’s stock craters, plunging more than 30% Tuesday morning.

Robert Blum

The decline in SVC was slower in the drug arms compared to a placebo, but it never achieved statistical significance. The mid- and high-dose arms had the best responses, but it wasn’t enough. And now the South San Francisco-based biotech plans to shift focus to a next-gen drug in the pipeline, where it feels it has a better shot at success, and kill the tirasemtiv program.

That’s also bad news for Astellas, which committed $95 million in cash to Cytokinetics in order to get an option on the drug as well as the earlier-stage therapy Cytokinetics will now turn to. Astellas also included up to $100 million in milestones for the work.

While disappointing for investors, it can’t be a big surprise to researchers in the field. Three years ago Cytokinetics reported that tirasemtiv — which is designed to increase muscle sensitivity to calcium –flunked the primary and a range of secondaries for ALS, scoring only on SVC. Failed mid-stage drugs face tough odds when they are pushed into late-stage testing, as Cytokinetics knows all too well this morning.

ALS remains one of the toughest targets in drug R&D, defeating multiple attempts at addressing a disease that involves motor neurons and the steady and remorseless decline of a patient’s muscle activity, leading to death. Riluzole was the only drug approved for ALS in the US, arriving in 1995, and remained in a class by itself until Mitsubishi Tanabe’s Radicava was added earlier this year. Neither come close to stopping the disease.

Cytokinetics CEO Robert Blum noted:

We have decided to suspend the development of tirasemtiv. While we believe that VITALITY-ALS demonstrated pharmacologic activity for the mechanism of action, we also believe that limitations of tirasemtiv may be addressed with our next-generation fast skeletal muscle activator, CK-2127107.  Based on previous Phase 1 clinical studies, we believe CK-2127107 will be better tolerated and potentially more effective than tirasemtiv in patients with ALS and look forward to Phase 2 trial results in 2018.

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Recursion Pharmaceuticals Salt Lake City, UT
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