Why Cytokinetics (CYTK) Stock Is Plummeting Today (Update)

Update (4:15 p.m.): Updated with Friday market close information and one-year low price.

NEW YORK (TheStreet) -- Cytokinetics  (CYTK) plummeted more than 64% to a one-year low of $4.57 on Friday after the biotechnology company announced its experimental treatment for Lou Gehrig's disease failed to meet its primary goal in a mid-stage trial.

The study measured the efficacy of one of the San Francisco-based company's main experimental drugs, tirasemtiv, on amyotrophic lateral sclerosis, or ALS. The study tested the drug against a placebo in 711 patients. 

The stock closed at $4.59, down 64.67% or $8.40 from its previous close of $12.99, at the close of trading on Friday. The stock continued to fall 2.4% to $4.48 in after-market activity. More than 17 million shares changed hands on Friday, well above the average volume of 1,054,580.

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