Why Merrimack Pharmaceuticals (MACK) Stock Hit a One-Year High Today (Update)

Update (4:52 p.m.): Updated with Thursday market close information.

NEW YORK (TheStreet) -- Merrimack Pharmaceuticals  (MACK) soared more than 60% to a one-year high of $7.65 on Thursday after the company announced its experimental cancer treatment MM-398 showed improved results in a late-stage study.

The company announced the treatment improved the overall survival rate in patients with metastatic pancreatic cancer when used in combination with two other drugs in the study. Merrimack said the drug combination yielded an overall survival rate of 6.1 months, compared to 4.2 months yielded by the other two drugs in patients who had previously received the chemotherapy drug gemcitabine.

The stock closed up 59.23%, or $2.60, to $6.99. Nearly 30 million shares changed hands, which eclipsed the average volume of 1,352,450. The stock hit a low of $6.55 for the day and holds a 52-week low of $2.05.

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