NEW YORK (TheStreet) -- Shares of Ambit Biosciences  (AMBI) exploded 85.24% to $15.19 in afternoon trading Monday after Japanese drug maker Daiichi Sankyo (DSNKY) agreed to purchase the company for approximately $315 million.

Daiichi Sankyo cited Ambit's drug candidate quizartinib, which is in late-stage trials for the treatment of acute myeloid leukemia, as the primary reason for the purchase.

The offer of $15 a share represents an 83% premium to Ambit's Friday closing price of $8.20.

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Ambit, which does not currently have any drugs on the market, will merge with one of Daiichi Sankyo's units after a tender offer. The companies announced more than 50% of all Ambit shares must be tendered.

"Quizartinib will fit seamlessly into our already robust oncology pipeline focused on targeted therapies with the potential for personalizing the treatment of cancer," Daiichi Sankyo executive Mahmoud Ghazzi said.

The stock hit a high of $15.45 on Monday. More than 2.37 million shares had changed hands as of 2:35 p.m., which dwarfed the average volume of 60,916.

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