Why one trader is selling puts in Ariad

Ariad Pharmaceuticals is trying to break out of its recent range, and one trader is betting on a floor beneath the stock.

optionMONSTER's tracking systems detected the sale of 2,500 August 15 puts in one print for $0.33. This is clearly a new position, as open interest in the strike was a mere 38 contracts before the trade appeared.

The put seller is looking for ARIA to stay above the $15 strike price through mid-August. If it falls below that level, the trader will be on the hook to buy shares at an effective price of $14.67 once the $0.33 credit from the put sale is included. (See our Education section)

ARIA rose 5.13 percent to close at $18.43 yesterday, just above its 50-day moving average, after hitting a two-month high of $19.64 in the morning. The stock was above $22 in mid-March but fell sharply in the next several sessions and has been trading sideways since.

RBC Capital reiterated its "outperform" rating and $36 price target on Ariad yesterday. Total option volume in the name surpassed 11,700 contracts in the session, more than 11 times its daily average for the last month.

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