By Jud Pyle, CFA, chief investment strategist for the Options News Network

Chicago (

TheStreet.com

) --

Biogen Idec

(BIIB) - Get Report

shares closed up $1.10 to $51.01 following news that the biotechnology manufacturer offered $14.50 per outstanding share in

Facet Biotech

( FACT) and one investor is expressing cautious optimism using a bull synthetic.

During midday trading, an investor sold 10,000 April 35 puts for around 90 cents to finance a purchase of 5,000 April 55 calls for $3.80 per contract with the stock trading around $50.70. The April 35 puts have dropped 20 cents so far on the day and are home to current open interest of just 11 contracts. The April 55 calls closed up 35 cents and are home to current open interest of 92 contracts. The April 35 puts have a delta of 10 and the April 55 calls have a delta of 44, meaning this bull synthetic trade has a delta of approximately 64.

Mergers and acquisitions activity often displays relative strength in companies. Biogen shares, in particular, are trading 12% higher than its recent low of $49.21 in July. It's interesting that we're seeing moderately bullish option activity in Biogen thanks to at least one investor who is not only long calls in the stock but also selling double the amount of puts.

-- written by Jud Pyle in Chicago. Pyle is the chief investment strategist for Options News Network and the portfolio manager of TheStreet.com Options Alerts. Click here for a free trial for Options Alerts. Mr. Pyle writes regularly about options investing for TheStreet.com.

Jud Pyle, CFA, is the chief investment strategist for Options News Network. Pyle started his career in finance in 1994 as a derivative analyst with SBC Warburg. After four years with Warburg, Pyle joined PEAK6 Investments, L.P., in 1998 as an equity options trader and as chief risk officer. A native of Minneapolis, Pyle received his bachelor's degree in economics and history from Colgate University in 1994. As a trader, Pyle traded on average over 5,000 contracts per day, and over 1.2 million contracts per year. He also built the stock group for all PEAK6 Investments, L.P. hedging, which currently trades on average over 5 million shares per day, and over 1 billion shares per year. Further, from 2004-06, he managed the trading and risk management for PEAK6 Investments L.P.'s lead market-maker operation on the former PCX exchange, which traded more than 10,000 contracts per day. Pyle is the "Mad About Options" resident expert. He is also a regular contributor to "Options Physics."