By David Russell, reporter at OptionMonsterNEW YORK -- Medivation ( MDVN) has already made a big move but the bulls are looking for more. Back on May 29, OptionMonster's trade scanners detected buying in the July 50 calls for $3.50. The investor rolled a long position in those contracts Monday, selling 2,250 contracts for $5.25 and buying an equal number of August 55 calls for $5.85. Calls lock in the price where shares can be purchased in the drug developer, letting investors cheaply position for a move higher. Adjusting the trade cost 60 cents and gave him or her an additional month of upside exposure. The stock jumped 5.77% to $52.04 Monday and is up 11% in the last week. It rose more than 400% between November 2011 and October 2012 but has been drifting mostly sideways since then. The recent activity suggests that further gains are expected soon. Calls accounted for more than 70% of volume, so the session's overall tone was definitely bullish. More than 8,000 contracts traded Monday, compared with the daily average of 1,200. Russell has no positions in MDVN.