Options traders who opened bullish positions in Gilead Sciences Inc. (GILD - Get Report) Tuesday afternoon were posting large gains by Wednesday morning on positive clinical-trial news.

Just on Tuesday, September 11, Investitute's proprietary programs identified the purchase of 2,400 September $73.50 calls for $0.48 to $0.50 with shares at $72.21. These were clearly new positions, as open interest in the strike was only 320 contracts before the activity appeared.

These call buyers may have expected positive, bullish news in the coming weeks, on the belief that the pipeline for GILD is broad with a multitude of opportunities to serve as catalysts.

Those calls sold for as much as $1.73 Wednesday morning. September 12, more than tripling in value overnight. The stock 3.82% at the same time, illustrating the kind of leverage that can be achieved quickly with options.

Long calls lock in the price where a stock can be purchased, gaining with a rally and providing leverage to the underlying shares. The contracts can quickly lose value if the stock stalls or pulls back but also carry less risk than owning the shares themselves.

Gilead rose 2.41% to $73.97 Wednesday. The pharmaceutical giant and Galapagos NV jointly announced Tuesday night, after the calls were purchased, that their proposed treatment for rheumatoid arthritis had achieved its primary goals in a Phase III study.