Cell Therapeutics ( CTIC - Get Report) shares plunged early Monday after the biotech company reported disappointing clinical results for its cancer drug.

The Seattle-based company said a phase III study of its drug Xyotax in combination with carboplatin, known as Stellar 3, missed its primary endpoint in treating patients with nonsmall-cell lung cancer.

Cell Therapeutics had hoped the data would show its treatment was superior to standard chemotherapy.

"We are disappointed that Xyotax in combination with carboplatin showed equal efficacy after the unprecedented blended median and one-year survival we saw on the trial," the company said in a statement. "We are encouraged by the preliminary analysis, which demonstrates a significant Xyotax treatment effect, reduction in toxicities, and increased patient convenience."

In the premarket, shares were trading at $5.11, down $4.89, or almost 50%.