MEMPHIS, Tenn. (AP) — Shares of biotechnology company GTx Inc. plunged in premarket trading Monday after the company said the Food and Drug Administration wants additional late-stage study data on the company's bone drug candidate toremifene in order to consider approval. The drug is aimed at preventing bone fractures in men who are being treated for prostate cancer by undergoing androgen deprivation therapy. GTx is seeking approval for an 80-milligram dose of the drug. In a statement, GTx said the FDA identified two deficiencies in the company's application. It now wants results from a second late-stage study, along with additional information. GTx said it is requesting a meeting with the FDA to determine the appropriate next steps. An estimated 186,000 new cases of prostate cancer were diagnosed in 2008, and GTx said 100,000 men start androgen deprivation treatment each year. The treatment tends to weaken bones. Shares of GTx plunged $2.98, or 33 percent, to $6 in premarket trading. They closed Friday at $8.98.