GTx Inc. said results from a Phase III study of its investigational drug Acapodene (toremifene citrate, 80 mg), showed that it works to reduce spinal fractures and other side effects from androgen deprivation therapy, a common treatment for prostate cancer.
Full data will be presented at a future medical meeting, but news that it had met its primary and other key endpoints sent GTx shares up 36.5 percent.
The Memphis, Tenn.-based company has said it plans to file a new drug application with the FDA in the summer, GTx spokesman McDavid Stilwell said. Its partner, Paris-based Ipsen SA, which has rights to license the drug in Europe, said it plans to file for the same indication in the European Union before year-end 2008.
In the study, patients treated with Acapodene 80 mg saw a 50 percent reduction in spinal fractures, compared with a 5 percent fracture rate in the placebo group, according to GTx. The drug also was shown to increase bone mineral density and improve gynecomastia, abnormal enlargement of breasts in males.
Currently, there are no drugs to treat multiple side effects of androgen deprivation therapy (ADT), which is used in about 800,000 men, the company said.
ADT is a hormone therapy, such as leuprolide and triptorelin injections. It works by reducing testosterone and estrogen, and can result in multiple estrogen-related side effects, such as bone loss and fractures, hot flashes, lipid changes, increased cardiovascular risk and gynecomastia, GTx said.
Data showing the effect of Acapodene 80 mg on hot flashes still is being evaluated and will be reviewed with the final data set, the company said.
The number of blood clot events, which included deep vein clots and pulmonary embolism, were higher in the Acapodene-treated group (17, or 2.4 percent) compared to the placebo group (seven, or 1.02 percent), GTx said. Most of the events occurred in men at high risk for a venous thromboembolism (VTE), including men older than 80, with a history of VTE, recent surgical procedure and immobilization.
In men without major risk factors for VTE, there were three such events in the Acapodene group and two in the placebo group. The most significant VTE risk occurred in the first year of treatment. In year two, the VTE event rate in the Acapodene-treated group was similar to the rate observed in the placebo group, GTx said.
Acapodene is a in a drug class known as selective estrogen receptor modulators, or SERMs. It is being studied in two separate clinical programs in men. The first pivotal Phase III clinical trial evaluates the 80-mg dose for the treatment of serious side effects of androgen deprivation therapy for advanced prostate cancer.
The second pivotal Phase III clinical trial evaluates Acapodene 20 mg for the prevention of prostate cancer in high-risk men with high-grade prostatic intraepithelial neoplasia (precancerous lesions), or PIN.
GTx licensed from Orion Corp., of Espoo, Finland, the rights to toremifene citrate for all indications worldwide, except breast cancer outside the U.S. The company has entered into a development and collaboration agreement with Ipsen Group for toremifene citrate in all indications except breast cancer for Europe and a group of former Soviet countries called the Commonwealth of Independent States (CIS).
Ipsen is the leading marketer of ADT (triptorelin) in Europe. Under the agreement, Ipsen is responsible for filing for marketing approval with regulatory authorities and commercializing toremifene citrate in Europe and CIS. GTx will file for marketing approval and plans to commercialize toremifene citrate 80 mg in the U.S.
GTx also is collaborating with Merck & Co. Inc., of Whitehouse Station, N.J., for development and global commercialization of selective androgen-receptor modulators, or SARMs, a new class of drugs with the potential to treat a variety of indications associated with muscle wasting and bone loss. GTx also is developing preclinical compounds, GTx-758, an oral LH inhibitor for advanced prostate cancer, and GTx-878, an estrogen receptor beta agonist for the treatment of benign prostatic hyperplasia and chronic prostatitis.
Shares of GTx (NASDAQ:GTXI) reached a high of $20 in opening trading Monday before closing at $17.59, up $4.70 or 36.5 percent.