Ariad Pharmaceuticals inc. of Cambridge said the pivotal Phase 3 safety and efficacy trial of ridaforolimus, its drug candidate for metastatic soft-tissue or bone sarcomas, met its primary endpoint. Ridaforolimus met the trial’s goal with a 28 percent reduction in the risk of progression compared to placebo, which is statistically significant, the company said. The trial was conducted at more than 100 medical centers worldwide on 711 patients aged 13 and older. Sarcomas that have spread in the body typically are treated with repeated, sequential rounds of chemotherapy. Ridaforolimus is a small-molecule inhibitor of mTOR, a protein that regulates protein synthesis, cell proliferation, cell cycle progression and cell survival, integrating signals from proteins known to be important to malignancy. The aim of the drug candidate is to extend the time between chemotherapy doses. “This is an unmet medical need. The trial shows the difficulty of getting a beneficial effect from chemotherapy. no new drug has been approved in the U.S. for sarcomas in more than 20 years,” said Harvey Berger, Ariad’s chairman and CEO. The trial remains active, with study participants being followed to get additional data including overall survival. Berger said partner Merck plans to file for marketing approval of oral ridaforolimus in 2011, subject to final collection and analysis of all available data from the trial. The data will be presented at a scientific meeting probably mid-year, Berger said. Sarcomas are a group of connective tissue cancers for which there are only limited treatments. They can arise anywhere in the body, including muscles, fat and bone. Incidence rates of sarcomas have stayed relatively constant over the past 30 years, according to the National Cancer Institute’s website, with about 10,660 Americans diagnosed with soft-tissue and 2,570 with bone sarcoma in 2009. of those, about 3,680 and 1,470, respectively, will die of the diseases. Soft-tissue sarcoma is more deadly because of a lack of detectable symptoms early in the disease. In a research report issued today, J.P. Morgan said the trial results were “a positive surprise as investor expectations were relatively low given that sarcoma is a tough-to-treat heterogeneous disease.” The report also said the positive results will extend to other types of tumors. Ariad in October released results of a Phase 2 study of the drug candidate in endometrial cancer showing a statistically significant improvement in progression-free survival. “Merck is running trials in a variety of solid tumors,” Berger said. “The endometrial trial was stopped earlier because of the favorable effect with ridaforolimus, which doubled the progression-free survival. Merck is currently evaluating the next steps and the design of a pivotal Phase 3 trial.” he added that Merck also is conducting Phase 2 trials on non small cell lung cancer and breast cancer.