RXi Pharmaceuticals Corporation (Nasdaq: RXII) shares gained 12% to $1.12 Monday, after favorable news about the company’s breast cancer vaccine trial. Volume for the stock exceeded 3.5 million shares, compared to a daily average of 722,000.

A story published Monday in Boston Business Journal revealed that the U.S. Food and Drug administration has cleared the way for the start of Rxi to launch its Phase 3 trial studying a potential vaccine for a certain type of breast cancer.

If successful, the vaccine would provide an alternative for women who have low to intermediate expression of the HER2 mutation, and are not eligible for the blockbuster drug Herceptin, made by Swiss drug maker Roche AG.

The FDA has now lifted a partial clinical hold the agency put on the chemistry, manufacturing and controls associated with the vaccine trial.

Worcester, Mass.-based RXi acquired the potential vaccine, called NeuVax, when it bought Scottsdale, Ariz.-based Apthera. As part of the deal, Apthera’s shareholders initially received approximately 4.8 million shares of Worcester, Mass.-based RXi’s common stock, worth $7.2 million at the time, on March 30. The deal closed in April. Apthera’s stockholders will also be entitled to contingent payments tied to clinical, regulatory and commercial milestones connected to NeuVax.

The partial clinical hold was placed on the vaccine candidate before it was acquired by RXi, and its lifting will allow the company to start its Phase 3 trial in the first half of 2012. The study is expected to include about 100 trial sties in the U.S., Canada and Europe.