RXi Pharmaceuticals (NASDAQ: RXII), the Worcester, MA-based developer of RNA interference therapies, said today it has agreed to acquire Scottsdale, AZ-based Apthera, a developer of peptide immunotherapies for cancer. Apthera shareholders will get 4.8 million shares of RXi under the deal, plus future considerations based on how Apthera’s NeuVax performs. RXi’s shares were valued at $1.50 before the announcement, meaning 4.8 million shares are worth about $7.2 million. As part of the deal, RXi CEO Noah Beerman is resigning, and being replaced as CEO by Mark Ahn, a member of RXi’s board. The NeuVax program will now become RXi’s most advanced in development, as it is being prepared to enter Phase III clinical trials in 2012.