H3 Biomedicine Inc., a biopharmaceutical company specializing in the discovery and development of oncology treatments, said that it has completed an expansion that more than doubles the size of its headquarters and laboratory facilities in Cambridge.

The company, which had 29 employees in 2011, said in a press release that it expects to end 2013 with 75 employees. The company’s headquarters and lab space now occupy about 48,000 square feet of space.