SOMERVILLE, MASS. — BioMed Realty, a San Diego-based subsidiary of Blackstone, has topped out Phase I of Assembly Innovation Park, a project in the Boston suburb of Somerville that will add 497,000 square feet of life sciences and office space to the local supply. The development will ultimately consist of three buildings and include retail space and open green space. Perkins & Will designed Assembly Innovation Park, and John Moriarty & Associates is serving as the general contractor. Vertical construction on the $514 million first phase began in August of last year, and full completion is scheduled for next year.