Alexandria Real Estate Equities, the California-based life science property developer, announced an agreement to sell 268,000 square feet at 421 Park Drive, a 660,034-square-foot life science development in Boston's Fenway neighborhood, to an affiliate of Boston Children's Hospital. The price for the portion sold to Boston Children’s Hospital is approximately $155 million. The life science real estate investment trust said it also stands to earn development fees under the deal over the next three years.