Alnylam Pharmaceuticals signed a lease for 45,000 square feet of office space at 300 Third St. in Cambridge, MA. Built in 2001, the four-story, Class-A office building consists of 131,547 square feet. The previous tenant, Palm Inc., terminated its lease for Alnylam to have a direct deal. Alnylam specializes in the cutting-edge field of RNA therapeutics.