As it seeks extra space for its downtown Washington, D.C., office, Brownstein Hyatt Farber Schreck is suing Simpson Thacher & Bartlett, its landlord, and the arbitration company JAMS Inc., a new tenant, over a subleased part of its building at 1155 F St. NW.

Brownstein has subleased about a floor and a half from Simpson Thacher since April 2015, according to a breach of contract complaint and other filings in D.C. Superior Court last week.