STEVENSON, Md.--(BUSINESS WIRE)--The securities litigation law firm of Brower Piven, A Professional Corporation, announces that a class action lawsuit has been commenced in the United States District Court for the District of Maryland on behalf of purchasers of Northwest Biotherapeutics, Inc. (NasdaqCM:NWBO) (“Northwest Biotherapeutics” or the “Company”) securities during the period between March 8, 2013 and August 20, 2015, inclusive (the “Class Period”). Investors who wish to become proactive