Our Leadership

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Robert J. Mulroy President & Chief Executive Officer

Fazal R. Khan, Ph.D. Senior Vice President of Manufacturing

William M. McClements Senior Vice President of Corporate Operations

Ulrik B. Nielsen, Ph.D. Senior Vice President & Chief Scientific Officer

Clet Niyikiza, Ph.D. Executive Vice President of Development

Edward J. Stewart Senior Vice President & President, Merrimack Healthcare Solutions

William A. Sullivan Chief Financial Officer & Treasurer


Robert J. Mulroy has served as our President and Chief Executive Officer and a member of our board of directors since May 1999. Prior to joining us, Mr. Mulroy worked as a management consultant in the pharmaceutical and healthcare industries. Mr. Mulroy has also worked as a consultant in the field of international development and has served as an advisor to multiple start-up companies in the biotechnology industry. Mr. Mulroy holds a master’s degree in public and private management from Yale University and a B.A. from Stanford University.

Fazal R. Khan, Ph.D. has served as our Senior Vice President of Manufacturing since April 2006. Prior to joining us, Dr. Khan served as Vice President of Manufacturing for Cellective Therapeutics, Inc., Vice President of Manufacturing Operations at Human Genome Sciences and Director of Biopharmaceuticals Development and Manufacturing at Hoffmann-LaRoche, Inc. Dr. Khan holds a Ph.D. and an M.S. in biochemistry and a B.S. from Aligarh University in India. 

William M. McClements has served as our Senior Vice President of Corporate Operations since September 2011. Previously, Mr. McClements served as Chief Human Resources Officer of Integreon Managed Solutions, Inc., a global research and business services company, from May 2010 to September 2011. Prior to that, Mr. McClements served as Chief Operating Officer and a partner at Monitor Group, a global strategic advisory firm, where he worked from 1987 to May 2010. From September 2009 to March 2010, Mr. McClements also served as Acting President of Be the Change Inc., a non-profit focused on creating national issue-based campaigns. Mr. McClements holds an M.B.A. from Harvard Business School and a B.A. from Williams College.

Ulrik B. Nielsen, Ph.D. has served as our Senior Vice President and Chief Scientific Officer since March 2009. Dr. Nielsen has also served as Chief Executive Officer and as a member of the board of directors of Silver Creek Pharmaceuticals, Inc. since July 2010. Dr. Nielsen was one of our co-founders and has been leading our research and drug discovery since March 2002, first as our Director of Research from March 2002 to December 2004 and then as our Vice President of Research from January 2005 to February 2009. Prior to joining us, Dr. Nielsen was a post-doctoral fellow at The Massachusetts Institute of Technology, where he researched the interface among biology, engineering and computational biology. Dr. Nielsen holds a Ph.D. in molecular biology and an M.S. in biochemistry from the University of Copenhagen.  

Clet Niyikiza, Ph.D. has served as our Executive Vice President of Development since February 2010. Dr. Niyikiza served as our Senior Vice President of Product Development from July 2009 to February 2010. Previously, Dr. Niyikiza served as Vice President and Medicine Development Leader at GlaxoSmithKline, overseeing product development and global anti-cancer medicine development strategy, from 2005 to July 2009. Prior to that, Dr. Niyikiza held multiple high level positions at Eli Lilly and Company, where he ultimately led the oncology translational and applied genomics research division. Dr. Niyikiza holds a Ph.D. in mathematical sciences and an M.A. in mathematics from Indiana University. 

Edward J. Stewart has served as our Senior Vice President and President, Merrimack Healthcare Solutions since December 2011. Mr. Stewart served as our Director of Business Development from August 2001 to July 2006, as our Senior Director of Business Development from August 2006 to July 2007, as our Vice President of Business Development from July 2007 to March 2009 and as our Senior Vice President of Business Development from March 2009 to December 2011. Mr. Stewart began his career at KPMG Peat Marwick LLP in the life sciences strategy consulting group. Mr. Stewart holds an M.B.A. from the Johnson Graduate School of Management at Cornell University and a B.S. from Bates College. 

William A. Sullivan has served as our Chief Financial Officer since May 2011 and our Treasurer since February 2010. Mr. Sullivan served as our Controller from November 2007 to February 2010 and our Vice President of Finance from February 2010 to May 2011. Previously, Mr. Sullivan served as Corporate Controller of Vette Corp., a thermal management solutions company, from October 2004 to November 2007. Mr. Sullivan began his career at Arthur Andersen LLP, where he obtained his certified public accountant license. Mr. Sullivan holds an M.B.A. and an M.S. in accounting from Northeastern University’s Graduate School of Professional Accounting and a B.A. from Williams College.