Cambridge, MA
January 3, 2008

Mersana, a cancer therapeutics company, announced today the appointment of C. Boyd Clarke as Chairman of the Company’s Board of Directors. Mr. Clarke is a senior biotechnology and pharmaceutical executive with a significant record of accomplishment over a 30-year industry career.

“It is a great pleasure to welcome Boyd Clarke as Chairman of our Board of Directors,” said Julie A. Olson, PhD, President and Chief Executive Officer at Mersana. “Boyd brings diverse management experience and commercial expertise in areas important to Mersana at our stage of development. His skills complement those of our existing team very well, and we anticipate his strategic leadership will be of considerable value as we advance our pipeline.”

Over the past 11 years Mr. Clarke has held the role of Chairman and Chief Executive Officer at several publicly-held biotechnology companies, most recently Neose Technologies. During his four year tenure at Neose, Mr. Clarke led the company from a platform-based discovery operation to a clinical stage development company with multiple product candidates. As President and CEO of Aviron he oversaw the Biological Licensing Application (BLA) submission for the company’s lead product and ultimately secured the sale of the vaccine company to MedImmune. He also served as President and CEO of US Bioscience. Mr. Clarke began his pharmaceutical career at Merck, where he held a series of increasingly responsible positions, including President of Pasteur Merieux MSD and Vice President of Merck Vaccines. He holds a Bachelor of Science degree and a Master of Arts degree from the University of Calgary. Mr. Clarke serves on the Board of Directors of QLT, Inc. and Rib-X, and is a past board member of the Biotechnology Industry Association (BIO).

“ Mersana’s Fleximer® technology has the potential to create safer and more efficacious cancer drugs, and the promise of the technology is now being demonstrated in their ongoing clinical studies,” stated Boyd Clarke. “I’m excited by the Company’s prospects and am looking forward to participating in their continued growth as Chairman.”

About Mersana Therapeutics, Inc.
Mersana, a privately held, venture backed company, utilizes its proprietary nanotechnology platform to transform existing and experimental anti-cancer agents into new, patentable drugs with superior pharmaceutical properties. The key component of Mersana’s platform is Fleximer®, a novel, biodegradable and bio-inert material that can be chemically linked to small molecules and biologics. Mersana’s pipeline includes XMT-1001, a Fleximer-camptothecin conjugate, which is currently in Phase 1 clinical trials and several preclinical stage oncology compounds. Mersana’s investors include Fidelity Biosciences, ProQuest Investments, Rho Ventures, Harris & Harris Group and PureTech Ventures.