Conjugation Technology Advancements Further Demonstrate Stability, Activity and Selectivity of Mersana’s ADCs

Mersana Therapeutics, Inc., a biopharmaceutical company developing its Fleximer® antibody-drug conjugate (ADC) platform and pipeline of small molecule Fleximer conjugates, announced today that new data related to its conjugation technology used to create next-generation ADCs is being presented in a poster session at the 2013 Annual Meeting of the American Association for Cancer Research (AACR). AACR is being held April 6-10, 2013 in Washington, D.C. The preclinical data being presented confirms that Mersana’s technology generates cysteine-conjugated ADCs that are stable, highly active and selective in Her-2 expressing tumor models.

In the poster, Mersana details that its technology, which has previously been applied to create lysine-based ADCs, can also be expanded to create cysteine-based ADCs. The data show that conjugation of Mersana’s Fleximer polymer via cysteines in the antibody hinge region overcomes the destabilization of the antibody which has been reported with conventional, direct drug-cysteine linked ADCs. The stabilization with the Fleximer conjugation approach enhances the advantages of Mersana’s polymer approach to ADCs, which include significantly higher capacity for drug payload, superior payload flexibility and improved physicochemical properties. In this research, the benefits were shown in Her-2 expressing cell lines and preclinical models.

"Mersana has previously demonstrated that our Fleximer-based ADCs that utilize lysine modification are highly efficacious," said Timothy B. Lowinger, Chief Scientific Officer of Mersana. "These data demonstrate that the scope of our conjugation technology can also be expanded to create novel, highly stable cysteine-based ADCs that are highly active, selective and well-tolerated in preclinical tumor models."

"Research into how we can expand our technology is part of our commitment to creating truly next-generation ADCs that have the potential to address limitations of other technologies," said Nicholas Bacopoulos, Ph.D., President and Chief Executive Officer of Mersana. "These types of technological advancements will be utilized as we build our proprietary pipeline of ADC candidates and forge collaborations."

Details of the poster presentation are provided below.

Abstract #4331

Title: Advantages of polyacetal polymer-based antibody drug conjugates employing cysteine bioconjugation

Authors: Alex Yurkovetskiy, Natalya Bodyak, Mao Yin, Josh Thomas, Patrick Conlon, Cheri Stevenson, Alex Uttard, LiuLiang Qin, Dmitry Gumerov, Elena Ter-Ovanesyan, Michael DeVit, Timothy B. Lowinger

Session: Experimental and Molecular Therapeutics 28

Date/Time: Tuesday, April 9, 2013, 1:00 p.m. to 5:00 p.m.

Location: Hall A-C, Poster Section 36, Washington Convention Center

About Mersana

Mersana engineers novel drug conjugates that maximize the potential of new and established therapeutic classes. Utilizing its proprietary conjugation technology, which is comprised of the Fleximer® polymer and a broad array of customizable linker chemistries, Mersana is developing its next-generation antibody-drug conjugate (ADC) platform with superior properties not found with other ADC technologies. Mersana is currently working with a number of top Pharma companies to develop next generation Fleximer-ADCs and most recently announced a $270 million collaboration with Endo Pharmaceuticals in March, 2012. The company is also advancing its own pipeline of next-generation drugs with best-in-class potential to address unmet needs and improve patient outcomes in multiple oncology indications. Mersana’s investors include New Enterprise Associates (NEA), Pfizer Venture Investments, Proquest Investments, Fidelity Biosciences, Rho Ventures and Harris and Harris Group. Mersana was founded by PureTech Ventures, LLC and a group of leading academics and clinicians.
 For more information, visit www.mersana.com.

Fleximer® is a trademark of Mersana Therapeutics, Inc.

Media Contacts:

 MacDougall Biomedical Communications
 Kari Watson
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 kwatson@macbiocom.com