Mersana Therapeutics Reports Phase I Results for XMT-1001 in Patients with Solid Tumors at AACR-NCI-EORTC International Conference

Mersana Therapeutics Reports Phase I Results for XMT-1001 in Patients with Solid Tumors at AACR-NCI-EORTC International Conference

October 24, 2007

- favorable pharmacokinetic and safety data observed in
first clinical trial of novel Fleximer(TM) anticancer agent
-


    CAMBRIDGE, Mass., Oct. 24 /Xinhua-PRNewswire/ --
Mersana, a cancer therapeutics company, announced interim
results of a Phase I study of its lead product candidate,
XMT-1001, in patients with advanced solid tumors. The data
was presented by Edward A. Sausville, M.D., Ph.D, Professor
of Medicine and Associate Director for Clinical Research,
University of Maryland Greenebaum Cancer Center in a poster
session on October 23 at the 2007 AACR-NCI-EORTC
International Conference on Molecular Targets and
Therapeutics taking place in San Francisco, CA.  Full text
of the abstract #A146 "A Phase I Study of the Safety,
Tolerability, and Pharmacokinetics of Intravenous XMT-1001
in Patients with Advanced Solid Tumors" can be viewed
online at the AACR website at http://www.aacr.org. XMT-1001
is a polymer-based prodrug of camptothecin (CPT), a
well-characterized topoisomerase I inhibitor with potent
anti-tumor activity.

    Commenting on the data, Robert J. Fram, M.D. Chief
Medical Officer at Mersana, stated:  "The Phase I
results show that, in humans, camptothecin, the active
agent in XMT-1001, is released gradually from the Fleximer
carrier as a pro-drug in a manner that will potentially
avoid common safety problems associated with drugs in this
class.  To date, we've seen no evidence of drug-related
serious adverse events and the study is ongoing."

    Results were presented from 12 patients enrolled in an
ongoing Phase I open-label, dose-escalation trial designed
to determine the safety, tolerability and pharmacokinetic
profile of XMT-1001. To date, XMT-1001 has been well
tolerated in patients and no serious drug related adverse
events have been reported.  Preliminary results demonstrate
a favorable pharmacokinetic profile with low levels of CPT,
both total and free, recovered in urine.  The maximum
tolerated dose (MTD) has not been reached and the study
continues to accrue patients. 

    "Our Fleximer nanotechnology platform is designed
to create proprietary new drugs from existing and novel
pharmaceutical compounds," said Julie Olson, President
and Chief Executive Officer of Mersana.  "We are
pleased to note that in the Phase I study, our proprietary
Fleximer-controlled drug release system achieved results
consistent with our objective of extending the half-life of
the camptothecin analog while avoiding safety concerns. The
favorable pharmacokinetic and safety data are consistent
with results from preclinical studies of XMT-1001,"
she concluded.  

    About XMT-1001

    XMT-1001 is Mersana's most advanced Fleximer(TM)-based
product candidate.  It utilizes a novel, dual release
mechanism to liberate a camptothecin prodrug, which is then
converted within cells into camptothecin, a DNA
topoisomerase I inhibitor.  In preclinical studies,
XMT-1001 was better tolerated and more efficacious than
either camptothecin or irinotecan in models of human
cancer, showing extended plasma half-life and high
concentrations in tumor tissue.

    About Fleximer

    Mersana is transforming oncology product development by
creating new drugs from anti-cancer agents through
application of its Fleximer nanotechnology platform. 
Fleximer is a novel, biodegradable and bio-inert polymer
that can be chemically linked to drugs, including small
chemical entities, peptides and biologics.  Fleximer-based
compounds can be individually designed to improve the
therapeutic performance of drugs by modulating such
properties as circulation time and site of release, while
significantly improving toxicity profiles.  

    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(TM), 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.

    Fleximer is a trademark of Mersana Therapeutics, Inc. 


    For more information, please contact:

     Pete Leone, Chief Operating Officer
     Mersana Therapeutics, Inc.
     Phone: [phone]

     Media:
     Kathryn Morris
     KmorrisPR
     Phone: [phone]
     Email: [e-mail]