CytomX Announces Global Strategic Collaboration with Pfizer to Develop and Commercialize Multiple Probody™-Drug Conjugates in

  CytomX Announces Global Strategic Collaboration with Pfizer to Develop and
  Commercialize Multiple Probody™-Drug Conjugates in Oncology

  CytomX Eligible to Receive Approximately $25 Million in Upfront, Research
 Reimbursement and Preclinical Milestone Payments, $610 Million in Regulatory
             and Sales Milestones, Plus Tiered Royalties on Sales

Business Wire

SOUTH SAN FRANCISCO, Calif. -- June 6, 2013

CytomX Therapeutics, Inc., a biotechnology company developing a new generation
of targeted antibody therapeutics, today announced that it has entered into a
global strategic collaboration with Pfizer Inc. to develop and commercialize
multiple Probody™-Drug Conjugates (PDCs). CytomX’s novel Probody Platform
brings to the collaboration a proprietary, highly differentiated approach to
developing safer and more effective antibody-drug conjugates (ADCs). PDCs are
engineered to combine cytotoxic agents with masked Probodies that remain inert
in healthy tissue but are activated specifically in the tumor
microenvironment, opening up new target space for this emerging therapeutic
class.

“Combining our novel Probody Platform with Pfizer’s broad capabilities in ADCs
marks an important milestone for CytomX and underscores the potential of our
Probody Platform to enable new generations of empowered antibodies,” said Sean
McCarthy, D.Phil., chief executive officer of CytomX. “Our innovative science
is driving the development of groundbreaking Probodies and PDCs that have
already demonstrated preclinical activity when selectively activated within
the tumor microenvironment. We look forward to collaborating with Pfizer with
the aim of researching and developing highly differentiated PDC products that
have the potential to change the way cancer is treated.”

Under the terms of the agreement, Pfizer has exclusive rights to pursue
development and commercialization of select PDCs. The companies will work
together on preclinical research and Pfizer will be responsible for
development and potential commercialization of any selected PDCs. CytomX will
be eligible to receive up-front, research reimbursement and preclinical
milestone payments totaling approximately $25 million and approximately $610
million in regulatory and sales milestone payments, as well as tiered
royalties reaching double digits on potential future sales.

“This partnership is a great example of how Pfizer is seeking to innovate new
capabilities in cutting-edge science and technology platforms with the aim of
delivering safer, more effective cancer medicines to patients,” said Robert T.
Abraham, senior vice president and chief scientific officer, Pfizer’s Oncology
Research Unit. “Pfizer’s investment in CytomX’s emerging Probody Platform is
an important component of our overall strategic focus to advancing the next
generation of ADCs and reflects the disruptive potential of this approach.”

About The CytomX Probody™ Platform

CytomX’s novel Probody™ Platform is enabling the development of a diversified
pipeline of next generation empowered antibodies, including Probodies,
Probody-Drug Conjugates (PDCs), bispecifics, and other formats, to address
previously undruggable targets in cancer, inflammation, and other significant
unmet medical needs. Probodies have the potential to expand the therapeutic
window for targets where therapeutic intervention is expected to have a
significant impact on the disease, but also where normal tissue expression
patterns are too widespread to allow for adequate safety margins using
conventional antibody approaches. CytomX’s Probodies are fully recombinant
masked antibodies that remain inert in healthy tissue but are activated
specifically in the disease microenvironment. Probodies leverage dysregulated
protease activity, a hallmark of many diseased states, to locally activate in
the disease tissue thereby achieving unprecedented levels of tissue-specific
targeting.

About CytomX

CytomX Therapeutics is a biotechnology company developing the next generation
of highly targeted antibody therapeutics. The company’s vision is to transform
lives with safer, more effective therapies. CytomX’s Probody™ Platform
represents a disruptive approach to discovering and developing empowered
antibodies and is enabling the development of a diversified pipeline
addressing previously undruggable targets in major unmet medical needs
including cancer and inflammation. Probodies are masked antibodies that remain
inert in healthy tissue but are activated specifically in the disease
microenvironment. This improved selectivity allows CytomX to open a
therapeutic window for high potential, but previously inaccessible targets,
and to expand the therapeutic index of existing, validated targets, thereby
redefining the landscape for therapeutic antibodies. CytomX is led by a
seasoned and proven management team and is financed by leading life science
investors including Third Rock Ventures, Canaan Partners and the Roche Venture
Fund. For more information, please visit www.cytomx.com.

Contact:

Pure Communications, Inc.
Kristie Wallis, 336-774-8666
Kristie@purecommunicationsinc.com
 
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