Merck Serono and Opexa Therapeutics Enter into Option and License Agreement for Development of Tcelna™ (imilecleucel-T) for

  Merck Serono and Opexa Therapeutics Enter into Option and License Agreement
  for Development of Tcelna™ (imilecleucel-T) for Treatment of Multiple
  Sclerosis

 Merck Serono granted option for exclusive license from Opexa to develop and
 commercialize Tcelna (imilecleucel-T), an investigational T-cell therapy for
               patients suffering from multiple sclerosis (MS)

Business Wire

THE WOODLANDS, Texas -- February 5, 2013

Opexa Therapeutics, Inc. (NASDAQ: OPXA) today announced the execution of an
agreement with Merck Serono, a division of Merck, Darmstadt, Germany, for the
development and commercialization of Tcelna^™ (imilecleucel-T), a potential
first-in-class personalized T-cell therapy for patients suffering from
multiple sclerosis (MS). Tcelna (imilecleucel-T) is being developed by Opexa
and currently is in a Phase IIb clinical trial in patients with Secondary
Progressive MS (SPMS). Potential payments to Opexa from the option and license
agreement could total $225 million based upon the successful development and
commercialization of Tcelna for MS.

Tcelna (imilecleucel-T) is being developed as a personalized therapy
specifically tailored to each patient’s individual disease profile and has
been evaluated in Phase I and II clinical studies in MS that included SPMS
patients. Tcelna (imilecleucel-T) has received Fast Track Designation from the
United States Food and Drug Administration as a potential treatment for SPMS.

Under the terms of the agreement, Opexa will receive an upfront payment of $5
million for granting an option to Merck Serono for the exclusive license of
the Tcelna (imilecleucel-T) program for the treatment of MS. The option may be
exercised prior to or upon completion of Opexa’s ongoing Phase IIb clinical
trial in patients with SPMS. Upon exercising this licensing option, Merck
Serono would pay an upfront license fee of either $25 million or $15 million
(depending upon whether certain conditions are met), and in return receive
worldwide development and commercial rights to Tcelna (imilecleucel-T) in MS,
excluding Japan. After exercising the option Merck Serono would be wholly
responsible for funding clinical development, subject to Opexa’s co-funding
option, as well as regulatory and commercialization activities for the MS
program. Additional financial considerations of the agreement include
development and commercial milestone payments to Opexa of up to $195 million
and a tiered royalty rate from the high single digits to the mid-teens based
on net sales payable to Opexa. The potential payments to Opexa could,
therefore, total $225 million excluding royalty payments.

Under the agreement, Opexa will have an option right to co-fund development,
under which the Company would participate in economic support for future
clinical development of the program in exchange for additional royalty
consideration. In addition to retaining all rights outside of MS as well as
retaining the ability to commercialize Tcelna (imilecleucel-T) in Japan, Opexa
also retains certain manufacturing rights related to the program. Further
details of the transaction are included in a Form 8-K that was filed this
morning by Opexa with the United States Securities and Exchange Commission.

“Merck Serono is strongly committed to developing innovative drug candidates
like Tcelna (imilecleucel-T), a potential first-in-class personalized  cell
therapy for patients with multiple sclerosis,” said Susan Herbert, Head of
Global Business Development and Strategy at Merck Serono. “This agreement
illustrates Merck Serono’s commitment to employ creative ways of accessing
external innovation to develop potential next generation multiple sclerosis
treatments, especially in secondary progressive multiple sclerosis, an area of
high unmet need.”

Neil K. Warma, President and Chief Executive Officer of Opexa, commented,
“Opexa is pleased to partner with Merck Serono and given Merck Serono’s
long-term strategic commitment to, and existing franchise position in the
field of multiple sclerosis, we could not ask for a more experienced partner
to carry Tcelna (imilecleucel-T) through development and hopefully to the
market and to patients. We also are pleased to retain important rights through
this transaction, such as certain manufacturing rights, commercialization
rights to the Japanese market and a co-funding of development option, as well
as rights for all indications outside of MS, all of which are intended to
enhance Opexa shareholder value.”

Conference Call

The management of Opexa will host a conference call today, Tuesday, February
5, 2013, at 8:30 a.m. EST to discuss the agreement. To participate in the live
conference call, please dial (877) 372-0867 (U.S.) or (253) 237-1170
(International). A live webcast of the call will also be available on the
investor relations section of the Company's website,
www.opexatherapeutics.com. An online archive of the webcast will be available
on Opexa’s website for one year following the call.

About Multiple Sclerosis (MS)

MS is a chronic, inflammatory condition of the central nervous system and is
the most common, non-traumatic, disabling neurological disease in young
adults. It is estimated that approximately two million people have MS
worldwide.

While symptoms can vary, the most common symptoms of MS include blurred
vision, numbness or tingling in the limbs and problems with strength and
coordination. The relapsing forms of MS are the most common.

About Tcelna (imilecleucel-T)

Tcelna (imilecleucel-T) is a potential personalized therapy that is under
development to be specifically tailored to each patient's disease profile.
Tcelna (imilecleucel-T) is manufactured using ImmPath^™, Opexa's proprietary
method for the production of a patient-specific T-cell immunotherapy, which
encompasses the collection of blood from the MS patient, isolation of
peripheral blood mononuclear cells, generation of an autologous pool of
myelin-reactive T-cells (MRTCs) raised against selected peptides from myelin
basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) and proteolipid
protein (PLP), and the return of these expanded, irradiated T-cells back to
the patient. These attenuated T-cells are reintroduced into the patient via
subcutaneous injection to trigger a therapeutic immune system response.

Opexa is currently conducting a Phase IIb study of Tcelna (imilecleucel-T).
Named Abili-T, the trial is a randomized, double-blind, placebo-controlled
clinical study in patients who demonstrate evidence of disease progression
without associated relapses. The trial is expected to enroll 180 patients at
approximately 30 leading clinical sites in the U.S. and Canada with each
patient receiving two annual courses of Tcelna (imilecleucel-T) treatment
consisting of five subcutaneous injections per year. The trial’s primary
efficacy outcome is the percentage of brain volume change (atrophy) at 24
months. Study investigators will also measure several important secondary
outcomes commonly associated with MS, including disease progression as
measured by the Expanded Disability Status Scale (EDSS), annualized relapse
rate and changes in disability as measured by EDSS and the MS Functional
Composite.

About Opexa

Opexa Therapeutics, Inc. (NASDAQ:OPXA) is dedicated to the development of
patient-specific cellular therapies for the treatment of autoimmune diseases
such as MS. The Company’s leading therapy candidate, Tcelna^™
(imilecleucel-T), is a personalized cellular immunotherapy that is in Phase
IIb clinical development for MS. Tcelna (imilecleucel-T) is derived from
T-cells isolated from peripheral blood, expanded ex vivo, and reintroduced
into the patients via subcutaneous injections. This process triggers a potent
immune response against specific subsets of autoreactive T-cells known to
attack myelin.

For more information visit the Opexa Therapeutics website at
www.opexatherapeutics.com

About Merck Serono

Merck Serono is the biopharmaceutical division of Merck. With headquarters in
Darmstadt, Germany, Merck Serono offers leading brands in 150 countries to
help patients with cancer, multiple sclerosis, infertility, endocrine and
metabolic disorders as well as cardiovascular diseases. In the United States
and Canada, EMD Serono operates as a separately incorporated subsidiary of
Merck Serono.

Merck Serono discovers, develops, manufactures and markets prescription
medicines of both chemical and biological origin in specialist indications. We
have an enduring commitment to deliver novel therapies in our core focus areas
of oncology, neurology and immunology.

For more information, please visit www.merckserono.com or www.merckgroup.com

About Merck

Merck is a global pharmaceutical and chemical company with total revenues of
€10.3 billion in 2011, a history that began in 1668, and a future shaped by
approx. 40,000 employees in 67 countries. Its success is characterized by
innovations from entrepreneurial employees. Merck's operating activities come
under the umbrella of Merck KGaA, in which the Merck family holds an
approximately 70% interest and free shareholders own the remaining
approximately 30%. In 1917 the U.S. subsidiary Merck & Co. was expropriated
and has been an independent company ever since.

For more information, please visit www.merckserono.com or www.merckgroup.com

Cautionary Statement Relating to Forward-Looking Information for the Purpose
of "Safe Harbor" Provisions of the Private Securities Litigation Reform Act of
1995

This press release contains forward-looking statements which are made pursuant
to the safe harbor provisions of Section 27A of the Securities Act of 1933, as
amended, and Section 21E of the Securities Exchange Act of 1934, as amended.
The words “expects,” “believes,” “may,” “could,” and similar expressions are
intended to identify forward-looking statements. The forward-looking
statements in this release do not constitute guarantees of future performance.
Investors are cautioned that statements in this press release which are not
strictly historical statements, including, without limitation, statements
regarding the development of the Company’s product candidate, Tcelna
(imilecleucel-T), constitute forward-looking statements. Such forward-looking
statements are subject to a number of risks and uncertainties that could cause
actual results to differ materially from those anticipated, including, without
limitation, risks associated with: the success of our clinical trials
(including the Phase IIb trial for Tcelna (imilecleucel-T) in SPMS which,
depending upon results, may determine whether Merck Serono elects to exercise
its option pursuant to the option and development agreement), whether Merck
Serono exercises its option and, if so, whether the Company receives any
development or commercialization milestone payments or royalties from Merck
Serono pursuant to the option and development agreement, our dependence (if
Merck Serono exercises its option) on the resources and abilities of Merck
Serono for the further development of Tcelna (imilecleucel-T), our ability to
raise additional capital to continue our development programs (including to
undertake and complete any ongoing or further clinical studies for Tcelna
(imilecleucel-T)), the efficacy of Tcelna (imilecleucel-T) for any particular
indication, such as for relapsing remitting MS or secondary progressive MS,
our compliance with all Food and Drug Administration regulations, our ability
to obtain, maintain and protect intellectual property rights (including for
Tcelna), and other risks detailed in our filings with the Securities and
Exchange Commission. These forward-looking statements speak only as of the
date made. We assume no obligation or undertaking to update any
forward-looking statements to reflect any changes in expectations with regard
thereto or any change in events, conditions or circumstances on which any such
statement is based. You should, however, review additional disclosures we make
in our reports filed with the Securities and Exchange Commission, including
our Annual Report on Form 10-K for the year ended December 31, 2011 and our
Quarterly Report on Form 10-Q for the quarter ended September 30, 2012.

Contact:

Opexa Therapeutics, Inc.
Neil K. Warma
281.775.0600
nwarma@opexatherapeutics.com
or
Vida Strategic Partners
Tim Brons
415-675-7400
tbrons@vidasp.com
or
The Trout Group
Adam Cutler
646.378.2936
opexa@troutgroup.com
 
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