CARLSBAD, Calif. and CAMBRIDGE, Mass., Oct. 9 /PRNewswire-FirstCall/ --
The Immune Response Corporation (Nasdaq: IMNR) and Hybridon, Inc.
(OTC Bulletin Board: HYBN) today announced that they have entered into a
license agreement for the use of AMPLIVAX(TM) as an adjuvant in the
development of a novel vaccine candidate for the prevention and treatment of
HIV, the virus that causes AIDS.  The new vaccine candidate, which has already
demonstrated activity in laboratory experiments, combines the whole-killed
vaccine technology employed in REMUNE(R), an immune-based HIV therapeutic
vaccine being evaluated in Phase II clinical trials by The Immune Response
Corporation, plus AMPLIVAX, Hybridon's 2nd generation immunomodulatory
oligonucleotide (IMO(TM)) adjuvant designed to enhance the immune response to
a vaccine antigen.  The Immune Response Corporation separately will continue
its clinical development of REMUNE as a potential treatment for patients
already infected with the HIV virus.
    "As The Immune Response Corporation presses forward with the clinical
development of REMUNE, we intend to expand our efforts in the HIV area by
beginning development of the new vaccine candidate for broader prophylactic
and therapeutic applications," said John Bonfiglio, Ph.D., CEO of The Immune
Response Corporation.  "In preclinical data generated to date, the use of
REMUNE plus AMPLIVAX has elicited a significantly enhanced HIV-1 specific
T-cell response, indicating the potential for the combined agents to function
as a novel HIV vaccine.  We are currently completing a number of preclinical
studies and plan to move this project into clinical development quickly.  The
fact that REMUNE has a history of being evaluated in human trials and that
AMPLIVAX has been studied in humans for other uses should facilitate the
clinical development of the combined product candidate."
    "We are very pleased to work with The Immune Response Corporation on the
development of a novel HIV vaccine candidate using our AMPLIVAX adjuvant,"
added Stephen R. Seiler, CEO of Hybridon, Inc.  "AMPLIVAX has shown
encouraging pre-clinical results as an adjuvant with a broad range of vaccines
targeted to multiple disease indications."
    AMPLIVAX is presently known as HYB2055.  HYB2055 is currently in two Phase
I clinical trials.  Adjuvant applications of HYB2055 will be referred to as
AMPLIVAX.

    About The Immune Response Corporation and REMUNE(R)
    The Immune Response Corporation is a biopharmaceutical company dedicated
to treating and preventing HIV and AIDS through the development of
immune-based therapeutic vaccines such as REMUNE, its lead product candidate.
The Company was co-founded by medical pioneer Dr. Jonas Salk, who was
instrumental in the formulation of REMUNE, which is currently in Phase II
clinical development.
    HIV, the human immunodeficiency virus, is the virus that causes AIDS, a
condition that slowly destroys the body's immune system, making it vulnerable
to infections.  REMUNE is designed to induce a specific immune response to the
HIV virus.  It is comprised of HIV-1 virus that has been chemically killed and
inactivated so that it is non-infectious, plus an adjuvant that helps enhance
the body's immune response to the virus.  More than 60 million people have
been infected with HIV since it was first recognized in 1981, and
approximately 40 million people around the world are living with HIV today.

    This news release contains forward-looking statements.  Actual results
could vary materially from those expected due to a variety of risk factors,
including whether the new vaccine candidate will be effective for the
prevention or treatment of HIV or whether it will enter into clinical trials,
whether The Immune Response Corporation will continue as a going concern and
successfully raise proceeds from financing activities sufficient to fund
operations and additional clinical trials of REMUNE, the uncertainty of
successful completion of any such clinical trials, whether REMUNE will be
effective as either a preventive or therapeutic vaccine, whether future trials
will be conducted and whether the results of such trials will coincide with
the results of REMUNE in preclinical trials.  These risks, among others, are
set forth in The Immune Response Corporation's SEC filings including, but not
limited to, its Annual Report on Form 10-K for the year ended December 31,
2002, and subsequent Quarterly Reports on Form 10-Q.  The Immune Response
Corporation undertakes no obligation to publicly release the results of any
revisions to these forward-looking statements, which may be made to reflect
events or circumstances after the date hereof or to reflect the occurrence of
unanticipated events.
    REMUNE(R) is a registered trademark of The Immune Response Corporation.

    About Hybridon
    Hybridon, Inc. is a leader in the discovery and development of novel
therapeutics and diagnostics, based on synthetic DNA.  The Company now has
four technology platforms: 1) Synthetic immunomodulatory oligonucleotide
(IMO(TM)) motifs that act to modulate responses of the immune system; 2)
Antisense technology which uses synthetic DNA to block the production of
disease-causing proteins at the cellular level; 3) Synthetic DNA drug
candidates that enhance the antitumor activity of certain marketed anticancer
drugs, thereby increasing their effectiveness; and 4) novel synthetic DNA
structures for identifying gene function, which can be used for target
validation and drug discovery as well as for PCR-based gene amplification.

    This press release contains forward-looking statements concerning Hybridon
that involve a number of risks and uncertainties.  For this purpose, any
statements contained herein that are not statements of historical fact may be
deemed to be forward-looking statements.  Without limiting the foregoing, the
words, "believes," "anticipates," "plans," "expects," "estimates," "intends,"
"should," "could," "will," "may," and similar expressions are intended to
identify forward-looking statements.  There are a number of important factors
that could cause Hybridon's actual results to differ materially from those
indicated by such forward-looking statements including risks as to whether
results obtained in preclinical studies or early clinical trials will be
indicative of results obtained in future preclinical studies or clinical
trials, or warrant further clinical trials and product development; whether
products based on Hybridon's technology will advance through the clinical
trial process and receive approval from the United States Food and Drug
Administration or equivalent foreign regulatory agencies; whether, if such
products receive approval, they will be successfully distributed and marketed;
whether the patent and patent applications owned or licensed by Hybridon will
protect the company's technology and prevent others from infringing it;
whether Hybridon's cash resources will be sufficient to fund product
development and such other important factors as are set forth under the
caption "Risk Factors" in Hybridon's Quarterly Report on Form 10-Q for the
quarter ended June 30, 2003, which important factors are incorporated herein
by reference.  Hybridon disclaims any intention or obligation to update any
forward-looking statements.

    Hybridon's IMO Technology
    Hybridon's IMO(TM) technology comprises a portfolio of compounds that
mimic bacterial DNA that activate the human immune system to fight diseases.
Independent reports have shown that CpG oligonucleotides are useful in the
treatment of cancer, infectious diseases and asthma/allergies, either alone or
in combination with antigens, antibodies or conventional therapies.
    AMPLIVAX and IMO are trademarks of Hybridon, Inc.

                   For further information please contact:

                       The Immune Response Corporation
          (Investors) - Kathy Lane, (760) 771-2236 or info@imnr.com
 (Media) - Gwen Rosenberg, Rosenberg Business Communications, (858) 759-0759

                                Hybridon, Inc.
        (Investors) - Robert G. Andersen, (617) 679-5500, ext. 5517 or
                            randersen@hybridon.com
       (Media) Robert Stanislaro, Noonan Russo Presence, (212) 845 4268

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