October 10, 2003

News Release: The Immune Response Corporation Licenses Hybridon's 2nd-Generation CpG DNA Adjuvant, AMPLIVAX(TM), for Use in Development of a Novel Vaccine for the Prevention and Treatment of HIV

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 This email address is being protected from spambots. You need JavaScript enabled to view it. (Media) - Gwen Rosenberg, Rosenberg Business Communications, (858) 759-0759 Hybridon, Inc. (Investors) - Robert G. Andersen, (617) 679-5500, ext. 5517 or This email address is being protected from spambots. You need JavaScript enabled to view it. (Media) Robert Stanislaro, Noonan Russo Presence, (212) 845 4268
SOURCE The Immune Response Corporation; Hybridon, Inc.

investors, Kathy Lane of The Immune Response Corporation,+1-760-771-2236, This email address is being protected from spambots. You need JavaScript enabled to view it. ; or media, Gwen Rosenberg of RosenbergBusiness Communications, +1-858-759-0759, for The Immune Response Corporation;or investors, Robert G. Andersen of Hybridon, Inc., +1-617-679-5500, ext.5517, This email address is being protected from spambots. You need JavaScript enabled to view it. ; or media, Robert Stanislaro of Noonan RussoPresence, +1-212-845-4268, for Hybridon, Inc.(IMNR HYBN)

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