Prepared by MERRILL CORPORATION

This prospectus is part of a registration statement we filed with the Securities and Exchange Commission, which will be used by Agouron Pharmaceuticals, Inc. to resell the common stock. This means:

Our common stock is listed on the Nasdaq National Market under the symbol "IMNR." On March 30, 2001, the last reported sale price for our common stock on the Nasdaq National Market was $2.53 per share.

Investing in our common stock involves risks. See "Risk Factors" beginning on page 2.

Neither the Securities and Exchange Commission nor any State Securities Commission has approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

You should carefully consider the risks described below before making an investment decision. The risks and uncertainties described below are not the only ones facing us. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also impair our business.

If any of the following risks actually occur, our business could be adversely affected. In those cases, the trading price of our common stock could decline, and you may lose all or part of your investment.

Our failure to develop and commercialize products successfully may cause us to cease operations

We have not completed the development of any products. Our failure to develop and commercialize products successfully may cause us to cease operations. Our potential therapies under development will require significant additional research and development efforts and regulatory approvals prior to potential commercialization.

The discontinuation of a previous Phase 3 trial of REMUNE in May 1999 due to lack of efficacy has had a material adverse effect on us. If our primary marketing partner, Agouron Pharmaceuticals, Inc., a Pfizer Inc. company, or Pfizer, does not successfully complete the current pivotal trial of REMUNE, we may have to abandon REMUNE or seek additional funding.

Our other therapies and technologies are at earlier stages of development than REMUNE and may not be shown to be safe or efficacious or ever receive regulatory approval. Some of our technologies have not yet been tested in humans. Human testing of potential products based on these technologies may not be permitted by regulatory authorities. Even if human testing is permitted, the products based on these technologies may not be successfully developed or be shown to be safe and efficacious.

The results of our preclinical studies and clinical trials may not be indicative of future clinical trial results. A commitment of substantial resources to conduct time-consuming research, preclinical studies and clinical trials will be required if we are to develop any products. Delays in planned patient enrollment in our clinical trials may result in increased costs, program delays or both. None of our potential products may prove to be safe and effective in clinical trials. Food and Drug Administration, or FDA, or other regulatory approvals may not be obtained and even if successfully developed and approved, our products may not achieve market acceptance. Any products resulting from our programs may not be successfully developed or commercially available for a number of years, if at all.

Unacceptable toxicities or side effects may occur at any time in the course of human clinical trials or, if any products are successfully developed and approved for marketing, during commercial use of our products. The appearance of any unacceptable toxicities or side effects could interrupt, limit, delay or abort the development of any of our products or, if previously approved, necessitate their withdrawal from the market.

Our additional financing requirements and limited access to financing may adversely affect our ability to develop products

We will need to raise additional funds to conduct research and development, preclinical studies and clinical trials necessary to bring our potential products to market and to establish manufacturing and marketing capabilities. A failure to raise additional funds would require us to scale back or eliminate some or all of our research and development programs or license to third parties products or technologies that we would otherwise seek to develop ourselves. We estimate that our existing capital resources and available equipment financing will be sufficient to fund our current and planned operations through 2001. We will need to obtain additional financial resources to fund operations beyond 2001.

Although we anticipate that development of REMUNE will continue to represent a significant portion of our overall expenditures, costs related to the development of REMUNE have decreased in 2000. Other anticipated costs with respect to REMUNE will depend on many factors, in particular the continuation of our collaboration with Pfizer.

The timing and amount of our future capital requirements will depend on many factors, including:

Our access to capital could be limited if we are not capable of continued progress in:

If Pfizer terminates its collaboration with us we may have to abandon REMUNE

According to its terms, our binding letter of intent with Pfizer may be terminated at will and at any time by Pfizer. If our agreement with Pfizer were terminated, that might require us to abandon REMUNE.

We may be unable to enter into additional collaborations or maintain existing ones

We intend to seek additional collaborative arrangements to develop and commercialize our products. We may not be able to negotiate collaborative arrangements on favorable terms, or at all, in the future and our current or future collaborative arrangements may not be successful or continue. Under the 1998 Schering collaboration for gene delivery technology, Schering's obligation to fund expired on December 31, 1999. Without funding arrangements, we may have to abandon some of our products under development.

Our patents and proprietary technology may not provide us with any benefit and the patents and proprietary technology of others may prevent us from commercializing products

A failure to obtain meaningful patent protection for our potential products and processes would greatly diminish the value of our potential products and processes.

In addition, whether or not our patents are issued, or issued with limited coverage, others may receive patents, which contain claims applicable to our products. We are aware that AstraZeneca PLC has acquired the rights to a patent, which has been issued in Europe and other countries, that may interfere with our ability to develop some of our technologies related to autoimmune disease if the

patent is upheld after current opposition proceedings. This patent, and others that we are not aware of, may adversely affect our ability to develop and commercialize products.

The patent positions of biotechnology and pharmaceutical companies can be highly uncertain and involve complex legal and factual questions. Therefore, the breadth of claims allowed in biotechnology and pharmaceutical patents cannot be predicted. We also rely upon unpatented trade secrets and know how, and others may independently develop substantially equivalent trade secrets or know how.

We also rely on protecting our proprietary technology in part through confidentiality agreements with our corporate collaborators, employees, consultants and certain contractors. These agreements may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or independently discovered by our competitors.

Our products and processes may infringe, or be found to infringe on, patents not owned or controlled by us, such as the patent owned by AstraZeneca PLC. If relevant claims of third-party patents are upheld as valid and enforceable, we could be prevented from practicing the subject matter claimed in the patents, or would be required to obtain licenses or redesign our products or processes to avoid infringement. Licenses may not be available at all or on commercially reasonable terms and we may not be able to redesign our products or processes to avoid infringement.

Litigation may be necessary to defend against claims of infringement, to enforce our patents or to protect trade secrets. Litigation could result in substantial costs and diversion of management efforts regardless of the results of the litigation. An adverse result in litigation could subject us to significant liabilities to third parties, require disputed rights to be licensed or require us to cease using certain technologies.

Our history of operating losses and our expectations of continuing losses may hurt our ability to continue operations

As of December 31, 2000 we had a consolidated accumulated deficit of $211.0 million. We have not generated revenues from the commercialization of any product. We expect to incur substantial net operating losses over the next several years, which may imperil our ability to continue operations. We may not be able to generate sufficient product revenue to become profitable on a sustained basis, or at all.

The lengthy product approval process and uncertainty of government regulatory requirements may delay or prevent us from commercializing products

Clinical testing, manufacture, promotion and sale of our products are subject to extensive regulation by numerous governmental authorities in the United States, principally the FDA, and corresponding state and foreign regulatory agencies. This regulation may delay or prevent us from commercializing products. Noncompliance with applicable requirements can result in, among other things, fines, injunctions, seizure of products, total or partial suspension of product marketing, failure of the government to grant premarket approval, withdrawal of marketing approvals and criminal prosecution.

The regulatory process for new therapeutic drug products, including the required preclinical studies and clinical testing, is lengthy and expensive. We may not receive necessary FDA clearances for any of our potential products in a timely manner, or at all. The length of the clinical trial process and the number of patients the FDA will require to be enrolled in the clinical trials in order to establish the safety and efficacy of our products is uncertain.

Even if additional clinical trials of REMUNE are successfully completed, the FDA may not approve REMUNE for commercial sale. We may encounter significant delays or excessive costs in our efforts to secure necessary approvals. Regulatory requirements are evolving and uncertain. Future

United States or foreign legislative or administrative acts could also prevent or delay regulatory approval of our products. We may not be able to obtain the necessary approvals for clinical trials, manufacturing or marketing of any of our products under development. Even if commercial regulatory approvals are obtained, they may include significant limitations on the indicated uses for which a product may be marketed.

In addition, a marketed product is subject to continual FDA review. Later discovery of previously unknown problems or failure to comply with the applicable regulatory requirements may result in restrictions on the marketing of a product or withdrawal of the product from the market, as well as possible civil or criminal sanctions.

Among the other requirements for regulatory approval is the requirement that prospective manufacturers conform to the FDA's Good Manufacturing Practices, or GMP. In complying with the FDA's GMP requirements, manufacturers must continue to expend time, money and effort in production, record keeping and quality control to assure that products meet applicable specifications and other requirements. Failure to comply with the FDA's GMP requirements subjects manufacturers to possible FDA regulatory action. We or our contract manufacturers, if any, may not be able to maintain compliance with the FDA's GMP requirements on a continuing basis. Failure to maintain compliance could have a material adverse effect on us.

The FDA has not designated expanded access protocols for REMUNE as "treatment" protocols. The FDA may not determine that REMUNE meets all of the FDA's criteria for use of an investigational drug for treatment use. Even if REMUNE is allowed for treatment use, third party payers may not provide reimbursement for the costs of treatment with REMUNE.

The FDA may not consider REMUNE or any other of our products under development to be appropriate candidates for accelerated approval, expedited review or fast track designation.

Marketing any drug products outside of the United States will subject us to numerous and varying foreign regulatory requirements governing the design and conduct of human clinical trials and marketing approval. Approval procedures vary among countries and can involve additional testing, and the time required to obtain approval may differ from that required to obtain FDA approval. Foreign regulatory approval processes include all of the risks associated with obtaining FDA approval set forth above, and approval by the FDA does not ensure approval by the health authorities of any other country.

Technological change and competition may render our potential products obsolete

The biotechnology industry continues to undergo rapid change and competition is intense and is expected to increase. Competitors may succeed in developing technologies and products that are more effective or affordable than any that we are developing or that would render our technology and products obsolete and noncompetitive. Many of our competitors have substantially greater experience, financial and technical resources and production, marketing and development capabilities than us. Accordingly, some of our competitors may succeed in obtaining regulatory approval for products more rapidly or effectively than us.

Our lack of commercial manufacturing and marketing experience may prevent us from successfully commercializing products

We have not manufactured any of our product candidates in commercial quantities. We may not successfully make the transition from manufacturing clinical trial quantities to commercial production quantities or be able to arrange for contract manufacturing and this could prevent us from commercializing products. Even if REMUNE is successfully developed and receives FDA approval, we have not demonstrated the capability to manufacture REMUNE in commercial quantities. Except for

REMUNE, we have not demonstrated the ability to manufacture our treatments in large-scale clinical quantities either. We rely on a third party for the final inactivation step of the REMUNE manufacturing process. If the existing manufacturing operations prove inadequate, there can be no assurance that any arrangement with a third party can be established on a timely basis or that we can establish other manufacturing capacity on a timely basis.

We have no experience in the sales, marketing and distribution of pharmaceutical products. Thus, our products may not be successfully commercialized even if they are developed and approved for commercialization.

The manufacturing process of our products involves a number of steps and requires compliance with stringent quality control specifications imposed by us and by the FDA. Moreover, our products can only be manufactured in a facility that has undergone a satisfactory inspection by the FDA. For these reasons, we would not be able quickly to replace our manufacturing capacity if we were unable to use our manufacturing facilities as a result of a fire, natural disaster (including an earthquake), equipment failure or other difficulty, or if such facilities are deemed not in compliance with the FDA's GMP requirements and the non-compliance could not be rapidly rectified. Our inability or reduced capacity to manufacture our products would prevent us from successfully commercializing products.

We may enter into arrangements with contract manufacturing companies to expand our own production capacity in order to meet requirements for our products, or to attempt to improve manufacturing efficiency. If we choose to contract for manufacturing services and encounter delays or difficulties in establishing relationships with manufacturers to produce, package and distribute our finished products, clinical trials, market introduction and subsequent sales of the products would be delayed. Further, contract manufacturers must also operate in compliance with the FDA's GMP requirements; failure to do so could result in, among other things, the disruption of product supplies. Our potential dependence upon third parties for the manufacture of our products may adversely affect our profit margins and our ability to develop and deliver products on a timely and competitive basis.

Adverse determinations concerning product pricing, reimbursement and related matters could prevent us from successfully commercializing products

Our ability to earn sufficient returns on our products will depend in part on the extent to which reimbursement for the costs of the products and related treatments will be available from government health administration authorities, private health coverage insurers, managed care organizations and other organizations. Failure to obtain appropriate reimbursement could prevent us from successfully commercializing products. Third party payors are increasingly challenging the price of medical products and services. If purchasers or users of our products are not able to obtain adequate reimbursement for the cost of using the products, they may forego or reduce their use. Significant uncertainty exists as to the reimbursement status of newly approved health care products, and whether adequate third party coverage will be available.

We face an inherent business risk of exposure to product liability and other claims in the event that the development or use of our technology or prospective products is alleged to have resulted in adverse effects. We may not avoid significant liability exposure. We may not have sufficient insurance coverage and we may not be able to obtain sufficient coverage at a reasonable cost. An inability to obtain product liability insurance at acceptable cost or to otherwise protect against potential product liability claims could prevent or inhibit the commercialization of our products. A product liability claim could hurt our financial performance. Even if we avoid liability exposure, significant costs could be incurred that could hurt our financial performance.

Hazardous materials and environmental matters could expose us to significant costs

We may be required to incur significant costs to comply with current or future environmental laws and regulations. Although we do not currently manufacture commercial quantities of our product candidates, we produce limited quantities of these products for our clinical trials. Our research and development and manufacturing processes involve the controlled storage, use and disposal of hazardous materials, biological hazardous materials and radioactive compounds. We are subject to federal, state and local laws and regulations governing the use, manufacture, storage, handling and disposal of these materials and some waste products. Although we believe that our safety procedures for handling and disposing of these materials comply with the standards prescribed by these laws and regulations, the risk of accidental contamination or injury from these materials cannot be completely eliminated. In the event of an accident, we could be held liable for any damages that result, and any liability could exceed our resources. Our operations, business or assets may be materially and adversely affected by current or future environmental laws or regulations.

Subordination of common stock to preferred stock could hurt common stockholders

Our common stock is expressly subordinate to our Series F Convertible Preferred Stock in the event of our liquidation, dissolution or winding up. If we were to cease operations and liquidate our assets, there may not be any remaining value available for distribution to the holders of common stock after providing for the Series F Convertible Preferred Stock liquidation preference.

You could suffer substantial dilution of your investment if our preferred stock is converted into common stock or certain options or warrants to purchase common stock are exercised

In 1998 we sold 200 shares of Series F Convertible Preferred Stock, or Series F Stock, in return for gross proceeds of $10 million. These shares of Series F Stock are currently convertible into at least 2.6 million shares of our common stock, which number is subject to increase if our common stock does not meet certain specified price trading levels. Additionally, on April 28, 2001 we will be required to redeem the Series F Stock in either cash or in shares of our common stock. Further, as of December 31, 2000 we had reserved 7.6 million shares of our common stock for potential issuance upon the exercise of stock options and warrants and payment of dividends on the Series F Stock. Issuance of any of these additional shares could substantially dilute your interest in our company.

Volatility of stock price and absence of dividends may hurt common stockholders

The market price of our common stock, like that of the common stock of many other biopharmaceutical companies, has been and is likely to be highly volatile. Factors such as the following could have a significant adverse impact on the market price of our common stock:

We have never paid cash dividends on our common stock and do not anticipate paying any cash dividends in the foreseeable future.

Changes to financial accounting standards may affect our reported results of operations

We prepare our financial statements to conform with generally accepted accounting principles, or GAAP. GAAP are subject to interpretation by the American Institute of Public Accountants, the Securities and Exchange Commission and various bodies formed to interpret and create appropriate accounting policies. A change in those policies can have a significant effect on our reported results and may even affect our reporting of transactions completed before a change is announced. Accounting policies affecting many other aspects of our business, including rules relating to purchase and pooling-of-interests accounting for business combinations, employee stock option grants and revenue recognition have recently been revised or are under review. Changes to those rules or the questioning of current practices may adversely affect our reported financial results or the way we conduct our business. In December 1999, the Securities and Exchange Commission issued Staff Bulletin ("SAB") No. 101—"Revenue Recognition in Financial Statements." We implemented SAB 101 in the fourth quarter of 2000 by adjusting the first, second and third quarters of our 2000 financial statements. Our statement of operations reflects a one-time charge to earnings of $13.2 million for the cumulative effect of the change in accounting principle as of January 1, 2000. Deferred revenue recognized, to reflect the application of the SAB 101 adjustment, was approximately $960,000 for each quarter of 2000. The balance of $9.7 million of deferred revenue from this adjustment will be recognized as revenue over the expected development period, which is estimated to be through June 2003. See Footnote 2 to the Consolidated Financial Statement included in our Annual Report on Form 10-K.

In addition, our preparation of financial statements in accordance with GAAP requires that we make estimates and assumptions that affect the recorded amounts of assets and liabilities, disclosure of those assets and liabilities at the date of the financial statements and the recorded amounts of expenses during the reporting period. A change in the facts and circumstances surrounding those estimates could result in a change to our estimates and could impact our future operating results.

Our certificate of incorporation and bylaws include provisions that could make attempts by stockholders to change management more difficult

The approval of 66²/3 percent of our voting stock is required to approve certain transactions and to take certain stockholder actions, including the calling of special meetings of stockholders and the amendment of any of the anti-takeover provisions, such as those providing for a classified board of directors, contained in our certificate of incorporation. The practical effect of these provisions is to make attempts by stockholders to change management more difficult.

Prior to making an investment decision with respect to the common stock offered hereby, prospective investors should also carefully consider any specific factors set forth under a caption "risk factors" in the applicable prospectus supplement, if any, together with all of the other information appearing in this prospectus or the prospectus supplement or incorporated by reference into this prospectus.

When used in this prospectus, the words "intends to," "believes," "anticipates," "expects" and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based largely on our expectations and are subject to a number of risks and uncertainties, some of which are beyond our control. For a discussion of some of these risks, see "Risk Factors." These forward-looking statements speak only as of the date of this prospectus. You are urged not to rely on these forward-looking statements. You are advised, however, to consult any further disclosures we make on related subjects in our current reports on Form 8-K, Quarterly Reports on Form 10-Q and Annual Reports on Form 10-K.

We file annual, quarterly and special reports, proxy statements and other information with the SEC. This information can be (1) read and copied at the public reference facilities maintained by the SEC at 450 Fifth Street, N.W., Judiciary Plaza, Washington, D.C., and at the SEC's Chicago Regional Office, 500 West Madison Street, Chicago, Illinois; and New York Regional Office, 7 World Trade Center, New York, New York and (2) accessed via a Web site maintained by the SEC (http://www.sec.gov). Copies of the material can also be obtained from the Public Reference Section of the SEC at 450 Fifth Street, N.W., Judiciary Plaza, Washington, D.C. 20549 at prescribed rates. Please call the SEC at 1-800-SEC-0330 for further information on the public reference rooms.

This prospectus is a part of a registration statement we filed with the SEC. This prospectus does not contain all of the information set forth in the registration statement. For more information about us and our common stock, you should read the registration statement and its exhibits and schedules. Copies of the registration statement, including its exhibits may be obtained from the SEC's principal office in Washington, D.C. upon payment of the fees prescribed by the SEC, may be examined without charge at the offices of the SEC, or may be accessed via a web site maintained by the SEC (http://www.sec.gov).

The SEC allows us to "incorporate by reference" the information we file with them, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings made by us with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 (File No. 0-18006):

Upon written or oral request, we will provide without charge to each person to whom a copy of this prospectus is delivered a copy of the documents incorporated by reference into this prospectus (other than exhibits to these documents unless the exhibits are specifically incorporated by reference into those documents). Requests should be submitted in writing or by telephone at (760) 431-7080 to The Immune Response Corporation, at our principal executive offices, 5935 Darwin Court, Carlsbad, California 92008.

We will not receive any proceeds from the sale of common stock by the selling stockholder in the offering.

We entered into a common stock purchase agreement with the selling stockholder in June 1998, under which we received seven payments of $2 million each for the purchase of shares of our unregistered common stock. Pursuant to the common stock purchase agreement we sold and issued 1,477,609 shares of our common stock to the selling stockholder of which 160,000 shares were previously sold by the selling stockholder.

You should consult your own tax advisor about the income tax issues and the consequences of holding and disposing of our common stock.

As of April 2, 2001 there was one selling stockholder as set forth below. Share ownership information is based upon information supplied by Agouron Pharmaceuticals, Inc.

Selling Stockholder		Shares of Common Stock Issuable Held at April 2, 2001		Number of Shares Being Offered		Percentage of Common Stock to be Held After Sale of Common Stock
Agouron Pharmaceuticals, Inc.		1,317,609		1,317,609		0%

We have a material relationship with the selling stockholder. During June 1998, we entered into a collaborative agreement with the selling stockholder, under which we exclusively licensed to the selling stockholder the marketing rights to REMUNE in North America, Europe, Japan and certain other countries. Pursuant to this agreement, if REMUNE receives regulatory approval, we will manufacture commercial supplies of REMUNE and will share with the selling stockholder profits from the commercialization of REMUNE on a ⁵⁰/50 basis. As part of the June 1998 agreement, the selling stockholder agreed to make up to six quarterly payments of $3 million each for research and development, of which all six payments have been received, and to make additional payments upon achievement, if any, of certain milestones. We also entered into the common stock purchase agreement with the selling stockholder pursuant to which we received seven payments of $2 million each for the purchase of shares of our unregistered common stock.

The selling stockholder (or, subject to applicable law, its pledges, donees, distributees, transferees or other successors in interest) may sell shares from time to time in public transactions, on or off the

Nasdaq National Market, or private transactions, at prevailing market prices or at privately negotiated prices, including but not limited to, one or any combination of the following types of transactions:

In effecting sales, brokers or dealers engaged by the selling stockholder may arrange for other brokers or dealers to participate in the resales. The selling stockholder also may pledge the shares to a financial institution, broker or dealer. Upon a default, the financial institution, broker or dealer may effect sales of the pledged shares pursuant to this prospectus.

Brokers, dealers or agents may receive compensation in the form of commissions, discounts or concessions from selling the stock in amounts to be negotiated in connection with the sale. The selling stockholder and any participating brokers or dealers may be deemed to be "underwriters" within the meaning of the Securities Act in connection with such sales. In such event, any commission, discount or concession these "underwriters" receive may be deemed to be underwriting compensation.

The validity of the issuance of the shares offered in this prospectus was passed upon for us by Pillsbury Winthrop LLP, San Francisco, California. A partner of Pillsbury Winthrop LLP owns 15,000 shares of our common stock and an option to acquire 20,000 shares of our common stock.

The consolidated financial statements of The Immune Response Corporation as of December 31, 2000 and 1999 and for each of the three years in the period ended December 31, 2000 included in the Company's Annual Report on Form 10-K and incorporated herein by reference have been audited by Arthur Andersen LLP, independent public accountants, as indicated in their reports with respect thereto, and are incorporated herein by reference in reliance upon the authority of said firm as experts in giving said reports.

We have not authorized any dealer, salesperson or any other person to give any information or to represent anything not contained in this prospectus. You must not rely on any unauthorized information. This prospectus does not offer to sell or seek an offer to buy any shares in any jurisdiction where it is unlawful. The information contained in this prospectus is correct only as of the date of this prospectus, regardless of the time of the delivery of this prospectus or any sale of the shares.

		Page
Risk Factors		2
Additional or Updated Risk Factors		9
Special Note Regarding Forward-Looking Information		9
Where You Can Find More Information		9
Use of Proceeds		10
Issuance of Common Stock to the Selling Stockholders		10
Income Tax Considerations		10
Selling Stockholders		10
Plan of Distribution		10
Legal Matters		11
Experts		11