PORTIONS OF THIS DOCUMENT HAVE BEEN OMITTED (DESIGNATED BY AN ASTERISK (*)
     AND WHITE SPACE) AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
           COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT
                     DATED AUGUST 4, 1998; FILE NO. 0-15609
                         COMMON STOCK PURCHASE AGREEMENT

       This Common Stock Purchase  Agreement  ("Agreement")  is made and entered
into as of June 11,  1998 by and  between THE IMMUNE  RESPONSE  CORPORATION.,  a
Delaware  corporation  (hereinafter  referred  to as the  Company)  and  AGOURON
PHARMACEUTICALS,  INC.,  a California  corporation  ("Agouron"),  which  parties
hereby agree as follows:

1.     AUTHORIZATION; COMMITMENT; CLOSING

       1.01 AUTHORIZATION.  The Company proposes to authorize, issue and sell to
Agouron on or before  January 15,  2000,  certain  amounts of its common  stock,
$.0025 par value ("Common Stock"), as described and determined below.

       1.02  COMMITMENT.  Subject to Paragraph 5.06 and the terms and conditions
hereof and on the basis of the  representations  and warranties  hereinafter set
forth,  the Company  agrees to issue and sell to Agouron,  and Agouron  agree to
purchase  from the Company as of the dates and for the  consideration  set forth
below, the number of shares of the Company's  Common Stock as determined  below.
The Common  Stock  which  Agouron  is  acquiring  pursuant  to the terms of this
Agreement is hereinafter  referred to as "Restricted  Common Stock".  Agouron is
hereinafter  sometimes  referred to as the  "Purchaser."  The  purchases  of the
Common Stock shall occur on the seven  purchase  dates set forth below.  On each
purchase  date,  Agouron  shall be entitled to acquire  such number of shares of
Restricted  Common  Stock  (rounded  up to the  nearest  whole  share) as may be
purchased for  $2,000,000,  at a purchase  price equal to the stated premium set
forth  opposite the applicable  purchase  date,  over the then fair market value
("FMV") of the Common Stock on The NASDAQ Stock Market.  FMV shall be defined as
the average closing price of the Common Stock on The NASDAQ Stock Market for the
five (5) trading days immediately preceding the referenced purchase date. In the
event the FMV is * on any purchase date, the premium applicable to such purchase
date shall be adjusted to *

PURCHASE DATE                      PURCHASE PRICE                PREMIUM OVER FM
-------------                      --------------                ---------------
June 11, 1998                      $2,000,000                           50%
October 15, 1998                   $2,000,000                            *
January 15, 1999                   $2,000,000                            *
April 15, 1999                     $2,000,000                            *
July 15, 1999                      $2,000,000                            *
October 15, 1999                   $2,000,000                            *
January 15, 2000                   $2,000,000                            *

       1.03  CLOSING.  Separate  closings  of  the  purchase  and  sale  of  the
Restricted Common Stock  ("Closings")  shall occur on each of the purchase dates
set forth  above and shall take place at such time and place as the  Company and
Purchaser  shall agree.  At each Closing the Company  shall deliver to Purchaser
the number of shares of  Restricted  Common Stock  required by  Paragraph  1.02,
above,  upon  delivery to the Company by Purchaser of a certified  check or wire
transfer of funds in the amount of $2,000,000. The Restricted Common Stock to be
delivered  to Agouron  hereunder  at each  Closing will be evidenced by a single
certificate  

<PAGE>

registered  in  Agouron's  name or in the name of such  nominee  as
Agouron  may  specify  and,  when  issued in  accordance  with the terms of this
Agreement  for the  consideration  expressed  herein,  will be duly  authorized,
validly  issued,  fully paid,  nonassessable  and free and clear of any liens or
encumbrances  caused or  created by the  Company  (except  that such  Restricted
Common Stock of the Company will be subject to  restrictions  on transfer  under
federal and applicable state securities laws).

2.     REPRESENTATIONS

       2.01  REPRESENTATIONS OF THE COMPANY. The Company represents and warrants
as follows:

                  (a) The  Company  is a  corporation  duly  organized,  validly
                  existing and in good  standing  under the laws of the State of
                  Delaware and has all requisite  power and authority  which are
                  necessary to own and operate its business and  properties  and
                  to carry on its business as it is being conducted. The Company
                  is duly  licensed and  qualified  and in good  standing in the
                  State of California and in such other  jurisdictions  in which
                  the  ownership  or lease of  property  or the  conduct  of its
                  business makes such licensing or qualification necessary.

                  (b) There are no  proceedings  pending or, to the knowledge of
                  the Company,  threatened  against or affecting  the Company in
                  any court or before any  governmental  authority  or agency or
                  arbitration board or tribunal which involve the possibility of
                  materially and adversely  affecting the properties,  business,
                  prospects  or  condition   (financial  or  otherwise)  of  the
                  Company.

                  (c) The issuance and sale of the  Restricted  Common Stock and
                  compliance  by the Company with all of the  provisions of this
                  Agreement are within the  corporate  powers of the Company and
                  have been duly  authorized by all proper  corporate  action on
                  the part of the  Company  and will  not (i)  conflict  with or
                  result  in any  breach  of any of  the  terms,  conditions  or
                  provisions  of, or  constitute a default under the Articles of
                  Incorporation  of the  Company or the  Bylaws of the  Company,
                  (ii)  conflict  with or  result  in any  breach  of any of the
                  terms,  conditions or  provisions  of, or constitute a default
                  under or give any party the right to terminate  or  accelerate
                  performance  under any other  agreement or instrument to which
                  the Company is a party (iii)  require  consent under any other
                  contract to which the  Company is a party,  (iv) result in the
                  creation or imposition of any lien, charge or encumbrance upon
                  any property or assets of the Company pursuant to the terms of
                  any  other  contract  to which the  Company  is a party or (v)
                  conflict  with  any  provision  of  any  applicable  judgment,
                  decree,  order,  statute,  rule, or regulation of any court or
                  any public,  governmental or regulatory  agency or body having
                  jurisdiction over the Company.

                  (d) This  Agreement  is a valid and binding  agreement  of the
                  Company and is  enforceable  against the Company in accordance
                  with the terms hereof,  except as such  enforceability  may be
                  affected by applicable bankruptcy laws and equitable remedies.
<PAGE>

                  (e) The  authorized  capital stock of the Company  consists of
                  5,000,000  shares of  preferred  stock  (preferred  stock) and
                  40,000,000 shares of common stock. As of the date hereof,  200
                  shares  of  its  Series  F  Convertible  Preferred  Stock  are
                  outstanding.  This preferred stock is convertible  into common
                  stock initially at a conversion price equivalent to $14.07 per
                  share of common stock. If the Company's  common stock does not
                  trade at prices  higher than $14.07 per share over a period of
                  time, the conversion price will be adjusted  downward on April
                  24, 1999 (or sooner if the Company issues common stock at less
                  than $14.07 per share) and quarterly thereafter. As of June 9,
                  1998,   22,900,350   shares   of  voting   common   stock  are
                  outstanding.  As of the date hereof,  4,497,749  stock options
                  issued  pursuant to the  Company's  stock option plans and two
                  (2) warrants to purchase a total of 2,051,281 shares of voting
                  stock are outstanding.  Up to 6,180,000 shares of common stock
                  may be issued under the Company's  stock option plans.  Except
                  as set  forth  above,  there are no other  options,  warrants,
                  conversion  privileges,  preemptive rights, or rights of first
                  refusal  granted by the  Company in favor of any other  person
                  presently  outstanding  or in existence to purchase or acquire
                  any  of  the  authorized  but  unissued  Common  Stock  of the
                  Company, other than any of such items granted pursuant to this
                  Agreement. The Company has provided to Purchaser copies of its
                  currently in effect Articles of Incorporation and Bylaws,  its
                  Form  10-K for the year  ended  December  31,  1997,  its 1997
                  Annual Report,  its Proxy  statement  dated April 27, 1998 and
                  its Form  10-Q for the  quarter  ended  March  31,  1998.  The
                  Company  warrants  that  the  information  contained  in  such
                  documents as updated and supplemented prior to the date of the
                  Closing is true and correct and when taken as a whole does not
                  omit  a fact  necessary  to  make  the  information  contained
                  therein in light of the circumstance under which the documents
                  were made (taking into account,  without limitation,  the type
                  of  transaction   contemplated   by  this  Agreement  and  the
                  sophistication  and nature of the Purchaser),  not misleading.
                  The Company  acknowledges that the Purchaser is relying on the
                  written documentation  provided by the Company to Purchaser as
                  described  above  in  making  its  decision  to  purchase  the
                  Restricted Common Stock.

                  (f) Since March 31, 1998, except for the sale of 200 shares of
                  Series F Convertible  Preferred  Stock for $10 million,  there
                  has not been any change in the assets, liabilities,  financial
                  condition or  operations  of the Company other than changes in
                  the ordinary course of business, none of which individually or
                  in the aggregate  have had a material  adverse  affect on such
                  assets, liabilities,  financial condition or operations of the
                  Company.

       2.02  REPRESENTATIONS  OF THE  PURCHASER.  The Purchaser  represents  and
warrants as follows:

                  (a) It is the intent of the Purchaser that its purchase of the
                  Restricted  Common Stock  contemplated by this Agreement shall
                  constitute a transaction  exempt from  registration  under the
                  Securities Act of 1933, as amended (the "Securities  Act") and
                  any applicable state securities laws.
<PAGE>

                  (b)  Purchaser  will not offer or sell any  Restricted  Common
                  Stock except pursuant to an effective  registration  statement
                  under  the  Securities  Act or in  transactions  which  do not
                  require registration under the Securities Act.

                  (c)  Purchaser is a  corporation  duly  organized  and validly
                  existing  under the laws of the State of California is in good
                  standing  under  such  laws  and has all  requisite  corporate
                  powers and authority to enter into this Agreement.

                  (d) On or prior to the date of the initial Closing,  Purchaser
                  will have taken all action  necessary  for the  authorization,
                  execution, delivery and performance of this Agreement.

                  (e) Purchaser has (i) reviewed this Agreement, and the written
                  statements, and documents, delivered to Purchaser as described
                  in Section 2.01(e);  and, (ii) received  satisfactory response
                  from the  Company  as to matters  about  which  Purchaser  has
                  inquired  relating  to this  Agreement,  and  other  documents
                  described  in Section  2.01(e) and  relating to the  Company's
                  business  condition,  prospects  and  plans  as  necessary  to
                  evaluate  the merits  and risks of  acquiring  the  Restricted
                  Common   Stock.   Purchaser  has  informed  the  Company  that
                  Purchaser is relying on all such  information and documents in
                  making its decision to purchase the Restricted Common Stock.

                  (f) Purchaser (i) has had the risks involved in the investment
                  represented  by this Agreement  explained;  (ii) has knowledge
                  and  experience in financial and business  matters to evaluate
                  the merits  and risks of the  investment  represented  by this
                  Agreement;  (iii)  is able to bear  the  economic  risk of the
                  investment represented by this Agreement (including a complete
                  loss of this  investment);  and (iv) has determined  that this
                  investment is suitable for  Purchaser in light of  Purchaser's
                  financial     circumstances    and    available     investment
                  opportunities.

                  (g) Purchaser is acquiring the Restricted Common Stock for its
                  own  account  and with its  general  assets for the purpose of
                  investment  and not  with a view to the  resale,  transfer  or
                  distribution thereof, and has no present intention of selling,
                  transferring,   negotiating  or  otherwise  disposing  of  any
                  Restricted  Common  Stock.  Notwithstanding  anything  in this
                  Agreement  to the  contrary,  it is agreed that the  Purchaser
                  shall  have the  right to assign or  transfer  the  Restricted
                  Common Stock to its Affiliates at any time without the consent
                  of the Company.

3.  NON-DISCLOSURE.  Except as agreed to by the parties  neither the Company nor
the Purchaser  shall release any  information to any third party with respect to
any of the terms of this  Agreement  without  the prior  written  consent of the
other,  which  consent  shall not  unreasonably  be withheld.  This  prohibition
includes,  but is not limited to,  press  releases,  promotional  materials  and
discussions with the media. If the Company determines that it is required by law
to release information to any third party regarding the terms of this Agreement,
it shall notify the Purchaser of this fact prior to releasing  the  information.
The notice to the Purchaser shall include the text of the  information  proposed
for  release.  The  Purchaser  shall 
<PAGE>

have the right to confer with the Company  regarding  the necessity for the
disclosure and the text of the information proposed for release.

4.     COMPLIANCE WITH SECURITIES ACT

       4.01 CERTAIN DEFINITIONS.  As used herein, the following terms shall have
the following respective meanings:

                  (a)  COMMISSION.   Shall  mean  the  Securities  and  Exchange
                  Commission,   or  any  other   Federal   agency  at  the  time
                  administering  the Securities Act or the Trust  Indenture Act,
                  as the case may be.

                  (b) SECURITIES  ACT. Shall mean the Securities Act of 1933, as
                  amended,  or any similar  Federal  statute,  and the rules and
                  regulations  of the  Commission  thereunder,  all as the  same
                  shall be in effect at the relevant time.

                  (c) EXCHANGE ACT.  Shall mean the  Securities  Exchange Act of
                  1934,  as amended,  or any similar  Federal  statute,  and the
                  rules and regulations of the Commission thereunder, all as the
                  same shall be in effect at the relevant time.

                  (d)  RESTRICTED  COMMON STOCK.  Shall mean the Common Stock of
                  the Company issued and sold pursuant to this  Agreement  which
                  by the terms  hereof is required to bear the legend  specified
                  in Section 4.02 hereof.

       4.02 RESTRICTION OF TRANSFERABILITY;  LEGEND. Shares of Restricted Common
Stock shall not be resold or transferred  unless registered under the Securities
Act or unless an  exemption  from  registration  is  available  for such sale or
transfer.  The conditions specified below are intended to ensure compliance with
the provisions of the  Securities Act in respect of any transfer of stock.  Each
certificate for shares of Restricted  Common Stock shall be stamped or otherwise
imprinted with a legend in substantially the following form:

                           The shares  evidenced  by this  certificate  have not
                           been registered  under the Securities Act of 1933, as
                           amended,  and may not be sold or  transferred  in the
                           absence  of  such   registration   or  an   exemption
                           therefrom  under said Securities Act and the transfer
                           of such  shares is  subject  to terms and  conditions
                           specified  in the  Common  Stock  Purchase  Agreement
                           dated as of June 11,  1998,  between  the Company and
                           Agouron Pharmaceuticals, Inc.

If shares of Restricted Common Stock evidenced by certificates  bearing a legend
required  by this  Section  4.02  are  sold in  accordance  with a  registration
statement which has become effective under the Securities Act, or if the Company
shall  receive an opinion of its counsel to the effect that any legend  required
under this  Section  4.02 is not, or is no longer,  necessary  or required  with
respect  to  such  shares  (including,   without  limitation,   because  of  the
availability  of the  exemption  afforded by Rule 144 of the  General  Rules and
Regulations  of the  Commission),  the  Company  shall,  or shall  instruct  its
transfer  agent and registrar  to, remove such legend or issue new  certificates
without such legend in lieu thereof.
<PAGE>

       4.03   INFORMATION REQUIREMENTS.  The Company agrees to:

                  (a) Make and keep public information  available,  as such term
                  is  understood  and  defined in  Commission  Rule 144 and Rule
                  144A, under the Securities Act;

                  (b) Use its best  efforts  to file  with the  Commission  in a
                  timely manner all reports and other documents  required of the
                  Company under the Securities Act and the Exchange Act; and

                  (c) Furnish to any holder of Restricted Common Stock a copy of
                  the most recent annual or quarterly report of the Company, and
                  such other  publicly  available  reports and  documents of the
                  Company,  so that such holder may avail  itself of any rule or
                  regulation  of the  Commission  allowing  it to sell  any such
                  securities without registration.

       4.04 PIGGY-BACK  REGISTRATION  RIGHTS.  If the Company before January 15,
2001  contemplates  a  public  offering  of  shares  of its  Common  Stock to be
registered  under the Securities  Act, the Company shall so notify the Purchaser
in writing of its  intention  to do so, at least  twenty  (20) days prior to the
filing of a registration statement for such offering. If Purchaser gives written
notice to the  Company,  within ten (10) days of receipt of the notice  from the
Company,  of Purchaser's  desire to have its Restricted Common Stock included in
such  registration  statement,  Purchaser may, subject to the provisions of this
Section 4.04,  have its Restricted  Common Stock  included in such  registration
statement.   The  Company  shall  bear  all  expenses  in  connection  with  the
registration and sale of any such Restricted  Common Stock,  other than the fees
or  disbursements  of any  special  counsel  which the  Purchaser  may retain in
connection with the  registration of its Restricted  Common Stock or any portion
of the  underwriter's  commission,  discounts and expenses  attributable  to the
Restricted Common Stock being offered and sold by the Purchaser. Notwithstanding
the foregoing,  if the managing underwriter of any such offering determines that
the number of shares proposed to be sold by the Company,  by other  shareholders
having piggy-back rights,  and/or by the Purchaser is greater than the number of
shares which the underwriter believes feasible to sell at the time, at the price
and upon the terms approved by the Company,  then the number of shares which the
underwriter  believes  may be sold  shall  be  allocated  for  inclusion  in the
registration  statement in the  following  order of  priority:  (i) shares being
offered by the Company;  and (ii) pro rata among the other  shareholders and the
Purchaser,  based on the  number  of shares of  Common  Stock  each  shareholder
requested to be  registered.  The Company  shall have the right to designate the
managing  underwriter in respect of a public  offering  pursuant to this Section
4.04.

       4.05       ADDITIONAL COVENANTS CONCERNING SALE OF SHARES.

                  (a) The Company will notify the Purchaser of the effectiveness
                  of any registration statement in which Purchaser has exercised
                  registration  rights granted  pursuant to the terms of Section
                  4.04,  together  with a list of the  jurisdictions  where  the
                  Company has  qualified  or is exempt from  registration  under
                  applicable state securities laws.
<PAGE>

                  (b) The Company will prepare and file with the Commission such
                  amendments and supplements to any registration statement filed
                  pursuant to the terms of Section 4.04 (and any prospectus used
                  in  connection  with such  registration  statement)  as may be
                  necessary to comply with the  provisions of the Securities Act
                  with  respect to the sale of  Restricted  Common  Stock by the
                  Purchaser.

                  (c) The Company  will  furnish to the  Purchaser a  reasonable
                  number of copies of the prospectus  used in connection  with a
                  registration  statement filed pursuant to the terms of Section
                  4.04,  including a preliminary  prospectus,  which  prospectus
                  conforms to the  requirements  of the Securities Act, and such
                  other  documents as the Purchaser may reasonably  request,  in
                  order  to  facilitate  the   disposition  of  the  Purchaser's
                  Restricted Common Stock.

                  (d) In connection with any registration  statement referred to
                  in Section 4.04 of this  Agreement,  Purchaser will furnish to
                  the Company  such  information  as the Company may  reasonably
                  require  from  Purchaser  for  inclusion  in the  registration
                  statement (and the prospectus included therein).

                  (e) The  Company's  obligations  under  Section  4.04 shall be
                  conditioned  upon  Purchaser  executing and  delivering to the
                  Company its agreement,  in a form  satisfactory to counsel for
                  the  Company,   that  it  will  comply  with  all   applicable
                  provisions  of the  Securities  Act,  the  Exchange  Act,  the
                  securities  acts  of  applicable  states  and  any  rules  and
                  regulations  promulgated  under such acts and will  furnish to
                  the  Company  information  about  sales  made in  such  public
                  offering.

       4.06       INDEMNIFICATION

         In the  event  any of the  Restricted  Common  Stock  of  Purchaser  is
included in a registration statement under Section 4.04 of this Agreement:

                  (a) To the extent permitted by law, the Company will indemnify
                  and hold harmless the Purchaser and its  Affiliates  and their
                  respective  officers,  directors  and  employees,  against any
                  losses, claims,  damages, or liabilities (joint or several) to
                  which they may become  subject under the  Securities  Act, the
                  Exchange  Act or other  federal or state law,  insofar as such
                  losses, claims, damages, or liabilities (or actions in respect
                  thereof)  arise out of or are based upon any of the  following
                  statements,  omissions or  violations  (hereinafter  sometimes
                  collectively referred to as a "Violation(s)"):  (i) any untrue
                  statement  or alleged  untrue  statement  of a  material  fact
                  contained  in  such  registration  statement,   including  any
                  preliminary  prospectus or final prospectus  contained therein
                  or any amendments or supplements thereto; (ii) the omission or
                  alleged  omission to state therein a material fact required to
                  be stated therein, or necessary to make the statements therein
                  not misleading; or (iii) any violation or alleged violation by
                  the Company of the Securities Act, the Exchange Act, any state
                  securities law or any rule or regulation promulgated under the
                  Securities Act, the Exchange Act or any state  securities law;
                  and the Company will
<PAGE>

                  reimburse each such indemnified party for
                  any  legal  or other  expenses  reasonably  incurred  by it in
                  connection  with  investigating  or  defending  any such loss,
                  claim, damage,  liability or action;  provided,  however, that
                  the indemnity  agreement  contained in this Section 4.06 shall
                  not apply to  amounts  paid in  settlement  of any such  loss,
                  claim,  damage,  liability  or  action if such  settlement  is
                  effected  without the consent of the  Company  (which  consent
                  shall not be unreasonably withheld or delayed),  nor shall the
                  Company be liable in any such case for any such  loss,  claim,
                  damage,  liability  or action to the extent that it arises out
                  of or is based upon a Violation which occurs in reliance upon,
                  and  in  conformity  with,   written   information   furnished
                  expressly for use in connection with such registration, by any
                  such indemnified party.

                  (b) To  the  extent  permitted  by  law,  the  Purchaser  will
                  indemnify and hold harmless the Company and its Affiliates and
                  their respective officers, directors and employees against any
                  losses, claims,  damages, or liabilities (joint or several) to
                  which they may become  subject under the  Securities  Act, the
                  Exchange  Act or other  federal or state law,  insofar as such
                  losses, claims, damages, or liabilities (or actions in respect
                  thereof)  arise out of or are based  upon any  Violations,  in
                  each case to the  extent  (and only to the  extent)  that such
                  Violation  occurs in reliance  upon,  and in conformity  with,
                  written  information   furnished  by  the  Purchaser  and  its
                  Affiliates  and  their  respective  officers,   directors  and
                  employees to the Company  expressly for use in connection with
                  such registration;  and the Purchaser will reimburse each such
                  indemnified  party for any legal or other expenses  reasonably
                  incurred by it in connection with  investigating  or defending
                  any such loss, claim, damage,  liability or action;  provided,
                  however,  that  the  indemnity  agreement  contained  in  this
                  Section 4.06 shall not apply to amounts paid in  settlement of
                  any such  loss,  claim,  damage,  liability  or action if such
                  settlement is effected  without the consent of the  Purchaser,
                  which consent shall not be unreasonably withheld or delayed.

                  (c) Promptly after receipt by an indemnified  party under this
                  Section  4.06 of  notice  of the  commencement  of any  action
                  (including any governmental  action),  such indemnified  party
                  will, if a claim in respect  thereof is to be made against the
                  indemnifying   party  under  this  Section  4.06,  notify  the
                  indemnifying party in writing of the commencement  thereof and
                  the indemnifying party shall have the right to participate in,
                  and,  to the  extent the  indemnifying  party so  desires,  to
                  assume the defense thereof with counsel mutually  satisfactory
                  to the parties.

5.     MISCELLANEOUS

       5.01 EXPENSES;  FINDERS FEES. Neither party shall pay expenses and finder
fees for or to the other in connection with this transaction.  Each party agrees
to  indemnify  and hold the other  party  harmless  from any  liability  for any
commission  or  compensation  in the nature of a  finder's  fee to any broker or
other person (and the costs and expenses of defending  against such liability or
asserted liability) claiming to have been hired or engaged by the party.

       5.02  REPLACEMENT  OF  CERTIFICATES  FOR  RESTRICTED  COMMON STOCK.  Upon
receipt by the Company of evidence  reasonably  satisfactory  to it of the loss,
theft,  destruction or mutilation of
<PAGE>

any certificate  evidencing any Restricted  Common Stock,  the Company will
execute,  register and deliver,  in lieu thereof, a new certificate for an equal
number of shares  of  Restricted  Common  Stock.  In the case of loss,  theft or
destruction of a certificate,  at the election of the Company, the Purchaser may
be required to provide an indemnity reasonably satisfactory to the Company or to
post a surety bond in an amount equal to the value of the shares  represented by
the new certificate.

       5.03  NOTICE.  Any notice  required  to be given  under the terms of this
Agreement  shall be in  writing,  and shall be given in person,  transmitted  by
telecopier,   e-mail  or  similar  electronic  communication,   delivered  by  a
recognized  overnight  delivery  service such as Federal Express or sent by mail
(certified or  registered  or air mail for  addresses  outside of the country of
origin), return receipt requested,  postage prepaid and addressed to the Company
at 5935 Darwin Court,  Carlsbad,  California 92008, or such other address as the
Company may  designate  to  Purchaser  in writing and to the  Purchaser,  at the
address  appearing at the  beginning of this  Agreement or such other address as
Purchaser may designate to the Company in writing.  Except as otherwise provided
herein,  any notice so given shall be deemed  delivered  upon the earlier of (i)
actual receipt;  (ii) receipt by sender of confirmation if telecopied or sent by
e-mail or  similar  electronic  communication;  (iii) two  business  days  after
delivery to such overnight  delivery  service;  or (iv) five business days after
deposit in the mail.

       5.04  SUCCESSORS AND ASSIGNS.  This  Agreement  shall be binding upon the
parties and their respective successors and assigns.

       5.05 SURVIVAL OF REPRESENTATIONS, ETC. All covenants, representations and
warranties  made by the  parties  herein  shall  survive  the  Closings  and the
delivery of this Agreement and the shares of Restricted  Common Stock  purchased
hereunder.

       5.06 TERMINATION.  Purchaser's  obligation to purchase  Restricted Common
Stock  under  this  Agreement  shall  terminate  with  respect  to any  purchase
obligations  whose purchase dates under Paragraph 1.02 occur after Purchaser has
elected to terminate, in its entirety, all of Purchaser's rights and obligations
under the  Letter of  Intent  ("LOI")  dated  June 11,  1998 and the  Definitive
Agreement (as defined in the LOI) between the parties.

       5.07  SEVERABILITY.  Should any part of this  Agreement for any reason be
declared  invalid,  such decision shall not affect the validity of any remaining
portion,  which  remaining  portion  shall remain in force and effect as if this
Agreement had been executed with the invalid portion  thereof  eliminated and it
is hereby  declared  the  intention  of the parties  hereto that they would have
executed the remaining  portion of this Agreement  without including therein any
such part,  parts, or portion which may, for any reason,  be hereafter  declared
invalid.

       5.08  GOVERNING  LAW. This  Agreement  shall be construed and enforced in
accordance  with,  and governed by, the laws of the State of California  without
regard to its conflict of law provisions.

       5.09 CAPTIONS,  FORM OF PRONOUNS. The descriptive headings of the various
sections  or parts of this  Agreement  are for  convenience  only and  shall not
affect the meaning or construction of any of the provisions hereof. All pronouns
used in this Agreement shall be deemed to include masculine, feminine and neuter
forms.
<PAGE>

       5.10 AGREEMENT IS ENTIRE CONTRACT.  This Agreement constitutes the entire
contract  between  the  parties  hereto  related  to the  purchase  and  sale of
Restricted  Common  Stock and no party  shall be liable or bound to the other in
any  manner  by  any  warranties,   representations   or  covenants   except  as
specifically set forth herein.

       5.11 THIRD PARTIES.  Nothing in this Agreement is intended to confer upon
any  party,  other  than the  parties  hereto,  and their  respective  permitted
successors and assigns, any rights, remedies,  obligations, or liabilities under
or by reason of this Agreement, except as expressly provided herein.

       5.12 AMENDMENT AND WAIVER. Any provision of this Agreement may be amended
and the  observance of any term hereof may be waived  (either  prospectively  or
retroactively  and either  generally or in a particular  instance) only with the
written consent of the Company and the Purchaser.

       5.13  AFFILIATES.  References  to  Purchaser in this  Agreement  shall be
deemed to  include  direct  or  indirect  subsidiaries  of  Purchaser.  The term
"Affiliate" shall have the meaning defined in the LOI.

       5.14 DISPUTE RESOLUTION. In the event of any controversy or claim arising
out of or relating to any provision of this Agreement,  the parties shall try to
settle their differences  amicably between  themselves.  Any unresolved disputes
arising between the parties  relating to, arising out of or in any way connected
with this  Agreement  or any term or condition  hereof,  or the  performance  by
either party of its obligations  hereunder,  whether before or after termination
of this Agreement, shall be finally resolved by binding arbitration.  Whenever a
party shall decide to institute arbitration  proceedings,  it shall give written
notice to that effect to the other  party.  The party  giving such notice  shall
refrain from instituting the arbitration  proceedings for a period of sixty (60)
days  following  such  notice  The  arbitration  shall  be  held  in San  Diego,
California  according  to the  rules  of the  American  Arbitration  Association
("AAA")  applicable  to  commercial  securities  matters  of  this  nature.  The
arbitration  shall be  conducted  by a panel of three  arbitrators  appointed in
accordance  with AAA rules;  provided,  however,  that each party  shall  within
thirty (30) days after the  institution of the arbitration  proceedings  appoint
one  arbitrator  with  the  third  arbitrator  being  chosen  by the  other  two
arbitrators.  If only one party  appoints an  arbitrator,  then such  arbitrator
shall be entitled to act as the sole arbitrator to resolve the controversy.  Any
arbitration  hereunder  shall  be  conducted  in the  English  language  and the
arbitrator(s)  shall apply the law set forth in Section 5.08. All  arbitrator(s)
eligible to conduct the arbitration must agree to render their opinion(s) within
thirty (30) days of the final arbitration  hearing. The arbitrator(s) shall have
the  authority  to grant  injunctive  relief and  specific  performance,  and to
allocate  between the parties the costs of arbitration in such equitable  manner
as he determines;  provided,  however,  that each party shall bear its own costs
and  attorney's  and witness'  fees.  Notwithstanding  the terms of this Section
5.14,  a party  shall also have the right to obtain  prior to the  arbitrator(s)
rendering the arbitration  decision,  provisional  remedies including injunctive
relief or specific  performance from a court having  jurisdiction  thereof.  The
arbitrator(s) will, upon the request of either party, issue a written opinion of
the findings of fact and  conclusions of law and shall deliver a copy to each of
the parties. Decisions of the arbitrator(s) shall be final and binding on all of
the  parties.  Judgment  on the award so  rendered  may be  entered in any court
having jurisdiction thereof.
<PAGE>

       The execution  hereof by Purchaser shall constitute a contract between us
for the uses and  purposes  hereinabove  set forth,  and this  Agreement  may be
executed in any number of counterparts,  each executed counterpart  constituting
an original but all together only one agreement.

                                        THE IMMUNE RESPONSE CORPORATION


                                        By /S/ DENNIS J. CARLO


                                        By /S/ CHARLES J. CASHION



ACCEPTED AND AGREED TO AS OF THE DAY AND YEAR AFORESAID.

                                        PURCHASER:
                                        AGOURON PHARMACEUTICALS, INC


                                        By /S/ PETER JOHNSON
                                        Peter Johnson
                                        President and Chief Executive Officer


                                        By /S/ GARY FRIEDMAN
                                        Gary Friedman
                                        Secretary