<PAGE>   1
                                                                   EXHIBIT 99.03

PROXY

                PROXY FOR 1999 SPECIAL MEETING OF STOCKHOLDERS OF
                         RIBI IMMUNOCHEM RESEARCH, INC.

The Proxy is Solicited on Behalf of the Board of Directors for the Special
Meeting of Stockholders to be Held September 23, 1999.


        The undersigned stockholder of Ribi ImmunoChem Research, Inc., a
Delaware corporation (the "Company"), hereby acknowledges receipt of the Notice
of Special Meeting of Stockholders and joint proxy statement/prospectus, each
dated August 12, 1999, and hereby appoints Robert Ivy and Ronald Kullick or
each of them, proxies and attorneys-in-fact, with full power to each of
substitution, on behalf and in the name of the undersigned, to represent the
undersigned at the Special Meeting of Stockholders of the Company to be held on
September 23, 1999, at 10:00 a.m., local time, at Hamilton City Hall/Community
Center which is located at 223 S. 2nd Street, Hamilton, Montana 59840, and at
any postponement or adjournment thereof, and to vote all the stock of the
Company which the undersigned would be entitled to vote if then and there
personally present, on the matters set forth in the Notice of Special Meeting
of Stockholders and joint proxy statement/prospectus.

THIS PROXY WILL BE VOTED AS DIRECTED OR, IF NO CONTRARY DIRECTION IS INDICATED,
WILL BE VOTED "FOR" EACH OF THE PROPOSALS SET FORTH IN THE NOTICE OF SPECIAL
MEETING OF STOCKHOLDERS AND JOINT PROXY STATEMENT/PROSPECTUS, AND, IN THEIR
DISCRETION, THE PROXIES ARE AUTHORIZED TO VOTE ON SUCH OTHER MATTER OR MATTERS
AS MAY PROPERLY COME BEFORE THE MEETING AND ANY POSTPONEMENTS OR ADJOURNMENTS
THEREOF.

PLEASE VOTE, SIGN, DATE AND RETURN THIS PROXY FORM USING THE ENCLOSED ENVELOPE.


                  (Continued and to be signed on reverse side.)

<PAGE>   2

                         Ribi ImmunoChem Research, Inc.

      PLEASE MARK VOTE IN OVAL IN THE FOLLOWING MANNER USING DARK INK ONLY.



        1. Proposal to approve the merger of the Company with and into Corixa
Corporation, a Delaware corporation ("Corixa") whereby, among other things:

        -  each outstanding share of the Company's common stock will be
           converted into the right to receive 0.1685 shares of Corixa common
           stock;

        -  each outstanding option and warrant to purchase shares of the
           Company's common stock that is not terminated as a result of the
           merger will be assumed by Corixa and converted into an option or
           warrant to purchase shares of Corixa common stock;

        -  the Company's stock option plans and option agreements granted to
           employees and directors will be amended; and

        -  each share of the Company's Series A preferred stock that is not
           converted into the Company's common stock prior to the merger will be
           redeemed by the Company.

                - FOR             - AGAINST               - ABSTAIN



NOTE: This Proxy should be marked, dated, signed by the stockholder(s) exactly
as his or her name appears hereon, and returned in the enclosed envelope.

               Please sign exactly as name appears hereon. When shares are held
               by joint tenants, both should sign. When signing as attorney,
               executor, administrator, trustee or guardian, please give full
               title as such. If a corporation, please sign in full corporate
               name by the President or other authorized officer. If a
               partnership, please sign in partnership name by an authorized
               person.

                              YOUR VOTE IS IMPORTANT!

                              PLEASE VOTE, SIGN, DATE AND RETURN THIS PROXY FORM
                              USING THE ENCLOSED ENVELOPE.

                                        ________________________________________
                                                       Signature


                                        ________________________________________
                                                       Signature

                                        Dated:____________________________, 1999