Patent Security Agreement - Biopure Corp. and Pharmacia & Upjohn Inc.
                            PATENT SECURITY AGREEMENT
      This PATENT SECURITY AGREEMENT ("Agreement") is made this 8th day of
October, 1996, by and between Biopure Corporation, a Delaware corporation,
having its principal office at 11 Hurley Street, Cambridge, Massachusetts 02141
("Grantor"), and Pharmacia & Upjohn, Inc., a Delaware corporation, having its
principal office at 7000 Portage Road, Kalamazoo, Michigan 49001 ("Grantee").
            WHEREAS, Grantor is the owner of the U.S. patents and patent
applications listed on the attached Schedule A (collectively the "Patents");
            WHEREAS, Grantee has extended a loan to Grantor pursuant to the
terms and conditions of that certain Promissory Note dated the date hereof
("Note") made by Grantor in favor of Grantee;
            WHEREAS, under a Security Agreement dated the date hereof ("Security
Agreement") between Grantor and Grantee, Grantor has granted to Grantee a
security interest in certain of its assets (including the Patents) to secure the
performance of the obligations of Grantor under the Note; and
            WHEREAS, Grantor and Grantee by this instrument seek to confirm and
make a record of the grant of a security interest in the Patents.
            NOW, THEREFORE, for good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, Grantor does hereby acknowledge that
it has granted to Grantee a security interest in all of Grantor's right, title
and interest in, to, and under the Patents. Grantor also acknowledges and
confirms that the rights and remedies of Grantee with respect to the security
interests in the Patents granted hereby are more fully set forth in the Note and
the Security Agreement, the terms and provisions of which are incorporated
herein by reference.
BIOPURE CORPORATION                     PHARMACIA & UPJOHN, INC.
By: /s/ Brian A. Lajoie                 By: /s/ Robert G. Kramer
    ----------------------                  ---------------------
    Name:  Brian A. Lajoie                  Name:
    Title: V.P. - Finance                   Title:
STATE OF Massachussets   )
                         )  SS:
COUNTY OF Middlesex      )
Subscribed and sworn to this 7th day of October, 1996.
/s/ Hazel V. Forney
------------------------
Notary Public
My Commission Expires: Jan 4, 2002
<PAGE>   3
                                   SCHEDULE A
                    U.S. Patents and U.S. Patent Applications
<TABLE>
<CAPTION>
Patent No.                          Title                      Issue Date
----------                          -----                      ----------
<S>                     <C>                                    <C>
5,084,558               Extra Pure Semi-Synthetic              01/28/92
                        Blood Substitute
5,296,465               Extra Pure Semi-Synthetic              03/22/94
                        Blood Substitute
5,095,765               Sample Valve for Sterile               03/17/92
                        Processing
5,295,944               Improved Method for Treating a         03/22/94
                        Tumor with Ionizing Radiation
<CAPTION>
Patent Application No.              Title                      Filing Date
----------------------              -----                      -----------
<S>                     <C>                                    <C>
08/209,949              Ultra Pure Hemoglobin                  03/11/94
                        Solutions and Blood
                        Substitutes
08/333,623              Enzymatic Production of                11/02/94
                        7-Amino Cephalosporanic Acid
08/477,916              Method for Separating                  06/07/95
                        Unmodified Hemoglobin from
                        Cross-Linked Hemoglobin
08/360,143              Chlorination of Cephalexin             12/20/94
                        with Chioroperoxidase from
                        Rathayibacter
08/409,337              Method for Oxygenating Tissue          03/23/95
                        Having Reduced Red Blood Cell
                        Flow
08/458,916              Method for Producing Ultrapure         06/02/95
                        Stable Polymerized Hemoglobin
                        Blood-Substitute
08/484,775              Method for Producing a Stable          06/07/95
                        Polymerized Hemoglobin Blood-
                        Substitute
</TABLE>
                                       -2-
<PAGE>   4
<TABLE>
<CAPTION>
Patent Application No.              Title                      Filing Date
----------------------              -----                      -----------
<S>                     <C>                                    <C>
08/478,004              Method for Producing a Stable          06/07/95
                        Polymerized Hemoglobin Blood-
                        Substitute
08/487,288              Stable Polymerized Hemoglobin          06/07/95
                        and Use Thereof
08/620,296              Stable Polymerized Hemoglobin          03/22/96
                        and Use Thereof
08/471,583              Method for Preserving a                06/07/95
                        Hemoglobin Blood Substitute
08/473,497              Method for Separating                  06/07/95
                        Hemoglobin
08/360,149              Enzymatic Halogenation of              12/20/94
                        Cephalexin to Produce Cefaclor
                        and Other Halogenated Products
08/475,899              Separation of Polymerized from         06/07/95
                        Unpolymerized Hemoglobin on
                        Hydroxyapatite Using HPLC
08/673,147              A Method for Chromatographic           07/01/96
                        Removal of Prions
08/094,501              Method for Treating a Tumor            07/20/93
                        with a Chemotherapeutic Agent
08/477,110              Method for Treating a Tumor            06/07/95
                        with a Chemotherapeutic Agent
</TABLE>
                                       -3-
<PAGE>   5
================================================================================
FORM PTO-1595                                        U.S. DEPARTMENT OF COMMERCE
(Rev. 6-93)                                          Patent and Trademark Office
                          RECORDATION FORM COVER SHEET
                                  PATENTS ONLY
                                                Attorney Docket No.: 014877-0000
--------------------------------------------------------------------------------
To the Commissioner of Patents and Trademarks:
Please record the attached original documents
  or copy thereof.                                          ATTN: BOX ASSIGNMENT
--------------------------------------------------------------------------------
1. Name of conveying party(ies):
   Biopure Corporation
   Additional name(s) of conveying party(ies) attached?
   |_| Yes   |X| No
--------------------------------------------------------------------------------
2. Name and address of receiving party(ies):
   Name: Pharmacia & Upjohn, Inc.
   Internal Address:
   Street Address: 7000 Portage Road,
   City: Kalamazoo
   State: Michigan            Zip: 49001
Additional name(s) & address(es) attached?
|_| Yes   |X| No
--------------------------------------------------------------------------------
3. Nature of conveyance:
   |_| Assignment                         |_| Merger
   |X| Security Agreement                 |_| Change of Name
   |_| Other
Execution Date: October 7, 1996
--------------------------------------------------------------------------------
4. Application number(s) or patent number(s):
   If this document is being filed together with a new application the execution
   date of the application is:
   A. Patent Application No.(s) 08/209,949, 08/333,623, 08/477,916, 08/360,143,
                                08/409,337, 08/458,916, 08/484,775, 08/478,004,
                                08/487,288, 08/620,296, 08/471,583, 08/473,497,
                                08/360,149, 08/475,899, 08/673,147, 08/094,501
                                and 08/477,110
   B. Patent No.(s) 5,084,558, 5,296,465, 5,095,765 and 5,295,944
Additional numbers attached: |_| Yes   |X| No
--------------------------------------------------------------------------------
5. Name and address of party to whom correspondence
   concerning document should be mailed:
 Name:                  Mr. Matthew T. Bailey
 Internal Address:      Morgan, Lewis & Bockius LLP
 Street Address:        1800 M Street, N.W.
 City: Washington       State: D.C.       Zip: 20036
--------------------------------------------------------------------------------
6. Total number of applications and patents involved: 21
--------------------------------------------------------------------------------
7. Total fee (37 C.F.R ss.3.41): $840.00
   |X| Enclosed
   |_| Authorized to be charged  to deposit account 13-4520
--------------------------------------------------------------------------------
8. Deposit account number: 13-4520
   Attach duplicate of page if paying by deposit account
================================================================================
9. Statement and Signature
      To the best of my knowledge and belief, the foregoing information is true
      and correct and any attached copy is a true copy of the original document.
      Matthew T. Bailey             /s/ Matthew T. Bailey      October 11, 1996
--------------------------------    ---------------------      ----------------
      Name of Person Signing              Signature                  Date
       Total number of pages including cover sheet, attachments and documents: 4
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