<PAGE>

                                                                    EXHIBIT 4.18

      THIS WARRANT AND THE SHARES OF COMMON STOCK THAT ARE ISSUABLE UPON
      EXERCISE OF THE WARRANT MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR
      OTHERWISE TRANSFERRED UNLESS SUCH TRANSFER IS REGISTERED OR QUALIFIED
      UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND APPLICABLE STATE
      SECURITIES LAWS OR UNLESS THE COMPANY RECEIVES AN OPINION OF COUNSEL OR
      OTHER EVIDENCE REASONABLY SATISFACTORY TO IT TO THE EFFECT THAT SUCH
      REGISTRATION AND QUALIFICATION ARE NOT REQUIRED.

      IN ADDITION, UNTIL THE FIRST ANNIVERSARY OF THE EFFECTIVE DATE OF
      POST-EFFECTIVE AMENDMENT NO. 1 TO THE REGISTRATION STATEMENT (AS DEFINED
      IN THE SELLING AGREEMENT REFERRED TO BELOW) (THE "LOCKUP DATE"), THIS
      WARRANT, AND THE SHARES OF COMMON STOCK THAT ARE ISSUABLE UPON EXERCISE OF
      THE WARRANT, SHALL NOT BE SOLD, TRANSFERRED, ASSIGNED, PLEDGED OR
      HYPOTHECATED BY THE SELLING AGENT, EXCEPT (I) TO ANY NASD MEMBER
      PARTICIPATING IN THE DISTRIBUTION CONTEMPLATED BY THE SELLING AGREEMENT OR
      TO ANY BONA FIDE OFFICER OR PARTNER THEREOF, (II) BY OPERATION OF LAW AND
      (III) BY REASON OF REORGANIZATION OF THE ISSUER.

            WARRANT TO PURCHASE 50,000 SHARES OF CLASS A COMMON STOCK
             (INCLUDING ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                             SELLING AGENT'S WARRANT

                              Dated: April 16, 2003

      This certifies that BNY Capital Markets, Inc. (herein sometimes called the
"Selling Agent") or its permitted transferee (the Selling Agent or any such
transferee is sometimes herein called the "Holder") is entitled to purchase from
BIOPURE CORPORATION, a Delaware corporation (the "Company"), at the price and
during the period as hereinafter specified, 50,000 shares (the "Shares") of
Class A common stock, $0.01 par value per share, of the Company (the "Common
Stock") at a purchase price of $3.45 per share (equal to the closing price of a
Share, as reported on The Nasdaq Stock Market on the trading day immediately
preceding the date of the Closing Date (as defined in the Standby Equity
Distribution Agreement (the "Selling Agreement") dated as of April 16, 2003
between the Holder and the Company) subject to adjustment as described below (as
so adjusted from time to time, the "Exercise Price").

      1. The rights represented by the Selling Agent's Warrant shall be
exercisable at the Exercise Price, and during the periods as follows:

            (a) At any time and from time to time prior to the fifth anniversary
of the Closing Date (the "Expiration Date") inclusive, the Holder shall have the
right to purchase Shares hereunder at the Exercise Price, provided that in no
event shall Shares purchased exceed 10% of the aggregate number of Shares
previously or simultaneously issued and sold under the Selling Agreement.
Subject to the proviso in the immediately preceding sentence, if on the

<PAGE>

Expiration Date, the current fair market value of one share of Common Stock
(determined in the same manner as the "current market price per share of Common
Stock" is to be determined pursuant to Section 8(e) of this Selling Agent's
Warrant) exceeds the Exercise Price, this Warrant shall be deemed to have been
exercised in full on the Expiration Date on a "cashless exercise" basis as
contemplated herein.

            (b) After the Expiration Date, the Holder shall have no right to
purchase all or any portion of the Shares hereunder.

      2.    (a) The rights represented by the Selling Agent's Warrant may be
exercised at any time within the period above specified, in whole or in part, by
(i) the surrender of the Selling Agent's Warrant (with the purchase form at the
end hereof properly executed) at the principal executive office of the Company
(or such other office or agency of the Company as it may designate by notice in
writing to the Holder at the address of the Holder appearing on the books of the
Company); (ii) payment to the Company of the Exercise Price then in effect for
the number of Shares specified in the above-mentioned purchase form together
with applicable stock transfer taxes, if any; and (iii) delivery to the Company
of a duly executed agreement signed by the person(s) designated in the purchase
form to the effect that such person(s) agree(s) to be bound by the provisions of
Section 6 and subsections (b), (c) and (d) of Section 7 hereof. The Selling
Agent's Warrant shall be deemed to have been exercised, in whole or in part to
the extent specified, immediately prior to the close of business on the date the
Selling Agent's Warrant is surrendered and payment is made in accordance with
the foregoing provisions of this Section 2, and the person or persons in whose
name or names the certificates for the Shares shall be issuable upon such
exercise shall become the holder or holders of record of such Shares at that
time and date. The Shares and the certificates for the Shares so purchased shall
be delivered to the Holder within a reasonable time, not exceeding ten (10)
business days, after the rights represented by this Selling Agent's Warrant
shall have been so exercised.

            (b) Notwithstanding anything to the contrary contained in Section
2(a), the Holder may elect to exercise this Selling Agent's Warrant in whole or
in part on a "cashless exercise basis" by receiving Shares equal to the value
(as determined below) of this Selling Agent's Warrant, or any part hereof, upon
surrender of the Selling Agent's Warrant at the principal office of the Company
together with notice of such election in which event the Company shall issue to
the Holder a number of Shares computed using the following formula:

                                   X = Y(A-B)
                                       ------
                                        A

       Where       X =      the number of Shares to be issued to the Holder;

                   Y =      the number of Shares issuable upon exercise of this
                            Selling Agent's Warrant;

                   A =      the current fair market value of one share of Common
                            Stock (determined in the same manner as the
                            "current market price per share of Common Stock"
                            is to be determined pursuant to Section 8(e) of this
                            Selling Agent's Warrant);

                   B =      the Exercise Price.

                                        2

<PAGE>

      3. Any transfer of this Selling Agent's Warrant shall be effected by the
Holder by (i) executing the form of assignment at the end hereof and (ii)
surrendering the Selling Agent's Warrant for cancellation at the office or
agency of the Company referred to in Section 2 hereof, accompanied by (x) a
written instrument of transfer in form reasonably satisfactory to the Company,
duly executed by the registered Holder thereof or by the duly appointed legal
representative thereof or by a duly authorized attorney-in-fact, (y) a
certificate (signed by an officer of the Holder if the Holder is a corporation)
stating that each transferee is a permitted transferee under this Section 3, and
(z) an opinion of counsel, reasonably satisfactory in form and substance to the
Company, to the effect that this Selling Agent's Warrant or the Shares, as
applicable, may be sold or otherwise transferred without registration under the
Act. Upon original issuance thereof, and until such time as the same shall have
been registered under the Act or sold pursuant to Rule 144 promulgated
thereunder (or any similar rule or regulation), each certificate representing
the Selling Agent's Warrant or any part thereof shall bear the following legend,
unless in the opinion of counsel to the Company such legend is no longer
required by the Act:

            THIS WARRANT AND THE SHARES OF COMMON STOCK THAT ARE ISSUABLE UPON
            EXERCISE OF THE WARRANT MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED
            OR OTHERWISE TRANSFERRED UNLESS SUCH TRANSFER IS REGISTERED OR
            QUALIFIED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND
            APPLICABLE STATE SECURITIES LAWS OR UNLESS THE COMPANY RECEIVES AN
            OPINION OF COUNSEL OR OTHER EVIDENCE REASONABLY SATISFACTORY TO IT
            TO THE EFFECT THAT SUCH REGISTRATION AND QUALIFICATION ARE NOT
            REQUIRED.

Upon any transfer of this Selling Agent's Warrant or any part thereof in
accordance with the first sentence of this Section 3(a), the Company shall
issue, in the name or names specified by the Holder (including the Holder), a
new Selling Agent's Warrant or Warrants of like tenor and representing in the
aggregate rights to purchase the same number of Shares as are purchasable
hereunder at such time.

      4. The Company covenants and agrees that all Shares which may be purchased
hereunder will, upon issuance and delivery against payment therefor of the
requisite purchase price, be duly and validly issued, fully paid and
nonassessable. The Company further covenants and agrees that, during the periods
within which the Selling Agent's Warrant may be exercised, the Company will at
all times have authorized and reserved a sufficient number of shares of its
Common Stock to provide for the exercise of the Selling Agent's Warrant.

      5. The Selling Agent's Warrant shall not entitle the Holder to any voting
rights or other rights, including without limitation notice of meetings of other
actions or receipt of dividends, as a stockholder of the Company.

      6. (a) Except as provided in Section 6(b), the Company shall advise the
Holder or its permitted transferee, whether the Holder holds the Selling Agent's
Warrant or has exercised the Selling Agent's Warrant and holds Shares, by
written notice at least four weeks prior to the filing of any new registration

                                       3

<PAGE>

statement thereto under the Act, covering any equity securities of the Company,
for its own account or for the account of others, except for any registration
statement filed on Form S-4 or S-8 (or other comparable form), and will, during
the five (5) year period from the Closing Date, upon the request of the Holder,
include in any such new registration statement (the "Registration Statement")
such information as may be required to permit a public offering of all or any of
the Shares underlying the Selling Agent's Warrant (the "Registrable
Securities").

            (b) At any time during the five (5) year period beginning on the
Closing Date, a 50% Holder (as defined below) may request, on one occasion, that
the Company register under the Act any and all of the Registrable Securities
held by such 50% Holder, at the Company's expense (except as provided below).
Upon the receipt of any such notice, the Company will promptly, but no later
than four weeks after receipt of such notice, file a post-effective amendment to
any existing registration statement or a new registration statement pursuant to
the Act (such post-effective amendment or new registration statement, a "Demand
Registration Statement"), so that such designated Registrable Securities may be
publicly sold under the Act as promptly as practicable thereafter and the
Company shall, subject to Section 6(h), use reasonable best efforts to cause
such Demand Registration Statement to become effective (including the taking of
such reasonable steps as are necessary to obtain the removal of any stop order)
within 120 days after the receipt of such notice, provided, that such 50% Holder
shall furnish the Company with appropriate information in connection therewith
as the Company may reasonably request in writing. The 50% Holder may, at its
option, request the registration of any of Registrable Securities in a
registration statement made by the Company as contemplated by Section 6(a) or in
connection with a request made pursuant to this Section 6(b), in either case
prior to acquisition of the Shares issuable upon exercise of the Selling Agent's
Warrant. Subject to Section 6(h), within ten days after receiving any such
notice pursuant to this Section 6(b), the Company shall give notice to any other
Holders of the Selling Agent's Warrant, advising that the Company is proceeding
with such Demand Registration Statement and offering to include therein,
pursuant to Section 6(a), the Shares underlying that part of the Selling Agent's
Warrant held by the other Holders, provided that they shall furnish the Company
with such appropriate information (relating to the intentions of such Holders)
in connection therewith as the Company shall reasonably request in writing.

            (c) The term "50% Holder" as used in this Section 6 shall mean the
Holder(s) of at least 50% of the Selling Agent's Warrant and/or the Shares
underlying the Selling Agent's Warrant upon the initial issuance of the Selling
Agent's Warrant, as the same may have been adjusted pursuant to Section 8.

            (d) After the Lockup Date, for so long as the Registrable
Securities included in any Registration Statement or Demand Registration
Statement remain unsold, the Company shall, subject to Section 6(h), (i)
maintain the effectiveness of such Registration Statement or Demand Registration
Statement; (ii) timely file all reports required under the Securities Exchange
Act of 1934, as amended, and the rules and regulations of the Commission
thereunder; (iii) file such post-effective amendments to the Registration
Statement or Demand Registration Statement as may be necessary so that the
Registration Statement or Demand Registration Statement does not contain any
misstatement of a material fact or omit to state any material fact required to
make the statements therein not misleading; (iv) supply prospectuses and such
other documents as any Holder whose Registrable Securities are included in such
Registration Statement or Demand Registration Statement may reasonably request
in order to facilitate the public sale or other disposition of such Registrable
Securities; (v) use its reasonable best efforts to register and qualify any of
the Registrable Securities for sale in such jurisdictions within the

                                       4

<PAGE>

United States (x) as any such Holder designates and (y) with respect to which
the Company obtained a qualification in connection with its initial public
offering, provided that the nothing in this clause (v) shall require the Company
to qualify to do business as a foreign corporation or to file a general consent
to service of process in any jurisdiction in which it is not otherwise so
qualified or required to file such a consent at the time; and (vi) do any and
all other acts and things which may be necessary or desirable to enable any such
Holder to consummate the public sale or other disposition of the Registrable
Securities included in the Registration Statement or Demand Registration
Statement, all at no expense to such Holder or the Selling Agent (except as
provided in the immediately following sentence). All costs and expenses in
connection with any Registration Statement or Demand Registration Statement
shall be borne by the Company, except that the Holder(s) shall bear the fees of
their own counsel and any other advisors retained by them and any underwriting
discounts or sales or other commissions applicable to any of the Registrable
Securities sold by them. In connection with any Registration Statement or Demand
Registration Statement, the Company shall furnish indemnification in the manner
provided in Section 7 hereof, and each Holder whose Registrable Securities are
included therein shall furnish information and indemnification in the manner
provided in Section 7. Subject to Section 6(g), the Company shall have the right
to include additional shares of Common Stock to be issued and sold by the
Company in any Demand Registration Statement.

            (e) Notwithstanding the foregoing set forth in this Section 6, the
Company shall not be required to include in any Registration Statement or any
Demand Registration Statement any Registrable Securities which in the opinion of
counsel to the Company (which opinion is reasonably acceptable to counsel to the
Selling Agent) would be saleable immediately without restriction or limitation
under Rule 144(k) (or its successor) if the Selling Agent's Warrant was
exercised pursuant to Section 2(b) herein.

            (f) If any registration pursuant to this Section 6 is in the form
of an underwritten offering, the Company will select and obtain the investment
banker or investment bankers and manager or managers that will administer the
offering. The Company shall (together with each Holder whose Registrable
Securities are included in such offering) enter into an underwriting agreement
in customary form with the managing underwriter selected for such underwriting.
If any Holder disapproves of the terms of the underwriting, it may elect to
withdraw therefrom by written notice to the Company and the managing
underwriter, and upon such withdrawal the original request of such Holder to
cause Registrable Securities to be registered shall not be deemed to constitute
a request for registration pursuant to Section 6(b), provided that the
withdrawal of one or more Holders shall not affect the determination of whether
any request made pursuant to Section 6(b) was made by a 50% Holder, and provided
further that if all Holders who have requested inclusion of their shares in a
Demand Registration pursuant to Section 6(b) withdraw their Registrable
Securities, then, notwithstanding anything to the contrary in this Selling
Agent's Warrant, any Holders who request registration of Registrable Securities
pursuant to Section 6(b) in the future shall be responsible for and pay all
expenses incurred by the Company in connection with such future registration..

            (g) (i) In the event that any registration pursuant to Section
6(a) shall be in connection with an underwritten offering, and the managing
underwriter determines in good faith and advises in writing that the number of
Registrable Securities to be included in such offering, together with the number
of shares of Common Stock to be included in the Registration Statement by the
Company or other holders of the Company's securities with the right to request
inclusion in the Registration Statement, if any, exceeds the number of shares of
Common Stock

                                       5
<PAGE>

that it is advisable to offer and sell at such time or would interfere with the
successful marketing of the Common Stock covered by the Registration Statement,
then priority for including shares of Common Stock in the Registration
Statement, up to the number advised by the managing underwriter, shall be
allocated first, to the Company and each other person who has requested
inclusion of shares of Common Stock pursuant to a "demand" registration right,
pro rata in proportion to the respective number of shares of Common Stock to be
included by them, and second, to the extent of any remaining capacity as advised
by the managing underwriter, to the Holders requesting registration of their
Registrable Securities and each other person who has requested inclusion of
shares of Common Stock pursuant to a "piggyback" registration right, pro rata in
proportion to the respective number of shares of Common Stock (including
Registrable Securities) to be included by them. (ii) In the event that any
registration pursuant to Section 6(b) shall be in connection with an
underwritten offering, and the managing underwriter determines in good faith and
advises in writing that the number of Registrable Securities to be included in
such offering, together with the number of shares of Common Stock to be included
in the Demand Registration Statement by the Company or other holders of the
Company's securities with the right to request inclusion in the Demand
Registration Statement, if any, exceeds the number of shares of Common Stock
that it is advisable to offer and sell at such time or would interfere with the
successful marketing of the Common Stock covered by the Demand Registration
Statement, then priority for including shares of Common Stock in the Demand
Registration Statement, up to the number advised by the managing underwriter,
shall be allocated first, to the 50% Holder and each other person who has
requested inclusion of shares of Common Stock pursuant to a "demand"
registration right, pro rata in proportion to the respective number of shares of
Common Stock to be included by them, and second, to the extent of any remaining
capacity as advised by the managing underwriter, to the Company and each other
person (including any Holder who is not a 50% Holder and who requests inclusion
of Registrable Securities in the Demand Registration Statement pursuant to
Section 6(a)) who has requested inclusion of shares of Common Stock pursuant to
a "piggyback" registration right, pro rata in proportion to the respective
number of shares of Common Stock (including Registrable Securities) to be
included by them.

            (h) In any registration initiated by the Company or by any person
having "demand" registration rights (other than a 50% Holder exercising such
rights pursuant to Section 6(b)) in which Holders request inclusion of their
Registrable Securities pursuant to Section 6(a), if at any time after giving
notice of its intention to register securities and prior to the effective date
of the Registration Statement the Company or such other person shall determine
for any reason not to register or to delay registration of it securities, the
Company may, at its election, give written notice of such determination to each
Holder that has requested inclusion of Registrable Securities in the
Registration Statement and (x) in the case of a determination not to register,
shall be relieved of its obligation to register any Registrable Securities in
connection with such registration and (y) in the case of a determination to
delay registering, shall be permitted to delay registering any Registrable
Securities for the same period as the delay in registering such other
securities. If (i) at any time when a prospectus relating to Registrable
Securities is required to be delivered under the Act, the Company discovers
that, or any event occurs as a result of which, the prospectus (including any
supplement thereto) included in any Registration Statement or Demand
Registration Statement, as then in effect, includes an untrue statement of a
material fact or omits to state any material fact required to be stated therein
or necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading, or (ii) the Commission issues any
stop order suspending the effectiveness

                                       6
<PAGE>

of any Registration Statement or proceedings are initiated or threatened for
that purpose, then the Company shall promptly deliver a written notice to such
effect to each Holder whose Registrable Securities are included in such
Registration Statement or Demand Registration Statement, and each such Holder
shall immediately upon receipt of such notice discontinue its disposition of
Registrable Securities pursuant to such Registration Statement or Demand
Registration Statement until its receipt of the copies of the supplemented or
amended prospectus contemplated by the immediately following sentence and, if so
directed by the Company, shall deliver to the Company (at the Company's expense)
all copies, other than permanent file copies, then in such Holder's possession
of the prospectus or prospectus supplement relating to such Registrable
Securities current at the time of receipt of such notice. As promptly as
practicable following the event or discovery referred to in clause (i) of the
immediately preceding sentence, the Company shall prepare and furnish to the
Holders whose Registrable Securities are included in such Registration Statement
or Demand Registration Statement a reasonable number of copies of an amendment
or supplement of such prospectus so that, as thereafter delivered to purchasers
of such Registrable Securities, such prospectus shall not include an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading. Notwithstanding
anything to the contrary in this Section 6 if the filing or maintenance of any
Registration Statement or Demand Registration Statement would require the
Company to make a disclosure that would, in the reasonable judgment of the
Company's Board of Directors, have a material adverse effect on the business,
operations, properties, prospects or financial condition of the Company or on
pending or imminent transactions, the Company shall have the right, exercisable
for a period not to exceed in the aggregate 45 consecutive calendar days in any
period of twelve consecutive months (the "Blackout Period") upon written notice
to the Holders, to delay the filing of any Registration Statement or Demand
Registration Statement or of any amendment thereto, to suspend its obligation to
maintain the effectiveness of any Registration Statement or Demand Registration
Statement and to suspend the use of any prospectus or prospectus supplement in
connection with any Registration Statement or Demand Registration Statement.
Each Holder agrees that upon receipt of any such notice from the Company, it
shall immediately cease all efforts to dispose of Registrable Securities
pursuant to such Registration Statement or Demand Registration Statement until
such time as the Company shall notify it of the end of such restrictions or, if
earlier, the expiration of the Blackout Period.

      7. (a) Whenever pursuant to Section 6 a Registration Statement or
Demand Registration Statement relating to any Shares issued upon exercise of the
Selling Agent's Warrant is filed under the Act, amended or supplemented, the
Company will indemnify and hold harmless each Holder of the securities covered
by such Registration Statement or Demand Registration Statement, amendment or
supplement (such Holder being hereinafter called the "Distributing Holder"), and
each person, if any, who controls (within the meaning of the Act) the
Distributing Holder, and each underwriter (within the meaning of the Act) of
such securities and each person, if any, who controls (within the meaning of the
Act) any such underwriter, against any losses, claims, damages or liabilities,
joint or several, to which the Distributing Holder, any such controlling person
or any such underwriter may become subject, under the Act or otherwise, insofar
as such losses, claims, damages or liabilities, or actions in respect thereof,
arise out of or are based upon any untrue statement or alleged untrue statement
of any material fact contained in any such Registration Statement or Demand
Registration Statement as declared effective or any final prospectus
constituting a part thereof or any amendment or supplement thereto, or arise out
of or are based upon the omission or the alleged omission to state therein a
material fact required

                                       7
<PAGE>

to be stated therein or necessary to make the statements therein not misleading
and will reimburse the Distributing Holder or such controlling person or
underwriter for any legal or other expense reasonably incurred by them in
connection with investigating or defending any such loss, claim, damage,
liability or action; provided, however, that the Company will not be liable in
any such case to the extent that any such loss, claim, damage or liability
arises out of or is based upon an untrue statement or alleged untrue statement
or omission or alleged omission made in said Registration Statement or Demand
Registration Statement, said preliminary prospectus, said final prospectus or
said amendment or supplement in reliance upon and in conformity with written
information furnished by such Distributing Holder or any other Distributing
Holder for use in the preparation thereof and provided further, that the
indemnity agreement provided in this Section 7(a) with respect to any
preliminary prospectus shall not inure to the benefit of any Distributing
Holder, controlling person of such Distributing Holder, underwriter or
controlling person of such underwriter from whom the person asserting any
losses, claims, charges, liabilities or litigation based upon any untrue
statement or alleged untrue statement of a material fact or omission or alleged
omission to state therein a material fact, received such preliminary prospectus,
if a copy of the prospectus in which such untrue statement or alleged untrue
statement or omission or alleged omission was corrected has not been sent or
given to such person within the time required by the Act and the rules and
regulations of the Commission thereunder.

            (b) The Distributing Holder will indemnify and hold harmless the
Company, each of its directors, each of its officers who have signed said
Registration Statement or Demand Registration Statement and such amendments and
supplements thereto, and each person, if any, who controls the Company (within
the meaning of the Act) against any losses, claims, damages or liabilities,
joint or several, to which the Company or any such director, officer or
controlling person may become subject, under the Act or otherwise, insofar as
such losses, claims, damages or liabilities, or actions in respect thereof,
arise out of or are based upon any untrue or alleged untrue statement of any
material fact contained in said Registration Statement or Demand Registration
Statement, said preliminary prospectus, said final prospectus, or said amendment
or supplement, or arise out of or are based upon the omission or the alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, in each case to the
extent, but only to the extent, that such loss, claim, damage or liability
arises out of or is based upon an untrue statement or alleged untrue statement
or omission or alleged omission made in said Registration Statement or Demand
Registration Statement, said preliminary prospectus, said final prospectus or
said amendment or supplement in reliance upon and in conformity with written
information furnished by such Distributing Holder for use in the preparation
thereof; and will reimburse the Company or any such director, officer or
controlling person for any legal or other expenses reasonably incurred by them
in connection with investigating or defending any such loss, claim, damage,
liability or action.

            (c) Promptly after receipt by an indemnified party under this
Section 7 of notice of the commencement of any action, such indemnified party
will, if a claim in respect thereof is to be made against an indemnifying party
under this Section 7, notify the indemnifying party in writing of the
commencement thereof, but the omission so to notify the indemnifying party will
not relieve it from any liability which it may have to any indemnified party for
indemnity or contribution to the extent it is not prejudiced as a proximate
result of such failure. In case any such action is brought against any
indemnified party, and such indemnified party seeks or intends to seek indemnity
from an indemnifying party, the indemnifying party will be

                                       8
<PAGE>

entitled to participate in, and, to the extent that it shall elect, jointly with
any other indemnifying party similarly notified, by written notice delivered to
the indemnified party promptly after receiving the aforesaid notice from such
indemnified party, to assume the defense thereof with counsel reasonably
satisfactory to such indemnified party; provided, however, if the defendants in
any such action include both the indemnified party and the indemnifying party
and the indemnified party shall have reasonably concluded that a conflict may
arise between the positions of the indemnifying party and the indemnified party
in conducting the defense of any such action or that there may be legal defenses
available to it and/or other indemnified parties which are different from or
additional to those available to the indemnifying party, the indemnified party
or parties shall have the right to select separate counsel to assume such legal
defenses and to otherwise participate in the defense of such action on behalf of
such indemnified party or parties. Upon receipt of notice from the indemnifying
party to such indemnified party of such indemnifying party's election so to
assume the defense of such action and approval by the indemnified party of
counsel (which approval shall not be unreasonably withheld or delayed), the
indemnifying party will not be liable to such indemnified party under this
Section 7 for any legal or other expenses subsequently incurred by such
indemnified party in connection with the defense thereof unless: (i) the
indemnified party shall have employed separate counsel in accordance with the
proviso to the next preceding sentence (it being understood, however, that the
indemnifying party shall not be liable for the expenses of more than one
separate counsel (together with local counsel), representing the indemnified
parties who are parties to such action); (ii) the indemnifying party shall not
have employed counsel satisfactory to the indemnified party to represent the
indemnified party within a reasonable time after notice of commencement of the
action; or (iii) the indemnifying party has authorized the employment of counsel
for the indemnified party satisfactory to the indemnified party at the expense
of the indemnifying party, in each of which cases the fees and expenses of
counsel shall be at the expense of the indemnifying party.

            (d) The indemnifying party under this Section 7 shall not be
liable for any settlement of any proceeding effected without its written
consent, which consent shall not be unreasonably withheld or delayed, but if
settled with such consent or if there be a final judgment for the plaintiff, the
indemnifying party agrees to indemnify the indemnified party against any loss,
claim, damage, liability or expense by reason of such settlement or judgment. No
indemnifying party shall, without the prior written consent of the indemnified
party, effect any settlement, compromise or consent to the entry of judgment in
any pending or threatened action, suit or proceeding in respect of which any
indemnified party is or could have been a party and indemnity was or could have
been sought hereunder by such indemnified party, unless such settlement,
compromise or consent includes: (i) an unconditional release of such indemnified
party from all liability on claims that are the subject matter of such action,
suit or proceeding; and (ii) does not include a statement as to or an admission
of fault, culpability or a failure to act by or on behalf of any indemnified
party.

            (e) Any losses, claims, damages, liabilities or expenses for which
an indemnified party is entitled to indemnification or contribution under this
Section 7 shall be paid by the indemnifying party to the indemnified party as
such losses, claims, damages, liabilities or expenses are incurred, but in all
cases, no later than forty-five (45) days after invoice to the indemnifying
party.

            (f) If the indemnification provided for in this Section 7 is
unavailable to or insufficient to hold harmless an indemnified party under
Section 7(a) or 7(b) above in respect of

                                       9
<PAGE>

any losses, claims, damages or liabilities (or actions or proceedings in respect
thereof) then each indemnifying party shall contribute to the aggregate amount
paid or payable by such indemnified party in such proportion as is appropriate
to reflect the relative fault of such indemnifying party on the one hand and the
Distributing Holder on the other in connection with the statements or omissions
which resulted in such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof), as well as any other relevant equitable
considerations. The relative fault shall be determined by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission or alleged omission to state a material fact relates to
information supplied by the Company or the "control" stockholders on the one
hand or the Distributing Holder on the other and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission.

      The Company and each Distributing Holder agree that it would not be just
and equitable if contributions pursuant to this Section 7(f) were determined by
pro rata allocation or by any other method of allocation which does not take
account of the equitable considerations referred to above in this Section 7(f).
The amount paid or payable by an indemnified party as a result of the losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
referred to above in this Section 7(f) shall be deemed to include any legal or
other expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim. Notwithstanding the
provisions of this Section 7(f): (i) each Distributing Holder shall not be
required to contribute any amount in excess of the amount of proceeds received
by such Holder from sale(s) of such Holder's Shares pursuant to the Registration
Statement or Demand Registration Statement; and (ii) no person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.

      8. The Exercise Price in effect at the time and the number and kind of
securities purchasable upon the exercise of the Warrant shall be subject to
adjustment from time to time upon the happening of certain events as follows:

            (a) In case the Company shall (i) declare a dividend or make a
distribution on its outstanding shares of Common Stock in shares of Common
Stock, (ii) subdivide or reclassify its outstanding shares of Common Stock into
a greater number of shares, (iii) combine or reclassify its outstanding shares
of Common Stock into a smaller number of shares, or (iv) enter into any
transaction whereby the outstanding shares of Common Stock of the Company are at
any time changed into or exchanged for a different number or kind of shares or
other security of the Company or of another corporation through reorganization,
merger, consolidation, liquidation or recapitalization, then appropriate
adjustments in the number of Shares (or other securities for which such Shares
have previously been exchanged or converted) subject to this Selling Agent's
Warrant shall be made and the Exercise Price in effect at the time of the record
date for such dividend or distribution or of the effective date of such
subdivision, combination, reclassification, reorganization, merger,
consolidation, liquidation or recapitalization shall be proportionately adjusted
so that the Holder of this Selling Agent's Warrant exercised after such date
shall be entitled to receive the aggregate number and kind of shares of Common
Stock which, if this Selling Agent's Warrant had been exercised by such Holder
immediately prior to such date, the Holder would have been entitled to receive
upon such dividend, distribution, subdivision, combination, reclassification,
reorganization, merger, consolidation, liquidation or recapitalization. For
example, if the Company declares a 2 for 1 stock distribution and the Exercise
Price hereof immediately prior to such event was $5.00 per Share and the number
of

                                       10

<PAGE>

Shares issuable upon exercise of this Selling Agent's Warrant was 10,000, the
adjusted Exercise Price immediately after such event would be $2.50 per Share
and the adjusted number of Shares issuable upon exercise of this Selling Agent's
Warrant would be 20,000. Such adjustment shall be made successively whenever any
event listed above shall occur.

            (b) In case the Company shall fix a record date for the issuance
of rights or warrants to all holders of its Common Stock entitling them to
subscribe for or purchase shares of Common Stock (or securities convertible into
Common Stock) at a price (the "Subscription Price") (or having a conversion
price per share) less than the current market price per share of Common Stock
basis as determined pursuant to Section 8(e) on such record date, the Exercise
Price shall be adjusted so that the same shall equal the price determined by
multiplying the same by a fraction, the numerator of which shall be the sum of
the number of shares of Common Stock outstanding on the record date mentioned
below and the number of additional shares of Common Stock which the aggregate
offering price of the total number of shares of Common Stock so offered (or the
aggregate conversion price of the convertible securities so offered) would
purchase at the current market price per share of Common Stock on such record
date, and the denominator of which shall be the sum of the number of shares of
Common Stock outstanding on the record date mentioned below and the number of
additional shares of Common Stock offered for subscription or purchase (or into
which the convertible securities so offered are convertible). Such adjustment
shall be made successively whenever such rights or warrants are issued and shall
become effective immediately after the record date for the determination of
stockholders entitled to receive such rights or warrants; and to the extent that
shares of Common Stock are not delivered (or securities convertible into Common
Stock are not delivered) after the expiration of such rights or warrants the
Exercise Price shall be readjusted to the Exercise Price which would then be in
effect had the adjustments made upon the issuance of such rights or warrants
been made upon the basis of delivery of only the number of shares of Common
Stock (or securities convertible into Common Stock) actually delivered. This
Section 8(b) shall not apply to the occurrence of a "Distribution Date" under
the Rights Agreement.

            (c) In case the Company shall hereafter distribute to all holders
of its Common Stock evidences of its indebtedness or assets (excluding cash
dividends or distributions and dividends or distributions referred to in Section
8(a) above) or subscription rights or warrants (excluding those referred to in
Section 8(b) above), then in each such case the Exercise Price shall be adjusted
by multiplying the same, by a fraction, the numerator of which shall be the
total number of shares of Common Stock then outstanding multiplied by the
current market price per share of Common Stock (as defined in Section 8(e)
below), less the fair market value (as determined by the Company's Board of
Directors) of said assets, or evidences of indebtedness so distributed or of
such rights or warrants, and the denominator of which shall be the total number
of shares of Common Stock outstanding multiplied by such current market price
per share of Common Stock. Such adjustment shall be made whenever any such
distribution is made and shall become effective immediately after the record
date for the determination of stockholders entitled to receive such distribution
and to the extent that any subscription rights or warrants are not exercised
before the expiration of such rights or warrants the Exercise Price shall be
readjusted to the Exercise Price which would then be in effect had the
adjustments made upon the issuance of such rights or warrants been made upon the
basis of delivery of only the number of rights or warrants actually exercised.
This Section 8(c) shall not apply to the occurrence of a "Distribution Date"
under the Rights Agreement.

                                       11

<PAGE>

            (d) Whenever the Exercise Price payable upon exercise of the
Selling Agent's Warrant is adjusted pursuant to Sections 8(a), (b) or (c) above,
the number of Shares purchasable upon exercise of this Selling Agent's Warrant
shall simultaneously be adjusted by multiplying the number of Shares issuable
upon exercise of this Selling Agent's Warrant by the Exercise Price in effect
immediately prior to such adjustment and dividing the product so obtained by the
Exercise Price, as adjusted.

            (e) For the purpose of any computation under Section 8(c) above,
the current market price per share of Common Stock at any date shall be deemed
to be the closing price on the Trading Day immediately preceding the date as of
which the current market price is being determined, provided that if the Common
Stock is not then listed on any market or exchange, then the current market
price shall be the average of the closing bid prices for the Common Stock on the
OTC Bulletin Board, or, if such is not available, the Pink Sheets LLC (formerly
the National Quotation Bureau), or otherwise the average of the closing bid
prices for the Common Stock quoted by two market-makers of the Common Stock, or
otherwise such Market Price shall be the fair market value of one share of
Common Stock as reasonably determined in good faith by the Corporation and the
Holders. "Trading Day" shall mean any day on which the principal United States
securities exchange or trading market on which the Common Stock is listed or
traded (the "Principal Market") as reported by Bloomberg Financial Markets is
open for trading. "Closing price" shall mean the last sale price for the Common
Stock on the Principal Market on any particular Trading Day.

            (f) No adjustment in the Exercise Price shall be required unless
such adjustment would require an increase or decrease of at least five cents
($0.05) in such price; provided, however, that any adjustments which may by
reason of this Section 8(f) are not required to be made shall be carried forward
and taken into account in any subsequent adjustment required to be made
hereunder. All calculations under this Section 8 shall be made to the nearest
cent or to the nearest one-hundredth of a share, as the case may be. Anything in
this Section 8 to the contrary notwithstanding, the Company shall be entitled,
but shall not be required, to make such changes in the Exercise Price, in
addition to those required by this Section 8, as it shall determine, in its sole
discretion, to be advisable in order that any dividend or distribution in shares
of Common Stock, or any subdivision, reclassification or combination of Common
Stock, hereafter made by the Company shall not result in any Federal income tax
liability to the holders of the Common Stock or securities convertible into
Common Stock.

            (g) Whenever the Exercise Price is adjusted, as herein provided,
the Company shall promptly cause a notice setting forth the adjusted Exercise
Price and adjusted number of Shares issuable upon exercise of the Selling
Agent's Warrant to be mailed to the Holder, at its address set forth herein, and
shall cause a certified copy thereof to be mailed to the Company's transfer
agent, if any. The Company may retain a firm of independent certified public
accountants selected by the Board of Directors (who may be the regular
accountants employed by the Company) to make any computation required by this
Section 8, and a certificate signed by such firm shall be conclusive evidence of
the correctness of such adjustment.

            (h) In the event that at any time, as a result of an adjustment
made pursuant to the provisions of this Section 8, the Holder of the Selling
Agent's Warrant thereafter shall become entitled to receive any shares of the
Company other than Common Stock, thereafter the number of such other shares so
receivable upon exercise of the Selling Agent's Warrant shall be subject to
adjustment from time to time in a manner and on terms as nearly equivalent as

                                       12

<PAGE>

practicable to the provisions with respect to the Common Stock contained in
Sections 8(a) to (f), inclusive, above.

      9. This Selling Agent's Warrant shall be governed by and in accordance
with the laws of the State of Delaware without regard to conflicts of laws
principles thereof.

      10. In case of any consolidation of the Company with, or merger of the
Company into, any other entity, or in case of any sale or conveyance of all or
substantially all of the assets of the Company other than in connection with a
plan of complete liquidation of the Company at any time prior to the Expiration
Date, then as a condition of such consolidation, merger or sale or conveyance,
the Company shall give written notice of consolidation, merger, sale or
conveyance to the Holder and, from and after the effective date of such
consolidation, merger, sale or conveyance the Selling Agent's Warrant shall
represent only the right to receive the consideration that would have been
issuable in respect of the Shares underlying the Selling Agent's Warrant in such
consolidation, merger, sale or conveyance had the Selling Agent's Warrant been
exercised in full immediately prior to such effective time and the Holder shall
have no further rights under this Selling Agent's Warrant other than the right
to receive such consideration.

                                       13

<PAGE>

      IN WITNESS WHEREOF, the Company has caused this Selling Agent's Warrant to
be signed by its duly authorized officers under its corporate seal, and this
Selling Agent's Warrant to be dated April 16, 2003.

                                                  BIOPURE CORPORATION

                                                  By: _______________________
                                                      Ronald F. Richards
                                                      Chief Financial Officer

Attest:

_____________________
Jane Kober
Secretary

                                       14

<PAGE>

                                  PURCHASE FORM

                  (To be signed only upon exercise of Warrant)

      The undersigned, the holder of the foregoing Selling Agent's Warrant,
hereby irrevocably elects to exercise the purchase rights represented by such
Warrant for, and to purchase thereunder, _______________ Shares of Class A
Common Stock, $0.01 par value per share (the "Shares"), of BIOPURE CORPORATION
and either

      [ ]   tenders herewith payment of the aggregate Exercise Price in respect
            of the Shares in full, in the amount of $_________; or

      [ ]   elects pursuant to Section 2(b) of such Warrant to convert such
            Warrant into Common Stock on a cashless exercise basis; and

requests that the certificates for the Shares issued in the name(s) of, and
delivered to _________________, whose address(es) is (are):

Dated:  _______________, ____

                                                By:__________________________

                                                _____________________________

                                                _____________________________
                                                Address

<PAGE>

                                  TRANSFER FORM

          (To be signed only upon transfer of Selling Agent's Warrant)

      For value received, the undersigned hereby sells, assigns, and transfers
unto ____________________ the right to purchase Shares represented by the
foregoing Selling Agent's Warrant to the extent of __________ Shares, and
appoints _________________________ attorney to transfer such rights on the books
of Biopure Corporation, with full power of substitution in the premises. The
undersigned believes that each transferee is a permitted transferee under
Section 3 of the Selling Agent's Warrant.

Dated:  _______________, ____

                                                By:__________________________

                                                _____________________________

                                                _____________________________
                                                Address

In the presence of:

_________________________