Document:

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                                                                     Exhibit 4.1

                          REGISTRATION RIGHTS AGREEMENT

         REGISTRATION RIGHTS AGREEMENT (the "Agreement"), dated as of April 2,
2003, by and between RRD International, LLC, a Delaware limited liability
company ("RRD"), and Bioenvision, Inc., a Delaware corporation (the "Comany").

                              PRELIMINARY STATEMENT

         WHEREAS, the Company and RRD have entered into that certain General
Services Agreement, dated as of the date hereof, pursuant to which RRD has
agreed to perform certain services for the Company (the "General Services
Agreement"), in exchange for, in pertinent part, the Company's issuance to RRD
of warrants to purchase one hundred and seventy-five thousand (175,000) shares
(the "Shares") of common stock, par value $0.001 per share (the "Common Stock"),
of the Company, pursuant to a warrant agreement of even date herewith (the
"Warrant Agreement"); and

         WHEREAS, the Company and RRD desire to provide for certain arrangements
with respect to the registration of the Shares under the Securities Act of 1933,
as amended.

         NOW THEREFORE, in consideration of these premises, and the respective
promises and covenants contained herein, the parties hereto agree as follows:

                                   I. ARTICLE

                                   DEFINITIONS

1.1.     Certain Definitions. For purposes of this Agreement, capitalized terms
used herein and not defined elsewhere herein shall have the following meanings:

         "Act" means the United States Securities Act of 1933, as amended, or
any similar federal statute, and the rules and regulations of the Commission
issued under the Act, as they each may, from time to time, be in effect.

         "Affiliate" of any Person shall mean, with respect to such Person, any
other Persont that, directly or indirectly, through one or more intermediaries,
controls, is controlled by or is under common control with such Person.

         "Commission" means the United States Securities and Exchange
Commission, or any other federal agency at the time administering the Act.

         "Common Stock" means the shares of common stock, par value $0.001 per
share, of the Company.

         "Exchange Act" means the United States Securities Exchange Act of 1934,
as amended, or any similar federal statute, and the rules and regulations of the
Commission issued under the Exchange Act, as they each may, from time to time,
be in effect.

         "Indemnified Party" has the meaning described in Section 2.4(c) below.

         "Indemnifying Party" has the meaning described in Section 2.4(c) below.

         "Person" means any individual, corporation, partnership, limited
partnership, joint venture, limited liability company, association, joint stock
company, trust, bank, trust company, unincorporated organization or other
organization or any governmental authority.

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         "Registration Statement" means a registration statement filed by the
Company with the Commission for a public offering and sale of its equity
securities (other than a registration statement on Form S-8 or Form S-4, or
their successors, or any other form for a limited purpose in which form
Registrable Shares may not be included).

         "Registration Expenses" means all expenses incurred by the Company in
complying with Article II, including, without limitation, all registration and
filing fees, exchange listing fees, printing expenses, fees and disbursements of
counsel for the Company, reasonable fees and disbursements of one counsel
selected by RRD (or its successor in interest) up to a maximum of $12,500 in the
aggregate for all registration rights granted hereunder, state Blue Sky fees and
expenses, and the expense of any special audits incident to or required by any
such registration, but excluding underwriting discounts on the Registrable
Shares, selling commissions on the Registrable Shares, transfer taxes and the
fees and expenses of any selling Stockholders', including RRD's own counsel
(except as otherwise provided herein), which shall be borne by the participating
Stockholders in proportion to the number of Registrable Shares offered by each.

         "Registrable Shares" means (i) the Shares, and (ii) any other shares of
Common Stock issued in respect thereof (because of stock splits, stock
dividends, reclassifications, recapitalizations, reorganizations, mergers,
consolidations or sales of assets or similar events); provided, that shares of
Common Stock which are Registrable Shares shall cease to be Registrable Shares
(i) when they have been sold, transferred or otherwise disposed of or exchanged
pursuant to a Registration Statement under the Act, (ii) when such shares are
eligible for resale pursuant to Rule 144(k) (or its successor) or in single
transaction pursuant to Rule 144(e) (or its successor) under the Act without
violation of the applicable volume limitations, or (iii) upon any sale, transfer
or other disposition in any manner to any person or entity which, by virtue of
Section 2.10 of this Agreement, is not entitled to the rights provided by this
Agreement.

         "Stockholders" means RRD and any person or entities to whom the rights
granted under this Agreement are validly transferred by RRD, and their permitted
successors or assigns pursuant to Section 2.10 hereof.

                                   2. ARTICLE

                               REGISTRATION RIGHTS

2.1.   Incidental Registration.

         2.1.1. Subject to Section 2.1.2 and 2.1.3 below, whenever the Company
proposes to file a Registration Statement at any time and from time to time
(including a registration effected by the Company for stockholders other than
the Stockholder) (a "Registration"), it will, prior to such filing, give written
notice to all Stockholders of its intention to do so and, upon the written
request of a Stockholder or Stockholders given within 30 days after the Company
provides such notice (which request shall state the number of Registrable Shares
to be registered and the intended method of distribution of such Registrable
Shares), the Company shall, subject to Section 2.1.2 and 2.1.3 below, cause all
Registrable Shares which the Company has been requested by such Stockholder or
Stockholders to be included in the Registration; provided that each Stockholder
shall be required to register not less than 10,000 shares in any such
Registration Statement, and provided, further, that the Company shall have the
right to postpone or withdraw any registration effected pursuant to this Section
2.1 without obligation or liability to any Stockholder (it being understood that
any such postponement or withdrawal shall not adversely affect the number of the
Stockholders registration rights under Section 2.1.3).

         2.1.2. In connection with any Registration under this Section 2.1
involving an underwritten offering, the Company shall not be required to include
any Registrable Shares in such Registration unless the holders thereof accept
the terms of the underwriting as agreed upon between the Company and the
underwriters selected by it. If in the opinion of the managing underwriter
employed by the Company for

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the distribution of equity securities it shall determine, in its sole
discretion, that the registration of all, or part of, the Registrable Shares
which the holders have requested to be included would interfere with the
successful marketing of the proposed public offering, then the Company shall be
required to include in the Registration only that number of Registrable Shares,
if any, which the managing underwriter believes may be sold without interfering
with the successful marketing of the proposed public offering. If the number of
Registrable Shares to be included in Registration in accordance with the
foregoing is less than the total number of shares which the holders of
Registrable Shares have requested to be included, then the holders of
Registrable Shares who have requested registration and other holders of
securities entitled to include them in such Registration shall participate in
the underwritten offering pro rata based upon their total ownership of shares of
Common Stock of the Company. If any holder would thus be entitled to include
more shares than such holder requested to be registered, the excess shall be
allocated among other requesting holders pro rata based upon their total
ownership of shares of Common Stock of the Company.

         2.1.3. The Company shall not be required to effect more than two (2)
registrations pursuant to paragraph 2.1.1 above.

2.2.     Registration Procedures.

         2.2.1. If and whenever the Company is required by the provisions of
this Agreement to effect the registration of any of the Registrable Shares under
the Act, the Company shall:

                  2.2.1.1. file with the Commission a Registration Statement
         with respect to such Registrable Shares and use its best efforts to
         cause that Registration Statement to become and remain effective for
         such period of time (not exceeding six months) as may be necessary to
         effect the sale or other disposition of all Registrable Shares covered
         by such Registration Statement or until the Registrable Shares covered
         thereby cease to be Registrable Shares, whichever is sooner;

                  2.2.1.2. as expeditiously as possible prepare and file with
         the Commission any amendments and supplements to the Registration
         Statement and the prospectus included in the Registration Statement as
         may be necessary to keep the Registration Statement effective for the
         period described in Section 2.2.1.1 above;

                  2.2.1.3. as expeditiously as possible furnish to each selling
         Stockholder such reasonable numbers of copies of the prospectus,
         including a preliminary prospectus, and such other documents as each
         selling Stockholder may reasonably request in order to facilitate the
         public sale or other disposition of the Registrable Shares owned by
         such selling Stockholder;

                  2.2.1.4. as expeditiously as possible register or qualify the
         Registrable Shares covered by the Registration Statement under the
         securities or Blue Sky laws of such states as the selling Stockholder
         shall reasonably request; provided, however, that (x) the Company shall
         not for any purpose be required to qualify to do business as a foreign
         corporation in any jurisdiction wherein it is not so qualified or
         execute a general consent to service of process in any jurisdiction and
         (y) if the Company is offering securities for its own account, it need
         not register or qualify under the securities or Blue Sky laws of any
         jurisdiction in which the managing underwriter has no intention of
         offering or selling securities for the account of the Company (except
         that the Company will use its best efforts to register or qualify
         Registrable Securities in such additional jurisdiction as any
         Stockholder may request subject to the limitation of clause (x) and at
         such Stockholder's expense);

                  2.2.1.5. if the distribution is to be made by means of an
         underwritten public offering and subject to receiving reasonable
         assurances of confidentiality, make available for inspection by the
         underwriters and its counsel or other advisors, such financial and
         other information and books and records of the Company, and cause the
         officers, directors, employees, counsel and independent certified
         public accountants of the Company to respond to such inquiries as shall
         be reasonably necessary, in the judgment of such underwriters' counsel,
         to conduct a reasonable investigation within the meaning of Section 11
         of the Act; and

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                  2.2.1.6. use best efforts to make available to its security
         holders, as soon as reasonably practicable, an earnings statement
         covering a period of at least twelve months which shall satisfy the
         provisions of Section 11(a) of the Act and Rule 158 thereunder.

         2.2.2. Each selling Stockholder of Registrable Shares agrees that, upon
receipt of any notice from the Company of (i) any request by the Commission for
amendments or supplements to a Registration Statement or related prospectus
covering any of such selling Stockholder's Registrable Shares, (ii) the issuance
by the Commission of any stop order suspending the effectiveness of a
Registration Statement covering any of such selling Stockholder's Registrable
Shares or the initiation of any proceedings for that purpose, (iii) the receipt
by the Company of any notification with respect to the suspension of the
qualification of any Registrable Shares for sale in any jurisdiction or the
initiation or threatening of any proceeding for such purpose, (iv) the happening
of any event that requires the making of any changes in the Registration
Statement covering any of such selling Stockholder's Registrable Shares so that
it will not contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary to make the statements
therein not misleading or that any related prospectus will not contain any
untrue statement of a material fact or omit to state any material fact necessary
in order to make the statements therein, in light of the circumstances under
which they are made, not misleading, and (v) the Company's reasonable
determination that a post-effective amendment to a Registration Statement
covering any of such selling Stockholder's Registrable Shares or a supplement to
any related prospectus is required under the Act; such selling Stockholder will
forthwith discontinue disposition of such Registrable Shares until it is advised
in writing by the Company that the use of the applicable prospectus (as amended
or supplemented, as the case may be) and disposition of the Registrable Shares
covered thereby pursuant thereto may be resumed; provided, however, (x) that
such selling Stockholder shall not resume its disposition of Registrable Shares
pursuant to such Registration Statement or related prospectus unless it has
received notice from the Company that such Registration Statement or amendment
has become effective under the Act and has received a copy or copies of the
related prospectus (as then amended or supplemented, as the case may be) unless
the Registrable Shares are then listed on a national securities exchange and the
Company has advised such selling Stockholder that the Company has delivered
copies of the related prospectus, as then amended or supplemented, in
transactions effected upon such exchange, subject to any subsequent receipt by
such selling Stockholder from the Company of notice of any of the events
contemplated by Stock clauses (i) through (iv) of this paragraph, and, (y) if so
directed by the Company, such holder will deliver to the Company (at the
Company's expense) all copies, other than permanent file copies then in such
Stockholder's possession, of the prospectus covering such Registrable Shares
current at the time of receipt of such notice.

2.3.     Allocation of Expenses. The Company will pay all Registration Expenses
of all Registrations under this Agreement.

2.4.     Indemnification.

         2.4.1. Indemnification of Holder. In the event that the Company
registers any of the Registrable Shares under the Act, the Company will
indemnify and hold harmless the Holder, its officers, directors, managers,
employees, members, shareholders, agents, controlling persons and underwriters,
from and against any and all losses, claims, damages, expenses or liabilities,
to which it becomes subject under the Act or under any other statute or at
common law or otherwise, and, except as hereinafter provided, will reimburse the
Holder for any legal or other expenses reasonably incurred by it in connection
with investigating or defending any actions whether or not resulting in any
liability, insofar as such losses, claims, damages, expenses, liabilities or
actions arise out of or are based upon any untrue statement or alleged untrue
statement of a material fact contained in the Registration Statement, in any
preliminary or amended preliminary prospectus or in the prospectus (or the
Registration Statement or prospectus as from time to time amended or
supplemented by the Company) or arise out of or are based upon the omission or
alleged omission to state therein a material fact required to be stated therein
or necessary in order to make the statements therein not misleading or any
violation by the Company of any rule or regulation promulgated under the Act
applicable to the Company and relating to action or inaction required of the
Company in connection with such registration, unless such untrue statement or
omission was made in such registration statement, preliminary or amended,
preliminary prospectus or prospectus in reliance upon and

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in conformity with information furnished in writing to the Company in connection
therewith by the Holder expressly for use therein (each, a "Holder Disclosure
Responsibility" and, collectively, the "Holder Disclosure Matters"); provided,
however, that Holder will indemnify and hold harmless the Company, its officers,
directors, employees, shareholders, agents, controlling persons and
underwriters, from and against any and all losses, claims, damages, expenses or
liabilities, to which it becomes subject under the Act or under any other
statute or at common law or otherwise and, except as hereinafter provided, will
reimburse the Company for any legal or other expenses reasonably incurred by it
in connection with investigating or defending any actions, whether or not
resulting in any liability, insofar as such losses, claims, damages, expenses
liabilities or actions arise out of or are based upon one or more Holder
Disclosure Matters and any untrue statement or alleged untrue statement of
material fact contained in such Registration Statement or the omission or
alleged omission to state a material fact required to be stated therein.

         2.4.2. Promptly after receipt by the party to be indemnified under this
Agreement (the "Indemnified Party") of notice of the commencement of any action
in respect of which indemnity may be sought against the indemnifying party (the
"Indemnifying Party"), the Indemnified Party will notify the Indemnifying Party
in writing of the commencement thereof, and, subject to the provisions
hereinafter stated, the Indemnifying Party shall assume the defense of such
action (including the employment of counsel, who shall be counsel reasonably
satisfactory to the Indemnified Party), and the payment of expenses insofar as
such action shall relate to any alleged liability in respect of which indemnity
may be sought against the Indemnifying Party. The Indemnified Party shall have
the right to employ separate counsel in any such action and to participate in
the defense thereof but the fees and expenses of such counsel shall not be at
the expense of the Indemnifying Party unless the Indemnifying Party has
specifically authorized the employment of such counsel. The Indemnifying Party
shall not be liable to indemnify any person for any settlement of any such
action effected without the Indemnifying Party's consent.

2.5.     Information by Holder. Each holder of Registrable Shares included in
any Registration shall furnish to the Company such information regarding such
holder and the distribution proposed by such holder as the Company may request
in writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Article 2.

2.6.     "Stand-Off" Agreement. Each Stockholder, if requested by the Company
and an underwriter of Common Stock or other securities of the Company, shall
agree not to sell or otherwise transfer or dispose of any Registrable Shares or
other securities of the Company held by such Stockholder for a specified period
of time (not to exceed 180 days) following the effective date of a Registration
Statement; provided, that all officers and directors of the Company enter into
similar agreements. Such agreement shall be in writing in a form satisfactory to
the Company and such underwriter. The Company may impose stop-transfer
instructions with respect to the Registrable Shares or other securities subject
to the foregoing restriction until the end of the stand-off period.

2.7.     Transfer of Rights.

         2.7.1. The rights and obligations of RRD under this Agreement may be
transferred by RRD to another person or entity that is then a stockholder of the
Company, to any affiliate of the Company, to an affiliate of RRD or a successor
in interest in a transaction exempt from registration under the Act; provided
that, in each case, at least 10,000 Registrable Shares (as adjusted for stock
splits, stock dividends, recapitalization or similar events) are transferred.

         2.7.2. Any transferee (other than a stockholder who is already a party
to an agreement in form and substance the same or substantially similar to this
Agreement) to whom rights under this Agreement are transferred shall, as a
condition to such transfer, deliver to the Company a written instrument by which
such transferee identifies itself, gives the Company notice of the transfer of
such rights, indicates the Registrable Shares owned by it and agrees to be bound
by the obligations imposed upon RRD under this Agreement.

         2.7.3. A transferee to whom rights are transferred pursuant to this
Section 2.7 may not again transfer such rights to any other person or entity,
other than as provided in this Section 2.7.

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2.8.     Exchange Act Registration; Rule 144 Reporting. The Company covenants
and agrees that until such time as RRD no longer holds any Registrable Shares
(or such Registrable Shares otherwise cease to be Registrable Shares) it will
use its best efforts to:

         2.8.1. make and keep public information available, as those terms are
understood and defined in Rule 144 under the Act, even if the Company
subsequently ceases to be subject to such reporting requirements;

         2.8.2. file with the Commission in a timely manner all reports and
documents required of the Company under the Act and the Exchange Act; and

         2.8.3. furnish to RRD promptly upon request (i) a written statement by
the Company as to its compliance with the reporting requirements of Rule 144 and
of the Exchange Act, (ii) a copy of the most recent annual or quarterly report
of the Company, and (iii) such other reports and documents of the Company and
other information in the possession of the Company as RRD may reasonably request
in availing itself of any rule or regulation of the Commission allowing RRD to
sell any such Registrable Shares without registration.

                                   3. ARTICLE

                                  MISCELLANEOUS

3.1.     Notices. All notices, demands, instructions and other communications
required or permitted to be given to or made upon any party hereto shall be in
writing delivered to the parties at the addresses set forth below (or such other
address as may be provided by one party in a notice to the other):

         If to RRD:

                  RRD International, LLC
                  11 North Washington Street
                  Suite 310
                  Rockville, Maryland 20850
                  Facsimile: (301) 762-6154
                  Attention:  Joseph P. Clancy, Esq., Manager, President and CEO

         with a copy to:

                  Wayne M. Zell, Esq.
                  Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  12010 Sunset Hills Road, Suite 900
                  Reston, Virginia 20190
                  Facsimile: 703-464-4895

         If to the Company:

                  Bioenvision, Inc.
                  509 Madison Avenue, Suite 404
                  New York, New York 10022
                  Facsimile: (212) 750-6777
                  Attention:  David P. Luci, Esq.

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         with a copy to:

                  Paul, Hastings, Janofsky & Walker LLP
                  Park Avenue Tower
                  75 East 55th Street
                  New York, New York 10022
                  Facsimile: (212) 319-4090
                  Attention:  Luke P. Iovine, III, Esq.

Notice delivered in accordance with the foregoing shall be effective (i) when
delivered, if delivered personally or by facsimile transmission, (ii) two days
after being delivered in the United States (properly addressed and all fees
paid) for overnight delivery service to a courier (such as Federal Express)
which regularly provides such service and regularly obtains executed receipts
evidencing delivery or (iii) five days after being deposited (properly addressed
and stamped for first-class delivery) in a daily serviced United States mail
box.

3.2.     Binding Effect. This Agreement shall be binding upon and inure to the
benefit of and be enforceable by the respective successors and permitted assigns
of the parties hereto.

3.3.     Headings. Article and Section headings used in this Agreement are for
convenience of reference only and shall not constitute a part of this Agreement
for any purpose or affect the construction of this Agreement.

3.4.     Execution in Counterparts. This Agreement may be executed in any number
of counterparts and by different parties on separate counterparts, each of which
counterparts, when so executed and delivered, shall be deemed to be an original
and all of which counterparts, taken together, shall constitute one and the same
Agreement. This Agreement shall become effective upon the execution of a
counterpart hereof by each of the parties hereto.

3.5.     Governing Law. This Agreement shall be deemed to have been made in the
State of New York and the validity of this Agreement, the construction,
interpretation and enforcement thereof, and the rights of the parties thereto
shall be determined under, governed by, and construed in accordance with the
internal laws of the State of New York, without regard to principles of
conflicts of law.

3.6.     Survival of Agreements, Representations and Warranties. All agreements,
representations and warranties made herein shall survive the execution and
delivery of this Agreement.

3.7.     Arbitration . Any dispute or controversy arising under, out of, in
connection with, or in relation to this Agreement shall be determined and
settled by arbitration in New York by a panel of three members in accordance
with the commercial rules of the American Arbitration Association. Any award
rendered therein shall be final and binding upon the parties and their legal
representatives and judgment may be entered in any court having jurisdiction
thereof.

3.8.     Amendments and Waivers. Any term of this Agreement may be amended and
the observance of any term of this Agreement may be waived (either generally or
in a particular instance and either retroactively or prospectively), with the
written consent of the Company and the holders of at least 51% of the
Registrable Shares; provided, that this Agreement may be amended with the
consent of the holders of less than all Registrable Shares (but not less than
51% of such shares) only in a manner which affects all Registrable Shares in the
same fashion. No waivers of or exceptions to any term, condition or provision of
this Agreement, in any one or more instances, shall be deemed to be, or
construed as, a further or continuing waiver of any such term, condition or
provision.

                            [Signature page follows]

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                  IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be executed as of the date first-above written.

                             RRD INTERNATIONAL, LLC

                             By:  /s/ Joseph P. Clancy
                                  ----------------------------------
                                  Name:  Joseph P. Clancy
                                  Title:  Manager, President and CEO

                             BIOENVISION, INC.

                             By:  /s/ David P. Luci
                                  ---------------------------------------------
                                  Name:    David P. Luci
                                  Title:   Director of Finance, General Counsel

                                       8<PAGE>

                                                                     Exhibit 4.2

THE SECURITIES EVIDENCED HEREBY AND THE SECURITIES ISSUABLE UPON EXERCISE HEREOF
HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED ("ACT"),
OR UNDER THE SECURITIES LAWS OF ANY STATE, AND MAY NOT BE OFFERED, SOLD,
TRANSFERRED OR ASSIGNED EXCEPT PURSUANT TO (I) AN EFFECTIVE REGISTRATION
STATEMENT UNDER THE ACT, (II) TO THE EXTENT APPLICABLE, RULE 144 UNDER THE ACT
(OR ANY SIMILAR RULE UNDER SUCH ACT RELATING TO THE DISPOSITION OF SECURITIES),
OR (III) AN OPINION OF COUNSEL, IF SUCH OPINION SHALL BE REASONABLY SATISFACTORY
TO COUNSEL TO THE ISSUER, THAT AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT IS
AVAILABLE. THIS LEGEND SHALL BE ENDORSED UPON ANY WARRANT ISSUED IN EXCHANGE FOR
THIS WARRANT.

                                WARRANT AGREEMENT
                               FOR COMMON STOCK OF
                                BIOENVISION, INC.

Warrant No. 00-_______

                                                                175,000 WARRANTS

         THIS WARRANT CERTIFIES that, for value received, RRD INTERNATIONAL,
LLC, a Delaware limited liability company, or its permitted assigns
(collectively, the "Holder"), is entitled to purchase from Bioenvision, Inc., a
Delaware corporation (the "Company"), at any time and from time to time, during
the exercise period referred to in Section 1 hereof, One Hundred Seventy-Five
Thousand (175,000) fully paid, validly issued and nonassessable shares (the
"Warrant Shares") of common stock of the Company, par value $.001 per share (the
"Common Stock") at the exercise price of $2.00 per share (the "Warrant Share
Price"). Securities issued upon exercise of this Warrant and the exercise price
payable therefor are subject to adjustment from time to time as hereinafter set
forth. As used herein, the term "Warrant" shall include any warrant or warrants
hereafter issued in consequence of the exercise of this Warrant in part or
transfer of this Warrant in whole or in part.

         The Company shall register this Warrant upon records to be maintained
by the Company for that purpose (the "Warrant Register"), in the name of the
record Holder hereof from time to time. The Company may deem and treat the
registered Holder of this Warrant as the absolute owner hereof for the purpose
of any exercise hereof or any distribution to the Holder, and for all other
purposes, and the Company shall not be affected by notice to the contrary.

1.       Exercise; Payment for Ownership Interest.

         (a) Upon the terms and subject to the conditions set forth herein, this
Warrant shall vest and Warrants shall be exercisable in five equal installments
upon the execution of this Agreement and the achievement of certain milestones
set forth below in accordance with the following vesting schedule:

(i)      20% of this Warrant (representing 35,000 Warrant Shares) shall vest
         upon execution of this Agreement by both parties hereto.
(ii)     20% of this Warrant (representing 35,000 Warrant Shares) shall vest
         immediately upon completion of the pre-IND meeting for the Company's
         Modrenal product.
(iii)    20% of this Warrant (representing 35,000 Warrant shares) shall vest
         immediately upon filing of the IND for Modrenal.
(iv)     20% of this Warrant (representing 35,000 Warrant Shares) shall vest
         immediately upon completion of the following three activities in
         connection with the Phase II prostate cancer study for Modrenal:

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         (a) preparation by Holder of protocol; and (b) preparation by Holder of
         case report forms; and (c) completion of site qualification and
         initiation visits by Holder.
(v)      20% of this Warrant (representing 35,000 Warrant Shares) shall vest
         immediately upon completion of the following two activities: (a)
         preparation of the initial strategic and operational plan ("the Plan")
         by Holder for development of the Company's Clofarabine product; and (b)
         as soon as the Holder commences its work with respect to the Plan.

Upon the achievement of each such milestone, this Warrant may be exercised for
the Warrants vested with respect to such milestone by the Holder hereof at any
time, or from time to time, on or after the date such milestone is achieved and
prior to 5 p.m. New York time on the five-year anniversary of the achievement of
the first milestone set forth in 1.A. above (the "Exercise Period"). Upon such
exercise, Holder shall present and surrender this Warrant to the principal
offices of the Company, or at the office of its Transfer Agent (as hereinafter
defined), if any, together with the Purchase Form annexed hereto, duly executed,
and accompanied by payment to the Company of an amount equal to the Warrant
Share Price multiplied by the number of Warrant Shares as to which this Warrant
is then being exercised; provided, however, that in each case, the minimum
number of Warrant Shares as to which this Warrant is being executed shall not be
less than 10,000 Warrant Shares; provided; further, that prior to the expiration
of the Exercise Period, in the event of (i) any merger, consolidation or sale of
all or substantially all the assets of the Company resulting in a single
transaction or series of related transactions, (ii) the acquisition by any
person, entity or group within the meaning of Section 13(d)(3) of the Securities
Exchange Act of 1934, as amended, of the Common Stock possessing a majority of
the voting power to elect directors of the Company, or (iii) approval by the
stockholders of the Company of a liquidation or dissolution of the Company, the
Holder shall have the right to exercise this Warrant commencing at such time
through the Exercise Period into the kind and amount of shares of stock and
other securities and property (including cash) receivable by a holder of the
number of shares of Common Stock into which this Warrant might have been
exercisable immediately prior thereto. Any transfer of Warrant Shares obtained
by the Holder in exercise of this Warrant is subject to the requirement that
such securities be registered under the Act, and applicable state securities
laws, or exempt from registration under such laws to the reasonable satisfaction
of the Company and its counsel. Except as provided in Section 1(c) hereof, the
Holder of this Warrant shall be deemed to be a stockholder of the Warrant Shares
as to which this Warrant is exercised in accordance herewith effective
immediately after the close of business on the date on which the Holder shall
have delivered to the Company this Warrant in proper form for exercise and
payment by certified or official bank check or wire transfer of the cash
purchase price for the number of Warrant Shares as to which the exercise is
being made, or by delivery to the Company of securities of the Company having a
value equal to the cash purchase price for such number of Warrant Shares
determined in good faith by the Board of Directors of the Company as of the date
of delivery, notwithstanding that the stock transfer books of the Company shall
be then closed or that certificates representing such Warrant Shares shall not
then be physically delivered to the Holder.

         (b) Subject to Section 3 of this Warrant, the Company shall register
the transfer of any portion of this Warrant in the Warrant Register, upon
surrender of this Warrant with the Form of Assignment attached hereto duly
completed and signed, to the Transfer Agent or to the Company. Upon any such
registration or transfer, a new warrant to purchase Common Stock, in
substantially the form of this Warrant so transferred shall be issued to the
transferee and a new warrant evidencing the remaining portion of this Warrant
not so transferred (the "New Warrant"), if any, shall be issued to the
transferring Holder. The acceptance of the New Warrant by the transferee thereof
shall be deemed the acceptance by such transferee of all of the rights and
obligations of a holder of a Warrant. Any transfer or assignment of this Warrant
and Warrant Shares obtained by the Holder in exercise of this Warrant is subject
to the requirements that such securities be registered under the Act and
applicable state securities laws or exempt from registration under such laws to
the satisfaction of the Company and its counsel.

         (c) Right to Convert Warrant into Common Stock: Net Issuance.

                  (i) Right to Convert. In addition to and without limiting the
                  rights of the Holder under the terms of this Warrant, the
                  Holder shall have the right to convert the vested

                                       2
<PAGE>

                  portion of this Warrant or any portion thereof (the
                  "Conversion Right" into shares of Common Stock as provided in
                  this Section 1(c) at any time or from time to time during the
                  term of this Warrant; provided, however, that in each case the
                  minimum number of Warrant Shares as to which this Warrant is
                  being exercised shall not be less than 10,000 Warrant Shares.
                  Upon exercise of the Conversion Right with respect to a
                  particular number of shares subject to this Warrant (the
                  "Converted Warrant Shares"), the Company shall deliver to the
                  Holder (without payment by the Holder of the Warrant Share
                  Price or any cash or other consideration) that number of
                  shares of fully paid and non-assessable Common Stock equal to
                  the quotient obtained by dividing (X) the value of this
                  Warrant (or the specified portion hereof) on the Conversion
                  Date (as defined in subsection (ii) hereof), which value shall
                  be determined by subtracting (A) the aggregate Warrant Share
                  Price of the Converted Warrant Shares immediately prior to the
                  exercise of the Conversion Right from (B) the aggregate fair
                  market value of the Converted Warrant Shares issuable upon
                  exercise of this Warrant (or the specified portion hereof) on
                  the Conversion Date (as herein defined) by (Y) the fair market
                  value of one share of Common Stock on the Conversion Date (as
                  herein defined).

                  Expressed as a formula, such conversion shall be computed as
follows:

                  X  =  B-A / Y

         where:   X  =  the number of shares of Common Stock that may be issued
                        to holder,

                  Y  =  the fair market value ("FMV") of one share of Common
                        Stock,

                  A  =  the aggregate Warrant Share Price (Converted Warrant
                        Shares x Warrant Share Price), and

                  B  =  the aggregate FMV (ie; FMV x Converted Warrant Shares).

         No fractional shares shall be issuable upon exercise of the Conversion
         Right, and, if the number of shares to be issued determined in
         accordance with the foregoing formula is other than a whole number, the
         Company shall pay to the Holder an amount in cash equal to the fair
         market value of the resulting fractional share as of the Conversion
         Date (as herein defined).

                  (ii) Method of Exercise. The Conversion Right may be exercised
                  by the Holder by the surrender of this Warrant at the
                  principal office of the Company together with the Purchase
                  Form in the form attached hereto duly completed and executed
                  and indicating the number of shares subject to this Warrant
                  which are being surrendered (referred to in Section 1(c)(i)
                  hereof as the Converted Warrant Shares) in exercise of the
                  Conversion Right. Such conversion shall be effective upon
                  receipt by the Company of this Warrant together with the
                  aforesaid written statement, or on such later date as is
                  specified therein (the "Conversion Date"), and, at the
                  election of the Holder hereof, may be made contingent upon the
                  occurrence of any of the events specified in Section 8.
                  Certificates for the shares issuable upon exercise of the
                  Conversion Right and, if applicable, a new Warrant evidencing
                  the balance of the shares remaining subject to this Warrant,
                  shall be issued as of the Conversion Date and shall be
                  delivered to the holder within thirty (30) days following the
                  Conversion Date.

                  (iii) Determination of Fair Market Value. For purposes of this
                  Section 1(c), "fair market value" or "FMV" of a share of
                  Common Stock as of a particular date (the "Determination
                  Date") shall mean:

                           (A) If traded on a securities exchange, the fair
         market value of the Common Stock shall be deemed to be the average of
         the closing prices of the Common Stock on such exchange over the
         five-day period ending one business day prior to the Determination Date
         or, if less, such number of days as the Common Stock has been traded on
         such exchange;

                                       3
<PAGE>

                           (B) If traded over-the-counter, the fair market value
         of the Common Stock shall be deemed to be the average of the closing
         bid prices of the Common Stock over the five-day period ending one
         business day prior to the Determination Date or, if less, such number
         of days as the Common Stock has been traded over-the-counter; and

                           (C) If there is no public market for the Common
         Stock, then fair market value shall be determined in good faith by the
         board of directors of the Company.

2.       Anti-Dilution Provisions. The Warrant Share Price in effect at any time
and the number and kind of securities issuable upon exercise of this Warrant and
the Warrant Share Price shall be subject to adjustment from time to time upon
happening of certain events as follows:

         2.1      Adjustments.  If the Company:

                  (i)      subdivides or reclassifies its outstanding shares of
                           Common Stock into a greater number of shares;

                  (ii)     combines or reclassifies its outstanding shares of
                           Common Stock into a smaller number of shares;

                  (iii)    issues, by reorganization or reclassification of its
                           Common Stock, any shares of its capital stock;

then the number and kind of Warrant Shares purchasable upon exercise of this
Warrant shall be adjusted so that the Holder upon exercise hereof shall be
entitled to receive the kind and number of Warrant Shares or other securities of
the Company that the Holder would have owned or have been entitled to receive
after the happening of any of the events described above had this Warrant been
exercised immediately prior to the happening of such event or any record date
with respect thereto. An adjustment made pursuant to this Section 2.1 shall
become effective immediately after the record date in the case of a dividend or
distribution and shall become effective immediately after the effective date in
the case of a subdivision, combination or issuance. If, as a result of an
adjustment made pursuant to this Section 2.1, the Holder of this Warrant
thereafter surrendered for exercise shall become entitled to receive shares of
two or more classes of capital stock or shares of Common Stock and any other
class of capital stock of the Company, the Board of Directors (whose
determination shall be conclusive and shall be described in a written notice to
all holders of Warrants promptly after such adjustment) shall determine the
allocation of the adjusted Warrant Share Price between or among shares of such
classes of capital stock or shares of Common Stock and such other class of
capital stock.

The adjustment to the number of Warrant Shares purchasable upon the exercise of
this Warrant described in this Section 2.1 shall be made each time any event
listed in paragraphs (i) through (iii) of this Section 2.1 occurs.

         2.2 In the event that at any time, as a result of an adjustment made
pursuant to this Section 2.1, the Holder of this 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 this
Warrant shall be subject to adjustment from time to time in a manner and on
terms as nearly equivalent as practicable to the provisions with respect to the
Common Stock contained herein.

         2.3 Other Action Affecting Warrant Shares. If the Company takes any
action affecting its shares of Common Stock after the date hereof, that would be
covered by Section 2.1 but for the manner in which such action is taken or
structured, which would in any way diminish the value of this Warrant, then the
Warrant Share Price shall be adjusted in such manner as the Board of Directors
of the Company shall in good faith determine to be equitable under the
circumstances.

         2.4 Notice of Adjustments. Upon the occurrence of each adjustment or
readjustment of the

                                       4
<PAGE>

Warrant Share Price pursuant to this Section 2, the Company at its expense will
promptly compute such adjustment or readjustment in accordance with the terms of
this Warrant and prepare a certificate setting forth such adjustment or
readjustment, including a statement of the adjusted Warrant Share Price or
adjusted number of shares of Common Stock, if any, issuable upon exercise of
each Warrant, describing the transaction giving rise to such adjustments and
showing in detail the facts upon which such adjustment or readjustment is based.
The Company will forthwith mail, by first class mail, postage prepaid, a copy of
each such certificate to the Holder of this Warrant at the address of such
Holder as shown on the books of the Company, and to its Transfer Agent.

         2.5 Adjustment Calculations. No adjustment in the Warrant Share Price
shall be required unless such adjustment would require an increase or decrease
of at least one cent ($0.01) in such price; provided, however, that any
adjustments which by reason of this Section 2.5 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 2 shall be
made to the nearest cent or to the nearest one-hundredth of a share, as the case
may be.

3.       No Voting Rights. Except as otherwise provided herein, this Warrant
shall not be deemed to confer upon the Holder any right to vote or to consent to
or receive notice as a stockholder of the Company, as such, in respect of any
matters whatsoever, or any other rights or liabilities as a stockholder, prior
to the exercise hereof.

4.       Warrants Transferable. This Warrant and all rights hereunder are
transferable, in whole or in part, at the principal offices of the Company by
the Holder hereof, upon surrender of this Warrant properly endorsed; provided,
however, that in each case the minimum number of Warrant Shares being
transferred by the Holder shall not be less than 10,000 Warrant Shares;
provided, further, however, that without the prior written consent of the
Company, this Warrant and all rights hereunder may be transferred only (i) to an
affiliate of the initial Holder hereof or successor in interest to any such
person in a transaction exempt from registration under the Act; or (ii) pursuant
to the registration of this Warrant or the Warrant Shares under the Act or
subsequent to one year from the date hereof pursuant to an available exemption
from such registration.

5.       Warrants Exchangeable; Assignment; Loss, Theft, Destruction, Etc. This
Warrant is exchangeable, without expense, upon surrender hereof by the Holder
hereof at the principal offices of the Company, or at the office of its Transfer
Agent, if any, for new Warrants of like tenor representing in the aggregate the
right to subscribe for and purchase the Warrant Shares which may be subscribed
for and purchased hereunder, each such new Warrant to represent the right to
subscribe for and purchase such Warrant Shares as shall be designated by such
Holder hereof at the time of such surrender. Upon surrender of this Warrant to
the Company at its principal office, or at the office of its Transfer Agent, if
any, with an instrument of assignment duly executed and funds sufficient to pay
any transfer tax, the Company shall, without charge, execute and deliver a new
Warrant in the name of the assignee named in such instrument of assignment and
this Warrant shall promptly be cancelled. This Warrant may be divided or
combined with other warrants which carry the same rights upon presentation
hereof at the principal office of the Company, or at the office of its Transfer
Agent, if any, together with a written notice specifying the names and
denominations in which new Warrants are to be issued and signed by the Holder
hereof. The term "Warrant" as used herein includes any Warrants into which this
Warrant may be divided or exchanged. Upon receipt of evidence satisfactory to
the Company of the loss, theft, destruction or mutilation of this Warrant and,
in the case of any such loss, theft or destruction, upon delivery of indemnity
satisfactory to the Company, or, in the case of any such mutilation, upon
surrender or cancellation of this Warrant, the Company will issue to the Holder
hereof a new Warrant of like tenor, in lieu of this Warrant, representing the
right to subscribe for and purchase the Warrant Shares which may be subscribed
for and purchased hereunder. Any such new Warrant executed and delivered shall
constitute an additional contractual obligation of the Company, whether or not
this Warrant so lost, stolen, destroyed, or mutilated shall be at any time
enforceable by anyone.

6.       Legends; Investment Representations. Any certificate evidencing the
securities issued upon exercise of this Warrant shall bear a legend in
substantially the following form:

                                       5
<PAGE>

        THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
        REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
        "ACT") OR ANY OTHER SECURITIES LAWS, AND SUCH SECURITIES MAY
        NOT BE SOLD, TRANSFERRED OR ASSIGNED UNLESS SO REGISTERED OR
        AN EXEMPTION FROM REGISTRATION UNDER SAID ACT AND ANY OTHER
        APPLICABLE SECURITIES LAWS IS AVAILABLE.

Upon the registration, under the Act, of the securities issued upon exercise of
the Warrant such legend shall be removed from the certificate evidencing such
securities.

7.       Modifications and Waivers. The Holder of this Warrant acknowledges and
agrees that the terms of this Warrant may be amended, modified or waived only by
the written agreement between the Holder and the Company.

8.       Miscellaneous. The Company shall pay all expenses and other charges
payable in connection with the preparation, issuance and delivery of this
Warrant and all substitute Warrants, including, without limitation, the
reasonable fees and expenses of one counsel to the Holder provided that such
reasonable fees and expenses which arise in connection with the negotiation,
execution and delivery of this Warrant, the Master Services Agreement and
related transaction documents shall not exceed $5,0000 in the aggregate. The
Holder shall pay all taxes (other than any issuance taxes, including, without
limitation, documentary stamp taxes, transfer taxes and other governmental
charges, which shall be paid by the Company) in connection with such issuance
and delivery of this Warrant and the Warrant Shares. In addition, the Holder
shall pay all taxes in connection with any sale, assignment or other transfer of
this Warrant.

The Company shall maintain, at the office or agency of the Company maintained by
the Company, books for the registration and transfer of the Warrant.

9.       Reservation of Warrant Shares. The Company will at all times reserve
and keep available, free from preemptive rights, out of the aggregate of its
authorized but unissued Common Stock or its authorized and issued Common Stock
held in its treasury, solely for the purpose of enabling it to satisfy any
obligation to issue Warrant Shares upon exercise of this Warrant, the maximum
number of shares of Common Stock that may then be deliverable upon the exercise
of this Warrant. This Warrant is a valid and binding obligation of the Company,
enforceable in accordance with its terms except (i) as limited by applicable
bankruptcy, insolvency, reorganization, moratorium and other laws of general
application affecting enforcement of creditor's rights generally and (ii) as
limited by laws relating to the availability of specific performance, injunctive
relief and equitable remedies. The execution, delivery and performance of this
Warrant have been or, on or before March 10, 2003 will be, duly authorized by
all necessary corporate or other action of the Company.

The Company or, if appointed, the Transfer Agent for the Common Stock (the
"Transfer Agent") and every subsequent transfer agent for any shares of the
Company's capital stock issuable upon the exercise of any of the rights of
purchase aforesaid will be irrevocably authorized and directed at all times to
reserve such number of authorized shares as shall be required for such purpose.
The Company will keep a copy of this Warrant on file with the Transfer Agent and
with every subsequent transfer agent for any shares of the Company's capital
stock issuable upon the exercise of the rights of purchase represented by this
Warrant. The Company covenants that all Warrant Shares that may be issued upon
exercise of this Warrant will, upon issue, be fully paid, nonassessable, free of
preemptive rights and free from all taxes, liens, charges and security interests
with respect to the issue thereof.

10.      Elimination of Fractional Interests. The Company shall not be required
to issue certificates representing fractions of shares of Common Stock upon the
exercise of the Warrants nor shall it be required to issue scrip or pay cash in
lieu of fractional interests, it being the intent of the parties that all
fractional

                                       6
<PAGE>

interests shall be eliminated by rounding any fraction up to the nearest whole
number of shares of Common Stock or other securities, properties or rights.

11.      Registration. The Warrant Shares shall be registered under the
Securities Act, to the extent provided in that certain Registration Rights
Agreement of even date herewith, by and between the Company and the Holder of
this Warrant.

12.      Descriptive Headings and Governing Law. The descriptive headings of the
several paragraphs of this Warrant are inserted for convenience only and do not
constitute a part of this Warrant. This Warrant shall be construed and enforced
in accordance with the laws of the State of New York, and the law of such State
shall govern the rights of the parties.

13.      Notices. All notices, requests and other communications hereunder shall
be in writing, shall be either (i) delivered by hand, (ii) made by telex,
telecopy or facsimile transmission, (iii) sent by overnight courier, or (iv)
sent by registered mail, postage prepaid, return receipt requested. In the case
of notices from the Company to the Holder, they shall be sent to the address
furnished to the Company in writing by the last Holder who shall have furnished
an address to the Company in writing. All notices from the Holder to the Company
shall be delivered to the Company at its offices at 509 Madison Avenue, Suite
404, New York, New York 10022, Attention: General Counsel or such other address
as the Company shall notify the Holder. All notices, requests and other
communications hereunder shall be deemed to have been given (i) by hand, at the
time of the delivery thereof to the receiving party at the address of such party
described above, (ii) if made by telex, telecopy or facsimile transmission, at
the time that a receipt thereof has been acknowledged by electronic confirmation
or otherwise, (iii) if sent by overnight courier, on the next business day
following the day such notice is delivered to the courier service, or (iv) if
sent by registered mail, on the fifth business day following the day such
mailing is made.

                            [Signature page follows]

                                       7
<PAGE>

IN WITNESS WHEREOF, this Warrant Agreement has been executed as of the 2nd day
of April, 2003.

                             BIOENVISION, INC.

                             By:   /s/ David P. Luci
                                   -------------------------------------------
                                   Name:  David P. Luci
                                   Title: Director of Finance, General Counsel

                                       8
<PAGE>

                                  PURCHASE FORM

                                                          Dated:__________, ____

The undersigned hereby irrevocably elects to exercise the within Warrant to the
extent of purchasing _____ Warrant Shares and hereby makes payment of
$_____________ in payment of the exercise price thereof.

                     ______________________________________
<PAGE>

                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

         FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers
unto _____________________ the right represented by the within Warrant to
purchase ________ shares of Common Stock of _____________ to which the within
Warrant relates and appoints _____________ attorney to transfer said right on
the books of ___________________ with full power of substitution in the
premises.

Dated:  _________ __, 200_

                              --------------------------------------
                              (Signature must conform in all respects to name
                              of holder as specified on the face of the Warrant)

                              Address of Transferee:

                              ------------------------

                              ------------------------

                              ------------------------

In the presence of:

-----------------------

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