Exhibit 10.26


                   AMENDMENT NO. 2 TO THE CO-DEVELOPMENT AGREEMENT


This  Amendment  No. 2 to  Co-Development  Agreement,  is made and  effective on
December 31, 2003 (the "Second Amendment"), by and between Bioenvision,  Inc., a
corporation having its principal  executive office at 509 Madison Avenue,  Suite
404,  New York,  New York  10022  ("Bioenvision")  and ILEX  Products,  Inc.,  a
corporation  having its principal  executive  office at 4545 Horizon Hill Blvd.,
San Antonio, Texas 78229-2263.


                                   WITNESSETH:


         WHEREAS,   Bioenvision  and  ILEX  Oncology,  Inc.  are  parties  to  a
co-development  agreement entered into and effective March 12, 2001 (as amended,
the "Agreement");

         WHEREAS,  subject to Section 23 of the Agreement,  ILEX Oncology,  Inc.
assigned the Agreement and all of its business  assets relating to the Agreement
to ILEX  Products,  Inc.,  a  wholly-owned  subsidiary  of ILEX  Oncology,  Inc.
("ILEX") on March 15, 2002;

         WHEREAS,  on  September  2, 2003,  Bioenvision  and ILEX entered into a
Letter Agreement for Co-Development of an Oral Clofarabine Formulation and First
Amendment to Co-Development Agreement (the "First Amendment");

         WHEREAS, pursuant to Section 25.2 of the Agreement, ILEX is desirous of
further  amending the Agreement to enable ILEX to accelerate the granting of the
exclusive  sub-license by Bioenvision to ILEX for  Clofarabine or any Product in
the USA and Canada as set forth in Article 6.1, in exchange for ILEX agreeing to
accelerate the payments made to  Bioenvision  under Articles 3.4 and 3.6 so that
Bioenvision receives payments on earlier dates than otherwise required under the
Agreement  with a larger  portion of the total amount of the payments being paid
initially; and

         WHEREAS,  Bioenvision is agreeable to the accelerated sub-license grant
and payment  schedule  proposed by ILEX,  subject to the provisions set forth in
the Second Amendment.

         NOW,  THEREFORE,  in  consideration  of the  premises  and  the  mutual
covenants and agreements  herein contained,  ILEX,  Bioenvision and SRI agree as
follows:

         As used  throughout  the  Second  Amendment  unless  otherwise  defined
herein,  the capitalized  terms shall have the meanings  ascribed to them in the
Agreement.


         1. Section 6.1 of the Agreement shall be renamed Section 6.1(a) and
Section 6.1(a) shall be amended by adding the following after the third sentence
thereof:

"Notwithstanding the foregoing sentence, the exclusive sub-license referenced
therein shall earlier become effective, if and only if ILEX makes payment to
Bioenvision of US$3.5 million by irrevocable wire transfer of immediately
available funds on or before the date of this Second Amendment. In the event of
such payment, the decision of Management to transfer manufacturing and marketing
rights for Clofarabine and Products in the USA and Canada under this Section,
via the grant of an exclusive license to ILEX, shall be accelerated to the date
of payment and the conditions for completion of the Co-Development Program set
forth herein, including the milestone events in Section 2.2 hereof shall be
deemed satisfied for purposes of, but only for the purposes of, granting of the
exclusive license to ILEX as set forth in this Section."


<PAGE>


         2. Section 6.1 of the Agreement shall be amended further by adding
Section 6.1(b) immediately following Section 6.1(a) as follows:

"6.1(b) Upon Bioenvision's grant of an exclusive sub-license pursuant to Section
6.1(a) above, the payment obligations of ILEX pursuant to Sections 3.4 and 3.6
of the Agreement shall be replaced by those in Section 6.1(c) below (while all
other financial obligations of ILEX, including, without limitation, ILEX's
obligations to SRI under Section 5.2 hereof, under the Agreement shall remain in
full force and effect) and the provisions of Section 20 of the Agreement shall
remain in full force and effect."

         3. Section 6.1 of the Agreement shall be amended further by adding
Section 6.1(c) immediately following Section 6.1(b) as follows:

"6.1(c) In consideration for the accelerated sub-license grant set forth in
Section 6.1(a) above, ILEX agrees to the following:

       (i)  Within five days following submittal of the first completed NDA
            filing with the FDA, for use of Clofarabine in the Field, ILEX shall
            pay to Bioenvision a sum of US$2 million by irrevocable wire
            transfer of immediately available funds; and

       (ii) Within six (6) months after submittal of the first completed NDA
            filing with the FDA, for use of Clofarabine in the Field, as set
            forth in the preceding sub-section 6.1(c)(i) above, ILEX shall pay
            to Bioenvision a sum of US$2 million by irrevocable wire transfer of
            immediately available funds."

         4. Section 6.1 of the Agreement shall be amended further by adding
Section 6.1(d) immediately following Section 6.1(c) as follows:

"6.1(d) All references in this Agreement to Section 6.1 shall be deemed to
include the provisions of Sections 6.1(a)-(d) and all references to "exclusive
license" in referring to the license grant from Bioenvision to ILEX in this
Agreement shall be amended to read "exclusive sublicense"."

Except as modified herein, the terms and conditions of the Agreement shall
remain in full force and effect.


<PAGE>


         IN WITNESS WHEREOF, the Parties have caused this Amendment to be
executed by their duly authorized representatives.
ILEX Products, Inc.                   Bioenvision, Inc.


By: /s/ Al A. Jecminek                By: /s/ David P. Luci
    ----------------------------          ------------------------------

Typed Name: Al A. Jecminek            Typed Name: David P. Lucik
            --------------------                  ----------------------

Title: Vice President, Licensing      Title: Director of Finance,
       -------------------------             ---------------------------
       and Intellectual Property             General Counsel
Date:  12/30/03                       Date:  12/30/03
       -------------------------             ---------------------------


Also, by signature of its duty authorized representative below, Southern
Research Institute accepts and agrees to all terms and conditions of this Second
Amendment which apply directly or indirectly to Southern Research Institute.

Southern Research Institute

By: /s/ Lucy C. Hicks
   ---------------------------------

Typed Name: Lucy C. Hicks
            ------------------------

Title: Legal Counsel
       -----------------------------

Date:  12/30/2003
       -----------------------------