**Agreement**





This **Agreement** effective as of the 9 th day of
March 2005 (the “Effective Date”) is entered into by and between **Keryx
Biopharmaceuticals, Inc.** , a
Delaware corporation having an office at 750 Lexington Avenue, 26 th Floor,
New York, NY 10022 (“Keryx”), **Procept,
Inc** ., a
Delaware Corporation having an office at 10 East 53rd Street, 33 rd Floor,
New York, NY 10022 (“Procept”), and **the
United States Public Health Service,** an
agency of the United States Government, having an address at Office of
Technology Transfer, National Institute of Health, 6011 Executive Boulevard,
Suite 325, Rockville, MA 20852-2804 (“PHS”). Each of Keryx, Procept and PHS
shall be referred to as a Party and collectively as the Parties.




**WHEREAS** , Procept
and the Penn State Research Foundation (PSRF) are parties to a license agreement
dated February 6, 1998 as amended (the “License Agreement”) relating to patent
rights associated with 06-Benzylguanine and/or its derivatives (the “Patent
Rights”);




**WHEREAS** , Procept
has sub-licensed to AOI Pharmaceuticals, Inc. (“AOIP”) its rights to the Patent
Rights under the License Agreement pursuant to a Sublicense Agreement executed
on or about October 13, 2000, as amended (the “Sublicense
Agreement”);





**WHEREAS** , as a
result of the acquisition of AOIP by Keryx, AOIP has become a wholly-owned
subsidiary of Keryx;





**WHEREAS** , PSRF
and PHS entered into Interinstitutional Agreements executed January 29, 2002
(the “Interinstitutional Agreements”) pursuant to which PHS has exclusive
licensing rights associated with the Patent Rights;


****


**WHEREAS** , the
University of Chicago and PHS entered into Interinstitutional Agreement
effective February 28, 2002 (the “Interinstitutional Agreements”) pursuant to
which PHS has exclusive licensing rights associated with the Patent
Rights;


****


**WHEREAS,** such
Interinstitutional Agreements superseded and terminated the License Agreement,
but not the Sublicense Agreement; and Procept and PHS have executed a new
exclusive patent license agreement dated February 28, 2002 regarding the Patent
Rights, as amended (the “Revised License Agreement”);







****


**WHEREAS** , Keryx
desires to purchase and assume from Procept and Procept has agreed to sell and
assign to Keryx all of Procept’s rights, interests and obligations under the
Revised License Agreement, which constitutes substantially the entire business
of Procept relating to the operations which concern the Revised License
Agreement; and





**WHEREAS** , in
order to effectuate such Assignment, pursuant to Section 14.07 of the Revised
License Agreement, Procept is obligated to pay PHS the sum of seventeen thousand
five hundred dollars ($17,500).





**NOW
THEREFORE** , in
consideration of the foregoing premises and the mutual covenants herein
contained, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Parties hereby agree as
follows:





1. Procept
hereby assigns to Keryx all of its rights and interests under the Revised
License Agreement, and Keryx hereby assumes all of the obligations of Procept
under the Revised License Agreement (whether such obligations accrued prior to
or after the date of this Agreement); provided, however, such assignment and
assumption shall become effective upon the receipt by Procept of the First
Installment. Procept, PHS and Keryx agree to take all reasonable steps necessary
to effectuate and perfect the actions set forth in this Paragraph.





2.  Procept
represents and warrants to Keryx that (i) the rights and interest conveyed
hereunder are free and clear from any liens or encumbrances of any nature
created by Procept and, to the knowledge of Procept, are free from any
requirement of any past payments, charges, fees or conditions, rights or
restrictions, (ii) Procept is not a party to any pending claim, litigation or
proceeding contesting the rights and interests conveyed hereunder nor, to the
knowledge of Procept, is any such claim threatened against Procept, and (iii)
Procept has not sold, assigned, conveyed, transferred or delivered to any third
party, and, to the knowledge of Procept, no person or entity has any licenses or
other rights under the Revised License Agreement. Keryx represents and warrants
to Procept that AOIP has performed and discharged all of its obligations under
the Sublicense Agreement.










3.  Procept
agrees to indemnify and hold Keryx, its directors, officers, employees and
agents harmless from and against any claims, liabilities, damages and expenses
in connection therewith (including reasonable attorney fees, costs and other
expenses of litigation) resulting from material misrepresentation or material
breach of a warranty by Procept under this **Agreement** . Keryx
agrees to indemnify and hold Procept, its directors, officers, employees and
agents harmless from and against any claims, liabilities, damages and expenses
in connection therewith (including reasonable attorney fees, costs and other
expenses of litigation) resulting from any failure of AOIP to perform and
discharge its obligations under the Sublicense Agreement.





4.  The
Parties hereby agree that for purposes of the Revised License Agreement, AOIP
shall be deemed a third party sublicensee under the Sublicense Agreement and not
an Affiliate of Keryx, with the effect among other things, that all amounts
(including milestones and royalties) owed or to be owed by Procept under the
Revised License Agreement currently applicable to Procept as a result of the
Sublicense Agreement shall remain unchanged by the assignment, except that they
shall become the responsibility of Keryx, irrespective of the affiliated
relationship between Keryx and AOIP. Following this assignment, for all purposes
of the Sublicense Agreement, any reference to Procept shall be deemed a
reference to Keryx. The parties acknowledge and agree that the Sublicense
Agreement shall survive this assignment.




5. As full
consideration for the agreements set forth herein, Keryx agrees to pay Procept a
total consideration of one hundred fifty eight thousand seven hundred and fifty
dollars ($158,750), payable in two installments, a first installment of eighty
three thousand seven hundred fifty dollars ($83,750) (the “First Installment”),
and a second installment of seventy five thousand dollars ($75,000) (the “Second
Installment”). The First Installment shall be payable as provided in Paragraph
6, and the Second Installment shall be evidenced by a promissory note from Keryx
payable to Procept, in the form attached hereto as **Exhibit
A** , which
bears no interest until after the maturity date and shall be due and payable on
December 31, 2005.










6. Within
ten (10) business days following execution of this **Agreement** by all
Parties, Keryx shall make payment of the First Installment as follows: (i) Keryx
shall pay PHS on behalf of Procept the sum of seventeen thousand five hundred
dollars ($17,500) in full satisfaction of the terms and conditions of Section
14.07 of the Revised License Agreement, and (ii) Keryx shall pay Procept an
amount equal to sixty six thousand two hundred and fifty dollars ($66,250),
which represents the First Installment less the amount paid by Keryx to PHS on
behalf of Procept pursuant to this Paragraph 6(i).





7. This **Agreement** embodies
the entire understanding of the parties as to its subject matter hereof.





8. This **Agreement** shall be
construed, governed, interpreted and applied in accordance with the laws of the
State of New York, without regard to its conflict of law rules.





9. This **Agreement** has been
prepared jointly and shall not be strictly construed against any
Party.





**IN
WITNESS WHEREOF** , the
Parties hereto have executed this **Agreement** as of
the Effective Date.




**SIGNATURES
BEGIN ON NEXT PAGE**












**PROCEPT-KERYX
ASSIGNMENT AGREEMENT**





**SIGNATURE
PAGE**





**For
Keryx Biopharmaceuticals, Inc.**








/s/
Michael S.
Weiss


Name:
Michael S. Weiss


Title:
Chairman & CEO


Date:
3/15/05











**For
Procept, Inc.**








By:
/s/ Salvatore A.
Bucci


Name:
Salvatore A. Bucci


Title:
President & CEO


Date:
3/10/05










**ACKNOWLEDGEMENT
AND ACCEPTANCE**





By
PHS:





/s/
Steven M. Ferguson Date:
3/17/05


Steven M.
Ferguson





Director,
Division of Technology Development and Transfer


Office of
Technology Transfer


National
Institutes of Health





Official
and Mailing Address for Notices:





Office of
Technology Transfer


National
Institutes of Health


6011
Executive Boulevard, Suite 325


Rockville,
Maryland 20852-3804 U.S.A.





By
PSRF:





/s/
David E. Branigan   Date:
3/23/05


David E.
Branigan





Treasurer,
The Penn State Research Foundation





Official
and Mailing Address for Notices:





Ronald J.
Huss


The
Pennsylvania State University


Intellectual
Property Office


113
Technology Center


University
Park, PA 16802 U.S.A.








By the
University of Chicago





/s/
Alan E. P. Thomas    Date:
3/25/05


Alan E.
P. Thomas





Director,
Office of Technology & Intellectual Property


University
of Chicago





Official
and Mailing Address for Notices:


University
of Chicago


5555
South Woodlawn Avenue, Suite 300


Chicago,
IL 60637 U.S.A