AMENDMENT NO. 5 TO THE DEVELOPMENT AND MANUFACTURING SERVICES AGREEMENT

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                                                                   Exhibit 10.21

                                 AMENDMENT NO. 5

                                       TO

                        THE DEVELOPMENT AND MANUFACTURING
                                SERVICES AGREEMENT

                              DATED 08 JANUARY 2004

                                     BETWEEN

                               LONZA BIOLOGICS ***

                                       AND

                           TRUBION PHARMACEUTICALS, INC.

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THIS AMENDMENT No. 5 ("Fifth Amendment") is made the 18th day of February, 2005

BETWEEN

LONZA BIOLOGICS *** of *** (hereinafter referred to as "LB"), and

TRUBION PHARMACEUTICALS, INC., of 2401 4th Avenue, Suite 1050, Seattle, WA
98121, USA (hereinafter referred to as the "Customer")

WHEREAS

A.    LB and the Customer entered into a development and manufacturing services
     agreement ("the Agreement") dated 08 January 2004, pursuant to which LB
     agreed to provide Services to the Customer, and,

B.    The Customer now wishes LB to perform additional services under the
     Agreement, and,

C.    LB is willing to perform such additional services on the terms set out in
     the Agreement, and

D.    The parties wish to amend the Agreement in accordance with Clause 13.5
     thereto.

NOW THEREFORE IT IS HEREBY AGREED as follows:

1.    Two new stages, Stages 23 and 24, shall be added to Schedule 2 of the
     Agreement to read as follows:

STAGE 23 ***

     23.1 OBJECTIVES

          ***

     23.2 ACTIVITIES

          ***

     23.3 DELIVERABLES

          23.3.1 Copies of all Process specific documentation prepared in
activity 23.2.1 which has not already been supplied to the Customer

     23.4 TIMESCALE

     Stage 23 will be scheduled in to the Services in such a way that it is not
rate limiting and shall be complete when LB and the Customer have approved the
documentation and when a copy of the approved final bulk Product specification
has been sent to the Customer.

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     It is estimated that Stage 23 will be complete approximately *** from the
commencement of Stage 23.

STAGE 24 ***

     24.1 OBJECTIVES

     ***

     24.2 ACTIVITIES

     ***

     24.3 DELIVERABLES

          24.3.1 A Certificate of Analysis for the Batch of bulk Product
manufactured.

          24.3.2 If requested by Customer, a copy of the completed manufacturing
batch record.

          24.3.3 The manufactured Product, including samples and in-Process
samples to be supplied to Customer as agreed by the parties.

     NOTE: ***.

     24.4 TIMESCALE

          Stage 24 shall be complete upon issue to the Customer of the
Certificate of Analysis for the Batch of Product manufactured.

          It is estimated that the Certificate of Analysis will be issued
approximately *** from commencement of this Stage (estimated out of freeze ***).
If the Customer requests in writing, the Product ca