Exhibit 10.20  November 13, 2008  Mark McCamish [***] [***]  Re: Retention Bonuses  Dear Mark:  We view your
contributions as an officer of Facet Biotech Corporation (Facet) as
important to our long-term success. 
Acknowledging this, we would like to summarize the retention bonuses we
are offering you in connection with our offer of employment to you.  Retention
Bonuses  Subject to
your acceptance of employment with Facet and continued employment in good
standing through the applicable bonus dates (each, a Bonus Date) and
the terms and conditions of this letter agreement (this Letter Agreement),
you will earn, and Facet will pay you, the Retention Bonuses set forth
below:  ·January 31, 2009 - $25,000 ·June 30, 2009 - $69,000 ·December 31, 2009 - $92,000  Subject to the
terms and conditions of this Letter Agreement, each Retention Bonus would be
paid with the next regular paycheck following the applicable Bonus Date.  Notwithstanding the foregoing or anything
else in this Letter Agreement, if prior to a Bonus Date Facet terminates your
employment without Cause (as that term is defined in Facets Retention and
Severance Plan (the RSP)), then on the date of such employment
termination you would, subject to the last sentence in this paragraph, earn a
prorated amount of the portion of any Retention Bonuses that you otherwise
would have earned.  The foregoing
proration would be based on the number of months between December 1, 2008
and such termination date, rounded up to the nearest whole month.  Any portion of your Retention Bonuses that
would be payable pursuant to this paragraph would be earned provided that you
sign, and do not revoke, Facets form of release agreement (Release
Agreement), and we would pay such portion of your Retention Bonus promptly
after the effective date of your Release Agreement and in any event, provided
that your Release Agreement has become effective, within 60 days after your
termination date.


Notwithstanding the terms of the RSP
or the preceding paragraph, should your employment be terminated without Cause
in connection with or following a Change in Control (as that term is defined
in and determined under the RSP) and provided you sign, and do not revoke, the
Release Agreement, we would pay you the full amount of your Retention Bonuses
that you have not yet earned promptly after the effective date of your Release
Agreement and, in any event, provided that your Release Agreement has become
effective, within 60 days of the date of your employment termination.  If Facet
terminates your employment for Cause or you voluntarily terminate your
employment, then you would not receive any portion of your Retention Bonuses
that you have not earned.  You agree that
none of your Retention Bonuses would be grossed up and will be subject to all
applicable payroll withholdings and deductions.  Additional Provisions  Notwithstanding anything contained in this Letter Agreement to the
contrary, no amount payable pursuant to this Letter Agreement on account of
your termination of employment which constitutes a deferral of compensation
within the meaning of the Treasury Regulations issued pursuant to Section 409A
of the Internal Revenue Code (the Section 409A Regulations) will
be paid unless and until you have incurred a separation from service within
the meaning of the Section 409A Regulations.  Furthermore, if you are a specified employee
within the meaning of the Section 409A Regulations as of the date of your
separation from service, no amount that constitutes a deferral of compensation
which is payable on account of your separation from service will paid to you
before the date (the Delayed Payment Date) which is first day of the
seventh month after the date of your separation from service or, if earlier,
the date of your death following such separation from service.  All such amounts that would, but for this
paragraph, become payable prior to the Delayed Payment Date will be accumulated
and paid on the Delayed Payment Date.  Facet intends that income provided to you pursuant to this Letter
Agreement will not be subject to taxation under Section 409A of the
Internal Revenue Code.  The provisions of
this Letter Agreement shall be interpreted and construed in favor of satisfying
any applicable requirements of Section 409A.  However,
Facet does not guarantee any particular tax effect for income provided to you
pursuant to this letter. In
any event, except for Facets responsibility to withhold applicable income and
employment taxes from compensation paid or provided to you, Facet will not be
responsible for the payment of any applicable taxes incurred by you on
compensation paid or provided to you pursuant to this Letter Agreement.  Except as otherwise provided in this Letter
Agreement, all of the other terms and conditions of your employment
relationship with Facet will continue to apply. 
This Letter Agreement is not intended change the at will nature of
your employment with


Facet. 
You would continue to be free to resign at any time, just as Facet would
be free to terminate your employment at any time, with or without cause.  The terms of
this Letter Agreement, when accepted by you, supersede, with the exception of
the RSP, all prior arrangements, whether written or oral, and understandings
regarding the subject matter of this Letter Agreement.  I would like
to thank you for your many contributions to our biotechnology operations and
for your continued support and dedication to Facet.  To indicate your acceptance of the terms of this Letter Agreement,
please sign and date this Letter Agreement in the space provided below and
return it to Gwen Carscadden, Human Resources Department, by December 5,
2008.  Sincerely,  /s/ Faheem HasnainFaheem HasnainPresident and Chief Executive OfficerAGREED AND ACKNOWLEDGED:/s/ Mark McCamishMark McCamishFebruary 13, 2009Date