Exhibit 10.1

NOTE: CERTAIN CONFIDENTIAL INFORMATION HAS BEEN OMITTED FROM THIS DOCUMENT AND
REPLACED BY "[*]". A COMPLETE COPY OF THIS DOCUMENT INCLUDING THE CONFIDENTIAL
INFORMATION HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION.

FOURTH AMENDMENT

TO

DEVELOPMENT AND LICENSE AGREEMENT

          THIS FOURTH AMENDMENT (the “Fourth Amendment”) to the DEVELOPMENT AND
LICENSE AGREEMENT by and between NPS Pharmaceuticals, Inc. (“NPS”) and Amgen
Inc. (“Amgen”) is dated as of August 10, 2011.  NPS and Amgen are referred to in
this Fourth Amendment individually as a “Party” and collectively as the
“Parties”.  Additionally, Royalty Sub (as defined below) hereby acknowledges and
agrees to the provisions contained in this Fourth Amendment.  Certain terms used
herein but not otherwise defined herein shall have the respective meanings set
forth in the Agreement (as defined below).

RECITALS

          WHEREAS, NPS and Amgen have previously entered into a Development and
License Agreement effective as of December 27, 1995, as amended by that certain
First Amendment to Development and License Agreement and that certain Second
Amendment to Development and License Agreement, each effective as of November
19, 2004, and that certain Third Amendment to Development and License Agreement,
effective as of March 4, 2008 (collectively, the “Agreement”);

          WHEREAS, NPS sold, among other things, all of its rights, title, and
interests in, to and under the Agreement to receive payments from Amgen, to
receive statements under Section 7.6(A) of the Agreement from Amgen and to
appoint, and receive reports from, an independent certified public accountant
under Section 7.6(C) of the Agreement, to Cinacalcet Royalty Sub LLC (“Royalty
Sub”);

          WHEREAS, Amgen desires to pay a certain amount as an advance against
future Royalty payments;

          WHEREAS, Royalty Sub, and indirectly NPS, desire to receive such
advance payment against future Royalty payments; and

          WHEREAS, NPS and Amgen now desire to amend certain provisions of the
Agreement as provided for herein, such amendments to take effect subject to, and
upon, the redemption in full of the Class B Notes issued by Royalty Sub under
that certain Indenture dated as December 22, 2004, as amended (the “Indenture”)
and delivery by NPS to Amgen of confirmation thereof from the trustee under the
Indenture (the “Redemption Date”).

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          NOW THEREFORE, in consideration of the mutual covenants contained in
this Fourth Amendment and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the Parties hereby agree as
follows:

ARTICLE I  

AMENDMENT

Section 1.01  Section 7.6(A) of the Agreement is hereby amended by inserting the
following at the end of the last sentence therein:

“Notwithstanding the first sentence of this Section 7.6(A) above, until the
Advance Recovery Date, Amgen shall not be obligated to pay any Royalties to
either NPS or Royalty Sub and instead shall withhold such Royalties and credit
them first (i) against the Discount Amount and then (ii) against the
Unrecaptured Advance.  From and after the Advance Recovery Date, the payment of
Royalties in accordance with Section 7.6 shall resume, including the payment of
any Royalties that are in excess of the amount needed to satisfy clauses (i) and
(ii) above.  Except as expressly set forth in the following sentence, the
Unrecaptured Advance and Discount Amount shall be satisfied solely by the
withholding of Royalties and neither NPS nor Royalty Sub shall have any
obligation to make any payment in respect thereof.  If an Event of Default
occurs, then Amgen shall have the option to have NPS repay all or a portion of
any remaining Unrecaptured Advance (such repayment to be made within [*] days
after Amgen’s delivery of its request for repayment), provided, however, that
[*].”

“The Discount shall accrue on the Unrecaptured Advance from the Advance Date and
shall be computed for each Discount Period on a calendar quarter basis.”   

“For purposes of this Section 7.6(A), the following terms have the meanings set
forth below:

“Advance Date” means the date that the Royalty Advance is paid to Royalty Sub,
via release of such amount from that certain escrow account established by the
Parties concurrently with the execution of the Fourth Amendment to the
Agreement.  The Parties shall provide joint written confirmation to each other
of the occurrence of the Advance Date.

“Advance Recovery Date” means the Payment Date on which an amount equal to the
Unrecaptured Advance plus the then due Discount Amount shall have been withheld
by Amgen from the Royalties.

“Discount” means 9% per annum on the Unrecaptured Advance compounded quarterly
for each Discount Period.

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“Discount Amount” means, on any Payment Date, the amount of accrued and unpaid
Discount.

“Discount Period” means the period beginning on (and including) the Advance Date
and ending on (but excluding) the first Payment Date thereafter and each
successive period beginning on (and including) a Payment Date and ending on (but
excluding) the next succeeding Payment Date.

“Event of Default” means an event whereby Amgen’s and/or its sublicensees’
obligations to pay Royalties to NPS or Royalty Sub under the Agreement cease
with respect to Net Sales in [*] pursuant to Section 14.2(c) (Default by NPS).

“Payment Date” means the date forty-five (45) days after the close of each
calendar quarter during the term of the Agreement.

“Royalty Advance” means the payment by Amgen of $145,000,000 to Royalty Sub as
an advance against future Royalties.

“Unrecaptured Advance” means the amount of the Royalty Advance that has not been
recaptured by Amgen through the withholding of Royalties as of any Payment Date
(it being understood that in no event shall the application of Royalties payable
by Amgen towards the Discount hereunder reduce or otherwise be deemed as a
recapture of the Unrecaptured Advance).”

ARTICLE II  

MISCELLANEOUS

Section 2.01  Ratification of Agreement; Fourth Amendment Part of
Agreement.  Except as expressly amended hereby, the Agreement is in all respects
ratified and confirmed and all the terms, conditions and provisions thereof
shall remain in full force and effect.  This Fourth Amendment shall form a part
of the Agreement for all purposes, and shall be read and construed together with
the Agreement.

Section 2.02  Severability.  In the event that any provision of this Fourth
Amendment or the application thereof to any Party hereto or to any circumstance
or in any jurisdiction governing this Fourth Amendment shall, to any extent, be
invalid or unenforceable under any applicable statute, regulation or rule of
law, then such provision shall be deemed inoperative to the extent that it is
invalid or unenforceable and the remainder of this Fourth Amendment, and the
application of any such invalid or unenforceable provision to the Parties,
jurisdictions or circumstances other than to whom or to which it is held invalid
or unenforceable, shall not be affected thereby nor shall the same affect the
validity or enforceability of this Fourth Amendment.

Section 2.03  Governing Law.  THIS FOURTH AMENDMENT SHALL IN ALL RESPECTS BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
CALIFORNIA, INCLUDING ALL MATTERS OF CONSTRUCTION, VALIDITY AND PERFORMANCE.

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Section 2.04  Counterparts.  This Fourth Amendment may be executed in one or
more counterparts by the Parties hereto, and each such counterpart shall be
considered an original and all such counterparts shall constitute one and the
same instrument.

Section 2.05  Headings, Etc.  The headings of the Articles and Sections of this
Fourth Amendment have been inserted for convenience of reference only, are not
to be considered a part hereof and shall in no way modify or restrict any of the
terms and provisions hereof.

Section 2.06  Amendment.  No amendment, modification or supplement of any
provision of this Fourth Amendment shall be valid or effective unless made in
writing and signed by a duly authorized officer of each Party.

Section 2.07  Authority.   Each Party represents and warrants to the other Party
that it has all rights and authority to enter into this Fourth Amendment, and
that the terms hereof are not inconsistent with other contractual obligations
(express or implied) which it may have.

Section 2.08  Expenses; Survival.  Except as otherwise agreed by the Parties,
each Party will bear its own costs, expenses and fees incurred in connection
with the transactions contemplated by this Fourth Amendment, provided that, NPS
shall indemnify, defend and hold harmless Amgen from any and all losses,
damages, liabilities or expenses (including attorney fees and expenses of
litigation) resulting from any third party claims brought in connection with the
Indenture or that certain Escrow Agreement entered into by the Parties
concurrently herewith, except such claims which arise from Amgen’s willful
misconduct or negligence.  Notwithstanding Section 2.09 below, this Section 2.08
will be effective on execution of this Fourth Amendment and will survive any
expiration hereof.

Section 2.09  Effectiveness.  The Agreement is hereby amended, subject to, and
effective upon (i) occurrence of the Redemption Date, and (ii) there being no
order, judgment, decree or writ from an authorized judicial or administrative
body that is in effect and restrains, enjoins or otherwise prohibits
consummation of the optional redemption of the Notes under the Indenture, with
each of the foregoing being conditions subsequent to this Fourth Amendment.  For
the avoidance of doubt, in the event that the Redemption Date has not occurred
by [*], 2011, this Fourth Amendment shall automatically expire and be of no
further force or effect.

[Signature Page Follows]

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IN WITNESS WHEREOF, the Parties hereto have caused this Fourth Amendment to be
duly executed, all as of the date first written above.

 

NPS PHARMACEUTICALS, INC.

    By: /s/ Francois Nader Name: Francois Nader Title:

President & Chief Executive Officer

    AMGEN INC.     By:

/s/ Robert A. Bradway

Name: Robert A. Bradway Title:

President & Chief Operating Officer

   

Acknowledged and agreed to by:

  CINACALCET ROYALTY SUB LLC     By: /s/ Edward Stratemeier Name: Edward
Stratemeier Title: Manager

[Signature Page to Fourth Amendment]