EXHIBIT 10.1

THIRD AMENDMENT TO THE EMPLOYMENT AGREEMENT

BY AND BETWEEN

HUMAN GENOME SCIENCES, INC. AND H. THOMAS WATKINS

WHEREAS, HUMAN GENOME SCIENCES, INC. (the “Company”) and H. THOMAS WATKINS
(“Executive”) have entered into an employment agreement, dated as of
November 21, 2004, as amended by the first and second amendments thereto (the
“Employment Agreement”) and a letter agreement, dated December 18, 2007 under
which the Executive participates in the Company’s Second Amended and Restated
Key Executive Severance Plan (the “KESP Participation Letter”);

WHEREAS, the Company and Executive now desire to further amend the Employment
Agreement the KESP Participation Letter to ensure compliance with Section 409A
of the Internal Revenue Code of 1986, as amended, and the Treasury regulations
and other guidance promulgated thereunder; and

WHEREAS, Section 14 of the Employment Agreement provides that all amendments
must be in writing signed by both parties;

NOW, THEREFORE, the Employment Agreement is hereby amended as follows:

1. Section 13 is hereby amended by deleting the last sentence thereof and
replacing it with the following text:

“In the event that Executive becomes entitled to receive payments and benefits
under this Agreement and under the Severance Plan due to a separation from
service, he shall be entitled to the payments and benefits under the Severance
Plan; provided, however, that such payments and benefits shall be paid net of
the payments and benefits, if any, received under this Agreement prior to
Executive becoming entitled to receive payments and benefits under the Severance
Plan and Executive shall cease to receive payments and benefits under this
Agreement upon becoming entitled to receive payments and benefits under the
Severance Plan. For the avoidance of doubt, the severance payments and benefits
under this Agreement and the Severance Plan shall not be paid in duplication of
each other.”

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2. Section 18(i)(i) is hereby amended in its entirety to read as follows:

“This Agreement is intended to comply with, or otherwise be exempt from,
Section 409A of the Code and any regulations and Treasury guidance promulgated
thereunder and this Agreement shall be so construed.”

3. Section 18(i) is hereby amended by adding a new subparagraph (vii) to read as
follows:

“(vii) Timing of Severance Pay After Execution of a Release. If under the terms
of the Agreement or the Severance Plan the execution of a general release of
claims is a condition precedent to Executive receiving severance or other
benefits under the Agreement or the Severance Plan, the Company will provide
Executive with the form of release agreement on or within fourteen days after
Executive’s separation from service. To be entitled to the severance or other
benefits, Executive must execute and deliver to the Company the release
agreement on or before the last day of the minimum required waiver consideration
period provided under the Age Discrimination in Employment Act or other
applicable law or such other date as may be specified in the release agreement.
If Executive timely delivers an executed release agreement to the Company, and
Executive does not revoke the release agreement during the minimum revocation
period required under applicable law, if any, the severance or other benefits
shall be paid or commence being paid, as applicable, on or after the date on
which the release agreement becomes effective in accordance with the terms of
the Agreement or the Severance Plan, as applicable; subject, however, to any
six-month delay that may be required under Section 409A of the Code for payments
of deferred compensation to specified employees (the “Specified Employee Rule”).
If, however, the period during which Executive has discretion to execute and/or
revoke the release agreement straddles two calendar years, the severance or
other benefits, to the extent such payments and benefits constitute deferred
compensation within the meaning of Section 409A of the Code, shall be paid or
commence being paid, as applicable, as soon as practicable in the second of the
two calendar years, regardless of within which calendar year Executive actually
delivers the executed release agreement to the Company, subject to the release
agreement first becoming effective and subject to the Specified Employee Rule,
if applicable. Consistent with Section 409A of the Code, Executive may not,
directly or indirectly, designate the calendar year of payment. Nothing in this
paragraph shall be construed to alter the terms of the Agreement or the
Severance Plan that condition Executive’s entitlement to any severance or other
benefits upon

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Executive’s compliance with restrictive covenants and any other terms and
conditions specified in the Agreement or the Severance Plan.”

4. In all other respects, the Employment Agreement is hereby ratified and
confirmed.

IN WITNESS WHEREOF, the Company and Executive hereby amend the Employment
Agreement and, as referenced by the amendment to Section 18(i) of the Employment
Agreement, the KESP Participation Letter, effective as of July 18, 2011.

 

H. THOMAS WATKINS    WITNESS:

        /s/ H. Thomas Watkins

  

        /s/ Cindy Tracy

HUMAN GENOME SCIENCES, INC.

   ATTEST:

By:

  

        /s/ James H. Davis

  

        /s/ Rose Hadidian

   James H. Davis, Ph.D.   

Title: Executive Vice President and General Counsel