Exhibit 10.1

*** INDICATES MATERIAL THAT WAS OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT WAS REQUESTED. ALL SUCH OMITTED MATERIAL WAS FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

SECOND AMENDMENT TO THE COLLABORATION AGREEMENT

     This Second Amendment (“ Second Amendment ”) to the Collaboration Agreement is effective as of the Second Amendment Effective Date (as set forth in Section 4 of this Second Amendment), by and between UCYCLYD PHARMA, INC. , a Maryland corporation, with its principal place of business at 7720 North Dobson Road, Scottsdale, AZ 85256 (“ Ucyclyd ”) and HYPERION THERAPEUTICS, INC. , a Delaware corporation, with its principal place of business at 601 Gateway Blvd., Suite 200, South San Francisco, CA 94080 (hereunder referred to as “ Hyperion ”). Ucyclyd and Hyperion are sometimes referred to herein individually as a “ Party ” and collectively as the “ Parties .”

RECITALS

      WHEREAS , Ucyclyd and Hyperion entered into that certain Collaboration Agreement dated August 23, 2007 (the “ Collaboration Agreement ”), as amended by the First Amendment on November 24, 2008;

      WHEREAS , Ucyclyd and Hyperion desire to amend the Collaboration Agreement as more fully set forth in this Second Amendment; and

      WHEREAS , in partial consideration of Ucyclyd agreeing to the modifications set forth in this Second Amendment, Hyperion has agreed to sell five percent (5%) of its common stock to Ucyclyd and concurrent with the signing of this Second Amendment, the Parties have entered into a Common Stock Purchase Agreement (the “ Transaction Document ”).

      NOW, THEREFORE , in consideration of the foregoing recitals (which are incorporated by reference into this Second Amendment), and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties hereto agree as follows:

1. Capitalized Terms . All capitalized terms not otherwise defined in this Second Amendment shall have the meanings ascribed to them as set forth in the Collaboration Agreement.

2. Amendments.

“ Development Field ” means the treatment of any human disease, disorder or condition, including but not limited to UCD, HE or Hyperammonemia.

Notwithstanding the amendment set forth above, Hyperion acknowledges and affirms: (i) its obligations under Section 2.2 of the Agreement including Hyperion’s agreement that the primary focus of its efforts under the Development and Regulatory Program is to obtain Regulatory Approval first in the United States for GT4P in UCD and HE; and (ii) Hyperion does not have any rights to further develop Ammonul HE during the Development Term.

“ 2.2.2 R&D Rights of Third Parties .

     (a) Hyperion acknowledges that, prior to the Second Amendment Effective Date, Ucyclyd has granted Third Parties certain rights under the Distribution Agreements (as such term has been amended based on changes to Schedule 1.30 pursuant to this Second Amendment) with respect to research and development of the Products for uses within the Development Field (the “ Pre-existing Rights ”) and that Hyperion’s exclusive license in Section 8.2 is subject to such Pre-existing Rights.

     (b) From the Second Amendment Effective Date until the termination or expiration of the Development Term, Ucyclyd agrees not to grant (i) such Third Parties or any new Third Parties any further rights with respect to GT4P for uses within the Development Field; and (ii) distribution rights to the Marketed Products in the United States to a Third Party which will extend past the Closing Date. The Parties acknowledge and agree that because the Closing Date is based on the occurrence of certain events described in Section 3.1 (Purchase Rights) , the exact date cannot be determined accurately and the Parties can rely only upon the dates on which the Closing is anticipated to occur based on the Development Plan in effect as of the Second Amendment Effective Date. Based on such Development Plan, the Closing Date is anticipated to be ***, which shall be the date relied upon with respect to the foregoing limitation; provided, however, that the date will be adjusted automatically if the events on which it is based change in the Development Plan or the events have not occurred by such date (as may be adjusted based on the foregoing) and the Parties agree to extend the date for a Closing under the Agreement.

     (c) During the Development Term, Ucyclyd reserves the right to grant Third Parties that currently or in the future distribute the Marketed Products the right to conduct research and development with respect to the Marketed Products for purposes of (i) obtaining Regulatory Approval for the Marketed Products in the applicable country or region, (ii) conducting post-marketing approval studies, and (iii) conducting any other studies or activities required by the applicable Regulatory Agency.

     (d) During the Development Term, Ucyclyd shall have the right to support investigator-sponsored activities or investigator-sponsored use of the Marketed Products for uses within the Development Field and will keep Hyperion apprised of such activities through the JSC meetings.

     (e) During the Development Term, Ucyclyd may support investigator-sponsored activities or investigator-sponsored use of GT4P only after allowing Hyperion to review such activities in advance and obtaining Hyperion’s approval of such activities.”

Second Amendment to Collaboration Agreement

“ R&D Rights Outside of the United States .

     (a) During the Development Term, Hyperion shall have the right to conduct research and development activities outside of the United States in support of Hyperion’s efforts to obtain Regulatory Approval in the United States, except in those jurisdictions where such research and development efforts would conflict with the rights granted to Third Parties pursuant to the Pre-existing Rights.

     (b) Subject to any Pre-existing Rights, during the Development Term, Hyperion shall have the right to propose to the JSC research and development activities outside of the United States in connection with obtaining Regulatory Approval for the Development Products outside of the United States. Ucyclyd shall advise Hyperion whether the conduct of any such activities would conflict with any rights granted to Third Parties that are in addition to the Pre-existing Rights. To the extent such proposed activities do not conflict with any Third Party rights, Hyperion shall have the right to perform such proposed activities. In the event that Hyperion conducts any research and development activities outside of the United States as permitted in this Section, Hyperion shall coordinate all such activities with Ucyclyd through the JSC during the Development Term.”

“ Closing . The Parties will mutually agree upon a closing date (the “ Closing Date ”), which shall occur not later than *** following, as applicable: (a) the GT4P Approval Date, (b) Hyperion’s exercise of the Purchase Option #1 or (c) the Purchase Option #2 End Date.

(a) On the Closing Date, Hyperion shall become obligated to pay Ucyclyd the Purchase Price, Purchase Option Price #1 or Purchase Option Price #2, as applicable (the “ Purchase Price Amount ”) in accordance with Section 3.3.3.

(b) On the Closing Date the Parties shall execute and deliver all documents set forth below (the “ Purchase Transaction Documents ”), under which Ucyclyd shall sell, transfer, assign and convey all Assets to Hyperion:

     (i) a Bill of Sale in the form attached to the Agreement as Exhibit 4 (Bill of Sale) , under which Ucyclyd transfers the ownership of certain Assets (including all Inventories) to Hyperion, which shall be signed by both Ucyclyd and Hyperion;

     (ii) a Technology Assignment Agreement in the form attached to the Agreement as Exhibit 5 (Technology Assignment Agreement) , under which Ucyclyd shall assign all Product Technology and Developed Technology, which shall be signed by Ucyclyd;

     (iii) an Assignment and Assumption Agreement of all Assigned Agreements in the form attached to the Agreement as Exhibit 6 (Assignment and Assumption Agreement) , which shall be countersigned by Ucyclyd and accompanied by all consents required from the applicable Third Parties to such Assigned Agreements to Hyperion as attachments to such Assignment and Assumption Agreement;

Second Amendment to Collaboration Agreement

     (iv) a Note in the form attached to the Agreement as Exhibit 9 (Note) ; and

     (v) a Security Agreement in the form attached to the Agreement as Exhibit 10 (Security Agreement) .”

“ Payment of Purchase Price Amount .

     (a) The Purchase Price Amount shall be due and payable *** commencing on the first Business Day of the *** following the Closing Date and continuing on the first Business Day of *** thereafter in accordance with the terms and conditions of the Note. Hyperion’s obligations under the Not