AMENDMENT NO. 4 TO SUBLICENSE AGREEMENT

THIS AMENDMENT NO. 4 TO SUBLICENSE AGREEMENT (the "Amendment") is made and entered into as of September 17, 2015 ("Amendment Effective Date") and amends the Sublicense Agreement effective as of February 16, 2012, as amended pursuant to that certain Amendment to Sublicense Agreement dated December 11, 2012, Amendment No. 2 to Sublicense Agreement dated January 7, 2013, and Amendment No. 3 to Sublicense Agreement dated February 27, 2015 (the "Sublicense Agreement") by and between Ligand Pharmaceuticals Incorporated, a corporation organized under the laws of Delaware and having a place of business at 11119 North Torrey Pines Road, Suite 200, La Jolla, CA, 92037 and its wholly owned subsidiary, Pharmacopeia, LLC (as successor in interest to Pharmacopeia Drug Discovery Inc.) ("PCOP"), a limited liability company organized under the laws of Delaware and having a place of business at 11119 North Torrey Pines Road, Suite 200, La Jolla, CA, 92037 (collectively, Ligand Pharmaceuticals Incorporated and PCOP shall be known as "Ligand") and Retrophin, Inc., a corporation organized under the laws of Delaware and having a place of business at 12255 El Camino Real, San Diego, CA 92130 ("Retrophin").

WHEREAS Ligand and Retrophin have previously entered into the Sublicense Agreement pursuant to which Ligand sublicensed to Retrophin rights under the License Agreement dated March 27, 2006 between PCOP and Bristol-Myers Squib Company (the “Upstream License”); and

WHEREAS, Ligand and Retrophin desire to amend certain terms of the Sublicense Agreement and the Upstream Agreement as set forth herein.

NOW, THEREFORE, in consideration of the foregoing premises and the mutual covenants contained herein, the Parties, intending to be legally bound, agree as follows:

1.Capitalized Terms. The capitalized terms used herein and not otherwise defined shall have the same definitions as provided in the Sublicense Agreement

2.Amendments to Milestone Payments.

3.Consideration. Retrophin shall pay Ligand (i) $850,000 in consideration for the amendments set forth in this Amendment, and (ii) $150,000 for the efforts to amend the Upstream License Agreement in accordance with Section 4 of this Amendment, in each case such payment shall be non-refundable and shall be made within 5 days of execution of this Amendment by both parties.

(a)Ligand will use reasonable best efforts to obtain a waiver of Sections 3.1 and 13.2.5 by BMS for the Asia Pacific Region. “Asia Pacific Region” means Japan, China, S. Korea, Taiwan, Thailand and Vietnam.

(b)Ligand will use reasonable best efforts to obtain BMS’ agreement to the standby license provided by Section 2.2.2(v) in which event, Section 2.2.2(v) would be amended substantially in the form of the following language:

“…provided, that, that such sublicensed rights shall not terminate if, as of the effective date of termination by BMS under Section 13.2, the Sublicensee is not in material default under its license agreement with Ligand in which case Sublicensee will assume all of Ligand’s rights and obligation under this Sublicense Agreement and be bound directly to BMS substituting Sublicensee for Ligand and subject to the payment to Ligand of all royalties and milestones under the sublicense agreement to the extent they exceed payments due to BMS under this Sublicense Agreement and payment to BMS of all royalties and milestones under this Upstream Agreement.”

(c)Ligand will use reasonable best efforts to obtain BMS’s agreement to the following amendments to the termination provisions of the Upstream Agreement.

“[…***…]”

“Ligand will […**…]”

(d)For the avoidance of doubt, any such efforts by Ligand made under this Sublicense Agreement shall not require Ligand to pay BMS any fee or concede and existing rights, but rather shall solely involve the use of logic and reason to seek to persuade BMS.

“1.70 “Asia Pacific Region” means Japan, China, S. Korea, Taiwan, Thailand and Vietnam.”

“…provided however, that such sublicensed rights shall not terminate if, as of the effective date of termination by Ligand under Article 13, the Sublicensee is not in material default under its license agreement with Retrophin in which case Sublicensee will assume all of Retrophin’s rights and obligation under this Sublicense Agreement and be bound directly to Ligand respectively substituting Sublicensee for Retrophin and subject to the payment to Retrophin of all royalties and milestones under the sublicense

agreement to the extent they exceed payments due to Ligand under this Sublicense Agreement and payment to Ligand of all royalties and milestones under this Sublicense Agreement to the extent they exceed payments due to BMS under the Upstream Agreement.”

“3.2.4 The provisions of Sections 3.2.1 and 3.2.2 shall not apply within the Asia Pacific Region.”

“Retrophin may terminate this Agreement for convenience upon […**…] ([…***…]) days prior written notice to Ligand and all of the provisions of Section 13.4 will survive termination of this Agreement pursuant to this Section 13.3.”

“[…***…]”

“Retrophin will […***…]

7.No Other Amendments. Except as provided herein, the Sublicense Agreement shall continue in full force and effect.

IN WITNESS WHEREOF, the Parties have executed this Amendment to Sublicense Agreement through their duly authorized representatives to be effective as of the Amendment Effective Date.

By:    /s/ Charles Berkman        By:    /s/ Laura Clague    

Name:    Charles Berkman         Name:    Laura Clague    

Title:     VP, General Counsel & Secretary         Title:    Chief Financial Officer