To: Horizon Pharma AG

Exhibit 10.1

To: Horizon Pharma AG

Xxxxxxxxxxxx 00

XX-0000 Xxxxxxx

Xxxxxxxxxxx

Mundipharma Medical Company

Xxxxxxxxxxx Xxxxx, 0xx Xxxxx

00 Xxx-xx-Xxxxx Xxxx

PO Box HM 2332

Xxxxxxxx, XX JX Bermuda

17th October 2012

Dear Sirs

Please sign where indicated below to accept the following amendment to the Second Letter Agreement dated 6th October 2011 between Mundipharma International Corporation Limited, Mundipharma Medical Company and Horizon Pharma AG.

PMR Study

Mundipharma’s requirement to initiate dosing of first patient in the PMR Study as set out in the First Letter Agreement between the parties shall be amended to “initiate submission for regulatory and ethics approval prior to December 31^st, 2012”.

Yours faithfully Mundipharma International Corporation Limited
By:		/s/ Xxxxxxx Xxxxxxxx
Name:		Xxxxxxx Xxxxxxxx
Title:		General Manager

Agreed to and accepted as of the date first set forth above:

Horizon Pharma AG						Horizon Pharma AG
By:		/s/ Xxxxxxx X. Xxxxxxx				By:		/s/ Xxxxxx X. Xxxx
Name:		Xxxxxxx X. Xxxxxxx				Name:		Xxxxxx X. Xxxx
Title:		Chairman, President, CEO				Title:		SVP Global Business Ops, Chief Compliance Officer

Mundipharma Medical Company
By:		/s/ Xxxxxxx Xxxxxxxx
Name:		Xxxxxxx Xxxxxxxx
Title:		General Manager

MUNDIPHARMA INTERNATIONAL CORPORATION LIMITED

Mundipharma House -14, Par-la-Ville Road - P.O. Box HM 2332 - Xxxxxxxx XX JX -Bermuda

Tel: (000) 000-0000 - Fax: (000) 000-0000

a member of the Mundipharma International Group