Sienna Biopharmaceuticals Appoints Erle Mast, Former CFO and Co-Founder of Clovis Oncology, to Board of Directors

WESTLAKE VILLAGE, Calif., June 14, 2017 -- Sienna Biopharmaceuticals, Inc., a privately held, clinical-stage biopharmaceutical company focused on bringing innovations in biotechnology to the discovery, development and commercialization of first-in-class, targeted, topical products in medical dermatology and aesthetics, today announced that Erle Mast has been appointed to Sienna’s Board of Directors. Mr. Mast will chair the Audit Committee.

“We are pleased to announce Erle’s appointment to the Sienna Board,” said Keith R. Leonard Jr., Chairman of Sienna’s Board of Directors. “He brings more than 30 years of experience in corporate finance, biopharmaceutical operations and public-company executive leadership. He has taken two start-up companies public, one of which he helped co-found, and then helped to grow both of them into multi-billion dollar companies. We believe Erle’s extensive experience and seasoned judgment will be a critical addition to Sienna’s Board as we build this enterprise.”

“I am excited to join the board of such a well-managed company at the forefront of innovation in topical dermatology,” said Mr. Mast. “Sienna’s pipeline has the potential to address the unmet needs of a remarkably large patient population burdened by skin conditions that negatively impact confidence and daily life. I look forward to collaborating with my fellow directors and this fine management team as we work toward exciting times ahead.”

About Erle Mast

Mr. Mast was one of the co-founders of Clovis Oncology, Inc. (NASDAQ:CLVS) and served as executive vice president and chief financial officer from the company’s inception in April 2009 until his retirement in March 2016. Prior to that, he served as executive vice president and chief financial officer of Pharmion Corporation from 2002 to 2008, as vice president of finance at Dura Pharmaceuticals, Inc. from 1997 to 2000 and as chief financial officer for the global biopharmaceuticals business of Elan Pharma International, the successor to Dura, from 2000 and 2002. From 1984 to 1997, Mr. Mast held roles of increasing responsibility at Deloitte & Touche LLP, serving most recently as audit partner. He is currently a member of the board of directors of Zogenix, Inc. (NASDAQ:ZGNX), and previously served on the boards of directors and audit committees of Receptos, Inc., Somaxon Pharmaceuticals, Inc. and Verus Pharmaceuticals, Inc. Mr. Mast received a Bachelor of Science in business administration from California State University, Bakersfield.

About Sienna Biopharmaceuticals

Sienna Biopharmaceuticals, Inc., is a clinical-stage biopharmaceutical company focused on bringing innovations in biotechnology to the discovery, development and commercialization of first-in-class, targeted, topical products in medical dermatology and aesthetics. Sienna is focused on developing an innovative, diversified, multi-asset pipeline of safe and effective topical therapies to address unmet needs and enhance the health, appearance and quality of life of dermatology and aesthetics patients. Sienna is led by a team of accomplished scientists, clinicians and business leaders who have developed and commercialized leading global brands in dermatology and aesthetics.

For more information, visit the Company’s website at www.SiennaBio.com.

Contact (Investors and Media):

Ric Peterson
Chief Financial Officer
[email protected]
818-629-2232

Sean Andrews
Senior Director, Investor Relations
[email protected]
818-629-2244