Certain Common Stock of Sienna Biopharmaceuticals, Inc. are subject to a Lock-Up Agreement Ending on 22-JAN-2018. These Common Stock will be under lockup for 180 days starting from 26-JUL-2017 to 22-JAN-2018. Details: The directors, executive officers and substantially all of company's stockholders and option holders have agreed, subject to certain exceptions, with the underwriters not to dispose of or hedge any shares of company’s common stock or securities convertible into or exchangeable for shares of common stock during the period from the date of the lock-up agreement continuing through the date 180 days after the date of this prospectus, except with the prior written consent of JP Morgan Securities LLC and Cowen and Company, LLC.