X0306 4 2019-07-02 false 0001656328 Sienna Biopharmaceuticals, Inc. SNNA 0001711464 Andrews Timothy K. C/O SIENNA BIOPHARMACEUTICALS, INC. 30699 RUSSELL RANCH ROAD, SUITE 140 WESTLAKE VILLAGE CA 91362 false true false false General Counsel & Secretary Common Stock 2019-07-02 4 F false 4095.00 0.76 D 95558.00 D Common Stock 15000.00 I See Footnote Common Stock 10000.00 I See Footnote Represents shares otherwise issuable to the Reporting Person that were withheld to satisfy the Issuer's tax withholding obligation upon settlement of restricted stock units. This transaction was executed in multiple trades in prices ranging from $0.72 to $0.83, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote. Includes a total of 2,916 shares of the Issuer's common stock acquired pursuant to the Issuer's Employee Stock Purchase Plan. The shares are held by Steelhead Bioventures LLC, a limited liability company in which the Reporting Person holds a controlling interest. The shares are held directly by the Andrews Living Trust (the "Trust"), of which the Reporting Person serves as co-trustee. The Reporting Person and members of his immediate family are beneficiaries of the Trust. The Reporting Person disclaims beneficial ownership of the shares of the Issuer's common stock held by the Trust except to the extent of his pecuniary interest therein. /s/ Timothy K. Andrews 2019-07-03