Sienna Biopharmaceuticals Announces First Patient Dosed in First-in-Human Trial of Topical SNA-125

— Trial to Enroll Approximately 15 Patients with Psoriasis
— Top-Line Results Expected in Third Quarter of 2018

WESTLAKE VILLAGE, Calif., Feb. 14, 2018 (GLOBE NEWSWIRE) — Sienna Biopharmaceuticals, Inc. (NASDAQ:SNNA) today announced that the first patient has been dosed in the Company’s first-in-human, Phase 1/2 proof-of-concept clinical trial of topical product candidate SNA-125 in the treatment of psoriasis and the associated pruritus, or itch. SNA-125 is designed to inhibit janus kinase 3, or JAK3, and tropomyosin receptor kinase A, or TrkA, with minimal to no systemic exposure. JAK3 is a validated target in psoriasis, atopic dermatitis and pruritus. JAK3 is required for immune cell development, and inhibiting JAK3 blocks the signaling of key cytokines, such as interleukin-17A, or IL-17A, IL-17F, IL-2 and tumor necrosis factor-alpha, or TNF-α, which results in a reduction in the severity of autoimmune and inflammatory diseases in which those cytokines play a pivotal role. TrkA is the high affinity receptor for nerve growth factor, or NGF, a known mediator of neurogenic inflammation and itch associated with psoriasis. This multicenter, randomized, double-blind, placebo- and comparator-controlled, intra-individual trial will evaluate the safety, tolerability and efficacy of SNA-125 compared to vehicle and other reference formulations in approximately 15 patients with chronic psoriasis.

“We are excited to now have two product candidates from our Topical by Design™ platform in the clinic,” said Frederick C. Beddingfield III, M.D., Ph.D., President and Chief Executive Officer of Sienna. “This week, we dosed our first patient in the SNA-125 proof-of-concept trial for psoriasis and expect to report top-line data in the third quarter of 2018. Last quarter, we dosed our first patient in the SNA-120 Phase 2b clinical trial for pruritus and the associated underlying psoriasis and expect to report top-line data in the first half of 2019. Soon, we plan to initiate the SNA-125 proof-of-concept trial for atopic dermatitis and expect those data in the second half of 2018.”

“In nonclinical studies to date, SNA-125 has demonstrated strong inhibition of JAK3 and TrkA as well as cytokine modulation similar to tofacitinib,” said Paul F. Lizzul, M.D., Ph.D., Chief Medical Officer of Sienna. “JAK3 is known to significantly reduce the severities of psoriasis, atopic dermatitis and associated pruritus, though oral JAK3 inhibitors are not particularly well tolerated. Our goal with this proof-of-concept trial, using the validated psoriasis plaque test, is to gain early clinical insight into the safety, tolerability and efficacy of SNA-125 as a topical treatment for psoriasis.”

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. The Company’s objective is to develop an innovative, diversified, multi-asset pipeline of topical therapies that enhance the health, appearance and quality of life of dermatology and aesthetics patients. Sienna is led by a management team with extensive experience in product development and commercialization at several leading dermatology, aesthetics and biotechnology companies.

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

Forward-Looking Statements

This press release contains forward-looking statements, including but not limited to the statements by Sienna’s Chief Executive Officer and Chief Medical Officer and other statements regarding Sienna’s expectations regarding its Phase 1/2 proof-of-concept clinical trials of SNA-125 and Phase 2b clinical trial of SNA-120, including the number of patients it anticipates will participate and expected timing related to the studies’ start, completion and data reporting. Such forward-looking statements involve substantial risks and uncertainties that could cause Sienna’s clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including the clinical trial enrollment process, the regulatory approval processes, the timing of regulatory filings, the challenges associated with manufacturing drug products, Sienna’s ability to successfully protect and defend its intellectual property, and other matters that could affect the sufficiency of existing cash to fund operations and the availability or commercial potential of Sienna’s product candidates. Sienna undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the Company in general, see Sienna’s most recent Quarterly Report on Form 10-Q and any subsequent current and periodic reports filed with the Securities and Exchange Commission.

Contact (Investors and Media):

Ric Peterson
Chief Financial Officer
rpeterson@siennabio.com
818-629-2232

Sean Andrews
Senior Director, Investor Relations
sandrews@siennabio.com
818-629-2244