Syndax Announces Presentations at the 2017 American Association for Cancer Research Annual Meeting

WALTHAM, Mass., March 29, 2017 -- Syndax Pharmaceuticals, Inc. ("Syndax," the "Company" or "we") (Nasdaq:SNDX), a clinical stage biopharmaceutical company focused on developing entinostat and SNDX-6352 in multiple cancer indications, announces a list of select poster presentations featuring entinostat at the upcoming American Association for Cancer Research (AACR) Annual Meeting being held April 1-5, 2017 in Washington, D.C. The abstracts feature new data and insight into how entinostat alters the cancer cell and tumor microenvironment to enhance immunotherapeutic approaches in renal, lung, breast, and pancreatic cancer models.

Key Entinostat Posters of Interest:

Title: Induced MHCII expression on breast cancer cells broadens the responding T cell repertoire, delays tumor-specific T cell exhaustion, and impairs tumor growth
Abstract Number: 643
Location: Section 27
Date and Time: Sunday, April 2 from 1:00-5:00 PM ET

Title: Epigenetic modulation of the tumor microenvironment enhances vaccine induced T cell responses in a murine model of pancreatic cancer
Abstract Number: 1686
Location: Section 29
Date and Time: Monday, April 3 from 8:00 AM-12:00 PM ET

Title: Promotion of immunogenicity using epigenetic modulation and immune checkpoint inhibition in mouse models of breast cancer
Abstract Number: 3667
Location: Section 27
Date and Time: Tuesday, April 4 from 8:00 AM-12:00 PM ET

Title: Harnessing epigenetic reprogramming by histone deacetylase inhibitor MS275 for pancreatic cancer therapy
Abstract Number: 5065
Location: Section 2
Date and Time: Wednesday, April 5 from 8:00 AM-12:00 PM ET

Title: HDAC inhibitor Entinostat disrupts function of PMN-MDSC
Abstract Number: 5595
Location: Section 24
Date and Time: Wednesday, April 5 from 8:00 AM-12:00 PM ET

About Syndax Pharmaceuticals, Inc.

Syndax is a clinical stage biopharmaceutical company focused on developing an innovative pipeline of combination therapies in multiple cancer indications. Our lead product candidate, entinostat, which was granted Breakthrough Therapy designation by the FDA following positive results from our Phase 2b clinical trial, ENCORE 301, is currently being evaluated in a Phase 3 clinical trial for advanced hormone receptor positive, human epidermal growth factor receptor 2 negative breast cancer. Syndax is developing entinostat, which has direct effects on both cancer cells and immune regulatory cells, and SNDX-6352, an anti-CSF-1R monoclonal antibody, to enhance the body's immune response on tumors that have shown sensitivity to immunotherapy. Entinostat is being evaluated as a combination therapeutic in Phase 1b/2 clinical trials with Merck & Co., Inc. for non-small cell lung cancer and melanoma; with Genentech, Inc. for TNBC; and with Pfizer Inc. and Merck KGaA, Darmstadt, Germany, for ovarian cancer. SNDX-6352 is being evaluated in a single ascending dose Phase 1 clinical trial and is expected to be developed to treat a variety of cancers. For more information on Syndax, please visit www.syndax.com.

Syndax's Cautionary Note on Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "expect," "plan," "anticipate," "estimate," "intend," "believe" and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These forward-looking statements are based on Syndax's expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties. Actual results may differ materially from these forward-looking statements. Forward-looking statements contained in this press release include, but are not limited to, statements about the progress, timing, clinical development and scope of clinical trials and the reporting of clinical data for Syndax's product candidates, and the potential use of SNDX-6352 to treat various cancer indications. Many factors may cause differences between current expectations and actual results including unexpected safety or efficacy data observed during preclinical or clinical studies, clinical trial site activation or enrollment rates that are lower than expected, changes in expected or existing competition, changes in the regulatory environment, failure of Syndax's collaborators to support or advance collaborations or product candidates and unexpected litigation or other disputes. Other factors that may cause Syndax's actual results to differ from those expressed or implied in the forward-looking statements in this press release are discussed in Syndax's filings with the U.S. Securities and Exchange Commission, including the "Risk Factors" sections contained therein. Except as required by law, Syndax assumes no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

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