Syndax Announces Expansion of Immuno-Oncology Collaboration Evaluating Entinostat in Combination with KEYTRUDA® (pembrolizumab) for the Treatment of Colorectal Cancer

WALTHAM, Mass., April 27, 2017 -- Syndax Pharmaceuticals, Inc. (NASDAQ:SNDX), today announced the expansion of ENCORE 601/KEYNOTE 142, the ongoing Phase 2 clinical collaboration with a subsidiary of Merck, known as MSD outside the United States and Canada, to include a cohort of patients with microsatellite stable colorectal cancer. This trial is designed to evaluate the safety, tolerability and efficacy of Syndax’s entinostat, an oral, small molecule that targets immune regulatory cells, in combination  with KEYTRUDA^® (pembrolizumab), Merck’s anti-PD-1 (programmed death receptor-1) therapy.

“Microsatellite stable colorectal cancers comprise approximately 85% of colorectal cancers, have limited treatment options once the disease advances, and have been unresponsive to anti-PD-1 monotherapy,” said Briggs W. Morrison, M.D., Chief Executive Officer of Syndax. “This expansion of ENCORE 601/KEYNOTE 142 is based in part on the previously communicated clinical responses we observed for the entinostat-KEYTRUDA combination in advanced melanoma patients that had progressed on prior anti-PD-1 therapy.”

ENCORE 601 continues to evaluate the combination of entinostat and KEYTRUDA in patients with advanced melanoma or non-small cell lung cancer (NSCLC) who have experienced disease progression following treatment with an anti-PD-1 therapy, and patients with NSCLC who are naïve to treatment with a PD-1 or PD-L1 antagonist. In March 2017, Syndax announced that the melanoma cohort achieved the pre-specified criteria required to advance to the second stage of the trial, and re-opened enrollment of that cohort. The Company will present results from the first stage of the melanoma cohort at the upcoming American Society of Clinical Oncology Annual Meeting in June. A decision on whether the two NSCLC cohorts can proceed to the second stage of the trial is expected in 2Q17.

Financial and other terms of the initial agreement, as well as the amendment covering the expanded collaboration between Syndax and Merck, were not disclosed.

About Syndax Pharmaceuticals, Inc.

Syndax is a clinical stage biopharmaceutical company developing an innovative pipeline of cancer therapies. 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. Given its potential ability to block the function of immune suppressive cells in the tumor microenvironment, entinostat is also being evaluated in combination with approved PD-1 antagonists. Ongoing Phase 1b/2 clinical trials combine entinostat with KEYTRUDA from Merck & Co., Inc. for non-small cell lung cancer and melanoma; with TECENTRIQ from Genentech, Inc. for TNBC; and with BAVENCIO from Pfizer Inc. and Merck KGaA, Darmstadt, Germany, for ovarian cancer. Our second product candidate, SNDX-6352, is a monoclonal antibody that blocks the CSF-1 receptor and may also block the function of immune suppressive cells in the tumor microenvironment. 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. 

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 our product candidates 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.

KEYTRUDA^® is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc.

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