– SY-1425 Inhibited Tumor Growth as a Single Agent in Preclinical Models of Drug-Resistant Breast Cancer with High RARA Gene Expression –

– SY-1425 in Combination with Standard-of-Care Breast Cancer Therapies Shows Synergistic Effects in Multiple Preclinical Models –

– Data Highlighted in Late-Breaking Presentation at San Antonio Breast Cancer Symposium –

CAMBRIDGE, Mass. -- (Business Wire)

Syros Pharmaceuticals (NASDAQ: SYRS) today announced the presentation of new data on SY-1425, its first-in-class selective retinoic acid receptor alpha (RARα) agonist, showing that SY-1425 inhibited tumor growth in multiple preclinical models of breast cancer driven by high levels of RARA gene expression. In these studies, SY-1425 showed significant anti-proliferative activity both as a single agent and in combination with standard-of-care breast cancer therapies in in vitro and in vivo models of breast cancer, including those resistant to existing treatments. These data were presented at the 39^th Annual San Antonio Breast Cancer Symposium (SABCS).

“Despite tremendous progress in treating certain types of breast cancer, two of the greatest remaining challenges are our ability to identify the right treatment for the right patient and cancer’s ability to become resistant to treatment,” said Nancy Simonian, M.D., Chief Executive Officer of Syros. “The new data on SY-1425 show that we have the potential to address both these challenges for subsets of breast cancer patients whose disease is driven by abnormally high expression of the RARA gene.”

The data presented at SABCS show that subsets of breast cancer patients’ tumors have a highly specialized region of regulatory DNA, known as a super-enhancer, that is associated with the RARA gene and drives high levels of RARA gene expression. In preclinical models of breast cancer, high RARA gene expression was shown to be predictive of response to treatment with SY-1425. The data highlight that SY-1425:

• Inhibited tumor growth in breast cancer cell lines as well as cell line-derived xenograft and patient-derived xenograft models of breast cancer with high RARA gene expression, including models of HER2-positive breast cancer resistant to treatment with trastuzumab and ER-positive breast cancer resistant to hormonal therapies. By contrast, SY-1425 did not inhibit tumor growth in models of breast cancer with low RARA gene expression.
• Reduced the expression of genes responsible for tumor growth in HER2-positive and ER-positive breast cancer cells with high RARA expression.
• Increased the anti-tumor effects of standard-of-care therapies, including tamoxifen and palbociclib in ER-positive breast cancer cells with high RARA expression and lapatinib in HER2-positive breast cancer cells with high RARA expression.

These data support the potential clinical development of SY-1425 in genomically defined subsets of breast cancer patients.

SY-1425 is currently in a Phase 2 clinical trial in genomically defined subsets of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients. Using its gene control platform, Syros discovered subsets of AML, MDS and breast cancer patients whose tumors have the super-enhancer associated with the RARA gene, which codes for the RARα transcription factor. The resulting over-expression of RARα locks the cells in an immature, undifferentiated and proliferative state. Treatment with SY-1425 in cancer cells with this super-enhancer promotes differentiation of these cells. Upon achieving clinical proof-of concept in AML and MDS, Syros plans to expand development of SY-1425 into genomically defined subsets of breast cancer patients.

SY-1425 is approved in Japan as Amnolake^® (tamibarotene) to treat relapsed or refractory APL, a form of AML that is driven by a fusion of the RARA gene with other genes. Syros in-licensed SY-1425 for development and commercialization in North America and Europe in cancer. Additional details about the ongoing Phase 2 trial in AML and MDS can be found using the identifier NCT02807558 at www.clinicaltrials.gov.

About Syros Pharmaceuticals
Syros Pharmaceuticals is pioneering the understanding of the non-coding region of the genome to advance a new wave of medicines that control expression of disease-driving genes. Syros has built a proprietary platform that is designed to systematically and efficiently analyze this unexploited region of DNA in human disease tissue to identify and drug novel targets linked to genomically defined patient populations. Because gene expression is fundamental to the function of all cells, Syros’ gene control platform has broad potential to create medicines that achieve profound and durable benefit across a range of diseases. Syros is currently focused on cancer and immune-mediated diseases and is advancing a growing pipeline of gene control medicines. Syros’ lead drug candidates are SY-1425, a selective RARα agonist in a Phase 2 clinical trial for genomically defined subsets of patients with acute myeloid leukemia and myelodysplastic syndrome, and SY-1365, a selective CDK7 inhibitor with potential in a range of solid tumors and blood cancers. Led by a team with deep experience in drug discovery, development and commercialization, Syros is located in Cambridge, Mass.

Cautionary Note Regarding Forward-Looking Statements
This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995, including without limitation statements regarding the potential therapeutic benefits of treatment with SY-1425 as a single agent or in combination with other agents in genomically defined subsets of AML, MDS and breast cancer patients, as well as plans to conduct clinical trials of SY-1425 in combination with other agents. The words ‘‘anticipate,’’ ‘‘believe,’’ ‘‘continue,’’ ‘‘could,’’ ‘‘estimate,’’ ‘‘expect,’’ ‘‘intend,’’ ‘‘may,’’ ‘‘plan,’’ ‘‘potential,’’ ‘‘predict,’’ ‘‘project,’’ ‘‘target,’’ ‘‘should,’’ ‘‘would,’’ and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various important factors, including: Syros’ ability to: advance the development of its programs, including SY-1425, under the timelines it projects in current and future clinical trials; obtain and maintain patent protection for its drug candidates and the freedom to operate under third party intellectual property; demonstrate in any current and future clinical trials the requisite safety, efficacy and combinability of its drug candidates; replicate scientific and non-clinical data in clinical trials; successfully develop a companion diagnostic test to identify patients with biomarkers associated with the RARA super-enhancer; obtain and maintain necessary regulatory approvals; identify, enter into and maintain collaboration agreements with third parties; manage competition; manage expenses; raise the substantial additional capital needed to achieve its business objectives; attract and retain qualified personnel; and successfully execute on its business strategies; risks described under the caption “Risk Factors” in the company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2016, which is on file with the Securities and Exchange Commission; and risks described in other filings that the company makes with the Securities and Exchange Commission in the future. Any forward-looking statements contained in this press release speak only as of the date hereof, and Syros expressly disclaims any obligation to update any forward-looking statements, whether because of new information, future events or otherwise.

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Contacts:

Media Contact:
Syros Pharmaceuticals, Inc.
Naomi Aoki, 617-283-4298
naoki@syros.com
or
Investor Contact:
Stern Investor Relations, Inc.
Hannah Deresiewicz, 212-362-1200
hannahd@sternir.com

Source: Syros Pharmaceuticals