New Publication in Cancer Research Highlights Discovery of SY-1365, a First-in-Class Selective CDK7 Inhibitor, and its Promise as a Potentially Transformative Targeted Approach for Difficult-to-Treat Cancers

SY-1365 Currently in Phase 1 Clinical Trial in Relapsed and
Treatment-Resistant Ovarian and Breast Cancer Patients

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Syros Pharmaceuticals (NASDAQ: SYRS), a leader in the development of
medicines that control the expression of genes, today announced the
online publication of a new manuscript, Discovery and
Characterization of SY-1365, a Selective, Covalent Inhibitor of CDK7,
in the American Association for Cancer Research’s (AACR) journal, Cancer
Research. SY-1365, a first-in-class selective cyclin-dependent
kinase 7 (CDK7) inhibitor, is currently being investigated in a Phase 1
clinical trial as a single agent and in combination with
standard-of-care therapies in multiple ovarian and breast cancer patient
populations that lack effective treatment options. This publication
highlights the discovery, mechanism of action and promise of SY-1365 as
a new targeted approach for a range of difficult-to-treat cancers.

“SY-1365 represents a potentially transformative targeted approach for a
number of cancers that have eluded treatment with existing approaches,”
said Eric R. Olson, Ph.D., Syros’ Chief Scientific Officer. “While CDK7
has long been a target of interest, it was historically
difficult-to-drug. This new publication profiles our work in discovering
SY-1365, which we believe to be the most advanced selective CDK7
inhibitor in clinical development, and the substantial anti-tumor
activity seen in preclinical models that supported its advancement into
the clinic. We are excited by the promise of CDK7 inhibition and the
potential benefit SY-1365 may bring to patients who are in dire need of
better therapies.”

Syros is currently conducting a Phase 1 clinical trial assessing the
safety and efficacy of SY-1365 as a single agent and in combination with
standard-of-care therapies in multiple ovarian and breast cancer patient
populations. The trial includes cohorts evaluating SY-1365 as a single
agent in patients with relapsed ovarian clear cell cancer and in
high-grade serous ovarian cancer (HGSOC) patients who have had three or
more prior lines of therapy; in combination with carboplatin in HGSOC
patients who have had one or more prior lines of therapy; in combination
with fulvestrant in metastatic hormone receptor-positive breast cancer
patients who are resistant to treatment with a CDK4/6 inhibitor; and as
a single agent in patients with solid tumors of any histology accessible
for biopsy. Additional details about the trial can be found using the
identifier NCT03134638 at www.clinicaltrials.gov.

CDK7 plays a key role in the transcription of genes and in cell cycle
regulation, and inhibiting CDK7 disrupts two important processes that
cancer cells use to survive: 1) expression of cancer-promoting genes;
and 2) uncontrolled cell cycle progression. SY-1365 has shown anti-tumor
activity in preclinical models of a range of solid tumors and blood
cancers, including cancers that have become resistant to treatment with
existing therapies or where existing options have failed to provide
meaningful benefit to patients. Further, data suggests that SY-1365
works to inhibit the growth of cell lines representing many different
cancer types at nanomolar concentrations, decreases MCL1 protein levels,
and demonstrates activity among cancer cells with low BCL-XL expression.

Building on its leadership in CDK7 inhibition, Syros is advancing
SY-5609, a highly selective and potent oral CDK7 inhibitor, toward
clinical development. In preclinical studies, SY-5609 has demonstrated
substantial anti-tumor activity, including inducing complete regressions
in cell line-derived xenograft models of breast and ovarian cancers. The
company plans to complete investigational new drug application
(IND)-enabling studies by the end of 2019 to support the initiation of a
Phase 1 oncology trial in early 2020.

About Syros Pharmaceuticals
Syros is pioneering the
understanding of the non-coding regulatory region of the genome to
advance a new wave of medicines that control the expression of genes.
Syros has built a proprietary platform that is designed to
systematically and efficiently analyze this unexploited region of DNA 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 monogenic 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 SY-1365, a selective CDK7 inhibitor in a Phase 1
clinical trial focused on patients with ovarian and breast cancers.
Syros is also developing a deep preclinical and discovery pipeline,
including SY-5609, an oral CDK7 inhibitor, as well as programs in
immuno-oncology and sickle cell disease. 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 promise of selective CDK7 inhibition
and the potential benefit of SY-1365 as a therapeutic approach for
difficult to treat cancers; the ability to complete IND-enabling
preclinical studies and begin clinical development of SY-5609; and the
benefits of Syros’ gene control platform and product development
pipeline. The words ‘‘anticipate,’’ ‘‘believe,’’ ‘‘continue,’’
‘‘could,’’ ‘‘estimate,’’ ‘‘expect,’’ “hope,” ‘‘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-1365, under the timelines it projects in current
and future clinical trials; demonstrate in any current and future
clinical trials the requisite safety, efficacy and combinability of its
drug candidates; successfully progress SY-5609 through IND-enabling
preclinical and toxicology studies; replicate scientific and
non-clinical data in clinical trials; obtain and maintain patent
protection for its drug candidates and the freedom to operate under
third party intellectual property; obtain and maintain necessary
regulatory approvals; identify, enter into and maintain collaboration
agreements with third parties, including its ability to perform under
the collaboration agreement with Incyte; 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 Syros’ Annual Report on Form 10-K for the
year ended December 31, 2018, which is on file with the Securities and
Exchange Commission; and risks described in other filings that Syros
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.

Contacts

Media Contact:
Naomi Aoki
Syros Pharmaceuticals
617-283-4298
[email protected]

Investor Contact:
Hannah Deresiewicz
Stern Investor
Relations, Inc.
212-362-1200
[email protected]