Epizyme Provides Business Update and Reports First Quarter 2019 Financial Results

Tazemetostat NDA Submissions for Epithelioid Sarcoma and Follicular
Lymphoma on Track for Second Quarter and Fourth Quarter 2019,
Respectively

Updated Data from Tazemetostat Development Program to be Presented in
the Second Quarter

First Research Milestone Achieved in Worldwide Collaboration with
Boehringer Ingelheim to Develop Novel Epigenetic Oncology Therapies

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Epizyme, Inc. (Nasdaq: EPZM), a late-stage biopharmaceutical company
developing novel epigenetic therapies, today provided business and
pipeline updates and reported first quarter 2019 financial results.

“This is an incredibly exciting time for our company, and 2019 is slated
to be one of the most important years in Epizyme’s evolution,” said
Robert Bazemore, president and chief executive officer of Epizyme. “Our
team is on track to submit two NDAs for tazemetostat this year, first
for epithelioid sarcoma in the second quarter, which, if successful,
would make tazemetostat the first commercially available EZH2 inhibitor,
and then a second submission for follicular lymphoma in the fourth
quarter. We are preparing for multiple clinical trials starting mid-year
designed to expand the utility of tazemetostat, and to initiate clinical
development of our novel G9a inhibitor in the second half of 2019. In
addition, we have achieved the first milestone in our partnership with
Boehringer Ingelheim, which further validates our research expertise and
our collaboration strategy in epigenetic target discovery and drug
development. With each milestone accomplished, we are one step closer to
fulfilling our mission of bringing new treatments to patients with
cancer and other serious diseases.”

Tazemetostat Program Updates and Progress

• NDA Submission for Epithelioid Sarcoma (ES) on Track for Second
  Quarter: Epizyme is well underway with its preparations to submit
  its first New Drug Application (NDA) for accelerated approval to the
  U.S. Food and Drug Administration (FDA) in the second quarter of 2019
  for tazemetostat in patients with ES. This is an ultra-rare and
  difficult-to-treat sarcoma, and if approved, tazemetostat would be the
  first treatment specifically indicated for patients with ES. Updated
  data from the company’s ongoing Phase 2 trial in ES will be presented
  at the 2019 American Society of Clinical Oncology (ASCO) Annual
  Meeting in Chicago; details will be disclosed at a future date.
• NDA Submission for All-Comer Follicular Lymphoma (FL) Population
  Planned for Fourth Quarter: Epizyme plans to submit an NDA for
  accelerated approval of tazemetostat for patients with FL, regardless
  of their EZH2 mutational status, who have been previously treated with
  two or more systemic therapies. The ongoing Phase 2 study has
  completed enrollment, and the company is working toward the submission
  of an NDA for accelerated approval in the fourth quarter of 2019 for
  this patient population. Updated data from the Phase 2 trial will be
  presented at a medical meeting in the second quarter of 2019. Details
  will be disclosed at a future date.

Planned Tazemetostat Clinical Studies in 2019

Epizyme is planning for multiple clinical trials designed to expand the
benefit of tazemetostat into earlier treatment lines in follicular
lymphoma, and to explore new combinations and potential indications in
both FL and solid tumors. Planned clinical trials include:

• a combination study of tazemetostat with the chemo-free treatment
  regimen “R²” (Revlimid^® plus Rituxan^®)
  for patients with relapsed/refractory FL who have received at least
  one prior therapy;
• a combination study of tazemetostat with Rituxan for patients with
  relapsed/refractory FL;
• a combination study of tazemetostat with R-CHOP for front-line
  patients with FL in collaboration with the Lymphoma Study Association
  (LYSA);
• a combination study of tazemetostat with the standards-of-care for
  patients with castration-resistant prostate cancer; and
• a combination study of tazemetostat with a PARP inhibitor for patients
  with platinum-resistant solid tumors, such as small-cell lung cancer,
  triple-negative breast cancer and ovarian cancer.

Initiation of Clinical Development of EZM8266 for Sickle Cell Disease

• Upon approval of an Investigational New Application (IND) for EZM8266
  for the treatment of patients with sickle cell disease, Epizyme
  anticipates beginning clinical development in the second half of 2019
  with a Phase 1 trial of EZM8266, a novel, first-in-class G9a inhibitor.

Business Updates

• Epizyme recently earned a $5.5 million milestone payment from
  Boehringer Ingelheim, following the selection of a lead optimization
  candidate for the shared program targeting an enzyme within the
  helicase family. The companies are jointly researching and developing
  this program, with both parties sharing U.S. commercialization
  responsibilities and Boehringer Ingelheim assuming responsibility for
  commercialization outside the U.S. The companies will also share
  research responsibilities for a histone acetyltransferase (HAT)
  program that is under development.
• In March of this year, Epizyme raised $172.50 million in aggregate
  gross proceeds, before deducting underwriting discounts and offering
  expenses, from two concurrent underwritten public offerings.

First Quarter 2019 Financial Results

• Cash Position: Cash, cash equivalents and marketable securities
  were $371.1 million as of March 31, 2019, as compared to $247.9
  million as of March 31, 2018.
• Revenue: Collaboration revenue for the first quarter of
  2019 was $7.9 million. There was no collaboration revenue recognized
  for the first quarter of 2018. The increase in collaboration revenue
  is due to the company’s collaboration with Boehringer Ingelheim, which
  was initiated in November 2018.
• R&D Expenses: Research and development (R&D) expenses
  were $26.9 million for the first quarter of 2019, compared to $25.6
  million for the first quarter of 2018. The increase is primarily due
  to greater tazemetostat manufacturing costs and costs incurred in
  preparation for two NDA submissions offset by decreases in clinical
  trial expenses.
• G&A Expenses: General and administrative (G&A) expenses
  were $12.0 million for the first quarter of 2019, compared to $9.4
  million for the first quarter of 2018. The increase is primarily due
  to a rise in medical affairs and commercial costs as a result of
  organizational development in preparation for tazemetostat
  commercialization.
• Net Loss Attributed to Common Stockholders: Net loss
  attributable to common stockholders was $32.3 million, or $0.39 per
  share, for the first quarter of 2019, compared to $34.1 million,
  or $0.49 per share, for the first quarter of 2018.

Financial Guidance

Following its March financing, and based on its current operating plan,
Epizyme expects its cash runway to extend into at least the first
quarter of 2021.

The company will not hold a conference call in conjunction with these
results.

About the Epizyme-Boehringer Ingelheim Collaboration

Epizyme and Boehringer Ingelheim established a worldwide collaboration
agreement in November 2018 to develop novel epigenetic oncology
therapies. Under the terms of the agreement, Boehringer Ingelheim and
Epizyme will jointly research and develop a helicase program, with both
parties sharing U.S. commercialization responsibilities and Boehringer
Ingelheim assuming responsibility for commercialization outside the U.S.
Epizyme and Boehringer Ingelheim will also share research
responsibilities for a histone acetyltransferase (HAT) program, with
Boehringer Ingelheim assuming responsibility for worldwide development
and commercialization. Epizyme received an upfront payment of $15
million and will receive an additional $5 million in research funding in
2019, and is eligible to receive up to $280.5 million in research,
development and commercialization milestones. For the helicase program,
Epizyme will fund a portion of the global development costs, retain a
share of U.S. profits and receive tiered royalties on ex-U.S. sales. For
the HAT program, Epizyme is eligible to receive tiered royalties on
worldwide sales.

About Epizyme, Inc.

Epizyme, Inc. is a late-stage biopharmaceutical company committed to
rewriting treatment for cancer and other serious diseases through novel
epigenetic medicines. Epizyme is broadly developing its lead product
candidate, tazemetostat, a first-in-class EZH2 inhibitor, with studies
underway in both solid tumors and hematological malignancies, as a
monotherapy and combination therapy in relapsed and front-line disease.
The company also is developing a novel G9a program with its next
development candidate, EZM8266, which is targeting sickle cell disease.
By focusing on the genetic drivers of disease, Epizyme’s science seeks
to match targeted medicines with the patients who need them. For more
information, visit www.epizyme.com.

Cautionary Note on Forward-Looking Statements

Any statements in this press release about future expectations, plans
and prospects for Epizyme, Inc. and other statements containing the
words “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,”
“plan,” “predict,” “project,” “target,” “potential,” “will,” “would,”
“could,” “should,” “continue,” and similar expressions, constitute
forward-looking statements within the meaning of The Private Securities
Litigation Reform Act of 1995. Actual results may differ materially from
those indicated by such forward-looking statements as a result of
various important factors, including: uncertainties inherent in the
initiation of future clinical studies and in the availability and timing
of data from ongoing clinical studies; whether interim results from a
clinical trial will be predictive of the final results of the trial;
whether results from preclinical studies or earlier clinical studies
will be predictive of the results of future trials; whether results from
clinical studies will warrant meetings with regulatory authorities,
submissions for regulatory approval or review by governmental
authorities under the accelerated approval process; whether Fast Track
Designation and Orphan Drug Designations will provide the benefits for
which tazemetostat is eligible; expectations for regulatory approvals,
including accelerated approval, to conduct trials or to market products;
whether the company’s cash resources will be sufficient to fund the
company’s foreseeable and unforeseeable operating expenses and capital
expenditure requirements; other matters that could affect the
availability or commercial potential of the company’s therapeutic
candidates; and other factors discussed in the “Risk Factors” section of
the company’s most recent Form 10-Q filed with the SEC and in the
company’s other filings from time to time with the SEC. In addition, the
forward-looking statements included in this press release represent the
company’s views as of the date hereof and should not be relied upon as
representing the company’s views as of any date subsequent to the date
hereof. The company anticipates that subsequent events and developments
will cause the company’s views to change. However, while the company may
elect to update these forward-looking statements at some point in the
future, the company specifically disclaims any obligation to do so.

Contacts

Media:
Erin Graves, (617) 500-0615
Epizyme, Inc.
[email protected]

Investors:
Chelcie
Lister, (919) 777-3049
THRUST Strategic Communications
[email protected]