(EPZM) Reacquires Global Rights from Eisai for First-in-Class EZH2 Inhibitor EPZ-6438

Epizyme, Inc. (NASDAQ:EPZM), a clinical stage biopharmaceutical company creating novel epigenetic therapeutics for cancer patients, announced today that it has reacquired global rights to its EZH2 program, including EPZ-6438, from its partner Eisai Co. Ltd, or Eisai. Under the terms of the agreement, Epizyme will be solely responsible for global clinical development, manufacturing and commercialization in all countries outside of Japan, where Eisai will retain rights. EPZ-6438, a first-in-class inhibitor of EZH2, is currently being evaluated in a Phase 1/2 clinical study for the treatment of B-cell non-Hodgkin lymphoma (NHL) and INI1-deficient solid tumors, such as synovial sarcoma and malignant rhabdoid tumor.

“Over the past seven years, we have been deliberately building Epizyme as an independent, fully integrated oncology company. Obtaining global control of EPZ-6438, a very promising clinical asset, represents an important milestone in the evolution of the Company,” said Robert Gould, Ph.D., President and Chief Executive Officer, Epizyme. “As we began to see the quality and duration of the responses, including two complete responses, in relapsed and refractory NHL and INI1-deficient patients treated with EPZ-6438 as a monotherapy, it became clear to us that having worldwide development and commercialization responsibility for a targeted therapeutic like 6438 would be transformative for Epizyme.”

“With the continued emergence of clinical data on EPZ-6438, it is apparent that this is a therapy with tremendous potential to benefit a variety of patient populations,” said Takashi Owa, Ph.D., Chief Innovation Officer, Eisai Product Creation Systems. “As we re-focus our resources on our later stage programs across therapeutic areas, we believe that Epizyme is well positioned to move EPZ-6438 development forward aggressively. We are pleased that the structure of this agreement allows us to participate in the future success of EPZ-6438.”

Following completion of the transition of EPZ-6438 from Eisai to Epizyme, Epizyme plans to conduct a five-arm Phase 2 study in approximately 150 patients with NHL. This study will evaluate EPZ-6438 in the following patient cohorts:

• Diffuse large B-cell lymphoma, germinal center B-cell-like (GCB) type with wild-type EZH2
• Diffuse large B-cell lymphoma, GCB type with mutant EZH2
• Follicular lymphoma with wild-type EZH2
• Follicular lymphoma with mutant EZH2
• Diffuse large B-cell lymphoma, non-GCB type

The cohort of patients with diffuse large B-cell non-GCB type is expected to include predominantly patients with wild-type EZH2, since the frequency of EZH2 mutations is approximately 5 percent in this sub-population of diffuse large B-cell lymphoma.

In addition, Epizyme plans to initiate a Phase 2 study in adults with INI1-deficient tumors, including synovial sarcoma, and a Phase 1 study in children with INI-1 deficient tumors, including malignant rhabdoid tumors. Epizyme will also continue the clinical pharmacology studies that are part of the Eisai / Epizyme clinical plan.

“We are pleased to lead the development of EPZ-6438, and look forward to further exploring and defining its clinical activity and safety in a range of hematological and solid tumor indications,” said Peter Ho, M.D., Ph.D., Chief Development Officer, Epizyme.

Terms of the Agreement

Under the terms of the agreement, Epizyme will be responsible for global development, manufacturing and commercialization. Epizyme will fund 100 percent of global development costs, and Eisai will fund 100 percent of Japan-specific development costs.

Epizyme will make a $40 million upfront payment to Eisai, with a total of up to $20 million in potential clinical milestone payments and up to $50 million in potential regulatory milestone payments. Epizyme will pay Eisai a royalty at a percentage in the mid-teens on sales of EPZ-6438 outside of Japan, and Eisai will pay Epizyme a royalty at a percentage in the mid-teens on sales in Japan. Eisai will have a limited right of first negotiation for Asia rights if Epizyme decides to license Asia rights to a third party.

Conference Call Information

The Company will discuss details of this transaction and the Company’s development plans for EPZ-6438 on its 2014 financial results conference call, to be held at 7:30 a.m. today, March 12.

To participate in the conference call, please dial 1-877-844-6886 (domestic) or 1-970-315-0315 (international) and refer to conference ID 1428077. The live webcast can be accessed under “Events and Presentations” in the Investor Relations section of the Company’s website at www.epizyme.com.

About EPZ-6438

Epizyme is developing EPZ-6438 for the treatment of non-Hodgkin lymphoma patients and patients with INI1-deficient solid tumors. EPZ-6438 is a small molecule inhibitor of EZH2 developed by Epizyme. In many human cancers, misregulated EZH2 enzyme activity results in misregulation of genes that control cell proliferation—without these control mechanisms, cancer cells are free to grow rapidly.

EPZ-6438 is the second HMTi to enter human clinical development (following Epizyme’s DOT1L inhibitor, EPZ-5676).

Additional information about this program, including clinical trial information, may be found here: http://clinicaltrials.gov/ct2/show/NCT01897571?term=7438&rank=1

About Epizyme, Inc.

Epizyme, Inc. is a clinical stage biopharmaceutical company creating novel epigenetic therapeutics for cancer patients. Epizyme has built a proprietary product platform that the company uses to create small molecule inhibitors of a 96-member class of enzymes known as histone methyltransferases, or HMTs. HMTs are part of the system of gene regulation, referred to as epigenetics, that controls gene expression. Genetic alterations can result in changes to the activity of HMTs, making them oncogenic (cancer-causing). By focusing on the genetic drivers of cancers, Epizyme’s targeted science seeks to match the right medicines with the right patients.

For more information, visit www.epizyme.com and connect with us on Twitter at @EpizymeRx.

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 or expansion of ongoing clinical studies, 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 or the results of future trials, expectations for regulatory approvals, development progress of the Company’s companion diagnostics, availability of funding sufficient for 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 or companion diagnostics and other factors discussed in the “Risk Factors” section of our Form 10-Q filed with the SEC on November 6, 2014, and in our other filings from time to time with the SEC, including our Form 10-K for the year ended December 31, 2014, that will be filed with the SEC. In addition, the forward-looking statements included in this press release represent the Company’s views as of 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. These forward-looking statements should not be relied upon as representing the Company’s views as of any date subsequent to the date hereof.