Epizyme Reports Positive Data on Tazemetostat in Epithelioid Sarcoma from its Phase 2 Trial Cohort at ESMO

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Oct. 22, 2018– Epizyme, Inc. (Nasdaq: EPZM), a clinical-stage company developing novel epigenetic therapies, today announced positive interim data from the fully enrolled epithelioid sarcoma cohort of its ongoing Phase 2 study of its lead candidate tazemetostat, a potent, selective, orally available EZH2 inhibitor. The data were presented by the study’s lead investigator, Mrinal Gounder, M.D., attending physician, Sarcoma Medical Oncology and Early Drug Development Services, Memorial Sloan Kettering Cancer Center, during the European Society for Medical Oncology (ESMO) 2018 Congress in Munich, Germany.

Interim data as of August 21, 2018 from the 62 patients enrolled show that tazemetostat treatment demonstrated clinically meaningful activity for patients with epithelioid sarcoma (ES). Oral, twice daily administration of tazemetostat resulted in durable objective responses and encouraging overall survival in both treatment-naive patients and patients who had been previously treated with an anticancer therapy. In addition, tazemetostat was generally well-tolerated.

“Epithelioid sarcoma is a rare and aggressive form of soft tissue sarcoma, with limited effective treatment options available. We often see patients diagnosed with advanced disease who have a very poor prognosis,” said Dr. Gounder. “It is highly encouraging to see these updated efficacy and tolerability data with tazemetostat, and I believe this agent has the potential to be an important treatment option for patients with epithelioid sarcoma and their treating physicians.”

“We are very pleased with the interim data from this cohort, which represents the largest prospective study of epithelioid sarcoma with any approved or investigational anticancer treatment to date. The data presented today further demonstrate the potential treatment opportunity we see with tazemetostat,” said Rob Bazemore, president and chief executive officer of Epizyme. “We are one step closer to achieving our mission of bringing epigenetic treatments to people with cancer and other serious diseases. We look forward to working with investigators and regulators in an effort to bring to market the potential first therapy indicated for patients with epithelioid sarcoma.”

Epithelioid Sarcoma Interim Efficacy Data

Epithelioid sarcoma is an ultra-rare and aggressive soft tissue sarcoma, characterized by a loss of the INI1 protein. It is most commonly diagnosed in young adults (18-40 years old) and is often fatal, with a median survival of less than one year in treatment-naive patients. Today, there is no treatment indicated specifically for epithelioid sarcoma.

The ES cohort completed enrollment in July of 2017 with 24 treatment-naive patients and 38 relapsed and/or refractory patients for a total of 62 epithelioid sarcoma patients. The primary endpoint of the study is objective response rate (ORR), comprised of complete and partial responses as measured by RECIST 1.1. Key secondary endpoints include duration of response, overall survival, disease control rate (DCR; comprised of confirmed objective responses for any duration or disease stabilization of 32 weeks or more) and safety.

Interim findings are summarized below, based on an August 21, 2018 data cut-off date.

Key Efficacy Endpoint

Treatment-naive
(n=24)

Relapsed and/or
Refractory
(n=38)

Total
(n=62)

Median Overall Survival, weeks
(90% confidence interval)

47.4
(33.7, 64.1)

82.4
(47.7, not reached)

Disease Control Rate, n (%)
(90% confidence interval)

9 (38%)
(21.2, 56.3)

6 (16%)
(7.1, 28.8)

15 (24%)
(15.5, 34.8)

Notably, since the data cut-off, one patient in the treatment-naive group who had stable disease subsequently achieved an objective response. This additional patient brings the total to six responders (~25%) in this treatment-naive group and nine responders (15%) in the overall population, to date, with several patients with stable disease remaining on treatment.

Tazemetostat Interim Safety Data

Tazemetostat has been generally well-tolerated and continues to demonstrate favorable safety in the Phase 2 study, with no discontinuations or deaths due to treatment-related adverse events (AEs) observed. The majority of treatment-emergent adverse events (TEAEs) were grade 1 or 2. Only 13 percent of patients experienced a grade 3 or higher treatment-related AE. Treatment-related AEs with an incidence of 10 percent or greater were fatigue (26%), nausea (26%), decreased appetite (16%), vomiting (16%), diarrhea and weight decrease (13%) and anemia (10%).

“We are pleased with the clinically meaningful and durable objective responses observed in this study, with a number of stable disease patients who are still on treatment and have the potential to achieve an objective response in the future,” stated Dr. Shefali Agarwal, medical oncologist and chief medical officer of Epizyme. “These updated efficacy and safety data from the completed ES cohort suggest that tazemetostat may play an important role for patients in the future, particularly when considering the known limitations and challenges with current treatment options, and further bolster our confidence in our first planned NDA submission for tazemetostat. I’d like to thank the study investigators, medical staffs, and most importantly, the patients and caregivers, who have participated in this trial and supported the ongoing development of tazemetostat.”

About the Tazemetostat Clinical Trial Program

Tazemetostat, a potent, selective, orally available, first-in-class EZH2 inhibitor, is currently being studied as a monotherapy in ongoing Phase 2 programs in certain molecularly defined solid tumors, including epithelioid sarcoma and other INI1-negative tumors; follicular lymphoma (FL); and combination studies in diffuse large B-cell lymphoma (DLBCL) and non–small cell lung cancer (NSCLC).

About Epizyme, Inc.

Epizyme, Inc. is a clinical-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, and 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, 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 relating to the Company’s ability to resume enrollment in its tazemetostat trials and the timing of such resumption, and the impact of the safety finding in the company’s pediatric trial on enrollment of patients in ongoing and future trials of tazemetostat following the lifting of the partial clinical hold and the resumption of enrollment; 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 to conduct trials or to market products; whether the company’s cash resources will be sufficient to fund the company’s foreseeable and unforeseeable future 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.

Source: Epizyme, Inc.

Posted: October 2018

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