Eisai and Halozyme Sign Collaboration Agreement to Investigate Eribulin and PEGPH20 in Advanced Breast Cancer

PRESS RELEASE

TOKYO and San Diego, CA — July 31, 2015 – Eisai Co., Ltd. and Halozyme Therapeutics, Inc. (NASDAQ: HALO) announced today that they have signed a clinical collaboration agreement to evaluate Eisai’s anticancer agent eribulin mesylate (brand name: Halaven®, “eribulin”) in combination with Halozyme’s investigational new drug PEGPH20 (PEGylated recombinant human hyaluronidase) in first line HER2- negative advanced breast cancer.

Eribulin, a halichondrin class microtubule dynamics inhibitor with a novel mechanism of action, is currently approved for the treatment of advanced breast cancer in approximately 60 countries worldwide. Structurally, eribulin is a simplified and synthetically produced version of halichondrin B, a natural product isolated from the marine sponge Halichondria okadai. Eribulin is believed to work by inhibition of the growth phase of microtubule dynamics which prevents cell division.

PEGPH20 is an investigational drug administered intravenously that targets the degradation of hyaluronan, a glycosaminoglycan — or chain of natural sugars throughout the body. Hyaluronan accumulates around cancer cells, increasing tumor interstitial fluid pressure and constricting tumor vasculature, subsequently inhibiting anticancer agents from reaching cancer cells. By degrading hyaluronan, PEGPH20 increases blood flow to the tumor which may allow cancer therapies to be more efficiently delivered to their target.

Under the agreement, the companies will jointly conduct and share the costs of a Phase Ib/II clinical study seeking to determine whether or not the combination therapy of eribulin and PEGPH20 can improve the overall response rate in advanced breast cancer patients with high levels of hyaluronan. In hyaluronan-rich triple-negative breast preclinical animal models, the addition of PEGPH20 to eribulin showed a significantly higher tumor growth inhibition including tumor regression when compared to eribulin alone.

“This is a very important collaboration, one that speaks to our continued commitment to address the unmet medical needs of patients with advanced breast cancer,” said RuiRong Yuan, MD, Vice President and Chief Medical Officer, Eisai Global Oncology. “We look forward to enrolling patients in the clinical trial and assessing the results.”

“This agreement marks the first clinical collaboration agreement for Halozyme and extends the study of PEGPH20 to a substantially wider population of patients with a partner that is a clear leader in the treatment of advanced breast cancer,” said Dr. Helen Torley, President and CEO, Halozyme Therapeutics, Inc.