Halozyme Therapeutics Presents Positive Pre-Clinical Single Agent Data for PEGPH20

Significant Single Agent Anti-Tumor Activity Observed With PEGPH20 in Tumor Models That Accumulate Hyaluronan Extended Half-Life of PEGPH20 Allows Continued Depletion of Hyaluronan From Tumors Following Systemic Administration SAN DIEGO, Jan. 26, 2009 (GLOBE NEWSWIRE) -- Halozyme Therapeutics, Inc. (Nasdaq:HALO), a biopharmaceutical company developing and commercializing products targeting the extracellular matrix, today announced the presentation of positive pre-clinical animal efficacy data for PEGPH20 (pegylated-rHuPH20 enzyme) monotherapy at the American Association for Cancer Research (AACR) Advances in Prostate Cancer Research meeting in San Diego. The study demonstrated that repeat intravenous treatment with PEGPH20 as a single agent in the PC3 mouse model resulted in approximately 70% (p=0.001) tumor growth inhibition compared to controls.

"This study demonstrates that a sustained depletion of hyaluronan from the tumor microenvironment with PEGPH20 is associated with a suppression of tumor cell expansion," stated Gregory Frost, Ph.D., Halozyme's Chief Scientific Officer. "By treating the tumor as an organ rather than just individual cancer cells, novel complementary approaches to treating this disease may be possible."

Halozyme continues to prepare for the commencement of a Phase 1 single agent clinical trial during the first half of 2009 with intravenously administered PEGPH20 in treatment refractory cancer patients. Additional investigations are also underway to explore combinations of PEGPH20 with other targeted and cytotoxic agents for potential clinical investigation.

Additional Study Results and Details

Various prostate cancer cell lines were screened in vitro for the production of pericellular coats comprised of hyaluronan (HA), the substrate for the PEGPH20 enzyme. Several aggressive prostate cancer cell lines that produce HA-rich coats surrounding the tumor cells collapsed in the presence of PEGPH20. Moreover, PEGPH20 significantly suppressed the growth of coat producing human prostate cancer cells within a three-dimensional matrix in a dose dependent fashion, suggesting such cells require HA to rapidly expand into the surrounding microenvironment.

Treatment of human PC3 prostate tumors in athymic mice with intravenous PEGPH20 resulted in a rapid, dose-dependent depletion of HA from the tumor microenvironment. Accumulation of HA in tumors such as PC3, correlates with increased tumor growth, metastases and elevated interstitial fluid pressure. Continued enzymatic depletion of HA from PC3 tumors with intravenous PEGPH20 was associated with a 70% tumor growth inhibition and an approximate doubling in time to progression. In contrast, no suppression of tumor volume growth or increase in time to progression was observed with PEGPH20 treatment of an HA negative prostate tumor, Du145.

Pegylation refers to the covalent attachment of polyethylene glycol to a molecule, usually a drug or therapeutic protein. The pegylation of rHuPH20 increases its plasma half-life to greater than 24 hours compared to less than one minute for the unpegylated enzyme, therefore resulting in a longer duration of action.

About Halozyme Therapeutics, Inc.

Halozyme is a biopharmaceutical company developing and commercializing products targeting the extracellular matrix for the endocrinology, oncology, dermatology and drug delivery markets. The company's portfolio of products and product candidates is based on intellectual property covering the family of human enzymes known as hyaluronidases and additional enzymes that affect the extracellular matrix. Halozyme's Enhanze(tm) Technology is a novel drug delivery platform designed to increase the absorption and dispersion of biologics. The company has key partnerships with Roche to apply Enhanze Technology to Roche's biological therapeutic compounds for up to 13 targets and with Baxter BioScience to apply Enhanze Technology to Baxter's biological therapeutic compound, GAMMAGARD LIQUID. Halozyme's research pipeline candidates target significant areas of unmet medical need. For more information visit www.halozyme.com .

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Safe Harbor Statement

In addition to historical information, the statements set forth above include forward-looking statements (including, without limitation, statements concerning future clinical trials and benefits associated with PEGPH20) that involve risk and uncertainties that could cause actual results to differ materially from those in the forward-looking statements. The forward-looking statements are also identified through use of the words "believe," "enable," "may," "will," "could," "intends," "estimate," "anticipate," "plan," "predict," "probable," "potential," "possible," "should," "continue," and other words of similar meaning. Actual results could differ materially from the expectations contained in forward-looking statements as a result of several factors, including regulatory approval requirements and competitive conditions. These and other factors that may result in differences are discussed in greater detail in the company's reports on Forms 10-K, 10-Q, and other filings with the Securities and Exchange Commission.