Halozyme Therapeutics Presents Findings on Combinations of rHuPH20 Enzyme With Bisphosphonates

Data Support Intravenous to Subcutaneous Conversion

SAN DIEGO, April 16 2008 / PSA Risingl/ -- Halozyme Therapeutics, Inc. (Nasdaq: HALO), a biopharmaceutical company developing and commercializing products targeting the extracellular matrix, today announced new pre-clinical findings on the local tolerability and pharmacokinetics of bisphosphonates combined with rHuPH20 at the American Association for Cancer Research (AACR) conference.

The objectives of the presented studies were to investigate in animal models whether increasing the dispersion and absorption of bisphosphonates in the skin and subcutaneous tissues with rHuPH20 could modify injection site reaction (ISR) profiles from two intravenous bisphosphonate formulations, zoledronic acid and ibandronate. The pharmacokinetics of bisphosphonates in blood were also examined and compared to intravenous infusion. Key findings from the study were as follows:

• In rodent intradermal models, injection of bisphosphonates without rHuPH20 created injection site reactions characterized by erythema, induration, and ulceration in a concentration dependent manner.
• In rodent intradermal models, the maximal concentration of bisphosphonates that could be administered without producing ISRs was increased 3- to 5-fold when co-administered in combination with rHuPH20.
• In porcine pharmacokinetic models, absolute bioavailability by subcutaneous (SC) injection with rHuPH20 was comparable to IV infusion.

"Historically, hyaluronidase products have been utilized as an antidote to local extravasations of certain chemotherapy agents," said Gregory Frost, PhD, Halozyme's Vice President and Chief Scientific Officer. "We reasoned that if rHuPH20 hyaluronidase could rapidly disperse, dilute and systemically absorb bisphosphonates, it could prevent local irritation and facilitate conversion from intravenous infusion to a more convenient subcutaneous route of administration. These pre-clinical findings support this program's objective of developing what would be the only SC bisphosphonate on the market, in the event of continued success." The Company plans to bring its SC bisphosphonate program into the clinic in the third quarter of this year.

Bisphosphonates are a class of molecules that bind to mineralized bone matrix and inhibit bone resorption. Currently, there are oral and intravenous bisphosphonates. Oral Bisphosphonates often cause gastrointestinal side effects and require a cumbersome dosing regimen. The gastrointestinal side effects of oral bisphosphonates is a significant cause of patient non-compliance to prescribed therapy. Certain bisphosphonates are indicated for the treatment of osteoporosis and skeletal metastases, but can only be administered today by intravenous infusion. As such, patients often have to travel to an infusion center or see a specialist to receive their intravenous bisphosphonate infusion. Subcutaneous injections of bisphosphonates are not considered feasible due to injection site toxicity in the skin and/or impractical injection volumes.

The recombinant protein, rHuPH20, is a human hyaluronidase enzyme that increases the dispersion and systemic absorption of locally injected drugs by temporarily degrading hyaluronan under the skin.

About Halozyme Therapeutics, Inc.

Halozyme is a biopharmaceutical company developing and commercializing products targeting the extracellular matrix for the drug delivery, oncology and dermatology markets. The company's portfolio of products and product candidates is based on intellectual property covering the family of human enzymes known as hyaluronidases. The company's Enhanze(TM) Technology is a novel drug delivery platform designed to increase the absorption and dispersion of biologics. Its key partnerships are with Roche to apply Enhanze Technology to Roche's biological therapeutic compounds for up to 13 targets and with Baxter to apply Enhanze Technology to Baxter's biological therapeutic compound, GAMMAGARD LIQUID 10%. In addition, the company has received FDA approval for two products: Cumulase(R), for use in in-vitro fertilization, and HYLENEX, for use as an adjuvant to increase the absorption and dispersion of other injected drugs and fluids. HYLENEX is partnered with Baxter International Inc. The Company also has a number of different enzymes in its portfolio that are targeting significant areas of unmet need.

Safe Harbor Statement

In addition to historical information, the statements set forth above include forward-looking statements (including, without limitation, statements concerning (i) the pre-clinical results of the company's rHuPH20 enzyme with bisphosphonates (ii) and the timing of entering the clinic for the company's subcutaneous bisphosphonate program) 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.

Halozyme Contact Media Contacts David A. Ramsay Karen Sparks / Joleen Schultz Chief Financial Officer Mentus (858) 704-8260 (858) 455-5500, x275/x215

[email protected] [email protected] [email protected]

SOURCE Halozyme Therapeutics, Inc.

David A. Ramsay, Chief Financial Officer of Halozyme Therapeutics, Inc., +1-858-704-8260, [email protected]; or Karen Sparks, +1-858-455-5500, ext. 275, [email protected], or Joleen Schultz, +1-858-455-5500, ext. 215 [email protected], both of Mentus, for Halozyme Therapeutics, Inc.