AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 10, 2005
REGISTRATION NO. 333-_______

SECURITIES AND EXCHANGE COMMISSION

FORM S-3

REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

HALOZYME THERAPEUTICS, INC.

11588 Sorrento Valley Road, Suite 17
San Diego, California 92121
(858) 794-8889
(Address, Including Zip Code, and Telephone Number, Including
Area Code, of Registrant’s Principal Executive Offices)

David A. Ramsay
Halozyme Therapeutics, Inc.
11588 Sorrento Valley Road, Suite 17
San Diego, California 92121
(858) 794-8889
(Name, Address, Including Zip Code, and Telephone Number, Including
Area Code, of Agent for Service)

COPIES TO:

Douglas J. Rein, Esq.
DLA Piper Rudnick Gray Cary US LLP
4365 Executive Drive, Suite 1100
San Diego, CA 92121-2133
Telephone: (858) 677-1400
Facsimile: (858) 677-1477

APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
From time to time after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. o

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following
box. þ

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box. o

CALCULATION OF REGISTRATION FEE

     (1) This Registration Statement also covers contracts which may be issued by the Registrant under which the counterparty may be required to purchase Debt Securities, Common Stock, Preferred Stock or Warrants.

     (2) Not specified as to each class of securities to be registered hereunder pursuant to General Instruction II.D. of Form S-3. In no event will the aggregate maximum offering price of all securities registered under this Registration Statement exceed $50,000,000. Any securities registered hereunder may be sold separately or as units with other securities registered hereunder.

     (3) Subject to footnote (2), there are being registered hereunder an indeterminate number of Debt Securities as may be sold from time to time by Halozyme Therapeutics, Inc.

     (4) Subject to footnote (2), there are being registered hereunder an indeterminate number of shares of Common Stock as may be sold, from time to time, by Halozyme Therapeutics, Inc. There is also being registered hereunder an indeterminate number of shares of Common Stock that may be issued upon conversion, as applicable, of Preferred Stock or Debt Securities registered hereunder or upon exercise of Warrants registered hereunder, as the case may be.

     (5) Subject to footnote (2), there are being registered hereunder an indeterminate number of shares of Preferred Stock, as may be sold, from time to time, by Halozyme Therapeutics, Inc. or as may be issued upon conversion of Debt Securities registered hereunder or upon the exercise of Warrants registered hereunder, as the case may be.

     (6) Subject to footnote (2), there are being registered hereunder an indeterminate number of Warrants representing rights to purchase Debt Securities, Preferred Stock or Common Stock (as shall be designated by the Company at the time of any such offering) registered hereunder.

     (7) Units may consist of two or more of the securities listed in this table offered and sold together.

     (8) Calculated pursuant to Rule 457(o) of the rules and regulations under the Securities Act of 1933, as amended.

THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a), MAY DETERMINE.

SUBJECT TO COMPLETION, DATED JUNE 10, 2005

The information in this prospectus is not complete and may be changed. We may not sell these securities under this prospectus until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell nor does it seek an offer to buy these securities in any state where the offer and sale would not be permitted.

PROSPECTUS

$50,000,000

HALOZYME THERAPEUTICS, INC.

     We may from time to time issue, in one or more series or classes, up to $50,000,000 in aggregate principal amount of our common stock, preferred stock, debt securities and/or warrants. We may offer these securities separately or together. We will specify in the accompanying prospectus supplement the terms of the securities being offered. We may not sell any securities under this prospectus without delivery of the applicable prospectus supplement.

     We will provide the specific terms of these securities in supplements to this prospectus. Any prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and any accompanying prospectus supplement carefully before you invest. THIS PROSPECTUS MAY NOT BE USED TO OFFER OR SELL ANY SECURITIES UNLESS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

     Our common stock is listed on The American Stock Exchange under the symbol “HTI.” On June 8, 2005, the last reported sale price for our common stock was $2.00 per share.

     The securities offered by this prospectus or any prospectus supplement may be offered directly to investors or to or through underwriters, dealers or other agents. If any underwriters or dealers are involved in the sale of any securities offered by this prospectus and any prospectus supplement, their names, and any applicable purchase price, fee, commission or discount arrangement between or among them, will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement.

     INVESTING IN OUR SECURITIES INVOLVES A HIGH DEGREE OF RISK. SEE “RISK FACTORS” BEGINNING ON PAGE 3 FOR A DISCUSSION OF MATERIAL RISKS YOU SHOULD CONSIDER BEFORE YOU INVEST IN OUR SECURITIES.

     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

THE DATE OF THIS PROSPECTUS IS ____________, 2005.

You should rely only on the information provided or incorporated by reference in this prospectus. We have not authorized anyone to provide you with additional or different information. This document may only be used where it is legal to sell these securities. You should not assume that any information in this prospectus is accurate as of any date other than the date of this prospectus. Information incorporated by reference in this prospectus is accurate only as of the date of the document incorporated by reference. In this prospectus, unless otherwise indicated, the words “Halozyme,” “we,” “us,” and “our” refer to Halozyme Therapeutics, Inc. and its subsidiaries.

TABLE OF CONTENTS

FORWARD-LOOKING STATEMENTS

     This prospectus, including the documents that we incorporate by reference, contains forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act. Any statements about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and may be forward-looking. These statements are often, but are not always, made through the use of words or phrases such as “anticipates,” “estimates,” “plans,” “projects,” “continuing,” “ongoing,” “expects,” “management believes,” “we believe,” “we intend” and similar words or phrases. Accordingly, these statements involve estimates, assumptions and uncertainties which could cause actual results to differ materially from those expressed in them. Any forward-looking statements are qualified in their entirety by reference to the factors discussed throughout this prospectus, and in particular those factors listed under the section entitled “Risk Factors.”

     Because the factors referred to in the preceding paragraph could cause actual results or outcomes to differ materially from those expressed in any forward-looking statements we make, you should not place undue reliance on any such forward-looking statements. Further, any forward-looking statement speaks only as of the date on which it is made, and we undertake no obligation to update any forward-looking statement or statements to reflect events or circumstances after the date on which such statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for us to predict which factors will arise. In addition, we cannot assess the impact of each factor on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements.

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PROSPECTUS SUMMARY

     The following summary highlights selected information from this prospectus and in information incorporated by reference. Because this is a summary, it does not contain all the information about us that may be important to you. You should read this entire prospectus and the other documents and the financial statements and related notes which are incorporated by reference in this prospectus.

Our Business

     Halozyme is a development stage biopharmaceutical company dedicated to the development and commercialization of recombinant human enzymes for the infertility, ophthalmology, and oncology markets.

     Our products under development are based on intellectual property covering the family of human enzymes known as hyaluronidases. Hyaluronidases are enzymes (proteins) that break down hyaluronic acid, which is a naturally occurring substance in the human body. Currently, we have no product revenue and all of our potential products, with the exception of Cumulase™, are either in the discovery, pre-clinical, or pre-NDA approval stage. It may be years, if ever, before we are able to obtain the necessary regulatory approvals necessary to generate meaningful revenue from the sale of these potential products. In addition, we have never generated any revenue from our biopharmaceutical operations and we have had operating and net losses each year since inception. We have accumulated a deficit of $16,264,958 from inception through March 31, 2005.

     Our technology is based on recombinant human PH20 (rHuPH20), a human synthetic version of hyaluronidase that degrades hyaluronic acid, a space-filling, “gel”-like substance that is a major component of tissues throughout the body, such as the skin and eyes. The PH20 enzyme is a naturally occurring enzyme that digests hyaluronic acid to temporarily break down the gel, thereby facilitating the penetration and dispersion of other drugs that are injected in the skin or in the muscle.

     Bovine and ovine derived hyaluronidases have been used in multiple therapeutic areas, including in vitro fertilization and ophthalmology, where a FDA-approved bovine version was used as a drug delivery agent to enhance dispersion of local anesthesia for cataract surgery for over 50 years. Despite the multiple potential therapeutic applications for hyaluronidase, there are problems with existing and potential animal derived product offerings, including:

     • Impurity: Most such commercial enzyme preparations are crude extracts from cattle testes and are typically less than 1-5% pure.

     • Prion disease: Cattle testes are an organ with the highest concentration of hyaluronidase, but also with the highest levels of a protein implicated in the development of neurodegenerative disorders associated with prion disease, such as “Mad Cow Disease.”

     • Immunogenicity: Hyaluronidases can also be found in bacteria, leeches, certain venoms, and marine organisms. Very few companies are pursuing clinical development of any of these enzymes. Regardless, all such preparations are non-human, and are therefore likely to elicit potent immune reactions, possess endotoxin, or have some of the same defects as slaughterhouse derivations.

     There have been successes in replacing animal-derived drugs with human recombinant biologics, as in the case of insulin, Pulmozyme^® and human growth hormone. Our objective is to execute this recombinant human enzyme replacement strategy by applying our products under development to key markets in multiple therapeutic areas, beginning with in vitro fertilization and ophthalmology.

     As an alternative to the existing animal-derived drugs, our proprietary technology, as evidenced by our exclusive license with the University of Connecticut of the patent covering the DNA sequence which encodes human hyaluronidase, may be utilized to expand existing markets and create new markets. Gaps in existing hyaluronidase offerings may create demand for our solution.

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     Deliatroph Pharmaceuticals, Inc., our predecessor company, was founded on February 26, 1998. Our operations to date have been limited to organizing and staffing, acquiring, developing and securing technology and undertaking product development for a limited number of product candidates. As we have not begun principal operations of commercializing a product candidate, our financial statements have historically been presented as a development stage company.

     Our principal executive offices are located at 11588 Sorrento Valley Road, Suite 17, San Diego, California 92121. Our telephone number is (858) 794-8889.

This Prospectus

     This prospectus is part of a registration statement that we filed with the SEC utilizing a “shelf” registration process. Under this shelf process, we may sell the securities described in this prospectus in one or more offerings up to a total dollar amount of $50 million. We have provided in this prospectus a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. We may also add, update or change in the prospectus supplement any of the information contained in this prospectus. This prospectus, together with applicable prospectus supplements, includes all material information relating to this offering. You should read both this prospectus and any prospectus supplement together with the additional information described under the heading “Where You Can Find More Information.”

Risk Factors

     You should consider carefully all of the information contained in and incorporated by reference in this prospectus, including the information set forth under the caption “Risk Factors,” before making an investment in the securities offered.

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RISK FACTORS

     You should carefully consider the following risk factors before purchasing any of our securities. The risks and uncertainties described below are not the only ones we face. There may be additional risks and uncertainties that are not known to us or that we do not consider to be material at this time. If the events described in these risks occur, our business, financial condition and results of operations would likely suffer. This prospectus contains forward-looking statements that involve risks and uncertainties. Our actual results may differ significantly from the results discussed in the forward-looking statements. This section discusses the risk factors that might cause those differences. You should also consider the additional information set forth in our SEC reports on Forms 10-KSB, 10-QSB and 8-K and in the other documents considered a part of this prospectus. See “Where You Can Find More Information.”

Risks Related To Our Business

We have not generated any revenue from product sales to date; we have a history of net losses and negative cash flow, and may never achieve or maintain profitability.

     We have not generated any revenue from product sales to date and may never generate significant revenues from future product sales. Even if we do achieve significant revenues from product sales, we expect to incur significant operating losses over the next several years. We have never been profitable, and may never become profitable. Through March 31, 2005, we have incurred aggregate net losses of $16,264,958.

We may need to raise funds in the next twelve months, and there can be no assurance that such funds will be available.

     During the next twelve months we may need to raise additional capital to complete the steps required to obtain FDA or other regulatory approval for any of our products. If we engage in acquisitions of companies, products, or technology in order to execute our business strategy, we may need to raise additional capital. We may be required to raise additional capital in the future through the public offering of securities, collaborative agreements, private financings and various other equity or debt financings, including calling outstanding warrants to purchase our common stock.

     Currently, warrants to purchase approximately 11.7 million shares of our common stock are outstanding and this amount of outstanding warrants may make us a less desirable candidate for investment for some potential investors. Approximately 5.9 million of our outstanding warrants contain a call feature that, potentially, will allow us to raise funds from the holders of these warrants. If our common stock closes at a price equal to or greater than $2.00 per share for twenty consecutive trading days, we have the ability, at our sole discretion, to call warrants exercisable for up to approximately 1,971,000 shares of common stock, provided that we have not exercised a call right in the preceding three months. Upon such a call, the holders of these warrants have thirty days to decide whether to either exercise their warrants at a price of $1.75 per share or receive $0.01 from us for each share of common stock that is not exercised. If we need to raise funds in the future and we wish to utilize this call right, we will not be able to exercise the call right if we do not meet the minimum closing price condition and, even if we meet this condition, we cannot be sure of the amounts that will be raised by such a call because some or all warrant holders may decide not to exercise their warrants.

     Considering our stage of development and the nature of our capital structure, if we are required to raise additional capital in the future, the additional financing may not be available on favorable terms, or at all. If we are successful in raising additional capital, a substantial number of additional shares will be outstanding and would dilute the ownership interest of our investors.

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If we do not receive and maintain regulatory approvals for our product candidates, we will not be able to commercialize our products, which would substantially impair our ability to generate revenues.

     With the exception of the December 2004 receipt of a CE (European Conformity) Mark and April 2005 FDA clearance for Cumulase, none of our product candidates have received regulatory approval from the FDA or from any similar national regulatory agency or authority in any other country in which we intend to do business. Approval from the FDA is necessary to manufacture and market pharmaceutical products in the United States. Many other countries including major European countries and Japan have similar requirements.

     During March 2005, we filed a new drug application (“NDA”) for the spreading agent Hylenex™, the first product in our Enhanze™ Technology platform. Other manufacturers have FDA approved products for use as spreading agents, including ISTA Pharmaceuticals, Inc. (“ISTA”), with an ovine-derived hyaluronidase (Vitrase®) and Amphastar Pharmaceuticals, Inc., with a bovine (bull) hyaluronidase, Amphadase™. The FDA determined that each of these products were new chemical entities and hence afforded market exclusivity, precluding identical products from being marketed for a period of five years. On March 3, 2005, the FDA confirmed to us that Hylenex would be designated a new chemical entity. Therefore, we believe that it is unlikely that the Vitrase or Amphadase marketing exclusivity will apply to Hylenex; but if the FDA later changes its determination and decides that either or both apply to Hylenex, then such a decision could have a material adverse impact on our operations.

     The processes for obtaining FDA approval are extensive, time-consuming and costly, and there is no guarantee that the FDA will approve our recently filed NDA application for Hylenex or any NDAs that we intend to file with respect to any of our product candidates, or that the timing of any such approval will be appropriate for our product launch schedule and other business priorities, which are subject to change. We have not currently begun the NDA approval process for any of our other potential products, and we may not be successful in obtaining such approvals for any of our potential products.

If we are unsuccessful in our clinical trials, we will not receive regulatory approvals for our product candidates.

     Clinical testing of pharmaceutical products is also a long, expensive and uncertain process. Even if initial results of pre-clinical studies or clinical trial results are positive, we may obtain different results in later stages of drug development, including failure to show desired safety and efficacy.

     The clinical trials of any of our product candidates could be unsuccessful, which would prevent us from obtaining regulatory approval and commercializing the product. FDA approval can be delayed, limited or not granted for many reasons, including, among others:

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     If the FDA does not approve our product candidates in a timely fashion on commercially viable terms or we terminate development of any of our product candidates due to difficulties or delays encountered in the regulatory approval process, it will have a material adverse impact on our business and we will be dependent on the development of our other product candidates and/or our ability to successfully acquire other products and technologies.

     In order to begin clinical testing of our Chemophase product candidate, we need to file an investigational new drug application (“IND”), which the FDA needs to determine is satisfactory to allow the initiation of clinical trials. If the FDA determines that our IND is deficient, we may be required to perform substantial additional work. This could require significant additional expense and delay any initiation of our clinical trials.

     In addition, we intend to market certain of our products, and perhaps have certain of our products manufactured, in foreign countries. The process of obtaining regulatory approvals in foreign countries is subject to delay and failure for many of the same reasons set forth above as well as for reasons that vary from jurisdiction to jurisdiction.

If our product candidates are approved by the FDA but do not gain market acceptance, our business will suffer because we may not be able to fund future operations.

     Assuming that we obtain the necessary regulatory approvals, a number of factors may affect the market acceptance of any of our existing product candidates or any other products we develop or acquire in the future, including, among others:

     If our products do not gain market acceptance, we may not be able to fund future operations, including the development or acquisition of new product candidates and/or our sales and marketing efforts for our approved products, which would cause our business to suffer.

If we are unable to sufficiently develop our sales, marketing and distribution capabilities or enter into agreements with third parties to perform these functions, we will not be able to commercialize products.

     We have never successfully marketed any products, and we may not be successful in marketing and promoting our existing product candidates or any other products we develop or acquire in the future. We are currently in the process of developing our sales, marketing and distribution capabilities. However, our current capabilities in these areas are very limited. In order to commercialize any products successfully, we must internally develop substantial sales, marketing and distribution capabilities, or establish collaborations or other arrangements with third parties to perform these services. We do not have extensive experience in these areas, and we may not be able to establish adequate in-house sales, marketing and distribution capabilities or engage and effectively manage relationships with third parties to perform any or all of such services. To the extent that we enter into co-promotion or other licensing arrangements, our product revenues are likely to be lower

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than if we directly marketed and sold our products, and any revenues we receive will depend upon the efforts of third parties, whose efforts may not be successful.

     In addition, our ability to market and promote our product candidates will be restricted to the labels approved by the FDA. If the approved labels are restrictive, our sales and marketing efforts may be negatively affected.

     We have entered into non-exclusive distribution agreements with MediCult AS, a Denmark-based distributor, MidAtlantic Diagnostics, Inc., a New Jersey-based distributor, and Cook Ob/Gyn Incorporated, an Indiana-based distributor, to market and sell our Cumulase product. We have entered into an exclusive sales and marketing agreement with Baxter Healthcare Corporation to market and sell our Hylenex product candidate, pending FDA approval. We depend upon the efforts of these third parties to promote and sell our Cumulase product and our Hylenex product candidate, pending FDA approval, but there can be no assurance that the efforts of these third parties will result in product sales.

If we have problems with our sole contract manufacturer, our product development and commercialization efforts for our product candidates could be delayed or stopped.

     We have signed a commercial supply agreement with Avid Bioservices Incorporated (“Avid”), a contract manufacturing organization, to produce bulk recombinant human hyaluronidase for clinical use. Avid will produce the active pharmaceutical ingredient under current good manufacturing practices for commercial scale production and will provide support for chemistry, manufacturing and controls sections for FDA regulatory filings. The active pharmaceutical ingredient is used in Hylenex, which will require a pre-approval inspection. If Avid fails this pre-approval inspection, it will likely delay the potential approval of our Hylenex NDA and have a material adverse effect on our business. We have not established and may not be able to establish arrangements with additional manufacturers for these ingredients or products should the existing supplies become unavailable or in the event that our sole contract manufacturer is unable to adequately perform its responsibilities. Difficulties in our relationship with Avid or delays or interruptions in Avid’s supply of its requirements could limit or stop our ability to provide sufficient quantities of our products, on a timely basis, for clinical trials and, if our products are approved, could limit or stop commercial sales, which would have a material adverse effect on our business and financial condition.

If we have problems with the third parties that prepare, package and fill and finish our product candidates for distribution, our product development and commercialization efforts for these candidates could be delayed or stopped.

     In the event that any of our product candidates are used in clinical trials or receive the necessary regulatory approval for commercialization, we rely on third parties to prepare, package and fill and finish the products prior to their distribution. If we are unable to locate third parties to perform these functions on terms that are economically acceptable to us, the progress of clinical trials could be delayed or even suspended and the commercialization of approved product candidates could be delayed or prevented. We currently utilize a third party to fill and finish Cumulase. In addition, we currently utilize Baxter Healthcare Corporation (“Baxter”) to fill and finish Hylenex under a development and supply agreement. Baxter may receive a pre-approval inspection by the FDA. If Baxter fails this pre-approval inspection, the potential approval of our Hylenex NDA, will likely be delayed. This could have a material adverse effect on our business.

Our inability to attract, hire and retain key management and scientific personnel, and to recruit qualified independent directors, could negatively affect our business.

     Our success depends on the performance of key management and scientific employees with biotechnology experience. Given our small staff size and programs currently under development, we depend substantially on our ability to hire, train, retain and motivate high quality personnel, especially our scientists and management team in this field. In addition, we also rely on the expertise and guidance of independent directors to develop business strategies and to guide our execution of these strategies. Due to changes in the regulatory environment for public companies over the past few years, the demand for independent directors

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has increased and it may be difficult for us, due to competition from both like-sized and larger companies, to recruit qualified independent directors.

     Furthermore, if we were to lose key management personnel, particularly Jonathan E. Lim, MD, our chief executive officer, or Gregory I. Frost, PhD, our chief scientific officer, then we would likely lose some portion of our institutional knowledge and technical know-how, potentially causing a substantial delay in one or more of our development programs until adequate replacement personnel could be hired and trained. For example, Dr. Frost has been with us from soon after our inception, and he possesses a substantial amount of knowledge about our development efforts. If we were to lose his services, we would experience delays in meeting our product development schedules. We have not entered into employment agreements with any of our employees or officers, including Dr. Lim and Dr. Frost. We do not have key man life insurance policies on the lives of any of our employees, including Dr. Lim and Dr. Frost.

Future sales of shares of our common stock, including sales of shares issued in our most recent financings, may negatively affect our stock price.

     As a result of our January 2004 private financing transaction, we issued 19,046,721 shares of common stock to certain private investors. In connection with this transaction we also issued warrants to the private investors for the purchase of 10,461,943 shares of common stock at purchase prices ranging from $0.77 to $1.75 per share. Currently, 8.3 million shares of common stock remain issuable upon exercise of these warrants. The exercise of these warrants could result in significant dilution to stockholders at the time of exercise. We filed a registration statement on Form S-3 (Registration No. 333-114776), which was declared effective on April 1, 2005, covering 23,902,482 of the shares issued in the January 2004 private financing transaction and issuable upon exercise of the warrants issued in that transaction.

     As a result of our October 2004 financing transaction, we issued 7,925,715 shares of common stock to certain institutional and accredited investors for $13.9 million in gross proceeds. In connection with this transaction, we also issued warrants for the purchase of 2,609,542 shares of common stock. We filed a registration statement on Form S-3 (Registration No. 333-120448), which was declared effective on November 26, 2004, covering the 10,535,257 shares issued to the private investors and issuable upon exercise of the warrants. In the future, we may issue additional options, warrants or other derivative securities convertible into Halozyme common stock.

     Sales of substantial amounts of shares of our common stock, or even the potential for such sales through the exercise of warrants, could lower the market price of our common stock and impair the Company’s ability to raise capital through the sale of equity securities.

Our stock price is subject to significant volatility.

     Our stock price is subject to significant volatility. Overall market conditions, in addition to other risks and uncertainties described in this section and elsewhere in this report, may cause the market price of our common stock to fall. We participate in a highly dynamic industry, which often results in significant volatility in the market price of common stock irrespective of company performance. As a result, our high and low stock prices during the last twelve months were $4.40 and $1.41, respectively. Fluctuations in the price of our common stock may be exacerbated by conditions in the healthcare and technology industry segments or conditions in the financial markets generally.

Recent trading in our stock has been limited, so investors may not be able to sell as much stock as they want to at prevailing market prices.

     During the last ninety days, our average daily trading volume was approximately 60,000 shares. If limited trading in our stock continues, it may be difficult for stockholders to sell their shares in the public market at any given time at prevailing prices.

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Our decision to redeem outstanding warrants may drive down the market price of our stock.

     As discussed above in the Risk Factor titled “We may need to raise funds in the next twelve months, and there can be no assurance that such funds will be available” we may have the ability to redeem certain outstanding warrants, under certain conditions, that may be exercised for approximately 5.9 million shares of common stock. The redemption price for these warrants is $0.01 per share, but the warrant holders have the opportunity to exercise their warrants prior to redemption at the price of $1.75 per share. If we decide to redeem any portion of our outstanding warrants in the future, some selling security holders may choose to sell outstanding shares of common stock in order to finance the exercise of the warrants prior to their redemption. This pattern of selling may result in a reduction of our common stock’s market price.

Risks Related To Our Industry

Compliance with the extensive government regulations to which we are subject is expensive and time consuming, and may result in the delay or cancellation of product sales, introductions or modifications.

     Extensive industry regulation has had, and will continue to have, a significant impact on our business. All pharmaceutical companies, including Halozyme, are subject to extensive, complex, costly and evolving regulation by the federal government, principally the FDA and to a lesser extent by the U.S. Drug Enforcement Administration (“DEA”), and foreign and state government agencies. The Federal Food, Drug and Cosmetic Act, the Controlled Substances Act and other domestic and foreign statutes and regulations govern or influence the testing, manufacturing, packaging, labeling, storing, record keeping, safety, approval, advertising, promotion, sale and distribution of our products. Under certain of these regulations, Halozyme and its contract suppliers and manufacturers are subject to periodic inspection of its or their respective facilities, procedures and operations and/or the testing of products by the FDA, the DEA and other authorities, which conduct periodic inspections to confirm that Halozyme and its contract suppliers and manufacturers are in compliance with all applicable regulations. The FDA also conducts pre-approval and post-approval reviews and plant inspections to determine whether our systems, or our contract suppliers’ and manufacturers’ processes, are in compliance with current good manufacturing practices and other FDA regulations. If we, or our contract supplier, fail these inspections, we may not be able to commercialize our product in a timely manner without incurring significant additional costs, or at all.

     In addition, the FDA imposes a number of complex regulatory requirements on entities that advertise and promote pharmaceuticals, including, but not limited to, standards and regulations for direct-to-consumer advertising, off-label promotion, industry-sponsored scientific and educational activities, and promotional activities involving the Internet.

     We are dependent on receiving FDA and other governmental approvals prior to manufacturing, marketing and shipping our products. Consequently, there is always a risk that the FDA or other applicable governmental authorities will not approve our products, or will take post-approval action limiting or revoking our ability to sell our products, or that the rate, timing and cost of such approvals will adversely affect our product introduction plans or results of operations.

Our suppliers and sole manufacturer are subject to regulation by the FDA and other agencies, and if they do not meet their commitments, we would have to find substitute suppliers or manufacturers, which could delay the supply of our products to market.

     Regulatory requirements applicable to pharmaceutical products make the substitution of suppliers and manufacturers costly and time consuming. We have no internal manufacturing capabilities and are, and expect to be in the future, entirely dependent on contract manufacturers and suppliers for the manufacture of our products and for their active and other ingredients. The disqualification of these manufacturers and suppliers through their failure to comply with regulatory requirements could negatively impact our business because the delays and costs in obtaining and qualifying alternate suppliers (if such alternative suppliers are available, which we cannot assure) could delay clinical trials or otherwise inhibit our ability to bring approved products to market, which would have a material adverse affect on our business and financial condition.

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We may be required to initiate or defend against legal proceedings related to intellectual property rights, which may result in substantial expense, delay and/or cessation of the development and commercialization of our products.

     We rely on patents to protect our intellectual property rights. The strength of this protection, however, is uncertain. For example, it is not certain that:

     We currently own or license several U.S. patents and also have pending patent applications. There can be no assurance that our existing patents, or any patents issued to us as a result of such applications, will provide a basis for commercially viable products, will provide us with any competitive advantages, or will not face third-party challenges or be the subject of further proceedings limiting their scope or enforceability.

     We may become involved in interference proceedings in the U.S. Patent and Trademark Office to determine the priority of our inventions. In addition, costly litigation could be necessary to protect our patent position. We also rely on trademarks to protect the names of our products. These trademarks may be challenged by others. If we enforce our trademarks against third parties, such enforcement proceedings may be expensive. We also rely on trade secrets, unpatented proprietary know-how and continuing technological innovation that we seek to protect with confidentiality agreements with employees, consultants and others with whom we discuss our business. Disputes may arise concerning the ownership of intellectual property or the applicability or enforceability of these agreements, and we might not be able to resolve these disputes in our favor.

     In addition to protecting our own intellectual property rights, third parties may assert patent, trademark or copyright infringement or other intellectual property claims against us based on what they believe are their own intellectual property rights. While we have not ever been and are currently not involved in any litigation, in the event we become involved, we may be required to pay substantial damages, including but not limited to treble damages, for past infringement if it is ultimately determined that our products infringe a third party’s intellectual property rights. Even if infringement claims against us are without merit, defending a lawsuit takes significant time, may be expensive and may divert management’s attention from other business concerns. Further, we may be stopped from developing, manufacturing or selling our products until we obtain a license from the owner of the relevant technology or other intellectual property rights. If such a license is available at all, it may require us to pay substantial royalties or other fees.

Future acquisitions could disrupt our business and harm our financial condition.

     In order to remain competitive, we may decide to acquire additional businesses, products and technologies. As we have limited experience in evaluating and completing acquisitions, our ability as an organization to make such acquisitions is unproven. Acquisitions could require significant capital infusions and could involve many risks, including, but not limited to, the following:

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     If any of these risks occurred, it could adversely affect our business, financial condition and operating results. We cannot assure you that we will be able to identify or consummate any future acquisitions on acceptable terms, or at all. If we do pursue any acquisitions, it is possible that we may not realize the anticipated benefits from such acquisitions or that the market will not view such acquisitions positively.

If third-party reimbursement is not available, our products may not be accepted in the market.

     Our ability to earn sufficient returns on our products will depend in part on the extent to which reimbursement for our products and related treatments will be available from government health administration authorities, private health insurers, managed care organizations and other healthcare providers.

     Third-party payers are increasingly attempting to limit both the coverage and the level of reimbursement of new drug products to contain costs. Consequently, significant uncertainty exists as to the reimbursement status of newly approved healthcare products. If we succeed in bringing one or more of our product candidates to market, third-party payers may not establish adequate levels of reimbursement for our products, which could limit their market acceptance and result in a material adverse effect on our financial condition.

We face intense competition and rapid technological change that could result in the development of products by others that are superior to the products we are developing.

     We have numerous competitors in the United States and abroad, including, among others, major pharmaceutical and specialized biotechnology firms, universities and other research institutions that may be developing competing products. Such competitors include Sigma-Aldrich Corporation, ISTA Pharmaceuticals, Inc. (ISTA), and Allergan, Inc., among others. These competitors may develop technologies and products that are more effective or less costly than our current or future product candidates or that could render our technologies and product candidates obsolete or noncompetitive. Many of these competitors have substantially more resources and product development, manufacturing and marketing experience and

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capabilities than we do. In addition, many of our competitors have significantly greater experience than we do in undertaking pre-clinical testing and clinical trials of pharmaceutical product candidates and obtaining FDA and other regulatory approvals of products and therapies for use in healthcare. Other manufacturers have FDA approved products for use as spreading agents, including ISTA Pharmaceuticals, Inc. (“ISTA”), with an ovine-derived hyaluronidase (Vitrase®) and Amphastar Pharmaceuticals, Inc., with a bovine (bull) hyaluronidase, Amphadase™. The FDA determined that each of these products were new chemical entities and hence afforded market exclusivity, precluding identical products from being marketed for a period of five years. On March 3, 2005, the FDA confirmed to us that Hylenex would be designated a new chemical entity. Therefore, we believe that it is unlikely that the Vitrase or Amphadase marketing exclusivity will apply to Hylenex; but if the FDA later changes its determination and decides that either or both apply to Hylenex, then such a decision could have a material adverse impact on our operations.

We are exposed to product liability claims, and insurance against these claims may not be available to us on reasonable terms or at all.

     We might incur substantial liability in connection with clinical trials or the sale of our products. Product liability insurance is expensive and in the future may not be available on commercially acceptable terms, or at all. We currently carry a limited amount of product liability insurance. A successful claim or claims brought against us in excess of our insurance coverage could materially harm our business and financial condition.

We may have difficulty implementing in a timely manner the internal controls over financial reporting necessary to allow our management to report on the effectiveness of our internal controls over financial reporting, and we may incur substantial costs in order to comply with the requirements of the Sarbanes-Oxley Act of 2002.

Pursuant to Section 404 of the Sarbanes-Oxley Act of 2002, we will be required to furnish a report of management’s assessment of the effectiveness of our internal controls over financial reporting as part of our Annual Report on Form 10-KSB for the fiscal year ending December 31, 2006. Our registered public accountant will then be required to attest to, and report on, our assessment. In order to issue our report, our management must document both the design for our internal controls over financial reporting and the testing processes that support management’s evaluation and conclusion. There can be no assurance that we will be able to complete the work necessary for our management to issue its management report in a timely manner, or that management will be able to report that our internal controls over financial reporting are effective.

RATIO OF EARNINGS TO FIXED CHARGES

     The following table sets forth ratios of earnings to fixed charges for the periods shown.

     The ratio of earnings to fixed charges was computed by dividing earnings by fixed charges. For this purpose, earnings consist of net loss before fixed charges. Fixed charges consist of interest expense plus the interest factor in lease expenses. During the fiscal years covered by this table, we did not have any material fixed charges or preferred stock dividends. However, our total lease expenses, which comprised most of our total commitments, were $147,638, $123,110, $64,958, $26,292 and zero for the twelve months ended December 31, 2004, 2003, 2002, 2001 and 2000.

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     Earnings have been inadequate to cover fixed charges and total commitments. The dollar amount of the coverage deficiency was approximately $9.1 million, $2.1 million, $1.1 million, $0.6 million and $0.1 million for the twelve months ended December 31, 2004, 2003, 2002, 2001 and 2000.

USE OF PROCEEDS

     We cannot guarantee that we will receive any proceeds in connection with this offering because we may choose not to issue any securities covered by this prospectus.

     Unless otherwise provided in a supplement or amendment to this prospectus, we intend to use any net proceeds from this offering, together with other available funds, for operating costs, capital expenditures and working capital needs and for other general corporate purposes.

     We have not specifically identified the precise amounts we will spend on each of these areas or the timing of these expenditures. The amounts actually expended for each purpose may vary significantly depending upon numerous factors, including the amount and timing of the proceeds from this offering, progress with clinical product development and other research programs. In addition, expenditures may also depend on the establishment of new collaborative arrangements with other companies, the availability of additional financing, and other factors.

     We anticipate that we will be required to raise substantial additional capital to continue to fund the clinical development of our technologies and products. We may raise additional capital through additional public or private financing, as well as collaborative relationships, incurring debt and other available sources.

WHERE YOU CAN FIND MORE INFORMATION

     We file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any document we file at the SEC’s public reference rooms located at Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference rooms. We are also required to file electronic versions of these documents with the SEC, which may be accessed from the SEC’s Internet site at http://www.sec.gov or at our website http://www.halozyme.com.

     The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and information that we file with the SEC later will automatically update and supersede the information in this prospectus or incorporated by reference. The following documents filed by us and any future filings made by us with the SEC under Sections 13(a), 13(c) 14 or 15(d) of the Securities Exchange Act of 1934, until we sell all of the securities offered hereby, are incorporated by reference in this prospectus:

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     We will furnish without charge to you, on written or oral request, a copy of any or all of the documents incorporated by reference. You should direct any requests for documents to David Ramsay, Chief Financial Officer, 11588 Sorrento Valley Road, Suite 17, San Diego, California 92121, telephone: (858) 794-8889.

THE SECURITIES WE MAY OFFER

     The descriptions of the securities contained in this prospectus, together with the applicable prospectus supplements, summarize all the material terms and provisions of the various types of securities that we may offer. We will describe in the applicable prospectus supplement the particular terms of the securities offered by that prospectus supplement. If we indicate in the applicable prospectus supplement, the terms of the securities may differ from the terms we have summarized below. We will also include in the prospectus supplement information, where applicable, about material U.S. federal income tax considerations relating to the securities, and the securities exchange, if any, on which the securities will be listed.

DESCRIPTION OF COMMON STOCK

     The following is only a summary of the material terms of our common stock and, because it is only a summary, it does not contain all the information that may be important to you. Accordingly, you should read carefully the more detailed provisions of our articles of incorporation and bylaws, each of which has been filed with the SEC, as well as applicable Nevada law.

General

     We currently have authorized 100,000,000 shares of common stock, par value $0.001, and, as of May 1, 2005, we had 49,922,468 shares of common stock outstanding. As of June 1, 2005, we had an aggregate of 10,000,000 shares of common stock reserved for issuance upon exercise of stock options granted, or to be granted, under our Amended and Restated 2001 Stock Plan and 2004 Stock Plan. As of June 1, 2005, we had warrants to purchase an aggregate of approximately 11,675,846 shares of our common stock outstanding.

Voting Rights

     Holders of our common stock are entitled to one vote per share on all matters to be voted upon by the stockholders. The holders of common stock are not entitled to cumulate voting rights with respect to the election of directors, which means that the holders of a majority of the shares voted can elect all of the directors then standing for election.

Dividends

     Subject to limitations under Nevada law and preferences that may apply to any outstanding shares of preferred stock, holders of our common stock are entitled to receive ratably such dividends or other distribution, if any, as may be declared by our board of directors out of funds legally available therefor.

Liquidation

     In the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in all assets remaining after payment of liabilities, subject to the liquidation preference of any outstanding preferred stock.

Rights and Preferences

     The common stock has no preemptive, conversion or other rights to subscribe for additional securities. There are no redemption or sinking fund provisions applicable to our common stock. The rights, preferences and privileges of holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that we may designate and issue in the future.

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Fully Paid and Nonassessable

     All outstanding shares of our common stock are, and all shares of common stock to be outstanding upon completion of the offering will be, validly issued, fully paid and nonassessable.

Transfer Agent and Registrar

     The transfer agent and registrar for our common stock is Corporate Stock Transfer Company.

DESCRIPTION OF PREFERRED STOCK

     We currently have authorized 20,000,000 shares of preferred stock, $0.001 par value per share. All shares of preferred stock are undesignated. As of the date of this prospectus, we did not have any shares of preferred stock outstanding.

     Our Board of Directors is authorized to fix and determine designations, preferences, privileges, rights, and powers and relative, participating, optional, or other special rights, qualifications, limitations, or restrictions on the preferred stock of Halozyme as provided by Nevada Revised Statutes.

     The purpose of authorizing our Board of Directors to issue preferred stock in one or more series and determine the number of shares in the series and its rights and preferences is to eliminate delays associated with a stockholder vote on specific issuances. Examples of rights and preferences that the Board of Directors may fix are: (1) dividend rights, (2) dividend rates, (3) conversion rights, (4) voting rights, (5) terms of redemption, and (6) liquidation preferences. The issuance of preferred stock, while providing desirable flexibility in connection with possible acquisitions and other corporate purposes, could make it more difficult for a third party to acquire, or could discourage a third party from acquiring, a majority of our outstanding voting stock. The rights of holders of our common stock described above, will be subject to, and may be adversely affected by, the rights of any preferred stock that we may designate and issue in the future.

     We will incorporate by reference as an exhibit to the registration statement which includes this prospectus the form of any certificate of designation which describes the terms of the series of preferred stock we are offering. This description and the applicable prospectus supplement will include:

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     If we issue shares of preferred stock under this prospectus, the shares will fully be paid and nonassessable and will not have, or be subject to, any preemptive or similar rights.

     The Nevada Revised Statutes provides that the holders of preferred stock will have the right to vote separately as a class on any proposal involving an increase or decrease in the authorized number of shares of that class, or changes in the powers, preferences or special rights of holders of that preferred stock so as to affect the class adversely. This right is in addition to any voting rights that may be provided for in the applicable certificate of designation.

     The transfer agent and registrar for any series of preferred stock will be set forth in the applicable prospectus supplement.

DESCRIPTION OF DEBT SECURITIES

     The following description, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future debt securities we may offer, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. If we indicate in a prospectus supplement, the terms of any debt securities we offer under that prospectus supplement may differ from the terms we describe below.

     We will issue any senior notes under the senior indenture which we will enter into with a trustee to be named in the senior indenture. We will issue any subordinated notes under the subordinated indenture which we will enter into with a trustee to be named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement which includes this prospectus. We use the term “indentures” to refer to both the senior indenture and the subordinated indenture. The indentures will be qualified under the Trust Indenture Act of 1939. We use the term “debenture trustee” to refer to either the senior trustee or the subordinated trustee, as applicable.

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     The following summaries of material provisions of the senior notes, the subordinated notes and the indentures are subject to, and qualified in their entirety by reference to, all the provisions of the indenture applicable to a particular series of debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

     We conduct some of our operations through a subsidiary formed under the laws of California. Our rights and the rights of our creditors, including holders of debt securities, to the assets of any subsidiary of ours upon that subsidiary’s liquidation or reorganization or otherwise would be subject to the prior claims of that subsidiary’s creditors, except to the extent that we may be a creditor with recognized claims against the subsidiary. Our subsidiary’s creditors would include trade creditors, debt holders, secured creditors and taxing authorities. Except as we may provide in a prospectus supplement, neither the debt securities nor the indentures restrict us or our subsidiary from incurring indebtedness.

General

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Conversion or Exchange Rights

     We will set forth in the prospectus supplement the terms on which a series of notes may be convertible into or exchangeable for common stock or other securities of ours. We will include in that prospectus supplement provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of common stock or other securities of ours that the holders of the series of notes receive would be subject to adjustment.

Consolidation, Merger or Sale of Assets

     The indentures do not contain any covenant which restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the notes, as appropriate.

Events of Default Under the Indenture

     The following are events of default under the indentures with respect to any series of notes that we may issue:

     If an event of default with respect to notes of any series occurs and is continuing, the debenture trustee or the holders of at least 50% in aggregate principal amount of the outstanding notes of that series, by notice to us in writing, and to the debenture trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately.

     The holders of a majority in principal amount of the outstanding notes of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

     Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the debenture trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of notes, unless such holders

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have offered the debenture trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding notes of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the debenture trustee, or exercising any trust or power conferred on the debenture trustee, with respect to the notes of that series, provided that:

     A holder of the notes of any series will only have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:

     These limitations do not apply to a suit instituted by a holder of notes if we default in the payment of the principal, premium, if any, or interest on, the notes.

     We will periodically file statements with the debenture trustee regarding our compliance with specified covenants in the indentures.

Modification of Indenture; Waiver

     We and the debenture trustee may change an indenture without the consent of any holders with respect to specific matters, including:

     In addition, under the indentures, the rights of holders of a series of notes may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding notes of each series that is affected. However, we and the debenture trustee may only make the following changes with the consent of each holder of any outstanding notes affected:

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Discharge

     Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for obligations to:

     In order to exercise our rights to be discharged, we must deposit with the debenture trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange, and Transfer

     We will issue the notes of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue notes of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depository named by us and identified in a prospectus supplement with respect to that series. See “Legal Ownership of Securities” for a further description of the terms relating to any book-entry securities.

     At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the notes of any series can exchange the notes for other notes of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

     Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the notes may present the notes for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the notes that the holder presents for transfer or exchange, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

     We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any notes. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the notes of each series.

     If we elect to redeem the notes of any series, we will not be required to:

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Information Concerning the Debenture Trustee

     The debenture trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the debenture trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the debenture trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of notes unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

     Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any notes on any interest payment date to the person in whose name the notes, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

     We will pay principal of and any premium and interest on the notes of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, will we make interest payments by check which we will mail to the holder. Unless we otherwise indicate in a prospectus supplement, we will designate the corporate trust office of the debenture trustee in the City of New York as our sole paying agent for payments with respect to notes of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the notes of a particular series. We will maintain a paying agent in each place of payment for the notes of a particular series.

     All money we pay to a paying agent or the debenture trustee for the payment of the principal of or any premium or interest on any notes which remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the security thereafter may look only to us for payment of those amounts.

Governing Law

     The indentures and the notes will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

Subordination of Subordinated Notes

     The subordinated notes will be unsecured and will be subordinate and junior in priority of payment to some or all of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated notes which we may issue. It also does not limit us from issuing any other secured or unsecured debt.

DESCRIPTION OF WARRANTS

     The following description, together with the additional information we may include in any applicable prospectus supplements, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and the related warrant agreements and warrant certificates. While the terms summarized below will apply generally to any warrants that we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. If we indicate in the prospectus supplement, the terms of any warrants offered under that prospectus supplement may differ from the terms described below. Specific warrant agreements will contain additional important terms and provisions and will be incorporated by reference as an exhibit to the registration statement which includes this prospectus.

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General

     We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities.

     We will evidence each series of warrants by warrant certificates that we will issue under a separate warrant agreement. We will enter into the warrant agreement with a warrant agent. Each warrant agent will be a bank that we select which has its principal office in the United States and a combined capital and surplus of at least $50,000,000. We will indicate the name and address of the warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

     We will describe in the applicable prospectus supplement the terms of the series of warrants, including:

     Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

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Exercise of Warrants

     Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to 5:00 P.M. New York time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

     Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent upon exercise.

     Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Enforceability of Rights By Holders of Warrants

     Each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue or series of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

LEGAL OWNERSHIP OF SECURITIES

     We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

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Book-Entry Holders

     We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

     Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

     As a result, investors in a book-entry security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not holders, of the securities.

Street Name Holders

     We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

     For securities held in street name, we will recognize only the banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

Legal Holders

     Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

     For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depositary participants or customers or by law, to pass the payment or notice along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, such as to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the holders.

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Special Considerations for Indirect Holders

     If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

Global Securities

     A global security is a security held by a depositary which represents one or more individual securities. Generally, all securities represented by the same global securities will have the same terms.

     Each security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, The Depository Trust Company, New York, New York, known as DTC, will be the depositary for all securities issued in book-entry form.

     A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under the section titled “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a holder of the security, but only an indirect holder of a beneficial interest in the global security.

     If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations for Global Securities

     As an indirect holder, an investor’s rights relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

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     If securities are issued only in the form of a global security, an investor should be aware of the following:

Special Situations When a Global Security Will Be Terminated

     In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

     The global security will terminate when the following special situations occur:

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     The prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

ADDITIONAL INFORMATION CONCERNING OUR CAPITAL STOCK

Nevada Law

     We are subject to certain provisions of the Nevada Revised Statutes (the “Revised Statutes”) which could delay or make more difficult a merger or tender offer involving Halozyme.

     Sections 78.378 to 78.3793, inclusive, of the Revised Statutes relate to the acquisitions of a controlling interest in a corporation. Such provisions apply to Nevada corporations that have at least 200 shareholders, at least 100 being Nevada residents, and that do business directly or indirectly in Nevada. Where applicable, Nevada law prohibits an acquiror from voting shares of a target company after exceeding certain threshold ownership percentages, until the acquiror provides certain information to the company and a majority of the disinterested shareholders vote to restore the voting rights of the acquiror’s shares at a meeting called at the request and expense of the acquiror. If the voting rights of such shares are fully restored and the acquiring person obtained shares representing a majority of the outstanding shares of the corporation shareholders voting against such restoration, then those shareholders whose shares were not voted in favor of authorizing the voting rights of the acquiror may demand payment for the “fair value” of their shares.

     The Revised Statutes, 78.411 to 78.444, inclusive, also restrict a “business combination” with “interested shareholders”, unless certain conditions are met, with respect to corporations that have a least 200 shareholders of record. An “interested shareholder” is a person who, together with affiliates and associates, beneficially owns (or within the prior three years, did beneficially own) 10% or more of the corporation’s voting stock. A “business combination” includes:

     A corporation to which this statute applies may not engage in a combination within three years after the interested shareholder acquired its shares, unless the combination or the interested shareholder’s acquisition of shares was approved by the board of directors before the interested shareholder acquired the shares. If this

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approval was not obtained, then after the three year period expires, the combination may be consummated if all applicable statutory requirements are met and either:

Charter Document Provisions

     Our bylaws provide that the Board of Directors is divided into three classes of directors, with each class serving a staggered three-year term. The classification system of electing directors may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of Halozyme and may maintain the incumbency of the Board of Directors, as it generally makes it more difficult for stockholders to replace a majority of the directors. Our Bylaws do not permit stockholders to act without a meeting and do not provide for cumulative voting in the election of directors. The amendment of any of these provisions would require approval by holders of at least a majority of the shares of outstanding common stock.

     These and other provisions of our amended and restated articles of incorporation, including, but not limited to the Board of Directors’ ability to designate the rights and preferences of our preferred stock, could have the effect of deterring certain takeovers or delaying or preventing certain changes in control or management of Halozyme, including transactions in which stockholders might otherwise receive a premium for their shares over then-current market prices.

PLAN OF DISTRIBUTION

     The securities being offered may be sold in one or more transactions at fixed prices, at prevailing market prices at the time of sale, at prices related to the prevailing market prices, at varying prices determined at the time of sale, or at negotiated prices. These sales may be effected at various times in one or more of the following transactions, or in other kinds of transactions:

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     We may sell our securities directly to one or more purchasers, or to or through underwriters, dealers or agents or through a combination of those methods. The related prospectus supplement will set forth the terms of each offering, including:

     In addition, any securities covered by this prospectus which qualify for sale pursuant to Regulation S of the Securities Act of 1933, as amended (the “Securities Act”), may be sold pursuant to Regulation S rather than pursuant to this prospectus.

     In connection with the sale of our common stock, underwriters may receive compensation from us or from purchasers of our common stock in the form of discounts, concessions or commissions. Underwriters, dealers and agents that participate in the distribution of our common stock may be deemed to be underwriters. Discounts or commissions they receive and any profit on their resale of our common stock may be considered underwriting discounts and commissions under the Securities Act.

     We may agree to indemnify underwriters, dealers and agents who participate in the distribution of our common stock against various liabilities, including liabilities under the Securities Act of 1933. We may also agree to contribute to payments which the underwriters, dealers or agents may be required to make in respect of these liabilities. We may authorize dealers or other persons who act as our agents to solicit offers by various institutions to purchase our common stock from us under contracts which provide for payment and delivery on a future date. We may enter into these contracts with commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and others. If we enter into these

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agreements concerning any series of our common stock, we will indicate that in the prospectus supplement or amendment.

     In connection with an offering of our common stock, underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of our common stock. Specifically, underwriters may over-allot in connection with the offering, creating a syndicate short position in our common stock for their own account. In addition, underwriters may bid for, and purchase, our common stock in the open market to cover short positions or to stabilize the price of our common stock. Finally, underwriters may reclaim selling concessions allowed for distributing our common stock in the offering if the underwriters repurchase previously distributed common stock in transactions to cover short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of our common stock above independent market levels. Underwriters are not required to engage in any of these activities and may end any of these activities at any time. Agents and underwriters may engage in transactions with, or perform services for, us and our affiliates in the ordinary course of business.

LEGAL MATTERS

     The validity of the securities offered hereby and other legal matters relating to the offering will be passed upon for us by Hale Lane Peek Dennison and Howard, Reno, Nevada.

EXPERTS

     The financial statements incorporated in this prospectus by reference to the Annual Report on Form 10-KSB for the year ended December 31, 2004, have been so incorporated in reliance on the report of Cacciamatta Accountancy Corporation, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.

     Our expenses in connection with the distribution of the securities being registered hereunder will be substantially as follows (all expenses other than the SEC Registration Fee are estimates):

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Our amended and restated articles of incorporation provide for the indemnification of our directors, officers, employees and agents to the fullest extent permitted by the laws of the State of Nevada. Section 78.7502 of the Nevada Revised Statutes permits a corporation to indemnify any of its directors, officers, employees or agents against expenses actually and reasonably incurred by such person in connection with any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (except for an action by or in right of the corporation) by reason of the fact that such person is or was a director, officer, employee or agent of the corporation, provided that it is determined that such person acted in good faith and in a manner which he reasonably believed to be in, or not opposed to, the best interests of the corporation and, with respect to any criminal action or proceeding, had no reasonable cause to believe his conduct was unlawful.

     Section 78.751 of the Nevada Revised Statutes requires that the determination that indemnification is proper in a specific case must be made by (a) the stockholders, (b) the board of directors by majority vote of a quorum consisting of directors who were not parties to the action, suit or proceeding or (c) independent legal counsel in a written opinion (i) if a majority vote of a quorum consisting of disinterested directors is not possible or (ii) if such an opinion is requested by a quorum consisting of disinterested directors.

     Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, we have been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

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ITEM 16. EXHIBITS.

ITEM 17. UNDERTAKINGS.

The undersigned Registrant hereby undertakes:

(i) To include any prospectus required by section 10(a)(3) of the Securities Act of 1933 (the “Securities Act”);

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement;

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement; provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in periodic reports filed by the Registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement.

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     The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to section 13(a) or section 15(d) of the Securities Exchange Act of 1934 that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

     The undersigned Registrant hereby undertakes to deliver or cause to be delivered with the prospectus, to each person to whom the prospectus is sent or given, the latest annual report to security holders that is incorporated by reference in the prospectus and furnished pursuant to and meeting the requirements of Rule 14a-3 or Rule 14c-3 under the Securities Exchange Act of 1934; and, where interim financial information required to be presented by Article 3 of Regulation S-X are not set forth in the prospectus, to deliver, or cause to be delivered to each person to whom the prospectus is sent or given, the latest quarterly report that is specifically incorporated by reference in the prospectus to provide such interim financial information.

     Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers, and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer, or controlling person of the Registrant in the successful defense of any action, suit, or proceeding) is asserted by such director, officer, or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

     The undersigned Registrant hereby undertakes that:

     For the purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the Registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of the registration statement as of the time it was declared effective.

     For the purposes of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Post-Effective Amendment to the registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of San Diego, State of California, on June 10, 2005.

POWER OF ATTORNEY

     KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Jonathan E. Lim and David A. Ramsay, and each of them, his or her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities including his or her capacity as a director and/or officer of Halozyme Therapeutics, Inc., to sign any and all amendments (including post-effective amendments) to this registration statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his or her substitute or substitutes, may lawfully do or cause to be done by virtue thereof.

     Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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INDEX TO EXHIBITS