Filed Pursuant to Rule 424(b)(3) and (c)
Registration No. 333-114776

HALOZYME THERAPEUTICS, INC.

PROSPECTUS SUPPLEMENT #1
(To Prospectus dated April 1, 2005)

     This prospectus supplement supplements the Halozyme Therapeutics, Inc. prospectus dated April 1, 2005, which originally related to the sale of up to 23,740,622 shares of our common stock by certain selling security holders. This Prospectus Supplement No. 1 should be read in conjunction with the original prospectus and this Prospectus Supplement No. 1 is qualified by reference to the original prospectus, except to the extent that the information provided by this Prospectus Supplement No. 1 supersedes the information contained in the original prospectus.

     SEE “RISK FACTORS” CONTAINED IN OUR MOST RECENT PERIODIC FILINGS WITH THE SECURITIES AND EXCHANGE COMMISSION TO READ ABOUT FACTORS YOU SHOULD CONSIDER BEFORE MAKING A DECISION TO PURCHASE OUR COMMON STOCK.

     The shares offered or sold under this prospectus have not been approved by the Securities and Exchange Commission or any state securities commission nor have any of these organizations determined that this prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

The date of this Prospectus Supplement No. 1 is March 16, 2007.

     The sections of the prospectus, dated April 1, 2005, titled “Use of Proceeds”, “Selling Security Holders” and “Plan of Distribution” are superseded in their entirety by the following:

USE OF PROCEEDS

     We will not receive proceeds from the sale of shares under this prospectus, but we did receive consideration from the selling security holders at the time they purchased the shares. We may receive proceeds from the exercise price of the warrants if they are exercised by the selling security holders. Assuming the exercise of all remaining Warrants held by the selling security holders, we would receive gross proceeds of approximately $5.0 million. We intend to use any proceeds from the exercise of the Warrants for working capital and general corporate purposes.

SELLING SECURITY HOLDERS

     The shares are being offered by certain selling security holders. The selling security holders may from time to time offer and sell pursuant to this prospectus up to an aggregate of 5,985,858 shares of our common stock now owned by them or issuable to them upon the exercise of warrants. The selling security holders may, from time to time, offer and sell any or all of the shares that are registered under this prospectus. Because the selling security holders are not obligated to sell their shares, and because the selling security holders may also acquire publicly traded shares of our common stock, we cannot estimate how many shares the selling security holders will own after the offering.

     None of the selling security holders has ever held an office, been a director or had any other material relationship with Halozyme or its predecessor company.

     Pursuant to the stock purchase agreements with the selling security holders, all expenses incurred with respect to the registration of the common stock will be borne by us, but we will not be obligated to pay any underwriting fees, discounts, commissions or other expenses incurred by them in connection with the sale of such shares.

     The following table sets forth, with respect to the selling security holders: (i) the number of shares of common stock covered by this prospectus, (ii) the number of shares of common stock covered by this prospectus that are issuable upon exercise of the warrants, (iii) the total shares of common stock covered by this prospectus, (iv) the total number of shares of common stock beneficially owned but not covered by this prospectus*, (v) the total number of shares of company stock beneficially owned by such selling security holders as of March 1, 2007*, and (vi) the percentage of shares of common stock beneficially owned as of March 1, 2007, based upon approximately 71.0 million shares of common stock outstanding as of March 1, 2007.

*    Each selling security holder’s beneficial ownership total reflects shares owned beneficially as of August 12, 2004 as adjusted by (i) warrant exercises and redemptions and (ii) the sale of registered shares pursuant to the prior version(s) of this prospectus from that date through March 14, 2007, and such totals do not include any shares that were sold pursuant to Rule 144 or that were purchased or sold on the open market unless such purchases and sales were reported in public filings made with the Securities and Exchange Commission.

SELLING SECURITY HOLDERS

						Shares of								Shares of
						Common				Total Shares of				Common
		Shares of				Stock Issuable				Common Stock				Stock Beneficially				Total Shares of				Total
		Common				Upon				Equivalents				Owned But NOT				Common Stock				Beneficial
		Stock Being				Exercise of				Being				Being				Beneficially				Ownership
Security Holders		Registered				Warrants				Registered				Registered				Owned				%
Anthony Salandra			2,200				57,223				59,423				70,673				130,096				0.18	%
Asia Pacific Imports			7,500				11,250				18,750				56,250				75,000				0.10	%
Autry Qualified Interest Trust			29,500				45,500				75,000				225,000				300,000				0.42	%
BioGrowth, Inc.			140,569				—				140,569				—				140,569				0.19	%
Bonanza Master Fund, LTD			88,700				136,300				225,000				1,700,586				1,925,586				2.70	%
Brean Murray, Carret & Co., LLC			107,700				165,513				273,213				—				273,213				0.38	%
Centrum Bank AG			45,500				—				45,500				—				45,500				0.06	%
Darren Blanton			90,000				322,788				412,788				927,074				1,339,862				1.87	%
David Hochman			—				2,350				2,350				—				2,350				0.00	%
Dr. Donald Cramer			—				637				637				2,500				3,137				0.00	%
Dr. Leonard Makowka			3,750				—				3,750				11,250				15,000				0.02	%
Forest Hill Select Fund, LP			120,000				—				120,000				321,417				441,417				0.62	%
Franklin H. Nyi			11,800				18,200				30,000				90,000				120,000				0.16	%
Gene Salkind, MD			23,600				36,400				60,000				305,000				365,000				0.51	%
Global Securities Corporation			20,000				—				20,000				—				20,000				0.02	%
Harvest International			—				107,596				107,596				107,596				215,192				0.30	%
Henri Talerman			15,000				15,000				30,000				80,000				110,000				0.15	%
Hyde Family Trust			20,000				10,000				30,000				90,000				120,000				0.16	%
Icon Investors Limited			89,842				—				89,842				—				89,842				0.12	%
Jacqueline Autry			5,900				9,100				15,000				45,000				60,000				0.08	%
Jerome Morgan			1,300				2,000				3,300				9,900				13,200				0.01	%
Jesse Grossman			58,022				442,891				500,913				1,260,695				1,761,608				2.46	%
Fidelity Management Trust Co FBO Jesse Grossman IRA			160,078				—				160,078				—				160,078				0.23	%
John Paul DeJoria			11,800				18,200				30,000				40,000				70,000				0.10	%
Jonathan Spanier			163,800				359,513				523,313				1,209,423				1,732,736				2.42	%
Keith Granirer			—				1,713				1,713				7,500				9,213				0.01	%
Ken Rickel			34,000				267,442				301,442				462,042				763,484				1.07	%
Ken Y. Leung			11,800				18,200				30,000				80,000				110,000				0.15	%

						Shares of								Shares of
						Common				Total Shares of				Common
		Shares of				Stock Issuable				Common Stock				Stock Beneficially				Total Shares of				Total
		Common				Upon				Equivalents				Owned But NOT				Common Stock				Beneficial
		Stock Being				Exercise of				Being				Being				Beneficially				Ownership
Security Holders		Registered				Warrants				Registered				Registered				Owned				%
Kingsbridge Capital			22,100				34,150				56,250				250				56,500				0.07	%
Laura Stone			1,650				1,650				3,300				10,115				13,415				0.01	%
Lawrence Diamant			—				812				812				3,938				4,750				0.00	%
Linda May Stone			5,900				9,100				15,000				41,400				56,400				0.07	%
Lore E. Stone Trust, Lore E. Stone, trustee			9,000				—				9,000				27,000				36,000				0.05	%
Louis F. Burke PC Retirement Trust			2,900				4,600				7,500				20,000				27,500				0.03	%
Michael P. Marcus			—				18,200				18,200				20,000				38,200				0.05	%
Michael Stone			317,394				—				317,394				629,394				946,788				1.33	%
Nadine Smith			19,092				95,297				114,389				—				114,389				0.16	%
Odyssey Holdings Ltd.			20,000				—				20,000				—				20,000				0.02	%
Oppenheimer & Co. Inc. Custodian for Jonathan Spanier IRA Rollover			62,500				96,177				158,677				474,890				633,567				0.89	%
Paul Rosenberg			—				53,798				53,798				3,798				57,596				0.08	%
Peter Geddes			218,100				335,219				553,319				1,664,618				2,217,937				3.10	%
Peter Geddes Custodian for Campbell Geddes under CUTMA, age 21			7,300				11,450				18,750				50,000				68,750				0.09	%
Peter Geddes Custodian for Lily Geddes under CUTMA, age 21			7,300				11,450				18,750				50,000				68,750				0.09	%
Peter Graffman			3,600				5,775				9,375				68,175				77,550				0.10	%
Peter Kosa			35,000				—				35,000				—				35,000				0.04	%
Richard Genovese			120,000				614,892				734,892				1,230,746				1,965,638				2.74	%
Roth Capital Partners, LLC			41,900				94,400				136,300				—				136,300				0.19	%
Sean Fitzpatrick			1,100				—				1,100				—				1,100				0.00	%
Spectrum Advisors, Ltd.			—				22,800				22,800				3,000				25,800				0.03	%
Steven S. Vender			6,600				10,275				16,875				50,000				66,875				0.09	%
TBG America Inc.			—				18,200				18,200				—				18,200				0.02	%
The Ward Family Foundation			17,700				27,300				45,000				135,000				180,000				0.25	%
University Finance, Inc.			130,000				—				130,000				—				130,000				0.18	%

						Shares of								Shares of
						Common				Total Shares of				Common
		Shares of				Stock Issuable				Common Stock				Stock Beneficially				Total Shares of				Total
		Common				Upon				Equivalents				Owned But NOT				Common Stock				Beneficial
		Stock Being				Exercise of				Being				Being				Beneficially				Ownership
Security Holders		Registered				Warrants				Registered				Registered				Owned				%
Vega Investments Inc.			30,700				47,300				78,000				—				78,000				0.10	%
Vertical Ventures, LLC			—				45,500				45,500				—				45,500				0.06	%
William F. Miller III			8,800				13,700				22,500				115,000				137,500				0.19	%
Winnie Huang			5,900				9,100				15,000				45,000				60,000				0.08	%
Total			2,356,897				3,628,961				5,985,858				11,744,23062				17,730,088				24.60	%

     Subject to applicable exceptions set forth by the Securities and Exchange Commission, transferees, pledgees, donees or successors to the selling security holders named in the prospectus may not offer and sell securities pursuant to the prospectus unless we supplement or amend the prospectus to reflect the required information concerning such transferees, pledgees, donees or successors.

PLAN OF DISTRIBUTION

     The selling security holders and any of their pledgees, assignees and successors-in-interest may, from time to time, sell all or any part of their shares of common stock offered hereby on any stock exchange, market or trading facility on which the shares are traded or in private transactions. These sales may be at fixed or negotiated prices. The selling security holders may use any one or more of the following methods when selling shares:

	•		ordinary brokerage transactions and transactions in which the broker-dealer solicits purchasers;
	•		block trades in which the broker-dealer will attempt to sell the shares as agent but may position and resell a portion of the block as principal to facilitate the transaction;
	•		purchases by a broker-dealer as principal and resale by the broker-dealer for its account;
	•		an exchange distribution in accordance with the rules of the applicable exchange;
	•		privately negotiated transactions;
	•		short sales;
	•		broker-dealers may agree with the selling security holders to sell a specified number of such shares at a stipulated price per share;
	•		a combination of any such methods of sale; and
	•		any other method permitted pursuant to applicable law.

     The selling security holders may also sell shares under Rule 144 under the Securities Act, if available, rather than under this prospectus. The selling security holders may also engage in short sales against the box, puts and calls and other transactions in our securities or derivatives of our securities, and may sell or deliver shares in connection with these trades. The selling security holders may pledge their shares to their brokers under the margin provisions of customer agreements. If a selling security holder defaults on a margin loan, the broker may, from time to time, offer and sell the pledged shares.

     Broker-dealers engaged by the selling security holders may arrange for other broker-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the selling security holders (or, if any broker-dealer acts as agent for the purchaser of shares, from the purchaser) in amounts to be negotiated. The selling security holders do not expect these commissions and discounts to exceed what is customary in the types of transactions involved.

     The selling security holders and any broker-dealers or agents that are involved in selling the shares may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. Any selling security holders that are broker-dealers or broker-dealer affiliates will be deemed to be “underwriters” within the meaning of the Securities Act in connection with any sales of the shares by them. In such event, any commissions received by such broker-dealers or agents and any profit on the resale of the shares purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Of the selling security holders Brean Murray, Carret & Co., LLC; Grant Bettingern, Inc.; and Roth Capital Partners, LLC are each broker-dealers.

     Because selling security holders may be deemed to be “underwriters” within the meaning of Section 2(11) of the Securities Act, the selling security holders will be subject to the prospectus delivery requirements of the Securities Act and the rules promulgated thereunder. We have informed the selling security holders that the anti-manipulative provisions of Regulation M promulgated under the Exchange Act may apply to their sales in the market.

     We have agreed to indemnify certain of the selling security holders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act.

     After being notified by a selling security holder that any material arrangement has been entered into with a broker-dealer or underwriter for the sale of shares through a block trade, special offering, exchange distribution or secondary distribution or a purchase by a broker, dealer or underwriter, we will file a supplement to this prospectus, if required, pursuant to Rule 424(b) under the Securities Act, disclosing (i) the name of each such selling security holder and of the participating broker-dealer(s) or underwriter(s), (ii) the number of shares involved, (iii) the price at which such shares were sold, (iv) the commissions paid or discounts or concessions allowed to such broker-dealer(s) or underwriter(s), where applicable, (v) that such broker-dealer(s) or underwriter(s) did not conduct any investigation to verify the information set out or incorporated by reference in this prospectus and (vi) other facts material to the transaction. Individuals and entities who receive shares from the selling security holders as a gift or in connection with a pledge may sell up to 500 of such shares pursuant to this prospectus.