Halozyme Therapeutics, Inc.

Item 1.01 Entry into a Material Definitive Agreement. Convertible Notes Indentures On September 22, 2026, Halozyme Therapeutics, Inc. (the “Company,” “we,” “us” or “our”) completed its previously announced sale of $1,500.0 million aggregate principal amount of 1.50% Convertible Senior Notes due 2033 (the “Convertible Notes”), including $200.0 million in aggregate principal amount of its Convertible Notes purchased pursuant to the exercise by the initial purchasers (the “Initial Purchasers”) of the Convertible Notes of the option (the “Convertible Notes Option”) to purchase additional Convertible Notes. The Convertible Notes were issued pursuant to an indenture, dated as of September 22, 2026, (the “Indenture”) between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”). The Company offered and sold the Convertible Notes in reliance on the exemption from registration provided by Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). The Initial Purchasers offered and sold the Convertible Notes to “qualified institutional buyers” pursuant to the exemption from registration provided by Rule 144A under the Securities Act. The offer and sale of the Convertible Notes and the shares of common stock issuable upon conversion of the Convertible Notes have not been registered under the Securities Act, or the securities laws of any other jurisdiction, and the Convertible Notes and such shares may not be offered or sold absent registration or an applicable exemption from registration requirements, or in a transaction not subject to, such registration requirements. The Company received net proceeds from the offering of approximately $1,471.1 million after deducting the Initial Purchasers’ discounts and commissions and the Company’s estimated offering expenses. The Company used approximately $187.5 million of the net proceeds of the offering to fund the cost of entering into the Capped Call Transactions (as defined herein). In addition, the Company expects to use a portion of the net proceeds of the offering to repurchase for cash approximately $151.7 million aggregate principal amount of its outstanding 0.25% convertible senior notes due 2027 (the “2027 Notes”) and $220.0 million aggregate principal amount of its outstanding 1.00% convertible senior notes due 2028 (the “2028 Notes” and, together with the 2027 Notes, the “Existing Convertible Notes”) for a total repurchase cost (including accrued and unpaid interest) of approximately $217.0 million of the 2027 Notes and a total repurchase cost (including accrued and unpaid interest) of approximately $435.5 million of the 2028 Notes in privately negotiated transactions effected through one of the initial purchasers of the Convertible Notes or its affiliate, as the Company’s agent (the “Note Repurchases”). The Company intends to use the remainder of the net proceeds from the offering for general corporate purposes, including working capital, capital expenditures, potential acquisitions and strategic transactions, and, potentially, future note repurchases including repurchases of the Existing Convertible Notes from time to time or for the repayment of the Convertible Notes at maturity or upon early optional redemption at the Company’s discretion. The Convertible Notes will pay interest semi-annually in arrears on April 1st and October 1st of each year, beginning on April 1, 2027, at an annual rate of 1.50%. The Convertible Notes will be convertible into cash, and, if applicable, shares of the Company’s common stock, at the Company’s election, based on the applicable conversion rate at such time. The Convertible Notes are unsecured obligations of the Company and will rank senior in right of payment to all of the Company’s indebtedness that is expressly subordinated in right of payment to the Convertible Notes, will rank equally in right of payment with all of the Company’s existing and future liabilities that are not so subordinated, will be effectively junior to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness and will be structurally subordinated to all indebtedness and other liabilities (including trade payables) of the Company’s current or future subsidiaries. Holders may convert their Convertible Notes at their option only in the following circumstances: (1) during the 30 consecutive trading days immediately after the period consisting of the first 20 trading days of any calendar quarter commencing after the calendar quarter ending on December 31, 2026, if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price for each of at least five trading days during such 20-day trading period; (2) during the five consecutive business days immediately after any five consecutive trading day period (such five consecutive trading day period, the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock, as described in the Indenture; (4) if the Company calls such notes for redemption; and (5) at any time from, and including April 1, 2033, until the close of business on the second scheduled trading day immediately before the maturity date. The initial conversion rate for the Convertible Notes will be 7.1509 shares of common stock per $1,000 in principal amount of Convertible Notes, equivalent to a conversion price of approximately $139.84 per share of common stock. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued or unpaid interest. Subject to certain exceptions, holders may require the Company to repurchase, for cash, all or part of their Convertible Notes upon a “Fundamental Change” (as defined in the Indenture) at a price equal to 100% of the principal amount of the Convertible Notes being repurchased plus, any accrued and unpaid interest, if any, and up to, but excluding, the “Fundamental Change Repurchase Date” (as defined in the Indenture). In addition, upon a “Make-Whole Fundamental Change” (as defined in the Indenture) prior to the maturity date of the Convertible Notes, the Company will, in some cases, increase the conversion rate for a holder that elects to convert its Convertible Notes in connection with such Make-Whole Fundamental Change. The Convertible Notes will be redeemable (a “Provisional Redemption”), in whole or in part, at the Company’s option at any time, and from time to time, on or after October 7, 2030 and on or before the 30th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if (i) the Convertible Notes are “Freely Tradable” (as defined in the Indenture) as of the date the Company sends the related redemption notice and all accrued and unpaid additional interest, if any, has been paid in full, as of the first interest payment date occurring on or before the date the Company sends such notice; and (ii) the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (2) the trading day immediately before the date the Company sends such notice. In addition, calling any Convertible Note for Provisional Redemption will constitute a Make-Whole Fundamental Change with respect to that Convertible Note, in which case the conversion rate applicable to the conversion of that Convertible Note will be increased in certain circumstances if it is converted after it is called for Provisional Redemption. The Convertible Notes will also be redeemable (a “Cleanup Redemption”), in whole and not in part, at the Company’s option at any time, at a cash redemption price equal to the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if (i) the principal amount of the Convertible Notes outstanding at the time the Company sends the related redemption notice is less than $100.0 million; and (ii) the Convertible Notes are Freely Tradable as of the date the Company sends the related redemption notice and all accrued and unpaid additional interest, if any, has been paid in full, as of the first interest payment date occurring on or before the date the Company sends such notice. In addition, calling the Convertible Notes for Cleanup Redemption will constitute a Make-Whole Fundamental Change, which will require the Company to increase the conversion rate in certain circumstances for a specified period of time. The Indenture contains certain events of default after which the Convertible Notes may be due and payable immediately. Such events of default include, without limitation, the following: (1) a default in the payment when due (whether at maturity, upon redemption or repurchase upon fundamental change or otherwise) of the principal of, or the redemption price or fundamental change repurchase price for, any Convertible Note; (2) a default for 30 days in the payment when due of interest on any Convertible Note; (3) the Company’s failure to deliver, when required by the Indenture, as applicable, a fundamental change notice or other notices pursuant to such Indenture; (4) a default in the Company’s obligation to convert a Convertible Note in accordance with the Indenture upon the exercise of the conversion right with respect thereto, if such default is not cured within two business days after its occurrence; (5) a default in the Company’s obligations described in the Indenture with respect to consolidation, merger and sale of assets of the Company; (6) a default in any of the Company’s obligations or agreements under the Indenture or the Convertible Notes, (other than a default set forth in the preceding (1), (2), (3), (4) or (5)) where such default is not cured or waived within 60 days after notice to the Company by the Trustee, or to the Company and the Trustee by holders of at least 25% of the aggregate principal amount of such Convertible Notes then outstanding, which notice must specify such default, demand that it be remedied and state that such notice is a “notice of default”; (7) a default by the Company or any of the Company’s subsidiaries with respect to any one or more mortgages, agreements or other instruments under which there is outstanding, or by which there is secured or evidenced, any indebtedness for money borrowed of at least $50.0 million (or its foreign currency equivalent) in the aggregate of the Company or any of the Company’s subsidiaries, whether such indebtedness exists as of the date the Company first issues the Convertible Notes or is thereafter created, where such default: (x) constitutes a failure to pay the principal of, or premium or interest on, any of such indebtedness when due and payable at its stated maturity, upon required repurchase, upon declaration of acceleration or otherwise, in each case after the expiration of any applicable grace period; or (y) results in such indebtedness becoming or being declared due and payable before its stated maturity, in each case where such default is not cured or waived within 30 days after notice to the Company by the Trustee, as appliable, or to the Company and the Trustee by holders of at least 25% of the aggregate principal amount of such Convertible Notes then outstanding; and (8) certain events of bankruptcy, insolvency and reorganization with respect to the Company or any of the Company’s “significant subsidiaries”, as defined in the Indenture. The foregoing description of the Indenture and Convertible Notes is qualified in its entirety by reference to the text of the Indenture and the Form of Convertible Note, as applicable, copies of which are attached as Exhibits 4.1 and 4.2, respectively, to this Current Report on Form 8-K and are incorporated herein by reference. Capped Call Transactions On September 17, 2026, in connection with the pricing of the Convertible Notes, the Company entered into capped call transactions (the “Base Capped Call Transactions”) with certain of the Initial Purchasers or their respective affiliates and certain other financial institutions (collectively, the “Capped Call Counterparties”). On September 18, 2026, in connection with the Initial Purchasers’ exercise of the Convertible Notes Option, the Company entered into additional capped call transactions with the Capped Call Counterparties (together with the Base Capped Call Transactions, the “Capped Call Transactions”). The Capped Call Transactions are expected generally to reduce potential dilution to holders of our common stock on any conversion of the Convertible Notes or at our election (subject to certain conditions) offset any cash payments the Company is required to make in excess of the principal amount of such converted Convertible Notes, as the case may be, with such reduction or offset subject to a cap. The cap price of the Capped Call Transactions is initially approximately $208.39 per share of common stock, representing a premium of approximately 90.0% above the closing price of common stock on Nasdaq on September 17, 2026, and is subject to certain adjustments under the terms of the Capped Call Transactions. The Capped Call Counterparties or their respective affiliates may modify their hedge positions by entering into or unwinding various derivatives with respect to our common stock or purchasing or selling our common stock in secondary market transactions following the pricing of the Convertible Notes and prior to the maturity of the Convertible Notes (and (x) are likely to do so during any observation period related to a conversion of the Convertible Notes, following any redemption of the Convertible Notes by the Company, or following any repurchase of the Convertible Notes by the Company in connection with any fundamental change and (y) are likely to do so following any repurchase of Convertible Notes by the Company other than in connection with any such redemption or any fundamental change if the Company elects to unwind a corresponding portion of the Capped Call Transactions in connection with such repurchase). This activity could cause or avoid an increase or decrease in the market price of our common stock or the Convertible Notes, which could affect the holders’ ability to convert the Convertible Notes and, to the extent the activity occurs during any observation period related to a conversion of the Convertible Notes, it could affect the amount and value of the consideration that the holder will receive on conversion of such Convertible Notes. The Capped Call Transactions are separate transactions entered into by the Company with the Capped Call Counterparties, are not part of the terms of the Convertible Notes, and will not affect any holder’s rights under the Convertible Notes. Holders of the Convertible Notes will not have any rights with respect to the Capped Call Transactions. The form of the Capped Call Transaction confirmation (the “Capped Call Confirmation”) is filed as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated by reference. The foregoing description of the Capped Call Confirmation does not purport to be complete and is qualified in its entirety by reference to such exhibit.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth in Item 1.01 is incorporated herein by reference into this Item 2.03.

Item 3.02 Unregistered Sales of Equity Securities The information set forth in Item 1.01 is incorporated herein by reference into this Item 3.02. Any shares of the Company’s common stock that may be issued upon conversion of the Convertible Notes will be issued in reliance upon Section 3(a)(9) of the Securities Act as involving an exchange by the Company exclusively with its security holders. Initially, a maximum of 13,676,100 shares of the Company’s common stock may be issued upon conversion of the Convertible Notes, based on the initial maximum conversion rate of 9.1174 shares of common stock per $1,000 principal amount of Convertible Notes, which is subject to customary anti-dilution adjustment provisions.