Onconetix Inc 美股招股说明书（2026-05-12版）

PROSPECTUS 25,000,000 shares of Common Stock This prospectus relates to the offer and sale from time to time by Keystone Capital Partners, LLC (“Keystone” or the “SellingStockholder”) of up to 25,000,000 shares of common stock of Onconetix, Inc. (“we,” “us,” “our,” the “Company,” or “Onconetix”),par value $0.00001 per share (the “Common Stock”), that have been or may be issued by us to Keystone pursuant to that certainCommon Stock ELOC Purchase Agreement, dated as of October 2, 2024, by and between us and Keystone (the “ELOC PurchaseAgreement”), establishing an equity line of credit (“ELOC”). Such shares of our Common Stock include up to 25,000,000 shares ofCommon Stock (assuming the shares to be issued are sold at a price of approximately $0.6771 per share, which, in accordance with the The actual number of shares of our Common Stock issuable will vary depending on the then-current market price of shares of ourCommon Stock sold to the Selling Stockholder under the ELOC Purchase Agreement, but will not exceed the number set forth in thepreceding sentences unless we file an additional registration statement under the Securities Act of 1933, as amended (the “Securities We are registering the shares on behalf of the Selling Stockholder, to be offered and sold by it from time to time. We are notselling any securities under this prospectus, and will not receive any proceeds from the sale of Common Stock by the SellingStockholder pursuant to this prospectus. We may receive up to $25.0 million in aggregate gross proceeds from Keystone under theELOC Purchase Agreement in connection with sales of the shares of our Common Stock pursuant to the ELOC Purchase Agreement atvarying purchase prices after the date of this prospectus. However, the actual proceeds from Keystone may be less than this amountdepending on the number of shares of our Common Stock sold and the price at which the shares of our Common Stock are sold. Our Common Stock is listed on The Nasdaq Capital Market under the symbol “ONCO.” The last reported sale price of ourCommon Stock on The Nasdaq Capital Market on May 7, 2026 was $0.404 per share. We recommend that you obtain current market The Selling Stockholder is an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act. The Selling Stockholdermay offer all or part of the shares for resale from time to time through public or private transactions, at either prevailing market pricesor at privately negotiated prices. Our registration of the shares of Common Stock covered by this prospectus does not mean that theSelling Stockholder will offer or sell any of the shares. With regard only to the shares the Selling Stockholder sells for its own behalf, We will pay the expenses incurred in registering the shares, including legal and accounting fees. See “Plan of Distribution” onpage 41 of this prospectus. Investing in our Common Stock involves certain risks. See “Risk Factors” on page 10 of this prospectus, included in anyaccompanying prospectus supplement and in the documents incorporated by reference in this prospectus for a discussion of We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. Weurge you to read the entire prospectus, any amendments or supplements, any free writing prospectuses, and any documents Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminaloffense. The date of this prospectus is May 7, 2026 TABLE OF CONTENTS ABOUT THIS PROSPECTUS ABOUT THIS PROSPECTUS This prospectus is part of a registration statement on Form S-1 that we filed with the Securities and Exchange Commission (the“SEC”) for the delayed or continuous offering and sale of securities pursuant to Rule 415 under the Securities Act. This prospectusgenerally describes Onconetix, Inc. and our Common Stock. The Selling Stockholder may use this registration statement to sell up toan aggregate of up to 25,000,000 shares of our Common Stock from time to time through any means described in the section entitled“Plan of Distribution.” Our registration of the securities covered by this prospectus does not mean that either we or the Selling We will not receive any proceeds from the sale of Common Stock by the Selling Stockholder pursuant to this prospectus.However, we will pay the expenses, other than underwriting discounts and commissions, associated with the sale of shares pursuant tothis prospectus. We may receive up to $25.0 million in aggregate gross proceeds from Keystone under the ELOC Purchase Agreementin connection with sales of the shares of our Common Stock pursuant to the ELOC Purchase Agreement after the date of this We and the Selling Stockholder, as applicable, may deliver a prospectus supplement with this prospectus, to the extentappropriate, to update