赛图斯肿瘤学公司美股招股说明书(2025-09-10版)

Citius Oncology, Inc.5,142,858 Shares of Common Stock Pursuant to this prospectus supplement and the accompanying prospectus, we are offering 5,142,858 shares of our commonstock, $0.0001 par value per share, at a purchase price of $1.75 per share of common stock to a certain investor pursuant to a securitiespurchase agreement. In a concurrent private placement, we are selling to such investors warrants to purchase up to 5,142,858 shares of ourcommon stock, which represents 100% of the number of shares of our common stock being purchased in this offering (the“Warrants”). The Warrants have an exercise price of $1.84 per share, are exercisable six months from the date of issuance, and expirefive and one half years after their issuance date. The Warrants and the shares of our common stock issuable upon the exercise of theWarrants are being offered pursuant to the exemption provided in Section 4(a)(2) under the Securities Act of 1933, as amended (the“Securities Act”), and Rule 506(b) promulgated thereunder, and they are not being offered pursuant to this prospectus supplement andthe accompanying prospectus. The Warrants being issued in the concurrent private placement are not listed on any securities exchange,and we do not expect to list the Warrants. Our common stock is traded on Nasdaq under the symbol “CTOR”. We have engaged Maxim Group LLC as our exclusive placement agent (“Maxim” or the “placement agent”) to use itsreasonable best efforts to solicit offers to purchase our securities in this offering. The placement agent has no obligation to purchaseany of the securities from us or to arrange for the purchase or sale of any specific number or dollar amount of the securities. We haveagreed to pay the placement agent the placement agent fees set forth in the table below. See “Plan of Distribution” in this prospectussupplement for more information. (1)Represents a cash fee equal to 7.0% of the aggregate purchase price. We have also agreed to issue to the underwriter, or itsdesignees, at the closing of this offering, common share purchase warrants (the “Placement Agent’s Warrants”) to purchase thenumber of common shares equal to 4.0% of the aggregate number of shares of common stock sold in this offering. We have alsoagreed to reimburse the placement agent for certain expenses in connection with this offering. See “Plan of Distribution”beginning on page S-13 of this prospectus supplement for a description of the compensation to be received by the placementagent. The aggregate market value of our outstanding common stock held by non-affiliates as of the date of this prospectus is$34,685,270, based on 12,299,741 shares of outstanding common stock held by non-affiliates as of August 27, 2025, and a per shareprice of $2.82, the closing sale price of our common stock on July 11, 2025 (a date within 60 days of the date hereof). Pursuant toGeneral Instruction I.B.6 of Form S-3, in no event will we sell the securities described in this prospectus in a primary public offeringwith a value exceeding more than one-third of the aggregate market value of our common stock held by non-affiliates in the twelve-month period prior to the date of the sale of any such securities, so long as the aggregate market value of our outstanding commonstock held by non-affiliates remains below $75.0 million. Investing in our securities involves a high degree of risks, including the risk of losing your entire investment. See “RiskFactors” beginning on page S-6 to read about factors you should consider before buying our securities. Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of thesesecurities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense. We anticipate that delivery of the shares of common stock offered hereby against payment on or about September 10, 2025. Maxim Group LLC The date of this prospectus supplement is September 9, 2025. TABLE OF CONTENTS PageABOUT THIS PROSPECTUSS-iiCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSS-iiiPROSPECTUSSUMMARYS-1RISK FACTORSS-6USE OF PROCEEDSS-8CAPITALIZATIONS-10DILUTIONS-11DESCRIPTION OF SECURITIES THAT WE ARE OFFERINGS-12PLAN OF DISTRIBUTIONS-13LEGAL MATTERSS-16EXPERTSS-16WHERE YOU CAN FIND ADDITIONAL INFORMATIONS-16INCORPORATION BY REFERENCES-17 TABLE OF CONTENTS PageABOUT THIS PROSPECTUSiiCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSiiiTHE COMPANY1RISK FACTORS3USE OF PROCEEDS4PLANOF DISTRIBUTION5DESCRIPTIONOF OUR CAPITAL STOCK7DESCRIPTION OF WARRANTS11DESCRIPTION OF DEBT SECURITIES12DESCRIPTION OF THE UNITS14DESCRIPTIONOF THE RIGHTS15LEGAL MATTERS17EXPERTS17WHERE YOU CAN FIND ADDITIONAL INFORMATION17INCORPORATION BY REFERENCE18 ABOUT THIS PROSPECTUS SUPPLEMENT On September 2, 2025, we filed a registration statement on Form S-3 (File No. 333-289979) with the United States Securitiesand Exchange Commission (the “SEC”) using a shelf registration p