CITIUS ONCOLOGY, INC.

As filed with the Securities and Exchange Commission on July 14, 2025

Registration Statement No. 333-_______

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-1

REGISTRATION STATEMENT UNDER

THE SECURITIES ACT OF 1933

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation or organization)

8731

(Primary Standard Industrial Classification Code Number)

99-4362660

(I.R.S. Employer

Identification Number)

11 Commerce Drive, First Floor

Cranford, New Jersey 07016

Telephone: (908) 967-6677

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Leonard Mazur

Chief Executive Officer

11 Commerce Drive, First Floor

Cranford, New Jersey 07016

Telephone: (908) 967-6677

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this registration statement.

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 check the following box:☒

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.☐

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.☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) 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.☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.☐

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 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the U.S. Securities and Exchange Commission is effective. The preliminary prospectus is not an offer to sell these securities and does not constitute the solicitation of offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED JULY 14, 2025

PRELIMINARY PROSPECTUS

Citius Oncology, Inc.

Up to $15 million of Shares of Common Stock

Up to $15 million of Pre-Funded Warrants to Purchase up to $15 million of Shares of Common Stock

Up to $15 million of Warrants to Purchase $15 million of Shares of Common Stock

Up to $15 million of Shares of Common Stock underlying the Warrants and Pre-Funded Warrants

Up to $750,000 of Shares of Common Stock Underlying the Placement Agent’s Warrants

We are offering up to $15 million of shares of common stock, par value $0.0001 per share (the “Common Stock”), and accompanying warrants to purchase up to $15 million of shares of Common Stock (the “Warrants”), at an assumed combined offering price of $[] per share of Common Stock and accompanying Warrant (assuming a public offering price equal to the closing price of our Common Stock of $[] per share as reported by the Nasdaq Capital Market (“Nasdaq”) on July [__], 2025).

Each Warrant will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Warrants (the “Warrant Stockholder Approval”), provided however, if the Pricing Conditions (as defined below) are met, the Warrant Stockholder Approval will not be required and the Warrants will be exercisable upon issuance (the “Initial Exercise Date”). The Warrants will expire five years from the Initial Exercise

The shares of Common Stock and Warrants will be issued separately and will be immediately separable upon issuance but will be purchased together in this offering. This prospectus also relates to the shares of common stock issuable upon exercise of the common warrants sold in this offering. As used herein “Pricing Conditions” means that the combined public offering price per share and accompanying common warrant is such that the Warrant Stockholder Approval is not required under the rules of The Nasdaq Stock Market LLC (“Nasdaq”) because either (i) the offering is an at-the-market offering under the rules of Nasdaq (the “Nasdaq Rules”) and such price equals or exceeds the sum of (a) the applicable “Minimum Price” per share under Nasdaq Rule 5635(d) plus (b) $0.125 per whole share of common stock underlying the common warrants or (ii) the offering is a discounted offering where the pricing and discount (including attributing a value of $0.125 per whole share underlying the common warrants) meet the pricing requirements under the Nasdaq Rules.

We are also offering to those purchasers, if any, whose purchase of the Common Stock in this offering would result in the purchaser, together with its affiliates and certain related parties, beneficially owning more than 4.99% (or at the election of the purchaser, 9.99%) of our outstanding Common Stock immediately following the consummation of this offering, the opportunity to purchase, if they so choose, pre-funded warrants in lieu of the Common Stock that would otherwise result in ownership in excess of 4.99% (or 9.99%, as applicable) of our outstanding Common Stock (the “Pre-Funded Warrants”). The purchase price for each Pre-Funded Warrant will equal the per share public offering price for the Common Stock in this offering less the $0.0001 per share exercise price of each such Pre-Funded Warrant. Each Pre-Funded Warrant will be exercisable upon issuance and will not expire prior to exercise. For each Pre-Funded Warrant we sell, the number of shares of Common Stock we are offering will be decreased on a one-for-one basis. This prospectus also relates to the shares of Common Stock that are issuable from time to time upon exercise of the Pre-Funded Warrants.

Our Common Stock is traded on Nasdaq under the symbol “CTOR”. There is no established trading market for the Warrants and Pre-Funded Warrants being sold in this offering and we do not expect a market to develop. In addition, we do not intend to list the Warrants and Pre-Funded Warrants on Nasdaq or any other nationally recognized trading system. Without an active trading market, the liquidity of the Warrants and Pre-Funded Warrants will be limited.

The public offering price for our securities in this offering will be determined at the time of pricing, and may be at a discount to the then-current market price. The assumed combined public offering price used throughout this prospectus may not be indicative of the final offering price. The final public offering price will be determined through negotiation between us and investors based upon a number of factors, including our history and our prospects, the industry in which we operate, our past and present operating results, the previous experience of our executive officers and the general condition of the securities markets at the time of this offering.

We have engaged Maxim Group LLC as our exclusive placement agent (“Maxim” or the “placement agent”) to use its reasonable best efforts to solicit offers to purchase our securities in this offering. The placement agent has no obligation to purchase any of the securities from us or to arrange for the purchase or sale of any specific number or dollar amount of the securities. Because there is no minimum offering amount required as a condition to closing in this offering the actual public offering amount, placement agent’s fee, and proceeds to us, if any, are not presently determinable and may be substantially less than the total maximum offering amounts set forth above and throughout this prospectus. We have agreed to pay the placement agent the placement agent fees set forth in the table below. See “Plan of Distribution” in this prospectus for more information.

Investing in our securities involves a high degree of risks, including the risk of losing your entire investment. See “Risk Factors” beginning on page 8 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 these securities 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 (or Pre-Funded Warrants in lieu thereof) and Warrants offered hereby against payment on or about , 2025.

Maxim Group LLC

The date of this prospectus is , 2025.

TABLE OF CONTENTS

You should rely only on the information contained in this prospectus. No one has been authorized to provide you with information that is different from that contained in this prospectus. This prospectus is dated as of the date set forth on the cover hereof. You should not assume that the information contained in this prospectus is accurate as of any date other than that date.

We and the placement agent are offering to sell, and seeking offers to buy, our securities only in jurisdictions where offers and sales are permitted. Neither we nor the placement agent have done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside of the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of our securities and the distribution of this prospectus outside of the United States.

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