X0202 SCHEDULE 13D/A 0001506251 XXXXXXXX LIVE 4 Common Shares, $0.0001 par value per share 05/15/2026 false 0001851484 17331Y109 Citius Oncology, Inc.

11 Commerce Drive 1st Floor Cranford NJ 07016

Leonard L. Mazur (908) 967-6677 Chief Executive Officer 11 Commerce Drive, 1st Floor Cranford NJ 07016 Alexander M. Donaldson, Esq. (919) 781-4000 4101 Lake Boone Trail, Suite 300 Raleigh NC 27607 Lorna A. Knick, Esq. (919) 781-4000 4101 Lake Boone Trail, Suite 300 Raleigh NC 27607 Wyrick Robbins Yates & Ponton (919) 781-4000 4101 Lake Boone Trail, Suite 300 Raleigh NC 27607 0001506251 N Citius Pharmaceuticals, Inc. OO N X1 66049615.00 0.00 66049615.00 0.00 66049615.00 N 71.0 CO CO Common Shares, $0.0001 par value per share Citius Oncology, Inc. 11 Commerce Drive 1st Floor Cranford NJ 07016 EXPLANATORY NOTE This Amendment No. 4 to the Schedule 13D of the Reporting Person filed on August 16, 2024, as amended on July 25, 2025, September 12, 2025, and December 17, 2025 (this "Amendment"), amends and supplements the Schedule 13D as specifically set forth herein, to report a material decrease in the Reporting Person's percentage beneficial ownership of the Issuer's common stock resulting solely from increases in the Issuer's outstanding shares. The information provided herein is intended to encompass the information that would have been included in amendments previously required upon the occurrence of the events summarized below. The Reporting Person is the beneficial owner of 66,049,615 shares of the Issuer's common stock, which represents approximately 71.0% of the Issuer's outstanding common stock, based upon 92,981,204 shares of common stock outstanding as of May 14, 2026 (per the Issuer's Form 10-Q for the quarter ended March 31, 2026, filed May 15, 2026). The decrease in the Reporting Person's percentage beneficial ownership since Amendment No. 3 resulted solely from increases in the Issuer's outstanding shares of common stock and not from any acquisition or disposition of shares by the Reporting Person. Additional Event Requiring Amendment On February 10, 2026, the Issuer reported that 88,275,204 shares of common stock were outstanding (as of such date), as disclosed in its Quarterly Report on Form 10-Q for the quarter ended December 31, 2025. Based on 66,049,615 shares beneficially owned by the Reporting Person, this reflected a decrease in the Reporting Person's percentage beneficial ownership to approximately 74.9%. The Reporting Person has sole voting and dispositive power of 66,049,615 shares of the Issuer's common stock beneficially owned. Note: In its Current Report on Form 8-K filed on May 6, 2026 (the "Form 8-K"), the Issuer disclosed the immediate exercise of warrants for 12,777,778 shares and the issuance of replacement warrants. According to the Form 8-K, such shares are being held in abeyance by the transfer agent due to a 9.99% beneficial ownership limitation and therefore are not included in the outstanding share count used above. Citius Pharmaceuticals, Inc. /s/ Leonard Mazur 06/04/2026