Citius Oncology Highlights Phase 1 Data in an Investigator-Initiated Study of LYMPHIR (denileukin diftitox-cxdl) in Combination with Pembrolizumab in Recurrent or Refractory Gynecologic Malignancies Investigator-initiate

Oncology Highlights Phase 1 Data in an Investigator-Initiated Study of LYMPHIR

(denileukin diftitox-cxdl) in Combination

with Pembrolizumab in Recurrent or Refractory Gynecologic Malignancies

Investigator-initiated

study data presented May 30, 2026, at the American Society of

Oncology (ASCO) Annual Meeting demonstrated durable responses and manageable tolerability in heavily pre-treated

months of median progression-free survival observed among 48% of efficacy-evaluable patients achieving clinical benefit (10 of 21)

were observed in patients previously treated with immune checkpoint inhibitors,

including a 33% objective response rate in patients with

relapsed or refractory endometrial cancer

N.J., June 1, 2026 - Citius Oncology, Inc. ("Citius Oncology") (Nasdaq: CTOR), an oncology-focused

biopharmaceutical company and majority-owned subsidiary of Citius Pharmaceuticals, Inc. ("Citius Pharma") (Nasdaq:

CTXR), today highlighted Phase 1 clinical data presented May 30, 2026, at the American Society of Clinical Oncology (ASCO) Annual

Meeting evaluating LYMPHIR (denileukin diftitox-cxdl) in combination with pembrolizumab in patients with recurrent or refractory

gynecologic malignancies. The poster presentation (Abstract #2564) was presented by investigators from the University of Pittsburgh

Medical Center (UPMC) Magee-Womens Hospital.

ability to transiently deplete immunosuppressive regulatory T-cells may help address immune resistance in the tumor microenvironment

and enhance the effect of checkpoint inhibitors. The encouraging clinical signals and tolerability profile observed in this study support

continued clinical evaluation of this "chemo-free" immunomodulatory approach, especially in tumors where resistance to checkpoint

inhibitors remains a significant challenge," said Dr. Myron S. Czuczman, Chief Medical Officer of Citius Oncology.

open-label Phase 1 study evaluated LYMPHIR in combination with pembrolizumab in 25 heavily pre-treated patients (21 evaluable for efficacy)

with recurrent or metastatic solid tumors, primarily gynecologic malignancies. Enrolled patients had received a median of five prior

therapies, and more than half had previously received anti-PD-1 or PD-L1 therapy.

Efficacy and Safety findings presented at ASCO included:

Alexander Olawaiye, a professor and one of the gynecologic cancer researchers at UPMC Magee-Womens Hospital and lead investigator of

the study, added, "Patients with recurrent gynecologic malignancies who progress following immunotherapy often have limited treatment

options. The clinical activity observed with denileukin diftitox-cxdl plus pembrolizumab, including durable responses and prolonged disease

control in heavily pre-treated patients, is notable. Given the lack of effective salvage treatments for these patients, especially those

that have failed prior immune-checkpoint inhibition, the novel combination of LYMPHIR plus pembrolizumab provides a potential viable

therapeutic option. Importantly, the safety profile observed was manageable in this heavily pre-treated population, supporting continued

evaluation in larger studies."

translational studies are evaluating the impact of the combination on regulatory T-cells, immune effector cells, and the tumor microenvironment

to help identify potential biomarkers in order to optimize future development strategies. A Phase 2 expansion study is being planned

to further evaluate the combination in gynecologic cancers, including less heavily pre-treated and prior immunotherapy-exposed patient

open-label, dose-escalation, investigator-initiated Phase 1 study (NCT05200559), led by Dr. Alexander B Olawaiye at UPMC Magee-Womens

Hospital, enrolled 25 patients with recurrent or metastatic solid tumors who had received at least one prior line of therapy. LYMPHIR

was administered intravenously on Days 1-3 of each 21-day cycle at escalating doses (3, 6, 9, and 12 mcg/kg), along with

pembrolizumab (200 mg IV) on Day 1. Patients who completed eight cycles of combination therapy were continued on pembrolizumab

monotherapy until disease progression. Citius Oncology provided study drug and financial support to the investigator-initiated study;

the study was designed, conducted, and analyzed by the UPMC investigators.

note on investigational use: The use of LYMPHIR in this study was investigational and outside of its FDA-approved indication of relapsed

or refractory Stage I-III cutaneous T-cell lymphoma. LYMPHIR is not approved by the FDA for the treatment of gynecologic malignancies

or any solid tumor, and the safety and efficacy of LYMPHIR in this setting have not been established. This Phase 1 study was not designed

or powered to evaluate clinical efficacy, and no conclusions can be drawn regarding comparative effectiveness or long-term outcomes.

Early-stage clinical data may not be predictive of results from larger or later-stage studies.

or metastatic ovarian and endometrial cancers are two of the most common gynecologic malignancies in the United States. Endometrial cancer

is the most frequently diagnosed gynecologic cancer, with an estimated 70,000 new endometrial cancer cases expected in the United States

in 20261, while ovarian cancer remains the deadliest with approximately 12,700 deaths per year (51.6%) and approximately 20,000

new diagnoses each year in the United States2. These cancers are often detected at advanced stages, and although many patients

initially respond to platinum-based chemotherapy, most experience relapse and develop resistance. Survival rates in the recurrent setting

remain poor, and responses to current immunotherapies such as PD-1 inhibitors are limited, highlighting a significant unmet need for

novel treatment approaches. LYMPHIR's transient depletion of regulatory T-cells in combination with anti-PD-1 checkpoint inhibition

may potentially enhance host anti-tumor immune responses and help overcome immunotherapy resistance in these difficult-to-treat tumors.

LYMPHIR (denileukin diftitox-cxdl)

is a targeted immune therapy for relapsed or refractory cutaneous T-cell lymphoma (CTCL) indicated for use in Stage I-III disease after

at least one prior systemic therapy. It is a recombinant fusion protein that combines the IL-2 receptor binding domain with diphtheria

toxin (DT) fragments. The agent specifically binds to IL-2 receptors on the cell surface, causing diphtheria toxin fragments that have

entered cells to inhibit protein synthesis. After uptake into the cell, the DT fragment is cleaved and the free DT fragments inhibit

protein synthesis, resulting in cell death. Denileukin diftitox-cxdl-associated anti-tumor activity is achieved via a direct cytocidal

action on IL-2R-expressing tumors and depletion of host immunosuppressive regulatory T lymphocytes (Tregs).

2021, reformulated denileukin diftitox received regulatory approval in Japan for the treatment of relapsed or refractory CTCL and peripheral

T-cell lymphoma (PTCL). Subsequently, in 2021, Citius acquired an exclusive license with rights to develop and commercialize reformulated

denileukin diftitox in all markets except for India, Japan and certain parts of Asia. LYMPHIR (denileukin diftitox-cxdl) was approved

by the FDA and subsequently launched in the U.S. in December 2025.

Citius Oncology, Inc.

Oncology, Inc. (Nasdaq: CTOR) is a platform to develop and commercialize novel targeted oncology therapies. In December 2025, Citius

Oncology launched LYMPHIR, approved by the FDA for the treatment of adults with relapsed or refractory Stage I-III CTCL who had

had at least one prior systemic therapy. Management estimates the initial CTCL market for LYMPHIR currently exceeds $400 million, is

growing, and is underserved by existing therapies. Robust intellectual property protections that span orphan drug designation, complex

technology, trade secrets and pending patents for immuno-oncology use as a combination therapy with checkpoint inhibitors would further

support Citius Oncology's competitive positioning. For more information, please visit www.citiusonc.com.

press release may contain "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933 and

Section 21E of the Securities Exchange Act of 1934. Such statements are made based on our expectations and beliefs concerning future

events impacting Citius Oncology. You can identify these statements by the fact that they use words such as "will," "anticipate,"

"estimate," "expect," "plan," "should," and "may" and other words and terms

of similar meaning or use of future dates. Forward-looking statements are based on management's current expectations and are subject

to risks and uncertainties that could negatively affect our business, operating results, financial condition and stock price. Factors

that could cause actual results to differ materially from those currently anticipated are: our need for substantial additional funds

and our ability to raise additional money to fund our operations for at least the next 12 months as a going concern; our ability to successfully

commercialize LYMPHIR and establish a sustainable revenue stream; our ability to regain compliance with Nasdaq's continued listing

standards; our ability to obtain, perform under and maintain third party agreements and relationships, including obtaining a new bulk

drug substance supplier; risks relating to the results of research and development activities, including those from our existing and

any new pipeline assets; early-stage clinical data may not be predictive of results from larger or later-stage studies; our ability to

secure and maintain strategic partnerships and expand international access to LYMPHIR; the estimated markets for LYMPHIR and our product

candidates and the acceptance thereof by any market; our ability to use the latest technology to support our commercialization efforts

for LYMPHIR; physician and patient acceptance of LYMPHIR in a competitive treatment landscape; our reliance on third-party logistics

providers, distributors, and specialty pharmacies to support commercial operations; our ability to educate providers and payers, secure

adequate reimbursement, and maintain uninterrupted product supply; post-marketing requirements and ongoing regulatory compliance related

to LYMPHIR; the ability of LYMPHIR and our product candidates to impact the quality of life of our target patient populations; our ability

to procure cGMP commercial-scale supply; risks related to our growth strategy; patent and intellectual property matters; government regulation;

as well as other risks described in our Securities and Exchange Commission ("SEC") filings. These risks have been and may

be further impacted by any future public health risks. Accordingly, these forward-looking statements do not constitute guarantees of

future performance, and you are cautioned not to place undue reliance on these forward-looking statements. Risks regarding our business

are described in detail in our SEC filings which are available on the SEC's website at www.sec.gov, including in Citius Oncology's

Annual Report on Form 10-K for the year ended September 30, 2025, filed with the SEC on December 23, 2025. These forward-looking statements

speak only as of the date hereof, and we expressly disclaim any obligation or undertaking to release publicly any updates or revisions

to any forward-looking statements contained herein to reflect any change in our expectations or any changes in events, conditions or

circumstances on which any such statement is based, except as required by law.

(denileukin diftitox-cxdl)

is an IL2-receptor-directed cytotoxin indicated for the treatment of adult patients with r/r Stage I-III cutaneous T-cell lymphoma (CTCL)