Citius Oncology is a single-product biopharmaceutical company focused on commercializing LYMPHIR (denileukin diftitox-cdxl), an FDA-approved therapy for cutaneous T-cell lymphoma (CTCL), a rare skin cancer affecting roughly 30,000–40,000 patients in the U.S. LYMPHIR is an engineered IL-2 diphtheria toxin fusion protein that binds to IL-2 receptors on cancer cells and delivers diphtheria toxin directly into the cell to cause cell death, while also depleting immunosuppressive regulatory T-cells to enhance the body's antitumor response. LYMPHIR is a reformulation of ONTAK, an older drug withdrawn in 2014 due to manufacturing issues; Citius Oncology acquired rights to the reformulated product, ran a Phase 3 trial, received FDA approval in August 2024, and launched commercially in December 2025. The company sells LYMPHIR in the U.S. through specialty distributors — Cardinal Health, Cencora, and McKesson — who supply hospitals and cancer centers, targeting a concentrated group of oncologists and dermatologist-oncologists. LYMPHIR is administered as a daily IV infusion over five consecutive days in 21-day cycles, generating recurring revenue per patient. Citius Oncology runs a lean, asset-light structure with no direct employees, relying entirely on contracted service providers and parent company Citius Pharma for management and commercial functions. The company carries a meaningful royalty and milestone burden owed to Dr. Reddy's and Eisai, which reduces per-dollar revenue economics. Beyond CTCL, Citius Oncology is exploring LYMPHIR in combination with checkpoint inhibitors and as a pretreatment for CAR-T therapy.