# Denileukin diftitox

Source: https://onco.cc/drugs/denileukin-diftitox/  
OnCo record `denileukin-diftitox` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Denileukin diftitox (Lymphir) is an infusion that uses the interleukin-2 signal as a homing device to deliver a bacterial toxin into cutaneous T-cell lymphoma cells. It was withdrawn in 2014 and returned in an improved form in 2024.

## Summary

The original denileukin diftitox (Ontak) was approved in 1999 for persistent or recurrent CD25-positive cutaneous T-cell lymphoma and withdrawn from the US market in 2014 because of manufacturing problems. A reformulated, higher-purity product was approved by the FDA in August 2024 as Lymphir for adults with relapsed or refractory stage I to III CTCL after at least one systemic therapy, on Study 302, an open-label single-arm trial in which 36% of patients responded (with CD25 expression on at least 20% of malignant cells required for entry). Capillary leak syndrome, infusion reactions and visual changes carry boxed warnings and require premedication and close monitoring.

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-10
- Also known as: Ontak (1999 to 2014); E7777
- Tags: nci-list
- Brand: Lymphir
- Modality: IL-2 receptor-directed cytotoxin (fusion protein)
- Mechanism: Fusion of interleukin-2 with diphtheria toxin fragments A and B; binds CD25-expressing cells, is internalised, and the toxin blocks protein synthesis and kills the cell.
- Approvals: US 1999: Persistent or recurrent CD25-positive CTCL (Ontak; withdrawn 2014); US 2024: Relapsed or refractory stage I to III CTCL after at least one systemic therapy (Lymphir)

## Notes

- Cutaneous T-cell lymphoma has no cancer record yet.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Denileukin_diftitox
- US label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=denileukin%20diftitox
- NCI drug page: https://www.cancer.gov/about-cancer/treatment/drugs/denileukindiftitox-cxdl

## Connected records

- targets: [CD25 (IL-2 receptor alpha)](https://onco.cc/targets/cd25/)
- companies: [Citius Pharmaceuticals](https://onco.cc/companies/citius-pharmaceuticals/), [Eisai](https://onco.cc/companies/eisai/)
- trials: [A Trial of Intravenous Denileukin Diftitox in Stage III or IV Ovarian Cancer](https://onco.cc/trials/nct00880360/), [Phase II Trial of Ontak With Metastatic Melanoma](https://onco.cc/trials/nct00299689/), [Study of Denileukin Diftitox in Participants With Stage IIIC and Stage IV Melanoma](https://onco.cc/trials/nct01127451/)
- cancers: [Mycosis fungoides](https://onco.cc/cancers/mycosis-fungoides/)

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