Human interleukin-2
Also known as: Aldesleukin, IL-2, Proleukin, recombinant human IL-2, T-cell growth factor, TCGF
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Summary
Human interleukin‑2 (IL‑2) is a cytokine that promotes the growth and activation of T‑lymphocytes and natural‑killer cells. It is formulated as a prescription drug, approved in the United States, and delivered by intravenous or subcutaneous injection. Commercially, IL‑2 is incorporated into the fusion protein denileukin diftitox, which is used for relapsed or refractory cutaneous T‑cell lymphoma (CTCL).
Mechanism of Action
IL‑2 binds the heterotrimeric IL‑2 receptor composed of α (CD25), β (CD122) and γ (CD132) chains. Receptor engagement activates the JAK1/3‑STAT5 pathway, leading to transcription of genes that drive proliferation, survival, and cytotoxic function of activated CD4⁺ and CD8⁺ T cells and NK cells. In denileukin diftitox, the IL‑2 moiety directs the diphtheria‑toxin payload to cells expressing high‑affinity IL‑2 receptors, delivering a cytotoxic effect while simultaneously stimulating immune effector cells.
What the Research Shows
A phase III, open‑label, multicenter trial evaluated denileukin diftitox‑cxdl, an improved‑purity IL‑2‑diphtheria toxin fusion, in 69 patients with relapsed/refractory CTCL who had received at least one prior systemic therapy. Patients received 9 µg/kg/day intravenously for five consecutive days every 21 days, up to eight cycles. The primary endpoint, objective response rate (ORR) by Global Response Score, was 36.2% (95% CI 25.0‑48.7), including 8.7% complete responses. Median duration of response was 8.9 months, and 84.4% experienced a reduction in skin tumor burden, with nearly half showing ≥50% decrease. Safety outcomes were consistent with known IL‑2‑related toxicities.
Reported Benefits
The trial demonstrated that denileukin diftitox‑cxdl can induce clinically meaningful tumor regression in a substantial proportion of heavily pre‑treated CTCL patients, with a median response lasting close to nine months. Reduction in skin tumor burden was observed in most participants, suggesting a disease‑modifying effect. The IL‑2 component also contributes to immune activation, which may support antitumor activity beyond the direct cytotoxic effect of the toxin.
Limitations of the Evidence
Evidence derives from a single‑arm, open‑label study without a comparator, limiting conclusions about relative efficacy. The overall response rate, while notable, remains modest, and complete responses were infrequent. The patient cohort was limited to CTCL, so findings cannot be extrapolated to other malignancies. Long‑term survival data and quality‑of‑life outcomes were not reported in the abstract.
Safety Considerations
Treatment‑emergent adverse events were common. Infusion reactions (74%) and hypersensitivity (68%) were the most frequent, usually grade 1‑2. Hepatotoxicity occurred in 36% of patients, and capillary leak syndrome was reported in 20% (grade ≥3 in 5.8%). Nausea (44%) and fatigue (32%) were also noted. Monitoring of liver enzymes, fluid balance, and prompt management of infusion‑related reactions are recommended.
How It Is Administered
Denileukin diftitox‑cxdl is administered intravenously as a daily infusion for five consecutive days, repeated every 21 days for up to eight cycles. The approved formulation of IL‑2 itself can be given either intravenously or subcutaneously, depending on the clinical indication and product label.
Routes of Administration
Goals & Uses
- Metastatic melanomaOncologyHigh
- Metastatic renal cell carcinoma treatmentOncologyHigh
- Immune reconstitution in HIVInfectious DiseaseModerate
- HIV infection adjunctInfectiousLow
- adoptive cell therapy supportImmunotherapyModerate
- Metastatic melanoma treatmentOncologyHigh
- Expansion of regulatory T cells (autoimmune diseases)ImmunologyModerate
- Metastatic renal cell carcinomaOncologyHigh
- Adoptive cell therapy adjunctOncology / ImmunotherapyModerate
Contraindications
- solid organ transplantTransplantHigh
- Active autoimmune disease requiring systemic treatmentImmunologyModerate
- Severe hepatic or renal impairmentOrgan ImpairmentModerate
- PregnancyPopulationModeratePotential fetal risk or insufficient safety data
- Severe cardiovascular diseaseCardiovascularHigh
- Active infection or sepsisInfectious DiseaseHigh
- Organ transplant recipients on immunosuppressionTransplantHigh
- Abnormal thallium stress test or pulmonary function testsCardiovascular/PulmonaryHigh
- autoimmune disease activityAutoimmuneModerate
Adverse Effects
- Injection site reactionsLocalCommon
- Capillary leak syndromeVascularRareLeakage of fluid from blood vessels into tissues
- HypotensionCardiovascularCommonLow blood pressure
- Nausea/vomitingGastrointestinalCommon
- Fever and chillsConstitutionalCommon
- Neuropsychiatric effects (confusion, somnolence)NeurologicalUncommon
- Renal impairment / oliguriaRenalCommon
- Fever, chills, rigorsConstitutionalCommon
- Elevated liver enzymesHepaticUncommonIncrease in AST/ALT or other hepatic markers
Drug Interactions
- Antihypertensive agentsModerate
- Beta‑blockersLow
- Nephrotoxic agents (e.g., aminoglycosides, NSAIDs)High
- CyclosporineHigh
- CorticosteroidsModerate
- Checkpoint inhibitors (e.g., nivolumab, ipilimumab)Moderate
Population Constraints
- Renal impairmentOrgan ImpairmentRelative
- Patients with CNS metastasesDisease RelatedRelative
- Pediatric patientsAgeRelative
- Elderly patients (>65 years)AgeRelative
- Pregnant womenReproductiveRelative
- Elderly (>65)AgeRelative
Regulatory Status
- European UnionApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaEMA centralized procedure
- United StatesApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaPrescribed under Risk Evaluation and Mitigation Strategy (REMS)
- United KingdomApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaMHRA approved
FDA approved (1992) as Proleukin; EMA approved for similar indications; used under restricted distribution due to toxicity.
Evidence & Sources
- Journal ArticleModerateFoss FM, et al.2025-01-01T00:00:00.000000Z
Frequently Asked Questions
What type of cancer is denileukin diftitox approved to treat?
Denileukin diftitox is approved for patients with relapsed or refractory cutaneous T‑cell lymphoma, including mycosis fungoides and Sézary syndrome, after at least one prior systemic therapy.
How does the IL‑2 component contribute to the drug’s action?
The IL‑2 moiety targets cells that express the high‑affinity IL‑2 receptor (CD25). This directs the attached diphtheria toxin to those malignant T‑cells, delivering a cytotoxic payload while also stimulating broader immune activation.
What are the most common side effects patients should expect?
Patients most often experience infusion‑related reactions and hypersensitivity, typically mild to moderate. Hepatotoxicity, capillary leak syndrome, nausea, and fatigue also occur and should be monitored throughout treatment.
Is the drug given as a single dose or multiple cycles?
The regimen involves daily intravenous infusions for five days, repeated every 21 days. Treatment can continue for up to eight cycles, depending on response and tolerability.
Can IL‑2 be used for conditions other than CTCL?
While the abstract focuses on denileukin diftitox for CTCL, IL‑2 itself is a cytokine used in other approved oncology indications, such as metastatic renal cell carcinoma and melanoma, but those uses are not detailed in this study.
What is Human interleukin-2?
Human interleukin‑2 (IL‑2) is a cytokine that promotes the growth and activation of T‑lymphocytes and natural‑killer cells. It is formulated as a prescription drug, approved in the United States, and delivered by intravenous or subcutaneous injection. Commercially, IL‑2 is incorporated into the fusion protein denileukin diftitox, which is used for relapsed or refractory cutaneous T‑cell lymphoma (CTCL).
What is Human interleukin-2 used for?
Human interleukin-2 is educationally associated with: Metastatic melanoma, Metastatic renal cell carcinoma treatment, Immune reconstitution in HIV, HIV infection adjunct, adoptive cell therapy support, Metastatic melanoma treatment, Expansion of regulatory T cells (autoimmune diseases), Metastatic renal cell carcinoma, Adoptive cell therapy adjunct. Educational only — not medical advice.
How is Human interleukin-2 administered?
Recorded routes of administration: Intravenous, Subcutaneous.
What are the potential side effects of Human interleukin-2?
Reported adverse effects include: Injection site reactions, Capillary leak syndrome, Hypotension, Nausea/vomiting, Fever and chills, Neuropsychiatric effects (confusion, somnolence), Renal impairment / oliguria, Fever, chills, rigors, Elevated liver enzymes. This list is not exhaustive — consult a qualified clinician.
Who should avoid Human interleukin-2?
Recorded contraindications: solid organ transplant, Active autoimmune disease requiring systemic treatment, Severe hepatic or renal impairment, Pregnancy, Severe cardiovascular disease, Active infection or sepsis, Organ transplant recipients on immunosuppression, Abnormal thallium stress test or pulmonary function tests, autoimmune disease activity. Consult a qualified clinician before use.