Aldesleukin

Summary

Aldesleukin is a recombinant form of interleukin‑2 (IL‑2) that stimulates proliferation and activation of immune cells. It is administered by injection (intravenous or subcutaneous) and is approved for clinical use as a cytokine therapy. Research explores its ability to expand regulatory T cells at low doses for cardiovascular inflammation, to boost anti‑tumour activity in renal cell carcinoma and in adoptive cell therapies for glioblastoma and colorectal cancer, and to modulate autoimmune myositis.

Mechanism of Action

Aldesleukin binds the high‑affinity IL‑2 receptor (CD25/CD122/CD132) on lymphocytes, triggering JAK1/3‑STAT5 signalling that drives proliferation of CD8+ cytotoxic T cells, NK cells, and especially CD4+CD25+ regulatory T cells (Tregs). At low concentrations, the high‑affinity receptor on Tregs is preferentially engaged, leading to selective Treg expansion, whereas higher doses activate broader effector populations, enhancing cytotoxic activity against tumours but also increasing cytokine‑mediated toxicity.

What the Research Shows

A phase 1b/2a dose‑escalation trial in patients with stable or acute ischemic heart disease showed subcutaneous low‑dose aldesleukin (0.3–3.0 ×10⁶ IU daily) increased circulating Tregs in a dose‑dependent manner with mostly mild adverse events. In a first‑in‑human glioblastoma study, intracranial administration of allogeneic CAR‑T cells combined with 2500–5000 IU aldesleukin infusions was well tolerated and yielded transient tumour necrosis in four of six patients. A 2004 review of metastatic renal cell carcinoma reported numerous trials of aldesleukin, noting clinical activity but unresolved dose‑response relationships. A 2024 rheumatology review highlighted phase II trials of aldesleukin in idiopathic inflammatory myopathies, reporting improvements in clinical and laboratory measures. Finally, a 2025 phase I trial of CRISPR‑edited TILs for metastatic colorectal cancer used high‑dose intravenous aldesleukin (720 000 IU/kg) as part of lymphodepletion; all patients experienced severe haematologic toxicities, yet half achieved stable disease and one patient attained a durable complete response.

Reported Benefits

Low‑dose aldesleukin can selectively expand Tregs, offering a potential anti‑inflammatory strategy for ischemic heart disease. High‑dose regimens enhance cytotoxic lymphocyte activity, contributing to tumour regression in renal cell carcinoma and in adoptive cell therapy settings for glioblastoma and colorectal cancer. Early-phase myositis trials suggest possible clinical and laboratory improvements, indicating broader immunomodulatory utility.

Limitations of the Evidence

Evidence is limited to small, early‑phase studies; sample sizes are modest and follow‑up short. Optimal dosing remains unclear, with conflicting data on efficacy versus toxicity. The cardiovascular trial was exploratory and requires larger confirmatory studies. In oncology, benefits have been observed primarily in combination with cellular therapies, making it difficult to isolate aldesleukin’s contribution. Safety concerns increase markedly at high doses, restricting broader use.

Safety Considerations

Low‑dose subcutaneous aldesleukin was associated with mainly mild adverse events and two serious events unrelated to the drug. High‑dose intravenous administration, as used in TIL therapy, produced universal grade 3–4 haematologic toxicities, fatigue, and anorexia, reflecting the known capillary‑leak syndrome of IL‑2. Intracranial delivery in the glioblastoma study was well tolerated with no severe cytokine‑release events. Overall, safety is dose‑dependent, with higher doses requiring intensive monitoring.

How It Is Administered

Aldesleukin is supplied as a sterile recombinant protein for injection. It can be given subcutaneously (e.g., daily low‑dose regimens) or intravenously (e.g., high‑dose bolus in adoptive cell therapy). In some trials it has been delivered directly into the brain parenchyma alongside CAR‑T cells. Formulations are typically supplied in IU units and reconstituted in sterile diluent before administration.

Routes of Administration

Goals & Uses

• Metastatic melanomaOncologyHigh
• Metastatic renal cell carcinoma treatmentOncologyHigh
• Immune reconstitution in HIVInfectious DiseaseModerate
• Combination immunotherapy potentiationOncologyModerate
• Metastatic melanoma treatmentOncologyHigh
• Regulatory T-cell expansion (low-dose)Autoimmunity / ResearchLow
• Adjuvant immunotherapy for solid tumoursOncologyModerate
• Metastatic renal cell carcinomaOncologyHigh

Contraindications

• Severe cardiovascular disease (unstable angina, recent MI)CardiovascularModerate
• Organ allografts requiring immunosuppressionTransplantationHigh
• Hypersensitivity to aldesleukin or any excipientAllergyHigh
• Organ transplant recipientsImmunologyHigh
• Known hypersensitivity to aldesleukin or any componentAllergyHigh
• Prior severe toxicity on previous IL-2 coursePrior Treatment HistoryHigh
• Serious infections or sepsisInfectious DiseaseHigh
• Active autoimmune diseaseAutoimmunityHigh
• Abnormal thallium stress test or pulmonary function testsCardiovascular/PulmonaryHigh

Adverse Effects

• Oliguria / renal impairmentRenalCommon
• Capillary leak syndromeVascularCommonLeakage of fluid from blood vessels into tissues
• HypotensionCardiovascularCommonLow blood pressure
• Nausea/vomitingGastrointestinalCommon
• Fever and chillsConstitutionalCommon
• Neuropsychiatric effects (confusion, somnolence)NeurologicalCommon
• Pulmonary edemaRespiratoryUncommon
• Rash or pruritusDermatologicCommon
• Thrombocytopenia and anemiaHematologicCommon

Drug Interactions

• Nephrotoxic agents (e.g., aminoglycosides, NSAIDs)High
• CorticosteroidsModerate
• Cardiotoxic agents (e.g., doxorubicin)High
• Other cytokine therapies (e.g., interferon‑α)Moderate
• ACE inhibitorsLow
• AntihypertensivesHighMay potentiate hypotensive effects in some contexts
• Interferon-alphaModerate

Population Constraints

• PregnancyReproductive SafetyAbsolute
• Patients with CNS metastasesDisease RelatedRelative
• Pediatric patientsAgeRelative
• Patients with hepatic impairmentOrgan FunctionRelative
• Elderly patients (≥65 years)Age RelatedRelative
• BreastfeedingReproductiveAbsolute
• Pediatric useAgeRelative

Regulatory Status

• European UnionApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaEMA approval; similar monitoring requirements.
• United StatesApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaFDA‑approved; administered under a Risk Evaluation and Mitigation Strategy (REMS).
• United KingdomApprovedApproved: metastatic renal cell carcinoma, metastatic melanomaMHRA approved; used in specialist oncology centres.

Approved by FDA (2006) for metastatic RCC and melanoma; also holds EMA approval. Administered under strict monitoring due to risk of capillary leak syndrome.

Evidence & Sources

• Regulatory T-Cell Response to Low-Dose Interleukin-2 in Ischemic Heart Disease
  Journal ArticleModerateZhao TX, et al.2022-01-01T00:00:00.000000Z
• Off-the-shelf, steroid-resistant, IL13Rα2-specific CAR T cells for treatment of glioblastoma
  Journal ArticleModerateBrown CE, et al.2022-01-01T00:00:00.000000Z
• Aldesleukin in advanced renal cell carcinoma
  Journal ArticleModerateSchmidinger M, Hejna M, Zielinski CC2004-01-01T00:00:00.000000Z
• Where are we now in biologic drugs for myositis?
  Journal ArticleModerateNeves A, et al.2024-01-01T00:00:00.000000Z
• Targeting the intracellular immune checkpoint CISH with CRISPR-Cas9-edited T cells in patients with metastatic colorectal cancer: a first-in-human, single-centre, phase 1 trial
  Journal ArticleModerateLou E, et al.2025-01-01T00:00:00.000000Z

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